Document:

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                                                                     Exhibit 4.2

                             AMENDED AND RESTATED

                            STOCKHOLDERS AGREEMENT

                                 BY AND AMONG

                                 TELLIUM, INC.

                                      AND

                     CERTAIN STOCKHOLDERS OF TELLIUM, INC.

                        DATED AS OF SEPTEMBER 19, 2000
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<TABLE>
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ARTICLE I.........................................................................................................1
   1.1. Affiliate.................................................................................................1
        ---------
   1.2. Common Stock..............................................................................................2
        ------------
   1.3. Exchange Act..............................................................................................2
        ------------
   1.4. Fully-Diluted Common Stock................................................................................2
        --------------------------
   1.5. Holders...................................................................................................2
        -------
   1.6. Liquidation Event.........................................................................................2
        -----------------
   1.7. Permitted Transfer........................................................................................2
        ------------------
   1.8. Preferred Stock...........................................................................................3
        ---------------
   1.9. Qualified IPO.............................................................................................3
        -------------
   1.10. Registrable Securities...................................................................................3
         ----------------------
   1.11. Related Party............................................................................................3
         -------------
   1.12. Securities Act...........................................................................................4
         --------------
   1.13. Shares...................................................................................................4
         ------
   1.14. TWCP Investors...........................................................................................4
         --------------
   1.15. Warrants.................................................................................................4
         --------
ARTICLE II........................................................................................................5
ARTICLE III.......................................................................................................5
   3.1. General...................................................................................................5
        -------
   3.2. Notice....................................................................................................5
        ------
   3.3. Right of First Offer......................................................................................6
        --------------------
   3.4. Tag-Along Right...........................................................................................7
        ---------------
   3.5. Closing...................................................................................................8
        -------
   3.6. Qualified Transfer........................................................................................8
        ------------------
   3.7. Company Effecting Transfers...............................................................................9
        ---------------------------
   3.8. Termination of Right of First Offer and Tag-Along Right...................................................9
        -------------------------------------------------------
ARTICLE IV........................................................................................................9
   4.1. Drag-Along Right..........................................................................................9
        ----------------
   4.2. Closing...................................................................................................9
        -------
   4.3. Termination of Drag-Along Right..........................................................................10
        -------------------------------
ARTICLE V........................................................................................................10
   5.1. General..................................................................................................10
        -------
   5.2. Qualified Offeree........................................................................................10
        -----------------
   5.3. Exemptions...............................................................................................10
        ----------
   5.4. Termination of Rights....................................................................................12
        ---------------------
ARTICLE VI.......................................................................................................12
   6.1. Membership Generally.....................................................................................12
        --------------------
   6.2. Committees...............................................................................................13
        ----------
   6.3. Removal..................................................................................................13
        -------
   6.4. Vacancies................................................................................................13
        ---------
   6.5. Certain Actions..........................................................................................13
        ---------------
   6.6. Termination..............................................................................................13
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ARTICLE VII......................................................................................................14
   7.1. Piggyback Registration Rights............................................................................14
        -----------------------------
   7.2. Demand Registration Rights; Form S-3 Registration Rights; Shelf Registration.............................15
        ----------------------------------------------------------------------------
   7.3. Registration Procedures..................................................................................18
        -----------------------
   7.4. Restrictions on Public Sale..............................................................................23
        ---------------------------
   7.5. Registration Expenses....................................................................................24
        ---------------------
   7.6. Indemnification..........................................................................................25
        ---------------
   7.7. Rule 144.................................................................................................26
        --------
   7.8. Participation in Underwritten Registrations..............................................................27
        -------------------------------------------
ARTICLE VIII.....................................................................................................27
   8.1. Legend...................................................................................................27
        ------
   8.2. Transferees; Additional Restriction on Transfer..........................................................27
        -----------------------------------------------
   8.3. Specific Performance, Etc................................................................................28
        -------------------------
   8.4. Notices..................................................................................................28
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</TABLE>

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<TABLE>
<S>                                                                                                              <C>
   8.5. Entire Agreement; Amendments and Waivers.................................................................28
        ----------------------------------------
   8.6. Termination..............................................................................................28
        -----------
   8.7. Recapitalizations, Exchange, Etc. Affecting the Company's Stock..........................................29
        ---------------------------------------------------------------
   8.8. Preferred Stock Issuance.................................................................................29
        ------------------------
   8.9. Multiple Counterparts....................................................................................29
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   8.10. Additional Signatories..................................................................................29
         ----------------------
   8.11. Headings................................................................................................29
         --------
   8.12. Governing Law...........................................................................................29
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   8.13. Construction............................................................................................29
         ------------
   8.14. Expenses................................................................................................29
         --------
   8.15. Invalidity..............................................................................................30
         ----------
   8.16. Cumulative Remedies.....................................................................................30
         -------------------
</TABLE>
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                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

                  This AMENDED AND RESTATED STOCKHOLDERS AGREEMENT (this
"Agreement") is entered into as of September 19, 2000 by and among Tellium,
Inc., a Delaware corporation (the "Company") and certain of its stockholders who
are from time to time holders of Shares and are parties to this Agreement
(collectively, the "Stockholders").

                                   RECITALS
                                   --------

                  1. The Company and the persons listed on Annex I hereto (each
a "Current Stockholder" and, collectively, the "Current Stockholders") are
parties to an Amended and Restated Stockholders Agreement dated as of December
2, 1999 (the "Existing Stockholders Agreement").

                  2. Pursuant to a Stock Purchase Agreement, dated as of the
date hereof (the "Series E Purchase Agreement"), by and among the Company and
the persons listed on Annex II (each a "Series E Investor" and, collectively,
the "Series E Investors"), the Company has agreed to issue and sell, and the
Series E Investors have agreed to purchase, shares of the Company's Series E
Preferred Stock.

                  3. It is a condition to the obligations of the Series E
Investors and the Company under the Series E Purchase Agreement that this
Agreement be executed by the parties hereto.

                  4. Each of the Current Stockholders and the Company desires to
amend and restate the Existing Stockholders Agreement and, together with the
Series E Investors, enter into this Agreement for the purpose of regulating
certain aspects of the Stockholders' relationships among one another and with
the Company.

                                   AGREEMENT
                                   ---------

          NOW THEREFORE, in consideration of the above recitals and the mutual
covenants herein contained and for other good and valuable consideration, the
parties hereto agree as follows:

                                  ARTICLE I.

                                  DEFINITIONS
                                  -----------

                  As used herein, the following terms shall have the following
meanings:

     1.1. Affiliate. The term "Affiliate" shall mean with respect to any person
          ---------
or entity, any other person or entity directly or indirectly controlling,
controlled by or under common control with such first person or entity (for
purposes of this definition, "control" as used with respect to a person or
entity, shall mean the possession, directly or indirectly, of the power to

                                      -1-
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direct or cause the direction of management and policies of such person or
entity, whether by ownership of voting securities, by contract or otherwise).

     1.2. Common Stock. The term "Common Stock" shall mean the Common Stock of
          ------------
the Company, par value $0.001 per share.

     1.3. Exchange Act. The term "Exchange Act" shall mean the Securities
          ------------
Exchange Act of 1934, as amended.

     1.4. Fully-Diluted Common Stock. The term "Fully-Diluted Common Stock"
          --------------------------
shall mean all of the outstanding Common Stock of the Company, assuming
conversion, exercise or exchange in accordance with their respective terms of
all outstanding convertible, exercisable or exchangeable securities, options,
warrants and similar instruments into or for Common Stock (regardless of whether
such convertible securities are then convertible, exercisable or exchangeable).
As provided in Section 8.7, all such calculations shall be appropriately
adjusted for stock splits, stock dividends and other similar events as described
therein.

     1.5. Holders. The term "Holders" shall mean:
          -------

          (a) with respect to any Demand Registration, Piggyback Registration,
or S-3 Registration, (x) all Current Stockholders who hold Registrable
Securities, and (y) if the Shelf Registration Statement is not then effective,
all Series E Investors who hold Registrable Securities;

          (b) with respect to the Shelf Registration Statement, all Series E
Investors who hold Registrable Securities; and

          (c) with respect to any Registration, any other person who or which,
under the terms of an agreement approved by the Board of Directors is entitled
to the rights of a "Holder" hereunder in connection with such Registration.

     1.6. Liquidation Event. The term "Liquidation Event" shall have the meaning
          -----------------
ascribed thereto in the Company's Certificate of Incorporation.

     1.7. Permitted Transfer. The term "Permitted Transfer" shall mean (i) a
          ------------------
Transfer of Shares among a Stockholder and its respective Related Parties and,
in the case of Thomas Weisel Partners Group LLC ("TWP") and any Related Party
thereof constituting an investment fund established primarily for the benefit of
employees of TWP, a pledge of up to 100,000 shares to secure financing obtained
by the relevant Stockholder provided that upon any transfer upon or in lieu of
foreclosure of such pledge, the transferee is not a competitor of the Company
(as determined in good faith by the Board) and the transferee agrees to be bound
by this Agreement in accordance with Section 8.2, and (ii) Transfers to any
person pursuant to an effective registration statement under the Securities Act;
provided, however, that no such Transfer described above (other than (ii) above)
--------  -------
shall be a Permitted Transfer unless the transferee agrees in writing to be
bound by this Agreement in accordance with the terms of Section 8.2 hereof.

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     1.8.  Preferred Stock. The term "Preferred Stock" shall mean the Preferred
           ---------------
Stock of the Company, par value $0.001 per share, including the Series A
Preferred Stock of the Company, the Series B Preferred Stock of the Company, the
Series C Preferred Stock of the Company, the Series D Preferred Stock of the
Company and the Series E Preferred Stock of the Company.

     1.9.  Qualified IPO. The term "Qualified IPO" shall mean the closing of a
           -------------
firm commitment underwritten public offering of the Company's Common Stock under
the Securities Act which results in gross proceeds to the Company of not less
than $50 million at an offering price per share of Common Stock of not less than
$7.63 (subject to appropriate adjustment to reflect any stock splits, reverse
splits or similar recapitalizations affecting shares of Common Stock).

     1.10. Registrable Securities. The term "Registrable Securities" shall mean:
           ----------------------

           (a) with respect to any Demand Registration, Piggyback Registration
or S-3 Registration, (i) the shares of Common Stock issued upon any one or more
conversions of Preferred Stock (other than the Series E Preferred Stock) or
exercises of Warrants issued to the Current Stockholders, (ii) if the Shelf
Registration Statement is not then effective, the shares of Common Stock issued
upon conversion of the Series E Preferred Stock held by the Series E Investors;

           (b) with respect to the Shelf Registration Statement, the shares of
Common Stock issued upon conversion of the Series E Preferred Stock held by the
Series E Investors; and

           (c) with respect to any Registration, the shares of Common Stock held
by other Holders referred to in Section 1.5(c);

provided, however, that a Registrable Security shall cease to be a Registrable
--------  -------
Security at such time that (i) the Registrable Security has been effectively
registered under the Securities Act and disposed of in accordance with the
registration statement covering it or (ii) has been sold to the public pursuant
to Rule 144 (or any similar provision then in force) under the Securities Act
and any legend required under federal or state securities laws has been removed
from the certificate representing such Registrable Security.

     1.11. Related Party. The term "Related Party" shall mean (i) with respect
           -------------
to any Stockholder, any parent, controlling stockholder, general partner,
controlling member or two-thirds (2/3) or more owned subsidiary of the
Stockholder, (ii) with respect to any Stockholder, a trust, corporation,
partnership, limited liability company or other entity, the beneficiaries,
stockholders, partners, members, owners or persons holding a two-thirds (2/3) or
more controlling interest of which consist of the Stockholder and/or such other
persons or entities referred to in the immediately preceding clause (i), (iii)
with respect to any TWCP Investor, (x) its respective partners, members or
equity holders upon a final liquidation of such TWCP Investor, (y) TWP (together
with any person who succeeds to the business of TWP substantially as an
entirety, collectively, the "TWP Group") and any subsidiaries of the TWP Group
principally engaged in the investment or merchant banking or private investment
business and

                                      -3-
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any investment funds controlled, as general partner, managing
member or otherwise, directly or indirectly, by the TWP Group, (iv) with respect
to TWP, up to four employees of TWP (who may receive an aggregate of up to 9,500
shares (as adjusted for stock splits, stock dividends, reverse splits and the
like)) and (v) with respect to any Series E Investor, any Affiliate of such
Series E Investor.

     1.12. Securities Act. The term "Securities Act" shall mean the Securities
           --------------
Act of 1933, as amended.

     1.13. Shares. The term "Shares" shall mean shares of Preferred Stock, and
           ------
shares of Common Stock issued or issuable upon the conversion of Preferred
Stock. The term "Shares" shall also include the Warrants and the shares of
Preferred Stock and/or Common Stock issuable upon the conversion or exercise of
the Warrants (and the shares of Common Stock issued or issuable upon conversion
of any such Preferred Stock).

     1.14. TWCP Investors. The term "TWCP Investors" shall mean Thomas Weisel
           --------------
Capital Partners, L.P., TWP CEO Founders' Circle (AI), L.P., TWP CEO Founders'
Circle (QP), L.P., Thomas Weisel Partners Group LLC, as nominee, Thomas Weisel
Capital Partners Employee Fund, L.P., TWP 2000 Co-Investment Fund, L.P., TWP
Tellium Investors, Thomas Weisel Capital Partners (Dutch), L.P., and Thomas
Weisel Capital Partners (Dutch II), L.P.

     1.15. Warrants. The term "Warrants" shall mean (a) the 1,742,000 Warrants
           --------
to purchase an aggregate of up to 5,226,000 shares of Common Stock of the
Company issued in connection with the Purchase Agreement dated as of September
21, 1999, between the Company and Extant, Inc. (the "Extant Warrants"), (b) the
Warrants to purchase up to 29,509 shares of Series C Preferred Stock issued or
issuable to Comdisco (the "Comdisco Warrants") and (c) any options, rights or
warrants to acquire Common Stock the holder of which has agreed in writing, with
the written consent of the Company, to become a party to this Agreement, and to
be bound by all of the rights and obligations applicable under this Agreement to
a holder of shares in respect of such options, rights or warrants and the Common
Stock issuable pursuant thereto.

                                      -4-
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                                   ARTICLE II.

                   RESTRICTION ON TRANSFER; COORDINATION WITH
                   ------------------------------------------
                          CERTIFICATE OF INCORPORATION
                          ----------------------------

     So long as this Agreement remains in effect, without the prior written
consent of the other Stockholders, no Stockholder shall transfer, sell, assign,
pledge or otherwise dispose of (each, a "Transfer") any Shares other than in
accordance with the terms of this Agreement. The Company and the Stockholders
agree that the provisions of this Agreement are not intended to conflict with
the liquidation provisions of the Company's Certificate of Incorporation, as in
effect from time to time. Therefore, the Company and the Stockholders hereby
agree that the rights and obligations of the Stockholders with respect to
Transfers contemplated by Section 3.4 and 4.1 are subject to the satisfaction of
the condition that upon the consummation of any such Transfer in a transaction
or series of related transactions that would be treated, as provided in those
sections, as a Liquidation Event pursuant to its Certificate of Incorporation as
in effect at the time of such Transfer, the consideration received in such
Transfer shall be distributed as provided in those sections among all of the
holders of capital stock of the Company in the manner in which such proceeds
would be distributed upon a Liquidation Event pursuant to the rights and
preferences set forth in the Certificate of Incorporation of the Company as in
effect immediately prior to such Transfer. Consideration received in any such
Transfer shall be deemed to include all consideration received by any
Stockholder in any transaction which is consummated substantially
contemporaneously with such Transfer.

                                  ARTICLE III.

                      RIGHT OF FIRST OFFER; TAG-ALONG RIGHT
                      -------------------------------------

     3.1. General. Each time a Stockholder proposes to Transfer Shares to any
          -------
person or persons (a "Proposed Purchaser"), other than pursuant to a Permitted
Transfer (a "Proposed Transfer"), such Stockholder (the "Proposed Seller") shall
first offer all such Shares to the other Stockholders (the "Remaining
Stockholders") in accordance with the terms of Section 3.2 hereof, and the
Remaining Stockholders shall have the option to accept such offer pursuant to
Section 3.3 hereof or, under certain circumstances, to sell Shares to the
Proposed Purchaser pursuant to Section 3.4 hereof.

     3.2. Notice. Prior to consummating any Proposed Transfer, the Proposed
          ------
Seller shall provide the Remaining Stockholders with written notice (the
"Transfer Notice") of the Proposed Transfer, which notice shall offer to
transfer to the Remaining Stockholders, in accordance with Section 3.3 hereof,
the number of Shares proposed to be transferred at the same price per share and
upon the same terms and conditions as the Proposed Seller intends, on a bona
fide basis, to Transfer such Shares. The Transfer Notice shall set forth: (i)
the name of the Proposed Seller and the number of Shares proposed to be
transferred (the "Proposed Shares"), (ii) the name and address of the Proposed
Purchaser, if known, (iii) the proposed amount and form of consideration and
terms and conditions of payment to be made by such Proposed Purchaser, if known,
and (iv) a representation that the Proposed Purchaser, if any, has been informed
of the right of first offer

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and tag-along right provided for in this Article III and has agreed to act in
accordance with the terms hereof.

     3.3. Right of First Offer. Upon receipt of a Transfer Notice, each of the
          --------------------
Remaining Stockholders shall have the option, for a period of 30 days following
the date the Transfer Notice is received by the Remaining Stockholders, to
purchase up to all of the Proposed Shares provided, however, that if the
consideration to be paid for the Proposed Shares set forth in the Transfer
Notice is other than cash, any Remaining Stockholders exercising their option
under this Section 3.3 shall pay in cash the fair market value of such
consideration as determined by an investment banking firm mutually acceptable to
the Proposed Seller and the holders of a majority of Shares held by Remaining
Stockholders who elect to exercise their option, which appraisal shall be final,
within five (5) days of such determination if such determination is made after
30 days following receipt of the Transfer Notice. Such option may be exercised
by any Remaining Stockholder by delivery of written notice of the exercise of
the option to the Proposed Seller, a copy of which shall be sent to all other
Remaining Stockholders which notice shall set forth the maximum number of Shares
proposed to be purchased by the Remaining Stockholder. In the event that the
aggregate number of Shares proposed to be purchased by all Remaining
Stockholders exceeds the number of Proposed Shares (such excess being referred
to in this Section 3.3 as the "Excess"), then the number of Shares that an
exercising Remaining Stockholder shall be entitled to purchase shall be reduced
by the Excess multiplied by a fraction equal to the number of Shares held by
such Stockholder divided by the number of Shares held by all exercising
Remaining Stockholders. If the Remaining Stockholders do not elect to purchase
all of the Proposed Shares, then the Proposed Seller shall have the right,
subject to Section 3.4 hereof, for a period of 90 days after the expiration of
the aforementioned 30-day period to transfer to the Proposed Purchaser (or any
other purchaser) (the actual purchaser, the "Final Purchaser") the Proposed
Shares, but only at a price per share no less and upon the terms and conditions
no more favorable to the purchaser than as set forth in the Transfer Notice;
provided, however, that as a condition to the Transfer of the Shares to such
--------  -------
purchaser, such purchaser shall agree in writing to be bound by this Agreement
in accordance with the terms of Section 8.2 hereof. Any Shares that continue to
be held by the Proposed Seller after any Transfer of Shares to such purchaser
shall again be subject to the restriction on Transfer contained in Section 3.1
hereof. For purposes of any calculation of the number of Shares outstanding
under this Section 3.3, and with respect to any numerator or denominator
provided herein, the conversion, exercise or exchange of all outstanding
securities and the exercise of all outstanding convertible, exercisable or
exchangeable securities into or for Common Stock (regardless of whether such
securities are then convertible, exercisable or exchangeable), including all
Warrants, shall be assumed; provided, that with respect to shares of Series E
                            --------
Preferred Stock, it shall be assumed that such shares are converted pursuant to
Section (E)(1) of Article IV of the Certificate of Incorporation after September
30, 2002. The fees and expenses of any investment banking firm retained in
connection with the determination of the fair market value of the consideration
to be paid for the Proposed Shares hereunder shall be borne proportionately by
the Proposed Seller and each Remaining Stockholder according to the relative
number of the Shares, if any, actually (i) sold by the Proposed Seller to a
third party, and/or (ii) purchased by such Remaining Stockholder.

                                      -6-
<PAGE>

     3.4. Tag-Along Right. In connection with any Proposed Transfer, other than
          ---------------
a Permitted Transfer or a Qualified Transfer (as defined in Section 3.6 below),
each of the Remaining Stockholders shall, in addition to the option specified in
Section 3.3 above, have a "tag-along" right to require the Final Purchaser to
purchase from the Remaining Stockholder a number of whole Shares equal to the
number derived by multiplying the total number of Proposed Shares by a fraction,
the numerator of which is the total number of Shares held by the Remaining
Stockholder and the denominator of which is the total number of Shares held by
all Remaining Stockholders; provided, however, that (i) the tag-along right
                            --------  -------
specified in this Section 3.4 shall terminate in connection with the Proposed
Transfer if one or more Stockholders have exercised their option to purchase
from the Proposed Seller all of the Proposed Shares pursuant to Section 3.3
above and (ii) the tag-along right specified in this Section 3.4 for holders of
Warrants shall only be exercisable with respect to Warrants converted to
Preferred Stock or Common Stock, as applicable, by the holders thereof prior to
exercising such right. Any Shares purchased from a Remaining Stockholder
pursuant to this Section 3.4 shall be paid for in cash, at the same price per
Share and upon the same terms and conditions as set forth in the Transfer
Notice, subject to Section 3.5 below. The tag-along right may be exercised, in
lieu of exercise of the option set forth in Section 3.3 above, by any Remaining
Stockholder by delivery of a written notice of such exercise to the Proposed
Seller (the "Tag-Along Notice") within 30 days following the Remaining
Stockholder's receipt of the Transfer Notice. The Tag-Along Notice shall state
the number of Shares that such Remaining Stockholder proposes to sell to the
Final Purchaser, as determined above (the "Exercise Shares"). Provided that the
Final Purchaser purchases, on the same terms and conditions as set forth in the
Transfer Notice, all Exercise Shares from Remaining Stockholders who timely
deliver Tag-Along Notices, the Proposed Seller shall have the right, for the
90-day period set forth in Section 3.3(a) or 3.3(b), as applicable, to transfer
to the Final Purchaser, on terms and conditions no more favorable than those set
forth in the Transfer Notice, up to a number of Shares equal to the number of
Proposed Shares less the aggregate number of Exercise Shares; provided, however,
                                                              --------  -------
that as a condition to the transfer of the Shares to the Final Purchaser, such
purchaser shall agree in writing to be bound by this Agreement in accordance
with the terms of Section 8.2 hereof. Any Shares that continue to be held by the
Proposed Seller after any transfer of Shares to the Final Purchaser shall again
be subject to the restriction on transfer contained in Section 3.1 hereof. For
purposes of any calculation of the number of Shares outstanding under this
Section 3.4, and with respect to any numerator or denominator provided herein,
the conversion, exercise or exchange of all outstanding securities (regardless
of whether such securities are then convertible, exercisable or exchangeable)
shall be assumed.

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<PAGE>

     3.5. Closing.
          -------

          (a)     At the closing of any sale of Shares pursuant to Section 3.3,
the Proposed Seller shall (i) execute any documents or instruments, including,
without limitation, representations and warranties (as to title, existence and
authorization only), reasonably requested by the Remaining Stockholder(s)
purchasing the Proposed Seller's Shares, and (ii) deliver to such Remaining
Stockholder(s) certificates for the Shares being sold, duly endorsed or
accompanied by duly executed stock assignments separate from certificate, free
and clear of all claims and encumbrances, against delivery by such Remaining
Stockholder(s) of the consideration (including a certified check for the cash
portion of such consideration) for the total sales price of the Shares being
sold.

          (b) (i) At the closing of any sale of Shares pursuant to Section 3.4,
the Remaining Stockholder(s) selling Shares to the Final Purchaser shall (i)
execute any documents or instruments, including, without limitation,
representations and warranties (as to title, existence and authorization only),
reasonably requested by the Final Purchaser, and (ii) deliver to Final Purchaser
certificates for the Shares being sold, duly endorsed or accompanied by duly
executed stock assignments separate from certificate, free and clear of all
claims and encumbrances, against delivery by Final Purchaser of the
consideration (including a certified check for the cash portion of such
consideration) for the total sales price of the Shares being sold.

          (ii)    If any transaction as to which Remaining Stockholders have
exercised tag-along rights pursuant to Section 3.4 would not be treated as a
Liquidation Event pursuant to the Certificate of Incorporation of the Company as
then in effect, but nevertheless involves the sale of all or more than 50% of
the voting capital stock (as defined in the Certificate of Incorporation) of the
Company to the Final Purchaser and its Affiliates and any other persons with
whom the Final Purchaser is a member of a "group" (as defined under Regulation
13D under the Exchange Act), the Company and the Stockholders hereby agree that
it shall be a condition of any such closing that each holder of Preferred Stock
shall receive in respect of each share of Preferred Stock an amount of
consideration equal to the consideration that such holder would have received if
such transaction constituted a Liquidation Event and the aggregate consideration
being paid by the Final Purchaser divided by the percentage of the Fully-Diluted
Common Stock being acquired by the Final Purchaser in the transaction were
distributed to the holders of capital stock in accordance with the provisions of
paragraph D of Article IV of the Certificate of Incorporation of the Company.

     3.6. Qualified Transfer. As used herein, the term "Qualified Transfer"
          ------------------
shall mean one or more transfers which do not result in the cumulative
disposition since the date hereof of more than 1,500,000 Shares of Fully-Diluted
Common Stock (subject to adjustment for stock splits, reverse stock splits,
stock dividends, stock combinations and the like) held by the transferor and its
Related Parties; provided, however, that no such transfer shall be a Qualified
                 --------  -------
Transfer unless the transferee agrees in writing to be bound by this Agreement
in accordance with the terms of Section 8.2 hereof.

                                      -8-
<PAGE>

     3.7. Company Effecting Transfers. The Company agrees not to effect any
          ---------------------------
transfer of Shares by a Stockholder until it has received evidence reasonably
satisfactory to it that the Stockholder has complied with this Article III.

     3.8. Termination of Right of First Offer and Tag-Along Right. The right of
          -------------------------------------------------------
first offer and tag-along right provided under this Article III shall terminate
upon a Qualified IPO.

                                  ARTICLE IV.

                               DRAG-ALONG RIGHT
                               ----------------

     4.1. Drag-Along Right. With respect to any proposed transfer, sale or other
          ----------------
disposition which is not a Permitted Transfer (a "Proposed Drag-Along Transfer")
by one or more Stockholders (the "Proposed Transferors") of Shares comprising a
majority of the outstanding Shares held by all Stockholders to a proposed bona
fide purchaser (a "Proposed Transferee"), the Proposed Transferors shall have a
"drag-along" right to require all Stockholders to sell all (but not less than
all) of their Shares (assuming, in the case of Warrants, exercise or conversion
into Common Stock or Preferred Stock in accordance with its terms) in the
Proposed Drag-Along Transfer to the Proposed Transferee at the same price per
Share and upon the same terms and conditions as the Proposed Drag-Along Transfer
by the Proposed Transferors, subject to Section 4.2 below. The Proposed
Transferors shall, not less than 45 nor more than 90 days prior to the Proposed
Drag-Along Transfer, notify, or cause to be notified, each of the other
Stockholders and the Company in writing of such Proposed Drag-Along Transfer.
Such notice (the "Drag-Along Notice") shall set forth: (i) a statement that the
Proposed Transferors intend to sell all of its Shares in the Proposed Drag-Along
Transfer, (ii) the name and address of the Proposed Transferee, (iii) the
proposed amount and form of consideration and terms and conditions of payment
offered by such Proposed Transferee and (iv) that the Proposed Transferee has
been informed of the drag-along right provided for in this Article IV and has
agreed to purchase the Shares held by the Stockholders in accordance with the
terms hereof.

     4.2. Closing. At the closing of the transfer to the Proposed Transferee (of
          -------
which the Proposed Transferors shall give each of the other Stockholders at
least 10 business days' prior written notice), each Stockholder shall (i)
execute any documents or instruments, including, without limitation,
representations and warranties (as to title, existence and authorization only)
reasonably requested by the Proposed Transferee, and (ii) deliver certificates
for the Shares being sold, duly endorsed or accompanied by duly executed stock
assignments separate from certificate, free and clear of all claims and
encumbrances, against delivery by the Proposed Transferee to each Stockholder of
the consideration (including a certified check for the cash portion of such
consideration) for the total sales price of all Shares of such Stockholder. The
Company and the Stockholders hereby agree that it shall be a condition of any
such closing that each holder of Preferred Stock shall receive in respect of
each share of Preferred Stock an amount of consideration equal to the
consideration that such holder would have received in such transaction if such
transaction constituted a Liquidation Event and the aggregate consideration
being paid by the Proposed Transferee divided by the percentage of the
Fully-Diluted Common Stock being acquired by the Proposed Transferee in the
transaction were distributed to the

                                      -9-
<PAGE>

holders of capital stock in accordance with the provisions of paragraph D of
Article IV of the Certificate of Incorporation of the Company.

     4.3. Termination of Drag-Along Right. The drag-along right provided under
          -------------------------------
this Article IV shall terminate upon a Qualified IPO.

                                  ARTICLE V.

                              RIGHTS TO CO-INVEST
                              -------------------

     5.1. General. If the Company proposes to newly-issue for cash (a "Proposed
          -------
Issuance") any of its equity securities (the "Securities"), then the Company
shall, no later than 20 days prior to the consummation of such issuance, give
written notice to each of the Current Stockholders of such proposed issuance.
Such notice shall describe the proposed issuance and shall contain an offer to
each Qualified Offeree (as defined in Section 5.2 below) to sell to such
Qualified Offeree, at the same price and for the same consideration to be paid
by the proposed purchasers, such Qualified Offeree's pro rata portion (which
shall be a percentage equal to the number of shares of Fully-Diluted Common
Stock (excluding any shares of Series E Preferred Stock or Common Stock issuable
upon conversion thereof) held by such Qualified Offeree divided by the total
number of shares of Fully-Diluted Common Stock; provided, however, that if the
                                                --------  -------
use of proceeds of the Proposed Issuance shall include the repurchase of Common
Stock or Preferred Stock permitted by the Company's Certificate of
Incorporation, as then in effect, or as to which the Qualified Offeree has
agreed, then such percentage shall be calculated assuming the consummation of
such repurchase) of the Securities to be sold; provided, however, that any
                                               --------  -------
Securities offered to Lucent Technologies Inc. ("Lucent") or its Affiliates
shall include such number of securities that are non-voting while held by Lucent
or its Affiliates and, with respect to convertible Securities, that are not
convertible into voting securities while held by Lucent or its Affiliates except
upon a Qualified IPO (but otherwise having rights, preferences and privileges
that are identical to those of the Securities) as may be requested by Lucent.
Subject to the foregoing, if Common Stock is being issued with other Securities
as a unit, each Qualified Offeree who desires to accept such offer must purchase
such unit in order for such acceptance to be valid; provided, however, that any
                                                    --------  -------
such unit offered to Lucent shall include securities that are non-voting or
convertible into non-voting securities as described above. If any such Qualified
Offeree fails to accept such offer by written notice within 15 days after the
Company's notice, the Company may proceed with such proposed issuance, free of
any right on the part of such Qualified Offeree under this Section 5.1 in
respect thereof.

     5.2. Qualified Offeree. For purposes of this Article V, a "Qualified
          -----------------
Offeree" shall include only a Current Stockholder which is an "accredited
investor" for purposes of Rule 501 under the Securities Act and is a Current
Stockholder party to this Agreement.

     5.3. Exemptions. The rights granted by Section 5.1 shall not apply to:
          ----------

     (i)  (A) up to 20,425,000 shares of Common Stock (as adjusted for stock
splits, reverse splits, recapitalizations and the like) issued or issuable
pursuant to any stock option plan,

                                     -10-
<PAGE>

stock purchase plan or restricted stock plan adopted by the Board of Directors
(or the compensation committee thereof) for employees and consultants (including
officers, directors, consultants and other persons rendering or to be rendering
services to the Company or its subsidiaries) of the Company or its subsidiaries
(inclusive of all options outstanding as of the date hereof under the Amended
and Restated 1997 Stock Option Plan of the Company as amended on or prior to the
date hereof and any options issued upon expiration or termination of any such
outstanding options);

            (B) shares of Common Stock issued or issuable pursuant to any stock
option plan, stock purchase plan or restricted stock plan adopted by at least
two-thirds (66-2/3%) of the Board of Directors for employees and consultants
(including officers, directors, consultants and other persons rendering or to be
rendering services to the Company or its subsidiaries) of the Company or its
subsidiaries; and

            (C) shares of Common Stock issued or issuable to the first chief
executive officer of the Company appointed to such position on or after the date
hereof pursuant to any stock option plan, stock purchase plan or restricted
stock plan adopted by the Board of Directors (or the compensation committee
thereof).

     (ii)   issuances of shares of Series E Preferred Stock pursuant to the
Series E Purchase Agreement;

     (iii)  issuances of Common Stock upon the conversion of Preferred Stock
issued on or prior to the date hereof or acquired pursuant to the Series E
Purchase Agreement,

     (iv)   any issuance of securities in connection with a Qualified IPO,

     (v)    issuances of securities upon exercise of the Comdisco Warrants or
conversion of the Preferred Stock acquired thereon and issuances of Common Stock
upon exercise of the Extant Warrants,

     (vi)   issuances of securities pursuant to the acquisition of another
business entity or business segment of any such entity by the Company by merger,
purchase of substantially all the assets or other reorganization,

     (vii)  issuances of securities in connection with any stock split, stock
dividend or similar recapitalization of the Company,

     (viii) issuances of securities to vendors, customers or other persons in
similar commercial situations with the Company (or to affiliates of any such
persons), if such issuance is approved by the Board,

     (ix)   issuances of up to 3,750,000 shares of Common Stock to be issued
pursuant to the Agreement and Plan of Merger, by and among the Corporation and
Astarte Acquisition Corporation, Astarte Fiber Networks, Inc., AFN LLC and Aron
B. Katz, dated as of August 29, 2000,

                                     -11-
<PAGE>

     (x)    issuances of up to 1,500,000 shares of Common Stock to be issued
pursuant to the Stock Purchase Agreement, by and among the Corporation and AT&T
Corp., dated as of September 1, 2000,

     (xi)   issuances of securities in connection with obtaining lease
financing, whether issued to a lessor, guarantor or other person,

     (xii)  issuances of securities together as a unit with the issuance of any
debt of the Company (commonly known as "equity kickers"), and

     (xiii) any right, option or warrant to acquire any security convertible
into securities exempted pursuant to clauses (i) through (xii) above.

     5.4.   Termination of Rights. The rights provided under this Article V
            ---------------------
shall terminate upon a Qualified IPO.

                                  ARTICLE VI.
                              BOARD OF DIRECTORS
                              ------------------

     6.1.   Membership Generally. The Company and the Stockholders hereby agree
            --------------------
to take, at any time and from time to time, all action necessary (including,
without limitation, voting the Shares owned by them, causing the appropriate
officers of the Company to call one or more special meetings of stockholders and
executing and delivering written consents) such that the Board shall have eight
(8) members and shall consist of:

     (a)    two (2) directors designated by Telcordia Venture Capital
            Corporation in its sole discretion;

     (b)    one (1) director designated by Oak Investment Partners VII Limited
            Partnership in its sole discretion;

     (c)    one (1) director designated by Thomas Weisel Capital Partners, L.P.
            in its sole discretion;

     (d)    the Company's Chief Executive Officer;

     (e)    the Company's Chairman of the Board (or a director nominated by the
            Company's Chief Executive Officer and approved by a majority vote of
            the remaining directors, if the same person holds the positions of
            Chief Executive Officer and Chairman of the Board); and

     (f)    two (2) independent directors designated by majority vote of the
            remaining directors.

                                     -12-
<PAGE>

     6.2. Committees. The Stockholders and the Company agree to take such action
          ----------
as is necessary to ensure that the one board member designated by TWCP shall be
entitled to serve on all standing committees of the Board of Directors,
including the audit, compensation and executive committees (if any such
committees exist from time to time), and the presently constituted search
committee of the Board of Directors which has been created to hire and negotiate
the terms of employment of the next Chief Executive Officer of the Company.

     6.3. Removal. If a director has been designated by a Stockholder and
          -------
elected pursuant to this Article VI and if such Stockholder requests that such
director be removed (with or without cause) by written notice thereof to the
other Stockholders, then each Stockholder agrees to take all actions required to
effect such result, including, without limitation, the actions specified in
Section 6.1 hereof.

     6.4. Vacancies. In the event that a vacancy is created on the Board of
          ---------
Directors at any time by the death, disability, retirement, resignation or
removal of a director or otherwise, each Stockholder agrees to cause the
director(s) designated by such Stockholder to vote for that individual
designated to fill such vacancy and serve as a director by whichever of the
Stockholders that had designated, pursuant to Section 6.1, the director whose
death, disability, retirement, resignation or removal resulted in such vacancy
on the Board of Directors.

     6.5. Certain Actions. The consent of a majority of the entire Board of
          ---------------
Directors (other than the Chief Executive Officer and the Chairman of the Board
and, in the case of clause (ii), other than the directors, if any, interested in
such transaction) shall be required for any action which (i) causes the Company
to incur any indebtedness for borrowed money in excess of $500,000 in the
aggregate or causes the Company to guarantee any indebtedness for borrowed money
in excess of $500,000 in the aggregate or (ii) causes the Company to engage in
any transaction (other than compensation awards (including stock option,
restricted stock and other awards) approved by the Board of Directors or the
compensation committee thereof, the reimbursement of business related expenses
in the ordinary course of business and other transactions on an arms' length
basis approved by the Board of Directors) with any officer, director or employee
of the Company or any member of the immediate family of any officer, director or
employee of the Company or causes the Company to engage in any transaction with
any corporation, partnership, limited liability company or other entity in which
any officer, director or employee of the Company or any member of the immediate
family of any officer, director or employee of the Company is an officer,
director, partner, member or employee.

     6.6. Termination. The provisions of this Article VI shall terminate upon a
          -----------
Qualified IPO.

                                     -13-
<PAGE>

                                 ARTICLE VII.
                              REGISTRATION RIGHTS
                              -------------------

     7.1. Piggyback Registration Rights.
          -----------------------------

     (a)  Right to Piggyback. After the date 180 days after the Company's
          ------------------
initial public offering, and subject to Sections 7.1(b) and 7.1(c) below,
whenever the Company proposes to register any shares of Common Stock (or
securities convertible into or exercisable or exchangeable for, or options to
purchase, Common Stock) with the Securities and Exchange Commission (the
"Commission") under the Securities Act (other than pursuant to a registration on
Form S-4 or S-8, or any successor forms thereto) (a "Piggyback Registration"),
the Company (i) will give written notice to all Holders at least 30 days prior
to the anticipated filing date, of its intention to effect such a registration,
which notice will specify the proposed offering price, the kind and number of
securities proposed to be registered, the distribution arrangements and such
other information that at the time would be appropriate to include in such
notice, and (ii) will, subject to Section 7.1(c) below, include in such
Piggyback Registration all Registrable Securities with respect to which the
Company has received written requests for inclusion therein within 20 days after
the date of the Company's notice. Except as may otherwise be provided in this
Agreement, Registrable Securities with respect to which such request for
registration has been received will be registered by the Company and offered to
the public in a Piggyback Registration pursuant to this Article VII on terms and
conditions at least as favorable as those applicable to the registration of
shares of Common Stock to be sold by the Company and by any other person selling
under such Piggyback Registration.

     (b)  Number of Piggyback Registrations. Each Holder shall be entitled to
          ---------------------------------
unlimited Piggyback Registrations, and the expenses of each Holder (including
the fees and expenses of a total of one counsel for the selling Holders in
accordance with Section 7.5(b) below) shall be borne by the Company in
accordance with the provisions of Section 7.5 hereof.

     (c)  Priority on Piggyback Registrations. If the managing underwriter or
          -----------------------------------
underwriters, if any, advise the selling Holders in writing that in its or their
reasonable opinion or, in the case of a Piggyback Registration not being
underwritten, the Company shall reasonably determine (and notify the selling
Holders of such determination), after consultation with an investment banker of
nationally recognized standing, that the number or kind of securities proposed
to be sold in such registration (including Registrable Securities to be included
pursuant to Section 7.1(a) above) is inconsistent with that which can be sold in
such registration without having a material effect on the success of the
offering (including, without limitation, an impact on the selling price or the
number of securities that any participant may sell), the Company will include in
such registration the number of securities, if any, which, in the opinion of
such underwriter or underwriters, or the Company, as the case may be, can be
sold as follows: (i) first, the shares the Company proposes to sell, and (ii)
second, the Registrable Securities requested to be included in such registration
by the Holders. To the extent that the privilege of including Registrable
Securities in any Piggyback Registration must be allocated among the selling
Holders pursuant to clause (ii) above, the allocation shall be made pro rata
based on the number of shares of Common Stock then owned by such Holders.

                                     -14-
<PAGE>

     (d)   Selection of Underwriters. If any Piggyback Registration is an
           -------------------------
underwritten offering, the Company will (i) select a managing underwriter or
underwriters to administer the offering, which managing underwriter or
underwriters will be of nationally recognized standing, and (ii) determine the
terms under which such underwriting shall take place.

     7.2.  Demand Registration Rights; Form S-3 Registration Rights; Shelf
           ---------------------------------------------------------------
Registration.
------------

     (a)   Right to Demand.
           ---------------

     (i)   After the earlier of (A) a Qualified IPO or (B) May 8, 2002, one or
more Holders may make a written request of the Company for registration with the
Commission, under and in accordance with the provisions of the Securities Act,
of all or part of their Registrable Securities.

     (ii)  After the earlier of (a) a Qualified IPO or (B) May 8, 2002, the
holders of at least a majority of the then-outstanding Registrable Securities
issued or issuable upon conversion of the Series D Preferred Stock of the
Company issued to the TWCP Investors (including resulting from splits,
combinations and similar recapitalizations resulting from such shares) may make
a written request for registration with the Commission under and in accordance
with the provisions of the Securities Act, of all or part of their Registrable
Securities.

     (iii) Any Holder(s) which request registration under Section 7.2(a)(i) or
(ii) are hereinafter referred to as "Demanding Holder(s)" and any such
registration is hereinafter referred to as a "Demand Registration." The rights
to registration under this Section 7.2(a) are limited as follows:

           (A) no such request for registration may be made within 180 days
after the effective date of a registration statement under the Securities Act
covering any of the Company's equity securities;

           (B) the anticipated offering price of all Registrable Securities
subject to the Demanding Holder(s)' request must equal or exceed $20 million in
the aggregate;

           (C) the Company need not effect more than two Demand Registrations
under Section 7.2(a)(i) (other than Demand Registrations on Form S-3, as to
which this clause (C) shall not apply);

           (D) the Company need not effect more than one Demand Registration
under Section 7.2(a)(ii) (other than Demand Registration on Form S-3, as to
which this clause (D) shall not apply);

           (E) the Company need not effect a Demand Registration described in
Section 7.2(a)(i) unless such Demand Registration shall include at least 25% of
the Registrable Securities then outstanding on the date the request is made;

           (F) the Company may, if the Board of Directors determines in the
exercise of its reasonable judgment that effecting such Demand Registration at
such time would have a material

                                     -15-
<PAGE>

adverse effect on the Company, defer such Demand Registration for a single
period not to exceed 90 days; and

         (G) if the Company elects to defer any Demand Registration pursuant
to (F) above, no Demand Registration shall be deemed to have occurred for
purposes of this Agreement.

Within 10 days after receipt of the request for a Demand Registration, the
Company will send written notice (the "Notice") of such registration request and
its intention to comply therewith to each of the other Holders and, subject to
Section 7.2(e) below, the Company will include in such registration all
Registrable Securities of such Holders with respect to which the Company has
received written requests for inclusion therein within 20 business days after
the effectiveness of the Notice. All requests made pursuant to this Section
7.2(a) will specify the aggregate number of Registrable Securities requested to
be registered and will also specify the intended methods of disposition thereof.

     (b) Form S-3 Registration. After the Company has qualified for the use of
         ---------------------
Form S-3 or any successor form, in addition to the rights contained in Section
7.2(a), any Holder shall have the right to request registrations of Registrable
Securities on Form S-3, so long as the anticipated gross offering price of the
Registrable Securities requested to be registered exceeds $1 million (such
requests shall be in writing and shall state the number of shares of Registrable
Securities to be disposed of and the intended methods of disposition of such
shares); provided, however, that the Company shall not be obligated to file more
         --------  -------
than one Form S-3 in any twelve-month period. Any such registration shall not be
                                                                          ---
counted as a registration pursuant to Section 7.2(a). Notwithstanding the
foregoing, the Company shall not be required to effect registration under this
Section 7.2(b) if the party requesting registration may, pursuant to Rule 144
under the Securities Act or otherwise publicly sell the Registrable Securities
without registration under the Securities Act and without any limitation with
respect to offerees, manner of offering or the size of the transaction. Any
registration effected under this Section 7.2(b) shall be referred to as a "Form
S-3 Registration."

     The rights to registration under this Section 7.2(b) are limited as
follows:

         (A) no such request for registration may be made within 180 days after
the effective date of a registration statement under the Securities Act covering
any of the Company's equity securities;

         (B) the Company may, if the Board of Directors determines in the
exercise of its reasonable judgement that effecting such Form S-3 Registration
at such time would have a material adverse effect on the Company, defer such
Form S-3 Registration for a single period not to exceed 90 days; and

         (C) if the Company elects to defer any Form S-3 Registration pursuant
to (B) above, no Form S-3 Registration shall be deemed to have occurred for
purposes of this Agreement.

                                     -16-
<PAGE>

Within 10 days after receipt of the request for a Form S-3 Registration, the
Company will send a Notice of such registration request and its intention to
comply therewith to each of the other Holders and, subject to Section 7.2(d)
below, the Company will include in such registration all Registrable Securities
of such Holders with respect to which the Company has received written requests
for inclusion therein within 20 business days after the effectiveness of the
Notice. All requests made pursuant to this Section 7.2(b) will specify the
aggregate number of Registrable Securities requested to be registered and will
also specify the intended methods of disposition thereof.

     (c) Shelf Registration. The Company shall cause to be filed with the
         ------------------
Commission on or prior to 60 days after the closing date of the Company's
initial Qualified IPO, a shelf registration statement pursuant to Rule 415 under
the Act (as may then be amended) (the "Shelf Registration Statement") on Form
S-1 or Form S-3, if the use of such form is then available and as determined by
the Company, to cover resales of Registrable Securities by the Holders thereof
who complete and execute all customary questionnaires, powers of attorney,
indemnities and other documents reasonably required by the Company in connection
with the Shelf Registration Statement. The Company shall use its reasonable best
efforts to cause such Shelf Registration Statement to be declared effective by
the Commission on or prior to 90 days after the closing date of its initial
Qualified IPO. The Company shall use its reasonable best efforts to keep such
Shelf Registration Statement continuously effective for a period ending two
years from the effective date thereof or such shorter period that will terminate
when each of the Registrable Securities covered by the Shelf Registration
Statement shall cease to be a Registrable Security.

     (d) Expenses; Exceptions. The expenses of each Demand Registration, Form
         --------------------
S-3 Registration and the Shelf Registration Statement (including the fees and
expenses of a total of one counsel for the selling Holders in accordance with
Section 7.5(b) below) shall be borne by the Company in accordance with the
provisions of Section 7.5 hereof. A Demand Registration or a Form S-3
Registration shall not be counted as a Demand Registration or a Form S-3
Registration, as the case may be, until such Demand Registration or Form S-3
Registration, as applicable, has been declared effective by the Commission and
maintained continuously effective for a period of at least six months or such
shorter period when all Registrable Securities included therein have been sold
in accordance therewith. If the Company elects to issue and sell any equity
securities pursuant to any Registration Statement filed in connection with a
Demand Registration or if the number of Registrable Securities that Holders are
entitled to sell in a Demand Registration is reduced in accordance with Section
7.2(e) below, then such Registration shall be deemed not to be a Demand
Registration solely for purposes of determining the number of Demand
Registrations granted by this Section 7.2.

     (e) Priority on Demand Registrations. If in any underwritten Demand
         --------------------------------
Registration or Form S-3 Registration the managing underwriter or underwriters
thereof (or in the case of a Demand Registration or Form S-3 not being
underwritten, in the opinion of the holders of a majority of the Registrable
Securities included therein), advise the Company in writing that in its or their
reasonable opinion the number of securities proposed to be sold in such Demand
Registration or Form S-3 Registration, as applicable, is inconsistent with that
which can be sold in such offering without having a material effect on the
success of the offering (including, without limitation, an impact on the selling
price or the number of Registrable Securities that any

                                     -17-
<PAGE>

participating Holder may sell), the Company will include in such registration
only the number of securities that, in the reasonable opinion of such
underwriter or underwriters (or holders of Registrable Securities, as the case
may be) can be sold without having a material adverse effect on the success of
the offering as follows: (i) first, the Registrable Securities requested to be
included in such Demand Registration or Form S-3 Registration, as applicable, by
the Holders (including the Demanding Holder(s)) pro rata based on the total
number of shares of Common Stock then owned by such Holders, and (ii) second,
any securities held by persons other than the Holders and requested to be
included in such Demand Registration or Form S-3 Registration, as applicable.

     (f) Selection of Underwriters. If any Demand Registration or Form S-3
         -------------------------
Registration is an underwritten offering, the Company will (i) select a managing
underwriter or underwriters to administer the offering, which managing
underwriter or underwriters shall be of nationally recognized standing and
reasonably acceptable to Demanding Holder(s) (or requesting holder(s), in the
case of a Form S-3 Registration) holding a majority of the Registrable
Securities requested to be included therein, and (ii) determine the terms under
which such underwriting shall take place, which terms shall be reasonably
acceptable to the Demanding Holder(s) (or requesting holder(s), in the case of a
Form S-3 Registration).

     7.3. Registration Procedures. With respect to the Shelf Registration
          -----------------------
Statement or any Piggyback Registration, Demand Registration or Form S-3
Registration (generically, a "Registration"), the Company will, subject to
Sections 7.1(c) and 7.2(e), as expeditiously as practicable:

     (a) within 90 days after mailing the applicable Notice, in the case of any
Piggyback Registration, Demand Registration or S-3 Registration, or within 60
days after the closing date of the Company's initial Qualified IPO, in the case
of the Shelf Registration Statement, prepare and file with the Commission, a
registration statement or registration statements (the "Registration Statement")
relating to the applicable Registration on any appropriate form under the
Securities Act, which form shall be available for the sale of the Registrable
Securities in accordance with the intended method or methods of distribution
thereof; provided, however, that the Company will include in any Registration
         --------  -------
Statement on a form all information that the selling Holders shall reasonably
request and shall include all financial statements required by the Commission to
be filed therewith, cooperate and assist in any filings required to be made with
the National Association of Securities Dealers, Inc. ("NASD"), and use its best
efforts to cause such Registration Statement to become effective; provided
                                                                  --------
further that before filing a Registration Statement or prospectus related
-------
thereto (a "Prospectus") or any amendments or supplements thereto, the Company
will furnish to the Holders covered by such Registration Statement and the
underwriters, if any, copies of all such documents proposed to be filed, which
documents will be subject to the reasonable review of such Holders and
underwriters and their respective counsel, and the Company will not file any
Registration Statement or amendment thereto or any Prospectus or any supplement
thereto to which the holders of a majority of the Registrable Securities covered
by such Registration Statement or the underwriters, if any, shall reasonably
object;

                                     -18-
<PAGE>

     (b) prepare and file with the Commission such amendments and post-effective
amendments to the Registration Statement as may be necessary to keep each
Registration Statement effective for the applicable period, or such shorter
period which will terminate when all Registrable Securities covered by such
Registration Statement have been sold; cause each Prospectus to be supplemented
by any required Prospectus supplement, and as so supplemented to be filed
pursuant to Rule 424 under the Securities Act; and comply with the provisions of
the Securities Act with respect to the disposition of all securities covered by
such Registration Statement during the applicable period in accordance with the
intended method or methods of distribution by the sellers thereof set forth in
such Registration Statement or supplement to the Prospectus; the Company shall
not be deemed to have used its best efforts to keep a Registration Statement
effective during the applicable period if it voluntarily takes any action that
would result in selling Holders covered thereby not being able to sell such
Registrable Securities during that period unless such action is required under
applicable law, provided that the foregoing shall not apply to actions taken by
the Company in good faith and for valid business reasons, including, without
limitation, the acquisition or divestiture of assets, so long as the Company
promptly thereafter complies with the requirements of Section 7.3(k) below, if
applicable;

     (c) notify the selling Holders and the managing underwriters, if any,
promptly, and (if requested by any such person or entity) confirm such advice in
writing, (A) when the Prospectus or any Prospectus supplement or post-effective
amendment has been filed, and, with respect to the Registration Statement or any
post-effective amendment, when the same has become effective, (B) of any request
by the Commission for amendments or supplements to the Registration Statement or
the Prospectus or for additional information, (C) of the issuance by the
Commission of any stop order suspending the effectiveness of the Registration
Statement or the initiation of any proceedings for that purpose, (D) if at any
time the representations and warranties of the Company contemplated by Section
7.3(n) below cease to be true and correct, (E) of the receipt by the Company of
any notification with respect to the suspension of the qualification of the
Registrable Securities for sale in any jurisdiction or the initiation or
threatening of any proceeding for such purpose and (F) of the happening of any
event which makes any statement made in the Registration Statement, the
Prospectus or any document incorporated therein by reference untrue or which
requires the making of any changes in the Registration Statement, the Prospectus
or any document incorporated therein by reference in order to make the
statements therein not misleading;

     (d) make every reasonable effort to obtain the withdrawal of any order
suspending the effectiveness of the Registration Statement at the earliest
possible moment;

     (e) if requested by the managing underwriter or underwriters or a holder of
Registrable Securities being sold in connection with an underwritten offering,
promptly incorporate in a Prospectus supplement or post-effective amendment such
information as the managing underwriters and the holders of a majority of the
Registrable Securities being sold agree should be included therein relating to
the plan of distribution with respect to such Registrable Securities, including,
without limitation, information with respect to the number of Registrable
Securities being sold to such underwriters, the purchase price being paid
therefor by such underwriters and with respect to any other terms of the
underwritten offering of the Registrable Securities to be sold in such offering;
and make all required filings of such

                                     -19-
<PAGE>

Prospectus supplement or post-effective amendment as soon as notified of the
matters to be incorporated in such Prospectus supplement or post-effective
amendment;

     (f) furnish to each managing underwriter and, if requested by the holders
of a majority of the Registrable Securities being sold, to each selling Holder,
without charge, at least one signed copy of the Registration Statement and any
amendment thereto, including financial statements and schedules, all documents
incorporated therein by reference and all exhibits (including those incorporated
by reference);

     (g) deliver to each selling Holder and the underwriters, if any, without
charge, as many copies of the Prospectus (including each preliminary prospectus)
and any amendment or supplement thereto as such Holder and underwriters may
reasonably request; the Company consents to the use of each Prospectus or any
amendment or supplement thereto by each of the selling Holders and the
underwriters, if any, in connection with the offering and sale of the
Registrable Securities covered by such Prospectus or any amendment or supplement
thereto;

     (h) prior to any public offering of Registrable Securities, register or
qualify or cooperate with the selling Holders, the underwriters, if any, and
their respective counsel in connection with the registration or qualification of
such Registrable Securities for offer and sale under the securities or "Blue
Sky" laws of such jurisdictions as any seller or underwriter reasonably requests
in writing, considering the amount of Registrable Securities proposed to be sold
in each such jurisdiction, and do any and all other acts or things necessary or
advisable to enable the disposition in such jurisdictions of the Registrable
Securities covered by the Registration Statement; provided, however, that the
                                                  --------  -------
Company will not be required to qualify generally to do business in any
jurisdiction where it is not then so qualified or to take any action that would
subject it to general service of process in any such jurisdiction where it is
not then so subject;

     (i) cooperate with the selling Holders and the managing underwriters, if
any, to facilitate the timely preparation and delivery of certificates
representing Registrable Securities to be sold and not bearing any restrictive
legends and in such denominations and registered in such names as the managing
underwriters may request at least two business days prior to any sale of
Registrable Securities to the underwriters;

     (j) use its best efforts to cause the Registrable Securities covered by the
applicable Registration Statement to be registered with or approved by such
other governmental agencies or authorities as may be necessary to enable the
seller or sellers thereof or the underwriters, if any, to consummate the
disposition of such Registrable Securities;

     (k) upon the occurrence of any event contemplated by Section 7.3(c)(F)
above, prepare a supplement or post-effective amendment to the Registration
Statement or the related Prospectus or any document incorporated therein by
reference or file any other required document so that, as thereafter delivered
to the purchasers of the Registrable Securities, the Prospectus will not contain
an untrue statement of a material fact or omit to state any material fact
necessary to make the statements therein not misleading;

                                     -20-
<PAGE>

     (l) cause all Registrable Securities covered by any Registration Statement
to be listed on each securities exchange on which similar securities issued by
the Company are then listed, or cause such Registrable Securities to be
authorized for trading on the NASDAQ National Market System if any similar
securities issued by the Company are then so authorized, if requested by the
holders of a majority of such Registrable Securities or the managing
underwriters, if any;

     (m) provide a CUSIP number for all Registrable Securities, not later than
the effective date of the applicable Registration Statement;

     (n) enter into such agreements (including an underwriting agreement) and
take all such other actions in connection therewith in order to facilitate the
disposition of such Registrable Securities as shall be reasonably necessary, and
in connection therewith, (A) make such representations and warranties to the
selling Holders and the underwriters, if any, in form, substance and scope as
are customarily made by issuers to underwriters in primary underwritten
offerings; (B) obtain opinions of counsel to the Company and updates thereof
(which counsel and opinions (in form, scope and substance) shall be reasonably
satisfactory to the managing underwriters, if any, and the holders of a majority
of the Registrable Securities being sold) addressed to each selling Holder and
the underwriters, if any, covering the matters customarily covered in opinions
requested in underwritten offerings and such other matters as may be reasonably
requested by such Holders and underwriters; (C) obtain "cold comfort" letters
and updates thereof from the Company's independent certified public accountants
addressed to the underwriters, if any, such letters to be in customary form and
covering matters of the type customarily covered in "cold comfort" letters by
underwriters in connection with primary underwritten offerings; (D) if an
underwriting agreement is entered into, the same shall set forth in full the
indemnification provisions and procedures set forth in Section 7.6 below with
respect to all parties to be indemnified pursuant to said Section; (E) the
Company shall deliver such documents and certificates as may be requested by the
holders of a majority of the Registrable Securities being sold and the managing
underwriters, if any, to evidence compliance with Section 7.3(c)(F) above and
with any customary conditions contained in the underwriting agreement or other
agreement entered into by the Company and (F) make its employees and personnel
(including senior executive officers of the Company) reasonably available and
otherwise provide reasonable assistance to the underwriters (taking into account
the requirements of the marketing process) of Registrable Securities in any
underwritten offering, including participation in any road show related thereto.
The above shall be done at each closing under such underwriting or similar
agreement or as and to the extent required thereunder;

     (o) make available for inspection during normal business hours by a
representative of the holders of a majority of the Registrable Securities, any
underwriter participating in any distribution pursuant to such Registration, and
any attorney or accountant retained by the representative or underwriter, all
financial and other records, and pertinent corporate documents of the Company,
and cause the Company's officers, directors and employees to supply all
information reasonably requested by any such representative, underwriter,
attorney or accountant in connection with such Registration Statement; provided,
                                                                       --------
however, that any records, information or documents that are designated by the
-------
Company in writing as confidential shall be kept confidential by such persons
unless disclosure of such records, information or documents is required by court
or administrative order or any regulatory body having jurisdiction;

                                     -21-
<PAGE>

     (p) otherwise use its best efforts to comply with all applicable rules and
regulations of the Commission, and make earnings statements satisfying the
provisions of Section 11(a) of the Securities Act generally available to its
security holders no later than 45 days after the end of any 12-month period (or
90 days, if such period is a fiscal year) (A) commencing at the end of any
fiscal quarter in which Registrable Securities are sold to underwriters in a
firm or best efforts underwritten offering, or (B) if not sold to underwriters
in such an offering, beginning with the first month of the Company's first
fiscal quarter commencing after the effective date of the Registration
Statement, which statements shall cover said 12-month periods; and

     (q) promptly prior to the filing of any document that is to be incorporated
by reference into any Registration Statement or Prospectus (after initial filing
of the Registration Statement), provide copies of such document to counsel to
the selling Holders and to the managing underwriters, if any, make the Company's
representatives available for discussion of such document and make such changes
in such document prior to the filing thereof as counsel for such selling Holders
or underwriters may reasonably request.

         The Company may require each seller of Registrable Securities as to
which any Registration is being effected to furnish to the Company such
information regarding the proposed distribution of such securities as the
Company may from time to time reasonably request in writing.

     Each Holder agrees by acquisition of such Registrable Securities that, upon
receipt of any notice from the Company of the happening of any event of the kind
described in Section 7.3(c)(F), such Holder will forthwith discontinue
disposition of Registrable Securities pursuant to the Registration Statement
until such Holder's receipt of copies of the supplemented or amended Prospectus
as contemplated by Section 7.3(k); or until it is advised in writing (the
"Advice") by the Company that the use of the Prospectus may be resumed, and has
received copies of any additional or supplemental filings that are incorporated
by reference in the Prospectus, and, if so directed by the Company, such Holder
will deliver to the Company (at the Company's expense) all copies, other than
permanent file copies then in such Holder's possession, of the Prospectus
covering such Registrable Securities. In the event the Company shall give any
such notice, the period during which the Registration Statement shall be
maintained effective pursuant to this Agreement shall be extended by the number
of days during the period from and including the date of the giving of such
notice to and including the date when each seller of Registrable Securities
covered by such Registration Statement shall have received the copies of the
supplemented or amended prospectus contemplated by Section 7.3(c)(F) or the
Advice.

                                     -22-
<PAGE>

         7.4. Restrictions on Public Sale.
              ---------------------------

         (a)  Public Sale by Stockholders and Holders. To the extent not
              ---------------------------------------
inconsistent with applicable law, (i) each Stockholder agrees not to effect any
public sale or distribution of Shares, including a sale pursuant to Rule 144 (or
any similar provision then in force) under the Securities Act, during the
180-day period, with respect to Current Stockholders, or 90-day period, with
respect to Series E Investors or other Holders with respect to the Shelf
Registration Statement (or, in either case, such shorter period as may be
consented to by the managing underwriter or underwriters, and the Company agrees
to use its best efforts to cause any such consent granted by any underwriter to
be made available to all other holders of Registrable Securities on a ratable
basis) following a Qualified IPO, and (ii) each Holder whose Registrable
Securities are included in a Registration Statement hereunder, if requested by
the managing underwriter or underwriters for such Registration, agrees not to
effect any public sale or distribution of Registrable Securities, including a
sale pursuant to Rule 144 (or any similar provision then in force) under the
Securities Act, during the 15 business days prior to, and during the 90-day
period (or such shorter period as may be consented to by such underwriter or
underwriters, which consent, if granted, will be made available to all other
holders of Registrable Securities on a ratable basis) following the effective
date of a Registration Statement pursuant to such Piggyback Registration or
Demand Registration (except as part of such Piggyback or Demand Registration).

         (b)  Public Sale by the Company. If requested by the managing
              --------------------------
underwriter or underwriters for any underwritten Registration, or by the holders
of a majority of the Registrable Securities being registered in a Demand
Registration that is not being underwritten or a Form S-3 Registration that is
not being underwritten, (i) the Company will not effect any public sale or
distribution of Common Stock (or securities convertible into or exchangeable or
exercisable for Common Stock) for its own account during the 15 business days
prior to, and during the 90-day period (or, if such Demand Registration
constitutes a Qualified IPO, 180 days) following the effective date of such
Registration, and (ii) the Company will use its best efforts to cause each other
holder of at least 150,000 shares of Common Stock (as adjusted for stock splits,
stock dividends, reverse splits and the like) (or securities convertible into or
exchangeable for, or options to purchase, Common Stock) purchased from the
Company at any time after the date of this Agreement (other than in a registered
public offering) to agree not to effect any public sale or distribution of any
such Securities during the period described in Section 7.4(a)(i) above (except
as part of such Registration, if otherwise permitted); provided, however, that
                                                       --------  -------
in the case of any employee or consultant who presently holds Common Stock
(and/or securities convertible into, or exchangeable for, or options to
purchase, Common Stock), the Company shall not be obligated to request that such
person enter into an agreement contemplated by this Section 7.4(b)(ii) unless
and until such person, after the date hereof, acquires from the Company
additional Common Stock (or securities convertible into, or exchangeable for, or
options to purchase, Common Stock) that result in such person becoming, or
continuing to be, the holder of at least 150,000 shares of Common Stock (as
adjusted for stock splits, stock dividends, reverse splits and the like)(or
securities convertible into, or exchangeable for, or options to purchase, Common
Stock), in which case it shall be a condition of the Company's issuance of such
additional Common Stock, securities or options of the Company that such person
enter into such an agreement.

                                     -23-
<PAGE>

         (c)  Other Registrations. If the Company has previously filed a
              -------------------
Registration Statement with respect to Registrable Securities, and if such
previous Registration has not been withdrawn or abandoned, the Company will not
file or cause to be effected any other registration of any of its Common Stock
(or securities convertible into or exchangeable for, or options to purchase,
Common Stock) under the Securities Act (except on Form S-4, Form S-8 or any
similar successor forms), whether on its own behalf or at the request of any
holder or holders of Common Stock (or securities convertible into or
exchangeable or exercisable for Common Stock), until a period of at least six
months has elapsed from the effective date of such previous Registration;
provided, however, that if the holders of 50% or more of the aggregate number of
--------  -------
Registrable Securities included in such previous Registration shall agree in
writing, such period may be shortened by the Company but not to a period shorter
than three months.

         7.5. Registration Expenses.
              ---------------------

         (a)  Generally. All expenses incident to the Company's performance of
              ---------
or compliance with this Article VII will be borne by the Company, including,
without limitation, all registration and filing fees, the fees and expenses of
the counsel and accountants for the Company (including the expenses of any "cold
comfort" letters and special audits required by or incident to the performance
of such persons), all other costs and expenses of the Company incident to the
preparation, printing and filing under the Securities Act of the Registration
Statement (and all amendments and supplements thereto) and furnishing copies
thereof and of the Prospectus included therein, the costs and expenses incurred
by the Company in connection with the qualification of the Registrable
Securities under the state securities or "Blue Sky," laws of various
jurisdictions, the costs and expenses associated with filings required to be
made with the NASD (including, if applicable, the fees and expenses of any
"qualified independent underwriter" and its counsel as may be required by the
rules and regulations of the NASD), the costs and expenses of listing the
Registrable Securities for trading on a national securities exchange or
authorizing them for trading on the NASDAQ National Market System and all other
costs and expenses incurred by the Company in connection with any Registration
hereunder; provided, however, that the Company shall not bear the costs and
           --------  -------
expenses of any selling Holder for underwriters' commissions, brokerage fees or
transfer taxes, or, except as otherwise provided in Section 7.5(b) below, the
fees and expenses of any counsel, accountants or other representative retained
by any selling Holder.

         (b)  Counsel and Out-Of-Pocket Fees. Notwithstanding Section 7.5(a)
              ------------------------------
above, in connection with each Registration hereunder, the Company will
reimburse the selling Holders for the reasonable fees and disbursements of not
more than one counsel, which counsel shall be chosen by the holders of a
majority of the Registrable Securities covered by the Registration.

                                     -24-
<PAGE>

         7.6. Indemnification.
              ---------------

         (a)  Indemnification by the Company. The Company agrees to indemnify,
              ------------------------------
to the full extent permitted by law, each Holder, its officers, directors and
agents and each person who controls such Holder within the meaning of the
Securities Act and the Exchange Act (each, an "Indemnified Holder"), against all
losses, claims, damages, liabilities and expenses caused by any untrue or
alleged untrue statement of a material fact contained in any Registration
Statement, Prospectus or preliminary Prospectus, or any omission or alleged
omission to state therein a material fact necessary to make the statements
therein (in the case of a Prospectus or any preliminary Prospectus, in light of
the circumstances under which they were made) not misleading, except to the
extent that such untrue statement or omission is caused by any information with
respect to such Indemnified Holder furnished in writing to the Company by such
Indemnified Holder or its representative expressly for use therein. The Company
will also indemnify underwriters, selling brokers, dealer managers and similar
securities industry professionals participating in the distribution, their
officers and directors and each person who controls such persons (within the
meaning of the Securities Act) to the same extent as provided above with respect
to Indemnified Holders; provided, however, that if pursuant to an underwritten
                        --------  -------
public offering of Registrable Securities, the Company and any underwriters
enter into an underwriting or purchase agreement relating to such offering that
contains provisions relating to indemnification and contribution between the
Company and such underwriters, such provisions shall be deemed to govern
indemnification and contribution as between the Company and such underwriters.

         (b)  Indemnification by Holders of Registrable Securities. In
              ----------------------------------------------------
connection with any Registration, each Holder participating therein will furnish
to the Company in writing such information with respect to the Holder as the
Company reasonably requests for use in connection with any Registration
Statement, Prospectus or preliminary Prospectus, and agrees to indemnify, to the
full extent permitted by law, the Company, the directors and officers of the
Company signing the Registration Statement and each person who controls the
Company (within the meaning of the Securities Act and the Exchange Act) against
any losses, claims, damages, liabilities and expenses resulting from any untrue
statement of a material fact or any omission to state a material fact required
to be stated therein or necessary to make the statements in the Registration
Statement, Prospectus or preliminary Prospectus (in the case of the Prospectus
or any preliminary Prospectus, in light of the circumstances under which they
were made) not misleading, to the extent, and only to the extent, that such
untrue statement or omission is caused by any information with respect to the
Holder so furnished in writing by the Holder or its representative specifically
for inclusion therein. In no event shall the liability of any selling Holder
hereunder be greater in amount than the dollar amount of the net proceeds (after
deducting commissions and expenses) received by such Holder upon the sale of the
Registrable Securities giving rise to such indemnification obligation. The
Company shall be entitled to receive indemnities from underwriters, selling
brokers, dealer managers and similar securities industry professionals
participating in the distribution, to the same extent as provided above with
respect to information with respect to such persons or entities so furnished in
writing by such persons or entities or their representatives specifically for
inclusion in any Registration Statement, Prospectus or preliminary Prospectus.

                                     -25-
<PAGE>

         (c)  Conduct of Indemnification Proceedings. Any person or entity
              --------------------------------------
entitled to indemnification hereunder will (i) give prompt written notice to the
indemnifying party after the receipt by the indemnified party of a written
notice of the commencement of any action, suit, proceeding or investigation or
threat thereof made in writing for which such indemnified party will claim
indemnification or contribution pursuant to this Agreement; provided, however,
                                                            --------  -------
that the failure of any indemnified party to give notice as provided herein
shall not relieve the indemnifying party of its obligations under the preceding
Section 7.6(a) or 7.6(b), as applicable, except to the extent that the
indemnifying party is actually prejudiced by such failure to give notice and
(ii) unless in such indemnified party's reasonable judgment a conflict of
interest may exist between such indemnified and indemnifying parties with
respect to such claim, permit such indemnifying party to assume the defense of
such claim with counsel reasonably satisfactory to the indemnified party.
Whether or not such defense is assumed by the indemnifying party, the
indemnifying party will not be subject to any liability for any settlement made
without its consent (but such consent will not be unreasonably withheld). No
indemnifying party will be required to consent to the entry of any judgment or
to enter into any settlement that does not include as an unconditional term
thereof the giving by the claimant or plaintiff of a release from all liability
in respect of such claim or litigation. An indemnifying party who is not
entitled to, or elects not to, assume the defense of a claim will not be
obligated to pay the fees and expenses of more than one counsel in any one
jurisdiction for all parties indemnified by such indemnifying party with respect
to such claim, unless in the reasonable judgment of any indemnified party a
conflict of interest may exist between such indemnified party and any other of
such indemnified parties with respect to such claim, in which event the
indemnifying party shall be obligated to pay the fees and expenses of such
additional counsel or counsels.

         (d)  Contribution. If for any reason the indemnification provided for
              ------------
in the preceding Section 7.6(a) or 7.6(b), as applicable, is unavailable to an
indemnified party as contemplated by such Section, then the indemnifying party,
in lieu of indemnification, shall contribute to the amount paid or payable by
the indemnified party as a result of such loss, claim, damage, liability or
expense in such proportion as is appropriate to reflect not only the relative
benefits received by the indemnified party and the indemnifying party, but also
the relative fault of the indemnified party and the indemnifying party, as well
as any other relevant equitable considerations; provided, however, that no
                                                --------  -------
selling Holder shall be required to contribute in an amount greater than the
difference between the net proceeds received by the Holder with respect to the
sale of Registrable Securities and all amounts already contributed by the Holder
with respect to such claims, including amounts paid for any legal or other fees
or expenses incurred by the Holder.

         7.7. Rule 144. The Company agrees that at all times after it has filed
              --------
a registration statement pursuant to the requirements of the Securities Act
relating to any class of equity securities of the Company, it will file in a
timely manner all reports required to be filed by it pursuant to the Securities
Act and the Exchange Act and will take such further action as any Holder may
reasonably request in order that such Holder may effect sales of Registrable
Securities pursuant to Rule 144. At any reasonable time and upon request of a
Stockholder, the Company will furnish such Stockholder and others with such
information as may be necessary to enable the Stockholder to effect sales of
Common Stock pursuant to Rule 144 under the Securities Act and will deliver to
such Stockholder a written statement as to whether it has

                                     -26-
<PAGE>

complied with such requirements. Notwithstanding the foregoing, the Company may
deregister any class of its equity securities under Section 12 of the Exchange
Act or suspend its duty to file reports with respect to any class of its
securities pursuant to Section 15(d) of the Exchange Act if it is then permitted
to do so pursuant to the Exchange Act and the rules and regulations thereunder.

         7.8. Participation in Underwritten Registrations. No Holder may
              -------------------------------------------
participate in any underwritten registration hereunder unless such Holder (i)
agrees to sell its Registrable Securities on the basis provided in any
underwriting arrangements approved by the Company, and (ii) accurately completes
in a timely manner and executes all questionnaires, powers of attorney,
underwriting agreements and other documents customarily required under the terms
of such underwriting arrangements.

                                  ARTICLE VIII.

                                  MISCELLANEOUS
                                  -------------

         8.1. Legend. In addition to any legends required by federal or state
              ------
securities laws, the certificates representing the Shares shall bear the
following legend:

         "The securities represented by this certificate are subject to certain
         restrictions on transfer, voting provisions, and other provisions set
         forth in an Amended and Restated Stockholders Agreement, as amended
         from time to time. A copy of such Agreement may be obtained from the
         Company upon request."

Each of the parties hereto agrees that it will not transfer any Shares without
complying with each of the restrictions set forth herein and agrees that in
connection with any such transfer it will, if requested by the Company, deliver
at its expense to the Company an opinion of counsel (including in-house or
special counsel), in form and substance reasonably satisfactory to the Company
and counsel for the Company, that such transfer is not in violation of the
securities laws of the United States of America.

         8.2. Transferees; Additional Restriction on Transfer. Each transferee
              -----------------------------------------------
of Shares from a Stockholder or a subsequent transferee (including the
transferee in a transfer from one Stockholder to another Stockholder) shall take
such Shares subject to the same restrictions as existed in the hands of the
transferor, including, without limitation, the restrictions imposed on
Stockholders under Article II hereof, the restrictions imposed on a Proposed
Seller under Article III hereof, the restrictions imposed on Stockholders other
than Proposed Transferors under Article IV hereof, the restrictions on voting
Shares under Article VI hereof and restrictions on the sale of Shares under
Section 7.4(a) hereof. No transferee of Shares from a Stockholder or a
subsequent transferee, other than a transferee receiving Shares in a Permitted
Transfer under clause (i) or (ii) of Section 1.7 or a transferee (together with
its Related Parties) of shares representing at least 1,500,000 shares of
Fully-Diluted Common Stock (subject to adjustment for stock splits, reverse
stock splits, stock dividends, combinations and the like), shall be entitled to
the benefits provided to Stockholders hereunder, including, without limitation,
the rights of a

                                     -27-
<PAGE>

Remaining Stockholder under Article III hereof, the right of Proposed
Transferors under Article IV hereof, and registration rights under Article VII
hereof.

         8.3. Specific Performance, Etc. The Company and each Stockholder, in
              -------------------------
addition to being entitled to exercise all rights provided herein, in the
Company's Certificate of Incorporation or granted by law, including recovery of
damages, will be entitled to specific performance of its rights under this
Agreement. Each party agrees that monetary damages would not be adequate
compensation for any loss incurred by reason of a breach by it of the provisions
of this Agreement and hereby agrees to waive the defense in any action for
specific performance that a remedy at law would be adequate.

         8.4. Notices. All notices, requests, demands and other communications
              -------
which are required or may be given under this Agreement shall be in writing and
shall be deemed to have been duly received when received if personally
delivered; when transmitted if transmitted by telecopy, electronic or digital
transmission method; the day after it is sent, if sent for next day delivery to
a domestic address by recognized overnight delivery service (e.g., FedEx); and
upon receipt, if sent by certified or registered mail, return receipt requested.
In each case notice shall be sent, if to the Company, to Tellium, Inc., 2
Crescent Place, P.O. Box 901, Oceanport, NJ 07757, Attn: Chief Executive Officer
(telecopier: 732-923-9805), or if to the other parties at their addresses listed
on Annex I attached hereto, or to such other place and with such other copies as
any party may designate as to itself or himself by written notice to the others.

         8.5. Entire Agreement; Amendments and Waivers. This Agreement
              ----------------------------------------
constitutes the entire agreement among the parties pertaining to the subject
matter hereof and supersedes all prior agreements, understandings, negotiations
and discussions, whether oral or written, of the parties hereto, including, with
limitation, the Existing Stockholders Agreement, which is hereby terminated
effective as of the date hereof. The provisions of this Agreement, including the
provisions of this sentence, may not be amended, modified or supplemented, and
waivers of or consents to departures from the provisions hereof may not be given
unless approved in writing by the Company and the holders of sixty-six and two
thirds percent (66-2/3%) of the Shares then outstanding (provided that if any
amendment adversely affects the rights of a particular Stockholder when compared
with its effect on the other Stockholders, the consent of such Stockholder shall
be required for such amendment); provided, however, that this Agreement shall be
                                 --------  -------
automatically amended to include any Permitted Transferee of a Stockholder. No
action taken pursuant to this Agreement, including, without limitation, any
investigation by or on behalf of any party, shall be deemed to constitute a
waiver by the party taking such action. The waiver by any party hereto of a
breach of any provision of this Agreement shall not operate or be construed as
waiver of any preceding or succeeding breach and no failure by any party to
exercise any right or privilege hereunder shall be deemed a waiver of such
party's rights or privileges hereunder or shall be deemed a waiver of such
party's rights to exercise the same at any subsequent time or times hereunder.

         8.6. Termination. If not terminated sooner pursuant to the terms
              -----------
hereof, Articles III, IV and V of this Agreement (regarding rights of first
offer and tag-along rights, drag-along rights and co-investment rights,
respectively) shall terminate and cease to be of any further force or effect
upon the Company's merger with and into another corporation or other entity
where, upon

                                     -28-
<PAGE>

consummation of the merger, the holders of the Company's voting stock
immediately prior to the merger will hold less than 50% of the voting stock of
the surviving corporation immediately after the merger. If not terminated sooner
pursuant to the terms hereof, Article VII of this Agreement (regarding
registration rights) shall terminate and cease to be of any further force or
effect upon the Company's merger with and into another corporation where, in
connection with the merger, the Shares are exchanged exclusively for cash and/or
shares of capital stock or other securities that are publicly traded on a
national securities exchange or authorized for trading on the NASDAQ National
Market System.

         8.7. Recapitalizations, Exchange, Etc. Affecting the Company's Stock.
              --------------------------------  -----------------------------
The provisions of this Agreement shall apply, to the full extent set forth
herein with respect to the Shares, to any and all shares of capital stock of the
Company that may be issued in respect of, in exchange for, or in substitution of
the Shares and shall be appropriately adjusted for any stock dividends, splits,
reverse splits, combinations, recapitalizations and the like occurring after the
date hereof.

         8.8. Waiver and Consent. With respect to the transactions contemplated
              ------------------
by the Series E Purchase Agreement, each of the Current Stockholders hereby
waives all preemptive rights and any similar rights granted to such Current
Stockholders by the Company pursuant to this Agreement, any predecessor
agreement, any organizational document or otherwise and consents to such
transactions.

         8.9. Multiple Counterparts. This Agreement may be executed in one or
              ---------------------
more counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

         8.10. Additional Signatories. Each purchaser of Preferred Stock of the
               ----------------------
Company under the Series E Purchase Agreement shall, upon execution and delivery
of a counterpart to this Agreement, be entitled to all the rights of, and be
subject to all of the obligations binding upon, a Stockholder hereunder, and all
references to "Stockholder" herein shall be deemed to include any such party
from the date of execution and delivery of a counterpart to this Agreement.

         8.11. Headings. The headings of the Articles and Sections herein are
               --------
inserted for convenience of reference only and are not intended to be part of or
to affect the meaning or interpretation of this Agreement.

         8.12. Governing Law. This Agreement shall be governed by and construed
               -------------
in accordance with the internal laws of the State of Delaware, without regard to
principles of conflict of laws.

         8.13. Construction. Differences in language as between similar
               ------------
provisions covering similar matters may reflect differences in style rather than
a different substantive intent and should be construed accordingly.

         8.14. Expenses. Except as otherwise specified in this Agreement or
               --------
Section 10 of the Stock Purchase Agreement, each party hereto shall pay its own
legal, accounting, out-of-pocket

                                     -29-
<PAGE>

and other expenses incident to this Agreement and to any action taken by such
party in preparation for carrying this Agreement into effect.

         8.15. Invalidity. In the event that any one or more of the provisions
               ----------
contained in this Agreement or in any other document or instrument referred to
herein, shall, for any reason, be held to be invalid, illegal or unenforceable
in any respect, then to the maximum extent permitted by law, such invalidity,
illegality or unenforceability shall not affect any other provision of this
Agreement or any other such document or instrument

         8.16. Cumulative Remedies. All rights and remedies of either party
               -------------------
hereto are cumulative of each other and of every other right or remedy such
party may otherwise have at law or in equity, and the exercise of one or more
rights or remedies shall not prejudice or impair the concurrent or subsequent
exercise of other rights or remedies.

                 (BALANCE OF THIS PAGE INTENTIONALLY LEFT BLANK)

         IN WITNESS WHEREOF, the parties have executed this Amended and Restated
Stockholders Agreement as of the day and year first written above.

TELLIUM, INC.

By: /s/
   -----------------------------
Name:
Title:

                                     -30-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

TELCORDIA VENTURE CAPITAL CORPORATION

By: /s/
   -------------------------------
Name:
Title:

                                     -31-
<PAGE>

                         Counterpart Signature Page to
     Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

CISCO SYSTEMS, INC.

By:
   -------------------------------
Name:
Title:

                                     -32-
<PAGE>

                         Counterpart Signature Page to
     Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

ACCEL V L.P.
By:  Accel V Associates L.L.C.
Its General Partner

By: /s/
   -------------------------------
           Managing Member

ACCEL INTERNET/STRATEGIC TECHNOLOGY FUND, L.P.

By: Accel Internet/Strategic Technology Fund
    Associates L.L.C.
    Its General Partner

By: /s/
   -------------------------------
           Managing Member

ACCEL KEIRETSU V L.P.
By:  Accel Keiretsu V. Associates L.L.C.
     Its General Partner

By: /s/
   -------------------------------
           Managing Member

ACCEL INVESTORS `96 L.P.

By: /s/
   -------------------------------
           General Partner

                                     -33-
<PAGE>

                         Counterpart Signature Page to
     Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

ELLMORE C. PATTERSON PARTNERS

By: /s/
   -------------------------------
           General Partner

                                     -34-
<PAGE>

                         Counterpart Signature Page to
     Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

BLUE ROCK CAPITAL, L.P.

By: Blue Rock Partners, L.P., its General Partner
By: Blue Rock, Inc., its General Partner

By: /s/
   -------------------------------
Name:
Title:

                                     -35-
<PAGE>

                         Counterpart Signature Page to
     Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

LUCENT TECHNOLOGIES INC.

By:
   -------------------------------
Name:
Title:

                                     -36-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

OAK INVESTMENT PARTNERS VII LIMITED PARTNERSHIP

By:      Oak Associates VII, LLC,
         Its General Partner

By: /s/
   -------------------------------
Name:    Edward F. Glassmeyer
Title:   Managing Member

OAK VII AFFILIATES FUND,
LIMITED PARTNERSHIP

By:      Oak VII Affiliates, LLC
         Its General Partner

By: /s/
   -------------------------------
Name:    Edward F. Glassmeyer
Title:   Managing Member

                                     -37-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

PEQUOT PRIVATE EQUITY FUND II, L.P.

By:      Pequot Capital Management, Inc.,
         Investment Manager

By: /s/
   ------------------------------
Name: David J. Malat
Title: Chief Financial Officer

                                     -38-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

WORLDVIEW TECHNOLOGY PARTNERS I, L.P.
By:      Worldview Capital I, L.P.,
         its General Partner

By:      Worldview Equity I, L.L.C.,
         its General Partner

By:
   ------------------------------
         Member

WORLDVIEW TECHNOLOGY INTERNATIONAL I, L.P.
By:      Worldview Capital I, L.P., its General Partner
By:      Worldview Equity I, L.L.C., its General Partner

By:
   ------------------------------
         Member

WORLDVIEW STRATEGIC PARTNERS I, L.P.
By:  Worldview Capital I, L.P., its General Partner
By:  Worldview Equity I, L.LC., its General Partner

By:
   ------------------------------
         Member

                                     -39-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

THOMAS WEISEL CAPITAL PARTNERS, L.P.
By: Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:    William Bunting
Title:   Authorized Signatory

TWP CEO FOUNDERS' CIRCLE (AI), L.P.
By: Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:    William Bunting
Title:   Authorized Signatory

TWP CEO FOUNDERS' CIRCLE (QP), L.P.
By: Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:    William Bunting
Title:   Authorized Signatory

THOMAS WEISEL PARTNERS GROUP LLC

By: /s/
   ------------------------------
Name:    William Bunting
Title:   Authorized Signatory

                                     -40-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

THOMAS WEISEL CAPITAL PARTNERS
EMPLOYEE FUND, L.P.

By: /s/
   ------------------------------
Name:      William Bunting
Title:     Authorized Signatory

TWP 2000 CO-INVESTMENT FUND, L.P.
By: Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:      Marianne Winkler
Title:     Authorized Signatory

TWP TELLIUM INVESTORS

By: /s/
   ------------------------------
Name:      David Baylor
Title:     Authorized Signatory

THOMAS WEISEL CAPITAL PARTNERS (DUTCH), L.P.
By: Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:      Marianne Winkler
Title:     Authorized Signatory

THOMAS WEISEL CAPITAL PARTNERS (DUTCH II), L.P.
By: Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:      Marianne Winkler
Title:     Authorized Signatory

                                     -41-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

RB INVESTMENT PARTNERS II, LLC

By: /s/
   ------------------------------
Name:
Title:

/s/
---------------------------------
JOHN WALLACE

                                     -42-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

SJJ LLC

By: /s/
   ------------------------------
Name:
Title:

                                     -43-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

COMDISCO, INC.

By:
   ------------------------------
Name:
Title:

                                     -44-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

                                     -45-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

ACAPPELLA VENTURES, LLC

By: /s/
   ------------------------------
Name:
Title:

                                     -46-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

AIM EQUITY FUNDS, on behalf
of its portfolio, AIM EMERGING GROWTH FUND

By: /s/
   -------------------------------
Name:
Title:

AIM GROWTH SERIES, on behalf of
its portfolio, AIM SMALL CAP GROWTH FUND

By: /s/
   ------------------------------
Name:
Title:

AIM SPECIAL OPPORTUNITIES, on behalf
of its portfolio, AIM SMALL CAP OPPORTUNITIES FUND

By: /s/
   ------------------------------
Name:
Title:

AIM SPECIAL OPPORTUNITIES, on behalf
of its portfolio, AIM MID CAP OPPORTUNITIES FUND

By: /s/
   ------------------------------
Name:
Title:

AIM SPECIAL OPPORTUNITIES, on behalf
of its portfolio, AIM LARGE CAP OPPORTUNITIES FUND

By: /s/
   ------------------------------
Name:
Title

                                     -47-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

ALLIANCE TECHNOLOGY PARTNERS, L.P.
By:  Alliance Capital Global Derivatives Corporation,
         General Partner

By: /s/
   ------------------------------
            Secretary

ACM TECHNOLOGY HEDGE FUND
By:  Alliance Capital Management L.P.,
         its Investment Adviser

By: /s/
   ------------------------------
            Authorized Officer

ACM STRATEGIC INVESTMENTS - TECHNOLOGY PORTFOLIO
By:  Alliance Capital Management L.P.,
         its Investment Adviser

By: /s/
   ------------------------------
            Authorized Person

                                      -48-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

WORLD TECHNOLGOIES PORTFOLIO, a series of WORLD TRUST

By: /s/
   ------------------------------
Name:  Frederick C. Quirsfeld
Title: Vice President, World Trust

EQUITY PORTFOLIO, a series of IDS LIFE SERIES FUND, INC.

By: /s/
   ------------------------------
Name:  Frederick C. Quirsfeld
Title: Vice President, IDS Life Series Fund, Inc.

AXP STRATEGY AGGRESSIVE FUND, a series of AXP STRATEGY SERIES, INC.

By: /s/
   ------------------------------
Name:  Frederick C. Quirsfeld
Title: Vice President, AXP Strategy Series, Inc.

AXP VARIABLE PORTFOLIO - STRATEGY AGGRESSIIVE FUND, a series of AXP
VARIABLE PORTFOLIO INVESTMENT SERIES, INC.

By: /s/
   ------------------------------
Name:  Frederick C. Quirsfeld
Title: Vice President, AXP Variable Portfolio Investment Series, Inc.

                                     -49-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

AMERINDO TECHNOLOGY GROWTH FUND II, INC.

By: /s/
   ------------------------------
Name:    Gary Tanaka
Title:   Director

AMERINDO INTERNET FUND PLC

By: /s/
   ------------------------------
Name:    Gary Tanaka
Title:   Manager

eMERGING TECHNOLOGY PORTFOLIO

By: /s/
   ------------------------------
Name:    Gary Tanaka
Title:   Attorney-in-fact

                                     -50-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

BROADBAND HOLDINGS (BVI) LIMITED

By: /s/
   ------------------------------
Name:    Edwin J. Wang
Title:   Authorized Signatory

                                     -51-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

CORNING INCORPORATED

By: /s/
   ------------------------------
Name:
Title:

                                     -52-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

FIDELITY SELECT PORTFOLIOS:
COMPUTER PORTFOLIO

By: /s/
   ------------------------------
Name:
Title:

FIDELITY ADVISOR SERIES VII:
FIDELITY ADVISOR TECHNOLOGY FUND

By: /s/
   ------------------------------
Name:
Title:

FIDELITY SMALL CAP AMERICA FUND

By: /s/
   ------------------------------
Name:
Title:

FIDELITY FOCUS TECHNOLOGY FUND

By: /s/
   ------------------------------
Name:
Title:

FIDELITY MT. VERNON STREET TRUST:
FIDELITY AGGRESSIVE GROWTH FUND

By: /s/
   ------------------------------
Name:
Title:

                                     -53-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

FIDELITY HASTINGS STREET TRUST:
FIDELITY FUND

By: /s/
   ------------------------------
Name:
Title:

FIDELITY ADVISOR SERIES I:
FIDELITY ADVISOR VALUE STRATEGIES FUND

By: /s/
   ------------------------------
Name:
Title:

FIDELITY SELECT PORTFOLIOS:
TECHNOLOGY PORTFOLIO

By: /s/
   ------------------------------
Name:
Title:

PENSION RESERVES INVESTMENT MANAGEMENT BOARD
BY:  FIDELITY MANAGEMENT TRUST COMPANY,
AS INVESTMENT MANAGER, UNDER POWER OF ATTORNEY

By: /s/
   ------------------------------
Name:
Title:

                                     -54-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

GOLDMAN, SACHS & CO.

By: /s/
   ------------------------------
Name:
Title:

                                     -55-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

INVESCO TECHNOLOGY FUND

By: /s/
   ------------------------------
Name:
Title:

INVESCO TELECOMMUNICATIONS FUND

By: /s/
   ------------------------------
Name:
Title:

                                     -56-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

                                     -57-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

MUNDER NETNET FUND, a series of The Munder Funds, Inc.

By: /s/
   -----------------------------------
Name:  Stephen J. Shenkenberg
Title:  Vice President and Secretary

                                     -58-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

OPPENHEIMER VARIABLE ACCOUNT FUNDS
FOR THE ACCOUNT OF OPPENHEIMER
AGGRESSIVE GROWTH FUND

By: /s/
   ------------------------------
Name:
Title:

OPPENHEIMER MIDCAP FUND

By: /s/
   ------------------------------
Name:
Title:

OPPENHEIMER EMERGING TECHNOLOGIES FUND

By: /s/
   ------------------------------
Name:
Title:

OPPENHEIMER ENTERPRISE FUND

By: /s/
   ------------------------------
Name:
Title:

                                     -59-
<PAGE>

                         Counterpart Signature Page to
     Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

PALANTIR PARTNERS LP

By: /s/
   ------------------------------
Name:
Title:

PALANTIR INVESTMENTS LDC

By: /s/
   ------------------------------
Name:
Title:

                                     -60-
<PAGE>

                         Counterpart Signature Page to
     Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

PEQUOT TECHNOLOGY PERENNIAL FUND, L.P.

By: Pequot Capital Management, Inc.
    its Investment Manager

By: /s/
   ------------------------------------
Name:   Kevin E. O'Brien
Title:  General Counsel

PEQUOT ENDOWMENT FUND, L.P.

By:     Pequot Capital Management, Inc.
        its Investment Manager

By: /s/
   ------------------------------------
Name:   Kevin E. O'Brien
Title:  General Counsel

                                     -61-
<PAGE>

                         Counterpart Signature Page to
     Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

ROTHCHILD TECHNOLOGY PARTNERS, LP

By: /s/
   ------------------------------
Name:    Mark J. McCall
Title:   Managing Director

                                     -62-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

THE PAISLEY FUND, L.P.

By: /s/
   ------------------------------
Name:
Title:

THE PAISLEY PACIFIC FUND, L.P.

By: /s/
   ------------------------------
Name:
Title:

                                     -63-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

TAILWIND INVESTMENT PARTNERS (QP), L.P.
By:  Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:
Title:

TAILWIND INVESTMENT PARTNERS (AI), L.P.
By:  Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:
Title:

TAILWIND INVESTMENT PARTNERS INTERNATIONAL, L.P.
By:  Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:
Title:

TAILWIND INVESTMENT PARTNERS EMPLOYEE FUND, L.P.
By:  Thomas Weisel Capital Partners LLC, its general partner

By: /s/
   ------------------------------
Name:
Title:

THOMAS WEISEL PARTNERS

By: /s/
   ------------------------------
Name:
Title:

                                     -64-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
           by and among Tellium, Inc. and the parties named therein

VAN WAGONER FUNDS

By: /s/
   ------------------------------
Name:
Title:

VAN WAGONER CAPITAL PARTNERS, L.P.

By: /s/
   ------------------------------
Name:
Title:

VAN WAGONER CROSSOVER FUND, LP

By: /s/
   ------------------------------
Name:
Title:

                                     -65-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

QUISSET PARTNERS, L.P.
by Wellington Management Company, LLP,
Its Investment Advisor

By: /s/
   ------------------------------
Name:    Peter L. Curry
Title:   Vice President

QUISSET INVESTORS (BERMUDA) L.P.
by Wellington Management Company, LLP,
Its Investment Advisor

By: /s/
   ------------------------------
Name:    Peter L. Curry
Title:   Vice President

RAYTHEON MASTER PENSION TRUST,
by Wellington Management Company, LLP,
Its Investment Advisor

By: /s/
   ------------------------------
Name:    Peter L. Curry
Title:   Vice President

                                     -66-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

WIT SOUNDVIEW PHOTONICS FUND 2000, LLC

By: /s/
   ------------------------------
Name:
Title:

WIT SOUNDVIEW FUND 2000, LLC

By: /s/
   ------------------------------
Name:
Title:

                                     -67-
<PAGE>

                          Counterpart Signature Page to
      Amended and Restated Stockholders' Agreement dated September __, 2000
             by and among Tellium, Inc. and the parties named therein

SUAIMHNEAS LLC

By: /s/
   ------------------------------
Name: Michael M. Connors
Title:   Manager

                                     -68-<PAGE>

                                                                     Exhibit 4.3

                     SUPPLEMENTAL STOCKHOLDERS' AGREEMENT

          This Supplemental Stockholders' Agreement (this "Agreement"), dated as
of October 10, 2000, by and between Tellium, Inc., a Delaware corporation (the
"Company"), and the stockholders of Astarte Fiber Networks, Inc., a Colorado
corporation ("Astarte"), which are listed on Exhibit A hereto (each a
                                             ---------
"Stockholder," collectively, the "Stockholders").

          WHEREAS, the Company has entered into an Agreement and Plan of Merger
dated as of August 29, 2000 (the "Merger Agreement") by and among the Company,
Astarte Acquisition Corporation, a Colorado corporation, and Astarte; and

          WHEREAS, as a condition precedent to the consummation of the
transactions contemplated by the Merger Agreement, the Company and the
Stockholders are required to enter into this Agreement.

          NOW, THEREFORE, in consideration of these premises and the mutual
agreements, provisions and covenants contained in this Agreement, the parties
hereby agree as follows:

       1. Certain Definitions
          -------------------

          Unless defined herein, capitalized terms not defined herein shall have
the meanings assigned to them in the Merger Agreement.  As used in this
Agreement, the following terms shall have the meanings set forth below:

          "Commission" means the Securities and Exchange Commission or any other
           ----------
federal agency at the time administering the Securities Act.

          "Common Stock" means the Common Stock, $0.001 par value per share, of
           ------------
the Company.

          "Company Stockholder" means a holder of shares of Common Stock of the
           -------------------
Company other than the Stockholders with respect to Merger Shares.

          "Exchange Act" means the Securities Exchange Act of 1934, as amended,
           ------------
and the rules and regulations of the Commission promulgated thereunder, all as
the same shall be in effect from time to time.

          "Merger Shares" means any shares of Common Stock held by operation of
           -------------
the Merger by any Stockholder, including any shares of Common Stock to be issued
in exchange for shares of Astarte capital stock or options to purchase shares of
Astarte capital stock (including the shares of Common Stock placed in escrow
pursuant to the Merger Agreement).

          "Person" means any individual, corporation, limited liability company,
           ------
limited or general partnership, joint venture, association, joint-stock company,
trust, unincorporated organization or government or any agency or political
subdivisions thereof.
<PAGE>

          "Registrable Shares" means the Merger Shares; provided, however, that
           ------------------                           --------  -------
Merger Shares that are Registrable Shares shall cease to be Registrable Shares
(x) upon their sale pursuant to a registration statement or Rule 144 under the
Securities Act, (y) when such shares are eligible for sale pursuant to Rule 144
under the Securities Act or (z) upon their sale in any manner to a person or
entity which is not entitled to the rights provided by this Agreement.

          "Rule 144" means Rule 144 promulgated under the Securities Act or any
           --------
successor rule thereto or any complementary rule thereto.

          "Securities Act" means the Securities Act of 1933, as amended, and the
           --------------
rules and regulations of the Commission thereunder, all as the same shall be in
effect from time to time.

          "Stockholder" means each Person which holds Merger Shares and is
           -----------
listed on Exhibit A hereto.
          ---------

       2. Stockholder's Representations and Agreements
          --------------------------------------------

          2.1  Investment Representations.  Each Stockholder hereby represents
               --------------------------
and warrants that it is acquiring the Merger Shares for investment for its own
account and not with a view to, or for resale in connection with, the
distribution or other disposition thereof.  Each Stockholder further represents
and warrants that (a) it has been given the opportunity to obtain any
information or documents (and to ask questions and receive answers about such
documents) relating to the Company and the business and prospects of the Company
that it deems necessary to evaluate the merits and risks related to its
investment in the Merger Shares, (b) its financial condition is such that it can
afford to bear the economic risk of holding the Merger Shares for an indefinite
period of time and it has adequate means for providing for its current needs and
personal contingencies, (c) it can afford to suffer a complete loss of its
investment in the Merger Shares, (d) all information that it has provided to the
Company concerning itself and its financial position is correct and complete as
of the date of this Agreement, (e) it understands and has taken cognizance of
all risk factors to the acquisition of the Merger Shares, and (f) its knowledge
and experience in financial and business matters are such that it is capable of
evaluating the merits and risks of its acquisition of the Merger Shares as
contemplated by this Agreement.

          2.2  Merger Shares Subject to Restrictions.  The Stockholders
               -------------------------------------
acknowledge that they have been advised that (a) the Merger Shares have not been
registered under the Securities Act, (b) other than any transfer, sale,
assignment, pledge, hypothecation or other disposal of Merger Shares (each, a
"Transfer") permitted pursuant to Section 3 hereof, the Merger Shares shall be
held indefinitely, and the Stockholder is required to bear the economic risk of
its investment in the Merger Shares, (c) when and if the Merger Shares can be
transferred pursuant to this Agreement, Rule 144 promulgated under the
Securities Act may not be available with respect to the sale of any securities
of the Company, and the Company has made no covenant to make such Rule
available, (d) when and if the Merger Shares may be disposed of pursuant to this
Agreement without registration in reliance on Rule 144, such disposition can be
made only in limited amounts in accordance with the terms and conditions of such
Rule, (e) if the Rule 144 exception is not available, public sale without
registration will require compliance with some other exemption under the
Securities Act, (f) a restrictive legend in the form set forth

                                      -2-
<PAGE>

in Section 6.1 below shall be placed on the certificates or instruments
representing the Merger Shares, and (g) a notation shall be made in the
appropriate records of the Company indicating that the Merger Shares are subject
to restrictions on transfer and, if the Company should at some time in the
future engage the services of a stock transfer agent, an appropriate stop
transfer restriction will be issued to such transfer agent with respect to the
Merger Shares.

          2.3  Rule 144 Sales.  Subject to the restrictions on transfer set
               --------------
forth in Section 3 hereof, if any of the Merger Shares are to be disposed of in
accordance with Rule 144 under the Act or otherwise and such transfer is
otherwise permitted, the Stockholders shall promptly notify the Company of such
intended disposition and shall deliver to the Company at or prior to the time of
such disposition such documentation as the Company may reasonably request in
connection with such sale and, in case of a disposition pursuant to Rule 144,
shall deliver to the Company an executed copy of any notice on Form 144,
required to be filed with the Commission.

          2.4  Opinions.  Each Stockholder agrees that it will not Transfer any
               --------
Merger Shares without complying with each of the restrictions set forth herein
and agrees that in connection with any Transfer it will, if requested by the
Company, deliver at its expense to the Company an opinion of counsel, in form
and substance reasonably satisfactory to the Company and counsel for the
Company, that such Transfer is not in violation of the securities laws of the
United States of America.

       3. General Restriction on Transfer of Merger Shares:  Right of
          -----------------------------------------------------------
          First Refusal
          -------------

          3.1  Restriction on Transfer With Respect to Merger Shares.  Except
               -----------------------------------------------------
for Transfers otherwise permitted by Section 3.3, each Stockholder agrees that
it will not Transfer any Merger Shares at any time without complying with the
right of first refusal set forth in Section 3.2 hereof.

          3.2  Right of First Refusal.  If at any time a Stockholder receives a
               ----------------------
bona fide offer ("Offer") to purchase any or all of its Merger Shares from a
third party (the "Offeror") which the Stockholder wishes to accept and which is
fully financed, the Stockholder shall cause the Offer to be reduced to writing
and shall notify the Company in writing of its wish to accept the Offer.  The
Stockholder's notice shall contain an irrevocable offer to sell such Merger
Shares to the Company (in the manner set forth below) at a purchase price equal
to the price contained in, and on the same terms and conditions of, the Offer,
and shall be accompanied by a true copy of the Offer (which shall identify the
Offeror).  At any time within 30 days after the date of the receipt by the
Company of the Stockholder's notice, the Company (and its designee(s)) shall
have the right and option to purchase some or all of the Merger Shares covered
by the Offer either (i) at the same price and on the same terms and conditions
as the Offer or (ii) if the Offer includes any consideration other than cash,
then, at the sole option of the Company, at the all-equivalent cash price,
determined in good faith by the Company's Board of Directors, by delivering a
check or checks in the appropriate amount to the Stockholder against delivery of
certificates or instruments representing the Merger Shares so purchased,
appropriately endorsed by the Stockholder.  The Company may also elect (but
shall have no obligation) to cause its designee(s) to purchase the Merger Shares
covered by the Offer.  Subject to Section 6.2 hereof, if

                                      -3-
<PAGE>

at the end of such 30-day period the Company (and its designee(s)) has not
tendered the purchase price for all the Merger Shares in the manner set forth
above, the Stockholder may during the succeeding 90-day period sell the Merger
Shares not purchased by the Company covered by the Offer to the Offeror on terms
no less favorable to the Stockholder than those contained in the Offer. No sale
may be made to any Offeror unless the Offeror agrees in writing with the Company
to be bound by this Agreement. Promptly after such sale, the Stockholder shall
notify the Company of the consummation thereof and shall furnish such evidence
of the completion and time of completion of such sale and of the terms thereof
as may reasonably be requested by the Company. If, at the end of 90 days
following the expiration of the 30-day period during which the Company may
purchase the Merger Shares, the Stockholder has not completed the sale of such
Merger Shares as aforesaid, all the restrictions on Transfer contained in this
Agreement in effect at that time shall again be in effect with respect to such
Merger Shares. The parties agree that any Transfers to Soundview Financial,
Texas Instruments and any Laor Parties shall not be subject to this provision.

          3.3  Certain Permitted Transfers.  The provisions of Sections 3.1 and
               ---------------------------
3.2 shall not apply to the following Transfers of Merger Shares (each a
"Permitted Transfer"):

               (a)  a Transfer made by a Stockholder to the Company; and

               (b)  a Transfer made to any of the following "Permitted
Transferees":

                    (i) upon the death of the Stockholder, to its executors,
administrators, testamentary trustees, legatees or beneficiaries (the
"Stockholder's Estate") or a Transfer to the executors, administrators,
testamentary trustees, legatees or beneficiaries of a person who has become a
holder of Merger Shares in accordance with the terms of this Agreement;

                    (ii) a Transfer made to a trust or custodianship the
beneficiaries of which include only the Stockholder, any spouse and any lineal
descendants, including adopted children (a "Stockholder's Trust"); or

                    (iii) a Transfer to the Stockholder's spouse and any lineal
descendants, including adopted children.

          3.4  Conditions to Transfers of Merger Shares.  No Transfer of Merger
               ----------------------------------------
Shares, whether or not permitted by Sections 3.2 or 3.3, shall be made or
recorded on the books of the Company, and any such Transfer shall be void and of
no effect, unless:

               (a) (i) Such Transfer of the Merger Shares is made pursuant to an
effective registration statement under the Securities Act, or (ii) pursuant to
an exemption therefrom with respect to which the Company may, upon request,
require a satisfactory opinion of counsel for the Stockholder (which counsel
shall be acceptable to the Company) to the effect that such Transfer is exempt
from the provisions of Section 5 of the Securities Act; and

                                      -4-
<PAGE>

               (b) The transferee of the Merger Shares agrees to be bound by,
and executes a counterpart to, an agreement with the Company substantially in
the form of this Agreement.

          3.5  Notice of Change of Beneficiary.  Immediately prior to any
               -------------------------------
Transfer of Merger Shares to a Stockholder's Trust, the Stockholder shall
provide the Company with a copy of the instruments creating the Stockholder's
Trust with the identity of the beneficiaries of the Stockholder's Trust.  The
Stockholder shall notify the Company prior to any change in the identity of any
beneficiary of the Stockholder's Trust.

          3.6  Transfers Not in Compliance.  No Transfer of Merger Shares in
               ---------------------------
violation of this Agreement shall be made or recorded on the books of the
Company and any such Transfer shall be void and of no effect.

          3.7  Termination of Transfer Restrictions.  Subject to Section 4.3,
               ------------------------------------
the restrictions on Transfer set forth in this Section 3 shall terminate upon an
Initial Public Offering by the Company.

       4. Registration Rights
          -------------------

          4.1  Piggyback Registration Rights.
               -----------------------------

               (a)  Right to Piggyback. Subject to Sections 4.1(b) and 4.1(c)
                    ------------------
below, whenever the Company proposes to register any shares of Common Stock (or
securities convertible into or exercisable or exchangeable for, or options to
purchase, Common Stock) with the Commission under the Securities Act (other than
pursuant to an initial public offering, a registration on Form S-4 or S-8, or
any successor forms thereto) (a "Piggyback Registration"), the Company (i) will
give written notice to all Stockholders which hold Registrable Shares at least
30 days prior to the anticipated filing date, of its intention to effect such a
registration, which notice will specify the proposed offering price, the kind
and number of securities proposed to be registered, the distribution
arrangements and such other information that at the time would be appropriate to
include in such notice, and (ii) will, subject to Section 4.1(c) below, include
in such Piggyback Registration all Registrable Shares with respect to which the
Company has received written requests for inclusion therein within 20 days after
the date of the Company's notice. Except as may otherwise be provided in this
Agreement, Registrable Shares with respect to which such request for
registration has been received will be registered by the Company and offered to
the public in a Piggyback Registration pursuant to this Section 4 on terms and
conditions at least as favorable as those applicable to the registration of
shares of Common Stock to be sold by the Company and by any other person selling
under such Piggyback Registration.

               (b)  Number of Piggyback Registrations. Each Stockholder shall be
                    ---------------------------------
entitled to unlimited Piggyback Registrations.

               (c)  Priority on Piggyback Registrations. If the managing
                    -----------------------------------
underwriter or underwriters, if any, advises the selling Stockholders in writing
that in its or their reasonable opinion or, in the case of a Piggyback
Registration not being underwritten, the Company shall

                                      -5-
<PAGE>

reasonably determine (and notify the selling Stockholders of such
determination), after consultation with an investment banker of nationally
recognized standing, that the number or kind of securities proposed to be sold
in such registration (including Registrable Shares to be included pursuant to
Section 4.1(a) above) is inconsistent with that which can be sold in such
registration without having a material effect on the success of the offering
(including, without limitation, an impact on the selling price or the number of
securities that any participant may sell), the Company will include in such
registration the number of securities, if any, which, in the opinion of such
underwriter or underwriters, or the Company, as the case may be, can be sold as
follows: (i) first, the shares the Company proposes to sell, (ii) second, the
Common Stock requested to be included in such registration by the Company
Stockholders pursuant to the Amended and Restated Stockholders Agreement by and
among certain Company Stockholders dated as of December 2, 1999 (as the same may
be amended from time to time), (iii) third, to the Common Stock requested to be
included in such registration statement by Company Stockholders pursuant to the
rights of holders of any Common Stock, including Common Stock issued on the
conversion of any shares of preferred stock or debt of the Company, in each case
sold after the date hereof in a financing transaction, and (iv) fourth, the
Registrable Shares requested to be included in such registration by the
Stockholders and other holders of Common Stock of the Company which possess at
least as favorable Piggyback Registration rights as the Stockholders. To the
extent that the privilege of including Registrable Shares in any Piggyback
Registration must be allocated among the selling Stockholders pursuant to clause
(iv) above, the allocation shall be made pro rata based on the number of
Registrable Shares that each such Stockholder shall have requested to include
therein in relation to the total number of Registrable Shares held by all the
Stockholders.

          (d)  Selection of Underwriters.  If any Piggyback Registration is an
               -------------------------
underwritten offering, the Company will (i) select a managing underwriter or
underwriters to administer the offering, which managing underwriter or
underwriters will be of nationally recognized standing, and (ii) determine the
terms under which such underwriting shall take place.

          (e)  Withdrawal and Postponement. If, at any time after giving written
               ---------------------------
notice of its intention to register any equity securities and prior to the
effective date of the registration statement filed in connection with such
registration, the Company shall determine for any reason not to register or to
delay registration of such equity securities, the Company may, at its election,
give written notice of such determination to the Stockholder and (i) in the case
of a determination not to register, shall be relieved of its obligation to
register any Registrable Shares in connection with such abandoned registration
and (ii) in the case of a determination to delay such registration of its equity
securities, shall be permitted to delay the registration of such Registrable
Shares requested by the Stockholder to be included therein for the same period
as the delay in registering such other equity securities.

          4.2  Registration Procedures.  With respect to any Piggyback
               -----------------------
Registration, the Company will, subject to Section 4.1(c), as expeditiously as
practicable:

          (a)  prepare and file with the Commission a registration statement or
registration statements (the "Registration Statement") on any appropriate form
under the Securities Act, which form shall be available for the sale of the
Registrable Shares in accordance

                                      -6-
<PAGE>

with the intended method or methods of distribution thereof; and use its
commercially reasonable efforts to cause such Registration Statement to become
effective;

          (b)  prepare and file with the Commission such amendments and post-
effective amendments to the Registration Statement as may be necessary to keep
each Registration Statement effective for the applicable period, or such shorter
period which will terminate when all Registrable Shares covered by such
Registration Statement have been sold; cause each Prospectus to be supplemented
by any required Prospectus supplement, and as so supplemented to be filed
pursuant to Rule 424 under the Securities Act; and comply with the provisions of
the Securities Act with respect to the disposition of all securities covered by
such Registration Statement during the applicable period in accordance with the
intended method or methods of distribution by the sellers thereof set forth in
such Registration Statement or supplement to the Prospectus;

          (c)  notify the selling Stockholders and the managing underwriters, if
any, promptly, (i) when the Prospectus or any Prospectus supplement or post-
effective amendment has been filed, and, with respect to the Registration
Statement or any post-effective amendment, when the same has become effective,
(ii) of any request by the Commission for amendments or supplements to the
Registration Statement or the Prospectus or for additional information, (iii) of
the issuance by the Commission of any stop order suspending the effectiveness of
the Registration Statement or the initiation of any proceedings for that
purpose, (iv) of the receipt by the Company of any notification with respect to
the suspension of the qualification of the Registrable Shares for sale in any
jurisdiction or the initiation or threatening of any proceeding for such purpose
and (v) of the happening of any event which makes any statement made in the
Registration Statement, the Prospectus or any document incorporated therein by
reference untrue or which requires the making of any changes in the Registration
Statement, the Prospectus or any document incorporated therein by reference in
order to make the statements therein not misleading;

          (d)  make every reasonable effort to obtain the withdrawal of any
order suspending the effectiveness of the Registration Statement at the earliest
possible moment;

          (e)  use its commercially reasonable efforts to cause the Registrable
Shares covered by the applicable Registration Statement to be registered with or
approved by such other governmental agencies or authorities as may be necessary
to enable the seller or sellers thereof or the underwriters, if any, to
consummate the disposition of such Registrable Shares;

          (f)  use its commercially reasonable efforts to cause all Registrable
Shares covered by any Registration Statement to be listed on each securities
exchange on which similar securities issued by the Company are then listed, or
cause such Registrable Shares to be authorized for trading on the NASDAQ
National Market System if any similar securities issued by the Company are then
so authorized, if requested by the holders of a majority of such Registrable
Shares or the managing underwriters, if any;

          (g)  upon the occurrence of any event contemplated by Section
4.2(c)(v) above, prepare a supplement or post-effective amendment to the
Registration Statement

                                      -7-
<PAGE>

or the related Prospectus or any document incorporated therein by reference or
file any other required document so that, as thereafter delivered to the
purchasers of the Registrable Shares, the Prospectus will not contain an untrue
statement of a material fact or omit to state any material fact necessary to
make the statements therein not misleading;

          (h)  otherwise use its commercially reasonable efforts to comply with
all applicable rules and regulations of the Commission.

     The Company may require each seller of Registrable Shares as to which any
Piggyback Registration is being effected to furnish to the Company such
information regarding the proposed distribution of such securities as the
Company may from time to time reasonably request in writing.

     Each Stockholder agrees by acquisition of such Registrable Shares
that, upon receipt of any notice from the Company of the happening of any event
of the kind described in Section 4.2(c)(v), such Stockholder will forthwith
discontinue disposition of Registrable Shares pursuant to the Registration
Statement until such Stockholder's receipt of copies of the supplemented or
amended Prospectus as contemplated by Section 4.2(g); or until it is advised in
writing (the "Advice") by the Company that the use of the Prospectus may be
resumed, and has received copies of any additional or supplemental filings that
are incorporated by reference in the Prospectus, and, if so directed by the
Company, such Stockholder will deliver to the Company (at the Company's expense)
all copies, other than permanent file copies then in such Stockholder's
possession, of the Prospectus covering such Registrable Shares.

          4.3  Restrictions on Public Sale.  To the extent not inconsistent with
               ---------------------------
applicable law, (i) each Stockholder agrees not to effect any public sale or
distribution of Registrable Shares, including a sale pursuant to Rule 144 (or
any similar provision then in force) under the Securities Act, during the 180-
day period (or such shorter period as may be consented to by the managing
underwriter or underwriters, and the Company agrees to use its commercially
reasonable efforts to cause any such consent granted by any underwriter to be
made available to all other holders of Registrable Shares on a ratable basis)
following its initial public offering (whether or not a Qualified Offering), and
(ii) each Stockholder whose Registrable Shares are included in a Registration
Statement hereunder, if requested by the managing underwriter or underwriters
for such Piggyback Registration, agrees not to effect any public sale or
distribution of Registrable Shares, including a sale pursuant to Rule 144 (or
any similar provision then in force) under the Securities Act, during the 15
business days prior to, and during the 90-day period (or such shorter period as
may be consented to by such underwriter or underwriters, which consent, if
granted, will be made available to all other holders of Registrable Shares on a
ratable basis) following the effective date of a Registration Statement pursuant
to such Piggyback Registration (except as part of such Piggyback Registration).

          4.4  Registration Expenses.  All expenses incident to the Company's
               ---------------------
performance of or compliance with this Section 4 will be borne by the Company,
including, without limitation, all registration and filing fees, the fees and
expenses of the counsel and accountants for the Company (including the expenses
of any "cold comfort" letters and special audits required by or incident to the
performance of such persons), all other costs and expenses of the Company
incident to the preparation, printing and filing under the Securities Act of the

                                      -8-
<PAGE>

Registration Statement (and all amendments and supplements thereto) and
furnishing copies thereof and of the Prospectus included therein, the costs and
expenses incurred by the Company in connection with the qualification of the
Registrable Shares under the state securities or "Blue Sky," laws of various
jurisdictions, the costs and expenses associated with filings required to be
made with the NASD (including, if applicable, the fees and expenses of any
"qualified independent underwriter" and its counsel as may be required by the
rules and regulations of the NASD), the costs and expenses of listing the
Registrable Shares for trading on a national securities exchange or authorizing
them for trading on the NASDAQ National Market System and all other costs and
expenses incurred by the Company in connection with any Piggyback Registration
hereunder; provided, however, that the Company shall not bear the costs and
           --------  -------
expenses of any selling Stockholder for underwriters' commissions, brokerage
fees or transfer taxes, or the fees and expenses of any counsel, accountants or
other representative retained by any selling Stockholder.

     4.5  Indemnification.
          ---------------

          (a) Indemnification by the Company.  The Company agrees to indemnify,
              ------------------------------
to the full extent permitted by law, each Stockholder, its officers, directors
and agents and each person who controls such Stockholder within the meaning of
the Securities Act and the Exchange Act (each, an "Indemnified Holder"), against
all losses, claims, damages, liabilities and expenses caused by any untrue or
alleged untrue statement of a material fact contained in any Registration
Statement, Prospectus or preliminary Prospectus, or any omission or alleged
omission to state therein a material fact necessary to make the statements
therein (in the case of a Prospectus or any preliminary Prospectus, in light of
the circumstances under which they were made) not misleading, except to the
extent that such untrue statement or omission is caused by any information with
respect to such Indemnified Holder furnished in writing to the Company by such
Indemnified Holder or its representative expressly for use therein.

          (b) Indemnification by Holders of Registrable Shares.  In connection
              ------------------------------------------------
with any Piggyback Registration, each Stockholder participating therein will
furnish to the Company in writing such information with respect to the
Stockholder as the Company reasonably requests for use in connection with any
Registration Statement, Prospectus or preliminary Prospectus, and agrees to
indemnify, to the full extent permitted by law, the Company, the directors and
officers of the Company signing the Registration Statement and each person who
controls the Company (within the meaning of the Securities Act and the Exchange
Act) against any losses, claims, damages, liabilities and expenses resulting
from any untrue statement of a material fact or any omission to state a material
fact required to be stated therein or necessary to make the statements in the
Registration Statement, Prospectus or preliminary Prospectus (in the case of the
Prospectus or any preliminary Prospectus, in light of the circumstances under
which they were made) not misleading, to the extent, and only to the extent,
that such untrue statement or omission is caused by any information with respect
to the Stockholder so furnished in writing by the Stockholder or its
representative specifically for inclusion therein. In no event shall the
liability of any selling Stockholder hereunder be greater in amount than the
dollar amount of the net proceeds (after deducting commissions and expenses)
received by such Stockholder upon the sale of the Registrable Shares giving rise
to such indemnification obligation. The Company shall be entitled to receive
indemnities from underwriters, selling brokers, dealer managers and similar
securities industry professionals

                                      -9-
<PAGE>

participating in the distribution, to the same extent as provided above with
respect to information with respect to such persons or entities so furnished in
writing by such persons or entities or their representatives specifically for
inclusion in any Registration Statement, Prospectus or preliminary Prospectus.

          (c)  Conduct of Indemnification Proceedings.  Any person or entity
               --------------------------------------
entitled to indemnification hereunder will (i) give prompt written notice to the
indemnifying party after the receipt by the indemnified party of a written
notice of the commencement of any action, suit, proceeding or investigation or
threat thereof made in writing for which such indemnified party will claim
indemnification or contribution pursuant to this Agreement; provided, however,
                                                            --------  -------
that the failure of any indemnified party to give notice as provided herein
shall not relieve the indemnifying party of its obligations under the preceding
Section 4.5(a) or 4.5(b), as applicable, except to the extent that the
indemnifying party is actually prejudiced by such failure to give notice and
(ii) unless in such indemnified party's reasonable judgment a conflict of
interest may exist between such indemnified and indemnifying parties with
respect to such claim, permit such indemnifying party to assume the defense of
such claim with counsel reasonably satisfactory to the indemnified party.
Whether or not such defense is assumed by the indemnifying party, the
indemnifying party will not be subject to any liability for any settlement made
without its consent (but such consent will not be unreasonably withheld). No
indemnifying party will be required to consent to the entry of any judgment or
to enter into any settlement that does not include as an unconditional term
thereof the giving by the claimant or plaintiff of a release from all liability
in respect of such claim or litigation. An indemnifying party who is not
entitled to, or elects not to, assume the defense of a claim will not be
obligated to pay the fees and expenses of more than one counsel in any one
jurisdiction for all parties indemnified by such indemnifying party with respect
to such claim, unless in the reasonable judgment of any indemnified party a
conflict of interest may exist between such indemnified party and any other of
such indemnified parties with respect to such claim, in which event the
indemnifying party shall be obligated to pay the fees and expenses of such
additional counsel or counsels.

          (d)  Contribution.  If for any reason the indemnification provided for
               ------------
in the preceding Section 4.5(a) or 4.5(b), as applicable, is unavailable to an
indemnified party as contemplated by such Section, then the indemnifying party,
in lieu of indemnification, shall contribute to the amount paid or payable by
the indemnified party as a result of such loss, claim, damage, liability or
expense in such proportion as is appropriate to reflect not only the relative
benefits received by the indemnified party and the indemnifying party, but also
the relative fault of the indemnified party and the indemnifying party, as well
as any other relevant equitable considerations; provided, however, that no
                                                --------  -------
selling Stockholder shall be required to contribute in an amount greater than
the difference between the net proceeds received by the Stockholder with respect
to the sale of Registrable Shares and all amounts already contributed by the
Stockholder with respect to such claims, including amounts paid for any legal or
other fees or expenses incurred by the Stockholder.

          4.6   Participation in Underwritten Registrations.  No Stockholder may
                -------------------------------------------
participate in any underwritten registration hereunder unless such Stockholder
(i) agrees to sell its Registrable Shares on the basis provided in any
underwriting arrangements approved by the Company, and (ii) accurately completes
in a timely manner and executes all questionnaires,

                                     -10-
<PAGE>

powers of attorney, underwriting agreements and other documents customarily
required under the terms of such underwriting arrangements.

       5. Miscellaneous Provisions
          ------------------------

          5.1  Legend.  In addition to any legends required by federal or state
               ------
securities laws, the certificates representing the Merger Shares shall bear the
following legend:

     THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
     RESTRICTIONS ON TRANSFER AND OTHER PROVISIONS SET FORTH IN A SUPPLEMENTAL
     STOCKHOLDERS' AGREEMENT DATED AS OF OCTOBER 10, 2000, AS AMENDED FROM TIME
     TO TIME. A COPY OF SUCH AGREEMENT MAY BE OBTAINED FROM THE COMPANY UPON
     REQUEST.

          5.2  Transferees; Additional Restriction on Transfer.  Each transferee
               -----------------------------------------------
of Merger Shares from a Stockholder or a subsequent transferee (including the
transferee in a transfer from one Stockholder to another Stockholder) shall take
such Merger Shares subject to the same restrictions as existed in the hands of
the transferor, including, without limitation, the restrictions imposed on
Stockholders under Section 3 hereof and restrictions on the sale of Merger
Shares under Section 4.3(a) hereof.  No transferee of Merger Shares from a
Stockholder or a subsequent transferee, (other than a transferee receiving
Merger Shares in a Permitted Transfer under Section 3.3) shall be entitled to
the benefits provided to Stockholders hereunder, including, without limitation,
the registration rights under Section 4 hereof.

          5.3  Specific Performance, Etc.  The Company and each Stockholder, in
               -------------------------
addition to being entitled to exercise all rights provided herein, in the
Company's Certificate of Incorporation or granted by law, including recovery of
damages, shall be entitled to specific performance of its rights under this
Agreement. Each party agrees that monetary damages would not be adequate
compensation for any loss incurred by reason of a breach by it of the provisions
of this Agreement and hereby agrees to waive the defense in any action for
specific performance that a remedy at law would be adequate.

          5.4  Notices.  All notices, requests, demands and other communications
               -------
which are required or may be given under this Agreement shall be in writing and
shall be deemed to have been duly received when received if personally
delivered; when transmitted if transmitted by telecopy, electronic or digital
transmission method; the day after it is sent, if sent for next day delivery to
a domestic address by recognized overnight delivery service (e.g., FedEx); and
                                                             ----
upon receipt, if sent by certified or registered mail, return receipt requested.
In each case notice shall be sent to the parties at their addresses listed on
Annex I attached hereto, or to such other place and with such other copies as
any party may designate as to itself or himself by written notice to the others.

          5.5  Entire Agreement; Amendments and Waivers.  This Agreement
               ----------------------------------------
constitutes the entire agreement among the parties pertaining to the subject
matter hereof and supersedes all prior agreements, understandings, negotiations
and discussions, whether oral or written, of the parties hereto.  The provisions
of this Agreement, including the provisions of this sentence, may

                                     -11-
<PAGE>

not be amended, modified or supplemented, and waivers of or consents to
departures from the provisions hereof may not be given unless approved in
writing by the Company and the holders of sixty-six and two thirds percent (66-
2/3%) of the Merger Shares then outstanding; provided, however, that this
                                             --------  -------
Agreement shall be automatically amended to include any Permitted Transferee of
a Stockholder. No action taken pursuant to this Agreement, including, without
limitation, any investigation by or on behalf of any party, shall be deemed to
constitute a waiver by the party taking such action. The waiver by any party
hereto of a breach of any provision of this Agreement shall not operate or be
construed as waiver of any preceding or succeeding breach and no failure by any
party to exercise any right or privilege hereunder shall be deemed a waiver of
such party's rights or privileges hereunder or shall be deemed a waiver of such
party's rights to exercise the same at any subsequent time or times hereunder.

          5.6  Termination.  If not terminated sooner pursuant to the terms
               -----------
hereof, Section 3 of this Agreement (regarding rights of first refusal) shall
terminate and cease to be of any further force or effect upon the Company's
merger with and into another corporation or other entity where, upon
consummation of the merger, the holders of the Company's voting stock
immediately prior to the merger will hold less than 50% of the voting stock of
the surviving corporation immediately after the merger.  If not terminated
sooner pursuant to the terms hereof, Section 4 of this Agreement (regarding
registration rights) shall terminate and cease to be of any further force or
effect upon the Company's merger with and into another corporation where, in
connection with the merger, the Merger Shares are exchanged exclusively for cash
and/or shares of capital stock or other securities that are publicly traded on a
national securities exchange or authorized for trading on the Nasdaq National
Market System.

          5.7  Recapitalizations, Exchange, Etc. Affecting the Company's Stock.
               ---------------------------------------------------------------
The provisions of this Agreement shall apply, to the full extent set forth
herein with respect to the Merger Shares, to any and all shares of capital stock
of the Company that may be issued in respect of, in exchange for, or in
substitution of the Merger Shares and shall be appropriately adjusted for any
stock dividends, splits, reverse splits, combinations, recapitalizations and the
like occurring after the date hereof.

          5.8  Multiple Counterparts.  This Agreement may be executed in one or
               ---------------------
more counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

          5.9  Headings.  The headings of the Articles herein are inserted for
               --------
convenience of reference only and are not intended to be part of or to affect
the meaning or interpretation of this Agreement.

          5.10 Governing Law.  This Agreement shall be governed by and construed
               -------------
in accordance with the internal laws of the State of Delaware, without regard to
principles of conflict of laws.

          5.11 Construction.  Differences in language as between similar
               ------------
provisions covering similar matters may reflect differences in style rather than
a different substantive intent and should be construed accordingly.

                                     -12-
<PAGE>

          5.12 Invalidity.  In the event that any one or more of the provisions
               ----------
contained in this Agreement or in any other document or instrument referred to
herein, shall, for any reason, be held to be invalid, illegal or unenforceable
in any respect, then to the maximum extent permitted by law, such invalidity,
illegality or unenforceability shall not affect any other provision of this
Agreement or any other such document or instrument

          5.13 Cumulative Remedies.  All rights and remedies of either party
               -------------------
hereto are cumulative of each other and of every other right or remedy such
party may otherwise have at law or in equity, and the exercise of one or more
rights or remedies shall not prejudice or impair the concurrent or subsequent
exercise of other rights or remedies.

                (BALANCE OF THIS PAGE INTENTIONALLY LEFT BLANK)

                                     -13-
<PAGE>

     IN WITNESS WHEREOF, the undersigned have executed this Agreement as of the
date set forth above.

                         TELLIUM, INC.

                         By:    /s/  Nicholas DeVito
                              ---------------------------------
                              Name:  Nicholas DeVito
                              Title:    VP Business Development

                                /s/ Gregory Alper
                              ------------------------------------

                                /s/ Gunnar Andersson
                              ------------------------------------

                                /s/ Robert Angliss
                              ------------------------------------

                                /s/ Trisha N. Allen
                              ------------------------------------

                                /s/ Paula Baker
                              ------------------------------------

                                /s/ Robert Baker
                              ------------------------------------

                                /s/ Linda Balas
                              ------------------------------------

                                /s/ David Blake, Jr. & Julie Blake
                              ------------------------------------

                                /s/ Deborah Bokar
                              ------------------------------------
                              Deborah Bokar Living Trust

                                /s/ Betsy Brigs-Nogueira
                              ------------------------------------

                                /s/ Michael R. Brown
                              ------------------------------------

                                     -14-
<PAGE>

                             /s/ Louis Cairo
                             ---------------------------------------

                             /s/ John Campbell
                             ---------------------------------------

                             /s/ Rudolf Carl
                             ---------------------------------------
                             Rudolf Carl Trust

                             /s/ Robert Greenlee
                             ----------------------------------------
                             President
                             Centennial Investment Management

                             /s/ Daisy Chong
                             ---------------------------------------

                             /s/ Ross P. Cooney
                             ---------------------------------------

                             /s/ Barry Costello
                             ----------------------------------------

                             /s/ Barbara A. Cross
                             ----------------------------------------

                             /s/ John Crowley
                             ---------------------------------------

                             /s/ French S. Durst
                             -----------------------------------------

                             /s/ Ronald K. Elliott
                             ------------------------------------------

                             /s/ William Fee
                             ------------------------------------------

                             /s/ S. Lisa Ferreira
                             ------------------------------------------

                             /s/ Gary Flack
                             ------------------------------------------

                                     -15-
<PAGE>

                             /s/ Edouard J. Fontenot
                             ------------------------------------------

                             /s/ Edward Fontenot
                             ------------------------------------------

                             /s/ Marie Y. Fontenot
                             ------------------------------------------

                             /s/ Michael Friedenbach
                             ------------------------------------------

                             /s/ Mary Ann Golay
                             ------------------------------------------

                             /s/ Michael Goldberg
                             ------------------------------------------

                             /s/ Brad Golson
                             ------------------------------------------

                             /s/ David Greenberg
                             ------------------------------------------

                             /s/ Lou Greenberg
                             ------------------------------------------

                             /s/ Robert Greenlee
                             ------------------------------------------

                             /s/ Courtney Hendrix
                             ------------------------------------------

                             /s/ Jean Hogan
                             ------------------------------------------

                             /s/ Anthony & Carolyn Jeffries
                             ------------------------------------------

                             /s/ Bradley N. Jennings
                             ------------------------------------------

                             /s/ Michael Kahn
                             ------------------------------------------

                                     -16-
<PAGE>

                             /s/ Sheldon Kahn
                             ------------------------------------------

                             /s/ Bonnie Kassell
                             ------------------------------------------

                             /s/ Stuart M. Leudan
                             ------------------------------------------
                             President
                             Katz Family Limited Partnership

                             /s/ Bernard R. Kornhaber
                             ------------------------------------------
                             Bernard Kornhaber Revocable Trust

                             /s/ Marda Kornhaber
                             ------------------------------------------

                             /s/ Anne Lenot
                             ------------------------------------------

                             /s/ Stuart Leudan
                             ------------------------------------------

                             /s/ Anne Livingston
                             ------------------------------------------

                             /s/ Robert Logelin
                             ------------------------------------------

                             /s/ Paul Lurie
                             ------------------------------------------

                             /s/ David Monson
                             ------------------------------------------

                             /s/ Tammy Muller
                             ------------------------------------------

                             /s/ Carol Jean Myren
                             ------------------------------------------

                             /s/ William H. Pearlman
                             ------------------------------------------
                             General Partner
                             Pearlman Family Limited Partnership

                                     -17-
<PAGE>

                             /s/ Charles Peres
                             ----------------------------------------------

                             /s/ Rainerio Reyes
                             ----------------------------------------------

                             /s/ Alan T. Richards
                             ----------------------------------------------

                             /s/ Michele Rueckert
                             ----------------------------------------------

                             /s/ Carolyn E. Shaffer
                             ----------------------------------------------

                             /s/ Jonathan Sheinkop
                             ----------------------------------------------

                             /s/ Michael Sheinkop
                             ----------------------------------------------

                             /s/ Mitchell B. Sheinkop
                             ----------------------------------------------

                             /s/ Donald Shwayder
                             ----------------------------------------------

                             /s/ Scott Shwayder
                             ----------------------------------------------

                             /s/ Dan Smathers
                             ----------------------------------------------

                             /s/ Richard Stauter
                             ----------------------------------------------

                             /s/ Paul Sugar and Judith Sugar
                             ----------------------------------------------
                             Paul Sugar and Judith Sugar Joint Living Trust

                             /s/ Carl Symons
                             ----------------------------------------------

                             /s/ Carol Coghlan Gavin
                             ----------------------------------------------
                             Tellabs, Inc.

                                     -18-
<PAGE>

                             By Carol Coghlan Gavin
                             Vice President, General Counsel and Secretary

                             /s/ May Vang Vue
                             -----------------------------------------

                             /s/ Zandra Voss-Wagner
                             -----------------------------------------

                             /s/ Eugene Weisman
                             -----------------------------------------

                             /s/ Larry Weisman
                             -----------------------------------------

                             /s/ John C. Wittenberger
                             -----------------------------------------

                             /s/ Arthur Wong
                             -----------------------------------------

                             /s/ Philip Wong
                             -----------------------------------------

                             /s/ Doua Xiong
                             -----------------------------------------

                             /s/ Fong Yang
                             -----------------------------------------

                                     -19-
<PAGE>

                                   EXHIBIT A
                                   ---------

Gregory Alper

Gunnar Andersson

Robert Angliss

Trisha N. Allen

Paula Baker

Robert Baker

Linda Balas

David Blake, Jr. & Julie Blake

Deborah Bokar Living Trust

Betsy Brigs-Nogueira

Michael R. Brown

Louis Cairo

John Campbell

Rudolf Carl Trust

Centennial Investment Management

Daisy Chong

Ross P. Cooney

Barry Costello

Barbara A. Cross

John Crowley

French S. Durst

Ronald K. Elliott

                                     -20-
<PAGE>

William Fee

S. Lisa Ferreira

Gary Flack

Edouard J. Fontenot

Edward Fontenot

Marie Y. Fontenot

Michael Friedenbach

Mary Ann Golay

Michael Goldberg

Brad Golson

David Greenberg

Lou Greenberg

Robert Greenlee

Courtney Hendrix

Jean Hogan

Anthony & Carolyn Jeffries

Bradley N. Jennings

Michael Kahn

Sheldon Kahn

Bonnie Kassell

Katz Family Limited Partnership

Bernard Kornhaber Revocable Trust

Marda Kornhaber

                                     -21-
<PAGE>

Anne Lenot

Stuart Leudan

Anne Livingston

Robert Logelin

Paul Lurie

David Monson

Tammy Muller

Carol Jean Myren

Pearlman Family Limited Partnership

Charles Peres

Rainerio Reyes

Alan T. Richards

Michele Rueckert

Carolyn E. Shaffer

Jonathan Sheinkop

Michael Sheinkop

Mitchell B. Sheinkop

Donald Shwayder

Scott Shwayder

Dan Smathers

Richard Stauter

Paul Sugar and Judith Sugar Joint Living Trust

Carl Symons

                                     -22-
<PAGE>

Tellabs, Inc.

May Vang Vue

Zandra Voss-Wagner

Eugene Weisman

Larry Weisman

John C. Wittenberger

Arthur Wong

Philip Wong

Doua Xiong

Fong Yang

                                     -23-

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