FORM S-4

CIENA Corporation

1201 Winterson Road

Russell B. Stevenson, Jr.

Copies to:

    Approximate date of commencement of proposed sale to the public:As soon as practicable after this Registration Statement becomes effective and all other conditions to the merger contemplated by the Agreement and Plan of Merger dated as of February 17, 2002,April 9, 2003, as such agreement may be amended, described in the enclosed Prospectus have been satisfied or waived.

CALCULATION OF REGISTRATION FEE

(1)	The Registration Statement covers the maximum number of shares of CIENA common stock which are expected to be issued in connection with the transactions described herein in the proposed merger of ONI Systems Corp.WaveSmith Networks, Inc. with and into CIENA, assuming the exercise of all currently outstanding stock options and warrants.warrants that will be outstanding at closing.
(2)	Includes corresponding rights to purchase shares of CIENA series A Junior Participating Preferred Stock pursuant to a Rights Agreement dated as of December 29, 1997, as amended, between CIENA and BankBoston N.A.
(3)	Estimated solelyPursuant to Rule 457(f)(2), because there is currently no public trading market for the purpose of calculatingWaveSmith common and preferred stock, the registration fee required by Section 6(b)was computed on the basis of 1/3 of the Securities Act of 1933, by multiplying the averagepar value of the high and low prices of shares of ONI Systems common and preferred stock on March 19, 2002,of WaveSmith computed as reported on Nasdaq by 164,946,353,of April 29, 2003. The par value equaled $2,176,376.28 in the number of shares of ONI Systems common stock outstanding on the close of business on March 19, 2002, assuming the exercise of all currently outstanding stock options and warrants.aggregate.

    The registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

The information in this joint proxy statement/prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This joint proxy statement/prospectus is not an offer to sell these securities and we are not soliciting offers to buy these securities in any state where the offer or sale is not permitted.

Preliminary Prospectus Dated March 20, 2002dated April 29, 2003. Subject to Completion.

Dear CIENA and ONI Systems stockholders:WaveSmith Stockholder:

    On behalf ofAfter careful consideration, the boards of directors of WaveSmith Networks, Inc. and management teamsCIENA Corporation have approved the merger of both CIENA and ONI Systems, we areWaveSmith with CIENA. I am pleased to deliver our jointprovide to you the enclosed proxy statement/prospectus forrelating to a special meeting of the stockholders of WaveSmith to be held on                                 , 2003, at [9:00 a.m.] Eastern Time, at the offices of Testa, Hurwitz & Thibeault, LLP at 125 High Street, Boston, Massachusetts.

    At the special meeting, you will be asked to vote, in person or by proxy, on the proposed merger involvingof WaveSmith with CIENA. The merger will be effected pursuant to the agreement and plan of merger, dated as of April 9, 2003, by and between CIENA and ONI Systems. Upon completionWaveSmith. Pursuant to the agreement and plan of merger, each outstanding share of capital stock of WaveSmith will be converted into the merger, holders of ONI Systems common stock willright to receive 0.7104 shares of CIENA common stock for each sharein the amounts set forth in the agreement and plan of ONI Systems commonmerger. CIENA will issue approximately 33 million shares in the merger to WaveSmith’s stockholders, including shares underlying WaveSmith stock they hold at that time.options and warrants. CIENA common stock is traded on the Nasdaq StockNational Market under the trading symbol “CIEN.” The closing price for CIENA common stock reported on the Nasdaq National Market on April     , 2003, was $                per share. If the merger is approved and consummated, WaveSmith will cease to exist as a separate entity. Following the merger, based on 434,980,818 outstanding shares of CIENA common stock as of April 25, 2003, and assuming that all of the WaveSmith stock options or warrants have been exercised, WaveSmith stockholders would own approximately 7.7% of the combined company and CIENA stockholders would own approximately 92.3% of the combined company. The merger is described more fully in the proxy statement/prospectus.

    The boardsAs described in the notice to stockholders dated April     , 2003, if the proposed merger with CIENA is approved at the special meeting, WS Contract Corp., a Delaware corporation and wholly-owned subsidiary of WaveSmith, will merge with and into WaveSmith immediately prior to the merger of WaveSmith into CIENA. In connection with the merger of WS Contract Corp. into WaveSmith, the Third Amended and Restated Certificate of Incorporation of WaveSmith will be amended and restated in its entirety and the liquidation preferences of the shares of WaveSmith’s preferred stock will be reduced.

WaveSmith’s board of directors of CIENAhas carefully reviewed and ONI Systems recommend that you vote in favor ofconsidered the proposed merger.

     The combination of our companies will create a company that is better positioned to serve the needs of communications service providers for next-generation optical networking productsterms and will reduce both the capital and operating costs for our customers. There are significant financial benefits from the combination, including cost savings from the elimination of duplicative infrastructures and the opportunity to take advantage of economies of scale.

     We encourage you to read this joint proxy statement/prospectus which includes important information about the merger. In addition, the section entitled “Risk Factors” beginning on page      of this joint proxy statement/ prospectus contains a description of risks that you should consider in evaluating the merger.

     Completionconditions of the merger requiresand the approvalagreement and plan of both CIENAmerger and ONI Systemshas concluded that the terms are fair to, and in the best interests of, WaveSmith and its stockholders. CIENA and ONI Systems have scheduled special meetings of their stockholders to obtain these approvals on                     , 2002. Information regarding these special meeting is included in this joint proxy statement/ prospectus. The CIENAWaveSmith’s board of directors recommends that CIENA stockholdersyou vote “FOR” the proposal to approveFORapproval and adoptadoption of the merger and the agreement and approveplan of merger.

The agreement and plan of merger must be approved and adopted by the merger. The ONI Systems boardholders of directors recommends that ONI Systems stockholders(i) a majority of the outstanding shares of WaveSmith’s common stock and preferred stock, voting as a single class on an as-converted basis, (ii) a majority of the outstanding shares of WaveSmith’s series A and series A-1 preferred stock, voting together as a single class on an as-converted basis, (iii) 60% of the outstanding shares of WaveSmith’s series B and series B-1 preferred stock, voting together as a single class on an as-converted basis, and (iv) 75% of the outstanding shares of WaveSmith’s series C preferred stock, voting as a separate class on an as-converted basis. Stockholders of WaveSmith entitled to vote “FOR”at the proposalspecial meeting who collectively beneficially own approximately 25.5% of WaveSmith’s common stock, 87.9% of WaveSmith’s series A and A-1 preferred stock, on an as-converted basis, 81.0% of WaveSmith’s series B and B-1 preferred stock, on an as-converted basis, 72.0% of WaveSmith’s series C preferred stock, on an as-converted basis and 63.4% of WaveSmith’s common stock and preferred stock together, on an as-converted basis, have already agreed to approve and adoptvote their shares in favor of the merger and the agreement and approveplan of merger.You are encouraged to review the merger.

enclosed proxy statement/prospectus and in particular review the matters referred to under “Risk Factors” starting on page 8. Whether or not you plan to attend the special meeting, please take the time to vote by promptly completing and mailing the enclosed proxy card in the postage-paid envelope provided.Your vote is very important. Please vote “FOR” your company’s proposal by signing and dating the enclosed proxy card or voting instruction card today and returning it in the pre-addressed envelope provided.

Thank you for your support.

Gary B. Smith	Hugh C. MartinOn Behalf of the Board of Directors,
	Thomas Burkardt
	Chief Executive Officer and President

Prospectus dated                  , 20022003

Neither the Securities and Exchange Commission nor any state securities regulator has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus and proxy statement. Any representation to the contrary is a criminal offense.

CIENA CORPORATIONWAVESMITH NETWORKS, INC.

NOTICE OF THE SPECIAL MEETING OF STOCKHOLDERS

TO BE HELD ON                                                   , 2003

To the stockholders of WaveSmith Networks, Inc.:

     A special meeting of the stockholders of WaveSmith Networks, Inc., a Delaware corporation, will be held at the offices of Testa, Hurwitz & Thibeault, LLP, 125 High Street, Boston, Massachusetts, on                               ,                      , 2003 at [9:00 a.m.] Eastern Time for the following purposes:

     1. To approve and adopt the merger and the agreement and plan of merger, dated as of April 9, 2003, by and between CIENA Corporation and WaveSmith pursuant to which WaveSmith will be merged with and into CIENA, with CIENA being the surviving corporation. A copy of the agreement and plan of merger is attached as Annex A to the proxy statement/prospectus accompanying this notice;

     2. To grant discretionary authority to the WaveSmith board of directors to adjourn or postpone the WaveSmith special meeting to solicit additional votes to approve the merger, if necessary; and

     3. To consider and act upon any other matter which may properly come before the special meeting.

     This proxy statement/prospectus and the proxy card are being furnished to the stockholders of WaveSmith in connection with the solicitation of proxies by WaveSmith’s board of directors for use at the special meeting of stockholders.

WaveSmith’s board of directors has approved the merger and the agreement and plan of merger and recommends that you voteFORapproval and adoption of the merger and agreement and plan of merger andFORthe grant of discretionary authority to adjourn the special meeting. The proposals are described in more detail in the accompanying proxy statement/prospectus, which you should read in its entirety before voting.

     The board of directors has fixed the close of business on                                                   , 2003 as the record date for determining the stockholders entitled to receive this notice, and to vote their shares at the meeting or any adjournment or postponement of the meeting. Only holders of record of common stock and preferred stock of WaveSmith at the close of business on the record date will be entitled to notice of, and to vote at, the meeting and any adjournment or postponement of the meeting. As of that date, there were (i) 79,787,626 shares of common stock outstanding, (ii) 185,000 shares of series A preferred stock outstanding, (iii) 9,015,000 shares of series A-1 preferred stock outstanding, (iv) 2,353,370 shares of series B preferred stock outstanding, (v) 33,333,331 shares of series B-1 preferred stock outstanding and (vi) 92,963,301 shares of series C preferred stock outstanding.

     Each share of common stock is entitled to 1 vote on each matter brought properly before the meeting. Each share of preferred stock is entitled to a number of votes equal to the number of shares of common stock into which such share of preferred stock may be converted into pursuant to WaveSmith’s certificate of incorporation. Each share of series A preferred stock is entitled to 2 votes for each matter brought properly before the meeting. Each share of series A-1 preferred stock is entitled to 3.51667 votes for each matter brought properly before the meeting. Each share of series B preferred stock is entitled to 1 vote for each matter brought properly before the meeting. Each share of series B-1 preferred stock is entitled to 2.4 votes for each matter brought properly before the meeting. Each share of series C preferred stock is entitled to 1 vote for each matter brought properly before the meeting.

     The representation in person, or by properly executed proxy, of the holders of a majority of all shares of capital stock entitled to vote at the special meeting is necessary to constitute a quorum at the special meeting of WaveSmith. In connection with the separate votes by the series A and series A-1 preferred

     Under Delaware law and the charter documents of WaveSmith, approval and adoption of the merger and the agreement and plan of merger requires the affirmative votes of (i) a majority of the outstanding shares of WaveSmith’s common stock and preferred stock, voting as a single class on an as-converted basis, (ii) a majority of the outstanding shares of WaveSmith’s series A and series A-1 preferred stock, voting as a single class on an as-converted basis, (iii) 60% of the outstanding shares of WaveSmith’s series B and series B-1 preferred Stock, voting as a single class on an as-converted basis and (iv) 75% of the outstanding shares of WaveSmith’s series C preferred stock, voting as a separate class on an as-converted basis.

     The board of directors has designated the two persons named on the enclosed proxy card, Thomas Burkardt and Gregg Savage, to serve as proxies in connection with the special meeting. All properly executed proxy cards will be voted (except to the extent that authority to vote has been withheld) and where a choice has been specified by the stockholder as provided in the proxy card, it will be voted in accordance with the specifications on the proxy card. If you sign and send in your proxy card and do not indicate how you want to vote, it will be voted in favor of approval of the merger and the agreement and plan of merger and in favor of the other proposals. You may revoke a proxy prior to its execution by giving written notice to Mr. Savage, the Secretary of WaveSmith, by submission of another proxy bearing a later date, or by voting in person at the special meeting. Such notice or later dated proxy will not affect a vote on any matter taken prior to the receipt of the proxy revocation by WaveSmith. Abstentions from voting identified as such on the proxy card are treated as present or represented for purposes of determining the presence or absence of a quorum at the special meeting. However, abstentions will have the same effect as votes against the merger and the agreement and plan of merger and the other proposals.

     The proxy statement/prospectus materials are being mailed on or about                     , 2003 to holders of record of WaveSmith’s capital stock as of                     , 2003. The principal executive office and mailing address of WaveSmith is 35 Nagog Park, Acton, MA 01720.

WHETHER OR NOT YOU PLAN TO ATTEND THE MEETING, PLEASE SIGN, DATE AND PROMPTLY RETURN THE ENCLOSED PROXY CARD, WHICH YOU MAY REVOKE AT ANY TIME PRIOR TO ITS USE.PROMPTLY SIGNING AND RETURNING YOUR PROXY CARD WILL HELP ENSURE THE PRESENCE OF A QUORUM FOR THE MEETING.A postage-paid, self-addressed envelope is enclosed for your convenience. Your shares will be voted at the meeting in accordance with your proxy.

	By orderOrder of the Board of Directors,

	Russell B. Stevenson, Jr.
	Senior Vice President, General Counsel and
	Secretary

ONI SYSTEMS CORP.

NOTICE OF THE SPECIAL MEETING OF STOCKHOLDERS

Time and Date		, local time, on             , 2002
Place
Item of Business		To consider and vote upon a proposal to approve and adopt the Agreement and Plan of Merger between CIENA Corporation and ONI Systems Corp. and approve the merger contemplated by the Agreement and Plan of Merger.
Adjournments and Postponements		Any action on the item described above may be considered at the special meeting at the time and on the date specified above or at any time and date to which the special meeting may properly be adjourned or postponed.
Record Date		You are entitled to vote only if you were an ONI Systems stockholder at the close of business on             , 2002.
Voting		Your vote is very important. Whether or not you plan to attend the special meeting, we encourage you to read this joint proxy statement/ prospectus and submit your proxy or voting instructions for the special meeting as soon as possible. You may submit your proxy or voting instructions for the special meeting by completing, signing, dating and returning the proxy card or voting instruction card in the pre-addressed envelope provided. For specific instructions on how to vote your shares, please refer to the section entitled “The Special Meeting of ONI Systems Stockholders” beginning on page      of this joint proxy statement/ prospectus and the instructions on the proxy card or voting instruction card.

	Thomas Burkardt, Chief Executive Officer
	By order of the Board of Directorsand President

	Michael A. Dillon
	Vice President, General Counsel and Secretary

TABLE OF CONTENTS

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     This joint proxy statement/prospectus incorporates important business and financial information about CIENA and ONI Systems from documents that each companyit has filed with the Securities and Exchange Commission but that have not been included in or delivered with this joint proxy statement/ prospectus. For a listing of documents incorporated by reference into this joint proxy statement/prospectus, please see the section entitled “Where You Can Find More Information” beginning on page 76 of this joint proxy statement/ prospectus.

     CIENA will provide you with copies of this information, relating to CIENA, without charge, upon written or oral request to:

CIENA Corporation

     In addition, you may obtain copies of this information by sending an e-mail to ir@ciena.com. A list of those stockholders entitled to vote at the special meeting will be available for inspection for ten days preceding the meeting at the address set forth above, and will also be available for inspection at the meeting itself.

     ONI Systems will provide you with copies of this information relating to ONI Systems, without charge, upon written or oral request to:

ONI Systems Corp.

     In addition, you may obtain copies of this information by sending an e-mail to ir@oni.com. A list of those stockholders entitled to vote at the special meeting will be available for inspection for ten days preceding the meeting at the address set forth above, and will also be available for inspection at the meeting itself.

In order for you to receive timely delivery of the documents in advance of the special meetings,meeting, CIENA or ONI Systems should receive your request no later than [date 5 business days prior to the meeting date].

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QUESTIONS AND ANSWERS ABOUT THE MERGER

Q:	Why am I receiving this joint proxy statement/ prospectus?
A:	CIENA and ONI Systems have agreed to combine their businesses under the terms of a merger agreement that is described in this joint proxy statement/ prospectus. A copy of the merger agreement is attached to this joint proxy statement/ prospectus as Annex A.
	In order to complete the merger, CIENA and ONI Systems stockholders must approve and adopt the merger agreement and approve the merger. Each of CIENA and ONI Systems will hold a special meeting of its respective stockholders to obtain these approvals. This joint proxy statement/ prospectus contains important information about the merger and the special meeting of each of CIENA and ONI Systems, and you should read it carefully. The enclosed voting materials for the special meeting allow you to vote your shares of common stock without attending the special meeting.
Q:	Why are CIENA and ONI Systems proposing the merger?
A:	We believe that the merger of ONI Systems and CIENA will create one of the leading optical networking equipment companies in the world. We believe that together we will be a stronger and more competitive company by expanding our product offerings and accessing each other’s customer relationships. For a complete description of CIENA’s and ONI Systems’ reasons for the merger, we encourage you to refer to pages                .
Q:	How do the boards of directors of CIENA and ONI Systems recommend that I vote?
A:	The CIENA board of directors recommends that CIENA stockholders vote “FOR” the proposal to approve and adopt the merger agreement and approve the merger.
	The ONI Systems board of directors recommends that ONI Systems stockholders vote “FOR” the proposal to approve and adopt the merger agreement and approve the merger.
	For a more complete description of the recommendations of the boards of directors of CIENA and ONI Systems, see “The Merger — Recommendation of CIENA’s Board of Directors and Reasons for the Merger” on page      and “The Merger — Recommendation of ONI Systems’ Board of Directors and Reasons for the Merger” on page      .
Q.	Have executive officers and directors of ONI Systems agreed to vote their shares in favor of the merger?
A.	Yes. The executive officers and directors of ONI Systems and their affiliates have agreed to vote shares representing approximately 11.5% of ONI Systems’ outstanding common stock as of February 17, 2002 in favor of the merger. See “Terms of the Merger Agreement and Related Transactions — Stockholder Agreements” on page      .
Q.	Are there risks that I should consider in deciding to vote for the merger?
A.	Yes. For example, the combined company might not realize the expected benefits of the merger. In evaluating the merger, you should carefully consider the factors discussed in “Risk Factors” on page      . You should also consider the risks associated with CIENA stock ownership and ONI Systems stock ownership which are incorporated by reference into this joint proxy statement/ prospectus. See “Where You Can Find More Information” on page      .
Q.	What will happen to CIENA and ONI Systems as a result of the merger?
A:	If the merger is completed, ONI Systems will merge into CIENA. The merged businesses will continue to be conducted under the CIENA name.
Q:	What will I receive in the merger?
A:	ONI Systems Stockholders: ONI Systems stockholders will receive 0.7104 shares of CIENA common stock for each share of ONI Systems common stock they now own. Instead of a fractional share of CIENA common stock, you will be entitled to receive an amount of cash equal to the value of the fractional share remaining after aggregating all of your ONI Systems shares held based on the closing price of CIENA common

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	stock on the closing date. After the merger, ONI Systems security holders will own approximately 24% of the outstanding shares of CIENA common stock on a fully diluted basis based on shares, options and warrants outstanding on February 17, 2002. For a more complete description of what you will receive in the merger, see “Terms of the Merger Agreement and Related Transactions — Treatment of Stock, Options and Warrants” on page      .
	CIENA Stockholders: A CIENA stockholder will continue with the same number of CIENA shares he or she now owns. These shares however, will represent a smaller proportion of the outstanding shares of the combined company.
Q:	What are the federal income tax consequences of the merger?
A:	In general, we expect that ONI Systems stockholders will not be required to pay federal income taxes as a result of exchanging ONI Systems shares for CIENA shares, except for taxes on any cash that is received in lieu of fractional shares. For a more complete description of the tax consequences of the merger, see “The Merger — Federal Income Tax Consequences” on page      .
Q:	When and where will the special meetingsmeeting take place?
A:	ONI Systems Stockholders:The special meeting will be held on                     , 2002,2003 at [9:00] a.m., local time, at                     .
	CIENA Stockholders: The special meeting will be held on                     , 2002, at            a.m., local time, at the BWI Marriott Hotel, 1743 W. Nursery Road, Linthicum, Maryland 21090.
Q:	If my shares are held in “street name” by my broker, will my broker vote my shares for me?
A:	Your broker will not be able to vote your shares unless you provide instructions on how to vote your shares. You should instruct your broker to vote your shares following the directions provided by your broker. Without instructions, your shares will not be voted and you will, in effect, be voting against the merger.
Q:	What happens if I do not vote?
A:	Failure to vote or to give voting instructions to your broker or nominee will have the same effect as voting “AGAINST” the proposal to approve and adopt the merger agreement and approve the merger. Therefore, we urge you to vote. For a more complete descriptionoffices of voting, see “The Special Meeting of CIENA Stockholders” on page      and “The Special Meeting of ONI Systems Stockholders” on page      .
Q:	When do CIENA and ONI Systems expect the merger to be completed?
A:	CIENA and ONI Systems are working to complete the merger as quickly as possible. We hope to complete the merger during the second or third calendar quarter of 2002. However, we cannot predict the exact timing of the completion of the merger because the merger is subject to government and regulatory review processes and other conditions.Testa, Hurwitz & Thibeault, LLP, 125 High Street, Boston, Massachusetts.
Q:	What do I need to do now?
A:	You should carefully read and consider the information contained in this joint proxy statement/prospectus. You should then complete and sign your proxy card and return it in the enclosed return envelope as soon as possible so that your shares will be represented at your company’sWaveSmith’s special meeting. If you sign, date and mail your proxy card without identifying how you want to vote, your proxy will be voted“FOR” the merger and“FOR” the grant of discretionary authority to adjourn the special meeting. If you do not vote, it will have the same effect as a vote“AGAINST” the proposals. You may also vote by appearing at the meeting and voting in person.
Q:	Who must approve the merger?
A:	In addition to the approvals of the boards of directors of CIENA and ONI SystemsWaveSmith which have already been obtained, the following approvals of the stockholders of ONI Systems and CIENAWaveSmith must also approve the merger. For a more complete description of voting, see “The Special Meeting of CIENA Stockholders” on page      and “The Special Meeting of ONI Systems Stockholders” on page      .
Q:	As an ONI Systems stockholder, will I be able to trade the CIENA common stock that I receive in connection with the merger?
A:	The shares of CIENA common stock you receive in the merger will be freely tradable, unless you are an affiliate of ONI Systems. The shares will be listed on the Nasdaq Stock Market under the symbol “CIEN.” Generally, persons who are deemed to beobtained:

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•	affiliatesholders of ONI Systems must comply with Rule 145 under the Securities Acta majority of 1933 if they wish to sell or otherwise transfer any of the shares of CIENAWaveSmith’s common stock received in connection with the merger. You will be notified if you are an affiliate of ONI Systems.and preferred stock, voting as a single class on as as-converted basis;
•	holders of a majority of WaveSmith’s series A and series A-1 preferred stock, voting together as a single class on an as-converted basis;
•	holders of 60% of WaveSmith’s series B and series B-1 preferred stock, voting together as a single class on an as-converted basis; and
•	holders of 75% of WaveSmith’s series C preferred stock, voting as a separate class on an as-converted basis.

Q:	Can I change my vote after I mail my signed proxy?
A:	Yes. You can change your vote at any time before your proxy is voted at the special meeting of your company’sWaveSmith’s stockholders. You can do this in one of three ways. First, you can send a written notice stating that you would like to revoke your proxy. Second, you can complete and submit a new proxy. If you choose either of these two methods, you must submit your notice of revocation or your new proxy for CIENA shares at the address on page and for ONI Systems shares at the address on page      .14. Third, you can attend the special meeting of your company’s stockholders and vote in person. Your attendance alone will not revoke your proxy. If you have instructed a broker to vote your shares, you must follow the directions received from your broker to change those instructions.
Q:	What is the required vote to approve and adopt the merger agreement and approve the merger?
A:	Approval and adoption of the merger agreement and approval of the merger requires the affirmative vote of the holders of a majority of the shares of each of CIENA common stock and ONI Systems common stock outstanding as of the record date.
Q:	Should I send in my certificates now?
A:	No, you should not send in your stock certificates with your proxy. You will receive instructions for exchanging your stock certificates if the merger is consummated.
Q:	Who can help answer my questions?
A:	If you have any questions about the merger, how to vote or revoke your proxy, or if you need additional copies of this joint proxy statement/prospectus or the enclosed proxy, you should contact:contact Gregg Savage, WaveSmith’s Chief Financial Officer and Secretary at (978) 489-2103.

ONI Systems:
[proxy solicitor]

CIENA Corporation:
Georgeson Shareholder Communications, Inc.

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SUMMARY

     This summary highlights selected information from this joint proxy statement/prospectus. It does not contain all of the information that is important to you. You should carefully read this joint proxy statement/prospectus and the other documents incorporated by reference into this joint proxy statement/prospectus. See “Where You Can Find More Information” on page      . In this joint proxy statement/prospectus, “we,” “us‘“us” and “our” may refer to either CIENA or ONI Systems,WaveSmith, depending on the context in which they are used, and “you”“you‘ and “your” refer to stockholders of ONI Systems or stockholders of CIENA, depending on the context in which they are used.WaveSmith.

The Companies (page )52)

CIENA Corporation

CIENA is a leader in the intelligent optical networking equipment industry. CIENA offers a portfolio of products for communicationssystems and software, offering telecommunications network solutions to service providers and enterprises worldwide. CIENA’s customers include long-distance carriers, competitive and incumbent local exchange carriers, Internet service providers, and wireless and wholesale carriers.carriers, systems integrators, governmental, large businesses and non-profit institutions. CIENA offers optical transport and intelligent optical switching systemsnetwork solutions that enable service providers to provision, manage and deliver economic, high-bandwidth services to their customers. CIENA has pursued a strategy to develop and leverage the power of disruptive technologies to change the fundamental economics of building carrier-class tele-and data-communications networks, thereby providing our customers with a competitive advantage. CIENA’s intelligent optical networking products are designed to enable carriers to deliver any time, any size, any priority bandwidth to their customers.

ONI Systems Corp.WaveSmith Networks, Inc.

ONI SystemsWaveSmith designs, develops and markets and sells optical communications networking equipment specificallya next generation multi-service switch platform designed to addressempower telecommunications carriers to cap their investments in aging technology, while they begin deploying next-generation platforms. In this way, WaveSmith’s products embrace carriers’ near-term, tactical requirements as well as their longer-term strategic visions. WaveSmith’s Distributed Node (DN^TM) multi-service switch platform is designed from the bandwidthground up to sustain and service limitationsleverage today’s layer 2 infrastructure while incorporating an evolutionary path to future technologies.

Vote Required (page 13)

Under Delaware law and WaveSmith’s certificate of metropolitan areaincorporation, the following stockholder approvals are required:

	•	holders of a majority of WaveSmith’s common stock and preferred stock, voting as a single class on as as-converted basis;
	•	holders of a majority of WaveSmith’s series A and series A-1 preferred stock, voting together as a single class on an as-converted basis;
	•	holders of 60% of WaveSmith’s series B and series B-1 preferred stock, voting together as a single class on an as-converted basis; and
	•	holders of 75% of WaveSmith’s series C preferred stock, voting as a separate class on an as-converted basis.

There were 79,787,626 shares of WaveSmith common stock and regional networks. Communications service providers can cost-effectively deploy ONI Systems’ products137,850,002 shares of WaveSmith preferred stock, comprised of 185,000 shares of WaveSmith series A preferred stock, 9,015,000 shares of WaveSmith series A-1 preferred stock, 2,353,370 shares of WaveSmith series B preferred stock, 33,333,331 shares of WaveSmith series B-1 preferred stock and 92,963,301 shares of WaveSmith series C preferred stock outstanding as of April 28, 2003. Each holder of WaveSmith common stock is entitled to relieve the traffic bottleneck in these networksone vote per share and offer new revenue-generating services including wavelength, private-line, ethernet and data storage services. By deploying ONI Systems’ equipment, service providers can rapidly build high-capacity flexible and scalable networks thateach holder of WaveSmith preferred stock is entitled to one vote for each full share of common stock into which its shares of preferred stock are able to support multiple services on a single platform from their central offices at the core of their networks to their customers’ sites at the edge of their networks. In addition, ONI Systems’ equipment can be introduced into a network without requiring complete replacementconvertible.

As of the existing network infrastructure.record date, WaveSmith’s officers and directors and their affiliates owned approximately 48.8% of WaveSmith’s outstanding common stock, 87.9% of WaveSmith’s outstanding series A and A-1 preferred stock on an as-converted basis, 81.0% of WaveSmith’s outstanding series B and B-1 preferred stock on an as-converted basis and 54.1% of WaveSmith’s outstanding series C preferred stock on an as-converted basis.

Several WaveSmith stockholders beneficially owning in the aggregate the following numbers of shares entered into agreements under which they agreed to vote their shares in favor of the merger and approval of the merger agreement:

	•	182,175,585 shares, representing 63.4% of WaveSmith’s common stock and preferred

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		stock, voting as a single class on as as-converted basis;
	•	28,203,689 shares, representing 87.9% of WaveSmith’s series A and series A-1 preferred stock, together on an as-converted basis;
	•	66,666,661 shares, representing 81.0% of WaveSmith’s series B and series B-1 preferred stock, together on an as-converted basis; and
	•	66,961,835 shares, representing 72.0% of WaveSmith’s series C preferred stock, as a separate class on an as-converted basis.

Additionally, CIENA’s wholly-owned subsidiary, MultiWave Investment, Inc., owns 16,666,667 shares of series C preferred stock, representing 17.9% of WaveSmith’s series C preferred stock, which it intends to vote in favor of the merger and approval of the merger agreement.

The Merger (page )16)

The merger agreement provides that ONI SystemsWaveSmith will merge with and into CIENA and CIENA will be the surviving company. CIENA and ONI Systems hope to complete the merger during the second or third calendar quarter of 2002.

The merger agreement is included as Annex A to this joint proxy statement/prospectus. It is the legal document that governs the merger. We cannot predict

Reasons for the exact timingMerger and Recommendation of the completionWaveSmith Board of the merger becauseDirectors (page 24)

The WaveSmith board of directors has determined that the merger is subjectadvisable and in the best interests of WaveSmith and its stockholders. The WaveSmith board of directors recommends that WaveSmith stockholders vote“FOR” the proposal to governmentapprove and regulatory review processesadopt the merger agreement and other conditions.approve the merger.

See “The Merger — Recommendation of the WaveSmith Board of Directors and Reasons for the Merger” for the reasons supporting the WaveSmith board of directors’ recommendations.

What You Will Receiveyou will receive in the Merger (page )35)

Each outstanding share of ONI Systems common stock will be cancelled and each ONI Systems stockholderIn the merger, you will receive 0.7104 sharesa fraction of a share of CIENA common stock for each share of ONI SystemsWaveSmith common stock or preferred stock that you own, in each case as determined by application of the stockholder owns. An ONI Systems stockholderformulas set forth under “Terms of the Merger Agreement and Related Transactions — Treatment of Stock, Options and Warrants.” You will also receive a cash payment for any fraction of afractional share of CIENA common stock that the stockholderyou would otherwise receive in the merger.

The formulas by which the number of shares of CIENA common stock to be entitledreceived for each share of WaveSmith capital stock are fixed. The number of shares of CIENA common stock to be received for each share of WaveSmith capital stock is subject to adjustment only in the event that WaveSmith’s fully-diluted outstanding capital stock changes due to option issuances, stock repurchases and similar events. Any issuance of WaveSmith capital stock due to the exercise of options or warrants currently outstanding will not affect the exchange ratios, as they are calculated on a fully-diluted, or fully-exercised, basis. WaveSmith stockholders will not know the value of the CIENA common stock they will receive in the merger when the special meeting of the WaveSmith stockholders is held. The value of the CIENA common stock will depend upon its market price when the merger is completed. The number of shares of CIENA common stock received will depend upon the number of shares of WaveSmith capital stock outstanding on the day the merger is completed.

For example, if the total number of shares of WaveSmith capital stock outstanding on a fully-diluted basis on the day the merger is completed is 291,698,422, which is the number of shares of capital stock outstanding on a fully-diluted basis on the record date, the following exchange ratios, rounded to the nearest ten thousandth, would apply:

The following chart gives a few examples of the number of shares of CIENA common stock that a holder of 100 shares of WaveSmith common stock would receive in the merger, assuming the application of the exchange ratio from the above table, and the value of those shares at a range of prices of CIENA common stock. The chart does not include cash received for fractional shares or cash paid in respect of dissenting shares.

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At the earliest practicable date after the completion of the merger, you will receive a letter of transmittal that will provide instructions on the procedure for exchanging your share certificates. For more information on how the election and exchange procedures work, seeSee “Terms of the Merger Agreement and Related Transactions — Exchange of Certificates; Fractional Shares” on page .36.

Please do not send your stock certificates at this time.

ONI Systems Employee Stock OptionsTotal Consideration CIENA Will Pay

Each outstanding option to purchaseAt the effective time of the merger, CIENA will issue approximately 35,407,695 shares of ONI Systemsits common stock in exchange for all WaveSmith outstanding common and preferred stock, including shares of series C preferred stock owned by MultiWave Investment, Inc. As of April 25, 2003, these shares have an aggregate value of approximately $149 million. Additionally, CIENA will assume the obligation to issue an additional approximately 639,803 shares of CIENA common stock on the exercise of outstanding options and warrants. This assumes that the number of shares of WaveSmith’s capital stock outstanding on a fully-diluted basis on the day the merger is completed is 291,698,422.

Appraisal Rights of Dissenting Stockholders (page 32)

If you object to the merger, Delaware law permits you to seek relief as a dissenting stockholder and have the “fair value” of your shares of WaveSmith common stock and WaveSmith preferred stock determined by a court and paid to you in cash.

If you are a WaveSmith stockholder and wish to dissent, you must deliver to WaveSmith, prior to the vote on the merger at the special meeting, a written demand for appraisal of your shares. You also must not vote in favor of the merger agreement. To not vote in favor of the merger agreement, you can either:

	•	vote “no” in person at the special meeting or by proxy;
	•	abstain from voting;
	•	fail to vote; or
	•	if you returned a duly executed proxy and revoke your proxy prior to the special meeting.

Beneficial owners of WaveSmith common stock or WaveSmith preferred stock whose shares are held of record by another person, such as a bank, broker or nominee, and who wish to seek appraisal, should instruct the record holder to follow the appraisal procedures of Delaware law. The relevant provisions of Delaware law are technical in nature and complex. If you wish to exercise appraisal rights and obtain appraisal of the fair value of your shares, you may wish to consult with legal counsel, because the failure to comply strictly with these provisions may result in waiver or forfeiture of your appraisal rights.

A copy of the relevant section of Delaware law governing this process is attached as Annex B to this prospectus and proxy statement.

Indemnification and Escrow Agreement (page 42)

If the merger occurs, all holder of WaveSmith capital stock who have not elected the appraisal rights described above, will be converted into an optionobligated to purchase aindemnify CIENA and its affiliates against losses due to, among other things, the breach or inaccuracy of any of WaveSmith’s representations and warranties made in the merger agreement. This obligation is limited to 10% of the total number of shares of CIENA common stock equalissued in the merger to holders of outstanding WaveSmith capital stock and 10% of the total number of shares of ONI SystemsCIENA common stock which is allocable to vested WaveSmith options which are assumed in the merger. An escrow arrangement will be established at closing to hold these amounts. Michael Feinstein, who is a member of WaveSmith’s board of directors and a senior principal of Atlas Venture will serve as Stockholder Representative on behalf of all former WaveSmith stockholders. Investment funds affiliated with Atlas Venture are significant stockholders of WaveSmith. See “Security Ownership of Directors, Executive Officers and More Than Five Percent Stockholders of WaveSmith.” The escrow

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Consequently, in some circumstances you could be required to forfeit to CIENA some of the CIENA common stock you would otherwise receive in the merger.

What is Needed to Complete the Merger (page )43)

Several conditions must be satisfied before the merger will be completed. These include:

	•	adoption of the merger agreement and approval ofby the merger byWaveSmith stockholders representing a majority of the outstanding shares of each of ONI Systems and CIENA;as described above;
	•	the waiting period under the Hart-Scott-Rodino Antitrust Improvement Act of 1976 must have expired or been terminated;
	•	receipt by ONI Systems of an opinion of its tax counsel that, for U.S. federal income tax purposes, the merger is generally not taxable to ONI Systems or its stockholders;
	•	receipt by CIENA of an opinion of its tax counsel that, for U.S. federal income tax purposes, the merger is generally not taxable to CIENA or its stockholders; and
	•	other customary contractual conditions set forth in the merger agreement.

If the law permits, CIENA or ONI SystemsWaveSmith may each waive conditions for the benefit of theirits company and stockholders and complete the merger even though one or more of these conditions has not been met. WaveSmith’s stockholder approval cannot be waived. If a material condition is waived by WaveSmith, we will resolicit the vote of its stockholders. We cannot assure you that the conditions will be satisfied or waived or that the merger will occur.

Federal Income Tax Consequences (page      )

The merger is intended to qualify as a reorganization under Section 368(a) of the Internal Revenue Code. CIENA and ONI Systems have respectively received opinions of Hogan & Hartson L.L.P. and Fenwick & West LLP that the merger will qualify as a reorganization if the merger takes place as described in the merger agreement. The opinions are based upon the assumption that factual representations made by CIENA and ONI Systems, which are ordinarily given in transactions of this type, will be correct when the merger closes. If the merger qualifies as a reorganization, no gain or loss will be recognized by CIENA or ONI Systems stockholders as a result of the merger, except with respect to cash received by ONI Systems stockholders in lieu of fractional shares. For a further discussion of the federal income tax consequences of the merger to CIENA and ONI Systems stockholders, see “The Merger — Federal Income Tax Consequences.” However, different tax consequences may apply to you because of your individual circumstances or because special tax rules apply to you, for example, if you:

	•	are a tax-exempt organization;
	•	are a dealer in securities;
	•	are a financial institution;
	•	are an insurance company;
	•	are a non-United States person;
	•	acquired your shares of ONI Systems stock from the exercise of options or otherwise as compensation or through a qualified retirement plan; or
	•	hold shares of ONI Systems stock as part of a straddle, hedge or conversion transaction.

These matters are very complicated. You should consult your tax advisor for a full explanation of the tax consequences of the merger to you.

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Accounting Treatment (page      )

CIENA will account for the merger using the purchase method of accounting.

Governmental and Regulatory Approvals (page      )

Under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, CIENA and ONI Systems must notify U.S. antitrust authorities of the proposed merger and must observe a waiting period before it can be completed. Therefore, the merger cannot occur until this waiting period has expired or has been terminated by the antitrust authorities. In addition, foreign, state and other regulatory authorities may also need to approve or be notified of the merger before it can be completed. CIENA and ONI Systems have filed, or expect soon to file, all of the required applications or notices with these regulatory authorities. While neither CIENA nor ONI Systems knows of any reason why we would not be able to obtain the necessary approvals in a timely manner, we cannot be certain when or if we will receive them.

Termination of the Merger Agreement; Expenses (page )45)

CIENA and ONI SystemsWaveSmith may mutually agree at any time to terminate the merger agreement without completing the merger, even if the ONI Systems or CIENAWaveSmith stockholders have approved it. Either party (so long as it has not materially breached the merger agreement) may terminate the merger if:

	•	the merger has not been consummated by September 30, 2002;August 15, 2003, or, if extended by CIENA under certain conditions, October 15, 2003;
	•	ONI Systems or CIENAWaveSmith stockholders do not approve the merger; or
	•	if a court forbids the merger to occur.

ONI SystemsWaveSmith may terminate the merger agreement prior to obtaining stockholder approval, ifso long as it has not materially breached the ONI Systems board of directors determines to enter into an alternative transaction that it views as superior or if CIENA’s board of directors changes its recommendation to stockholders in favor of the merger. merger agreement, if:

	•	the WaveSmith board of directors determines to enter into an alternative transaction that it views as superior to the merger, and
	•	CIENA does not match the offer made in the other transaction.

CIENA may similarlyalso terminate the merger agreement if ONI Systems’WaveSmith’s board of directors withdraws, modifies or amends, in any respect adverse to CIENA, its recommendation to stockholders in favor of the merger. ONI Systemsmerger or determines to pursue another transaction it considers superior.

WaveSmith has agreed to pay CIENA a termination fee of $36.7$5.1 million if the merger agreement is terminated becauseunder either of a change in ONI Systems’ board of directors recommendation (unless due to a material adverse effect on CIENA) orthese circumstances and specified other circumstances if ONI Systems accepts an alternative superior proposal. ONI Systems would also be required to pay this termination fee if there is a change in ONI Systems’ board of directors recommendation and CIENA terminates the agreement, or ONI Systems’ stockholders do not approve the merger, and there is a publicly announced third party has made an offer to acquire ONI Systems, which ONI Systems accepts within 12 months of the termination.WaveSmith. The merger agreement also requires ONI SystemsWaveSmith to reimburse CIENA for CIENA’sits out-of-pocket expenses, up to a maximum of $2 million,$500,000, in those situations where the termination fee is payable.

Further, under a letter agreement entered into by CIENA, agreed to pay ONI SystemsWaveSmith and MultiWave Investment,

No Solicitation by ONI Systems (page      )In the event that:

Under the merger agreement, ONI Systems agreed not to solicit, enter into, negotiate or participate in discussions regarding an “acquisition proposal” directly or indirectly, as described further on page      . However, this provision does not prohibit ONI Systems from providing information or entering into negotiations with a person in response to an unsolicited written bona fide acquisition proposal if ONI Systems’

	•	CIENA terminates the merger agreement for reasons other than because the WaveSmith board of directors determines in good faith that the acquisition proposal is reasonably likely to be consummated, the proposal if consummated would result in a transaction that is more favorable to ONI Systems stockholders than the merger with CIENA and that taking that action is necessary to fulfil its fiduciary duties to stockholders. ONI Systems has agreed to inform CIENA promptly of directors determined to enter into an alternative transaction that it views as superior to the merger;
	•	WaveSmith terminates the merger agreement because the August 15 or October 15 expiration date occurs, stockholder approval is not obtained or an order of a court prevents completion of this transaction; or

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Restrictions on Resales of CIENA Common Stock (page      )

All shares of CIENA common stock to be issued to ONI Systems stockholders in the merger will be freely tradable, unless the holder is considered an affiliate of ONI Systems, and will be listed on the Nasdaq Stock Market under the symbol “CIEN.”

Waiver and Amendment (page      )

     CIENA and ONI Systems may agree to amend the merger agreement prior to the time the merger becomes effective, subject to applicable law. Either of us can waive our right to require the other party to adhere to the terms and conditions of the merger agreement, if the law allows, at any time prior to the time the merger becomes effective.

Interests of ONI Systems’ Executive Officers and Directors in the Merger (page      )

In considering the recommendation of the ONI Systems board of directors about the merger, you should be aware of the interests which executive officers and directors of ONI Systems have in the merger that are different from your and their interests as stockholders. William Cumpston and Rohit Sharma have entered into employment agreements with CIENA. Hugh Martin has entered into a consulting agreement with CIENA. Contemporaneously with the approval of the merger agreement, the ONI Systems board of directors approved the grant of options to purchase 750,000 and 550,000 shares of ONI Systems common stock to Messrs. Cumpston and Sharma, respectively. The exercise price of these options is $5.21, the fair market value of ONI Systems common stock on February 21, 2001. The merger agreement requires CIENA to indemnify directors and officers of ONI Systems for events occurring before the merger, including events that are related to the merger. The ONI Systems board of directors recognized all those interests described above and concluded that those interests did not detract from the fairness of the merger to the stockholders of ONI Systems who are not executive officers or directors of ONI Systems.

Reasons for the Merger and Recommendation of the CIENA Board of Directors (page      )

THE CIENA BOARD OF DIRECTORS RECOMMENDS THAT CIENA STOCKHOLDERS VOTE“FOR” THE PROPOSAL TO APPROVE AND ADOPT THE MERGER AGREEMENT AND APPROVE THE MERGER.

The CIENA board of directors has determined that the merger is advisable and in the best interests of CIENA and its stockholders. The CIENA board of directors made this determination based on its review of:

	•	the potential strategic benefitsmerger agreement is terminated by either party because the waiting period under the Hart-Scott-Rodino Antitrust Improvement Act of the merger, including (among other things) the complementary nature of the technologies and products of CIENA and ONI Systems; the advantages of combining their respective management, sales forces and technical teams; and the prospect of an improved competitive and market position of the combined company.
	•	the potential financial implications of the merger, including (among other things) CIENA’s management’s views as to the business, results of operations and financial condition, technology, management and competitive position of CIENA and ONI Systems; potential cost savings and synergies; current and prospective financial market and commercial conditions; and the opinion of Morgan Stanley referred to below.
	•	the potential adverse effects of the merger, including (among other things) the risk that the potential benefits of the merger might1976 has not be realized; risks relating to integrating the businesses; the possibility of management and employee disruption; and the potential disruption of customer relationships.expired or been terminated,

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Thethen, the reseller agreement between CIENA boardand WaveSmith, the letter agreement referred to above between CIENA, MultiWave Investment, Inc. and WaveSmith and the agreements CIENA has with several holders of directors did not quantify or assign relative weight to the factors summarized above. For a more complete discussion of the CIENA board of directors’ reasons for the merger, see “The Merger — Recommendation of CIENA’s Board of Directors and Reasons for the Merger” beginning on page      of this joint proxy statement/ prospectus.WaveSmith capital stock will also terminate.

Reasons for the Merger and Recommendation of the ONI Systems Board of Directors (page      )WS Contract Corp. into WaveSmith

THE ONI SYSTEMS BOARD OF DIRECTORS RECOMMENDS THAT ONI SYSTEMS STOCKHOLDERS VOTE“FOR” THE PROPOSAL TO APPROVE AND ADOPT THE MERGER AGREEMENT AND APPROVE THE MERGER.

The ONI Systems boardAs part of directors has determined that the merger is advisable and innegotiations of the best interests of ONI Systems and its stockholders. The ONI Systems board of directors made this determination and its determination to recommend approvalterms of the merger based on its review of:

	•	the potential strategic benefits of the merger, including (among other things) the complementary nature of the technologies and products of CIENA and ONI Systems; the advantages of combining their respective management, sales forces and technical teams; and the prospect of an improved competitive and market position of the combined company.
	•	the potential financial implications of the merger, including (among other things) ONI Systems’ management’s views as to the business, results of operations and financial condition, technology, management and competitive position of CIENA and ONI Systems; potential cost savings and synergies; CIENA’s pre-announcement of its anticipated financial condition and results of operations; current and prospective financial market and commercial conditions; possible alternative transactions; and the opinions of Goldman Sachs referred to below.
	•	the potential adverse effects of the merger, including (among other things) the riskof WaveSmith into CIENA, WaveSmith and CIENA agreed that the potential benefits of the merger might not be realized; risks relating to integrating the businesses; the possibility of management and employee disruption; and the potential disruption of customer relationships.

The ONI Systems board of directors did not quantify or assign relative weight to the factors summarized above. For a more complete discussion of the ONI Systems board of directors’ reasons for the merger, see “The Merger — Recommendation of the ONI Systems Board of Directors and Reasons for the Merger” beginning on page      of this joint proxy statement/ prospectus.

Opinion of CIENA’s Financial Advisor (page      )

On February 15, 2002, Morgan Stanley delivered its oral opinion to the CIENA board of directors, subsequently confirmed in writing, that,stock to be issued as of February 15, 2002, the exchange ratio pursuant to the merger agreement was fair to CIENA from a financial point of view. The full text of Morgan Stanley’s opinion, which identifies assumptions made, matters considered and limitations on the review undertakenconsideration in connection with the opinion, is attached as Annex Dmerger should be distributed in a manner that differed from the results obtained under the existing charter documents of WaveSmith. The distribution agreed upon by the parties resulted in a greater number of shares being allocated to this joint proxy statement/ prospectus.the holders of WaveSmith common stock. Stockholders of WaveSmith have approved the merger of WS Contract Corp. into WaveSmith and the related changes to the charter documents of WaveSmith immediately prior to the merger of WaveSmith into CIENA are urged to implement this change. The changes to the WaveSmith charter documents reduces the preference amounts for each series of preferred stock of WaveSmith as follows:

See “Terms of the Merger Agreement and should, read thisRelated Transactions — Merger of WS Contract Corp. into WaveSmith.”

Federal Income Tax Consequences (page 28)

In the opinion in its entirety. Morgan Stanley’s opinion does not constituteof Hogan & Hartson L.L.P., counsel to CIENA, and Testa, Hurwitz & Thibeault, LLP, counsel to WaveSmith, the merger will qualify as a recommendation astax-free reorganization. As a general matter, therefore, no gain or loss will be recognized by WaveSmith stockholders on the exchange of their WaveSmith capital stock for CIENA common stock pursuant to how any shareholder of CIENA should votethe reorganization, except with respect to the merger.

Opinioncash received in lieu of ONI Systems’ Financial Advisor (page      )

On February 15, 2002, Goldman Sachs proferred its oral opinionfractional shares and cash received in exchange of WaveSmith shares by WaveSmith stockholders who dissent to the boardmerger. There is an exception to the general tax-free treatment, however, resulting from the merger of directorsWS Contract Corp. into WaveSmith immediately prior to the merger of ONI Systems, which opinion was subsequently confirmed in writing on February 17, 2002 that, asWaveSmith into CIENA. This transaction will cause the value of the date of that opinion, the exchange ratio of 0.7104 shares of CIENAWaveSmith common stock to be received for each shareincreased, resulting in WaveSmith common stockholders receiving a greater number of ONI Systemsshares of CIENA common stock pursuant to the merger agreement was fairthan such stockholders would have received if the merger of WS Contract Corp. into WaveSmith had not occurred. Although the matter is not free from a financial point of viewdoubt, CIENA and WaveSmith believe that this additional value should be taxed to the holders of shares of ONI SystemsWaveSmith common stock. In addition, on March 18, 2002, at the requeststockholders as ordinary income. For a further discussion of the boardfederal income tax consequences of directorsthese transactions, see “The Merger — Federal Income Tax Consequences.” Different tax consequences may apply to you because of ONI Systems, Goldman Sachs delivered its opinionyour individual circumstances or because special tax rules apply to the board of directors of ONI Systems that, asyou.

These matters are very complicated. You should consult your tax advisor for a full explanation of the date of that opinion, the exchange ratio was fair from a financial point of view to the holders of shares of ONI Systems common stock, which opinion was subsequently confirmed in writing by means of an opinion letter dated as of March 18, 2002. The full text of the written opinion of Goldman Sachs dated March 18, 2002, which identifies assumptions made, matters considered and limitations on

5

Differences in the Rights of Stockholders (page      )

If you own ONI Systems common stock and receive CIENA common stock in the merger you would become a stockholder of CIENA upon completion of the merger. Your rights would continue to be governed by Delaware law but your rights would be governed by CIENA’s certificate of incorporation, bylaws and stockholder rights plan, rather than ONI Systems’ certificate of incorporation and bylaws. Your rights as a stockholder of CIENA would differ from your rights as a stockholder of ONI Systems. To review these differences in more detail, see “CIENA Capital Stock and Comparison of Stockholder Rights” on page      .

Special Meeting of CIENA Stockholders (page      )

The special meeting will be held on                          , 2002 at      a.m. at the BWI Marriott Hotel, 1743 W. Nursery Road, Linthicum, Maryland 21090. At the special meeting, you will be asked to vote to adopt the merger agreement and to approve the merger.

You can vote, or submit a proxy to vote, at the special meeting if you were a record holder of CIENA common stock at the close of business on                          , 2002. You can vote your shares by attending the meeting and voting in person or you can mark the enclosed proxy card with your vote, sign it and mail it in the enclosed return envelope. You can revoke your proxy at any time before it is exercised.

Special Meeting of ONI Systems Stockholders (page      )

The special meeting will be held on                          , 2002 at      a.m. at                . At the special meeting, you will be asked to vote to adopt the merger agreement and to approve the merger.

You can vote, or submit a proxy to vote, at the special meeting if you were a record holder of ONI Systems common stock at the close of business on                          , 2002. You can vote your shares by attending the meeting and voting in person or you can mark the enclosed proxy card with your vote, sign it and mail it in the enclosed return envelope. You can revoke your proxy at any time before it is exercised.

Vote Required (page      )

Holders of a majority of the outstanding shares of CIENA common stock must vote in favor of adoptiontax consequences of the merger agreement before the merger can occur. There were           shares of CIENA common stock outstanding as of                . Each holder of CIENA common stock is entitled to one vote per share. CIENA’s officers, directors and their affiliates owned      % of CIENA’s outstanding stock as of the record date.

Holders of a majority of the outstanding shares of ONI Systems common stock must vote in favor of adoption of the merger agreement before the merger can occur. There were                shares of ONI Systems common stock outstanding as of                          , 2002. Each holder of ONI Systems common stock is entitled to one vote per share. ONI Systems’ officers, directors and their affiliates owned      % of ONI Systems’ outstanding stock as of the record date.

Neither CIENA nor ONI Systems stockholders are entitled to dissenters’ rights of appraisal for their shares under the Delaware General Corporation Law in connection with the merger.

Stockholder Agreements (page      )you.

In connection with the merger agreement, several executive officers and directors of ONI Systems and their affiliates owning in the aggregate                shares of ONI Systems common stock, representing approximately 11.5% of the outstanding ONI Systems’ common stock as of the record date, entered into agreements under which they agreed to vote their shares in favor of the merger. The form of this stockholder agreement is attached as Annex B to this joint proxy statement/ prospectus.

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SUMMARY SELECTED CONSOLIDATED HISTORICAL FINANCIAL DATA

Summary Selected Consolidated Historical Financial Data of CIENA

     The information in the following summary selected consolidated financial data as of October 31, 1997, 1998, 1999, 2000, 2001 and 20012002 and for the years ended October 31, 1997, 1998, 1999, 2000, 2001 and 20012002 is derived from CIENA’s audited consolidated financial statements. You should read this information in conjunction with the financial statements and notes to the consolidated financial statements which are incorporated by reference into this joint proxy statement/prospectus. See “Where You Can Find More Information” which begins on page .76. CIENA’s financial statements as of October 31, 20002001 and 20012002 and for each of the three years ended October 31, 20012002 were audited by PricewaterhouseCoopers LLP, independent accountants. Selected financial information as of January 31, 20012002 and 20022003 and for the three months then ended is derived from CIENA’s unaudited consolidated financial statements, which are incorporated into this joint proxy statement/prospectus by reference. CIENA has a 52 or 53 week fiscal year, which ends on the Saturday nearest to the last day of October in each year. For purposes of financial statement presentation, each fiscal year is described as having ended on October 31. Fiscal 1997, 1998, 1999, 2000 and 20002002 comprised 52 weeks and fiscal 2001 comprised 53 weeks. Historical events are not necessarily indicative of results to be expected in the future and results of interim periods are not necessarily indicative of the results of the entire year.

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     Significant events affecting CIENA’s operating trends.The comparability of CIENA’s operating results is affected by a number of significant and nonrecurring items recognized in some periods as well as acquisitions. In fiscal 1997, CIENA incurred special charges of $7.5 million related to the Pirelli litigation. In fiscal 1998, CIENA incurred special charges of $30.6 million related to the Pirelli litigation, $2.6 million of merger related costs associated with an unsuccessfulthe contemplated merger with Tellabs and $9.5 million in-process research and development charge associated with the acquisition of Terabit Technologies.Technology. In fiscal 1999, CIENA incurred $13.0 million of merger related costs associated with Omniathe purchase of Lightera and Lightera.Omnia. In fiscal 2000, CIENA incurred $28.0 million of additional provision for doubtful accounts associated with the write-off of customer receivables. In fiscal 2001, CIENA recorded a goodwill impairment of $1,719.4 million related to the Cyras acquisition, an in-process research and development charge of $45.9 million in connection with the Cyras acquisition, and restructuring costs to close facilities and terminate employees of $15.4 million. In fiscal 2002, CIENA consummated the acquisitionrecorded a $286.5 million provision for excess and obsolete inventory, $225.4 million for restructuring costs to close facilities, dispose of Cyras Systems, Inc. on March 29, 2001.certain excess equipment and terminate employees, and $557.3 million related to goodwill impairment. During the three months ended January 31, 2002, CIENA recorded $6.8 million of restructuring costs associated with exiting facilities and terminating employees. The operating results have been significantly impacted by the acquisitions of Lightera and Omnia in 1999, Cyras Systems in 2001 and ONI Systems in 2002.

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Summary Selected Consolidated Historical Financial Data of ONI SystemsRISK FACTORS

     The informationIn addition to the risks described in CIENA’s most recently filed Form 10-Q, you should carefully consider the following summary selected consolidated financial data is derived from ONI Systems’ audited consolidated financial statements.risk factors relating to the merger before deciding how to vote your shares. You should read thisalso consider the other information contained in conjunction with the financial statements and notes to the consolidated financial statements which areor incorporated by reference into, this joint proxy statement/prospectus. See “Where You Can Find More Information” which begins on page . ONI Systems’ financial statements as of December 31, 2000 and 2001 and for each76.

The value of the three years ended December 31, 2001 were auditedCIENA common stock that WaveSmith stockholders receive in the merger will depend on its market price at the time of the merger, and no adjustment will be made if that market price declines.

     The value of CIENA common stock that WaveSmith stockholders will receive in the merger depends on the market price of CIENA common stock. The market price of CIENA common Stock may decline, causing the value of the consideration received by KPMG LLP, independent accountants.WaveSmith stockholders in the merger to decline. The historical results aremarket price of CIENA common stock is extremely volatile and has fluctuated over a wide range. From                     , 2002 to April      , 2003, CIENA common stock traded as high as $          per share and as low as $               per share. From April 8, 2003, the last trading day prior to the date on which the merger was announced, through April      , 2003, the price of CIENA common stock has increased approximately        %. The market price of CIENA common stock may continue to fluctuate significantly in response to various factors, including:

	•	quarterly variations in operating results principally due to customer purchasing decisions;
	•	changes in estimates by securities analysts;
	•	continued low levels in capital spending by customers; and
	•	general economic conditions.

Neither company can terminate the merger due to fluctuations in CIENA’s stock price.

     Neither party has the right to terminate the merger due to increases or decreases in CIENA’s stock price, even if those fluctuations would materially affect the value of the consideration WaveSmith stockholders will receive in the merger. CIENA has agreed to issue approximately 36,047,498 shares of CIENA common stock for all of WaveSmith outstanding capital stock, including the assumption of outstanding options to acquire WaveSmith stock. This represented a value of approximately $170 million on April 8, 2003, based on a per share price for CIENA common stock of $4.716, which is the average of the per share prices for CIENA’s common stock for the last five trading days prior to the date on which the merger was announced. This amount, however, includes approximately 2,430,508 shares issuable in respect of shares of WaveSmith series C preferred stock that CIENA already owns.

     If the price for CIENA common stock increases, CIENA would not necessarily indicativebe able to terminate the merger, even though it would be paying significantly more for WaveSmith. If the price of resultsCIENA common stock decreases, WaveSmith would not be able to terminate the merger, even though its stockholders would receive less value for their shares of WaveSmith. The value of the aggregate consideration to be expectedreceived by WaveSmith stockholders was calculated on April 9, 2003, the date the merger agreement was executed, using the average closing price for any future period.