Filed Pursuant to Rule 424(b)(5)
Registration No. 333-227199

The information in this preliminary prospectus is not complete and may be changed. This preliminary prospectus is not an offer to sell these securities nor a solicitation of an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED SEPTEMBER 5, 2018

PRELIMINARY PROSPECTUS SUPPLEMENT

(TO PROSPECTUS DATED SEPTEMBER 5, 2018)

Infinera Corporation

$275,000,000

    % Convertible Senior Notes due 2024

Interest payable on March 1 and September 1

We are offering $275,000,000 principal amount of our     % Convertible Senior Notes due 2024 (the “notes”). The notes will bear interest at a rate of     % per year, payable semiannually in arrears on March 1 and September 1 of each year, beginning on March 1, 2019. The notes will mature on September 1, 2024, unless earlier repurchased, redeemed or converted.

Holders may convert their notes at their option at any time prior to the close of business on the business day immediately preceding June 1, 2024 only under the following circumstances: (1) during any fiscal quarter commencing after the fiscal quarter ending on December 29, 2018 (and only during such fiscal quarter), if the last reported sale price of the common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding fiscal quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price (as defined below) per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day; or (3) upon the occurrence of specified corporate events. On or after June 1, 2024, until the close of business on the second scheduled trading day immediately preceding the maturity date, holders of the notes may convert their notes at any time, regardless of the foregoing circumstances. Upon conversion, we will pay or deliver, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, as described in this prospectus supplement.

The conversion rate for the notes will initially be                  shares of common stock per $1,000 principal amount of notes (equivalent to an initial conversion price of approximately $        per share of common stock). The conversion rate for the notes will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events described in this prospectus supplement that occur prior to the maturity date of the notes or if we deliver a notice of redemption, in certain circumstances we will increase the conversion rate of the notes for a holder who elects to convert its notes in connection with such a corporate event or notice of redemption as the case may be.

Except as described in the immediately following sentence, we may not redeem the notes prior to September 5, 2021. If the Acquisition (as defined below) is not consummated for any reason by January 23, 2019, or if the Purchase Agreement (as defined herein) is terminated for any reason (other than by consummation of the Acquisition), we may redeem all, but not less than all, of the outstanding notes for cash on a redemption date to occur on or prior to April 23, 2019 for a redemption price for each $1,000 principal amount of notes equal to the sum of (i) $1,020, (ii) accrued and unpaid interest on such notes to, but excluding, the redemption date and (iii) 75% of the excess, if any, of the redemption conversion value (as defined herein) over the initial conversion value (as defined herein). We may redeem for cash all, but not less than all, of the notes, at our option, on or after September 5, 2021, if the last reported sale price of our common stock has been at least 130% of the conversion price for the notes then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending on, and including, the trading day immediately preceding the date on which we provide notice of redemption at a redemption price equal to 100% of the principal amount of the notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. No sinking fund is provided for the notes.

If we undergo a fundamental change prior to the maturity date of the notes, holders may require us to repurchase for cash all or any portion of their notes at a repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. The notes will be our senior unsecured obligations and will rank senior in right of payment to any of our indebtedness that is expressly subordinated in right of payment to the notes; equal in right of payment to any of our existing and future liabilities that are not so subordinated; effectively junior in right of payment to any of our secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness and other liabilities (including trade payables) of our current or future subsidiaries.

On July 23, 2018, we entered into a definitive unit purchase agreement (the “Purchase Agreement”) pursuant to which we will purchase all of the issued and outstanding limited liability company interests of Telecom Holding Parent LLC, a Delaware limited liability company (“Coriant,” and such purchase, the “Acquisition”). We intend to use a portion of the net proceeds from the offering of the notes, after paying the cost of the capped call transactions described herein, to fund the cash consideration and other amounts payable under the Purchase Agreement, including fees and expenses related thereto. We intend to use any remaining proceeds for general corporate purposes. This offering is not contingent on the consummation of the Acquisition.

Investing in the notes involves risks. See “Risk Factors” beginning on page S-15 of this prospectus supplement, as well as the documents we file with the Securities and Exchange Commission that are incorporated by reference herein for more information.

PRICE: 100%, PLUS ACCRUED INTEREST, IF ANY

We do not intend to apply to list the notes on any securities exchange or any automated dealer quotation system. Our common stock is listed on The Nasdaq Global Select Market under the symbol “INFN.” The last reported sale price of our common stock on The Nasdaq Global Select Market on September 4, 2018 was $8.69 per share.

If the underwriter sells more than the total principal amount of notes set forth above, the underwriter has an option, exercisable within a 30-day period, to purchase up to an additional $41,250,000 principal amount of notes solely to cover overallotments, if any.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

We expect that delivery of the notes will be made to investors in book-entry form through The Depository Trust Company on or about September     , 2018. The issue price will include accrued interest, if any, from September     , 2018 if settlement occurs after that date.

Sole Book-running Manager

MORGAN STANLEY

September     , 2018

TABLE OF CONTENTS

This prospectus supplement and the accompanying prospectus dated September 5, 2018 are part of a registration statement that we filed with the Securities and Exchange Commission (the “SEC”), using a “shelf” registration process. Under this shelf registration process, we may from time to time offer to sell debt securities in one or more offerings. We provide information to you about this offering of debt securities in two separate documents that are bound together: (1) this prospectus supplement, which describes the specific details regarding this offering; and (2) the accompanying prospectus, which provides general information, some of which may not apply to this offering. Generally, when we refer to this “prospectus,” we are referring to both documents combined. If information in this prospectus supplement is inconsistent with the accompanying prospectus, you should rely on this prospectus supplement. However, if any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in the accompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement as our business, financial condition, results of operations and prospects may have changed since the earlier dates. You should read this prospectus supplement, the accompanying prospectus, the documents and information incorporated by reference in this prospectus supplement and the accompanying prospectus, and any free writing prospectus that we have authorized for use in connection with this offering when making your investment decision. You should also read and consider the information in the documents we have referred you

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to under the heading “Where You Can Find More Information” and “Certain Documents Incorporated by Reference.”

Neither we nor the underwriter have authorized anyone to provide you with any information other than that contained or incorporated by reference in this prospectus supplement, the accompanying prospectus and any “free writing prospectus” prepared by or on behalf of us or to which we may have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. This prospectus supplement and the accompanying prospectus are not an offer to sell or a solicitation of an offer to buy securities in any jurisdiction where such offer to sale of securities would be unlawful. You should not assume that the information in this prospectus supplement and the accompanying prospectus, including any information incorporated by reference, is accurate as of any date other than their respective dates. If any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in this prospectus supplement—the statement in the document having the later date modifies or supersedes the earlier statement.

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RISK FACTORS

Investing in the notes and our common stock involves a high degree of risk. In addition, our business, operations and financial condition are subject to various risks. You should carefully consider the risks described below with all of the other information included in this prospectus supplement and the accompanying prospectus before making an investment decision. If any of the adverse events described below were to actually occur, our business, results of operations, or financial condition would likely suffer. In such an event, the trading price of the notes and our common stock could decline and you could lose all or part of your investment. Additionally, this section does not attempt to describe all risks applicable to our industry, our business or investment in the notes or our common stock. Risks not presently known to us or that we currently deem immaterial may also impair our business operations.

Risks Related to Our Proposed Acquisition of Coriant

We may fail to realize the anticipated strategic and financial benefits expected from our acquisition of Coriant.

We may not realize all of the anticipated benefits of the Acquisition or realize such benefits in the anticipated time frame after the completion of the Acquisition. Our ability to realize the anticipated strategic and financial benefits of the Acquisition will depend on, among other things, our ability to combine our business with Coriant’s business in a manner that facilitates growth, realizes anticipated cost savings and retains Coriant’s and our customers, suppliers and employees. We must successfully combine our business with the business of Coriant in a manner that enables these anticipated benefits to be realized and we must achieve the anticipated growth and cost savings without adversely affecting our revenue and financial results or the revenue and financial results of Coriant. We may not be able to achieve the cost reductions we have publicly announced prior to the Acquisition in the amount and time frame previously described, which may have a material adverse effect on our business, financial conditions and results of operations.

We may not be able to obtain our preferred form of financing to consummate the Acquisition, and the terms of the financing may be less favorable to us than expected.

There is no financing condition under the Purchase Agreement, which means that if the conditions to closing are otherwise satisfied or waived, we are obligated to consummate the Acquisition whether or not we have sufficient funds to pay the amounts required under the Purchase Agreement. In connection with the Purchase Agreement, we entered into a debt commitment letter pursuant to which an affiliate of the underwriter in this offering has committed to provide to us, among other things, $200 million of interim financing to fund the Acquisition, subject to the execution of definitive documentation and customary closing conditions, which will be reduced by the aggregate gross proceeds from the notes offered or from certain other forms of permanent financing. We currently intend to finance the cash portion of the Acquisition consideration and pay related fees and expenses in connection with the Acquisition using the net proceeds from the issuance of the notes offered hereby. Obligations of the lenders under the debt commitment letter are subject to a number of conditions, and we cannot provide any assurances that we will be able to close the financing provided by the debt commitment letter on the terms and in the amounts anticipated. If terms for the debt financing are less favorable than expected, or if we utilize such interim financing pursuant to the debt commitment letter, financing costs would likely increase, potentially significantly, and our financing or operating flexibility may be constrained. If we cannot close on any element of our financing plan, including the financing provided by the debt commitment letter, we will need to pursue other financing options, which will likely result in less favorable financing terms that would likely increase costs and/or materially adversely affect our financing and operating flexibility following the closing of the Acquisition.

We may be unable to realize the anticipated synergies related to the Acquisition, which could have a material adverse effect on our business, financial condition and results of operations.

Following the consummation of the Acquisition, we expect to realize significant synergies from cost savings after the closing of the Acquisition. We also expect to incur material one-time costs to achieve these synergies.

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While we believe these synergies are achievable, our ability to achieve such estimated synergies in the amounts and timeframe expected is subject to various assumptions by our management based on expectations that are subject to a number of risks, which may or may not be realized, as well as the incurrence of other costs in our operations that may offset all or a portion of such synergies and other factors outside our control. As a consequence, we may not be able to realize all of these synergies within the time frame expected or at all, or the amounts of such synergies could be significantly reduced. In addition, we may incur additional and/or unexpected costs to realize these synergies. Failure to achieve the expected synergies could significantly reduce the expected benefits associated with the Acquisition and adversely affect our business following the Acquisition. We have incurred and will continue to incur substantial expenses in connection with the negotiation and consummation of the transactions contemplated by the Purchase Agreement. These costs, as well as other unanticipated costs and expenses, could have a material adverse effect on our financial condition and operating results following the consummation of the Acquisition and many of these costs will be borne by us even if the Acquisition is not consummated.

Our gross margin will initially decline materially as a result of the Acquisition and we may not be able to increase them to the levels we expect to achieve.

We anticipate that our gross margin will initially decline as a result of the Acquisition. Our gross margin for the three months ended June 30, 2018 was 40.5%, which is significantly higher than the gross margin profile of the current Coriant business. As a result, we anticipate that, on a combined basis, our gross margin will be materially lower following consummation of the Acquisition. Any further declines in Coriant’s margin would continue to have a negative impact in our gross margin on a combined basis. While we intend to implement a number of strategies and measures to realize benefits and synergies that improve our gross margin following consummation of the Acquisition, there can be no assurance that such strategies and measures will be effective, that we will realize those anticipated benefits and synergies (including for the reasons described under “—We may be unable to realize the anticipated synergies relating to the Acquisition, which could have a material adverse effect on our business, financial condition and results of operations” above), or that they will have the effect of improving our gross margin, either within the anticipated time frame following the Acquisition or at all.

Following the consummation of the Acquisition, we may be unable to successfully integrate Coriant’s business and realize the anticipated benefits of the Acquisition.

We and Coriant currently operate as independent companies. After the closing of the Acquisition, we will be required to devote significant management attention and resources to integrating the business and operations of Coriant. Potential difficulties we may encounter in the integration process include the following:

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An inability to realize the anticipated benefits and cost synergies of the Acquisition, as well as any delays encountered in the integration process, could have a material adverse effect on the revenue, level of expenses and operating results of the combined company, which may materially adversely affect the value of our stock and the notes following the consummation of the Acquisition.

In addition, the actual integration may result in additional and unforeseen expenses, and the anticipated benefit of our plan for integration may not be realized. Actual synergies, if achieved at all, may be lower than what we expect and may take longer to achieve than anticipated. For example, the elimination of duplicative costs may not be possible or may take longer than anticipated, or the benefits from the Acquisition may be offset by costs incurred or delays in integrating the companies. If we are not able to adequately address these challenges, we may be unable to successfully integrate Coriant’s operations into our own or, even if we are able to combine the two business operations successfully, to realize the anticipated benefits of the integration of the two companies.

Our business relationships, those of Coriant or the combined company may be subject to disruption due to uncertainty associated with the Acquisition.

Parties with which we or Coriant do business may experience uncertainty associated with the pending Acquisition, including with respect to current or future business relationships with us, Coriant or the combined company. Our and Coriant’s business relationships may be subject to disruption, as customers, distributors, suppliers, vendors, and others may seek to receive confirmation that their existing business relations with us or Coriant, as the case may be, will not be adversely impacted as a result of the Acquisition or attempt to negotiate changes in existing business relationships or consider entering into business relationships with parties other than us, Coriant, or the combined company as a result of the Acquisition. For example, a number of Coriant’s customers deferred purchase orders with Coriant pending announcement of a strategic transaction, and there can be no assurance that all of those customers will ultimately submit such purchase orders with Coriant. Any such failure to submit such purchase orders with Coriant, or any of these other disruptions could have a material adverse effect on our or Coriant’s businesses, financial condition, or results of operations or on the business, financial condition or results of operations of the combined company, and could also have an adverse effect on our ability to realize the anticipated benefits of the Acquisition. The risks and adverse effects of such disruptions could be exacerbated by any delay in consummating the Acquisition, which could have a negative effect on our stock price and the value of your notes.

We do not currently control Coriant.

Although the Purchase Agreement contains covenants on the part of Coriant regarding the operation of its business prior to closing, we will not control Coriant and its subsidiaries until completion of the Acquisition and the business and results of operations of Coriant may be adversely affected by events that are outside of our control during the intervening period. The historic and current performance of Coriant’s business and operations may not be

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indicative of success in future periods. The future performance of Coriant may be influenced by, among other factors, economic downturns, turmoil in financial markets, unfavorable regulatory decisions, litigation, the occurrence or discovery of new liabilities, rising interest rates and other factors beyond our and Coriant’s control. As a result of any one or more of these factors, among others, the operations and financial performance of Coriant may be negatively affected, which may adversely affect the combined company’s future financial results.

The consummation of the Acquisition is subject to a number of conditions and if these conditions are not satisfied or waived, the Acquisition will not be consummated.

The proposed Acquisition of Coriant by us pursuant to the Purchase Agreement is subject to a number of conditions that must be satisfied prior to the consummation of the Acquisition and the closing of the Acquisition may not occur. Should the Acquisition fail to close for any reason, the business, reputation, financial condition and results of operations of Coriant’s and/or us may be materially adversely affected. The closing conditions under the Purchase Agreement include, among others:

For both us and Coriant, the obligation to consummate the Acquisition is also subject to the accuracy of representations and warranties of, and the performance of obligations of, the other party, in each case as set forth in the Purchase Agreement, subject to specified materiality exceptions. As a result of the above mentioned conditions and the other conditions described in the Purchase Agreement, there can be no assurance that the Acquisition will be consummated. Subject to certain exceptions, an adverse change in the business, financial condition, results of operations or prospects of us or Coriant’s prior to the completion of the Acquisition will not permit us to terminate the Acquisition, even if such changes would have a material adverse effect on Coriant or us.

If the Acquisition is not consummated, the notes will remain outstanding unless we elect to redeem the notes as described under “Description of Notes—Unwind Redemption.” See also “Risk Factors—Risks Related to the Notes—If we fail to consummate our acquisition of Coriant, we may redeem the notes at a redemption price that may be less than the value of your notes” and “—This offering is not contingent upon consummation of the Acquisition or the terms of the Acquisition, and our stock price could be adversely affected by any failure or delay in completing the Acquisition, as well as any failure to complete the Acquisition on the terms currently contemplated” for more information.

If we are unable to maintain effective internal control over financial reporting for the combined companies following the Acquisition, we may fail to prevent or detect material misstatements in our financial statements, in which case investors may lose confidence in the accuracy and completeness of our financial statements.

We and Coriant currently maintain separate internal control over financial reporting with different financial reporting processes and different process control software. After the closing of the Acquisition, we plan to integrate our internal control over financial reporting and move the combined companies to a single enterprise resource planning system. We may encounter difficulties and unanticipated issues in combining our respective accounting systems due to the complexity of the financial reporting processes. We may also identify errors or misstatements that could require audit adjustments. If we are unable to implement and maintain effective internal control over financial reporting following completion of the Acquisition, we may fail to prevent or detect material misstatements in our financial statements, in which case investors may lose confidence in the accuracy and completeness of our financial reports and the market price of our securities may decline.

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As a result of the Acquisition, our goodwill and intangible assets on our consolidated balance sheet will increase substantially. If our goodwill or assets become impaired in the future, we would be required to record a non-cash charge to earnings, which would also reduce our stockholders’ equity.

Our intangible assets, including goodwill, represent a significant portion of our total assets. As a result of the Acquisition, our goodwill and intangible assets on our consolidated balance sheet will increase substantially. Under U.S. GAAP, goodwill and intangible assets are reviewed for impairment on an annual basis (or more frequently if events or circumstances indicate that their carrying value may not be recoverable). In addition, certain of our or Coriant’s tangible assets, such as inventory, machinery and equipment, may experience impairment in their value. If our goodwill or other assets are determined to be impaired in the future, we will be required to record a non-cash charge to earnings during the period in which the impairment is determined, and any such charges may be material.

Coriant may have liabilities that are not known, probable or estimable at this time.

As a result of the Acquisition, Coriant will become a subsidiary of the Company and remain subject to its past, current and future liabilities, including the liabilities described in Coriant’s financial statements, which are incorporated in this prospectus supplement (other than indebtedness discharged in connection with the Acquisition). There could be unasserted claims or assessments against or affecting Coriant, including the failure to comply with applicable laws, regulations, orders and consent decrees or infringement or misappropriation of third party intellectual property or other proprietary rights that we failed or were unable to discover or identify in the course of performing our due diligence investigation of Coriant. In addition, there are liabilities of Coriant that are neither probable nor estimable at this time that may become probable or estimable in the future, including indemnification requests received from customers of Coriant relating to claims of infringement or misappropriation of third party intellectual property or other proprietary rights, tax liabilities arising in connection with ongoing or future tax audits and liabilities in connection with other past, current and future legal claims and litigation. Any such liabilities, individually or in the aggregate, could have a material adverse effect on our financial results. We may learn additional information about Coriant that adversely affects us, such as unknown, unasserted, or contingent liabilities and issues relating to compliance with applicable laws or infringement or misappropriation of third party intellectual property or other proprietary rights (including related indemnity requests from customers).

Coriant has not yet adopted accounting standard ASC 606 relating to revenue recognition and Subtopic 340-40 related to other assets and deferred costs. As a result, Coriant’s financial statements for the six months ended June 30, 2018 are presented on the basis of a different revenue recognition standard than our financial statements for the corresponding period and are not directly comparable. The adoption of ASC 606 and Subtopic 340-40 may have a material adverse effect on Coriant’s results of operations and financial position.

In May 2014, the FASB and the International Accounting Standards Board jointly issued a comprehensive new revenue recognition standard, ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASC 606”) that supersedes nearly all existing revenue recognition guidance under U.S. GAAP and International Financial Reporting Standards. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The new standard also requires additional disclosure about the nature, amount, timing, and uncertainty of revenue that is recognized. ASC 606 also includes Subtopic 340-40, “Other Assets and Deferred Costs—Contracts with Customers,” which requires the deferral of incremental costs of obtaining a contract with a customer.

We adopted ASC 606 as of December 31, 2017 using the modified retrospective transition method, which means that results for the reporting periods after December 31, 2017 are presented under ASC 606, while prior period amounts are not adjusted and continue to be reported in accordance with our historical accounting practices. We recorded a net reduction to the opening balance of our accumulated deficit of $15.4 million as of

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December 31, 2017 due to the cumulative impact of adopting ASC 606, with the impact primarily related to our services revenue, and the impact to revenue for the six months ended June 30, 2018 was a decrease of $1.6 million as a result of applying ASC 606. See Note 3, “Revenue Recognition” to the Notes to unaudited Condensed Consolidated Financial Statements of our Quarterly Report on Form 10-Q for the quarter ended June 30, 2018, which is incorporated by reference in this prospectus supplement for further information.

However, nonpublic companies are not yet required to implement ASC 606 and Subtopic 340-40 and, as a result, Coriant has not yet adopted ASC 606 and Subtopic 340-40. Accordingly, Coriant’s financial statements for the six months ended June 30, 2018 are not presented under ASC 606 and Subtopic 340-40, which means that they are presented on the basis of a different revenue recognition standard than our financial statements for the corresponding period. The adoption of ASC 606 and Subtopic 340-40 may result in a material decrease to Coriant’s revenue for the six months ended June 30, 2018, and may also result in a material decrease to deferred revenue, accounts receivable or other assets of Coriant, or a material increase in liabilities of Coriant, as of June 30, 2018. However, it is difficult to predict the exact impact of this change to accounting principles. The adoption of ASC 606 and Subtopic 340-40 could have a material adverse effect on Coriant’s financial position and results of operations as of and for the six months ended June 30, 2018 and future periods and could also have a material adverse effect on the perceived value of the Acquisition relative to Coriant’s reported earnings. In addition, any difficulties in the implementation and preparation of ASC 606 and Subtopic 340-40 with respect to the Coriant financial statements, could cause us to fail to meet our financial reporting obligations, which could result in regulatory discipline and damage our reputation with investors and could cause investors to lose confidence in the accuracy and completeness of our financial reports and the market price for our securities may decline.

The pro forma financial data included in this prospectus supplement may not be an indication of the combined company’s financial condition or results of operations following the Acquisition.

The pro forma financial data included herein are for illustrative purposes only, based on various estimated adjustments, assumptions, and preliminary estimates and may not be an indication of the combined company’s financial condition or results of operations following the Acquisition for several reasons. The actual financial condition and results of operations of the combined company following the Acquisition may not be consistent with, or evident from, the pro forma financial data. In addition, the assumptions used in preparing the pro forma financial data may not prove to be accurate, and other factors may materially adversely affect the combined company’s financial condition or results of operations following the Acquisition. Moreover, because Coriant has not yet adopted ASC 606 and Subtopic 340-40 as described above, we have obtained permission from the SEC to exclude an unaudited pro forma condensed combined statement of operations for the six months ended June 30, 2018. As a result, the pro forma data included herein does not present the combined company’s results of operations for the six months ended June 30, 2018. The pro forma results of operations for fiscal year 2017 are not necessarily indicative of the pro forma results for the six months ended June 30, 2018 or any other future period. See “Unaudited Pro Forma Condensed Combined Financial Information.”

The unaudited pro forma condensed combined financial information included and incorporated by reference in this prospectus supplement reflect the impact of the Acquisition on our and Coriant’s historical financial information using the acquisition method of accounting, as required under U.S. GAAP. Pursuant to the acquisition method, we have been determined to be the acquirer for accounting purposes. As required under U.S. GAAP, we will record Coriant’s tangible and identifiable intangible assets acquired and liabilities assumed based on their fair values at the acquisition date. The excess of consideration transferred (i.e., purchase price) over the fair value of net assets acquired will be recorded as goodwill. Goodwill is not amortized, but is tested for impairment at least annually or more frequently if circumstances indicate potential impairment. The operating results of Coriant will be reported as part of the combined company on the acquisition date. The final valuation of the tangible and identifiable intangible assets acquired and liabilities assumed have not yet been completed. The completion of the valuation upon consummation of the Acquisition could result in significantly different amortization expenses and balance sheet classifications than those presented in the unaudited pro forma condensed combined financial information included or incorporated in this prospectus supplement.

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Additionally, if the Acquisition occurs, we anticipate incurring significant integration costs, as well as the cost of cost savings initiatives, which have not been reflected in the unaudited pro forma condensed combined financial information included or incorporated in this prospectus supplement. The Acquisition and post-Acquisition integration process may also give rise to unexpected liabilities and costs. Unexpected delays in consummating the Acquisition or in connection with the post-Acquisition integration process may significantly increase the related costs and expenses incurred by us. If any of these circumstances were to occur, operating expenses for the combined business may be higher than expected, reducing operating income and the expected benefits of the Acquisition. In addition, actual financing costs for the combined company may be higher and revenue lower than the expected costs reflected in the unaudited pro forma condensed combined financial information. Higher financing costs would reduce the combined company’s profitability and may reduce cost reduction and other initiatives.

As a result of the Acquisition, Infinera and Coriant may be unable to retain key employees.

Our success after the Acquisition will depend in part upon our ability to retain key employees of ours and Coriant. Key employees may depart because of a variety of reasons relating to the Acquisition. If we and Coriant are unable to retain key personnel who are critical to the successful integration and future operations of the combined company, we could face disruptions in our operations, loss of existing customers, loss of key information, expertise or know-how, and unanticipated additional recruitment and training costs. In addition, the loss of key personnel could diminish the anticipated benefits of the Acquisition.

Risks Related to Our Business

Our quarterly results may vary significantly from period to period, which could make our future results difficult to predict and could cause our operating results to fall below investor or analyst expectations.

Our quarterly results, in particular, our revenue, gross margins, operating expenses, operating margins and net income (loss), have historically varied from period to period and may continue to do so in the future. As a result, comparing our operating results on a period-to-period basis may not be meaningful. Our budgeted expense levels are based, in large part, on our expectations of future revenue and the development efforts associated with that future revenue. Consequently, if our revenue does not meet projected levels in the short-term, our inventory levels, cost of goods sold and operating expenses would be high relative to revenue, resulting in potential operating losses. For example, in each of the prior six quarters, we have had operating losses, largely as a result of lower revenue and gross margins.

Factors that may contribute to fluctuations in our quarterly results, many of which are outside our control and may be difficult to predict, include:

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Many factors affecting our results of operations are beyond our control and make it difficult to predict our results for a particular quarter and beyond. If our revenue or operating results do not meet the expectations of investors or securities analysts or fall below any guidance we provide to the market, the price of our common stock may decline substantially.

Any delays in the development and introduction of our new products or in releasing enhancements to our existing products may harm our business.

Because our products are based on complex technologies, including, in many cases, the development of next-generation PICs and specialized ASICs (key components of our optical engines), we may experience unanticipated delays in developing, improving, manufacturing or deploying these products. The development process for our optical engines is lengthy, and any modifications entail significant development cost and risks.

At any given time, various new product introductions and enhancements to our existing products are in the development phase and are not yet ready for commercial manufacturing or deployment. We rely on third parties, some of which are relatively early stage companies, to develop, manufacture and timely deliver components for our next-generation products, which can often require custom development. The development process from laboratory prototype to customer trials, and subsequently to general availability, involves a significant number of simultaneous efforts. These efforts often must be completed in a timely and coordinated manner so that they may be incorporated into the product development cycle for our systems, and include:

Each of these steps, in turn, presents risks of failure, rework or delay, any one of which could decrease the speed and scope of product introduction and marketplace acceptance of our products. New generations of our optical engines as well as intensive software testing are important to the timely introduction of new products and enhancements to our existing products, and are subject to these development risks. In addition, unexpected

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intellectual property disputes, failure of critical design elements, limited or constrained engineering resources, and a host of other development execution risks may delay, or even prevent, the introduction of new products or enhancements to our existing products. If we do not develop and successfully introduce or enhance products in a timely manner, our competitive position will suffer.

As we transition customers to new products, we face significant risk that our new products may not be accepted by our current or new customers. To the extent that we fail to introduce new and innovative products that are adopted by customers, we could fail to obtain an adequate return on these investments and could lose market share to our competitors, which could be difficult or impossible to regain. Similarly, we may face decreased revenue, gross margins and profitability due to a rapid decline in sales of current products as customers hold spending to focus purchases on new product platforms. We could incur significant costs in completing the transition, including costs of inventory write-downs of the current product as customers transition to new product platforms. In addition, products or technologies developed by others may render our products noncompetitive or obsolete and result in significant reduction in orders from our customers and the loss of existing and prospective customers.

Our ability to increase our revenue will depend upon continued growth of demand by consumers and businesses for additional network capacity and on the level and timing of capital spending by our customers.

Our future success depends on factors that increase the amount of data transmitted over communications networks and the growth of optical transport networks to meet the increased demand for optical capacity. These factors include the growth of mobile, video and cloud-based services, increased broadband connectivity and the continuing adoption of high-capacity, revenue-generating services. If demand for such bandwidth does not continue, or slows down, the market for optical transport networking equipment may not continue to grow and our product sales would be negatively impacted.

In addition, demand for our products depends on the level and timing of capital spending in optical networks by service providers as they construct, expand and upgrade the capacity of their optical networks. Capital spending is cyclical in our industry and spending by customers can change on short notice. Any future decisions by our customers to reduce capital spending, whether caused by lower customer demand or weakening economic conditions, changes in government regulations relating to telecommunications and data networks, customer consolidation or other reasons, could have a material adverse effect on our business, results of operations and financial condition.

We are dependent on a small number of key customers for a significant portion of our revenue from period to period and the loss of, or a significant reduction in, orders from one or more of our key customers would reduce our revenue and harm our operating results.

A relatively small number of customers account for a large percentage of our revenue from period to period. For the second quarter of fiscal 2018, our top five customers accounted for approximately 55% of our total revenue. For fiscal year 2017 and the six months ended June 30, 2018, our top five customers accounted for approximately 44% and 54% of our total revenue, respectively. Included in these five customers for fiscal year 2017 is one customer that completed a merger in late 2017, which was a combination of two of our historically larger customers. For fiscal year 2016, our top five customers accounted for approximately 46% of our total revenue. Our business will likely be harmed if any of our key customers are acquired, do not generate as much revenue as we forecast, stop purchasing from us, delay anticipated product purchases, or substantially reduce their orders to us. In addition, our business will be harmed if we fail to maintain our competitive advantage with our key customers or do not add new larger customers over time. We continue to expect a relatively small number of customers to continue to account for a large percentage of revenue from period to period. However, customer consolidation could reduce the number of key customers that generate a significant percentage of our revenue and may increase the risks relating to dependence on a small number of customers.

Our ability to continue to generate revenue from our key customers will depend on our ability to maintain strong relationships with these customers and introduce competitive new products at competitive prices, and we may not be successful at doing so. In most cases, our sales are made to these customers pursuant to standard

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purchase agreements rather than long-term purchase commitments, and orders may be canceled or reduced readily. In the event of a cancellation or reduction of an order, we may not have enough time to reduce operating expenses to minimize the effect of the lost revenue on our business. Our operating results will continue to depend on our ability to sell our products to our key customers.

Increased consolidation among our customers in the communications networking industry has and could continue to adversely affect our business and results of operations.

We have seen increased consolidation in the communications networking industry over the past few years, which has adversely affected our business and results of operations. For example, during 2016, Charter Communications completed its acquisition of Time Warner Cable, Inc. and Altice completed its acquisition of Cablevision, and during the first quarter of 2017, Verizon completed its acquisition of XO Communications. In addition, in the fourth quarter of 2017, CenturyLink completed its acquisition of Level 3 Communications. Customer consolidation has led to changes in buying patterns, slowdowns in spending, redeployment of existing equipment and re-architecture of parts of existing networks or future networks, as the combined companies evaluate the needs of the combined business. Moreover, the significant purchasing power of these large companies can increase pricing and competitive pressures for us, including the potential for decreases in our average selling prices. If one of our customers is acquired by another company that does not rely on us to provide it with products or relies on another provider of similar products, we may lose that customer’s business. Such consolidation may further reduce the number of customers that generate a significant percentage of our revenue and may exacerbate the risks relating to dependence on a small number of customers. Any of the foregoing results will adversely affect our business, financial condition and results of operations.

Our gross margin may fluctuate from period to period and may be adversely affected by a number of factors, some of which are beyond our control.

Our gross margin fluctuates from period to period and varies by customer and by product. Over the past eight fiscal quarters, our gross margin has ranged from 24.1% to 45.6%. Our gross margin is likely to continue to fluctuate and will be affected by a number of factors, including:

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It is likely that the average unit prices of our products will decrease over time in response to competitive pricing pressures. In addition, some of our customer contracts contain clauses that require us to annually decrease the sales price of our products to these customers. In response, we will need to reduce the cost of our products through manufacturing efficiencies, design improvements and cost reductions from our supply partners. If these efforts are not successful or if we are unable to reduce our costs by more than the reduction in the price of our products, our gross margin will decline, causing our operating results to decline. Fluctuations in gross margin may make it difficult to manage our business and achieve or maintain profitability.

Aggressive business tactics by our competitors may harm our business.

The markets in which we compete are extremely competitive and this often results in aggressive business tactics by our competitors, including:

The level of competition and pricing pressure tend to increase when competing for larger high-profile opportunities or during periods of economic weakness when there are fewer network build-out projects. If we fail to compete successfully against our current and future competitors, or if our current or future competitors continue or expand their aggressive business tactics, including those described above, demand for our products could decline, we could experience delays or cancellations of customer orders, and/or we could be required to reduce our prices to compete in the market.

If we lose key personnel or fail to attract and retain additional qualified personnel when needed, our business may be harmed.

Our success depends to a significant degree upon the continued contributions of our key management, engineering, sales and marketing, and finance personnel, many of whom would be difficult to replace. For example, senior members of our engineering team have unique technical experience that would be difficult to replace. We do not have long-term employment contracts or key person life insurance covering any of our key personnel. Because our products are complex, we must hire and retain highly trained customer service and support personnel to ensure that the deployment of our products does not result in network disruption for our customers. We believe our future success will depend in large part upon our ability to identify, attract and retain highly skilled personnel. Competition for these individuals is intense in our industry, especially in the San Francisco Bay Area where we are headquartered. We may not succeed in identifying, attracting and retaining appropriate personnel. The loss of the services of any of our key personnel, the inability to identify, attract or retain qualified personnel in the future or delays in hiring qualified personnel, particularly engineers and sales personnel, could make it difficult for us to manage our business and meet key objectives, such as timely product introductions.

The markets in which we compete are highly competitive and we may not be able to compete effectively.

Competition in the optical transport networking equipment market is intense. Our main competitors include WDM system suppliers, such as Adva, Ciena, Cisco, Coriant, Fujitsu, Huawei, Nokia and ZTE. In addition, there are several smaller but established companies that offer one or more products that compete with our offerings.

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Competition in the markets we serve is based on any one or a combination of the following factors:

In addition to our current competitors, other companies have, or may in the future develop, products that are or could be competitive with our products. We also could encounter competitor consolidation in the markets in which we compete, which could lead to a changing competitive landscape, capabilities and market share, and could impact our results of operations.

Some of our competitors have substantially greater name recognition, technical, financial and marketing resources, and better established relationships with potential customers than we have. Many of our competitors have more resources and more experience in developing or acquiring new products and technologies, and in creating market awareness for those products and technologies. In addition, many of our competitors have the financial resources to offer competitive products at aggressive pricing levels that could prevent us from competing effectively. Further, many of our competitors have built long-standing relationships with some of our prospective and existing customers and have the ability to provide financing to customers and could, therefore, have an inherent advantage in selling products to those customers.

We also compete with low-cost producers that can increase pricing pressure on us and a number of smaller companies that provide competition for a specific product, customer segment or geographic market. In addition, we may also face increased competition from system and component companies that develop products based on off-the-shelf hardware that offers the latest commercially available technologies. Due to the narrower focus of their efforts, these competitors may achieve commercial availability of their products more quickly than we can and may provide attractive alternatives to our customers.

We must respond to rapid technological change and comply with evolving industry standards and requirements for our products to be successful.

The optical transport networking equipment market is characterized by rapid technological change, changes in customer requirements and evolving industry standards. We continually invest in research and development to sustain or enhance our existing products, but the introduction of new communications technologies and the emergence of new industry standards or requirements could render our products obsolete. Further, in developing our products, we have made, and will continue to make, assumptions with respect to which standards or requirements will be adopted by our customers and competitors. If the standards or requirements adopted by our prospective customers are different from those on which we have focused our efforts, market acceptance of our products would be reduced or delayed and our business would be harmed.

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We are continuing to invest a significant portion of our research and development efforts in the development of our next-generation products. We expect our competitors will continue to improve the performance of their existing products and introduce new products and technologies and to influence customers’ buying criteria so as to emphasize product capabilities that we do not, or may not, possess. To be competitive, we must anticipate future customer requirements and continue to invest significant resources in research and development, sales and marketing, and customer support. If we do not anticipate these future customer requirements and invest in the technologies necessary to enable us to have and to sell the appropriate solutions, it may limit our competitive position and future sales, which would have an adverse effect on our business and financial condition. We may not have sufficient resources to make these investments and we may not be able to make the technological advances necessary to be competitive.

The manufacturing process for our PICs is very complex and the partial or complete loss of our manufacturing facilities, or a reduction in yields or an inability to scale capacity to meet customer demands could harm our business.

The manufacturing process for our PICs and certain components of our products is very complex. In the event that any of the manufacturing facilities utilized to build these components were fully or partially destroyed, as a result of fire, water damage, or otherwise, it would limit our ability to produce our products. Because of the complex nature of our manufacturing facilities, such loss would take a considerable amount of time to repair or rebuild. The partial or complete loss of any of our manufacturing facilities, or an event causing the interruption in our use of such facility for any extended period of time would cause our business, financial condition and operating results to be harmed.

Minor deviations in the PIC manufacturing process can cause substantial decreases in yields and, in some cases, cause production to be suspended. In the past, we have had significant variances in our PIC yields, including production interruptions and suspensions and may have continued yield variances, including additional interruptions or suspensions in the future. Lower than expected yields from our PIC manufacturing process or defects, integration issues or other performance problems in our products could limit our ability to satisfy customer demand requirements, and could damage customer relations and cause business reputation problems, harming our business and operating results.

Our inability to obtain sufficient manufacturing capacity to meet demand, either in our own facilities or through foundry or similar arrangements with third parties, could harm our relationships with our customers, our business and our operating results.

Our large customers have substantial negotiating leverage, which may cause us to agree to terms and conditions that result in decreased revenue due to lower average selling prices and potentially increased cost of sales leading to lower gross margin, all of which would harm our operating results.

Many of our customers are large service providers that have substantial purchasing power and leverage in negotiating contractual arrangements with us. In addition, customer consolidation in the past few years has created combined companies that are even larger and have greater negotiating leverage. Our customers have and may continue to seek advantageous pricing, payment and other commercial terms. We have and may continue to agree to unfavorable commercial terms with these customers, including the potential of reducing the average selling price of our products, increasing cost of sales or agreeing to extended payment terms in response to these commercial requirements or competitive pricing pressures. To maintain acceptable operating results, we will need to comply with these commercial terms, develop and introduce new products and product enhancements on a timely basis, and continue to reduce our costs.

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We are dependent on sole source and limited source suppliers for several key components, and if we fail to obtain these components on a timely basis, we will not meet our customers’ product delivery requirements.

We currently purchase several key components for our products from sole or limited sources. In particular, we rely on our own production of certain components of our products, such as PICs, and on third parties, including sole source and limited source suppliers, for certain of the components of our products, including ASICs, field-programmable gate arrays, processors, and other semiconductor and optical components. We have increased our reliance on third parties to develop and manufacture components for certain products, some of which require custom development. We purchase most of these components on a purchase order basis and only have long-term contracts with these sole source or limited source suppliers. If any of our sole source or limited source suppliers suffer from capacity constraints, lower than expected yields, deployment delays, work stoppages or any other reduction or disruption in output, they may be unable to meet our delivery schedule which could result in lost revenue, additional product costs and deployment delays that could harm our business and customer relationships. Further, our suppliers could enter into exclusive arrangements with our competitors, refuse to sell their products or components to us at commercially reasonable prices or at all, go out of business or discontinue their relationships with us. We may be unable to develop alternative sources for these components.

The loss of a source of supply, or lack of sufficient availability of key components, could require us to redesign products that use such components, which could result in lost revenue, additional product costs and deployment delays that could harm our business and customer relationships. In addition, if our contract manufacturers do not receive critical components in a timely manner to build our products, then we would not be able to ship in a timely manner and would, therefore, be unable to meet our prospective customers’ product delivery requirements. In the past, we have experienced delivery delays because of lack of availability of components or reliability issues with components that we were purchasing. In addition, some of our suppliers have gone out of business, merged with another supplier, or limited their supply of components to us, which may cause us to experience longer than normal lead times, supply delays and increased prices. We may in the future experience a shortage of certain components as a result of our own manufacturing issues, manufacturing issues at our suppliers or contract manufacturers, capacity problems experienced by our suppliers or contract manufacturers, strong demand in the industry for such components, or other disruptions in our supply chain. In addition, disruptions to global macroeconomic conditions may create pressure on us and our suppliers to accurately project overall component demand and manufacturing capacity. These supplier disruptions may continue to occur in the future, which could limit our ability to produce our products and cause us to fail to meet a customer’s delivery requirements. Any failure to meet our customers’ product delivery requirements could harm our reputation and our customer relationships, either of which would harm our business and operating results.

If we fail to accurately forecast our manufacturing requirements or customer demand, we could incur additional costs, including inventory write-downs or equipment write-offs, which would adversely affect our business and results of operations.

We generate forecasts of future demand for our products several months prior to the scheduled delivery to our prospective customers. This requires us to make significant investments before we know if corresponding revenue will be recognized. Lead times for materials and components, including ASICs, that we need to order for the manufacture of our products vary significantly and depend on factors such as the specific supplier, contract terms and demand for each component at a given time. In the past, we have experienced lengthening in lead times for certain components. If the lead times for components are lengthened, we may be required to purchase increased levels of such components to satisfy our delivery commitments to our customers. In addition, we must manage our inventory to ensure we continue to meet our commitments as we introduce new products or make enhancements to our existing products.

If we overestimate market demand for our products and, as a result, increase our inventory in anticipation of customer orders that do not materialize, we will have excess inventory, which could result in increased risk of

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obsolescence and significant inventory write-downs. Furthermore, this will result in reduced production volumes and our fixed costs will be spread across fewer units, increasing our per unit costs. If we underestimate demand for our products, we will have inadequate inventory, which could slow down or interrupt the manufacturing of our products and result in delays in shipments and our ability to recognize revenue. In addition, we may be unable to meet our supply commitments to customers, which could result in a loss of certain customer opportunities or a breach of our customer agreements resulting in payment of damages.

Product performance problems, including undetected errors in our hardware or software, or deployment delays could harm our business and reputation.

The development and production of products with high technology content is complicated and often involves problems with software, components and manufacturing methods. Complex hardware and software systems, such as our products, can often contain undetected errors when first introduced or as new versions are released. In addition, errors associated with components we purchase from third parties, including customized components, may be difficult to resolve. We have experienced issues in the past in connection with our products, including failures due to the receipt of faulty components from our suppliers. In addition, performance issues can be heightened during periods where we are developing and introducing multiple new products to the market, as any performance issues we encounter in one technology or product could impact the performance or timing of delivery of other products. Our products may suffer degradation of performance and reliability over time.

If reliability, quality or network monitoring problems develop, a number of negative effects on our business could result, including:

Because we outsource the manufacturing of certain components of our products, we may also be subject to product performance problems as a result of the acts or omissions of third parties.

From time to time, we encounter interruptions or delays in the activation of our products at a customer’s site. These interruptions or delays may result from product performance problems or from issues with installation and activation, some of which are outside our control. If we experience significant interruptions or delays that we cannot promptly resolve, the associated revenue for these installations may be delayed or confidence in our products could be undermined, which could cause us to lose customers and fail to add new customers.

If our contract manufacturers do not perform as we expect, our business may be harmed.

We rely on third party contract manufacturers to perform a portion of the manufacturing of our products, and our future success will depend on our ability to have sufficient volumes of our products manufactured in a cost-effective and quality-controlled manner. We have engaged third parties to manufacture certain elements of

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our products at multiple contract manufacturing sites located around the world but do not have long-term agreements in place with some of our manufacturers and suppliers that will guarantee product availability, or the continuation of particular pricing or payment terms. There are a number of risks associated with our dependence on contract manufacturers, including:

Any of these risks could impair our ability to fulfill orders. Any delays by our contract manufacturers may cause us to be unable to meet the delivery requirements of our customers, which could decrease customer satisfaction and harm our product sales. In addition, if our contract manufacturers are unable or unwilling to continue manufacturing our products or components of our products in required volumes or our relationship with any of our contract manufacturers is discontinued for any reason, we would be required to identify and qualify alternative manufacturers, which could cause us to be unable to meet our supply requirements to our customers and result in the breach of our customer agreements. Qualifying a new contract manufacturer and commencing volume production is expensive and time-consuming and if we are required to change or qualify a new contract manufacturer, we could lose revenue and damage our customer relationships.

Our sales cycle can be long and unpredictable, which could result in an unexpected revenue shortfall in any given quarter.

Our products can have a lengthy sales cycle, which can extend from six to twelve months and may take even longer for larger prospective customers. Our prospective customers conduct significant evaluation, testing, implementation and acceptance procedures before they purchase our products. We incur substantial sales and marketing expenses and expend significant management effort during this time, regardless of whether we make a sale.

Because the purchase of our equipment involves substantial cost, most of our customers wait to purchase our equipment until they are ready to deploy it in their network. As a result, it is difficult for us to accurately predict the timing of future purchases by our customers. In addition, product purchases are often subject to budget constraints, multiple approvals and unplanned administrative processing and other delays. If sales expected from customers for a particular quarter are not realized in that quarter or at all, our revenue will be negatively impacted.

If we need additional capital in the future, it may not be available to us on favorable terms, or at all.

Our business requires significant capital. We have historically relied on outside debt or equity financing as well as cash flow from operations to fund our operations, capital expenditures and expansion. We may require additional capital from equity or debt financings in the future to fund our operations, respond to competitive pressures or strategic opportunities or to refinance our existing debt obligations. In the event that we require additional capital, we may not be able to secure timely additional financing on favorable terms, or at all. The terms of any additional financing may place limits on our financial and operating flexibility. If we raise additional funds through further issuances of equity, convertible debt securities or other securities convertible

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into equity, our existing stockholders could suffer dilution in their percentage ownership of our company, and any new securities we issue could have rights, preferences and privileges senior to those of holders of our common stock. If we are unable to obtain adequate financing or financing on terms satisfactory to us, if and when we require it, our ability to grow or support our business and to respond to business challenges could be limited and our business will be harmed.

If we fail to protect our intellectual property rights, our competitive position could be harmed or we could incur significant expense to enforce our rights.

We depend on our ability to protect our proprietary technology. We rely on a combination of methods to protect our intellectual property, including limiting access to certain information, and utilizing trade secret, patent, copyright and trademark laws and confidentiality agreements with employees and third parties, all of which offer only limited protection. The steps we have taken to protect our proprietary rights may be inadequate to preclude misappropriation or unauthorized disclosure of our proprietary information or infringement of our intellectual property rights, and our ability to police such misappropriation, unauthorized disclosure or infringement is uncertain, particularly in countries outside of the United States. This is likely to become an increasingly important issue if we expand our operations and product development into countries that provide a lower level of intellectual property protection. We do not know whether any of our pending patent applications will result in the issuance of patents or whether the examination process will require us to narrow our claims, and even if patents are issued, they may be contested, circumvented or invalidated. Moreover, the rights granted under any issued patents may not provide us with a competitive advantage, and, as with any technology, competitors may be able to develop similar or superior technologies to our own now or in the future.

Protecting against the unauthorized use of our products, trademarks and other proprietary rights is expensive, difficult, time consuming and, in some cases, impossible. Litigation may be necessary in the future to enforce or defend our intellectual property rights, to protect our trade secrets or to determine the validity or scope of the proprietary rights of others. Such litigation could result in substantial cost and diversion of management resources, either of which could harm our business, financial condition and operating results. Furthermore, many of our current and potential competitors have the ability to dedicate substantially greater resources to enforce their intellectual property rights than we do. Accordingly, despite our efforts, we may not be able to prevent third parties from infringing upon or misappropriating our intellectual property.

Claims by others that we infringe their intellectual property could harm our business.

Our industry is characterized by the existence of a large number of patents and frequent claims and related litigation regarding patent and other intellectual property rights. In particular, many leading companies in the optical transport networking industry, including our competitors, have extensive patent portfolios with respect to optical transport networking technology. In addition, patent holding companies seek to monetize patents they have purchased or otherwise obtained. We expect that infringement claims may increase as the number of products and competitors in our market increases and overlaps occur. From time to time, third parties may assert exclusive patent, copyright, trademark and other intellectual property rights to technologies and related standards that are important to our business or seek to invalidate the proprietary rights that we hold. Competitors or other third parties have, and may continue to assert claims or initiate litigation or other proceedings against us or our manufacturers, suppliers or customers alleging infringement of their proprietary rights, or seeking to invalidate our proprietary rights, with respect to our products and technology. In addition, we have had certain patent licenses with third parties that have not been renewed, and if we cannot successfully renew these licenses, we could face claims of infringement. In the event that we are unsuccessful in defending against any such claims, or any resulting lawsuit or proceedings, we could incur liability for damages and/or have valuable proprietary rights invalidated. For additional information regarding certain of the legal proceedings in which we are involved, see Item 3, “Legal Proceedings,” contained in Part I of our Quarterly Report on Form 10-Q for the six months ended June 30, 2018 and our Annual Report on Form 10-K for the fiscal year ended December 30, 2017 incorporated by reference in this prospectus supplement.

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Any claim of infringement from a third party, even one without merit, could cause us to incur substantial costs defending against the claim, and could distract our management from running our business. Furthermore, a party making such a claim, if successful, could secure a judgment that requires us to pay substantial damages or could include an injunction or other court order that could prevent us from offering our products. In addition, we might be required to seek a license for the use of such intellectual property, which may not be available on commercially reasonable terms or at all. Alternatively, we may be required to develop non-infringing technology, which would require significant effort and expense and may ultimately not be successful. Any of these events could harm our business, financial condition and operating results. Competitors and other third parties have and may continue to assert infringement claims against our customers and sales partners. Any of these claims would require us to initiate or defend potentially protracted and costly litigation on their behalf, regardless of the merits of these claims, because we generally indemnify our customers and sales partners from claims of infringement of proprietary rights of third parties. If any of these claims succeed, we may be forced to pay damages on behalf of our customers or sales partners, which could have an adverse effect on our business, financial condition and operating results.

We may also be required to indemnify some customers under our contracts if a third party alleges, or a court finds, that our products have infringed upon the proprietary rights of other parties. From time to time, we have agreed to indemnify certain customers for claims made against our products, where such claims allege infringement of third party intellectual property rights, including, but not limited to, patents, registered trademarks and/or copyrights. If we are required to make a significant payment under any of our indemnification obligations, our result of operations may be harmed.

We incorporate free and open source licensed software into our products. Although we monitor our use of such open source software closely, the terms of many open source licenses have not been interpreted by U.S. courts, and there is a risk that such licenses could be construed in a manner that could impose unanticipated conditions or restrictions on our ability to commercialize our products. In addition, non-compliance with open source software license terms and conditions could subject us to potential liability, including intellectual property infringement and/or contract claims. In such events, we may be required to seek licenses from third parties in order to continue offering our products, to re-engineer our products or to discontinue the sale of our products in the event re-engineering cannot be accomplished in a timely manner, any of which could adversely affect our business, operating results and financial condition.

Unfavorable macroeconomic and market conditions may adversely affect our industry, business and financial results.

Our business depends on the overall demand for additional bandwidth capacity and on the economic health and willingness of our customers and potential customers to make capital commitments to purchase our products and services. As a result of macroeconomic or market uncertainty, we may face new risks that we have not yet identified. In addition, a number of the risks associated with our business, which are disclosed in these risk factors, may increase in likelihood, magnitude or duration.

In the past, unfavorable macroeconomic and market conditions have resulted in sustained periods of decreased demand for optical communications products. These conditions may also result in the tightening of credit markets, which may limit or delay our customers’ ability to obtain necessary financing for their purchases of our products. A lack of liquidity in the capital markets or the continued uncertainty in the global economic environment may cause our customers to delay or cancel their purchases, increase the time they take to pay or default on their payment obligations, each of which would negatively affect our business and operating results. Weakness and uncertainty in the global economy could cause some of our customers to become illiquid, delay payments or adversely affect our collection of their accounts, which could result in a higher level of bad debt expense. In addition, currency fluctuations could negatively affect our international customers’ ability or desire to purchase our products.

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Challenging economic conditions have from time to time contributed to slowdowns in the telecommunications industry in which we operate. Such slowdowns may result in:

A lack of liquidity and economic uncertainty may adversely affect our suppliers or the terms on which we purchase products from these suppliers. It may also cause some of our suppliers to become illiquid. Any of these impacts could limit our ability to obtain components for our products from these suppliers and could adversely impact our supply chain or the delivery schedule to our customers. This also could require us to purchase more expensive components, or re-design our products, which could cause increases in the cost of our products and delays in the manufacturing and delivery of our products. Such events could harm our gross margin and harm our reputation and our customer relationships, either of which could harm our business and operating results.

Our international sales and operations subject us to additional risks that may harm our operating results.

Sales of our products into international markets are an important part of our business. During the first half of fiscal year 2018, fiscal year 2017 and fiscal year 2016, we derived approximately 39%, 42% and 38%, respectively, of our revenue from customers outside of the United States. We expect that significant management attention and financial resources will be required for our international activities over the foreseeable future as we continue to operate in international markets. In some countries, our success in selling our products and growing revenue will depend in part on our ability to form relationships with local partners. Our inability to identify appropriate partners or reach mutually satisfactory arrangements for international sales of our products could impact our ability to maintain or increase international market demand for our products. In addition, many of the companies we compete against internationally have greater name recognition and a more substantial sales and marketing presence.

We have sales and support personnel in numerous countries worldwide. In addition, we have established development centers in Canada, India and Sweden. There is no assurance that our reliance upon development resources in international locations will enable us to achieve meaningful cost reductions or greater resource efficiency.

Our international operations are subject to inherent risks, and our future results could be adversely affected by a variety of factors, many of which are outside of our control, including:

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International customers may also require that we comply with certain testing or customization of our products to conform to local standards. The product development costs to test or customize our products could be extensive and a material expense for us.

Our international operations are subject to increasingly complex foreign and U.S. laws and regulations, including but not limited to anti-corruption laws, such as the Foreign Corrupt Practices Act and the UK Bribery Act and equivalent laws in other jurisdictions, antitrust or competition laws, and data privacy laws, among others. Violations of these laws and regulations could result in fines and penalties, criminal sanctions against us, our officers, or our employees, prohibitions on the conduct of our business and on our ability to offer our products and services in one or more countries, and could also materially affect our reputation, our international expansion efforts, our ability to attract and retain employees, our business, and our operating results. Although we have implemented policies, procedures and training designed to ensure compliance with these laws and regulations, there can be no complete assurance that any individual employee, contractor or agent will not violate our policies. Additionally, the costs of complying with these laws (including the costs of investigations, auditing and monitoring) could also adversely affect our current or future business.

As we continue to expand our business globally, our success will depend, in large part, on our ability to effectively anticipate and manage these and other risks and expenses associated with our international operations. For example, political instability and uncertainty in the European Union and, in particular, the United Kingdom’s pending exit from the E.U. (Brexit) as well as other countries potentially choosing to exit the E.U., could slow economic growth in the region, affect foreign exchange rates, and could further discourage near-term economic activity, including our customers delaying purchases of our products. In addition, protectionist trade legislation in the United States or foreign countries, including changes in the current tariff structures, export or import compliance laws, or other trade policies, could reduce our ability to sell our products in foreign markets, the ability of foreign customers to purchase our products, and our ability to import components, parts and products from foreign suppliers. The President of the United States has proposed significant changes in trade policies, including tariffs and government regulations affecting trade between the United States and other countries. Potential changes which are being contemplated include the renegotiation or termination of trade agreements and the imposition of higher tariffs on imports into the United States. Any such actions could increase the cost to us of such components, parts and products (whether imported directly or indirectly) and cause increases in the prices at which we sell our products to our customers or could reduce our margins, which could materially adversely affect our business, financial condition and results of operations. Our failure to manage any of these risks successfully could harm our international operations and reduce our international sales, and business generally, adversely affecting our business, operating results and financial condition.

We may be adversely affected by fluctuations in currency exchange rates.

A portion of our sales and expenses stem from countries outside of the United States, and are in currencies other than U.S. dollars, and therefore subject to foreign currency fluctuation. Accordingly, fluctuations in foreign currency rates could have a material impact on our financial results in future periods. We may enter into other financial contracts to reduce the impact of foreign currency fluctuations. We currently enter into foreign currency exchange forward contracts to reduce the impact of foreign currency fluctuations on accounts receivable, and also to reduce the volatility of cash flows primarily related to forecasted foreign currency revenue and expenses. These forward contracts reduce the impact of currency exchange rate movements on certain transactions, but do not cover all foreign-denominated transactions and therefore do not entirely eliminate the impact of fluctuations in exchange rates that could negatively affect our results of operations and financial condition.

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Our effective tax rate may increase or fluctuate, which could increase our income tax expense and reduce our net income.

Our effective tax rate can be adversely affected by several factors, many of which are outside of our control, including:

The international tax environment continues to change as a result of both coordinated actions by governments and unilateral measures designed by individual countries, both intended to tackle concerns over base erosion and profit shifting (“BEPS”) and perceived international tax avoidance techniques. The recommendations of the BEPS Project led by the Organization for Economic Cooperation and Development are involved in much of the coordinated activity, although the timing and methods of implementation vary. In addition, U.S. tax reform continues to be a priority for the current administration, and changes to legislation commonly referred to as the Tax Cuts and Jobs Act enacted on December 22, 2017 could adversely affect our effective tax rate and our results of operations.

If we fail to maintain effective internal control over financial reporting in the future, the accuracy and timing of our financial reporting may be adversely affected.

We are required to comply with Section 404 of the Sarbanes-Oxley Act of 2002. The provisions of the act require, among other things, that we maintain effective internal control over financial reporting and disclosure controls and procedures. Preparing our financial statements involves a number of complex processes, many of which are done manually and are dependent upon individual data input or review. These processes include, but are not limited to, calculating revenue, deferred revenue and inventory costs. While we continue to automate our processes and enhance our review and put in place controls to reduce the likelihood for errors, we expect that for the foreseeable future, many of our processes will remain manually intensive and thus subject to human error.

Any acquisitions we make could disrupt our business and harm our financial condition and operations.

We may make strategic acquisitions of businesses, technologies and other assets. If we are not able to achieve the anticipated strategic benefits of such acquisitions, it could adversely affect our business, financial condition and results of operations. In addition, the market price of our common stock could be adversely affected if the integration or the anticipated financial and strategic benefits of such acquisitions are not realized as rapidly as, or to the extent anticipated by investors and securities analysts.

The expansion of our business through acquisitions allows us to complement our technological capabilities and address new markets. In the event of any future acquisitions, we may not ultimately strengthen our competitive position or achieve our goals, or they may be viewed negatively by customers, financial markets or investors and we could:

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Acquisitions can result in adverse tax consequences, warranty or product liability exposure related to acquired assets, additional stock-based compensation expense, and write-up of acquired inventory to fair value. In addition, we may record goodwill and other purchased intangible assets in connection with an acquisition and incur impairment charges in the future. If our actual results, or the plans and estimates used in future impairment analyses, are less favorable than the original estimates used to assess the recoverability of these assets, we could incur additional impairment charges.

Acquisitions also involve numerous risks that could disrupt our ongoing business and distract our management team, including:

Our failure to adequately manage the risks associated with an acquisition could have an adverse effect on our business, financial condition and operating results.

Unforeseen health, safety and environmental costs could harm our business.

Our manufacturing operations use substances that are regulated by various federal, state and international laws governing health, safety and the environment, including the Waste Electrical and Electronic Equipment Directive, Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment, and the Registration, Evaluation, Authorization, and Restriction of Chemicals regulations adopted by the European Union. If we experience a problem with complying with these regulations it could cause an interruption or delay in our manufacturing operations or it could cause us to incur liabilities for any costs related to health, safety or environmental remediation. We could also be subject to liability if we do not handle these substances in compliance with safety standards for storage and transportation and applicable laws. If we experience a problem or fail to comply with such safety standards, our business, financial condition and operating results may be harmed.

We are subject to governmental regulations that could adversely affect our business.

We are subject to U.S. and foreign trade control laws that may limit where and to whom we sell our products. These trade control laws also limit our ability to conduct product development activities in certain countries and restrict the handling of our U.S. export controlled technology. In addition, various countries regulate the import of certain technologies and have enacted laws that could limit our ability to distribute our products and certain product features or could limit our customers’ ability to implement our products in those countries. Changes in our products or changes in U.S. and foreign import and export regulations may create delays in the introduction of our products in international markets, prevent our customers with international operations from deploying our products throughout their global systems or, in some cases, prevent the import and export of our products to certain countries altogether. Any change in import and export regulations or related legislation, shift in approach to the enforcement or scope of existing regulations, or change in the countries, persons or technologies impacted by such regulations, could result in decreased use of our products by, or in our

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decreased ability to export or sell our products to, existing or potential customers with international operations. Failure to comply with these and similar laws on a timely basis, or at all, decreased use of our products or any limitation on our ability to develop, export or sell our products would adversely affect our business, financial condition and operating results.

Our product or manufacturing standards could also be impacted by new or revised environmental rules and regulations or other social initiatives. For instance, the SEC adopted new disclosure requirements in 2012 relating to the sourcing of certain minerals from the Democratic Republic of Congo and certain other adjoining countries. Those rules, which required reporting for the first time in calendar 2014, could adversely affect our costs, the availability of minerals used in our products and our relationships with customers and suppliers.

The Federal Communications Commission (“FCC”) has jurisdiction over the entire U.S. communications industry and, as a result, our products and our U.S. customers are subject to FCC rules and regulations. Current and future FCC regulations, including regulations on net neutrality or generally affecting communications services, our products or our customers’ businesses could negatively affect our business. In addition, international regulatory standards could impair our ability to develop products for international customers in the future. Moreover, many jurisdictions are evaluating or implementing regulations relating to cybersecurity, privacy and data protection, which can affect the market and requirements for networking and communications equipment. For example, in April 2016, the European Parliament approved the General Data Protection Regulation (the “GDPR”), which came into effect in May 2018 and supersedes current EU data protection regulations. The GDPR imposes stringent data handling requirements on companies that receive or process personal data of residents of the EU, and non-compliance with the GDPR could result in significant penalties, including data protection audits and heavy fines. Any failure to obtain the required approvals or comply with such laws and regulations could harm our business and operating results.

Natural disasters, terrorist attacks or other catastrophic events could harm our operations.

Our headquarters and the majority of our infrastructure, including our PIC fabrication manufacturing facility, are located in Northern California, an area that is susceptible to earthquakes, floods and other natural disasters. Further, a terrorist attack aimed at Northern California or at the United States energy or telecommunications infrastructure could hinder or delay the development and sale of our products. In the event that an earthquake, terrorist attack or other man-made or natural catastrophe were to destroy any part of our facilities, or certain of our contract manufacturers’ facilities, destroy or disrupt vital infrastructure systems or interrupt our operations for any extended period of time, our business, financial condition and operating results would be harmed.

Security incidents, such as data breaches and cyber-attacks, could compromise our intellectual property and proprietary or confidential information and cause significant damage to our business and reputation.

In the ordinary course of our business, we maintain sensitive data on our networks, including data related to our intellectual property and data related to our business, customers and business partners, which is considered proprietary or confidential information. We believe that companies in the technology industry have been increasingly subject to a wide variety of security incidents, cyber-attacks and other attempts to gain unauthorized access. While the secure maintenance of this information is critical to our business and reputation, our network and storage applications may be subject to unauthorized access by hackers or breached due to operator error, malfeasance or other system disruptions. It may be difficult to anticipate or immediately detect such security incidents or data breaches and the damage caused as a result. Accordingly, a data breach, cyber-attack, or unauthorized access or disclosure of our information, could compromise our intellectual property and reveal proprietary or confidential business information. In addition, these security incidents could also cause us to incur significant remediation costs and expenses, disrupt key business operations, subject us to liability and divert attention of management and key information technology resources, any of which could cause significant harm to our business and reputation.

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Risks Related to the Notes

If we fail to consummate our acquisition of Coriant, we may redeem the notes at a redemption price that may be less than the value of your notes.

If the Acquisition is not consummated for any reason by January 23, 2019, or if the Purchase Agreement is terminated for any reason (other than as a result of consummation of the Acquisition), we may redeem all, but not less than all, of the outstanding notes for cash on a redemption date to occur on or prior to April 23, 2019. The redemption price for each $1,000 principal amount of notes will equal the sum of (i) $1,020, (ii) accrued and unpaid interest on such notes to, but excluding, the redemption date and (iii) 75% of the excess, if any, of the redemption conversion value (as defined under “Description of Notes—Unwind Redemption”) over the initial conversion value (as defined in such section). Neither the redemption price nor the consideration you would receive if you choose to convert your notes in lieu of redemption will otherwise include any compensation for interest payments you would have received if such notes had not been redeemed or converted or any lost time value of your notes. As a result, if your notes are redeemed, you may not obtain your expected return on the notes and may not be able to reinvest the proceeds from a redemption in an investment that results in a comparable return.

This offering is not contingent upon consummation of the Acquisition or the terms of the Acquisition, and our stock price could be adversely affected by any failure or delay in completing the Acquisition, as well as any failure to complete the Acquisition on the terms currently contemplated.

We expect to use a portion of the net proceeds from this offering to finance our pending Acquisition. Completion of this offering is not contingent upon consummation of the Acquisition or the terms of the Acquisition, even if those terms vary materially from what we currently expect.

We have not identified any specific use for the portion of net proceeds from this offering that we intend to use to finance the pending Acquisition in the event that the Acquisition is not consummated. In the event the Acquisition is not consummated, we plan to use all of the net proceeds from this offering for general corporate purposes and to pay transaction fees. This means that our management would have broad discretion in the application of all of the net proceeds from this offering. Because of the number and variability of factors that would determine our use of the net proceeds from this offering if the Acquisition does not occur, we cannot provide any assurance that the return on our use of such net proceeds would be equivalent to the return on investment we currently anticipate from the Acquisition. If we do not invest or apply such net proceeds from this offering in ways that enhance our financial returns, and if we elect not to redeem the notes if the Acquisition does not occur, the trading price of the notes and our common stock could decline.

In the event we do not complete the Acquisition on the terms or on the timeframe currently contemplated, or if we do not complete it at all and we elect not to redeem the notes, the trading price of the notes and our common stock could also decline. Such a decline in market price of the notes or our common stock could occur regardless of the reason for the delay or failure to complete the Acquisition.

Although the notes are referred to as convertible senior notes, they will be effectively subordinated to any of our secured debt and any liabilities of our subsidiaries.

The notes will rank senior in right of payment to any of our indebtedness that is expressly subordinated in right of payment to the notes; equal in right of payment to any of our liabilities that are not so subordinated; effectively junior in right of payment to any of our secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness and other liabilities (including trade payables) of our subsidiaries. In the event of our bankruptcy, liquidation, reorganization or other winding up, our assets that secure debt ranking senior in right of payment to the notes will be available to pay obligations on the notes only after the secured debt has been repaid in full from these assets, and the assets of our subsidiaries will

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be available to pay obligations on the notes only after all claims senior to the notes have been repaid in full. There may not be sufficient assets remaining to pay amounts due on any or all of the notes then outstanding. The indenture governing the notes does not prohibit us from incurring additional senior debt or secured debt, nor does it prohibit any of our current or future subsidiaries from incurring additional liabilities.

As of June 30, 2018, we had no outstanding indebtedness for borrowed money (excluding intercompany debt). Our subsidiaries had $68.0 million of other liabilities (including trade payables but excluding intercompany obligations and liabilities of a type not required to be reflected on a balance sheet of such subsidiaries in accordance with U.S. GAAP). After giving effect to the issuance of the notes (assuming no exercise of the underwriter’s overallotment option to purchase additional notes, our indebtedness for borrowed money (excluding intercompany debt) would have been $275.0 million.

The notes are our obligations exclusively and a portion of our operations are conducted through, and a portion of our consolidated assets are held by, our subsidiaries.

The notes are our obligations exclusively and are not guaranteed by any of our subsidiaries. A portion of our consolidated assets are held by our subsidiaries. Accordingly, our ability to service our debt, including the notes, depends on the results of operations and cash flows of the consolidated company including our subsidiaries and upon the ability of such subsidiaries to provide us with cash, whether in the form of dividends, loans or otherwise, to pay amounts due on our obligations, including the notes. Our subsidiaries are separate and distinct legal entities and have no obligation, contingent or otherwise, to make payments on the notes or to make any funds available for that purpose. In addition, dividends, loans or other distributions to us from such subsidiaries may be subject to contractual and other restrictions and are subject to other business considerations.

Recent and future regulatory actions and other events may adversely affect the trading price and liquidity of the notes.

We expect that many investors in, and potential purchasers of, the notes will employ, or seek to employ, a convertible arbitrage strategy with respect to the notes. Investors would typically implement such a strategy by selling short the common stock underlying the notes and dynamically adjusting their short position while continuing to hold the notes. Investors may also implement this type of strategy by entering into swaps on our common stock in lieu of or in addition to short selling the common stock.

The SEC and other regulatory and self-regulatory authorities have implemented various rules and taken certain actions, and may in the future adopt additional rules and take other actions, that may impact those engaging in short selling activity involving equity securities (including our common stock). Such rules and actions include Rule 201 of SEC Regulation SHO, the adoption by the Financial Industry Regulatory Authority, Inc. and the national securities exchanges of a “Limit Up-Limit Down” program, the imposition of market-wide circuit breakers that halt trading of securities for certain periods following specific market declines, and the implementation of certain regulatory reforms required by the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010. Any governmental or regulatory action that restricts the ability of investors in, or potential purchasers of, the notes to effect short sales of our common stock, borrow our common stock or enter into swaps on our common stock could adversely affect the trading price and the liquidity of the notes.

Volatility in the market price and trading volume of our common stock could adversely impact the trading price of the notes.

The stock market in recent years has experienced significant price and volume fluctuations that have often been unrelated to the operating performance of companies. The market price of our common stock could fluctuate significantly for many reasons, including in response to the risks described in this section, elsewhere in this prospectus supplement or the documents incorporated by reference in this prospectus supplement or for reasons unrelated to our operations, such as reports by industry analysts, investor perceptions or negative

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announcements by our customers, competitors or suppliers regarding their own performance, as well as industry conditions and general financial, economic and political instability. A decrease in the market price of our common stock would likely adversely impact the trading price of the notes. The price of our common stock could also be affected by possible sales of our common stock by investors who view the notes as a more attractive means of equity participation in us and by hedging or arbitrage trading activity that we expect to develop involving our common stock. This trading activity could, in turn, affect the trading prices of the notes.

We may not have sufficient cash flow from our business to service our indebtedness or pay our indebtedness.

Our ability to make scheduled payments of the principal of, to pay interest on or to refinance our indebtedness, depends on our future performance, which is subject to economic, financial, competitive and other factors beyond our control. Our business may not continue to generate cash flow from operations in the future sufficient to service our indebtedness and make necessary capital expenditures. If we are unable to generate adequate cash flow, we may be required to adopt one or more alternatives, such as selling assets, restructuring indebtedness or obtaining additional equity capital on terms that may be onerous or highly dilutive. Our ability to refinance our indebtedness will depend on the capital markets and our financial condition at such time. We may not be able to engage in any of these activities or engage in these activities on desirable terms, which could result in a default under our debt obligations, which could, in turn, adversely affect our business, financial condition and operating results.

We may still incur substantially more debt or take other actions, which would intensify the risks discussed above.

We and our subsidiaries may incur substantial additional debt in the future, some of which may be secured debt. We will not be restricted under the terms of the indenture governing the notes from incurring additional debt, securing existing or future debt, recapitalizing our debt or taking a number of other actions that are not limited by the terms of the indenture governing the notes that could have the effect of diminishing our ability to make payments on the notes when due.

We may not have the ability to raise the funds necessary to settle conversions of the notes or to repurchase the notes upon a fundamental change, and our future debt may contain limitations on our ability to repurchase the notes.

Holders of the notes will have the right to require us to repurchase their notes upon the occurrence of a fundamental change at a repurchase price equal to 100% of their principal amount, plus accrued and unpaid interest, if any, as described under “Description of Notes—Fundamental Change Permits Holders to Require Us to Repurchase Notes.” In addition, upon conversion of the notes, unless we elect to deliver solely shares of our common stock to settle such conversion (other than paying cash in lieu of delivering any fractional share), we will be required to make cash payments in respect of the notes being converted as described in under “Description of Notes—Conversion Rights—Settlement upon Conversion.” However, we may not have enough available cash or be able to obtain financing at the time we are required to make repurchases of notes surrendered therefor or notes being converted. We may be required to use funds that are domiciled in foreign tax jurisdictions in order to make the cash payments upon any conversion or repurchase of the notes, which may result in tax liabilities and other additional costs.

In addition, our ability to repurchase the notes or to pay cash upon conversion of the notes may be limited by law, by regulatory authority or by agreements governing our future indebtedness. Our failure to repurchase or pay cash amounts due upon conversion of the notes as required would constitute a default under the indenture. A default under the indenture or the fundamental change itself could also lead to a default under agreements governing our future indebtedness. Moreover, the occurrence of a fundamental change under the indenture may constitute an event of default under agreements governing our future indebtedness. If the payment of the related

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indebtedness were to be accelerated after any applicable notice or grace periods, we may not have sufficient funds to repay the indebtedness and repurchase the notes or to pay cash upon conversion of the notes.

Redemption may adversely affect your return on the notes.

Except as described under “Description of Notes—Unwind Redemption,” we may not redeem the notes prior to September 5, 2021. We may redeem for cash all (but not less than all) of the notes, at our option, on or after September 5, 2021, if the last reported price of our common stock has been at least 130% of the conversion price for the notes then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending on, and including, the trading day immediately preceding the date on which we provide notice of redemption at a redemption price equal to 100% of the principal amount of the notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. As a result, we may choose to redeem the notes at times when prevailing interest rates are relatively low. As a result, you may not be able to reinvest the proceeds you receive from the redemption in a comparable security at an effective interest rate as high as the interest rate on your notes being redeemed. See “Description of Notes—Optional Redemption.”

The conditional conversion feature of the notes, if triggered, may adversely affect our financial condition and operating results.

In the event the conditional conversion feature of the notes is triggered, holders of notes will be entitled to convert the notes at any time during specified periods at their option. See “Description of Notes—Conversion Rights.” If one or more holders elect to convert their notes, unless we elect to satisfy our conversion obligation by delivering solely shares of our common stock (other than paying cash in lieu of delivering any fractional share), we would be required to settle a portion or all of our conversion obligation through the payment of cash, which could adversely affect our liquidity. In addition, even if holders do not elect to convert their notes, we could be required under applicable accounting rules to reclassify all or a portion of the outstanding principal of the notes as a current rather than long-term liability, which would result in a material reduction of our net working capital.

The accounting method for convertible debt securities that may be settled in cash, such as the notes, is the subject of recent changes that could have a material effect on our reported financial results.

Under Accounting Standards Codification 470-20, Debt with Conversion and Other Options, which we refer to as ASC 470-20, an entity must separately account for the liability and equity components of certain convertible debt instruments (such as the notes) that may be settled entirely or partially in cash upon conversion in a manner that reflects the issuer’s economic interest cost. The effect of ASC 470-20 on the accounting for the notes is that the equity component is required to be included in the additional paid-in capital section of stockholders’ equity on our consolidated balance sheet, and the value of the equity component is treated as original issue discount for purposes of accounting for the debt component of the notes. As a result, we will be required to record a greater amount of non-cash interest expense in current periods presented as a result of the amortization of the discounted carrying value of the notes to their respective face amounts over their respective terms. We will report lower net income in our financial results because ASC 470-20 will require interest to include both the current period’s amortization of the debt discount and the instrument’s coupon interest, which could adversely affect our financial results, the trading price of our common stock and the trading price of the notes.

In addition, under certain circumstances, convertible debt instruments (such as the notes) that may be settled entirely or partly in cash are currently accounted for utilizing the treasury stock method, the effect of which is that any shares issuable upon conversion of the notes are not included in the calculation of diluted earnings per share except to the extent that the conversion value of the notes exceeds their respective principal amounts. Under the treasury stock method, for diluted earnings per share purposes, the transaction is accounted for as if the

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number of shares of common stock that would be necessary to settle such excess, if we elected to settle such excess in shares, are issued. We cannot be sure that the accounting standards in the future will continue to permit the use of the treasury stock method. If we are unable to use the treasury stock method in accounting for the shares issuable upon conversion of the notes, then our diluted earnings per share would be adversely affected.

Future sales of our common stock or the issuance of other equity-related securities could lower the market price for our common stock and adversely impact the trading price of the notes.

In the future, we may sell additional shares of our common stock or other equity-related securities to raise capital or issue common stock or equity-related securities to make acquisitions. In particular, a portion of the consideration payable by us in the Acquisition pursuant to the Purchase Agreement consists of approximately 21.0 million shares of our common stock, or approximately 12.0% of the outstanding shares of our common stock as of August 24, 2018 (subject to reduction in certain circumstances and after giving effect to the issuance of shares of our common stock in the Acquisition as if the issuance occurred on August 24, 2018). Those shares will be issued to Oaktree Optical Holdings, L.P., and will be subject to a lock-up agreement with the underwriter of this offering for a period of 60 days following the date of this prospectus supplement. In addition 50% of those shares are subject to lock-up arrangements with us for a period of six months following consummation of the Acquisition and the remaining 50% of those shares are subject to lock-up arrangements with us for a period of 12 months following consummation of the Acquisition, in each case pursuant to the terms of the Purchase Agreement. The lock-up arrangements relating to such shares are subject to certain important exceptions, and may be waived by the underwriter of this offering in its sole discretion or by us in our sole discretion, as applicable. In addition, a substantial number of shares of our common stock are reserved for issuance upon the exercise of stock options, the vesting of restricted stock, restricted stock units and performance shares pursuant to our employee benefit plans, for purchase by employees under our employee stock purchase plan, and upon conversion of the notes offered hereby. We cannot predict the size of future issuances or the effect, if any, that they may have on the market price for our common stock. The issuance and sale of substantial amounts of common stock, or the perception that such issuances and sales may occur, could adversely affect the trading price of the notes and the market price of our common stock and impair our ability to raise capital through the sale of additional equity or equity-related securities.

Holders of notes will not be entitled to any rights with respect to our common stock, but they will be subject to all changes made with respect to them to the extent our conversion obligation includes shares of our common stock.

Holders of notes will not be entitled to any rights with respect to our common stock (including, without limitation, voting rights and rights to receive any dividends or other distributions on our common stock) prior to the conversion date relating to such notes (if we have elected to settle the relevant conversion by delivering solely shares of our common stock (other than paying cash in lieu of delivering any fractional share)) or the last trading day of the relevant observation period (if we elect to pay and deliver, as the case may be, a combination of cash and shares of our common stock in respect of the relevant conversion), but holders of notes will be subject to all changes affecting our common stock. For example, if an amendment is proposed to our certificate of incorporation or bylaws requiring stockholder approval and the record date for determining the stockholders of record entitled to vote on the amendment occurs prior to the conversion date related to a holder’s conversion of its notes (if we have elected to settle the relevant conversion by delivering solely shares of our common stock (other than paying cash in lieu of delivering any fractional share)) or the last trading day of the relevant observation period (if we elect to pay and deliver, as the case may be, a combination of cash and shares of our common stock in respect of the relevant conversion), such holder will not be entitled to vote on the amendment, although such holder will nevertheless be subject to any changes affecting our common stock.

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The conditional conversion feature of the notes could result in your receiving less than the value of our common stock into which the notes would otherwise be convertible.

Prior to the close of business on the business day immediately preceding June 1, 2024, you may convert your notes only if specified conditions are met. If the specific conditions for conversion are not met, you will not be able to convert your notes, and you may not be able to receive the value of the cash, common stock or a combination of cash and common stock, as applicable, into which the notes would otherwise be convertible.

Upon conversion of the notes, you may receive less valuable consideration than expected because the value of our common stock may decline after you exercise your conversion right but before we settle our conversion obligation.

Under the notes, a converting holder will be exposed to fluctuations in the value of our common stock during the period from the date such holder surrenders notes for conversion until the date we settle our conversion obligation.

Upon conversion of the notes, we have the option to pay or deliver, as the case may be, cash, shares of our common stock, or a combination of cash and shares of our common stock. If we elect to satisfy our conversion obligation in cash or a combination of cash and shares of our common stock, the amount of consideration that you will receive upon conversion of your notes will be determined by reference to the volume-weighted average prices of our common stock for each trading day in a 40 trading-day observation period. As described under “Description of Notes—Settlement upon Conversion,” this period would be (i) subject to clause (ii), if the relevant conversion date occurs prior to June 1, 2024, the 40 consecutive trading day period beginning on, and including, the second trading day after such conversion date; (ii) if the relevant conversion date occurs on or after the date of our issuance of a notice of redemption as described under “Description of Notes—Optional Redemption” or “Description of Notes—Unwind Redemption” and prior to the relevant redemption date, the 40 consecutive trading days beginning on, and including, the 41st scheduled trading day immediately preceding such redemption date; and (iii) subject to clause (ii), if the relevant conversion date occurs on or after June 1, 2024, the 40 consecutive trading days beginning on, and including, the 41st scheduled trading day immediately preceding September 1, 2024. Accordingly, if the price of our common stock decreases during this period, the amount and/or value of consideration you receive will be adversely affected. In addition, if the market price of our common stock at the end of such period is below the average of the volume-weighted average price of our common stock during such period, the value of any shares of our common stock that you will receive in satisfaction of our conversion obligation will be less than the value used to determine the number of shares that you will receive.

If we elect to satisfy our conversion obligation solely in shares of our common stock upon conversion of the notes, we will be required to deliver the shares of our common stock, together with cash for any fractional share, on the second business day following the relevant conversion date (provided that, with respect to any conversion date occurring after June 1, 2024, settlement will occur on the maturity date of the notes). Accordingly, if the price of our common stock decreases during this period, the value of the shares that you receive will be adversely affected and would be less than the conversion value of the notes on the conversion date.

The notes are not protected by restrictive covenants.

The indenture governing the notes does not contain any financial or operating covenants or restrictions on the payments of dividends, the incurrence of indebtedness or the issuance or repurchase of securities by us or any of our subsidiaries. The indenture contains no covenants or other provisions to afford protection to holders of the notes in the event of a fundamental change or other corporate transaction involving us except to the extent described under “Description of Notes—Fundamental Change Permits Holders to Require Us to Repurchase Notes,” “Description of Notes—Conversion Rights—Increase in Conversion Rate upon Conversion upon a Make-Whole Fundamental Change or Notice of Optional Redemption” and “Description of Notes—Consolidation, Merger and Sale of Assets.”

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The increase in the conversion rate for notes converted in connection with a make-whole fundamental change or redemption may not adequately compensate you for any lost value of your notes as a result of such transaction.

If a make-whole fundamental change or redemption occurs prior to the maturity date, under certain circumstances, we will increase the conversion rate by a number of additional shares of our common stock for notes converted in connection with such make-whole fundamental change or redemption, as applicable. The increase in the conversion rate will be determined based on the date on which the specified corporate transaction becomes effective or the date of the redemption notice, as the case may be, and the price paid (or deemed to be paid) per share of our common stock in such transaction, as described below under “Description of Notes—Conversion Rights—Increase in Conversion Rate upon Conversion upon a Make-Whole Fundamental Change or Notice of Optional Redemption.” The increase in the conversion rate for notes converted in connection with a make-whole fundamental change or redemption, as applicable, may not adequately compensate you for any lost value of your notes as a result of such transaction or in connection with the redemption, as applicable. In addition, if the price of our common stock in the transaction or in connection with the redemption is greater than $         per share or less than $         per share (subject to adjustment), no additional shares will be added to the conversion rate. Moreover, in no event will the conversion rate per $1,000 principal amount of notes as a result of this adjustment exceed                  shares of common stock, subject to adjustment in the same manner as the conversion rate as set forth under “Description of Notes—Conversion Rights—Conversion Rate Adjustments.”

Our obligation to increase the conversion rate for notes converted in connection with a make-whole fundamental change or redemption could be considered a penalty, in which case the enforceability thereof would be subject to general principles of reasonableness and equitable remedies.

Upon any optional redemption of the notes or any conversion of the notes in connection with a related redemption notice, the cash comprising the redemption price, in the case of an optional redemption, or the applicable conversion rate, in the case of a conversion in connection with a redemption notice, as applicable, may not fully compensate you for future interest payments or lost time value of your notes.

On or after September 5, 2021, we may optionally redeem for cash all (but not less than all) of the notes, at our option, if the last reported sale price of our common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), during any 30 consecutive trading day period (including the last trading day of such period) ending on, and including, the trading day immediately preceding the date on which we provide notice of redemption at a redemption price equal to 100% of the principal amount of the notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. If we call the notes for optional redemption, you may convert all or any portion of your notes at any time prior to the close of business on the scheduled trading day immediately preceding the redemption date. Upon such redemption or conversion, the cash comprising the redemption price, in the case of an optional redemption, or the applicable conversion rate, in the case of a conversion in connection with a related redemption notice, in either case, may not fully compensate you for any future interest payments that you would have otherwise received or any other lost time value of your notes. See “Description of Notes—Optional Redemption.”

The conversion rate of the notes may not be adjusted for all dilutive events.

The conversion rate of the notes is subject to adjustment for certain events, including, but not limited to, the issuance of certain stock dividends on our common stock, the issuance of certain rights or warrants, subdivisions, combinations, distributions of capital stock, indebtedness, or assets, cash dividends and certain issuer tender or exchange offers as described under “Description of Notes—Conversion Rights—Conversion Rate Adjustments.” However, the conversion rate will not be adjusted for other events, such as a third-party tender or exchange offer or an issuance of common stock for cash, that may adversely affect the trading price of the notes or our common stock. An event that adversely affects the value of the notes may occur, and that event may not result in an adjustment to the conversion rate.

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Provisions in the indenture for the notes may deter or prevent a business combination that may be favorable to you.

If a fundamental change occurs prior to the maturity date of the notes, holders of the notes will have the right, at their option, to require us to repurchase all or a portion of their notes. In addition, if a make-whole fundamental change occurs prior to the maturity date of the notes, we will in some cases be required to increase the conversion rate for a holder that elects to convert its notes in connection with such fundamental change. Furthermore, the indenture for the notes prohibits us from engaging in certain mergers or acquisitions unless, among other things, the surviving entity assumes our obligations under the notes. These and other provisions in the indenture could deter or prevent a third party from acquiring us even when the acquisition may be favorable to you.

Some significant restructuring transactions may not constitute a fundamental change, in which case we would not be obligated to offer to repurchase the notes.

Upon the occurrence of a fundamental change, you have the right to require us to repurchase your notes. However, the fundamental change provisions will not afford protection to holders of notes in the event of other transactions that could adversely affect the notes. For example, transactions such as leveraged recapitalizations, refinancings, restructurings, or acquisitions initiated by us may not constitute a fundamental change requiring us to repurchase the notes. In the event of any such transaction, the holders would not have the right to require us to repurchase the notes, even though each of these transactions could increase the amount of our indebtedness, or otherwise adversely affect our capital structure or any credit ratings, thereby adversely affecting the holders of notes.

We cannot assure you that an active trading market will develop for the notes.

Prior to this offering, there has been no trading market for the notes, and we do not intend to apply to list the notes on any securities exchange or to arrange for quotation on any automated dealer quotation system. We have been informed by the underwriter that it intends to make a market in the notes after the offering is completed. However, the underwriter may cease its market-making at any time without notice. In addition, the liquidity of the trading market in the notes, and the market price quoted for the notes, may be adversely affected by changes in the overall market for this type of security and by changes in our financial performance or prospects or in the prospects for companies in our industry generally. As a result, we cannot assure you that an active trading market will develop for the notes. If an active trading market does not develop or is not maintained, the market price and liquidity of the notes may be adversely affected. In that case you may not be able to sell your notes at a particular time or you may not be able to sell your notes at a favorable price.

Any adverse rating of the notes may cause their trading price to fall.

We do not intend to seek a rating on the notes. However, if a rating service were to rate the notes and if such rating service were to lower its rating on the notes below the rating initially assigned to the notes or otherwise announces its intention to put the notes on credit watch, the trading price of the notes could decline.

You may be subject to tax if we make or fail to make certain adjustments to the conversion rate of the notes even though you do not receive a corresponding cash distribution.

The conversion rate of the notes is subject to adjustment in certain circumstances, including the payment of cash dividends. If the conversion rate is adjusted as a result of a distribution that is taxable to our common stockholders, such as a cash dividend, you may be deemed to have received a dividend subject to U.S. federal income tax without the receipt of any cash. In addition, a failure to adjust (or to adjust adequately) the conversion rate after an event that increases your proportionate interest in us could be treated as a deemed taxable dividend to you. If a make-whole fundamental change or redemption, as the case may be, occurs on or prior to the maturity

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date of the notes, under some circumstances, we will increase the conversion rate for notes converted in connection with the make-whole fundamental change or during the related redemption period. Such increase may also be treated as a distribution subject to U.S. federal income tax as a dividend. See “Material U.S. Federal Income Tax Considerations.” If you are a non-U.S. holder (as defined under “Material U.S. Federal Income Tax Considerations”), any deemed dividend would generally be subject to U.S. federal withholding tax at a 30% rate, or such lower rate as may be specified by an applicable treaty, which may be set off against subsequent payments on the notes (including upon conversion, repayment or maturity), or in some circumstances from any payments on our common stock or from sales proceeds subsequently paid or credited to you, or from your other funds or assets. See “Material U.S. Federal Income Tax Considerations.”

The capped call transactions may affect the value of the notes and our common stock.

In connection with the pricing of the notes, we expect to enter into capped call transactions with one or more of the underwriter or its affiliates and/or other financial institutions (the “option counterparties”). The capped call transactions are expected generally to reduce or offset the potential dilution upon conversion of the notes and/or offset any cash payments we are required to make in excess of the principal amount of converted notes, as the case may be, with such reduction and/or offset subject to a cap. If the underwriter exercises its option to purchase additional notes, we expect to enter into additional capped call transactions with the option counterparties.

In connection with establishing their initial hedges of the capped call transactions, the option counterparties or their respective affiliates expect to enter into various derivative transactions with respect to our common stock concurrently with or shortly after the pricing of the notes. This activity could increase (or reduce the size of any decrease in) the market price of our common stock or the notes at that time.

In addition, the option counterparties or their respective affiliates may modify their hedge positions by entering into or unwinding various derivatives with respect to our common stock and/or purchasing or selling our common stock or other securities of ours in secondary market transactions following the pricing of the notes and prior to the maturity of the notes (and are likely to do so during any observation period related to a conversion of notes). This activity could also cause or avoid an increase or a decrease in the market price of our common stock or the notes, which could affect your ability to convert the notes and, to the extent the activity occurs during any observation period related to a conversion of notes, it could affect the number of shares and value of the consideration that you will receive upon conversion of the notes.

In addition, if any such capped call transactions fail to become effective, whether or not this offering of notes is completed, the option counterparties or their respective affiliates may unwind their hedge positions with respect to our common stock, which could adversely affect the value of our common stock and, if the notes have been issued, the value of the notes.

We are subject to counterparty risk with respect to the capped call transactions.

The option counterparties to the capped call transactions are financial institutions, and we will be subject to the risk that any or all of them might default under the capped call transactions. Our exposure to the credit risk of the counterparties will not be secured by any collateral. Past global economic conditions have resulted in the actual or perceived failure or financial difficulties of many financial institutions. If an option counterparty becomes subject to insolvency proceedings, we will become an unsecured creditor in those proceedings with a claim equal to our exposure at the time under the capped call transactions with such option counterparty. Our exposure will depend on many factors but, generally, an increase in our exposure will be correlated to an increase in the market price and in the volatility of our common stock. In addition, upon a default by an option counterparty, we may suffer adverse tax consequences and more dilution than we currently anticipate with respect to our common stock. We can provide no assurance as to the financial stability or viability of the option counterparties.

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Risks Related to Our Common Stock

The trading price of our common stock has been volatile and is likely to be volatile in the future. This volatility may affect the price at which you could sell the common stock you receive upon conversion of your notes, if any, and the sale of substantial amounts of our common stock could adversely affect the price of our common stock and the value of your notes.

The trading prices of our common stock and the securities of other technology companies have been and may continue to be highly volatile. Factors affecting the trading price of our common stock include:

In addition, if the market for technology stocks or the stock market in general experiences loss of investor confidence, the trading price of our common stock could decline for reasons unrelated to our business, financial condition or operating results. The trading price of our common stock might also decline in reaction to events that affect other companies in our industry even if these events do not directly affect us. Each of these factors, among others, could harm the value of the common stock you receive upon the conversion of your notes, if any, and the value of your notes. Some companies that have had volatile market prices for their securities have had securities class action lawsuits filed against them. If a suit were filed against us, regardless of its merits or outcome, it could result in substantial costs and divert management’s attention and resources.

As of August 24, 2018, we had outstanding approximately 154.0 million shares of our common stock. In addition, as of August 24, 2018, we had options outstanding to purchase approximately 1.1 million shares of our common stock (all of which were exercisable as of that date) and we also had approximately 8.8 million shares underlying outstanding restricted stock units and performance stock units. Further, a portion of the consideration payable by us in the Acquisition pursuant to the Purchase Agreement consists of approximately 21.0 million shares of our common stock, or approximately 12.0% of the outstanding shares of our common stock as of August 24, 2018 (subject to reduction in certain circumstances and after giving effect to the issuance of shares of our common stock in the Acquisition as if the issuance occurred on August 24, 2018). Those shares will be issued to Oaktree Optical Holdings, L.P., and will be subject to a lock-up agreement with the underwriter of this offering for a period of 60 days following the date of this prospectus supplement. In addition, 50% of those shares are subject to lock-up arrangements with us for a period of six months following consummation of the Acquisition and the remaining 50% of those shares are subject to lock-up arrangements with us for a period of 12 months following consummation of the Acquisition, in each case pursuant to the terms of the Purchase Agreement. The lock-up arrangements relating to such shares are subject to certain important exceptions, and may be waived by the underwriter of this offering in its sole discretion or by us in our sole discretion, as applicable. We and certain of our directors and officers have also entered into lock-up agreements with the underwriter of this offering with respect to shares of our common stock, and certain other securities convertible into, or exchangeable or exercisable for, shares of our common stock. Such lock-up agreements are subject to certain important exceptions, and may also be waived by the underwriter, in whole or in part, in its sole discretion. See “Underwriter”. The sale or the availability for sale of a large number of shares of our common stock in the public market could cause the price of our common stock, and the value of your notes, to decline.

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Anti-takeover provisions in our charter documents and Delaware law could discourage delay or prevent a change in control of our company and may affect the trading price of our common stock and the value of the notes.

We are a Delaware corporation and the anti-takeover provisions of the Delaware General Corporation Law, which apply to us, may discourage, delay or prevent a change in control by prohibiting us from engaging in a business combination with an interested stockholder for a period of three years after the person becomes an interested stockholder, even if a change of control would be beneficial to our existing stockholders. In addition, our amended and restated certificate of incorporation and amended and restated bylaws may discourage, delay or prevent a change in our management or control over us that stockholders may consider favorable. Our amended and restated certificate of incorporation and amended and restated bylaws:

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FORWARD-LOOKING STATEMENTS

This prospectus supplement contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements may also be made in our documents incorporated or deemed to be incorporated by reference in this prospectus supplement. Such forward-looking statements include our expectations regarding revenue, gross margin, operating expenses, cash flows and other financial items; any statements of the plans, strategies and objectives of management for future operations and personnel; factors that may affect our operating results; our ability to leverage our vertically-integrated manufacturing infrastructure; costs and expectations regarding our restructuring plan; anticipated customer activity; statements concerning new products or services, including new product features and delivery dates; statements related to capital expenditures; statements related to liquidity; statements related to future economic conditions, performance, market growth or our sales cycle; statements related to the pending Acquisition, including conditions to the closing of the Acquisition and the potential impact on our future combined operating results; statements related to the notes; statements related to the impact of tax regulations; statements related to the effects of litigation on our financial position, results of operations or cash flows; statements related to the new revenue recognition standard; statements as to industry trends and other matters that do not relate strictly to historical facts or statements of assumptions underlying any of the foregoing. These statements are often identified by the use of words such as “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” or “will,” and similar expressions or variations. These statements are based on the beliefs and assumptions of our management based on information currently available to management. Such forward-looking statements are subject to risks, uncertainties and other factors that could cause actual results and the timing of certain events to differ materially from future results expressed or implied by such forward-looking statements. Factors that could cause or contribute to such differences include, but are not limited to, those identified below, and those discussed in the section titled “Risk Factors” beginning on page S-15 of this prospectus supplement and the other risks, uncertainties, assumptions and factors specified in our Annual Report on Form 10-K for the year ended December 30, 2017, our Quarterly Report on Form 10-Q for the fiscal quarter ended June 30, 2018 and in other filings we make with the SEC from time to time. Such forward-looking statements speak only as of the date of this report. We disclaim any obligation to update any forward-looking statements to reflect events or circumstances after the date of such statements.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $         million (or approximately $         million if the underwriter exercises its overallotment option to purchase additional notes in full), after deducting the underwriters’ discount and estimated offering expenses payable by us.

We expect to enter into capped call transactions with one or more option counterparties. We intend to use approximately $         million of the net proceeds from this offering to pay the cost of the capped call transactions. We intend to use the remaining net proceeds to fund the cash portion of the purchase price of the Acquisition, including fees and expenses relating thereto and general corporate purposes. This offering is not contingent on the consummation of the Acquisition.

If the underwriter exercises its overallotment option to purchase additional notes, we expect to use a portion of the net proceeds from the sale of the additional notes to enter into additional capped call transactions with the option counterparties and the remainder for general corporate purposes.

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PRICE RANGE OF COMMON STOCK

Our common stock is listed on the Nasdaq Global Select Market under the symbol “INFN.” The following table sets forth, for the periods indicated, the high and low closing sales prices for our common stock as reported by Bloomberg, L.P.

As of August 24, 2018, there were approximately 92 registered holders of record of our common stock. A substantially greater number of holders of our common stock are “street name” or beneficial holders, whose shares are held of record by banks, brokers and other financial institutions.

The last reported sale price of our common stock on the Nasdaq Global Select Market on September 4, 2018 was $8.69.

DIVIDEND POLICY

We have not paid any cash dividends on our common stock and do not intend to pay cash dividends on our common stock in the near future.

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CAPITALIZATION

The following table sets forth our cash, cash equivalents, short-term investments and capitalization as of June 30, 2018:

You should read this table in conjunction with “Use of Proceeds” as well as our “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements, including the related notes, contained in our Annual Report on Form 10-K for the fiscal year ended December 30, 2017 and our Quarterly Report on Form 10-Q for the quarter ended June 30, 2018, incorporated by reference in this prospectus supplement.

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INFINERA CORPORATION

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

The following sets forth certain unaudited pro forma condensed combined financial information giving effect to the planned acquisition of Telecom Holding Parent LLC, a Delaware limited liability company and subsidiaries (collectively, “Coriant”) by Infinera Corporation, a Delaware corporation (hereinafter referred to as “Infinera,” “the Company,” “we,” “our,” “us” and similar terms unless the context indicates otherwise). The following unaudited pro forma condensed combined financial information presents the historical condensed combined financial statements of Infinera and Coriant after giving effect to Infinera’s acquisition of Coriant (the “Acquisition”) and the offering of the notes (the “Offering”) based on the assumptions, reclassifications and adjustments described in the accompanying notes to the unaudited pro forma condensed combined financial information. We refer to the Acquisition and the Offering transactions collectively as the “Transactions.”

The unaudited pro forma condensed combined balance sheet as of June 30, 2018 gives effect to the planned Transactions as if they had been consummated on June 30, 2018. The unaudited pro forma condensed combined statement of operations for the year ended December 30, 2017 gives effect to the Transactions as if they had been consummated on January 1, 2017, the beginning of Infinera’s most recently completed fiscal year. As Coriant is a privately held company and has not adopted ASC 606, Revenue from Contracts with Customers or Subtopic 340-40, Other Assets and Deferred Costs - Contracts with Customers, or evaluated its contracts in the context of these new standards, it is impracticable to reasonably determine pro forma revenues or other related amounts impacted by the adoption of these standards for the six months ended June 30, 2018. Therefore, the unaudited pro forma condensed combined financial statements set forth below does not include an unaudited pro forma condensed combined statement of operations for the six months ended June 30, 2018. Because Coriant has not yet adopted ASC 606 and Subtopic 340-40 as described above, we have obtained permission from the SEC to exclude an unaudited pro forma condensed combined statement of operations for the six months ended June 30, 2018. The adoption of ASC 606 and Subtopic 340-40 may result in a material decrease to Coriant’s revenue for the six months ended June 30, 2018, and may also result in a material decrease to deferred revenue, accounts receivable or other assets of Coriant, or a material increase in liabilities of Coriant as of June 30, 2018. However, it is difficult to predict the exact impact of this change to accounting principles. As a result, the adoption of ASC 606 and Subtopic 340-40 could have a material adverse effect on Coriant’s financial position and results of operations as of and for the six months ended June 30, 2018 and future periods and, consequently, on our revenue and results of operations for that period on a combined basis after giving effect to the Acquisition. After the close of the Acquisition, we anticipate completing a more detailed review of Coriant’s contracts to calculate appropriate pro forma adjustments consistent with ASC 606 and Subtopic 340-40. However, pro forma adjustments for the six months ended June 30, 2018 would have included an increase of $12 million amortization expense for intangible assets recorded in cost of sales and operating expenses, and a net decrease of $33 million of interest expense.

The unaudited pro forma condensed combined financial information has been prepared in accordance with Article 11 of SEC Regulation S-X, except as noted in the preceding paragraph with respect to the unaudited pro forma condensed combined statement of operations for the six months ended June 30, 2018. See “Risk Factors—The pro forma financial data included in this prospectus supplement may not be an indication of the combined company’s financial condition or results of operations following the Acquisition.” The unaudited pro forma adjustments reflecting the Acquisition have been prepared in accordance with the business combination accounting guidance as provided in Accounting Standards Codification 805, Business Combinations, and reflect the preliminary allocation of the purchase price to the acquired assets and assumed liabilities based on a preliminary estimate of fair values, using available information and the assumptions set forth in the notes to the unaudited pro forma condensed combined financial information. The estimates of fair values of assets and liabilities acquired are preliminary and subject to change when the formal valuation and other studies are finalized and will be based on the valuation as of the actual closing date of the Acquisition. The unaudited pro forma adjustments related to the Offering are preliminary in nature and reflect the Company’s best estimates of the proceeds and related interest assumptions at the time of the preparation of this unaudited pro forma

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condensed combined financial information. Adjustments to these preliminary estimates are expected to occur and these adjustments could have a material impact on the accompanying unaudited pro forma condensed combined financial information.

The historical condensed combined financial information has been adjusted to give effect to pro forma events that are (1) directly attributable to the Transactions, (2) factually supportable, and (3) with respect to the unaudited pro forma condensed combined statement of operations, expected to have a continuing impact on the operating results. The unaudited pro forma condensed combined financial information should be read together with the accompanying notes to the unaudited pro forma condensed combined financial statements and in conjunction with the following:

The unaudited pro forma adjustments are based on preliminary estimates and are not necessarily indicative of or intended to represent the results that would have been achieved had the Transactions been consummated as of the dates indicated or that may be achieved in the future. The actual results reported by the combined company in periods following the Transactions may differ significantly from those that are reflected in the unaudited pro forma condensed combined financial information for a number reasons, including the effects of applying final purchase accounting, the incremental costs incurred to integrate the two companies, and the final terms and interest rate for the Offering. Additionally, the Offering that is anticipated to finance the Acquisition is included in the unaudited pro forma financial information reflecting the terms and rates we expect to achieve based on current market rates. The actual terms of the Offering will be subject to market conditions. In addition, this unaudited pro forma condensed combined financial information should be read together with the information under “Risk Factors” in the Quarterly Report, the Annual Report and this prospectus supplement. The unaudited pro forma condensed combined financial information does not reflect any cost savings or associated costs to achieve such savings from operating efficiencies, synergies, or other restructuring that may result from the Acquisition. The unaudited pro forma adjustments are based upon available information and certain assumptions that Infinera believes are reasonable under the circumstances. Actual adjustments may differ from the amounts reflected in the unaudited pro forma condensed combined financial statements, and the differences may be material.

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INFINERA CORPORATION

UNAUDITED PRO FORMA CONDENSED COMBINED BALANCE SHEET

AS OF JUNE 30, 2018

(in millions)

See accompanying Notes to the Unaudited Pro Forma Condensed Combined Financial Information

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INFINERA CORPORATION

UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF OPERATIONS

FOR THE YEAR ENDED DECEMBER 30, 2017

(in millions, except per share amounts)

See accompanying Notes to the Unaudited Pro Forma Condensed Combined Financial Information

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INFINERA CORPORATION

NOTES TO UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

1. BASIS OF PRO FORMA PRESENTATION

The historical financial information has been adjusted to give pro forma effect to events that are: (a) directly attributable to the Transactions, (b) factually supportable, and (c) with respect to the unaudited pro forma condensed combined statement of operations, expected to have a continuing impact on the combined results. The unaudited pro forma adjustments related to the Acquisition are preliminary and based on estimates of the fair value and useful lives of the assets acquired and liabilities assumed, and have been prepared to illustrate the estimated effect of the Acquisition and certain other adjustments. The final determination of the purchase price allocation will be based on the final valuation of the fair values of assets acquired and liabilities assumed as of the actual closing date of the Acquisition. The unaudited pro forma adjustments related to the Offering are preliminary in nature and reflect Management’s best estimates of the proceeds and related interest assumptions at the time of the preparation of these unaudited pro forma condensed combined financial information. The unaudited pro forma condensed combined balance sheet as of June 30, 2018 gives effect to the planned Transactions as if they had been consummated on June 30, 2018. The unaudited pro forma condensed combined statement of operations the year ended December 30, 2017 give effect to the Transactions as if they had been consummated on January 1, 2017, the beginning of Infinera’s most recently completed fiscal year.

The unaudited pro forma condensed combined financial information was prepared in accordance with SEC Regulation S-X Article 11, except that the unaudited pro forma condensed combined financial statements set forth above does not include a condensed combined statement of operations for the six months ended June 30, 2018. See “Risk Factors—The pro forma financial data included in this prospectus supplement may not be an indication of the combined company’s financial condition or results of operations following the Acquisition.” The unaudited pro forma condensed combined financial information included herein was derived from Infinera’s and Coriant’s consolidated statements of operations for the fiscal years ended December 30, 2017 and December 31, 2017, respectively, and from Infinera’s and Coriant’s unaudited condensed consolidated balance sheets as of June 30, 2018, which are prepared in accordance with U.S. GAAP. Certain amounts in the historical consolidated financial statements of Coriant have been reclassified within the “as adjusted” column in the unaudited pro forma condensed combined financial information so that presentation would conform with Infinera’s financial statement presentation. These reclassifications have no effect on previous reported total assets, total liabilities, and shareholders’ equity, or net income (loss) of Infinera or Coriant.

Unless otherwise indicated, defined line items included in the footnotes have the meanings given to them in the historical financial statements of Coriant.

2. SIGNIFICANT ACCOUNTING POLICIES

The unaudited pro forma condensed combined consolidated financial information has been prepared using the significant accounting policies as set forth in our audited consolidated financial statements for the year ended December 30, 2017. Based on the procedures performed to date the Company has determined that no significant adjustments are necessary to conform Coriant’s financial statements to the accounting policies used by Infinera in the preparation of the unaudited pro forma condensed combined financial information, with the exception of the adoption of ASC 606, Revenue from Contracts with Customers and Subtopic 340-40, Other Assets and Deferred Costs—Contracts with Customers. After the consummation of the Acquisition, we will complete a more detailed review of the Coriant accounting policies. As a result of that review, differences could be identified between the accounting policies of the two companies that, when conformed, could have a material impact on the combined financial statements.

3. PRELIMINARY PURCHASE CONSIDERATION AND PURCHASE PRICE ALLOCATION

The preliminary purchase consideration of the Acquisition is estimated to be $355 million, consisting of $230 million in cash consideration, less deductions of $63 million, and $188 million in equity consideration. The

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estimated purchase price that is reflected in this unaudited pro forma condensed combined financial information does not purport to represent what the actual purchase price will be and the actual purchase price may differ materially from the estimated purchase price due to possible fluctuations in working capital and other closing adjustments. The preliminary purchase consideration is $355 million as follows: