Document:

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                                                                    EXHIBIT 10.2

                      ASSIGNMENT AND ASSUMPTION AGREEMENT

          This ASSIGNMENT AND ASSUMPTION AGREEMENT is made, executed and
delivered as of August 11, 2000 (as amended, amended and restated, supplemented,
or otherwise modified from time to time, this "Agreement") by and between
FIBERNET TELECOM GROUP, INC. (formerly known as FiberNet Holdco, Inc.), a
Delaware corporation (the "Parent") and FIBERNET OPERATIONS, INC. (formerly
known as FiberNet Telecom Group, Inc.), a Delaware corporation (the
"Subsidiary").

                                    RECITALS
                                    --------

          A.  The Subsidiary entered into an Agreement and Plan of
Reorganization, dated June 2, 2000 (as amended, amended and restated,
supplemented, or otherwise modified from time to time, the "Merger Agreement"),
pursuant to which, among other things, the Parent and the Subsidiary agreed
that, in accordance with the terms and conditions set forth therein (i) the
Subsidiary formed one subsidiary, FiberNet Holdco, Inc. ("Holdco"), and Holdco
formed two subsidiaries, FiberNet Merger Sub, Inc. ("FiberNet Merger Sub"), and
Devnet Merger Sub, LLC ("Devnet Merger Sub").  Holdco was a wholly-owned
subsidiary of the Subsidiary, and each of FiberNet Merger Sub and Devnet Merger
Sub was a wholly-owned subsidiary of Holdco, (ii) FiberNet Merger Sub, Inc.
merged with and into the Subsidiary, with the Subsidiary continuing as the
surviving corporation, (iii) in connection with such merger, the Subsidiary
changed its name to FiberNet Operations, Inc. ("FiberNet Operations") and the
Parent changed its name to FiberNet Telecom Group, Inc., and (iv) Devnet Merger
Sub merged with and into Devnet L.L.C. ("Devnet"), with Devnet continuing as the
surviving corporation (the transactions described in clauses (i), (ii), (iii)
and (iv) being referred to as the "Transaction");

          B.  The Subsidiary entered into the following agreements
(collectively, the "Assigned Documents"): (i) Securities Purchase Agreement
dated as of May 7, 1999, by and among the Subsidiary and the Purchasers named
therein; (ii) Stockholders Agreement dated as of May 7, 1999 (the "Stockholders
Agreement"), by and among the Subsidiary and the Stockholders named therein;
(iii) Registration Rights Agreement dated as of May 7, 1999, by and among the
Company and the Stockholders named therein; (iv) Securities Purchase Agreement
dated as of June 30, 2000, between the Subsidiary and Nortel Networks, Inc.
("Nortel"); (v) Registration Rights Agreement dated as of June 30, 2000, between
the Subsidiary and Nortel; (vi) Amendment dated as of June 30, 2000, among the
Subsidiary, Nortel and Signal Equity Partners, L.P., as the Majority in Interest
of the Purchasers ("Signal"), to the Stockholders Agreement; (vii) Securities
Purchase Agreement dated as of July 28, 2000, between the Subsidiary and Nortel;
and (viii) Second Amendment dated as of July 28, 2000, among the Subsidiary,
Nortel and Signal, to the Stockholders Agreement; and

          C.   In connection with the Transaction, the Subsidiary desires to
assign, and the Parent desires to assume, all of the Subsidiary's rights and
obligations under each of the Assigned Documents.
<PAGE>

                                   AGREEMENT
                                   ---------

          NOW, THEREFORE, in consideration of the promises and the mutual
agreements herein contained and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto,
intending to be legally bound, agree as follows:

                                   ARTICLE I

                           ASSIGNMENT AND ASSUMPTION
                           -------------------------

     Section 1.1.  Assignment and Assumption.   The Subsidiary hereby assigns to
the Parent, and the Parent hereby assumes and agrees to pay, discharge and
perform, as and when due, all of the liabilities, obligations and rights of the
Subsidiary under each of the Assigned Documents.

     Section 1.2.  Consent and Acceptance. Nortel and Signal hereby acknowledge
and consent to the assignment and assumption of the Assigned Documents described
in Recital B above.

     Section 1.3.  Successors and Assigns. This Agreement shall bind and inure
to the benefit of the respective parties and their assigns, transferees and
successors.

                                   ARTICLE II

                                    COVENANT
                                    --------

     The stock certificate representing the shares of Series H Preferred Stock,
par value $.001 per share, which were issued to Nortel by the Subsidiary on July
31, 2000, shall for all purposes be considered a stock certificate representing
shares of Series H Preferred Stock, par value $.001 per share, of the Parent as
a result of the conversion of such shares pursuant to the Merger Agreement in
connection with the Transaction.

                                  ARTICLE III

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

     Section 3.1.  Governing Law.   This Agreement shall be governed by, and
shall be construed and enforced in accordance with, the internal laws of the
State of New York, without regard to conflicts of laws principles (other than
Sections 5-1401 and 5-1402 of the General Obligations Law of the State of New
York).

     Section 3.2.  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 instruments.
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                            (Signature page follows)
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          IN WITNESS WHEREOF, each of the Parent and the Subsidiary has executed
this Assignment and Assumption Agreement as of the 11th day of August, 2000.

                              FIBERNET TELECOM GROUP, INC.,
                              as the Parent

                              By: /s/ Michael S. Liss
                                 --------------------------------------
                                Name:  Michael S. Liss
                                Title: President and Chief Executive
                                        Officer

                              FIBERNET OPERATIONS, INC.,
                              as the Subsidiary

                              By: /s/ Michael S. Liss
                                 --------------------------------------
                                Name:  Michael S. Liss
                                Title: President and Chief Executive
                                        Officer

Accepted and acknowledged
this 11th day of August, 2000:

NORTEL NETWORKS INC.

By: /s/ Robert D. Beiter
   --------------------------
   Name:  Robert D. Beiter
   Title: Director, Customer Finance

SIGNAL EQUITY PARTNERS, L.P.,
as Majority in Interest

By: /s/ Timothy P. Bradley
   --------------------------
   Name:  Timothy P. Bradley
   Title: Managing Partner

                                      S-1<PAGE>

                                                                     EXHIBIT 4.1

                NOT VALID UNLESS COUNTERSIGNED BY TRANSFER AGENT
             INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

NUMBER                                   SHARES
2812

                                    CUSIP NO. 315653 10 5

                         FiberNet Telecom Group, Inc.
AUTHORIZED COMMON STOCK:  150,000,000 SHARES
  PAR VALUE:$.001

THIS CERTIFIES THAT

IS THE RECORD HOLDER OF

              Shares of FIBERNET TELECOM GROUP, INC. Common Stock

transferable on the books of the Corporation in person or by duly authorized
attorney upon surrender of this Certificate properly endorsed.  This Certificate
is not valid until countersigned by the Transfer Agent and registered by the
Registrar.

Witness the facsimile seal of the Corporation and the facsimile signatures of
its duly authorized officers.

Dated:

[SEAL]

/s/ Roy D. Farmer III                         /s/ Michael S. Liss
----------------------------                  ----------------------------
      Secretary                                   President

NOTICE:  Signature must be guaranteed by a firm which is a member of a
   registered national stock exchange, or by a bank (other than a saving bank),
   or a trust company. The following abbreviations, when used in the
   inscription on the face of this certificate, shall be construed as though
   they were written out in full according to applicable laws or regulations.

TEN COM - as tenants in common           UNIF GIFT MIN ACT ......Custodian....
TEN ENT - as tenants by the entireties        (Cust)              (Minor)
JT TEN - as joint tenants with right of    Under Uniform Guide to Minors
       survivorship and not as tenants   Act..................................
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            in common                       (State)

    Additional abbreviations may also be sued though not in the above list.

For Value Received, ___________ hereby sell, assign and transfer unto

                    PLEASE INSERT SOCIAL SECURITY OR OTHER
                        IDENTIFYING NUMBER OF ASSIGNEE

                          ___________________________
                         |___________________________|

 ------------------------------------------------------------------------------
 (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)

---------------------------

---------------------------
                            Shares
---------------------------

of the capital stock represented by the within certificate, and do hereby
irrevocably constitute and appoint

                          Attorney
--------------------------

to transfer the said stock on the books of the within named Corporation with
full power of substitution in the premises.

Dated:
     ------------------------

-----------------------
NOTICE:  THE SIGNATURE TO THIS ASSIGNMENT MUST BE CORRESPOND WITH THE NAME AS
   WRITTEN UPON THE FACE OF CERTIFICATE IN EVERY PARTICULAR WITHOUT ALTERATION
   OR ENLARGEMENT OR ANY CHANGE WHATEVER

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