Document:

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                                                                     EXHIBIT 4.1

                                    AMENDMENT ("Amendment") dated as of August
                              11, 2000 between FIBERNET TELECOM GROUP, INC.
                              ("Company"), SIGNAL EQUITY PARTNERS, L.P.
                              (formerly known as Signal Capital Partners, L.P.),
                              as the Majority in Interest of the Purchasers
                              ("Signal"), and NORTEL NETWORKS INC. ("Nortel")
                              (each term as defined herein), to the Stockholders
                              Agreement dated as of May 7, 1999 (as amended by
                              the Amendment dated as of June 30, 2000, and as
                              further amended by the Amendment dated as of July
                              28, 2000, the "Stockholders Agreement") by and
                              among the Company and the Stockholders (as defined
                              in the Stockholders Agreement) listed therein
                              ("Stockholders").

             WHEREAS, pursuant to Section 17 of the Stockholders Agreement, the
Company, Nortel and Signal, as the Majority in Interest, have the right to
modify the Stockholders Agreement; and

             WHEREAS, the Company, Nortel and Signal, as the Majority in
Interest, wish to amend the Stockholders Agreement.

             NOW, THEREFORE, the parties agree as follows:

     Section 1.  Definitions.  Capitalized terms used and not otherwise defined
herein shall have the meanings ascribed to such terms in the Stockholders
Agreement.

     Section 2.  Agreement to Amend.  Pursuant to Section 17 of the Stockholders
Agreement, the Company, Nortel and Signal hereby agree to amend the Stockholders
Agreement as provided herein.

     Section 3.  Amendments.

             (a) Section 1 (Definitions) of the Stockholders Agreement shall be
amended as follows:

                 (i) The definition of the term "Stock" shall be amended and
restated in its entirety as follows:

                    "Stock" shall mean (i) the presently issued and outstanding
               shares of Common Stock, Series C Preferred Stock, Series D
               Preferred Stock, Series E Preferred Stock, Series F Preferred
               Stock, Series H Preferred Stock and Series I Preferred Stock, and
               any options, warrants or other instruments exercisable therefor
               (which options, warrants or other
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               instruments shall be deemed to be that number of outstanding
               shares of Stock for which they are exercisable), (ii) any
               additional shares of capital stock of the Company hereafter
               issued and outstanding and (iii) any shares of capital stock of
               the Company into which such shares may be converted or for which
               they may be exchanged or exercised.

                (ii) The following definition shall be added:

                    "Series I Preferred Stock" shall mean the Series I
                Convertible Preferred Stock, par value $.001, of the Company.

             (b)  New subsection (f)(viii) shall be added to Section 7
(Pre-emptive Rights) of the Stockholders Agreement as follows:

                "(viii) 62,500 shares of Series I Preferred Stock issued or to
          be issued to Nortel Networks Inc. (and shares of Common Stock to be
          issued upon conversion thereof)."

     Section 4.  Governing Law.  This Amendment shall be governed by and
construed in accordance with the laws of the State of New York (without regard
to principles of conflicts of laws).

     Section 5.  Successors and Assigns.  This Amendment shall bind and inure to
the benefit of the parties and their respective successors and assigns,
transferees, legal representatives and heirs.

     Section 6.  Headings.  The headings of this Amendment have been inserted
for convenience of reference only and shall not be deemed to be a part of this
Amendment.

     Section 7.  Entire Agreement.  This Amendment, the Stockholders Agreement
and the other writings referred to herein or delivered pursuant hereto contain
the entire agreement among the parties hereto with respect to the subject matter
hereof and supersede all prior and contemporaneous agreements and understandings
with respect thereto.

     Section 8.  Counterparts.  This Amendment may be executed in any number of
counterparts, and each such counterpart shall be deemed to be an original
instrument, but all such counterparts together shall constitute but one
agreement.

                                   * * * * *
<PAGE>

     IN WITNESS WHEREOF, the parties have executed this Amendment as of the date
first written above.

                              FIBERNET TELECOM GROUP, INC.

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

                              SIGNAL EQUITY PARTNERS, L.P.

                              By: Signal Equity Advisors, L.P.
                              Its: General Partner

                              By: Signal Equity Advisors, Inc.
                              Its: General Partner

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

                              NORTEL NETWORKS INC.

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

                                                                    Exhibit 10.1

SECURITIES PURCHASE AGREEMENT dated as of August 11, 2000 (the "Agreement") by
and among FIBERNET TELECOM GROUP, INC., a Delaware corporation (the "Company"),
and Nortel Networks Inc., a Delaware corporation, and any successors or assigns
thereto (the "Purchaser").

                                    PREAMBLE

          The Company wishes to sell and issue to the Purchaser shares of its
Series I Preferred Stock (as defined below), and the Purchaser desires to
purchase and accept such Preferred Stock, all upon and subject to the terms and
conditions hereof.

          NOW THEREFORE, the parties to this Agreement hereby agree as follows:

ARTICLE I
                                  DEFINITIONS

1.1       Defined Terms.  Capitalized terms used in this Agreement and not
otherwise defined herein shall have the meanings assigned thereto in the
Certificate of Designation.  As used in this Agreement, the following terms
shall have the following respective meanings:

          "Act" shall mean the Securities Act of 1933, together with any
applicable regulations, as the same may be amended from time to time.

          "Affiliate", as applied to any Person, means any other Person directly
or indirectly controlling, controlled by, or under direct or indirect common
control with, that Person.  For the purposes of this definition, "control"
(including, with correlative meanings, the terms "controlling", "controlled by"
and "under common control with"), as applied to any Person, means the
possession, directly or indirectly, of the power to direct or cause the
direction of the management and policies of that Person, whether through the
ownership of voting securities or by contract or otherwise.

          "Agreement" shall have the meaning given to such term in the caption.

          "Applicable Law" shall mean, with respect to any Person, property,
transaction or event, all present and future applicable laws, statutes,
regulations, treaties, judgments and decrees and all applicable official
directives, rules, consents, approvals, authorizations, orders, guidelines and
policies of any Governmental Authority or Persons having authority over or
applicable to such Person or any of its assets or properties.

          "Assignment" shall mean the Assignment and Assumption Agreement dated
as of the date hereof, by and among FiberNet Telecom Group, Inc., FiberNet
Operations, Inc., Nortel Networks Inc. and Signal Equity Partners, L.P., as
Majority in Interest.

          "Business Day" shall mean any day other than a Saturday, Sunday or a
day on which banks are authorized or required to be closed in New York, New
York.

          "Certificate of Designation" shall mean the Certificate of Designation
of the Preferred Stock of the Company.

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          "Closing Date" shall mean August 11, 2000, or such other date as the
Purchaser and the Company shall agree.

          "Code" shall mean the Internal Revenue Service Code of 1986, as
amended, and the rules and regulations thereunder, as from time to time in
effect, or any successor thereto.

          "Common Stock" means the common stock, par value $.001 per share, of
the Company.

          "Company" shall have the meaning given to such term in the caption.

          "Control" shall mean, with respect to any Person, the possession,
directly or indirectly, of the power to direct or cause the direction of the
management or policies of a Person, whether through the ownership of voting
securities, by contract or otherwise.

          "Environmental Claim" means any investigation, notice, notice of
violation, claim, action, suit, proceeding, demand, abatement order or other
order or directive (conditional or otherwise), by any Governmental Authority or
any other Person, arising (i) pursuant to or in connection with any actual or
alleged violation of any Environmental Law, (ii) in connection with any
Hazardous Materials or any actual or alleged Hazardous Materials Activity, or
(iii) in connection with any actual or alleged damage, injury, threat or harm to
health, safety, natural resources or the environment.

          "Environmental Laws" means any and all current or future statutes,
ordinances, orders, rules, regulations, guidance documents, judgments,
Governmental Actions, or any other requirements of governmental authorities
relating to (i) environmental matters, including those relating to any Hazardous
Materials Activity, (ii) the generation, use, storage, transportation or
disposal of Hazardous Materials, or (iii) occupational safety and health,
industrial hygiene, land use or the protection of human, plant or animal health
or welfare, in any manner applicable to the Company or any of its Subsidiaries
or any Facility, including the Comprehensive Environmental Response,
Compensation, and Liability Act (42 U.S.C. (S) 9601 et seq.), the Hazardous
Materials Transportation Act (49 U.S.C. (S) 1801 et seq.), the Resource
Conservation and Recovery Act (42 U.S.C. (S) 6901 et seq.), the Federal Water
Pollution Control Act (33 U.S.C. (S) 1251 et seq.), the Clean Air Act (42 U.S.C.
(S) 7401 et seq.), the Toxic Substances Control Act (15 U.S.C. (S) 2601 et
seq.), the Federal Insecticide, Fungicide and Rodenticide Act (7 U.S.C. (S)136
et seq.), the Occupational Safety and Health Act (29 U.S.C. (S) 651 et seq.),
the Oil Pollution Act (33 U.S.C. (S) 2701 et seq.) and the Emergency Planning
and Community Right-to-Know Act (42 U.S.C. (S) 11001 et seq.), each as amended
or supplemented, any analogous present or future state or local statutes or
laws, and any regulations promulgated pursuant to any of the foregoing.

          "ERISA" means the Employee Retirement Income Security Act of 1974, 29
U.S.C. (S)(S) 1000 et seq., amendments thereto, successor statutes, and
regulations or guidance promulgated thereunder.

          "ERISA Affiliate" means, as applied to any Person, (i) any corporation
which is a member of a controlled group of corporations within the meaning of
Section 414(b) of the Code of which that Person is a member; (ii) any trade or
business (whether or not incorporated) which

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is a member of a group of trades or businesses under common control within the
meaning of Section 414(c) of the Code of which that Person is a member; and
(iii) any member of an affiliated service group within the meaning of Section
414(m) or (o) of the Code of which that Person, any corporation described in
clause (i) above or any trade or business described in clause (ii) above is a
member. Any former ERISA Affiliate of the Company or any of its Subsidiaries
shall continue to be considered an ERISA Affiliate of the Company or such
Subsidiary within the meaning of this definition with respect to the period such
entity was an ERISA Affiliate of the Company or such Subsidiary and with respect
to liabilities arising after such period for which the Company or such
Subsidiary could be liable under the Code or ERISA.

          "Exchange Act" shall mean the Securities Exchange of 1934, together
with any applicable regulations, as the same may be amended from time to time.

          "Facilities" means any and all real property (including all buildings,
fixtures or other improvements located thereon) now, hereafter or heretofore
owned, leased, operated or used by the Company or any of its Subsidiaries or any
of their respective predecessors or Affiliates.

          "Financial Officer" of any Person shall mean its chief financial
officer or principal accounting officer.

          "Fiscal Year" shall mean, with respect to the Company, the one-year
period ending on December 31 of any year.

          "Governmental Action" means all permits, authorizations,
registrations, consents, approvals, determinations, decrees, waivers,
privileges, certifications, environmental clearances, notices and licenses of
any Governmental Authority.

          "Governmental Authority" shall mean Congress, any legislature,
assembly, council or other legislative body and any federal, state, municipal or
other governmental department, commission, board, bureau, agency or
instrumentality, or any court or any judicial or quasi-judicial body or
authority, in each case whether of or involving the United States of America or
any political subdivision thereof.

          "Hazardous Materials" means (i) any chemical, material or substance at
any time defined as or included in the definition of "hazardous substances,"
"hazardous wastes," "hazardous materials," "extremely hazardous waste," "acutely
hazardous waste," "radioactive waste," "biohazardous waste," "pollutant," "toxic
pollutant," "contaminant," "restricted hazardous waste," "infectious waste,"
"toxic substances," or any other term or expression intended to define, list or
classify substances by reason of properties harmful to health, safety or the
indoor or outdoor environment (including harmful properties such as
ignitability, corrosivity, reactivity, carcinogenicity, toxicity, reproductive
toxicity, "TCLP toxicity" or "EP toxicity" or words of similar import under any
applicable Environmental Laws); (ii) any oil, petroleum, petroleum fraction or
petroleum derived substance; (iii) any drilling fluids, produced waters and
other wastes associated with the exploration, development or production of crude
oil, natural gas or geothermal resources; (iv) any flammable substances or
explosives; (v) any radioactive materials; (vi) any asbestos-containing
materials; (vii) urea formaldehyde foam insulation; (viii)

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electrical equipment which contains any oil or dielectric fluid containing
polychlorinated biphenyls; (ix) pesticides; and (x) any other chemical, material
or substance, exposure to which is prohibited, limited or regulated by any
governmental authority or which may or could pose a hazard to the health and
safety of the owners, occupants or any Persons in the vicinity of any Facility
or to the indoor or outdoor environment.

          "Hazardous Materials Activity" means any past, current, proposed or
threatened activity, event or occurrence involving any Hazardous Materials,
including the use, manufacture, possession, storage, holding, presence,
existence, location, Release, threatened Release, discharge, placement,
generation, transportation, processing, construction, treatment, abatement,
removal, remediation, disposal, disposition or handling of any Hazardous
Materials, and any corrective action or response action with respect thereto.

          "Intellectual Property" means all patents, trademarks, tradenames,
copyrights, technology, know-how and processes used in or necessary for the
conduct of the business of the Company or any of its Subsidiaries that are
material to the condition (financial or otherwise), business or operations of
the Company or any of its Subsidiaries.

          "Intellectual Property Rights" means all industrial and intellectual
property rights, including, without limitation, patents, patent applications,
patent rights, trademarks, trademark applications, trade names, service marks,
service mark applications, copyright, copyright applications, know how, trade
secrets, proprietary processes and formulae, confidential information,
franchises, licenses, inventions, instructions, marketing materials, trade
dress, logos and designs, and all documentation and media constituting,
describing or relating to the foregoing, including, without limitation, manuals,
memoranda and records.

          "Judgments" shall mean all judgments, injunctions, orders and decrees
of all courts and arbitrators in proceedings or actions in which the Person in
question is a party or by which any of its assets or properties is bound.

          "Legal Requirements" means all laws, statutes, orders, decrees,
injunctions, licenses, permits, approvals, authorizations, agreements and
regulations of any Governmental Authority having jurisdiction over the matter in
question.

          "Lien" shall mean any security interest, pledge, bailment, mortgage,
deed of trust, the grant of a power to confess judgment, conditional sale or
title retention agreement, charge, encumbrance, easement, reservation,
preemptive right, restriction, cloud, right of first refusal or first offer,
option, or other similar arrangement or interest in real or personal property,
other than (i) liens arising by operation of law in the ordinary course of
business that, individually and in the aggregate, do not in any material respect
interfere with the use of any of the assets subject thereto, (ii) minor
imperfections of title which do not materially detract from the value of the
property affected or materially impair the operations of the Company and (iii)
liens for taxes not yet due and payable.

          "Material Adverse Effect" shall mean (i) a material adverse effect on
the business, assets, liabilities, operations, results of operations or
condition (financial or otherwise) of the

                                       4
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Company or (ii) any impairment of the ability of the Company to perform any of
its material obligations under any Transaction Document to which it is a party.

          "Material Contract" means any contract, lease or other agreement or
arrangement to which the Company or any Subsidiary is a party (other than the
Transaction Documents) (i) involving aggregate consideration payable to or by
the Company or any Subsidiary in excess of $5,000,000, or (ii) which is
otherwise material to the business, assets, operations, results of operations or
condition (financial or otherwise) of the Company or any of its Subsidiaries,
and without limiting the foregoing, shall be deemed to include each of the
agreements or arrangements set forth in Schedule 3.12(b) to this Agreement.

          "Multiemployer Plan" means a "multiemployer plan" (as defined in
Section 4001(a)(3) of ERISA) to which the Company or any of its Subsidiaries or
any ERISA Affiliate has contributed within the past six years or with respect to
which the Company or any of its Subsidiaries may incur any liability.

          "Organizational Document" shall mean, with respect to any Person, each
instrument or other document that (i) defines the existence of such Person,
including its articles or certificate of incorporation or organization, as filed
or recorded with an applicable Governmental Authority, or (ii) governs the
internal affairs of such Person, including its by-laws, in each case as amended,
supplemented or restated.

          "Permitted Liens" means the following types of Liens, excluding (a)
any such Lien imposed pursuant to Section 401(a)(29) or 412(n) of the Code or by
ERISA, and (b) any such Lien relating to or imposed in connection with any
Environmental Claim:

(i) Liens for taxes, assessments or governmental charges or claims not yet due
or payable;

(ii) Liens deemed to exist in connection with repurchase agreements;

(iii) Liens of sellers of goods to the Company or any Subsidiary arising under
Article 2 of the UCC or similar provisions of applicable law in the ordinary
course of business, covering only goods sold and securing only the unpaid
purchase price for such goods and related expenses;

(iv) statutory Liens of landlords, statutory Liens of banks and rights of set-
off, statutory Liens of carriers, warehousemen, mechanics, repairmen, workmen
and materialmen, and other Liens imposed by law, in each case incurred in the
ordinary course of business (a) for amounts not yet overdue or (b) for amounts
that are overdue and that (in the case of any such amounts overdue for a period
in excess of five days) are being contested in good faith by appropriate
proceedings, so long as the Company maintains cash reserves sufficient to
discharge any such Lien;

(v) Liens incurred or deposits made in the ordinary course of business in
connection with workers' compensation, unemployment insurance and other types of
social security (exclusive of obligations for the payment of borrowed money),
incurred in the ordinary course of business (a) for amounts not yet overdue or
(b) for amounts that are overdue and that (in the case of any such amounts
overdue for a period in excess of five days) are being contested in good faith
by

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appropriate proceedings, so long as the Company maintains cash reserves
sufficient to discharge any such Lien;

(vi) leases or subleases granted to third parties, provided, that each such
lease or sublease (a) is in the ordinary course of business and is in connection
with the provision of co-location services by the Company or any of its
Subsidiaries and (b) does not interfere in any material respect with the
ordinary conduct of the business of the Company or any of its Subsidiaries;

(vii) easements, rights-of-way, restrictions, encroachments, and other minor
defects or irregularities in title, in each case which do not and will not
interfere in any material respect with the ordinary conduct of the business of
the Company or any of its Subsidiaries;

(viii) any zoning or similar law or right reserved to or vested in any
governmental office or agency to control or regulate the use of any real
property; and

(ix) interests of landlords or any of their respective lenders in leases or co-
location agreements entered into by the Company or any of its Subsidiaries.

          "Person" shall be construed broadly and shall include any natural
person, company, partnership, joint venture, corporation, business trust,
unincorporated organization or Governmental Authority.

          "Qualified Public Offering"  shall mean a fully underwritten public
offering (underwritten by an underwriter of national reputation) of shares of
Common Stock registered pursuant to the Securities Act with proceeds to the
Company of at least $75,000,000 (net of underwriting discounts and expenses).

          "Release" means any release, spill, emission, leaking, pumping,
pouring, injection, escaping, deposit, disposal, discharge, dispersal, dumping,
leaching or migration of Hazardous Materials into the indoor or outdoor
environment (including the abandonment or disposal of any barrels, containers or
other closed receptacles containing any Hazardous Materials), including the
movement of any Hazardous Materials through the air, soil, surface water or
groundwater.

          "Responsible Officer" of any Person shall mean the Chief Executive
Officer or a Financial Officer of such Person.

          "SEC" means the Securities and Exchange Commission.

          "Solvent" or "Solvency" means, with respect to any Person as of a
particular date, that on such date (i) such Person is able to realize upon its
assets and pay its debts and other liabilities, contingent obligations and other
commitments as they mature in the normal course of business, (ii) such Person
does not intend to, and does not believe that it will, incur debts or
liabilities beyond such Person's ability to pay as such debts and liabilities
mature in their ordinary course, (iii) such Person is not engaged in a business
or a transaction, and is not about to engage in a business or a transaction, for
which such Person's property or assets would constitute unreasonably small
capital after giving due consideration to the prevailing practice in the

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industry in which such Person is engaged or is to engage, (iv) the fair value of
the property or assets of such Person is greater than the total amount of
liabilities, including contingent liabilities, of such Person and (v) the
present fair salable value of the assets of such Person, as a going concern, is
not less than the amount that will be required to pay the probable liability of
such Person on its debts as they become absolute and matured.  In computing the
amount of contingent liabilities at any time, it is intended that such
liabilities will be computed at the amount which, in light of all the facts and
circumstances existing at such time, represents the amount that can reasonably
be expected to become an actual or matured liability.

          "Stockholders Agreement" shall mean the Stockholders Agreement dated
as of  May 7, 1999, as amended on June 30, 2000, and as further amended on July
28, 2000, by and among the Company and the stockholders named therein, as
amended from time to time.

          "Subsidiary" shall mean any corporation, partnership, joint venture or
other legal entity in which the Company owns, directly or indirectly, a majority
equity interest.

          "Transaction Documents" shall mean this Agreement, the Certificate of
Designation and the Assignment.

          "UCC" means the Uniform Commercial Code (or any similar or equivalent
legislation) as in effect in any applicable jurisdiction.

1.2  TERMS GENERALLY.

     The definitions in Section 1.1 shall apply equally to the singular and
plural forms of the terms defined.  Whenever the context may require, any
pronoun shall include the corresponding masculine, feminine and neuter forms.
The words "include", "includes" and "including" shall be deemed to be followed
by the phrase "without limitation".

1.3  CROSS-REFERENCES.

     Unless otherwise specified, references in this Agreement or any Transaction
Document to any Article or Section are references to such Article or Section of
this Agreement or such Transaction Document, as the case may be, and references
in any Article, Section or definition to any clause are references to such
clause of such Section, Article or definition.

1.4  ACCOUNTING TERMS; GAAP.

     Except as otherwise expressly provided herein, all terms of an accounting
or financial nature shall be construed in accordance with generally accepted
accounting principles ("GAAP"), consistently applied, and all financial
statements or accounting determinations required herein to be prepared or made
in accordance with GAAP shall be prepared or made in accordance with GAAP
applied on a consistent basis.

                                  ARTICLE II
                        ISSUANCE OF THE PREFERRED STOCK

2.1  ISSUANCE OF PREFERRED STOCK.

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     Subject to the terms and conditions contained herein, at the Closing (as
hereinafter defined), the Company has authorized the issuance of 62,500 shares
of Series I Preferred Stock, $.001 par value (the "Preferred Stock"), of the
Company for a purchase price of $120.00  per share (the "Purchase Price Per
Share") or $7,500,000 in the aggregate (the "Preferred Stock Purchase Price").
The Preferred Stock Purchase Price shall be delivered by the Purchaser to the
Company by wire transfer of immediately available funds.

2.2  AGREEMENT TO SELL PREFERRED STOCK.

     At the Closing, the Company shall sell to the Purchaser, and the Purchaser
shall purchase from the Company 62,500 shares of Preferred Stock for the
Preferred Stock Purchase Price.

2.3  DELIVERY OF PREFERRED STOCK.

        (a)  At the Closing, the Company shall deliver to the Purchaser the
     stock certificate for the Preferred Stock to be purchased by the Purchaser
     (with such certificate registered in the name of the Purchaser), duly
     executed by the Company.

        (b)  Delivery shall be made against receipt by the Company of the
     Preferred Stock Purchase Price by wire transfer of immediately available
     funds.

2.4  THE CLOSING.

     The closing hereunder with respect to the issuance, sale and delivery of
62,500 shares of Preferred Stock (the "Closing") will take place at the offices
of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., Chrysler Center, 666
Third Avenue, 25th Floor, New York, New York  10017, simultaneously with the
execution and delivery of this Agreement.

                                  ARTICLE III
                   REPRESENTATIONS AND WARRANTIES OF COMPANY

          The Company represents and warrants to the Purchaser as of the date
hereof as set forth below.

3.1  ORGANIZATION, ETC.

     The Company and its Subsidiaries are corporations duly organized, validly
existing and in good standing under the laws of the State of Delaware. The
Company and its Subsidiaries have all requisite power and authority and have all
governmental licenses, approvals, consents and authorizations necessary to own
or lease their respective property and assets and to carry on their business as
currently conducted and are qualified to do business in each jurisdiction in
which the failure to so qualify or be in good standing would have a Material
Adverse Effect on the Company and its Subsidiaries.

3.2  CORPORATE POWER AND AUTHORITY; NO REQUIRED CONSENTS OR APPROVALS.

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        (a)  The Company has the power to execute, deliver and perform its
     obligations under each Transaction Document to which it is a party and to
     issue and sell the Preferred Stock hereunder and to deliver the Preferred
     Stock to the Purchaser.

        (b)  The execution, delivery and performance by the Company of each
     Transaction Document to which it is a party, including the issuance of
     Preferred Stock by the Company, have been duly authorized by all required
     corporate and stockholder action of the Company and will not (i) violate
     any provision of Applicable Law, any Judgment or any Organizational
     Document of the Company or any of its Subsidiaries, (ii) conflict with,
     result in a breach of or constitute (alone or with notice or lapse of time
     or both) a default (or give rise to any right of termination, modification,
     cancellation or acceleration) under any contract to which the Company or
     any of its Subsidiaries are party or (iii) result in the creation or
     imposition of any Lien upon any property of the Company or any of its
     Subsidiaries.

        (c)  Except as set forth on SCHEDULE 3.2, no filing with or consent or
     approval of, or other action by, any Governmental Authority or other Person
     is or will be required by any Applicable Law or agreement in connection
     with the execution, delivery and performance by the Company of any
     Transaction Document to which it is a party.

3.3  ENFORCEABILITY.

     Each Transaction Document to which the Company is a party has been duly
executed and delivered by the Company, and constitutes the legal, valid and
binding obligation of the Company, enforceable in accordance with its terms,
except as enforceability thereof may be limited by any applicable bankruptcy,
reorganization, insolvency or other Applicable Law affecting creditors' rights
generally or by general principles of equity.

3.4  REPORTS.

     The Company has timely filed the reports and schedules set forth in
SCHEDULE 3.4 with the SEC pursuant to the Exchange Act and the regulations
promulgated thereunder.  Such reports (collectively, the "SEC Reports") were
prepared in accordance, and complied as of their respective dates in all
material respects, with the requirements of the Exchange Act and the regulations
promulgated thereunder and did not as of their respective filing dates (or if
amended by a filing prior to the date hereof, then as of the date of such
amendment) contain any untrue statement of a material fact or omit to state a
material fact required to be stated therein or necessary in order to make the
statements therein, in the light of the circumstances under which they were
made, not misleading, except to the extent superseded by a SEC Report filed
subsequently and prior to the date hereof.  The financial statements (including
any related notes) of the Company included in the SEC Reports complied in all
material respects with applicable accounting requirements and all applicable
laws, were prepared in conformity with GAAP applied on a consistent basis
(except as otherwise stated in the financial statements) and present fairly the
consolidated financial position, results of operations, stockholders' equity,
liabilities (contingent or otherwise) and cash flows, as the case may be, of the
Company and its Subsidiaries as of the dates and for the period indicated,
subject, in the case of unaudited interim financial statements to: (i) the
absence of certain notes thereto; and (ii) normal year-end audit adjustments.

                                       9
<PAGE>

3.5  SECURITIES LAWS.

     The offering, sale and purchase of the Preferred Stock contemplated hereby
are exempt from registration under the Securities Act.  The issuance of all
other shares of capital stock of the Company on or before the date hereto has
been made in compliance with the Securities Act and all applicable state
securities or blue sky laws.

3.6  CAPITALIZATION AND ISSUANCE.

        (a)  The authorized capital stock of the Company as of the date hereof
     is 170,000,000 shares, consisting of (i) 150,000,000 shares of Common
     Stock; and (ii) 20,000,000 shares of Preferred Stock, of which (A) 133,333
     shares have been designated Series C Preferred Stock, (B) 500,000 shares
     have been designated Series D Preferred Stock; (C) 750,000 shares have been
     designated Series E Preferred Stock; (D) 500,000 shares have been
     designated Series F Preferred Stock; and (E) 750,000 shares have been
     designated Series H Preferred Stock. As of August 11, 2000, there were (i)
     32,084,650 shares of Common Stock issued and outstanding; (ii) (A) 83,688
     shares of Series C Preferred Stock issued and outstanding; (B) 316,376
     shares of Series D Preferred Stock issued and outstanding; (C) 305,627
     shares of Series E Preferred Stock issued and outstanding; (D) 361,731
     shares of Series F Preferred Stock issued and outstanding; and (E) 426,333
     shares of Series H Preferred Stock outstanding; (iii) 10,000,000 shares of
     Common Stock reserved for issuance upon exercise of stock options of the
     Company outstanding or which may be granted pursuant to employee stock
     option and similar plans; (iv) 14,809,358 shares of Common Stock reserved
     for issuance upon the conversion of Preferred Stock; and (v) 10,589,791
     shares of Common Stock reserved for issuance upon the exercise of warrants
     outstanding. Except as set forth on SCHEDULE 3.6, all issued and
     outstanding shares of capital stock of the Company are duly authorized and
     validly issued, fully paid, nonassessable, free and clear of all Liens, and
     such shares were issued in compliance with all applicable state, provincial
     and federal laws concerning the issuance of securities. SCHEDULE 3.6
     contains a list of all management stockholders and all stockholders who, to
     the Company's knowledge, own (i) preferred stock of the Company or (ii) in
     excess of five percent (5%) of the Common Stock of the Company on a fully
     diluted basis. No shares of the capital stock of the Company other than
     those described above, are issued and outstanding. Except as set forth on
     SCHEDULE 3.6, there are no preemptive or other outstanding rights, options,
     warrants, conversion rights or similar agreements or understandings for the
     purchase or acquisition from the Company of any shares of capital stock or
     other securities of the Company.

          (b) When the shares of Preferred Stock are issued and delivered to the
     Purchaser against payment therefor as provided in this Agreement, the
     Preferred Stock will be duly and validly issued, fully paid and
     nonassessable. Upon any conversion of a share of Preferred Stock in
     accordance with the terms thereof, the shares of Common Stock into which
     such share of Preferred Stock is converted will be duly and validly issued,
     fully paid and nonassessable. The form of certificate evidencing the
     Preferred Stock complies with all applicable requirements of Delaware law.

3.7  Solvency.

                                       10
<PAGE>

     Both before and after giving effect to the transactions contemplated by
this Agreement, the Company is and will be Solvent.

3.8  NO MATERIAL ADVERSE EFFECT.

     Since December 31, 1999, no development, event or change in respect of the
Company or any of its Subsidiaries and no development, event or change in
respect of the telecommunications market in which the Company or any of its
Subsidiaries is or will be conducting its business, has occurred that has caused
or evidences, either in any case or in the aggregate, a Material Adverse Effect.

3.9  TITLE TO PROPERTIES; LIENS; REAL PROPERTY; CONDITION; USE.

            (a)  Title to Properties; Liens.  The Company and each of its
Subsidiaries have (i) good marketable and insurable fee simple title to (in the
case of fee interests in real property), (ii) valid leasehold interests in (in
the case of leasehold interests in real or personal property), or (iii) good
title to (in the case of all other personal property), all of their respective
material properties and assets reflected in the most recent financial statements
delivered pursuant to this Agreement, except for assets disposed of since the
date of such financial statements in the ordinary course of business.  Except as
permitted by this Agreement and set forth on SCHEDULE 3.9(A), all such
properties and assets are held free and clear of Liens (other than Permitted
Liens).

          (b)  Real Property.  As of the Closing Date, SCHEDULE 3.9(B) contains
an accurate and complete list of (i) all material properties owned by the
Company or any of its Subsidiaries and (ii) all material leases, subleases or
assignments of leases (together with all amendments, modifications, supplements,
renewals or extensions of any thereof) affecting real estate or properties owned
or leased by the Company or any of its Subsidiaries regardless of whether the
Company or such Subsidiary is the landlord or tenant (whether directly or as an
assignee or successor in interest) under such lease, sublease or assignment.

          (c)  Condition; Use.  All of the material tangible properties and
assets of the Company and its Subsidiaries are in good operating condition an
repair, normal wear and tear excepted, and reasonably fit for their intended
use.  The Company and its subsidiaries enjoy peaceful and undisturbed possession
and use of its leasehold interests in any tangible properties or tangible
assets.

3.10  LITIGATION; ADVERSE FACTS.

     Except as set forth in SCHEDULE 3.10, there are no actions, suits,
proceedings, arbitrations or governmental investigations at law or in equity, or
before or by any arbitrator or Governmental Instrumentality, domestic or foreign
(including any Environmental Claims) that are pending or, to the knowledge of
the Company, threatened against or affecting the Company or any of its
Subsidiaries or any property of the Company or any of its Subsidiaries, which,
if adversely determined, could reasonably be expected to have a Material Adverse
Effect.  Neither the Company nor any of its Subsidiaries (i) is in violation of
any applicable Legal Requirement (including Environmental Laws) or (ii) is
subject to or in default with respect to any final

                                       11
<PAGE>

judgments, writs, injunctions, decrees, rules or regulations of any court or any
federal, state, municipal or other governmental department, commission, board,
bureau, agency or instrumentality, domestic or foreign, which, with respect to
any such violations or defaults occurring after the Closing Date, could
reasonably be expected to have a Material Adverse Effect.

3.11  PAYMENT OF TAXES.

     All tax returns and reports of the Company and each Subsidiary of the
Company required to be filed by any such Person have been timely filed, and all
taxes required to be paid with respect to such tax returns to be due and payable
and all material assessments, fees and other governmental charges upon the
Company and each Subsidiary of the Company and upon their respective properties,
assets, employees, income, businesses and franchises which are due and payable
have been paid when due and payable.  The Company knows of no proposed tax
assessment against the Company or any of its Subsidiaries which could reasonably
be expected to have a Material Adverse Effect that is not being actively
contested by the Company or such Subsidiary in good faith and by appropriate
proceedings and for which reserves or other appropriate provisions, if any, as
shall be required in conformity with GAAP shall not have been made or provided
therefor.

3.12  PERFORMANCE OF AGREEMENTS; MATERIAL CONTRACTS.

            (a) Neither the Company nor any of its Subsidiaries is in default in
the performance, observance or fulfillment of any of the material obligations,
covenants or conditions contained in any of its Material Contracts and no
condition exists that, with the giving of notice or the lapse of time or both,
would constitute such a default, or that would permit the counterparty to any
Material Contract to terminate the Material Contract to which it is a party.

            (b) SCHEDULE 3.12(B) contains an accurate and complete list of all
the Material Contracts in effect on the Closing Date.  Except as described on
Schedule 4.9.B, to the knowledge of the Company, all such Material Contracts are
in full force and effect and no defaults currently exist thereunder.  Any
description of the Material Contracts in the SEC Reports are accurate.

3.13  GOVERNMENTAL REGULATION.

     Neither the Company nor any of its Subsidiaries is subject to regulation
under the Public Utility Holding Company Act of 1935, the Federal Power Act, or
the Interstate Commerce Act, nor is an "investment company" as defined in the
Investment Company Act of 1940, or subject to regulation under the Investment
Company Act of 1940, or under any other federal or state statute or regulation
which may limit its ability to incur Indebtedness or which may otherwise render
all or any portion of the Transaction Documents unenforceable.

3.14  LABOR MATTERS.

     Except as disclosed and described in SCHEDULE 3.14, there are no collective
bargaining agreements or Multiemployer Plans covering the employees of the
Company as of the Closing

                                       12
<PAGE>

Date. The Company is not engaged in any unfair labor practice that could
reasonably be expected to have a Material Adverse Effect. There is no strike,
labor dispute, union organizing activity, slowdown or stoppage pending or, to
the best knowledge of the Company, threatened against the Company which,
individually or in the aggregate, could reasonably be expected to have a
Material Adverse Effect.

3.15  ENVIRONMENTAL PROTECTION.

     Except as set forth in SCHEDULE 3.15 annexed hereto:

     (i) neither the Company nor any of its Subsidiaries nor any of their
respective Facilities are subject to any outstanding written order, consent
decree or settlement agreement with any Person relating to (a) any Environmental
Law, (b) any Environmental Claim, or (c) any Hazardous Materials Activity;

     (ii) neither the Company nor any of its Subsidiaries has received any
letter or request for information under Section 104 of the Comprehensive
Environmental Response, Compensation, and Liability Act (42 U.S.C. (S) 9604) or
any comparable state law;

     (iii) there are and, to the Company's knowledge, have been, no conditions,
occurrences, or Hazardous Materials Activities on any Facility which could
reasonably be expected to form the basis of an Environmental Claim against the
Company or any of its Subsidiaries;

     (iv) neither the Company nor any of its Subsidiaries nor, to the Company's
knowledge, any predecessor of the Company or any of its Subsidiaries has filed
any notice under any Environmental Law indicating past or present treatment of
Hazardous Materials at any Facility, and none of the Company's or any of its
Subsidiaries' operations involves the generation, transportation, treatment,
storage or disposal of hazardous waste, as defined under 40 C.F.R. Parts 260-270
or any state equivalent; and

     (v) compliance with all current or reasonably foreseeable future
requirements pursuant to or under Environmental Laws could not, individually or
in the aggregate, reasonably be expected to give rise to a Material Adverse
Effect.

Notwithstanding anything in this Section 4.14. to the contrary, no event or
condition has occurred or is occurring with respect to the Company or any of its
Subsidiaries relating to any Environmental Law, any Release of Hazardous
Materials, or any Hazardous Materials Activity, including any matter disclosed
on SCHEDULE 3.15 annexed hereto, which individually or in the aggregate has had
or could reasonably be expected to have a Material Adverse Effect.

3.16 IMMUNITY.

     Neither the Company nor any of its Subsidiaries is entitled to claim for
itself or any of its assets immunity from suit, execution, attachment or other
legal process in any proceeding in any jurisdiction in connection with any of
the Transaction Documents to which it is a party.

                                       13
<PAGE>

3.17  ADDITIONAL MATTERS.

            (a) Disclosure.  The written factual information furnished by (or
based on written information furnished by) the Company to the Purchaser in
connection with the negotiation of the Transaction Documents (excluding any
financial projections and other estimates or views of future circumstances),
taken as a whole, does not contain, as of the Closing Date, any untrue
statements of material fact and does not omit to state, as of the Closing Date,
any material fact necessary in order to make the statements contained therein,
in light of the circumstances under which they were made, not materially
misleading (unless superseded or corrected and disclosed in writing to the
Purchaser prior to the Closing Date).

          (b) Licenses and Permits.  The Company has obtained and holds in full
force and effect, free from burdensome restrictions, all Governmental Actions,
franchises, leases, qualifications, easements, rights of way and other rights
and approvals which are necessary for the operation of its business as presently
conducted, except where the failure to obtain such rights and approvals,
individually and in the aggregate, could not be reasonably expected to have a
Material Adverse Effect.  The Company is not in violation of the terms or
conditions of any such Governmental Action, franchise, lease, qualification,
easement, right of way, right or approval, which violation could reasonably be
expected to have a Material Adverse Effect.

          (c) Intellectual Property.  The Company has obtained and holds in full
force and effect the Intellectual Property, free from burdensome restrictions,
which is necessary for the operation of its business as presently conducted
except for that Intellectual Property which the failure to own or license could
not reasonably expected to have a Material Adverse Effect.  No product, process,
method, substance, part or other material presently sold or employed by the
Company in connection with such business infringes any Intellectual Property
owned by any other Person, except as could not, individually and in the
aggregate, reasonably be expected to have a Material Adverse Effect.  All of the
material Intellectual Property owned or used by the Company as of the Closing
Date is set forth in SCHEDULE 3.17.

          (d) Year 2000.  Any reprogramming required to permit the proper
functioning, in and following the year 2000, of the Company's and each of its
Subsidiaries' computer systems and equipment containing embedded microchips
(including systems and equipment supplied by others or with which the Company's
or any of its Subsidiaries' systems interface) which the Company or any of its
Subsidiaries possesses as of the date this representation is made or deemed made
and the testing of all such systems and equipment, as so reprogrammed, was
completed by January 1, 2000.  The computer and management information systems
of the Company and each of its Subsidiaries are, and, with ordinary course
upgrading and maintenance, will continue to be, sufficient to permit the Company
and each of its Subsidiaries to conduct its business without causing a Material
Adverse Effect.

3.18  SUBSIDIARIES.

      All of the Subsidiaries of the Company are identified in SCHEDULE 3.18
annexed hereto.  The equity interests of each of the Subsidiaries of the Company
are identified in SCHEDULE 3.18 annexed hereto and such equity interests are
duly authorized, validly issued and fully paid and

                                       14
<PAGE>

nonassessable. Each of the Subsidiaries of the Company identified in SCHEDULE
3.18 annexed hereto is (i) a corporation or limited liability company duly
organized or formed, validly existing and in good standing under the laws of its
respective jurisdiction of organization set forth therein, has all requisite
corporate or limited liability company power and authority to own and operate
its properties and to carry on its business as now conducted and as proposed to
be conducted, and (ii) is qualified to do business and is in good standing in
the State of New York and in every other jurisdiction where its assets are
located and wherever necessary to carry out its business and operations, except
where the failure to be so qualified and in good standing could not reasonably
be expected to have a Material Adverse Effect. SCHEDULE 3.18 annexed hereto
completely and correctly sets forth the ownership of each Subsidiary of the
Company.

3.19      MERGER.

          The shares of Series H Preferred Stock, par value $.001 per share,
which were issued to the Purchaser by FiberNet Operations, Inc. (formerly known
as FiberNet Telecom Group, Inc.) on July 31, 2000 were converted into shares of
Series H Preferred Stock, par value $.001 per share, of FiberNet Telecom Group,
Inc. (formerly known as FiberNet Holdco, Inc.) pursuant to, and in connection
with the transactions contemplated by, the Agreement and Plan of Reorganization
dated as of June 2, 2000, by and among FiberNet Telecom Group, Inc., FiberNet
Holdco, Inc., FiberNet Merger Sub, Inc., Devnet Merger Sub, LLC, Devnet L.L.C.
and FP Enterprises L.L.C.

                                   ARTICLE IV
                  REPRESENTATIONS AND WARRANTIES OF PURCHASER

4.1  PURCHASER REPRESENTATIONS AND WARRANTIES.

     The Purchaser represents and warrants to the Company as follows:

        (a)   Such Purchaser is acquiring the Preferred Stock to be purchased by
it and the Common Stock  issuable upon conversion or exercise of such Preferred
Stock, for its own account, for investment and not with a view to the
distribution thereof, nor with any present intention of distributing the same.

        (b)  Such Purchaser understands that the Preferred Stock have not been,
and any other securities of the Company issuable upon conversion or exercise of
any Preferred Stock, will not be, registered under the Act, by reason of their
issuance in a transaction exempt from the registration requirements of the Act,
and that they must be held indefinitely unless a subsequent disposition thereof
is registered under the Act or is exempt from registration.

        (b)  Such Purchaser is an "accredited investor," as defined in Rule 501
(the provisions of which are known to such Purchaser) promulgated under the Act
and has been advised by individuals with such knowledge and experience in
financial and business matters as to be capable of evaluating the merits and
risks of its investment in the Company, has the ability to bear the economic
risks of its investment for an indefinite period of time, has been furnished

                                       15
<PAGE>

with and has had access to such information as reasonably requested and has had
the opportunity to ask, and has received satisfactory answers for, questions of
the Company.

4.2  AUTHORITY.

     Such Purchaser has all requisite power and authority to enter into the
Transaction Documents to which it is a party, to perform its obligations
thereunder, and to consummate the transactions contemplated thereby.  Such
Purchaser has not been organized, reorganized or recapitalized specifically for
the purpose of investing in the Company.

4.3  ENFORCEABILITY.

     Such Purchaser has taken all requisite action necessary to authorize its
execution and delivery of the Transaction Documents to which it is a party, its
performance of its obligations thereunder, and its consummation of the
transactions contemplated thereby.  Each Transaction Document has been executed
and delivered by an officer or duly authorized representative of Purchaser in
accordance with such authorization.  This Agreement constitutes and, upon their
execution and delivery, the other Transaction Documents to which it is a party
will constitute, valid and binding obligations of such Purchaser, enforceable in
accordance with their terms, subject to applicable bankruptcy, reorganization,
insolvency, and similar laws affecting creditors' rights generally and to
general principles of equity.

4.4  BROKERS AND FINDERS.

     No person or entity acting on behalf or under the authority of such
Purchaser is or will be entitled to any broker's, finder's, or similar fee or
commission in connection with the transactions contemplated hereby which would
become an obligation of the Company.

                                   ARTICLE V
                             DELIVERIES AT CLOSING

5.1  DELIVERIES ON THE CLOSING DATE.

     The Company and the Purchaser, as applicable, shall make the following
deliveries on the Closing Date:

        (a) Preferred Stock. Purchaser shall receive a certificate for its
respective shares of Preferred Stock from the Company in accordance with the
provisions of Section 2.3.

        (b) Charter Amendment.  The Company shall file and the Secretary of
State of Delaware shall accept a Certificate of Designation setting forth the
preferences, privileges, rights and powers of the Preferred Stock substantially
in the form of EXHIBIT A attached hereto.

        (c) Corporate Documents.  The Purchaser shall receive:

            (i)  a copy of the certificate of incorporation of the Company,
     including all amendments thereto, certified as of a recent date by an
     appropriate public official of the

                                       16
<PAGE>

     State of Delaware and a certificate as to the good standing or existence of
     the Company in the State of Delaware;

                (ii) a certificate of a Responsible Officer of the Company dated
     the Closing Date and certifying (A) a correct and complete copy of each
     Organizational Document of the Company as in effect on the Closing Date,
     (B) a correct and complete copy of resolutions duly adopted by the board of
     directors of the Company, authorizing the execution, delivery and
     performance of the Transaction Documents, the sale of the Preferred Stock
     hereunder and the other transactions contemplated hereby and thereby, (C)
     that the certificate of incorporation of the Company has not been amended
     since the date of the last amendment thereto shown on the certificate of
     good standing or existence furnished pursuant to clause (i) above, and (D)
     as to the incumbency and specimen signature of each officer of the Company
     who shall execute any Transaction Document or any other document delivered
     in connection herewith;

                (iii) a certificate of a Responsible Officer of the Company as
     to the incumbency and specimen signature of the Responsible Officer
     executing the certificate pursuant to clause (ii) above;

                (iv)  a certificate from the Secretary of State of each state in
     the United States of America in which the Company is required to be
     qualified to do business as a foreign corporation, certifying as to such
     qualification and the Company's good standing in such state.

         (d) Officer's Certificate.  Purchaser shall also receive an officer's
certificate from a Responsible Officer stating the following in substantially
similar form:

                (i)    the representations and warranties of the Company
     contained in this Agreement shall be true and correct in all material
     respects on and as of the Closing Date with the same effect as though such
     representations and warranties had been made on and as of the Closing Date;

                (ii)   each and all of the agreements and covenants of the
     Company to be performed on or before the Closing Date pursuant to the terms
     hereof, including all deliveries and obligations at Closing, shall have
     been duly performed in all material respects; and

                (iii)  all governmental and third party consents and approvals
     necessary to permit the consummation of the transactions contemplated by
     this Agreement shall have been received.

        (e) Expenses.  Purchaser shall receive its expenses pursuant to SECTION
7.4 of this Agreement.

        (f) Legal Opinion.  Purchaser shall receive a legal opinion from Mintz,
Levin, Cohn, Ferris, Glovsky and Popeo, P.C., counsel to the Company, covering
the matters set forth on EXHIBIT B attached hereto.

                                       17
<PAGE>

        (g) Waivers and Consents.  Purchaser shall receive, in the form of
EXHIBIT C attached hereto, a copy of the waiver of certain rights by the
stockholders of the Company.

        (h) Third Amendment to Stockholders Agreement.  The Company, Purchaser
and Signal Equity Partners, L.P. (formerly known as Signal Capital Partners,
L.P.) shall duly execute and deliver the Third Amendment to the Stockholders
Agreement substantially in the form of EXHIBIT D attached hereto, and the
Company and the Purchaser shall have received a duly executed counterpart
thereof.

        (i) Assignment.  The Company, FiberNet Operations, Inc., Purchaser and
Signal Equity Partners, L.P. (formerly known as Signal Capital Partners, L.P.)
shall duly execute and deliver the Assignment substantially in the form of
EXHIBIT E attached hereto, and the Company and the Purchaser shall have received
a duly executed counterpart thereof.

                                   ARTICLE VI
                                   COVENANTS

        So long as (i) at least twenty-five (25%) percent of the shares of
Preferred Stock shall be issued and outstanding; and (ii) a Qualified IPO has
not occurred, the Company covenants as follows in this Article VI.

6.1     TRANSFER OF PREFERRED STOCK.  Each certificate representing Preferred
Stock shall be stamped or otherwise imprinted with a legend in substantially the
following form:

          "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR
          INVESTMENT AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
          1933 OR THE SECURITIES LAWS OF ANY STATE.  THESE SECURITIES MAY NOT BE
          SOLD, TRANSFERRED OR OTHERWISE DISPOSED OF IN THE ABSENCE OF SUCH
          REGISTRATION OR AN EXEMPTION THEREFROM.  IN ADDITION, THE TRANSFER OF
          THESE SECURITIES IS SUBJECT TO THE CONDITIONS SPECIFIED IN THE
          STOCKHOLDERS AGREEMENT DATED AS OF MAY 7, 1999, AS AMENDED, BY AND
          AMONG FIBERNET TELECOM GROUP, INC. AND THE STOCKHOLDERS LISTED
          THEREIN.  SUCH AGREEMENT, AS AMENDED, RESTRICTS THE TRANSFER OF THESE
          SECURITIES UNTIL JUNE 30, 2001.  NO TRANSFER OF THESE SECURITIES SHALL
          BE VALID OR EFFECTIVE UNTIL SUCH CONDITIONS HAVE BEEN FULFILLED."

6.2     CONDUCT OF BUSINESS AND MAINTENANCE OF EXISTENCE.  The Company and its
Subsidiaries will continue to engage in business of the same general type as
conducted or contemplated to be conducted by the Company and its Subsidiaries on
the Closing Date, and use their reasonable commercial efforts to preserve, renew
and keep in full force and effect their respective corporate existences and take
all reasonable action to maintain all rights, privileges and franchises
necessary or desirable in the normal conduct of the business of the Company and
its Subsidiaries.

                                       18
<PAGE>

6.3     FINANCIAL AND OTHER INFORMATION.  The Company and its Subsidiaries will
maintain a system of accounts in accordance with sound accounting principles and
procedures, keep full and complete financial records and at the request of the
Purchaser, the Company shall promptly deliver to the Purchaser information
regarding the securityholders, officers and directors of the Company and any of
its Subsidiaries, including, without limitation, names, addresses, types of
securities held and terms of securities held.

6.4     ACCESS TO INFORMATION.  The Company and its Subsidiaries will permit
Purchaser to inspect, at Purchaser's expense, any of the properties or books and
records of the Company and any of the Subsidiaries, to make copies of extracts
from such books and records and to discuss the affairs and condition of the
Company and the Subsidiaries with representatives of the Company and such
Subsidiaries, all to such reasonable extent and at such reasonable times and
intervals as Purchaser may reasonably request.  The Company and its Subsidiaries
will furnish Purchaser copies of all correspondence and mailings to the
stockholders of the Company and its Subsidiaries at the same time such is given
or mailed to such Stockholders.

6.5     NO IMPAIRMENT.  The Company and the Subsidiaries will observe and
honor in good faith all rights of Purchaser under the terms of this Agreement or
any other documents executed in connection herewith, and will take no action
that would impair or otherwise prejudice such rights.

6.6     COMPLIANCE.  The Company shall comply, and cause each Subsidiary to
comply, with all applicable laws, rules, regulations and orders, noncompliance
with which could materially and adversely affect the business or condition,
financial or otherwise of the Company and the Subsidiaries, taken as a whole.

6.7     BROKERAGE.     The Company and its Subsidiaries agree to indemnify and
harmless Purchaser for any brokerage commissions, finder's fees or similar
compensation in connection with the transactions contemplated by this Agreement
based on any arrangement or agreement made by the Company or any Subsidiary.

6.8     EXCHANGE LISTING.  The Company will promptly apply to have listed, on a
when issued basis, on NASDAQ or any other exchange on which the Common Stock of
the Company is traded, any shares of Common Stock issuable to the Purchaser upon
the conversion of the Preferred Stock by the Purchaser.

6.9     HART-SCOTT-RODINO FILINGS.

  The  Company will make any filings required to be made by the Company under
the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, following
receipt of notice from the Purchaser that it intends to convert its Preferred
Stock and advice from counsel that such filing is required.  The Company shall
notify the Purchaser at least 60 days in advance of when the Company plans to
complete a Qualified Public Offering so that the Purchaser shall have adequate
time for it to determine whether filings are required under such Act and for the
Purchaser and the Company to make any required filings so that the mandatory
waiting period under that Act has expired or been terminated prior to the
mandatory conversion of the Purchaser's Preferred Stock.

                                       19
<PAGE>

6.10 SERIES C PREFERRED STOCK.

  The Company will not issue any additional shares of its Series C Preferred
Stock.

6.11 SERIES H PREFERRED STOCK.

  Other than in connection with the payment of in-kind dividends on previously
issued shares of the Company's Series H Preferred Stock, the Company will not
issue any additional shares of its Series H Preferred Stock without the prior
written consent of the Purchaser.

6.12 CONDUCT OF OPERATIONS.

     Except as otherwise permitted or contemplated by this Agreement or with the
written consent of Purchaser, the Company shall not (i) be merged with or into
any other corporation or entity; (ii) sell all or substantially all of its
assets to any third party; (iii) authorize, designate or issue any shares of a
new class or series of equity securities senior to the Preferred Stock as to
liquidation preference, redemption or dividends; (iv) change in any material
respect the principal business of the Company as such business is currently
conducted or as it has been proposed by the Company to the Purchaser to be
conducted; (v) repurchase any Common Stock or Preferred Stock, other than the
purchase of Common Stock from employees pursuant to agreements with the Company
as of the Closing Date to repurchase such stock; provided that the purchase
price shall not exceed the price paid by such employee for such stock; (vi)
declare or pay any dividend (other than a stock dividend) on the Common Stock;
(vii) except to the extent necessary to comply with foreign laws, create any
subsidiary in which the Company owns less than one hundred percent (100%) of the
equity securities, or permit any Subsidiary to issue any equity securities to
anyone other than the Company or a wholly-owned Subsidiary of the Company or
merge with or into any Subsidiary (other than in connection with the
transactions contemplated by the Agreement and Plan of Reorganization dated as
of June 2, 2000, by and among the Company, FiberNet Holdco, Inc., FiberNet
Merger Sub, Inc., Devnet Merger Sub, LLC, Devnet L.L.C. and F.P. Enterprises
L.L.C.); (viii) make any loans to any officers, directors or affiliates (other
than Subsidiaries) of the Company, other than (a) commission advances and travel
or miscellaneous cash advances in the ordinary course of business and (b) in
connection with the hiring and/or retention of senior executives; (ix) enter
into any business arrangement or agreement with any officer, director or
affiliate of the Company (other than (a) employment agreements, (b) stock option
agreements in accordance with the Company's Employee Equity Participation
Program or 1999 Stock Option Plan, each as amended through the date hereof or as
contemplated to be amended in the latest proxy statement filed by the Company
with the SEC and (c) transactions with Metromedia Fiber Network, Inc. ("MFN"),
Tishman Speyer Properties, LP ("TSP"), or any affiliates of MFN or TSP, which
transactions do not, in the aggregate, involve the issuance of securities
accounting for in excess of five percent (5%) of the fully diluted outstanding
Common Stock of the Company; provided, however, that agreements in effect as of
the date hereof shall not be counted against such five percent (5%) limit); (x)
enter into any arrangement or agreement which (a) conflicts with the rights of
the Purchaser with respect to its Preferred Stock, (b) restricts the Company's
performance under this Agreement or any of the other Transaction Documents or
(c) could result in the repurchase or redemption of any shares of Common Stock,
Preferred Stock or any securities convertible or exchangeable for shares of
Common Stock or Preferred Stock (other than pursuant to (a) agreements with

                                       20
<PAGE>

employees giving the Company the right to repurchase shares upon the termination
of services and (b) the terms of any redeemable preferred stock of the Company
outstanding on the date hereof); (xi) amend the Certificate of Incorporation or
Bylaws of the Company in any manner adverse to the Purchaser or the rights of
the holders of the Preferred Stock (it being understood and agreed that the
amendment of the Certificate of Incorporation for the purpose of authorizing or
issuing securities with rights and preferences junior or pari passu with the
rights and preferences of the Preferred Stock shall not be deemed to be adverse
to the Purchaser); and (xii) authorize a new stock option plan or grant plan or
amend its existing stock option plan (other than as such plan is contemplated to
be amended in the latest proxy statement filed by the Company with the SEC).

                                  ARTICLE VII

                             COVENANTS OF PURCHASER

7.1  CONVERSION.

     If the holder of a Majority in Interest (as defined in the Stockholders
Agreement) has irrevocably elected to have the stockholders bound by the
Stockholders Agreement (other than the Purchaser) convert all of their shares of
preferred stock of the Company into shares of Common Stock, that the Purchaser
may refuse, if requested, to convert its shares of Preferred Stock into shares
of Common Stock, except that the Purchaser may not refuse to do so if such
refusal is based primarily on Purchaser's desire or intent to cause the Company
to agree to purchase more equipment and/or software from the Purchaser or to
prevent the Company from purchasing equipment and/or software from another
vendor.

                                  ARTICLE VIII
                                 MISCELLANEOUS

8.1  COMMUNICATION.

     Subject to the express provisions of this Agreement, all communications
provided for or permitted hereunder shall be in writing, personally delivered to
an officer or other responsible employee of the addressee or sent by registered
mail, charges prepaid, or by telecopy with confirmed receipt (with hard copy to
follow), telegram or other means of recorded telecommunication, charges prepaid,
to the applicable address set forth below or to such other address as either
party hereto may from time to time designate to the other in such manner,
provided that no communication shall be sent by mail pending any threatened or
during any actual postal strike or other disruption of postal service in the
United States.  Any communication so personally delivered shall be deemed to
have been validly and effectively given on the date of such delivery.  Any
communication so sent by registered mail shall be deemed to have been validly
and effectively given on the tenth Business Day next following the day on which
it is sent.  Any communication so sent by telecopy, telegram or other means of

                                       21
<PAGE>

recorded telecommunication shall be deemed to have been validly and effectively
given on the Business Day next following the day on which it is sent.

     Communications sent to the Company shall be addressed to:

     FiberNet Telecom Group, Inc.
     570 Lexington Avenue
     New York, New York 10022
     Attention: President
     Telephone: (212) 405-6200
     Telecopier: (212) 421-8860

     With a copy  to:

     Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
     Chrysler Center
     666 Third Avenue, 25th Floor
     New York, New York 10017
     Attention:  Gordon Caplan, Esq.
     Telephone: (212) 986-7200
     Telecopier: (212) 983-3115

     Communications sent to the Purchaser shall be addressed to:

     Nortel Networks Inc.
     GMS 991 15 A40
     2221 Lakeside Blvd.
     Richardson, Texas 75082-4399
     Attention: Paul D. Day, Vice President Customer Finance North America
     Telephone: (972) 684-2271
     Telecopier: (972) 684-3679

     With a copy to:

     Jenkens & Gilchrist, a Professional Corporation
     1445 Ross Avenue
     Suite 3200
     Dallas, Texas 75202
     Attention: Daryl Robertson, Esq.
     Telephone: (214) 855-4165
     Telecopier: (214) 855-4300

8.2  RELIANCE UPON AND SURVIVAL OF REPRESENTATIONS, WARRANTIES AND COVENANTS.

     The Company acknowledges and agrees that the representations, warranties,
covenants, acknowledgements and agreements made herein are made with the
intention that they may be relied upon by Purchaser.  The Company further agrees
that by accepting the purchase of the

                                       22
<PAGE>

Preferred Stock hereunder that it shall be representing and warranting that the
foregoing representations, warranties, covenants, acknowledgements and
agreements apply with the same force and effect as if they had been made at the
time of Closing and without regard to any investigation made by Purchaser. The
Company hereby undertakes to notify Purchaser of any change in any
representation, warranty, covenant or other information relating to such parties
set forth herein that take place prior to the Closing. The representations and
warranties of the Company contained herein shall survive the Closing of the
transactions contemplated hereby and will continue in full force and effect for
a period of two (2) years thereafter; provided, however, that the
representations and warranties contained in Section 3.6 shall survive
indefinitely.

8.3  SUCCESSORS AND ASSIGNS.

     This Agreement shall inure to the benefit of and be binding on the parties
hereto, their respective successors and any assignees or transferees of some or
all of the parties' rights or obligations hereunder; provided that, except as
provided in the following sentence, neither this Agreement, nor the benefit
hereof, may be assigned by the Company without the prior written consent of the
Purchaser.

8.4  EXPENSES OF THE PURCHASER.

     The Company shall be responsible for and promptly pay (i) its own fees and
expenses and (ii) the reasonable fees and out-of-pocket expenses of Purchaser,
including reasonable fees and out-of-pocket expenses of Purchaser's counsel
incurred in connection with the preparation, execution and delivery of this
Agreement and the other Transaction Documents and the purchase of the Preferred
Stock hereunder; provided, however, that the Company's obligation to pay the
fees and expenses of Purchaser shall in no event exceed $35,000.

8.5  GOVERNING LAW.

        (a)  ALL QUESTIONS CONCERNING THE CONSTRUCTION, INTERPRETATION AND
VALIDITY OF THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH
THE DOMESTIC LAWS OF THE STATE OF NEW YORK WITHOUT GIVING EFFECT TO ANY CHOICE
OR CONFLICT OF LAW PROVISION OR RULE (WHETHER IN THE STATE OF NEW YORK OR ANY
OTHER JURISDICTION) THAT WOULD CAUSE THE APPLICATION OF THE LAWS OF ANY
JURISDICTION OTHER THAN THE STATE OF NEW YORK.

        (b)  DISPUTES ARISING IN CONNECTION WITH COMPLEX FINANCIAL TRANSACTIONS
ARE MOST QUICKLY AND ECONOMICALLY RESOLVED BY AN EXPERIENCED AND EXPERT PERSON.
THEREFORE, THE PARTIES HERETO WAIVE ALL RIGHT TO TRIAL BY JURY IN ANY ACTION,
SUIT OR PROCEEDING BROUGHT TO ENFORCE OR DEFEND ANY RIGHTS OR REMEDIES UNDER
THIS AGREEMENT OR ANY DOCUMENTS RELATED HERETO.

8.6     Rights and Waivers.

                                       23
<PAGE>

        (a)  The rights and remedies of Purchaser under the Transaction
Documents and in connection therewith: (i) are cumulative, (ii) may be exercised
as often and in such order as Purchaser consider appropriate, (iii) are in
addition to the rights and remedies of Purchaser under the general law, and (iv)
shall not be capable of being waived or varied except by virtue of an express
waiver or variation in writing signed by an officer of the Purchaser; and in
particular any failure to exercise or any delay in exercising any of such rights
and remedies shall, to the extent permitted by law, not operate as a waiver or
variation of that or any other such right or remedy; any defective or partial
exercise of any of such rights shall, to the extent permitted by law, not
preclude any other or future exercise of that or any other such right or remedy;
and no act or course of conduct or negotiation on the part of the Purchaser or
on its behalf shall, to the extent permitted by law, in any way preclude the
Purchaser from exercising any such right or remedy or constitute a suspension or
variation of any such right or remedy.

        (b)  No Transaction Document nor any provision thereof, may be waived,
amended or modified except pursuant to an agreement or agreements in writing
entered into by the parties thereto.

8.7  AMENDMENTS.

     No amendments to, or modification of, this Agreement shall be made without
the written consent of the Purchaser.

8.8  CONSTRUCTION.

     The Company and the Purchaser acknowledge that each of them has had the
benefit of legal counsel of its own choice and has been afforded an opportunity
to review this Agreement and the other Transaction Documents with its legal
counsel and that this Agreement and the other Transaction Documents shall be
construed as if jointly drafted by the Purchaser and the Company.

8.9  SEVERABILITY.

     Whenever possible, each provision of this Agreement will be interpreted in
such manner as to be effective and valid under applicable law, but if any
provision of this Agreement is held to be invalid, illegal or unenforceable in
any respect under any applicable law or rule in any jurisdiction, such
invalidity, illegality or unenforceability will not affect any other provision
or any other jurisdiction, and such invalid, void or otherwise unenforceable
provisions shall be null and void.  It is the intent of the parties, however,
that any invalid, void or otherwise unenforceable provisions be automatically
replaced by other provisions which are as similar as possible in terms to such
invalid, void or otherwise unenforceable provisions but are valid and
enforceable to the fullest extent permitted by law.

8.10 COUNTERPARTS.

     This Agreement may be executed in two or more counterparts, each of which
when executed and delivered shall deemed to be an original, but all of which
when taken together shall constitute but one and the same instrument; either
party may execute this Agreement by signing any counterpart of it.

                                       24
<PAGE>

8.11 HEADINGS.

     Article and Section headings used herein are for convenience of reference
only and are not to affect the construction of, or to be taken into
consideration in interpreting, this Agreement.

8.12 ENTIRE AGREEMENT.

     This Agreement, together with the other Transaction Documents, constitutes
the entire agreement between the parties relating to the subject matter hereof
and, except as stated herein or in the instruments and documents to be executed
and delivered pursuant hereto, contains all the representations and warranties
of the respective parties relating to the subject matter hereof.

8.13 Confidentiality.

     Unless required by law, the Company will not, without the prior written
consent of the Purchaser, such consent not to be unreasonably withheld or
delayed, make reference to the Purchaser in the Company's marketing,
advertising, press releases or other information available to the public.

                                       25
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Securities
Purchase Agreement to be duly executed by their authorized officers, all as of
the day and year first above written.

                              FIBERNET TELECOM GROUP, INC.

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

                              NORTEL NETWORKS INC.

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

<PAGE>

                                                                      Exhibit A
                                                                      ----------

                           CERTIFICATE OF DESIGNATION

<PAGE>

                                                                       Exhibit B
                                                                       ---------

                             FORM OF LEGAL OPINION

<PAGE>

                                                                       Exhibit C
                                                                       ---------

                               CONSENT AND WAIVER

<PAGE>

                                                                       Exhibit D
                                                                       ---------

                   THIRD AMENDMENT TO STOCKHOLDERS AGREEMENT

<PAGE>

                                                                       Exhibit E
                                                                       ---------

                      ASSIGNMENT AND ASSUMPTION AGREEMENT

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