SUMMARY

The following summary highlights selected information in this proxy statement/prospectus and may not contain all the information that may be important to you. Accordingly, we encourage you to read carefully this entire proxy statement/prospectus, its annexes and the documents referred to in this proxy statement/prospectus. Each item in this summary includes a reference directing you to the page in this proxy statement/prospectus where the subject is discussed in more detail. You may obtain the information incorporated by reference into this proxy statement/prospectus without charge by following the instructions under the section entitled “Where You Can Find More Information” beginning on page 211 of this proxy statement/prospectus.

The Merger and the Merger Agreement

The terms and conditions of the merger are contained in the merger agreement, a copy of which is attached as Annex A to this proxy statement/prospectus. We encourage you to read the merger agreement carefully and in its entirety, as it is the legal document that governs the merger.

Pursuant to the merger agreement, Merger Sub will merge with and into Cyan, with Cyan continuing as the surviving corporation and a wholly owned subsidiary of Ciena. Immediately thereafter, Cyan will be merged with and into Ciena, and the separate existence of Cyan will cease. Following the merger, Cyan common stock will be delisted from the NYSE, deregistered under the Exchange Act and will cease to be publicly traded.

Per Share Merger Consideration (Page 65)

At the effective time, each share of Cyan common stock issued and outstanding immediately prior to the effective time will be converted into the right to receive merger consideration having a value at closing of the aggregate exchange ratio (0.224 shares of Ciena common stock), consisting of: (i) 0.19936 (89% of the aggregate exchange ratio) shares of Ciena common stock (plus cash in lieu of any fractional shares resulting therefrom equal to the product of (A) the fractional share interest to which a stockholder would otherwise be entitled and (B) the volume weighted average price per share of Ciena common stock on the NYSE on the last trading day prior to closing, rounded to the nearest cent), and (ii) an amount of cash, without interest, equal to the product of (A) 0.02464 (11% of the aggregate exchange ratio) multiplied by (B) the volume weighted average price per share of Ciena common stock on the NYSE on the last trading day prior to closing.

Financing of the Merger (Page 112)

Ciena’s obligation to complete the merger is not contingent upon receipt by Ciena of any financing. Ciena anticipates that the funds needed to pay the cash portion of the merger consideration and other merger fees and expenses will be derived from cash on hand.

For more information on the financing of the merger, see the section entitled “The Merger—Financing of the Merger” beginning on page 112 of this proxy statement/prospectus.

Recommendation of the Cyan Board; Cyan’s Reasons for the Merger (Page 88)

At a meeting held on May 3, 2015, the Cyan board unanimously approved the merger agreement, the merger and all of the other transactions contemplated by the merger agreement, declared that it is in the best interests of Cyan and its stockholders to enter into the merger agreement and consummate the merger and all of the other transactions contemplated by the merger agreement, directed that the adoption of the merger agreement be submitted to a vote at a meeting of the Cyan stockholders and recommended that the Cyan stockholders vote to adopt the merger agreement. Accordingly, the Cyan board unanimously recommends that the Cyan stockholders

vote “FOR” the proposal to adopt the merger agreement. The Cyan board also unanimously recommends that the Cyan stockholders vote “FOR” the NYSE share issuance proposals, “FOR” the nominees for election as Class II directors to the Cyan board, “FOR” the ratification of the appointment of Ernst & Young LLP as Cyan’s independent registered public accounting firm for the fiscal year ending December 31, 2015, and “FOR” the approval of the adjournment of the postponed annual meeting, if necessary or appropriate, to solicit additional proxies in favor of the adoption of the merger agreement or the NYSE share issuance proposals.

In evaluating the merger, the Cyan board consulted with and received the advice of Cyan’s outside legal and financial advisors, discussed certain issues with Cyan senior management and considered a number of factors that it believed supported its decision to enter into the merger agreement and consummate the merger, including, without limitation, those listed in “The Merger—Recommendation of the Cyan Board; Cyan’s Reasons for the Merger” beginning on page 88 of this proxy statement/prospectus.

Opinions of Cyan’s Financial Advisors (Page 92)

Opinion of Jefferies LLC

In connection with the merger and the second step merger, Jefferies LLC, which we refer to as Jefferies, Cyan’s financial advisor, delivered a written opinion, dated May 3, 2015, to the Cyan board as to the fairness, from a financial point of view and as of such date, of the merger consideration to be received by holders of Cyan common stock pursuant to the merger agreement. The full text of Jefferies’ opinion, a copy of which is attached as Annex C to this proxy statement/prospectus, describes the various assumptions made, procedures followed, matters considered and limitations and qualifications on the review undertaken by Jefferies. Jefferies’ opinion was provided for the use and benefit of the Cyan board (in its capacity as such) in its evaluation of the merger consideration from a financial point of view and did not address any other aspect of the merger or any other matter. The opinion did not address the relative merits of the merger or other transactions contemplated by the merger agreement as compared to any alternative transaction or opportunity that might be available to Cyan, nor did it address the underlying business decision by Cyan to engage in the merger. Jefferies’ opinion does not constitute a recommendation as to how any stockholder should vote or act in connection with the merger or any other transactions. The summary of Jefferies’ opinion set forth in this proxy statement/prospectus is qualified in its entirety by reference to the full text of Jefferies’ opinion.

Opinion of Houlihan Lokey Capital, Inc.

Cyan also engaged Houlihan Lokey Capital, Inc., which we refer to as Houlihan Lokey, to render an opinion with respect to the fairness of the per share merger consideration to holders of Cyan common stock. On May 3, 2015, at the Cyan board meeting at which the Cyan board approved the merger agreement and proposed merger, Houlihan Lokey rendered an oral opinion to the Cyan board (which was subsequently confirmed in writing by delivery of Houlihan Lokey’s written opinion to the Cyan board dated May 3, 2015), as to the fairness, from a financial point of view, of the per share merger consideration to be received by the holders of Cyan common stock in the merger, as of May 3, 2015, based upon and subject to the procedures followed, assumptions made, qualifications and limitations on the review undertaken and other matters considered by Houlihan Lokey in preparing its opinion.

Houlihan Lokey’s opinion was directed to the Cyan board and only addressed the fairness, from a financial point of view, of the per share merger consideration to be received by the holders of Cyan common stock in the merger and does not address any other aspect or implication of the merger. The summary of Houlihan Lokey’s opinion in this proxy statement/prospectus is qualified in its entirety by reference to the full text of its written opinion, which is included as Annex D to this proxy statement/prospectus and sets forth the procedures followed, assumptions made, qualifications and limitations on the review undertaken and other matters considered by Houlihan Lokey in preparing its opinion. However,

neither Houlihan Lokey’s opinion nor the summary of its opinion and the related analyses set forth in this proxy statement/prospectus are intended to be, and do not constitute, advice or a recommendation to the Cyan board or any stockholder as to how to act or vote with respect to the merger or related matters.

See “The Merger – Opinions of Cyan’s Financial Advisors”.

Information About the Postponed Annual Meeting (Page 56)

The postponed annual meeting will be held at Cyan’s headquarters, located at 1383 N. McDowell Blvd., Suite 300, Petaluma, California 94954 , on July 31, 2015, at 8:00 a.m., local time. The postponed annual meeting is being held in order to vote on:

Completion of the merger is conditioned on approval of the proposal to adopt the merger agreement. Further, Ciena’s obligation to consummate the merger is subject to approval of the NYSE share issuance proposals, but approval of the other matters before the postponed annual meeting is not a condition to the obligation of either Cyan or Ciena to complete the merger.

Only holders of record of issued and outstanding shares of Cyan common stock as of the close of business on June 25, 2015, the record date, are entitled to notice of, and to vote at, the postponed annual meeting or any adjournment or postponement of the postponed annual meeting. You may cast one vote for each share of Cyan common stock that you owned as of that record date.

Approval of the proposal to adopt the merger agreement requires the affirmative vote of the holders of a majority of the outstanding shares of Cyan common stock entitled to vote on the matter at the postponed annual meeting. Shares not present, and shares present and not voted, whether by broker non-vote, abstention or otherwise, will have the same effect as votes cast “AGAINST” the proposal to adopt the merger agreement.

For the NYSE share issuance proposals to be considered approved, a majority of the shares present or represented by proxy at the meeting and entitled to vote on the proposals at the meeting must be cast “FOR” the proposals. Under the applicable NYSE stockholder approval policy, approval of these proposals requires the affirmative vote of a majority of votes cast on the proposals at the meeting. Because under this policy abstentions are counted as “votes cast” for purposes of determining whether a majority of “votes cast” are in favor of the proposals, the requirements for approval under the bylaws and the NYSE policy are equivalent. Therefore, abstentions will have the same effect as a vote “AGAINST” the proposals in determining whether the proposals have received the requisite number of affirmative votes. Broker non-votes, if any, will have no effect on the outcome of the NYSE share issuance proposals.

The election of directors requires a plurality vote of the shares of common stock voted at the meeting. “Plurality” means that the individuals who receive the largest number of votes cast “FOR” are elected as directors. As a result, any shares not voted “FOR” a particular nominee (whether as a result of stockholder withholding or a broker non-vote) will not be counted in such nominee’s favor and will have no effect on the outcome of the election.

For the proposal to ratify the appointment of independent accountants and the proposal to adjourn the meeting to be considered approved, they must receive the affirmative vote of a majority of the shares present in person or by proxy at the meeting and entitled to vote thereon. Abstentions will have the same effect as a vote “AGAINST” the proposals. Broker non-votes, if any, will have no effect on the outcome of these proposals.

As of the close of business on the record date, there were 49,311,592 shares of Cyan common stock outstanding and entitled to vote.

Voting by Cyan’s Directors and Executive Officers (Page 57)

As of the record date, Cyan’s directors and executive officers and certain of their affiliates beneficially owned 24,018,189 shares of Cyan common stock entitled to vote at the postponed annual meeting. This represents approximately 45.0% in voting power of the outstanding shares of Cyan common stock entitled to be cast at the postponed annual meeting. Certain officers and directors and affiliated stockholders, including investment funds affiliated with certain directors, have entered into voting agreements that obligate them to vote “FOR” the proposal to adopt the merger agreement and “FOR” the NYSE share issuance proposals. Additionally, Cyan currently expects that the Cyan directors and executive officers will vote their shares of Cyan common stock “FOR” each of the other proposals before the postponed annual meeting, although none of them is obligated to do so.

Interests of Cyan’s Directors and Executive Officers in the Merger (Page 141)

In considering the recommendation of the Cyan board to adopt the merger agreement, Cyan stockholders should be aware that some of the Cyan directors and executive officers have interests in the merger and have arrangements that are different from, or in addition to, those of Cyan stockholders generally, including, but not limited to, the following:

These interests and arrangements may create potential conflicts of interest. The Cyan board was aware of these potential conflicts of interest and considered them, among other matters, in reaching its decision to approve the merger agreement, the merger, and the other transactions contemplated by the merger agreement. See the section entitled “Interests of Cyan’s Directors and Executive Officers in the Merger” beginning on page 141 of this proxy statement/prospectus for additional information.

Regulatory Approvals (Page 113)

The completion of the merger is subject to antitrust review in the United States. Under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, which we refer to as the HSR Act, and the rules promulgated thereunder, the merger may not be completed until notification and report forms have been filed with the Federal Trade Commission, which we refer to as the FTC, and the Department of Justice, which we refer to as the DOJ, and the applicable waiting period (or any extensions thereof) has expired or been terminated.

On May 15, 2015, Cyan and Ciena filed with the FTC and DOJ notification and report forms under the HSR Act with respect to the proposed merger. The waiting period under the HSR Act for the proposed merger terminated on June 15, 2015.

Ciena and Cyan have agreed to cooperate with each other and use, and cause their respective affiliates to use, their respective reasonable best efforts to obtain all regulatory approvals required to complete the merger in the most expeditious manner practicable. In furtherance of the foregoing, and subject to certain limitations, Ciena and Cyan have agreed to use their reasonable best efforts to:

Appraisal Rights of Cyan Stockholders (Page 203)

Cyan stockholders of record have appraisal rights under the DGCL in connection with the merger. Cyan stockholders who do not vote in favor of the adoption of the merger agreement and who otherwise comply with the applicable provisions of Section 262 of the DGCL will be entitled to exercise appraisal rights thereunder. Any shares of Cyan common stock held by a Cyan stockholder as of the record date who has not voted in favor of the adoption of the merger agreement and who has demanded appraisal for such shares in accordance with the DGCL will not be converted into a right to receive the per share merger consideration, unless such Cyan stockholder fails to perfect or withdraws or otherwise loses such stockholder’s appraisal rights under the DGCL. If, after the effective time, such holder of Cyan common stock fails to perfect or withdraws or otherwise loses his, her or its appraisal rights, each such share will be treated as if it had been converted as of the effective time into a right to receive the per share merger consideration, without interest thereon, less any withholding taxes. The relevant provisions of the DGCL are included as Annex E to this proxy statement/prospectus.

You are encouraged to read these provisions carefully and in their entirety. Due to the complexity of the procedures for exercising your appraisal rights, Cyan stockholders who are considering exercising such rights are encouraged to seek the advice of legal counsel. Failure to strictly comply with these provisions will result in the loss of appraisal rights. See the section entitled “Appraisal Rights of Cyan Stockholders” beginning on page 203 of this proxy statement/prospectus for additional information and the text of Section 262 of the DGCL reproduced in its entirety as Annex E to this proxy statement/prospectus.

Conditions to Completion of the Merger (Page 132)

Each party’s obligation to consummate the merger is subject to the satisfaction or waiver, to the extent applicable, of the following conditions:

In addition, the obligations of Ciena and Merger Sub to effect the merger are subject to the satisfaction, or waiver of the following additional conditions:

In addition, the obligations of Cyan to effect the merger are subject to the satisfaction or waiver of the following additional conditions:

For a more complete summary of the conditions that must be satisfied or waived prior to completion of the merger, see the section entitled “The Merger Agreement—Conditions to Completion of the Merger” beginning on page 132 of this proxy statement/prospectus.

No Solicitation or Negotiation of Takeover Proposals (Page 125)

The merger agreement provides that neither Cyan nor any of its subsidiaries will, and Cyan will instruct and cause its and its subsidiaries’ respective directors, officers and other representatives not to, directly or indirectly:

Notwithstanding these restrictions, prior to the adoption of the merger agreement by the stockholders of Cyan, Cyan may, after providing notice to Ciena and entering into a confidentiality agreement with the applicable third party:

in each case if:

No Change in Recommendations (Page 127)

Subject to certain exceptions described below, the Cyan board and each committee of the Cyan board may not:

However, at any time before the Cyan stockholder approval is obtained, the Cyan board may make an adverse recommendation change in response to an intervening event or a superior proposal (as such terms are specifically defined in the merger agreement), subject to compliance in all material respects with requirements in the merger agreement with respect to any such intervening event or superior proposal, if the Cyan board determines in good faith, after consultation with its outside legal counsel, that the failure to take such action would reasonably be expected to result in a violation of the Cyan board’s fiduciary duties under applicable law.

The Cyan board may not make an adverse recommendation change until after at least three business days following Ciena’s receipt of written notice from Cyan advising that the Cyan board intends to take such action and the basis for doing so. After providing such notice and prior to making such adverse recommendation change:

Any amendment to the financial terms or other material terms of any takeover proposal will be deemed to be a new takeover proposal except that the three business day notice period for such new acquisition proposal will be two business days for such purposes.

Termination of the Merger Agreement (Page 134)

The merger agreement may be terminated at any time prior to the effective time, whether before or (unless otherwise specified below) after the receipt of the Cyan stockholder approval, by delivery of written notice to the other parties to the merger agreement under the following circumstances:

Termination Fees and Expenses (Page 135)

Cyan will be required to pay a termination fee of $15.0 million to Ciena if:

If the merger agreement is terminated pursuant to the first bullet above, the termination fee must be paid on the earlier of (i) the date of entry into a definitive agreement with respect to a takeover proposal or (ii) the date of consummation of the transaction referenced in clause (iii) of the first bullet above. If the termination is made

pursuant to the second bullet above, the termination fee must be paid within three business days of the date of termination. If the termination is made pursuant to the third bullet above, the termination fee must be paid contemporaneously with the termination of the merger agreement.

Cyan will be required to reimburse Ciena for all documented out-of-pocket expenses, including those of the exchange agent and its representatives, incurred by Ciena or Merger Sub in connection with the merger agreement and the transactions contemplated thereby in the event of clauses (i) and (ii) of the first bullet above apply, in each case up to a maximum amount of $2.0 million. Any termination fee payable by Cyan will be offset by the amount of any of Ciena or Merger Sub’s expenses previously reimbursed pursuant to the merger agreement. In the event any such expenses are paid, and thereafter Cyan becomes obligated to pay a termination fee as a result of any of the items set forth above becoming applicable, then the amount of such termination fee shall be reduced by the amount of any such expenses so paid.

If Cyan fails promptly to pay any of the foregoing fees or expenses, and, in order to obtain such payment, Ciena commences a suit that results in a judgment against Cyan for the payment of such fees or expenses, Cyan must pay to Ciena its costs and expenses (including attorneys’ fees and expenses) in connection with such suit, together with interest on the amount of such amount from the date such payment was required to be made until the date of payment at the prime rate as published in The Wall Street Journal in effect on the date such payment was required to be made.

Treatment of Cyan Warrants and Convertible Notes (Page 130)

With respect to Cyan’s $50.0 million principal amount of outstanding convertible notes, the merger is expected to constitute a “fundamental change,” as such term is defined in the indenture governing the convertible notes, which we refer to as the indenture. The indenture provides that for a period of time beginning 25 trading days prior to the anticipated effective date of the merger and continuing until the date set for repurchase of any convertible notes tendered for purchase under the special purchase rights of holders triggered if the merger constitutes a “fundamental change” as described below, the note holders will be entitled to convert their convertible notes into the amount of cash and shares of Cyan common stock provided for in the indenture. If converted on or after the effective date of the merger, a converting noteholder will receive the cash and shares of Ciena common stock that a holder of the number of shares of Cyan common stock into which such notes were convertible immediately prior to the merger would have been entitled to receive in connection with the merger, subject to Ciena’s right to elect to pay cash in lieu of issuing such shares. The merger is also expected to constitute a “make-whole fundamental change” under the indenture. As a result, the applicable conversion rate will be increased pursuant to a make-whole provision in the indenture with respect to any conversion that occurs within the conversion period following the effective date of the merger and prior to the related repurchase date set by Ciena (but not with respect to future conversions), as further described in the indenture. The merger will also give rise to a right of holders of the convertible notes to require Ciena to repurchase their convertible notes at 100% of the principal amount thereof plus accrued and unpaid interest, to the extent the merger constitutes a “fundamental change.” The value of the merger consideration is expected to be higher than the principal amount of the convertible notes.

The merger also is expected to constitute a “fundamental transaction” as defined in the warrants. Cyan will issue timely notices to the holders of the warrants as to the record date for determining rights to vote with respect to the merger (notwithstanding that the warrants are not exercisable), and Cyan will otherwise take all actions required by the warrants in connection with the merger. Pursuant to their terms, the warrants will be deemed to have been automatically exercised on a cashless basis immediately prior to the effective time of the merger, at an exercise price of $3.62 per share. The shares of Cyan common stock issuable as a result of such deemed exercise will be deemed issued and outstanding immediately prior to the effective time and the shares of Ciena common stock issued in exchange for such Cyan shares pursuant to the merger will be registered pursuant to the Form S-4

of which this proxy statement/prospectus forms a part. Before the effective time, Cyan may, and intends to, amend one or more of the warrants to delete the provisions limiting the number of shares issuable under the warrants to any holder to 9.99% of the outstanding shares of Cyan.

The shares issuable on conversion of the convertible notes and upon exercise of the warrants are currently limited by the terms of those securities as a consequence of the limitations on private placements of voting equity securities, including to affiliates of Cyan, under the listing standards of the NYSE. The NYSE share issuance proposals are required in order to lift the restrictions on the issuance of Cyan shares under these instruments. See “Proposal No. 3—Approval of Certain Issuances of Cyan Common Stock in Excess of 20% of Cyan’s Outstanding Shares upon Conversion of Cyan’s Outstanding Convertible Notes and Exercise of Related Warrants Issued December 2014” on page 154 and “Proposal No. 4—Approval of Certain Issuances of Cyan’s Common Stock to Certain Affiliated Holders upon Conversion of Cyan’s Outstanding Convertible Notes and Exercise of Related Warrants Issued December 2014” on page 161. Prior to obtaining stockholder approval of such issuances, Cyan is required to pay the cash value of the shares that would otherwise be issuable upon conversion or exercise, as the case may be.

The Voting Agreements (Page 138)

On May 3, 2015, Ciena and certain Cyan officers and directors and affiliated stockholders, including investment funds affiliated with certain directors, entered into voting agreements. As of the record date, these persons beneficially owned in the aggregate 22,311,690 shares of Cyan common stock, comprising 19,411,926 shares of Cyan common stock (or approximately 39.4% of the shares of Cyan common stock outstanding as of the close of business on the record date) and 2,899,764 shares issuable upon exercise of Cyan options exercisable or the settlement of Cyan restricted stock units within 60 days of the record date, for aggregate beneficial ownership of approximately 42.7% of the shares of Cyan common stock outstanding as of the close of business on the record date. Each of these persons has agreed to vote all beneficially owned shares of Cyan common stock in favor of adoption of the merger agreement and the NYSE share issuance proposals and any other matter that must be approved by Cyan stockholders in order to facilitate the merger, and to vote against, among other things, any proposal opposing or competing with the merger. Each voting agreement will terminate on the earliest to occur of the effective time of the consummation of the merger, the termination of the merger agreement, and mutual agreement of Ciena and the applicable stockholder. Notwithstanding the foregoing, if the Cyan board of directors makes an adverse recommendation change with respect to an “intervening event”, as such term is defined in the merger agreement, then the obligation of the stockholder to vote as described above will be modified such that the stockholder, together with the other Cyan stockholders entering into voting agreements, shall only be required to collectively vote an aggregate number of shares equal to 35% of the total voting power of the outstanding Cyan shares as described above, and the number of shares in excess of that percentage shall be voted on a pro rata basis on the merger and the NYSE share issuance proposals in a manner equivalent to the proportion of votes “FOR” and “AGAINST”, or abstain, cast by all of Cyan’s other stockholders on these matters. Each Cyan director and officer who has entered into a voting agreement has done so solely in his or her capacity as a stockholder and not in his or her capacity as a director or officer of Cyan or any of its subsidiaries. Accordingly, the voting agreements do not restrict or limit any of Cyan’s directors or officers from taking or omitting to take any action in his or her capacity as a director or officer of Cyan in order to fulfill his or her fiduciary obligations under applicable law or acting in such capacity or voting in such capacity in the good faith exercise of his or her fiduciary duties under applicable law. A copy of the form of voting agreement is attached to this proxy statement/prospectus as Annex B.

Accounting Treatment (Page 114)

Ciena prepares its financial statements in accordance with accounting principles generally accepted in the United States of America, which we refer to as GAAP. The merger will be accounted for using the acquisition method of accounting. Ciena will be treated as the acquiror for accounting purposes.

Material U.S. Federal Income Tax Consequences of the Merger (Page 190)

It is the intention of Ciena and Cyan that the merger and second step merger, considered together as a single integrated transaction for U.S. federal income tax purposes, will qualify as a “reorganization” within the meaning of the Code. Therefore, for U.S. federal income tax purposes, as a result of the merger, it is expected that a U.S. holder of shares of Cyan common stock generally will only recognize gain (but not loss) in an amount not to exceed the cash received as part of the merger consideration and will recognize gain or loss if such holder received cash in lieu of fractional shares of Cyan common stock.

Because individual circumstances may differ, we recommend that you consult your own tax advisor to determine the particular tax effects of the merger to you.

You should read the section entitled “Material U.S. Federal Income Tax Consequences of the Merger” beginning on page 190 of this proxy statement/prospectus for a more complete discussion of the material U.S. federal income tax consequences of the merger.

Comparison of Stockholders’ Rights (Page 194)

The rights of Cyan stockholders are governed by Cyan’s restated certificate of incorporation, which we refer to as the Cyan charter, by Cyan’s amended and restated bylaws, which we refer to as the Cyan bylaws, and by the DGCL. Your rights as a stockholder of Ciena will be governed by Ciena’s amended and restated certificate of incorporation, which we refer to as the Ciena charter, by Ciena’s amended and restated bylaws, which we refer to as the Ciena bylaws, and by the DGCL. Your rights under the Ciena charter and the Ciena bylaws will differ in some respects from your rights under the Cyan charter and the Cyan bylaws. For more detailed information regarding a comparison of your rights as a stockholder of Cyan and Ciena, see the section entitled “Comparison of Stockholders’ Rights” beginning on page 194 of this proxy statement/prospectus.

Parties to the Merger (Page 63)

Cyan, Inc.

1383 N. McDowell Blvd.

Suite 300

Petaluma, California 94954

(707) 735-2300

Cyan, a Delaware corporation, is a pioneer in innovative, carrier-grade networking solutions that transform disparate and inefficient legacy networks into open, high-performance networks. Cyan’s solutions include high-capacity, multi-layer switching and transport platforms as well as a carrier-grade software-defined networking platform for network virtualization and control. Cyan’s solutions enable network operators to virtualize their networks, accelerate service delivery and increase scalability and performance, while reducing costs. Cyan has designed its solutions to enable a variety of existing and emerging applications, including business Ethernet, wireless backhaul, broadband backhaul, cloud connectivity, bandwidth on demand, and network functions virtualization (NFV). By deploying Cyan’s solutions, network operators can transform legacy networks into open, multi-vendor, carrier-grade software-controlled networks. Cyan’s solutions not only reduce network operators’ ongoing capital and operating expenses, but also enable their networks to more flexibly support rapidly changing service requirements and new business models. Cyan is headquartered in Petaluma, California.

Cyan common stock is listed on the NYSE under the symbol “CYNI.”

Ciena Corporation

7035 Ridge Road

Hanover, Maryland 21076

(410) 694-5700

Ciena, a Delaware corporation, is a network specialist focused on communications networking solutions that enable converged, next-generation architectures, optimized to create and deliver the broad array of high-bandwidth services relied upon by business and consumer end users. Ciena provides equipment, software and services that support the transport, switching, aggregation, service delivery and management of voice, video and data traffic on communications networks. These solutions enable network operators to adopt software-programmable network infrastructures that offer the on-demand experience required by end users of services and applications. At the same time, these solutions yield business and operational value for network operators.

Ciena common stock is listed on the NYSE under the symbol “CIEN.”

Neptune Acquisition Subsidiary, Inc.

c/o Ciena Corporation

7035 Ridge Road

Hanover, Maryland 21076

(410) 694-5700

Merger Sub, a Delaware corporation and a wholly owned subsidiary of Ciena, was formed solely for the purpose of facilitating the merger. Merger Sub has not carried on any activities or operations to date, except for those activities incidental to its formation and undertaken in connection with the transactions contemplated by the merger agreement. By operation of the merger, Merger Sub will be merged with and into Cyan, with Cyan surviving the merger as a wholly owned subsidiary of Ciena. In the second step merger, Cyan will merge with and into Ciena.

SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA OF CYAN

The following table presents selected historical consolidated financial data for Cyan as of and for the fiscal years ended December 31, 2010, 2011, 2012, 2013 and 2014 and as of and for the three months ended March 31, 2014 and 2015. The balance sheet data as of December 31, 2013 and 2014 and the statement of operations data for the fiscal years ended December 31, 2012, 2013 and 2014 have been obtained from Cyan’s audited consolidated financial statements included in Cyan’s Annual Report on Form 10-K for the fiscal year ended December 31, 2014, which is incorporated by reference into this proxy statement/prospectus. The balance sheet data as of December 31, 2011 and 2012 and the statement of operations data for the fiscal years ended December 31, 2010 and 2011 have been derived from Cyan’s audited consolidated financial statements not incorporated into this document by reference. The balance sheet data as of March 31, 2015 and the statement of operations data for the three months ended March 31, 2014 and 2015 have been obtained from Cyan’s unaudited consolidated financial statements included in Cyan’s Quarterly Report on Form 10-Q for the three months ended March 31, 2015, which is incorporated by reference into this proxy statement/prospectus. The balance sheet data as of March 31, 2014 has been derived from Cyan’s unaudited consolidated financial statements included in Cyan’s Quarterly Report on Form 10-Q for the three months ended March 31, 2014, which has not been incorporated into this document by reference.

The information set forth below is not necessarily indicative of future results and should be read together with the other information contained in Cyan’s Annual Report on Form 10-K for the fiscal year ended December 31, 2014 and Cyan’s Quarterly Report on Form 10-Q for the three months ended March 31, 2015, including the sections entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and the consolidated financial statements and related notes therein. See the section entitled “Where You Can Find More Information” beginning on page 211 of this proxy statement/prospectus.

SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA OF CIENA

The following table presents selected historical consolidated financial data for Ciena as of and for the fiscal years ended October 31, 2010, 2011, 2012, 2013 and 2014 and as of and for the six months ended April 30, 2014 and 2015. The statement of operations data for the fiscal years ended October 31, 2012, 2013 and 2014 and the balance sheet data as of October 31, 2013 and 2014 have been obtained from Ciena’s audited consolidated financial statements included in Ciena’s Annual Report on Form 10-K for the fiscal year ended October 31, 2014, which is incorporated by reference into this proxy statement/prospectus. The statement of operations data for the fiscal years ended October 31, 2010 and 2011 and the balance sheet data as of October 31, 2010, 2011 and 2012 have been derived from Ciena’s audited consolidated financial statements for such years, which have not been incorporated into this document by reference. The financial data as of April 30, 2015 and for the six months ended April 30, 2014 and 2015 have been obtained from Ciena’s unaudited condensed consolidated financial statements included in Ciena’s Quarterly Report on Form 10-Q for the six months ended April 30, 2015, which is incorporated by reference into this proxy statement/prospectus. The financial data as of April 30, 2014 has been derived from Ciena’s unaudited condensed consolidated financial statements included in Ciena’s Quarterly Report on Form 10-Q for the six months ended April 30, 2014.

The information set forth below is not necessarily indicative of future results and should be read together with the other information contained in Ciena’s Annual Report on Form 10-K for the fiscal year ended October 31, 2014 and Ciena’s Quarterly Report on Form 10-Q for the six months ended April 30, 2015, including the sections entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and the consolidated financial statements and related notes therein. See the section entitled “Where You Can Find More Information” beginning on page 211 of this proxy statement/prospectus.

STATEMENT OF OPERATIONS DATA:

BALANCE SHEET DATA:

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS

The following unaudited pro forma condensed combined financial information has been prepared to illustrate the effect of the merger, the second step merger and related transactions. Under the terms of the merger agreement, each outstanding share of Cyan common stock at the effective time will be exchanged for merger consideration having a value at closing of 0.224 shares of Ciena common stock, consisting of: (i) 0.19936 (89% of the aggregate exchange ratio) shares of Ciena common stock (plus cash in lieu of any fractional shares resulting therefrom equal to the product of (A) the fractional share interest to which a stockholder would otherwise be entitled and (B) the volume weighted average price per share of Ciena common stock on the NYSE on the last trading day prior to closing, rounded to the nearest cent); and (ii) an amount of cash, without interest, equal to the product of (A) 0.02464 (11% of the aggregate exchange ratio) multiplied by (B) the volume weighted average price per share of Ciena common stock on the NYSE on the last trading day prior to closing.

The unaudited pro forma condensed combined financial statements give effect to the merger under the acquisition method of accounting in accordance with Financial Accounting Standards Board (FASB) Accounting Standard Codification (ASC) Topic 805, Business Combinations, which we refer to as ASC 805, with Ciena treated as the legal and accounting acquirer. The historical consolidated financial information has been adjusted in the unaudited pro forma condensed combined financial statements to give effect to pro forma events that are (1) directly attributable to the merger, (2) factually supportable and (3) with respect to the statements of operations, expected to have a continuing impact on the combined results of Ciena and Cyan. Although Ciena and Cyan have entered into the merger agreement, there is no guarantee that the merger will be completed. The unaudited pro forma condensed combined financial statements present the effect of the pending merger between Ciena and Cyan as if the merger had been completed on November 1, 2013 for statement of operations purposes and on April 30, 2015 for balance sheet purposes. Due to different fiscal periods for Ciena and Cyan, the April 30, 2015 pro forma condensed combined balance sheet is based upon the historical consolidated balance sheet data of Ciena as of April 30, 2015, and the historical balance sheet data of Cyan as of March 31, 2015. The October 31, 2014 pro forma condensed combined statement of operations includes the historical consolidated statement of operations data of Ciena for the twelve months ended October 31, 2014 and the historical consolidated statement of operations data of Cyan for the twelve months ended December 31, 2014. The April 30, 2015 pro forma condensed combined statement of operations includes the historical consolidated statement of operations data of Ciena for the six months ended April 30, 2015 and the historical consolidated statement of operations data of Cyan for the six months ended March 31, 2015. Due to the difference in fiscal year ends, Cyan’s fourth quarter 2014 operating results are included in both the year ended October 31, 2014 and six months ended April 30, 2015 pro forma operating results. The unaudited pro forma condensed combined statements of operations do not reflect future events that may occur after the merger, including, but not limited to, the anticipated realization of ongoing savings from operating synergies and certain one-time charges Ciena expects to incur in connection with the transaction, and including, but not limited to, costs in connection with integrating the operations of Ciena and Cyan.

These unaudited pro forma condensed combined financial statements are for informational purposes only. They do not purport to indicate the results that would actually have been obtained had the merger been completed on the assumed date or for the periods presented, or which may be realized in the future. To produce the pro forma financial information, Ciena adjusted Cyan’s assets and liabilities to their estimated fair values. As of the date of this proxy statement/prospectus, Ciena has not completed the detailed valuation work necessary to arrive at the required estimates of the fair value of the Cyan assets to be acquired and the liabilities to be assumed and the related allocation of purchase price, nor has it identified all adjustments necessary to conform Cyan’s accounting policies to Ciena’s accounting policies. A final determination of the fair value of Cyan’s assets and liabilities will be based on the actual net tangible and intangible assets and liabilities of Cyan that exist as of the date of completion of the merger and, therefore, cannot be made prior to that date. Additionally, the value of merger consideration will be determined based on the trading price of Ciena common stock at the time of the

completion of the merger. Accordingly, the accompanying unaudited pro forma purchase price allocation is preliminary and is subject to further adjustments as additional information becomes available and as additional analyses are performed. The preliminary unaudited pro forma purchase price allocation has been made solely for the purpose of preparing the accompanying unaudited pro forma condensed combined financial statements. The preliminary purchase price allocation was based on Ciena’s historical experience and certain data available through the public domain and Ciena’s due diligence review of Cyan’s business. Until the merger is completed, both companies are limited in their ability to share information with each other. Upon completion of the merger, valuation work will be performed and any increases or decreases in the fair value of relevant statement of financial position amounts will result in adjustments to the statement of financial position and/or statements of operations until the purchase price allocation is finalized.

There can be no assurance that such finalization will not result in material changes from the preliminary purchase price allocation included in the accompanying unaudited pro forma condensed combined financial statements.

The unaudited pro forma condensed combined financial statements should be read in conjunction with:

UNAUDITED PRO FORMA CONDENSED COMBINED

BALANCE SHEET

(in thousands)