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Note: Redacted portions have been marked with (***). The redacted portions are
subject to a request for confidential treatment that has been filed with the
Securities And Exchange Commission.


                                                                   EXHIBIT 10.27

                              DYNEGY CONNECT, L.P.
                       2821 South Parker Road, Suite 700
                             Aurora, Colorado 80014

                                November 6, 2000


Tellium, Inc.
2 Crescent Place
P.O. Box 901
Oceanport, NJ 07757-0901
Attn: Mr. Nick DeVito, Vice President

     Re:  First Amendment to Purchase Agreement, made as of September 21, 1999
          ("Purchase Agreement"), by and between Dynegy Connect, LP, a Delaware
            ------------------
          limited parnership ("Dynegy Connect") (as indirect successor to
          Extant, Inc.) and Tellium, Inc. ("Tellium")
                                            -------

Dear Mr. DeVito:

     Reference is made to the Purchase Agreement. All capitalized terms that are
     used herein but not defined shall have the meaning ascribed to them in the
     Purchase Agreement.

     This amendment (the "Amendment") to the Purchase Agreement is effective as
                          ---------
     of the date above written.

     For good and valuable consideration, the receipt and sufficiency of which
     is hereby acknowledged, and intending to be legally bound hereby, the
     parties agree as follows:

     The Purchase Agreement is hereby amended as follows:

     1.  Section 1 shall be deleted in its entirety and replaced with the
         following:

          (a) Scope: Subject to the terms, provisions and conditions hereinafter
          set forth, during the term of this Agreement, Dynegy Connect, L.P. and
          the other Authorized Purchasers (as defined in Section 1(b) below),
          including but not limited to European Affiliates of Dynegy Inc., agree
          to purchase, and Tellium agrees to sell, deliver and, if agreed to by
          the parties, install their full optical switch requirements during the
          three (3) year period ending November 1, 2003, including hardware and
          software ("Products") at the prices set forth on Schedule C attached
                                                           ----------
          hereto; provided, however, any commitment to purchase Products shall
          be subject to the Products meeting, in the Authorized Purchaser's
          reasonable discretion, performance standards and current technology
          being deployed at any time during the term of this Agreement. Subject
          to the foregoing, it is expected that Dynegy Connect shall
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Note: Redacted portions have been marked with (***). The redacted portions are
subject to a request for confidential treatment that has been filed with the
Securities And Exchange Commission.


          purchase approximately Two Hundred and Fifty Million Dollars
          ($250,000,000) of Products and installation services described in the
          Schedules, attached hereto and made a part of this Agreement from
          Tellium during the term of this Agreement. It is the intention of the
          parties that Products shall be delivered in such quantities and at
          such times as is set forth in Schedule A attached hereto.
                                        -----------

          (b)  Definitions: For purposes of this Agreement, the following terms
          shall have the following meanings:

                     (1) "Affiliate" shall mean with respect to a person, any
                     other person directly or indirectly controlling, controlled
                     or under common control with such person. For purposes of
                     this definition, "control" when used with respect to any
                     person means the power to direct the management and
                     policies of such person, directly or indirectly, whether
                     through the ownership of voting securities, by contract, or
                     otherwise; and the terms "controlling" and "controlled"
                     have meanings correlative to the foregoing.

                     (2)  "Authorized Purchaser" shall mean

                            (a) DCP Leasing, L.L.C., Dynegy Connect, L.P. or
                            Dynegy Global Communications, Inc. (collectively
                            referred to herein as the "Dynegy Entities");
                                                       ---------------


                            (b)  (***);

                            (c)  (***); and/or

                            (d)  (***).

     2.  The first paragraph of Section 3 shall be deleted in its entirety and
replaced with the following:

          Dynegy Connect will issue purchase orders ("Orders") to Tellium for
       delivery and installation of Products, which Orders will be based on the
       Forecasts (as defined below) delivered pursuant to Section 3.1.

          Other Authorized Purchasers may issue purchase orders to Tellium under
       the Purchase Agreement provided that (i) such Authorized Purchasers agree
       to be bound all applicable terms and conditions of the Purchase Agreement
       insofar, but only insofar, as they relate to the purchase orders issued
       by such Authorized Purchaser and the equipment delivered pursuant to such
       purchase orders, which applicable terms and conditions shall include,
       without limitation, those set forth in this Section 3 and Sections
       4, 5, 6, 8, 10, 14, 16, 23, 29 and 30, and (ii) if the Authorized
       Purchaser for a purchase order is any person other than (***), Dynegy
       Connect or Dynegy Global

                                      -2-
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subject to a request for confidential treatment that has been filed with the
Securities And Exchange Commission.

       Communications, Inc. then such Authorized Purchaser shall meet the
       reasonable credit criteria employed by Tellium.

           Tellium shall provide Dynegy Connect or such other Authorized
       Purchaser with notice of acceptance of such Order within seven (7) days
       of receipt of the Order. Every Order shall contain a description of the
       Products ordered, the quantities and prices, the delivery date(s), and
       the place of delivery. All such Orders will be made pursuant and subject
       to this Agreement, whether specifically stated or not. In the event of a
       conflict or variance between the terms and conditions of an Order and the
       terms and conditions of this Agreement, the terms and conditions of this
       Agreement shall govern.

           All purchases made by any Authorized Purchaser will be deemed to be
       purchases made by Dynegy Connect (as successor to Extant) for purposes of
       calculating any volume discounts and for purposes of calculating the
       number of, and the vesting of, the Warrants.

    3. Section 4 shall be deleted in its entirety and replaced with the
       following:

                Tellium shall deliver the Products by the delivery date(s) set
          forth in the applicable Order but in no event shall delivery occur
          after the (* * *) after receipt of the Order unless otherwise agreed
          in writing between the Authorized Purchaser and Tellium. In the event
          that delivery of an Order is not made within the respective time
          period specified in Section 29.2, the Authorized Purchaser shall have
          the right to terminate this Agreement in accordance with Section 29.2.
          The Authorized Purchaser's acceptance of the Products shall be in
          accordance with Section 6 at the destination(s) specified in the
          Order. All deliveries shall be F.O.B. Oceanport, New Jersey. Title and
          risk of loss or damage to the Products shall remain with Tellium until
          delivery of the Product to a common carrier for delivery to the
          Authorized Purchaser. Customer shall pay shipping and insurance
          charges. Loss, damage or destruction subsequent to Delivery of the
          Products shall not relieve the Authorized Purchaser or of its
          obligations to pay for the Products.

     4.   Section 5 shall be deleted in its entirety and replaced with the
following:

                (a)  The pricing for Products shall be as set forth in
             Schedule C attached hereto. The prices set forth in Schedule C
             ----------                                          ----------
             are exclusive of all federal, state or local sales, excise, use,
             value added, import or export or similar taxes, other than taxes
             based upon Tellium's net income or corporate franchise. Tellium may
             invoice Customer for any taxes which Tellium will be required to
             collect or pay.

                (b)  All payments shall be made in U.S. Dollars.

                (c)  Products and installation services shall be invoiced
             separately. Products shall be invoiced within (* * *) of delivery
             and installation services shall be invoiced upon acceptance (as
             defined in Section 6).

                                      -3-
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subject to a request for confidential treatment that has been filed with the
Securities And Exchange Commission.



                (d)  All invoices shall be due net (* * *) from the date of
            invoice.

                (e)  For any amount due hereunder which remains unpaid after its
            due date, Customer shall pay Tellium a service fee of (* * *) of the
            amount due that remains unpaid.

                (f)  (* * *) shall (* * *) and (* * *) the (* * *) to the
            (* * *) for (* * *) to (* * *) or (* * *).

                (g)  Tellium shall provide Engineer & Furnish (Pre-wired and
            Tested OXC) services as set forth in Schedule C, Table 3 for the
                                                 ----------
            first (* * *).

                (h)  When the Authorized Purchasers have (* * *) for (* * *)
            of (* * *), Tellium (* * *) a (* * *) of (* * *) to (* * *) for
            (* * *) stated in (***).

   5. Section 6 is amended as follows:

                (a) The insertion of an (a) at the very beginning of such
            section.

                (b) Each reference to "(* * *)" in Section 6 shall be replaced
            with "(* * *)."

                (c) The following subsection (b) shall be added to Section 6:

                      (b) Installation Services: Acceptance shall have occurred
                      with respect to installation services on the earlier of
                      (* * *) following installation or the carrying of live
                      traffic on the network.

   6. Section 8 shall be deleted in its entirety and replaced with the
following:

          IMPORT/EXPORT.  Each Authorized Purchaser hereby covenants that no
          commodities or technical data (including computer software) or other
          technology agreed to be sold or otherwise transferred under this
          Agreement will be sold, leased, delivered, transferred or conveyed to
          any person in any country except in strict compliance with all export
          and import laws, regulations, executive orders or decrees of the
          United States Government or any agencies thereof and the government of
          any other country (or agencies thereof) with jurisdiction over such
          transaction. Each Authorized Purchaser shall, solely at its own
          expense, obtain all required export and import licenses, permits,
          approvals, certificates and verifications before shipment of any
          Products.

   7. A new paragraph shall be added to Section 16 which shall read as follows:

          Notwithstanding any other provision of the Purchase Agreement, Tellium
          may (i) disclose the terms of this Amendment in any filing with the
          Securities and

                                      -4-
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subject to a request for confidential treatment that has been filed with the
Securities And Exchange Commission.

          Exchange Commission and (ii) file this Amendment with the Securities
          and Exchange Commission, provided that it uses (* * *) to seek
          confidential treatment with respect to the filing referred to in
          Clause (ii) of this Section 7.

     8. Section 29.2 (c) shall be deleted in its entirety.


     This Letter Agreement may be executed in two or more counterparts, and it
shall not be necessary that the signatures of all parties hereto be contained on
any one counterpart hereof; each counterpart shall be deemed an original, but
all of which together shall constitute one and the same instrument. Delivery of
an executed signature page of this Letter Agreement by facsimile transmission
shall be effective as delivery of a manually-executed counterpart hereof.


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                                      -5-
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Note: Redacted portions have been marked with(***). The redacted portions are
subject to a request for confidential treatment that has been filed with the
Securities and Exchange Commission.

  Please execute below to evidence your agreement to the foregoing.

                                              Very truly yours,

                                              DYNEGY CONNECT, L.P.

                                              By:   /s/ Michael S. Sava
                                                 --------------------------
                                              Name:  Michael S. Sava
                                              Title: Executive Vice President



ACCEPTED AND AGREED TO:


TELLIUM, INC.



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


DCP LEASING,L.L.C., as Construction Agent for
Polaris Connect Statutory Trust

By:   /s/ Michael S. Sava
    --------------------------
Name:  Michael S. Sava
      ------------------------
Title: Executive Vice President
       ------------------------

DYNEGY GLOBAL COMMUNICATIONS, INC.



By:   /s/ Michael G. Gray
    --------------------------
Name:  Michael G. Gray
      ------------------------
Title: Vice President
       ------------------------

                                      -6-