As filed with the Securities and Exchange Commission on October 10, 2003May 21, 2004

Registration No. 333-108019333-115211

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

AMENDMENT NO. 21

TO

FORM S-4

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

TELLIUM,ZHONE TECHNOLOGIES, INC.

(Exact name of registrant as specified in its charter)

2 Crescent Place7001 Oakport Street

Oceanport, New Jersey 07757-0901Oakland, California 94621

(732) 923-4100(510) 777-7000

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Harry J. CarrMorteza Ejabat

Chief Executive Officer

Tellium,Zhone Technologies, Inc.

2 Crescent Place7001 Oakport Street

Oceanport, New Jersey 07757-0901Oakland, California 94621

(732) 923-4100(510) 777-7000

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public:    As soon as practicable after the effectiveness of this registration statement and the satisfaction or waiver of all other conditions under the merger agreement described herein.

If the securities being registered on this form are to be offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box.¨

If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act of 1933, check the following box and list the Securities Act of 1933 registration statement number of the earlier effective registration statement for the same offering.¨

If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act of 1933, check the following box and list the Securities Act of 1933 registration statement number of the earlier effective registration statement for the same offering.¨

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 that 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 Securities and Exchange 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. TelliumZhone 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 nor the solicitation of an offer to buy these securities in any state where the offer or sale is not permitted.

Subject to Completion, dated October 10, 2003May 21, 2004

MERGER PROPOSED—YOUR VOTE IS VERY IMPORTANT

Tellium, Inc.On behalf of the boards of directors and management teams of both Zhone Technologies, Inc. have agreedand Sorrento Networks Corporation, we are pleased to a combination ofdeliver our joint proxy statement/prospectus for the two companies under the terms of aproposed merger agreement. Telliuminvolving Zhone and Zhone are proposing the merger because theySorrento. We believe that the merger will provide substantial strategic and financial benefits to the stockholders of both companies.

Upon completion of the merger, ZhoneSorrento stockholders will be entitledhave the right to receive 0.9 of a certain numbershare of shares of TelliumZhone common stock for each share of ZhoneSorrento common stock owned as of the effective time of the merger. The number of shares of Tellium common stock to be issued with respect to each share of Zhone common stock will be determined by a formula described in the merger agreement and this joint proxy statement/prospectus. The formula will result in the holders of Zhone’s outstanding stock, options and warrants receiving 60% of the shares of the combined company on a fully converted basis and the holders of Tellium’s outstanding stock, options and warrants retaining 40% of the combined company.

Based on the capitalization of Tellium and Zhone as of the date of this joint proxy statement/prospectus, we estimate that the exchange ratio will be approximately             , which means that each share of Zhone common stock will convert, at the time of the merger, into              shares of Tellium common stock. The exchange ratio will be adjusted proportionately in the event that a reverse split of Tellium’s common stock, approved by Tellium’s stockholders at its last annual meeting of stockholders, is implemented by Tellium’s board of directorsheld immediately prior to the merger. We expect that a reverse split of Tellium’s common stock will be implemented prior to the merger according to a ratio between (and including) one-for-ten and one-for-four.

All shares of Zhone preferred stock will be converted into shares of Zhone common stock immediately prior to the merger on a one for one basis. Accordingly, Zhone preferred stockholders and Zhone common stockholders will receive the same per share consideration in the merger. Stockholders of Tellium will continue to own their existing shares.Zhone common stock.

Based on the estimated exchange ratio of approximately             , we estimate that, on a pre-reverse split basis, Tellium will issue approximately              million shares of Tellium common stock in the merger and reserve an additional approximately              million shares of Tellium common stock for future issuance in connection with Tellium’s assumption of Zhone’s outstanding options and warrants (including out-of-the-money options and warrants).

Tellium’sZhone common stock is traded on the Nasdaq SmallCapNational Market under the trading symbol “TELM.“ZHNE.” Sorrento common stock is traded on the Nasdaq National Market under the trading symbol “FIBR.” On October 9, 2003,April 22, 2004, the last sale pricetrading day before we announced the merger, the closing sales prices of Tellium’sZhone common stock was $1.35 per share,and Sorrento common stock as reported on the Nasdaq SmallCap Market.

Following the merger, the combined company will be namedNational Market were $3.89 and $2.67, respectively. The closing sales prices of Zhone Technologies, Inc., and it is anticipated that the combined company will trade on Nasdaq under the ticker symbol “ZHNE.” Since Nasdaq has deemed the merger a reverse merger of Tellium, Tellium has submitted an initial listing application and must satisfy Nasdaq’s initial listing criteria.

The merger cannot be completed unless Tellium’s stockholders approve the issuance of shares of Tellium common stock pursuant toand Sorrento common stock as reported on the merger agreement and Zhone’s stockholders adoptNasdaq National Market on May 20, 2004, the merger agreement. The obligationslast practicable trading day before the distribution of Tellium and Zhone to complete the merger are also subject to the satisfaction or waiver of several conditions. More information about Tellium, Zhone and the merger is contained in this joint proxy statement/prospectus.We encourage you to read this joint proxy statement/prospectus, includingwere $3.27 and $2.85, respectively. Upon completion of the section entitled “Risk Factors” beginningmerger, Sorrento will be a wholly owned subsidiary of Zhone and Zhone’s shares will continue to trade on page 20, before voting.the Nasdaq National Market under the trading symbol “ZHNE.”

The board of directors of Tellium has unanimously approvedZhone and Sorrento cannot complete the merger agreementunless the stockholders of both of our companies approve it. Zhone and the issuanceSorrento will each hold a special meeting of shares of Tellium common stock pursuantits stockholders to thevote on this merger agreement.proposal. The board of directors of Zhone has

approved the merger agreement. Tellium’s board of directors unanimously recommends that Tellium stockholders vote“FOR” the proposal to issue shares of Tellium’s common stock pursuant to the merger agreement. Zhone’s board of directors unanimously recommends that Zhone stockholders vote“FOR” the proposal to issue shares of Zhone common stock pursuant to the merger agreement. The Sorrento board of directors unanimously recommends that Sorrento stockholders vote“FOR” the proposal to adopt the merger agreement.

Tellium and Zhone have each scheduled a stockholders meeting in connection with the respective votes required. Your vote is very important. Whether or not you plan to attend your respective company’sthe special meeting of stockholders meeting,of Zhone or Sorrento, please take the time to vote by marking your votes oncompleting and mailing the enclosed proxy card, signing and dating the proxy card and returning it to your respective company in the enclosed envelope.accompanying pre-addressed envelope as soon as possible.

This joint proxy statement/prospectus contains information regarding the merger agreement, the proposed merger and the two companies. We encourage you to read this entire document carefully, including the discussion under the section entitled “Risk Factors,” which begins on page 19.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued under this joint proxy statement/prospectus or determined if this joint proxy statement/prospectus is truthful or complete. Any representation to the contrary is a criminal offense. This joint proxy statement/prospectus is dated , 2003,[            ], 2004, and is first being mailed to TelliumZhone and ZhoneSorrento stockholders on or about , 2003.June 1, 2004.

ADDITIONAL INFORMATION

This joint proxy statement/prospectus incorporates important business and financial information about TelliumZhone from other documents that are not included in or delivered with this joint proxy statement/prospectus. For a listing of the documents incorporated by reference into this joint proxy statement/prospectus, please see the section entitled “Where You Can Find More Information.”

TelliumZhone will provide you with copies of the information relating to Tellium,Zhone, without charge, upon written or oral request to:

Tellium,Zhone Technologies, Inc.

2 Crescent Place7001 Oakport Street

Oceanport, New Jersey 07757Oakland, California 94621

(732) 923-4100(510) 777-7013

Attention: Investor Relations

In order for you to receive timely delivery of the documents in advance of the TelliumZhone or ZhoneSorrento stockholder meetings, TelliumZhone should receive your request no later than , 2003.June 23, 2004.

ZHONE TECHNOLOGIES, INC.

7001 Oakport Street

Oakland, California 94621

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

TO BE HELD ON , 2003JUNE 30, 2004

To the Stockholders of Tellium,Zhone Technologies, Inc.:

NOTICE IS HEREBY GIVEN that a special meeting of stockholders of Tellium,Zhone Technologies, Inc. will be held at Tellium’sZhone’s principal offices at 2 Crescent Place, Oceanport, New Jersey 077577001 Oakport Street, Oakland, California 94621 on , 2003June 30, 2004 at 9:00 a.m., local time, for the following purposes:

Please refer to the attached joint proxy statement/prospectus, which forms a part of this notice and is incorporated herein by reference, for further information with respect to the business to be transacted at the special meeting.

StockholdersOnly stockholders of record of Zhone common stock at the close of business on SeptemberMay 25, 2003 which we refer to as2004, the record date for the Zhone special meeting, or their proxies are entitled to notice of and to vote at thethis special meeting or any adjournment or postponement of the special meeting. Certain directors and executive officers of Tellium and their affiliates owning Tellium common stock, representing approximately 8% of the shares of Tellium common stock outstanding as of the record date, have agreed to vote their shares in favor of the proposal to issue Tellium common stock in the merger.

The board of directors of Tellium unanimously recommends that you vote“FOR” the proposal to issue Tellium common stock in the merger.

The presence, in person or by proxy, of a majority of the outstanding shares of TelliumZhone common stock entitled to vote will be required to establish a quorum at the TelliumZhone special meeting. The approval of the issuance of Tellium common stock in the merger requires the affirmative vote of a majority of the votes cast at the meeting (a quorum being present). is required to approve the issuance of Zhone common stock in the merger.

Your vote is important. PleaseWhether or not you expect to attend the Zhone special meeting in person, please complete, sign, date and return the enclosed proxy card as soon as possible to make sure that your shares are represented at the special meeting. To do so, Returning the proxy card does not deprive you of your right to attend the Zhone special meeting and to vote your shares in person. You may completerevoke your proxy at any time before it is actually voted at the meeting by: delivering written notice of revocation to Zhone’s Secretary at 7001 Oakport Street, Oakland, California 94621; submitting a later dated proxy; or attending the special meeting and returnvoting in person. For specific instructions on voting procedures and revocation of proxies, please refer to the enclosedsection entitled “The Zhone Special Meeting” beginning on page 85 of this joint proxy card. Alternatively, you may usestatement/prospectus and the toll-free telephone number showninstructions on the proxy card tocard.

The Zhone board of directors unanimously approved the merger agreement and unanimously recommends that Zhone stockholders vote by telephone or visit“FOR” the web site noted on the proxy card to vote over the Internet. This will not prevent you from voting in person, but it will help to secure a quorum and avoid added solicitation costs. If you are a stockholderissuance of record of TelliumZhone common stock you also may cast your vote in person at the special meeting.merger.

By order of the Board of Directors,

Michael J. LoschKirk Misaka

Chief Financial Officer, SecretaryTreasurer and TreasurerSecretary

            , 2003[            ], 2004

Please note that attendance at the special meeting will be limited to stockholders of Tellium as of the record date, or their authorized representatives, and guests of Tellium.SORRENTO NETWORKS CORPORATION

9990 Mesa Rim Road

San Diego, California 92121

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

TO BE HELD ON , 2003JUNE 30, 2004

To the Stockholders of Zhone Technologies, Inc.:Sorrento Networks Corporation:

NOTICE IS HEREBY GIVEN that a special meeting of stockholders of Zhone Technologies, Inc.Sorrento Networks Corporation will be held at Zhone’sSorrento’s principal offices at 7001 Oakport Street, Oakland,9990 Mesa Rim Road, San Diego, California 9462192121 on , 2003June 30, 2004 at 10:00 a.m., local time, for the following purposes:

Please refer to the attached joint proxy statement/prospectus, which forms a part of this notice and is incorporated herein by reference, for further information with respect to the business to be transacted at the special meeting.

StockholdersOnly stockholders of record of Sorrento common stock at the close of business on SeptemberMay 25, 2003 which we refer to as2004, the record date for the Sorrento special meeting, or their proxies are entitled to notice of and to vote at thethis special meeting or any adjournment or postponement of the special meeting. Certain stockholders, directors and executive officers of Zhone owning Zhone common stock and preferred stock, representing approximately 69% of the voting power of the Zhone common stock and preferred stock voting together on an as-converted basis and approximately 68% of the voting power of the Zhone preferred stock (with all series of Zhone preferred stock voting together on an as-converted basis) outstanding as of the record date, have agreed to vote their shares in favor of the proposal to adopt the merger agreement. Because of this voting control, these entities, acting together, can cause the approval of the proposal to adopt the merger agreement without the affirmative vote of any other stockholder of Zhone.

The board of directors of Zhone unanimously recommends that you vote“FOR” the proposal to adopt the merger agreement.

The presence, in person or by proxy, of a majority of the outstanding shares of ZhoneSorrento common stock and preferred stock entitled to vote will be required to establish a quorum at the ZhoneSorrento special meeting. The affirmative vote of a majority of the outstanding shares of ZhoneSorrento common stock and preferred stock voting together on an as-converted basis and a majority of the outstanding shares of Zhone preferred stock (with all series of Zhone preferred stock voting together on an as-converted basis) is required to adopt the merger agreement.

Your vote is important. PleaseWhether or not you expect to attend the Sorrento special meeting in person, please complete, sign, date and return the enclosed proxy card as soon as possible to make sure that your shares are represented at the special meeting. To do so, Returning the proxy card does not deprive you of your right to attend the Sorrento special meeting and to vote your shares in person. You may complete and return the enclosedrevoke your proxy card. If you are a stockholder of record of Zhone common stock or preferred stock, you also may cast your vote in personat any time before it is actually voted at the meeting by: delivering written notice of revocation to Sorrento’s Secretary at 9990 Mesa Rim Road, San Diego, California 92121; submitting a later dated proxy; or attending the special meeting. If you domeeting and voting in person. For specific instructions on voting procedures and revocation of proxies, please refer to the section entitled “The Sorrento Special Meeting” beginning on page 88 of this joint proxy statement/prospectus and the instructions on the proxy card.

Sorrento stockholders are not vote, it will haveentitled to dissenters’ rights of appraisal for their shares under Delaware law in connection with the same effect as voting againstmerger. Please refer to the proposal to adoptsection entitled “The Merger-No Appraisal Rights” beginning on page 61 of this joint proxy statement/prospectus for a discussion of appraisal rights.

The Sorrento board of directors unanimously approved the merger agreement and unanimously recommends that Sorrento stockholders vote “FOR” the approval of the merger agreement.

Please do not send any certificates representing your ZhoneSorrento common stock or preferred stock at this time.

Please note that attendance at the special meeting will be limited to stockholders of Zhone as of the record date, or their authorized representatives, and guests of Zhone.Joe Armstrong

Chief Financial Officer

[            ], 2004

TABLE OF CONTENTS

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QUESTIONS AND ANSWERS ABOUT THE MERGER

In order to complete the merger, TelliumZhone stockholders must vote to approve the issuance of shares of TelliumZhone common stock in connection with the merger, and ZhoneSorrento stockholders must vote to adopt the merger agreement.agreement and approve the merger.

TelliumZhone and ZhoneSorrento will hold separate meetings of their respective stockholders to obtain these approvals. This joint proxy statement/prospectus contains important information about the merger and the special meetings of the respective stockholders of each of TelliumZhone and Zhone,Sorrento, and you should read it carefully. The enclosed voting materials allow you to vote your shares without attending your special meeting.

Your vote is important. We encourage you to vote as soon as possible.

Immediately after the merger described above, Tellium will effect a second merger with a newly formed, wholly owned subsidiary, which will merge with and into Tellium and, as a result, Tellium will be re-named Zhone Technologies, Inc., which may be referred to in this joint proxy/statement prospectus as the “combined company.” We anticipate that the combined company will trade on Nasdaq under the ticker symbol “ZHNE.”

Q:	What will I receive for my Sorrento 7.5% senior convertible debenture?

Based on the capitalization of Tellium and Zhone as of the date of this joint proxy statement/prospectus, Tellium and Zhone estimate that the exchange ratio will be approximately             , which means that each

share of Zhone common stock will convert, at the time of the merger, into              shares of Tellium common stock. The exchange ratio will be adjusted proportionately in the event that a reverse split of Tellium’s common stock, approved by Tellium’s stockholders at its last annual meeting of stockholders, is implemented by Tellium’s board of directors prior to the merger. Tellium and Zhone expect that a reverse split of Tellium’s common stock will be implemented prior to the merger according to a ratio between (and including) one-for-ten and one-for-four.

As a condition to the consummation of the merger, all shares of Zhone preferred stock will be converted into shares of Zhone common stock immediately prior to the merger on a one for one basis. Accordingly, Zhone preferred stockholders and Zhone common stockholders will receive the same per share consideration in the merger.

The final exchange ratio will be calculated based on the total number of fully converted shares outstanding for Tellium and Zhone immediately prior to the merger. Zhone stockholders will receive cash in lieu of any fractional shares of Tellium common stock. Please see “The Merger Agreement—The Merger Consideration and Conversion of Securities.”

Based on the estimated exchange ratio of approximately             , Tellium and Zhone estimate that, on a pre-reverse split basis, Tellium will issue approximately              million shares of Tellium common stock in the merger and reserve an additional approximately              million shares of Tellium common stock for future issuance in connection with Tellium’s assumption of Zhone’s outstanding options and warrants (including out-of-the-money options and warrants).

The ZhoneSorrento special meeting will take place at 7001 Oakport Street, Oakland,9990 Mesa Rim Road, San Diego, California 9462192121 on , 2003June 30, 2004 at 10:00 a.m., local time.

shares of TelliumZhone common stock to the ZhoneSorrento stockholders in the merger. For a more complete description of the recommendation of the TelliumZhone board of directors, see “The Merger—Reasons for the Merger—Tellium.Zhone.”

The Zhone board of directors unanimously recommends that Zhone stockholders vote “FOR” the proposal to adopt the merger agreement. For a more complete description of the recommendation of the Zhone board of directors, see “The Merger—Reasons for the Merger—Zhone.”

instructions on how to vote your shares. Please refer to the voting instruction card used by your broker or nominee to see if you may submit voting instructions by telephone.nominee.

agent on how to exchange your ZhoneSorrento stock certificates for TelliumZhone stock certificates. Please do not send in your ZhoneSorrento stock certificates with your proxy.

ZhoneSorrento stockholders who have any questions about the merger or how to submit a proxy, or who need additional copies of this joint proxy statement/prospectus or the enclosed proxy card or voting instructions, should contact: Christen Chesel, Zhone Technologies, Inc., 7001 Oakport Street, Oakland,Joe Armstrong, Sorrento Networks Corporation, 9990 Mesa Rim Road, San Diego, California 94621,92121, Telephone: (510) 777-7013(858) 450-4934 or Email: investor-relations@zhone.com.jarmstrong@sorrentonet.com.

SUMMARY

The following is a summary of information contained in this joint proxy statement/prospectus. This summary may not contain all of the information about the merger that is important to you. For a more complete description of the merger, TelliumZhone and ZhoneSorrento encourage you to read carefully this entire joint proxy statement/prospectus, including the attached annexes. In addition, TelliumZhone and ZhoneSorrento encourage you to read the information incorporated by reference into this joint proxy statement/prospectus, which includes important business and financial information about Tellium that it has filed with the Securities and Exchange Commission, or the SEC.Zhone. You may obtain the information incorporated by reference into this joint proxy statement/prospectus without charge by following the instructions in the section entitled “Where You Can Find More Information.”

The Companies (see page 91)

Tellium, Inc.

2 Crescent Place

Oceanport, New Jersey 07757

(732) 923-4100

Tellium designs, develops and markets high-speed, high-capacity, intelligent optical switching solutions that enable network service providers to quickly and cost-effectively deliver new high-speed services. Intelligent optical switches are products that are installed in telecommunications networks to manage the flow of optical signals, which are beams of light transmitted over fiber optic cables.

Tellium’s products include highly reliable hardware, standards-based operating software and integrated network planning, and network management tools designed to deliver intelligent optical switching for public telecommunications networks. They are specifically designed to manage very high-speed optical signals and can be easily expanded, enabling service providers to grow and manage their networks quickly and efficiently to keep pace with dynamic requirements of data services. Tellium has designed its products to be cost-effective for service providers when they are expanding and enhancing the capabilities of their existing networks or building out new ones. Tellium’s optical switches operate with existing optical networking equipment to support the transition from older networks to advanced, intelligent optical networks without service disruption. This capability protects service providers’ prior investment in fiber optics and transmission equipment. Tellium’s optical switches are easily upgraded, providing its customers with the ability to adopt new technologies and features without the need to replace Tellium’s equipment.

Zhone Technologies, Inc.

7001 Oakport Street

Oakland, California 94621

(510) 777-7000

Zhone designs, develops and markets telecommunications hardware and software that simplify today’s telecommunications networks. Zhone’s products, which address the connection between network service providers and their subscribers, or the localwireline access network, allow network service providers to combine voice, data, video, entertainment and management services over their existing copper-wire infrastructure. Also,copper wire infrastructure while supporting migration to fiber networks. Zhone’s products also enable network service providers to transition to a fiber infrastructure while continuing to operatemore cost-competitive VoIP and packet-based services without compromising their current copper infrastructure.ATM and circuit-based revenue streams. In addition, Zhone’s products allow network service providers to add rich new subscriber services more quickly than is possible with conventional copper access solutions.

Zhone is the first company dedicated solely to developing the full spectrum of next-generation accesswireline network solutions. Zhone’s flagship products are based upon its Single Line Multi Service, or SLMS, architecture. This new approach was specifically developed to address the unmet challenges of delivering standards-basedmanaging the complex transition from legacy service delivery to packet-based voice, data and video solutions. SLMS provides carriers with flexibility and investment protection by supporting the most widely accepted media and technology protocols. Zhone’s products enable network service providers to use their existing networks to deliver voice, data, video and entertainment services to their customers. Zhone has designed its products to interoperate with different types of wiring and equipment already deployed in service providers’ networks and in subscribers’ homes. Zhone’s products enable network service providers to elegantly migrate their existing networks to delivervoice, data, video and entertainment services to their customers.

Zhone’s strategy is to develop products through a combination of internal development and acquisitions of companies with applicable technology or market presence. This strategy has allowed Zhone to rapidly advance its flagship products by incorporating key acquired technologies into its SLMS product architecture.

Sorrento Networks Corporation

9990 Mesa Rim Road

San Diego, California 92121

(858) 558-3960

Sorrento is a leading supplier of intelligent optical networking solutions for access, metropolitan and regional applications worldwide. Sorrento’s solutions enable communications carriers and service providers to offer broadband networking services over their existing optical fiber infrastructure. Sorrento’s technologies permit telecommunications service providers to increase fiber capacity and fiber bandwidth utilization, reduce network costs and complexity over scalable and efficient networking platforms. Sorrento’s optical networking systems support a wide variety of protocols, mixed speeds of traffic and accommodate changing traffic patterns directly over optical networks.

Sorrento’s product solutions include optical access, optical transport, and network management solutions optimized for access, metro and regional markets, and combine to create powerful, cost-effective, and easy-to- manage optical networks. Sorrento’s dense wavelength division multiplexing, or DWDM, and coarse wavelength division

multiplexing, or CWDM, platforms can be used in enterprise, access, metropolitan and regional network applications. WDM technology allows many optical signals to be transmitted simultaneously on the same optical fiber by using different wavelengths of light to distinguish the signals. This technology increases optical network capacity and flexibility.

Sorrento currently has an installed base with over 20 communications service providers and system integrators worldwide, including AT&T Broadband, now Comcast Corporation, Deutsche Telekom, Cox Communications, Time Warner Telecom, United Pan-Europe Communications, El Paso Global Networks and Edison Carrier Solutions.

The Merger (see page 37)

TelliumZhone and ZhoneSorrento have agreed to the combination of TelliumZhone and ZhoneSorrento under the terms of the merger agreement described in this joint proxy statement/prospectus. We have attached the merger agreement asAnnex A to this joint proxy statement/prospectus. We encourage you to read the merger agreement in its entirety.

Under the terms of the merger agreement, ZebraSelene Acquisition Corp., a newly formed and wholly owned subsidiary of Tellium,Zhone, will merge with and into ZhoneSorrento and the separate corporate existence of Zebra Acquisition Corp.Selene will cease. ZhoneSorrento will be the surviving corporation in the merger and will continue as a wholly owned subsidiary of Tellium under the name ZTI Merger Subsidiary III, Inc.Zhone.

Upon completion of the merger, ZhoneSorrento stockholders will be entitled to receive 0.9 of a certain numbershare of shares of TelliumZhone common stock for each share of ZhoneSorrento common stock owned as of the effective time of the merger. The number of shares of Tellium common stock to be issued with respect to each share of Zhone common stock will be determined by a formula described in the merger agreement and this joint proxy statement/prospectus.

Based on the capitalization of Tellium and Zhone as of the date of this joint proxy statement/prospectus, we estimate that the exchange ratio will be approximately             , which means that each share of Zhone common stock will convert, at the time of the merger, into              shares of Tellium common stock. The exchange ratio will be adjusted proportionately in the event that a reverse split of Tellium’s common stock, approved by Tellium’s stockholders at its last annual meeting of stockholders, is implemented by Tellium’s board of directors prior to the merger. We expect that a reverse split of Tellium’s common stock will be implemented prior to the merger according to a ratio between (and including) one-for-ten and one-for-four.

All shares of Zhone preferred stock will be converted into shares of Zhone common stock immediately prior to the merger on a one for one basis. Accordingly, Zhone preferred stockholders andZhone common stockholders will receive the same per share consideration inclosing of the merger. Stockholders of TelliumZhone will continue to own their existing shares.

Immediately after the merger described above, Tellium will effect a second merger with a newly formed, wholly owned subsidiary, which will merge with and into Tellium and, as a result, Tellium will be re-named Zhone Technologies, Inc. This second merger does not require stockholder approval.

Recommendations of the Boards of Directors (see page 42)

Tellium’sThe Zhone board of directors unanimously approved the merger and unanimously recommends that TelliumZhone stockholders vote “FOR” the proposal to issue TelliumZhone common stock pursuant to the merger agreement.

Zhone’sThe Sorrento board of directors unanimously approved the merger and unanimously recommends that ZhoneSorrento stockholders vote“FOR” the proposal to adopt the merger agreement.

Stockholders Entitled to Vote; Vote Required in Connection with the Merger Proposals(see page 86)

You can vote at the TelliumZhone special meeting if you owned TelliumZhone common stock at the close of business on SeptemberMay 25, 2003,2004, the record date for the TelliumZhone special meeting. On that date, there were 116,893,020approximately 78,142,000 shares of TelliumZhone common stock outstanding and entitled to vote. You can cast one vote for each share of TelliumZhone common stock that you owned on that date. Approval of the proposal to issue shares of TelliumZhone common stock pursuant to the merger agreement requires the affirmative vote of a majority of the total votes cast at the special meeting by holders of Tellium’sZhone common stock outstanding as of the record date (a quorum being present). As of the record date, Tellium’s executive officers, directors and entities affiliated with them owned, in the aggregate, approximately 8% of Tellium’s outstanding common stock.

You can vote at the ZhoneSorrento special meeting if you owned ZhoneSorrento common stock or preferred stock at the close of business on SeptemberMay 25, 2003,2004, the record date for the ZhoneSorrento special meeting. On that date, there were 15,744,078approximately 17,239,475 shares of ZhoneSorrento common

stock outstanding and entitled to vote, 62,500,000 shares of Series AA preferred stock outstanding and entitled to vote and 20,469,338 shares of Series B preferred stock outstanding and entitled to vote. Each share of ZhoneSorrento common stock, Series AA preferred stock and Series B preferred stock is entitled to one vote.

The affirmative vote of a majority of the outstanding shares of ZhoneSorrento common stock and preferred stock voting together on an as-converted basis and a majority of the outstanding shares of Zhone preferred stock (with all series of Zhone preferred stock voting together on an as-converted basis) is required to adopt the merger agreement. As of the record date, Zhone’s executive officers, directors and entities affiliated with them owned, in the aggregate, approximately 76% of Zhone’s outstanding common stock and approximately 68% of Zhone’s outstanding preferred stock.

Voting Agreements (see page 71)

ZhoneSorrento has entered into a voting agreement with certain significant stockholders, directors and executive officers of Tellium and their affiliatesZhone owning TelliumZhone common stock representing approximately 8%43% of the sharesvoting power of Telliumthe Zhone common stock outstanding as of the record date, pursuant to which these stockholders have agreed to vote their shares in favor of the proposal to issue Tellium common stock pursuant tomerger and adoption of the merger agreement.agreement as described in “Voting Agreements-Zhone Stockholders.” This voting agreement is attached to this joint proxy statement/prospectus asAnnex B.

TelliumZhone and Zebra Acquisition Corp.Selene have entered into a voting agreement with certain significant stockholders,

directors and executive officers of ZhoneSorrento owning ZhoneSorrento common stock and preferred stock representing approximately 69%less than one percent of the voting power of the ZhoneSorrento common stock and preferred stock voting together on an as-converted basis and approximately 68% of the voting power of the Zhone preferred stock (with all series of Zhone preferred stock voting together on an as-converted basis) outstanding as of the record date, pursuant to which these stockholders have agreed (1) to vote their shares in favor of the proposal to adoptmerger and adoption of the merger agreement and (2) for a period of 180 days following the merger, not to transfer any Tellium common stock received by such stockholder in the merger or publicly announce an intention to effectany such transfer, subject to certain permitted exceptions as described in “Voting Agreements—ZhoneAgreements-Sorrento Stockholders.” Because of this voting control, these entities, acting together, can cause the approval of the proposal to adopt the merger agreement without the affirmative vote of any other stockholder of Zhone. This voting agreement is attached to this joint proxy statement/prospectus asAnnex C.

Opinion of Morgan StanleyThomas Weisel Partners LLC to TelliumZhone (see page 46)

On July 25, 2003, Morgan Stanley & Co. Incorporated delivered its oral opinion, subsequently confirmed in writing, to the Tellium board of directors that, as of such date and based upon and subject to the various considerations set forth in its opinion, the exchange ratio pursuant to the merger agreement was fair from a financial point of view to the holders of shares of Tellium common stock. Morgan Stanley provided its opinion to the Tellium board of directors in connection with the board’s consideration of the merger. The Morgan Stanley opinion is not a recommendation as to how any Tellium stockholder should vote with respect to the proposal to approve the issuance of shares of Tellium common stock in connection with the merger.

The full text of the written opinion of Morgan Stanley, which sets forth assumptions made, matters considered and limitations on the review undertaken in connection with its opinion, is attached to this joint proxy statement/prospectus asAnnex D. Stockholders of Tellium are urged to read the opinion carefully and in its entirety.

Opinion of Credit Suisse First BostonApril 21, 2004, Thomas Weisel Partners LLC to Zhone

On July 25, 2003, Credit Suisse First Boston rendered its oral opinion to the Zhone board of directors, subsequently confirmed in writing on July 27, 2003,as of April 21, 2004, that, as of the date of its opinion and based upon and subject to the various considerations set forth in the Credit Suisse First Bostonits opinion, the exchange ratioconsideration to be issued by Zhone in the merger was fair, from a financial point of view, to holders of Zhone common stock (assuming conversion of shares of Zhone preferred stock into shares of Zhone common stock as contemplated in the merger agreement), other than affiliates of Zhone.

The full text of the Credit Suisse First Boston

Thomas Weisel Partners opinion, which sets forth, among other things, assumptions made, procedures followed, matters considered and limitations on the scope of the review undertaken by Credit Suisse First BostonThomas Weisel Partners in rendering its opinion, is attached asAnnex ED to this joint proxy statement/prospectus. Zhone stockholders are urged to, and should, read the Credit Suisse First BostonThomas Weisel Partners opinion carefully and in its entirety. The Credit Suisse First BostonThomas Weisel Partners opinion addresses only the fairness, from a financial point of view, of the exchange ratio to holders of Zhone common stock (assuming conversion of shares of Zhone preferred stock into shares of Zhone common stock as contemplated in the merger agreement), other than affiliates of Zhone as of the date of the Credit Suisse First BostonThomas Weisel Partners opinion, and does not constitute a recommendation to any stockholder as to how such stockholder should vote or act on any matter relating to the merger. In addition,

Opinion of Needham & Company, Inc. to Sorrento (see page 51)

On April 21, 2004, Needham & Company, Inc. rendered its oral opinion to the Credit Suisse First BostonSorrento board of directors, subsequently confirmed in writing as of April 21, 2004, that, as of the date of its opinion and based upon and subject to the various considerations set forth in its opinion, the exchange ratio was fair, from a financial point of view, to holders of Sorrento common stock.

The full text of the Needham & Company opinion, which sets forth, among other things, assumptions made, procedures followed, matters considered and limitations on the scope of the review undertaken by Needham & Company in rendering its opinion, is attached asAnnex E to this joint proxy statement/prospectus. Sorrento stockholders are urged to, and should, read the Needham & Company opinion carefully and in its entirety. The Needham & Company opinion addresses only the fairness, from a financial point of view, of the exchange ratio to holders of Sorrento common stock as of the date of the Needham & Company opinion, and does not constitute a recommendation to any holder of Zhone preferred stockstockholder as to whetherhow such stockholder should convert its ownership of Zhone preferred stock into Zhone common stock in connection withvote or act on any matter relating to the merger.

Ownership of the Combined Company after the Merger

Upon completion of the merger, Zhone stockholders will be entitled to receive a certain number of shares of Tellium common stock for each share of Zhone common stock owned as of the effective time of the merger. The number of shares of Tellium common stock to be issued with respect to each share of Zhone common stock will be determined by a formula described in the merger agreement and this joint proxy statement/prospectus. The formula will result in the holders of Zhone’s outstanding stock, options and warrants receiving 60% of the shares of the combined company on a fully converted basis and the holders of Tellium’s outstanding stock, options and warrants retaining 40% of the combined company.

Interests of Directors and Executive Officers of TelliumZhone in the Merger (see page 59)

In considering the recommendation of the TelliumZhone board of directors regarding the merger, Zhone stockholders should be aware that some Zhone directors and executive officers have interests in the merger and related arrangements that are different from, or in addition to, their interests as Zhone stockholders.

C. Richard Kramlich, a member of Zhone’s board of directors, is a general partner of New Enterprise Associates, a venture capital firm that is affiliated with various New Enterprise Associates entities that hold Zhone common stock and warrants to purchase shares of Sorrento common stock. In addition, Morteza Ejabat, Zhone’s Chairman and Chief Executive Officer, Jeanette Symons, Zhone’s Chief Technology Officer, and Robert Dahl, a member of Zhone’s board of directors, and/or trusts for the benefit of the foregoing persons or their family members, have partnership interests in various New Enterprise Associates entities that are holders of both Zhone common stock and warrants to purchase shares of Sorrento common stock. Upon completion of the merger, these warrants to purchase shares of Sorrento common stock will be converted into warrants to purchase shares of Zhone common stock as adjusted to give effect to the merger exchange ratio.

These interests may create potential conflicts of interest for these directors and executive officers

because they may be more likely to approve the issuance of Zhone common stock in connection with the merger than Zhone stockholders generally. The Zhone board of directors was aware of these interests and took these interests into account in its deliberations of the merits of the merger and in approving the merger and the transactions contemplated by the merger agreement. See “The Merger—Interests of Directors and Executive Officers of Zhone in the Merger.”

Interests of Directors and Executive Officers of Sorrento in the Merger (see page 60)

In considering the recommendation of the Sorrento board of directors that TelliumSorrento stockholders vote in favor of the issuanceadoption of Tellium common stock pursuant to the merger agreement, TelliumstockholdersSorrento stockholders should be aware that some TelliumSorrento directors and executive officers may have interests in the merger that may be different from, or in addition to, their interests as stockholders of Tellium.Sorrento. These include interests and potential claims arising under:relating to:

The TelliumSorrento board of directors was aware of these interests during its deliberations of the merits of the merger and in determining to recommend to Tellium stockholders that they vote for the proposal to issue Tellium common stock pursuant to the merger agreement. See “The Merger—Interests of Directors and Executive Officers of Tellium in the Merger.”

Interests of Directors and Executive Officers of Zhone in the Merger

In considering the recommendation of the Zhone board of directors that Zhone stockholders vote in favor of adoption of the merger agreement, Zhone

stockholders should be aware that some Zhone directors and executive officers may have interests in the merger that may be different from, or in addition to, their interests as stockholders of Zhone. These include interests arising under:

The Zhone board of directors was aware of these interests during its deliberations of the merits of the merger and in determining to recommend to ZhoneSorrento stockholders that they vote for the proposal to adopt the merger agreement. See “The Merger—Interests of Directors and Executive Officers of ZhoneSorrento in the Merger.”

Listing of TelliumZhone Common Stock and Deregistration of ZhoneSorrento Common Stock (see page 59)

Tellium’sZhone common stock is currently traded on the Nasdaq SmallCapNational Market under the symbol “TELM.“ZHNE.” It is a condition to the consummation of the merger that the shares of TelliumZhone common stock issuable in the merger be approved for listing on the Nasdaq National Market or the Nasdaq SmallCap Market.

On September 11, 2003, The Nasdaq Stock Market notified Tellium that the proposed merger between Tellium and Zhone would result in a reverse merger of Tellium. As a result, Tellium has submitted an initial listing application and must satisfy all of the initial Nasdaq National Market or Nasdaq SmallCap Market inclusion criteria, including a minimum bid price of $5 or $4 per share, respectively. On October 9, 2003, the last sale price of Tellium’s common stock was $1.35 per share.

In order to meet the listing requirements of the Nasdaq National Market or the Nasdaq SmallCap Market, Tellium has agreed to effect a reverse stocksplit with respect to the Tellium common stock, if necessary, according to a ratio between (and including) one-for-ten and one-for-four. Tellium’s stockholders have previously approved a reverse stock split of Tellium’s common stock within such range. Tellium and Zhone expect that a reverse stock split will be implemented prior to the merger with the exact ratio of the reverse stock split, between the ranges described above, to be agreed to by Tellium and Zhone.

If the merger is completed, ZhoneSorrento common stock will be deregistered under the Securities Exchange Act of 1934, as amended, or the Exchange Act, and ZhoneSorrento will no longer file periodic reports with the Securities and Exchange Commission, or SEC.

No Appraisal Rights (see page 61)

TelliumNeither Zhone stockholders nor Sorrento stockholders are not entitled to dissenters’ or appraisal rights in connection with the merger.

Holders of Zhone common stock and preferred stock will be permitted to exercise appraisal rights under the Delaware General Corporation Law and dissenters’ rights under the California General Corporation Law in connection with the merger, except to the extent that a court or applicable legal authority rules otherwise. However, it is a condition to Tellium’s obligation to consummate the merger that holders of less than 10% of the outstanding shares of Zhone common stock (on an as-converted basis) have perfected appraisal rights under the Delaware General Corporation Law or the California General Corporation Law. See “Appraisal Rights.”

Conditions to Completion of the Merger (see page 67)

In order to complete the merger, TelliumZhone and ZhoneSorrento must satisfy a number of conditions, including, but not limited to, the following:

On August 25, 2003, we received notice fromagreement must have been declared effective by the Federal Trade Commission that we received early termination of the applicable waiting periods under the HSR Act;SEC and not be subject to any stop order,

No Solicitation by Tellium or ZhoneSorrento (see page 66)

The merger agreement contains detailed provisions restricting Tellium and ZhoneSorrento from seeking an alternative transaction with another party. These “no solicitation” provisions prohibit Tellium and Zhone,Sorrento, as well as each of theirits subsidiaries and representatives, from taking any action to solicit an acquisition proposal from another party. The merger agreement does not, however, prohibit Tellium or Zhone,Sorrento or its board of directors from considering, and potentially recommending, an unsolicited bona fide superior written proposal under limited circumstances.

Termination of the Merger Agreement (see page 68)

TelliumZhone and ZhoneSorrento can jointly agree to terminate the merger agreement at any given time. Either company may also terminate the merger agreement if the merger is not completed by March 31,September 30, 2004, subject to certain limitations, and under other circumstances described in this joint proxy statement/prospectus.

Termination Fees and Expenses (see page 69)

The merger agreement provides that, under specified circumstances, TelliumZhone or ZhoneSorrento may be required to payreimburse the other party’s expenses related to the merger up to $1 million andmillion. In addition, Sorrento has agreed to pay Zhone a termination fee equal to $3of $2 million less(less the amount, ofif any, paymentpreviously paid by Sorrento to reimburse Zhone for out-of-pocket expenses) in the event that the merger agreement is terminated under other party’s expenses related to the merger.specified circumstances.

Sorrento Stock Options and Warrants (see page 62)

Upon completion of the merger, Zhone Preferred Stockwill assume all options to purchase Sorrento common stock and warrants to purchase Sorrento common stock then outstanding under Sorrento’s option agreements, stock option plans and warrant agreements. Upon completion of the merger, each assumed option and warrant to purchase Sorrento stock will cease to represent a right to acquire shares of Sorrento stock and will be converted into an option or warrant to purchase Zhone common stock.

In each case, the number of shares of Zhone common stock subject to the new Zhone option or warrant will be equal to the number of shares of Sorrento common stock subject to the Sorrento option or warrant multiplied by 0.9, and the exercise price per share of Zhone common stock will be equal to the existing per share exercise price of the Sorrento option or warrant divided by 0.9.

Sorrento Debentures (see page 63)

Upon completion of the merger, each share7.5% senior convertible debenture due August 2, 2007 of Zhone preferred stock issued andSorrento which is outstanding immediately prior to the effective time of the merger will automatically be converted into the right to receive a number of shares of Tellium common stock equal to the exchange ratio. The merger agreement also provides, as a condition to Tellium consummating the merger, that all shares of Zhone preferred stock will be convertedassumed by Zhone and thereafter continue to represent a debenture of Sorrento, except that the Sorrento debentures will be convertible into shares of Zhone common stock immediately prioras adjusted to the effective time of the merger on a one for one basis. Accordingly, Zhone preferred stockholders and Zhone common stockholders will receive the same per share consideration ingive effect to the merger.

Zhone Stock Options and Warrants

Upon completion of the merger, Tellium will assume all options to purchase Zhone common stock and all warrants to purchase Zhone common stock and Zhone preferred stock then outstanding under Zhone’s option agreements, stock option plans and warrant agreements. After the merger, each option and warrant will represent the right to purchase that number of shares of Tellium common stock equal to the number of shares of Zhone common stock covered by the option or Zhone common stock or preferred stock covered by the warrant, as applicable, immediately before the merger multiplied by the

exchange ratio, rounded down to the nearest whole share. The exercise price per share of Tellium common stock subject to each option or warrant will equal the pre-conversion price per share of Zhone common stock subject to such option or the pre-conversion price of Zhone common stock or preferred stock subject to such warrant, as applicable, divided by the exchange ratio, rounded to the nearest whole cent.

Material United States Federal Income Tax Consequences of the Merger (see page 57)

ItThe merger is expected that the merger willintended to be treated as a reorganization for U.S. federal income tax purposes, and Zhone’s obligation to completepurposes. However, the treatment of the merger as a reorganization is conditioned onnot a condition to the receipt of a tax opinion from its counsel, dated asclosing of the closing date, thatmerger and no ruling from the merger will be so treated.Internal Revenue Service or opinion of counsel has been requested regarding the tax consequences of the merger. Assuming that the merger is treated as a reorganization, then, in general, ZhoneSorrento stockholders who exchange their ZhoneSorrento stock solely for TelliumZhone common stock in the merger will not recognize gain or loss for U.S. federal income tax purposes as a result of the merger, except that ZhoneSorrento stockholders will recognize gain or loss with respect to any cash they receive in lieu of fractional shares of TelliumZhone common stock upon completion of the merger.

Tax matters are very complicated, and the tax consequences of the merger to ZhoneSorrento stockholders will depend on each ZhoneSorrento stockholder’s particular tax situation. Each ZhoneSorrento stockholder is urged to read carefully the discussion in the section entitled “The Merger—Material United States Federal Income Tax Consequences of the Merger” and to consult its tax advisors regarding the specific tax consequences of the merger.

Accounting Treatment (see page 58)

The merger will be accounted for as a “reverse acquisition” using the purchase method of accounting under generally accepted accounting principles. Although the merger is structured such that Zhone will become a wholly owned subsidiary of Tellium at closing, Zhone will be treated as the acquiring company for accounting purposes.

Regulatory Approvals (see page 57)

Under the HSRHart-Scott-Rodino Antitrust Improvements Act of 1976 and the rules promulgated thereunder by the Federal Trade Commission, certain transactions, including the merger, may not be completed unless certain waiting period requirements have been satisfied. The merger may also be subject to review by the governmental authorities of various other jurisdictions under the antitrust laws of those jurisdictions. On August 25, 2003, we received notice fromMay 14, 2004, Zhone and Sorrento each filed notification reports with the Department of Justice and the Federal Trade Commission that we receivedand requested an early termination of the applicablerequired waiting periods underperiod. If early termination is not granted and a request for additional information by the HSR Act. In addition, ifrelevant antitrust authorities is not made, the shares of Tellium common stock issued in the merger are not listedwaiting period will expire at midnight on the Nasdaq National Market at the time of issuance, they will be subject to qualification under California law. On September 15, 2003, we received notice from the California Corporations Commissioner that the shares are qualified for offer, sale and issuance under California law.June 14, 2004.

Under the merger agreement, both TelliumZhone and ZhoneSorrento have agreed to use their commercially reasonable best efforts to obtain all required governmental approvals and avoid any action or proceeding by a governmental entity in connection with the execution of the merger agreement and completion of the merger. Except as noted above with respect to the required filings under the HSR Act, qualification under California law and the filing of a certificate of merger in Delaware at or before the effective time of the merger, neither Tellium nor Zhone is aware of any material federal or state regulatory requirements or approvals required for the execution of the merger agreement or completion of the merger.

Summary Historical Financial Data of Tellium

The following information is provided to aid you in your analysis of the financial aspects of the merger. This information was derived from the audited financial statements of Tellium for the years ended December 31, 1998 through December 31, 2002 and the unaudited financial statements of Tellium for the six months ended June 30, 2002 and June 30, 2003. This information is only a summary, and you should read it together with the historical financial statements and related notes contained in the annual and quarterly reports and other information filed by Tellium with the SEC and incorporated by reference in this joint proxy statement/prospectus. See “Where You Can Find More Information.”