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                                                                   Exhibit 10.48


                            NEON COMMUNICATIONS, INC.

                          REGISTRATION RIGHTS AGREEMENT

         This Agreement dated as of September 14, 2000 is entered into by and
among NEON Communications, Inc., a Delaware corporation (the "Company"),
Consolidated Edison Communications, Inc., a New York corporation ("CEC") and
Exelon Ventures Corp., a Pennsylvania corporation ("Exelon," and together with
CEC, the "Investors").

                                    RECITALS

         WHEREAS, the Company has entered into a separate Subscription Agreement
with each of CEC and Exelon dated as of November 23, 1999 (as amended to date,
the "Subscription Agreements"); and

         WHEREAS, the Company and the Investors desire to provide for certain
arrangements with respect to the registration of shares of capital stock of the
Company under the Securities Act of 1933;

         NOW, THEREFORE, in consideration of the mutual promises and covenants
contained in this Agreement, the parties hereto agree as follows:

         1. CERTAIN DEFINITIONS.

         As used in this Agreement, the following terms shall have the following
respective meanings:

                  "BUSINESS DAY" means any day other than Saturday, Sunday and
any day which is a legal holiday or a day on which banking institutions in New
York are authorized or required by law or other action of a governmental
authority to close.

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

                  "COMMON STOCK" means the common stock, $.01 par value per
share, of the Company.

                  "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended, or any successor federal statute, and the rules and regulations of the
Commission issued under such Act, as they each may, from time to time, be in
effect.

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                  "INITIATING HOLDERS" means the Investor or Investors
initiating a request for registration pursuant to Section 2.1(a).

                  "OTHER HOLDERS" shall have the meaning set forth in Section
2.1(c).

                  "PROSPECTUS" means the prospectus included in any Registration
Statement, as amended or supplemented by an amendment or prospectus supplement,
including post-effective amendments, and all material incorporated by reference
or deemed to be incorporated by reference in such Prospectus.

                  "REGISTRATION STATEMENT" means a registration statement filed
by the Company with the Commission for a public offering and sale of securities
of the Company (other than a registration statement on Form S-8 or Form S-4, or
their successors, or any other form for a similar limited purpose, or any
registration statement covering only securities proposed to be issued in
exchange for securities or assets of another corporation).

                  "REGISTRATION EXPENSES" means the expenses described in
Section 2.4.

                  "REGISTRABLE SHARES" means (i) the Shares and (ii) any other
shares of Common Stock issued in respect of the Shares (because of stock splits,
stock dividends, reclassifications, recapitalizations, or similar events);
provided, however, that shares of Common Stock which are Registrable Shares
shall cease to be Registrable Shares upon (i) any sale pursuant to a
Registration Statement or Rule 144 under the Securities Act (ii) their
eligibility for sale pursuant to Rule 144(k) under the Securities Act or (iii)
any sale in any manner to a person or entity which, by virtue of Section 3 of
this Agreement, is not entitled to the rights provided by this Agreement.

                  "SECURITIES ACT" means the Securities Act of 1933, as amended,
or any successor federal statute, and the rules and regulations of the
Commission issued under such Act, as they each may, from time to time, be in
effect.

                  "SELLING STOCKHOLDER" means any Stockholder owning Registrable
Shares included in a Registration Statement.

                  "SHARES" means the CEC NEON shares and the Exelon NEON shares
as defined in the Subscription Agreements.

                  "STOCKHOLDERS" means the Investors and any persons or entities
to whom the rights granted under this Agreement are transferred by any
Investors, their successors or assigns pursuant to Section 3 hereof.

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         2. REGISTRATION RIGHTS

                  2.1 REQUIRED REGISTRATIONS.

                  (1) At any time after the first anniversary of the closing of
the Subscription Agreements, either Investor may request, in writing, that the
Company effect the registration on Form S-3 (or any successor form or any other
registration statement form which the Company is eligible to use) of Registrable
Shares owned by such Investor having an aggregate value of at least $5,000,000
(based on the then current market price or fair value).

                  (2) Upon receipt of any request for registration pursuant to
this Section 2, the Company shall promptly give written notice of such proposed
registration to all other Stockholders. Such Stockholders shall have the right,
by giving written notice to the Company within 30 days after the Company
provides its notice, to elect to have included in such registration such of
their Registrable Shares as such Stockholders may request in such notice of
election, subject in the case of an underwritten offering to the approval of the
managing underwriter as provided in Section 2.1(c) below. Thereupon, the Company
shall, as expeditiously as possible, effect the registration of all Registrable
Shares which the Company has been requested to so register.

                  (3) If the Initiating Holders intend to distribute the
Registrable Shares covered by their request by means of an underwriting, they
shall so advise the Company as a part of their request made pursuant to Section
2.1(a), and the Company shall include such information in its written notice
referred to in Section 2.1(b). The right of any other Stockholder to include its
Registrable Shares in such registration pursuant to Section 2.1(a) shall be
conditioned upon such other Stockholder's participation in such underwriting on
the terms set forth herein. If the Company desires that any officers or
directors of the Company holding securities of the Company be included in any
registration for an underwritten offering requested pursuant to Section 2.1(c)
or if other holders of securities of the Company who are entitled, by contract
with, or other instrument executed by, the Company prior to the date hereof, to
have securities included in such a registration (the "Other Holders") request
such inclusion, the Company may include the securities of such officers,
directors and Other Holders in such registration and underwriting on the terms
set forth herein. The Company shall (together with all Stockholders, officers,
directors and Other Holders proposing to distribute their securities through
such underwriting) enter into an underwriting agreement in customary form
(including, without limitation, customary indemnification and contribution
provisions on the part of the Company) with the managing underwriter; PROVIDED
that such underwriting agreement shall not provide for indemnification or
contribution obligations on the part of Stockholders materially greater than the
obligations of the Stockholders pursuant to Section 2.5. Notwithstanding any
other provision of this Section 2.1(c), if the managing underwriter

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advises the Company that the inclusion of all shares requested to be registered
would adversely affect the offering, the securities of the Company held by
officers or directors of the Company (other than Registrable Shares) shall be
excluded from such registration and underwriting to the extent deemed advisable
by the managing underwriter, and if a further limitation of the number of shares
is required, the number of shares that may be included in such registration and
underwriting shall be allocated among all Other Holders and holders of
Registrable Shares pro rata in proportion to the respective number shares they
have requested to be registered. If any holder of Registrable Shares, officer,
director or Other Holder who has requested inclusion in such registration as
provided above disapproves of the terms of the underwriting, such person may
elect to withdraw therefrom by written notice to the Company, and the securities
so withdrawn shall also be withdrawn from registration. If the managing
underwriter has not limited the number of Registrable Shares or other securities
to be underwritten, the Company may include securities for its own account in
such registration if the managing underwriter so agrees and if the number of
Registrable Shares and other securities which would otherwise have been included
in such registration and underwriting will not thereby be limited.

                  (4) The Initiating Holders shall have the right to select the
managing underwriter(s) for any underwritten offering requested pursuant to
Section 2.1(a), subject to the approval of the Company, which approval will not
be unreasonably withheld.

                  (5) The Company shall not be required to effect more than two
registrations pursuant to Section 2.1(a), and neither Investor, acting
individually, shall be entitled to request a registration pursuant to Section
2.1(a) more than once. In addition, in the event that Form S-3 is not available
to the Company, the Company shall not be required to effect more than one
registration on Form S-1 pursuant to Section 2.1(a), and any request to effect a
registration on Form S-1 shall be made jointly by both Investors. For purposes
of this Section 2.1(e), a Registration Statement shall not be counted until such
time as such Registration Statement has been declared effective by the
Commission (unless the Initiating Holders withdraw their request for such
registration (other than as a result of information concerning the business or
financial condition of the Company which is made known to the Stockholders after
the date on which such registration was requested) and elect not to pay the
Registration Expenses therefor pursuant to Section 2.4).

                  (6) If at the time of any request to register Registrable
Shares by Initiating Holders pursuant to this Section 2.1, the Company is
engaged or has plans to engage in a registered public offering or is engaged in
any other activity which, in the good faith determination of the Company's Board
of Directors, would be adversely affected by the requested registration, then
the Company may at its option direct that such request be delayed for a period
not in excess of 90 days from the date of such

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request, such right to delay a request to be exercised by the Company not more
than once in any 12-month period.

         2.2 INCIDENTAL REGISTRATION.

                  (1) Whenever the Company proposes to file a Registration
Statement (other than a Registration Statement filed pursuant to Section 2.1) at
any time and from time to time, it will, prior to such filing, give written
notice to all Stockholders of its intention to do so; PROVIDED, that no such
notice need be given if no Registrable Shares are to be included therein as a
result of a determination of the managing underwriter pursuant to Section
2.2(b). Upon the written request of a Stockholder or Stockholders given within
20 days after the Company provides such notice, the Company shall use its best
efforts to cause all Registrable Shares which the Company has been requested by
such Stockholder or Stockholders to register to be registered under the
Securities Act to the extent necessary to permit their sale or other disposition
in accordance with the intended methods of distribution specified in the request
of such Stockholder or Stockholders; provided that the Company shall have the
right to postpone or withdraw any registration effected pursuant to this Section
2.2 without obligation to any Stockholder.

                  (2) If the registration for which the Company gives notice
pursuant to Section 2.2(a) is a registered public offering involving an
underwriting, the Company shall so advise the Stockholders as a part of the
written notice given pursuant to Section 2.2(a). In such event, the right of any
Stockholder to include its Registrable Shares in such registration pursuant to
Section 2.2 shall be conditioned upon such Stockholder's participation in such
underwriting on the terms set forth herein. All Stockholders proposing to
distribute their securities through such underwriting shall enter into an
underwriting agreement in customary form with the underwriter or underwriters
selected for the underwriting by the Company. Notwithstanding any other
provision of this Section 2.2, if the managing underwriter determines that the
inclusion of all shares requested to be registered would adversely affect the
offering, the Company may limit the number of Registrable Shares to be included
in the registration and underwriting. The Company shall so advise all holders of
Registrable Shares requesting registration, and the number of shares that are
entitled to be included in the registration and underwriting shall be allocated
in the following manner. The securities of the Company held by holders other
than Stockholders and Other Holders shall be excluded from such registration and
underwriting to the extent deemed advisable by the managing underwriter, and, if
a further limitation on the number of shares is required, the number of shares
that may be included in such registration and underwriting shall be allocated
among all Stockholders and Other Holders requesting registration in proportion,
as nearly as practicable, to the respective number of shares of Common Stock
which they held at the time the Company gives the notice specified in Section
2.2(a). If any Stockholder or Other Holder would thus be entitled to include

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more securities than such holder requested to be registered, the excess shall be
allocated among other requesting Stockholders and Other Holders pro rata in the
manner described in the preceding sentence. If any holder of Registrable Shares
or any officer, director or Other Holder disapproves of the terms of any such
underwriting, such person may elect to withdraw therefrom by written notice to
the Company, and any Registrable Shares or other securities excluded or
withdrawn from such underwriting shall be withdrawn from such registration.

                  (c) Notwithstanding the foregoing, the Company shall not be
required, pursuant to this Section 2.2, to include any Registrable Shares in a
Registration Statement if such Registrable Shares can then be sold pursuant to
Rule 144(k) under the Securities Act.

         2.3 REGISTRATION PROCEDURES.

                  (1) If and whenever the Company is required by the provisions
of this Agreement to use its best efforts to effect the registration of any
Registrable Shares under the Securities Act, the Company shall:

                  (1) file with the Commission a Registration Statement with
respect to such Registrable Shares and use its best efforts to cause that
Registration Statement to become effective as soon as possible;

                  (2) as expeditiously as possible prepare and file with the
Commission any amendments and supplements to the Registration Statement and the
prospectus included in the Registration Statement as may be necessary to comply
with the provisions of the Securities Act (including the anti-fraud provisions
thereof) and to keep the Registration Statement effective for 12 months from the
effective date or such lesser period until all such Registrable Shares are sold;

                  (3) as expeditiously as possible furnish to each Selling
Stockholder such reasonable numbers of copies of the Prospectus, including any
preliminary Prospectus, in conformity with the requirements of the Securities
Act, and such other documents as such Selling Stockholder may reasonably request
in order to facilitate the public sale or other disposition of the Registrable
Shares owned by such Selling Stockholder;

                  (4) as expeditiously as possible use its best efforts to
register or qualify the Registrable Shares covered by the Registration Statement
under the securities or Blue Sky laws of such states as the Selling Stockholders
shall reasonably request, and do any and all other acts and things that may be
necessary or desirable to enable the Selling Stockholders to consummate the
public sale or other disposition in such states of the Registrable Shares owned
by the Selling Stockholder;

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PROVIDED, HOWEVER, that the Company shall not be required in connection with
this paragraph (iv) to qualify as a foreign corporation or execute a general
consent to service of process in any jurisdiction;

                  (5) as expeditiously as possible, cause all such Registrable
Shares to be listed on each securities exchange or automated quotation system on
which similar securities issued by the Company are then listed;

                  (6) promptly provide a transfer agent and registrar for all
such Registrable Shares not later than the effective date of such registration
statement;

                  (7) promptly make available for inspection by the Selling
Stockholders, any managing underwriter participating in any disposition pursuant
to such Registration Statement, and any attorney or accountant or other agent
retained by any such underwriter or selected by the Selling Stockholders, all
financial and other records, pertinent corporate documents and properties of the
Company and cause the Company's officers, directors, employees and independent
accountants to supply all information reasonably requested by any such seller,
underwriter, attorney, accountant or agent in connection with such Registration
Statement;

                  (8) as expeditiously as possible, notify each Selling
Stockholder, promptly after it shall receive notice thereof, of the time when
such Registration Statement has become effective or a supplement to any
Prospectus forming a part of such Registration Statement has been filed; and

                  (9) as expeditiously as possible following the effectiveness
of such Registration Statement, notify each seller of such Registrable Shares of
any request by the Commission for the amending or supplementing of such
Registration Statement or Prospectus.

         (2) If the Company has delivered a Prospectus to the Selling
Stockholders and after having done so the Prospectus is amended to comply with
the requirements of the Securities Act, the Company shall promptly notify the
Selling Stockholders and, if requested, the Selling Stockholders shall
immediately cease making offers of Registrable Shares and return all
Prospectuses to the Company. The Company shall promptly provide the Selling
Stockholders with revised Prospectuses and, following receipt of the revised
Prospectuses, the Selling Stockholders shall be free to resume making offers of
the Registrable Shares.

         (3) In the event that, in the judgment of the Company, it is advisable
to suspend use of a Prospectus included in a Registration Statement due to
pending material developments or other events that have not yet been publicly

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disclosed and as to which the Company believes public disclosure would be
detrimental to the Company, the Company shall notify all Selling Stockholders to
such effect, and, upon receipt of such notice, each such Selling Stockholder
shall immediately discontinue any sales of Registrable Shares pursuant to such
Registration Statement until such Selling Stockholder has received copies of a
supplemented or amended Prospectus or until such Selling Stockholder is advised
in writing by the Company that the then current Prospectus may be used and has
received copies of any additional or supplemental filings that are incorporated
or deemed incorporated by reference in such Prospectus. Notwithstanding anything
to the contrary herein, the Company shall not exercise its rights under this
Section 2.3(c) to suspend sales of Registrable Shares for a period in excess of
60 days in any 365-day period.

                  2.4 ALLOCATION OF EXPENSES. The Company will pay all
Registration Expenses for all registrations under this Agreement; PROVIDED,
HOWEVER, that if a registration under Section 2.1 is withdrawn at the request of
the Initiating Holders (other than as a result of information concerning the
business or financial condition of the Company which is made known to the
Stockholders after the date on which such registration was requested) and if the
Initiating Holders elect not to have such registration counted as a registration
requested under Section 2.1, the requesting Stockholders shall pay the
Registration Expenses of such registration pro rata in accordance with the
number of their Registrable Shares included in such registration. For purposes
of this Section, the term "Registration Expenses" shall mean all expenses
incurred by the Company in complying with this Agreement, including, without
limitation, all registration and filing fees, exchange listing fees, printing
expenses, fees and expenses of counsel for the Company and the fees and expenses
of one counsel selected by the Selling Stockholders to represent the Selling
Stockholders, state Blue Sky fees and expenses, and the expense of any special
audits incident to or required by any such registration, but excluding
underwriting discounts, selling commissions and the fees and expenses of Selling
Stockholders' own counsel (other than the counsel selected to represent all
Selling Stockholders).

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         2.5 INDEMNIFICATION AND CONTRIBUTION.

             (1) In the event of any registration of any of the Registrable
Shares under the Securities Act pursuant to this Agreement, the Company will
indemnify and hold harmless the seller of such Registrable Shares, each
underwriter of such Registrable Shares, and each other person, if any, who
controls such seller or underwriter within the meaning of the Securities Act or
the Exchange Act against any losses, claims, damages or liabilities, joint or
several, to which such seller, underwriter or controlling person may become
subject under the Securities Act, the Exchange Act, state securities or Blue Sky
laws or otherwise, insofar as such losses, claims, damages or liabilities (or
actions in respect thereof) arise out of or are based upon any untrue statement
or alleged untrue statement of any material fact contained in any Registration
Statement under which such Registrable Shares were registered under the
Securities Act, any preliminary prospectus or final prospectus contained in the
Registration Statement, or any amendment or supplement to such Registration
Statement, or arise out of or are based upon the omission or alleged omission to
state a material fact required to be stated therein or necessary to make the
statements therein not misleading; and the Company will reimburse such seller,
underwriter and each such controlling person for any legal or any other expenses
reasonably incurred by such seller, underwriter or controlling person in
connection with investigating or defending any such loss, claim, damage,
liability or action; PROVIDED, HOWEVER, that the Company will not be liable in
any such case to the extent that any such loss, claim, damage or liability
arises out of or is based upon any untrue statement or omission made in such
Registration Statement, preliminary prospectus or prospectus, or any such
amendment or supplement, in reliance upon and in conformity with information
furnished to the Company, in writing, by or on behalf of such seller,
underwriter or controlling person specifically for use in the preparation
thereof.

             (2) In the event of any registration of any of the Registrable
Shares under the Securities Act pursuant to this Agreement, each seller of
Registrable Shares, severally and not jointly, will indemnify and hold harmless
the Company, each of its directors and officers and each underwriter (if any)
and each person, if any, who controls the Company or any such underwriter within
the meaning of the Securities Act or the Exchange Act, against any losses,
claims, damages or liabilities, joint or several, to which the Company, such
directors and officers, underwriter or controlling person may become subject
under the Securities Act, Exchange Act, state securities or Blue Sky laws or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of a material fact contained in any Registration Statement
under which such Registrable Shares were registered under the Securities Act,
any preliminary prospectus or final prospectus contained in the Registration
Statement, or any amendment or supplement to the Registration Statement, or
arise out of or are based upon any omission or alleged omission to state a
material fact required to be stated

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therein or necessary to make the statements therein not misleading, if the
statement or omission was made in reliance upon and in conformity with
information relating to such seller furnished in writing to the Company by or on
behalf of such seller specifically for use in connection with the preparation of
such Registration Statement, prospectus, amendment or supplement; PROVIDED,
HOWEVER, that the obligations of a Stockholder hereunder shall be limited to an
amount equal to the net proceeds to such Stockholder of Registrable Shares sold
in connection with such registration.

             (3) Each party entitled to indemnification under this Section (the
"Indemnified Party") shall give notice to the party required to provide
indemnification (the "Indemnifying Party") promptly after such Indemnified Party
has actual knowledge of any claim as to which indemnity may be sought, and shall
permit the Indemnifying Party to assume the defense of any such claim or any
litigation resulting therefrom; PROVIDED, that counsel for the Indemnifying
Party, who shall conduct the defense of such claim or litigation, shall be
approved by the Indemnified Party (whose approval shall not be unreasonably
withheld); and, PROVIDED, FURTHER, that the failure of any Indemnified Party to
give notice as provided herein shall not relieve the Indemnifying Party of its
obligations under this Section except to the extent that the Indemnifying Party
is adversely affected by such failure. The Indemnified Party may participate in
such defense at such party's expense; PROVIDED, HOWEVER, that the Indemnifying
Party shall pay such expense if representation of such Indemnified Party by the
counsel retained by the Indemnifying Party would be inappropriate due to actual
or potential differing interests between the Indemnified Party and any other
party represented by such counsel in such proceeding; PROVIDED FURTHER that in
no event shall the Indemnifying Party be required to pay the expenses of more
than one law firm per jurisdiction as counsel for the Indemnified Party. The
Indemnifying Party also shall be responsible for the expenses of such defense if
the Indemnifying Party does not elect to assume such defense. No Indemnifying
Party, in the defense of any such claim or litigation shall, except with the
consent of each Indemnified Party, consent to entry of any judgment or enter
into any settlement which does not include as an unconditional term thereof the
giving by the claimant or plaintiff to such Indemnified Party of a release from
all liability in respect of such claim or litigation, and no Indemnified Party
shall consent to entry of any judgment or settle such claim or litigation
without the prior written consent of the Indemnifying Party, which consent shall
not be unreasonably withheld.

             (4) In order to provide for just and equitable contribution in
circumstances in which the indemnification provided for in this Section 2.5 is
due in accordance with its terms but for any reason is held to be unavailable to
an Indemnified Party in respect to any losses, claims, damages and liabilities
referred to herein, then the Indemnifying Party shall, in lieu of indemnifying
such Indemnified Party, contribute to the amount paid or payable by such
Indemnified Party as a result of such losses, claims, damages or liabilities to
which such party may be subject in such

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proportion as is appropriate to reflect the relative fault of the Company on the
one hand and the Stockholders on the other in connection with the statements or
omissions which resulted in such losses, claims, damages or liabilities, as well
as any other relevant equitable considerations. The relative fault of the
Company and the Stockholders shall be determined by reference to, among other
things, whether the untrue or alleged untrue statement of material fact related
to information supplied by the Company or the Stockholders and the parties'
relative intent, knowledge, access to information and opportunity to correct or
prevent such statement or omission. The Company and the Stockholders agree that
it would not be just and equitable if contribution pursuant to this Section 2.5
were determined by pro rata allocation or by any other method of allocation
which does not take account of the equitable considerations referred to above.
Notwithstanding the provisions of this paragraph of Section 2.5, (a) in no case
shall any one Stockholder be liable or responsible for any amount in excess of
the net proceeds received by such Stockholder from the offering of Registrable
Shares and (b) the Company shall be liable and responsible for any amount in
excess of such proceeds; PROVIDED, HOWEVER, that no person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation. Any party entitled to contribution will, promptly
after receipt of notice of commencement of any action, suit or proceeding
against such party in respect of which a claim for contribution may be made
against another party or parties under this Section, notify such party or
parties from whom contribution may be sought, but the omission so to notify such
party or parties from whom contribution may be sought shall not relieve such
party from any other obligation it or they may have thereunder or otherwise
under this Section. No party shall be liable for contribution with respect to
any action, suit, proceeding or claim settled without its prior written consent,
which consent shall not be unreasonably withheld.

             2.6 OTHER MATTERS WITH RESPECT TO UNDERWRITTEN OFFERINGS. In the
event that Registrable Shares are sold pursuant to a Registration Statement in
an underwritten offering pursuant to Section 2.1, the Company agrees to (a)
enter into an underwriting agreement containing customary representations and
warranties with respect to the business and operations of the Company and
customary covenants and agreements to be performed by the Company, including
without limitation customary provisions with respect to indemnification by the
Company of the underwriters of such offering; (b) use its best efforts to cause
its legal counsel to render customary opinions to the underwriters with respect
to the Registration Statement; and (c) use its best efforts to cause its
independent public accounting firm to issue customary "cold comfort letters" to
the underwriters with respect to the Registration Statement.

             2.7 INFORMATION BY HOLDER. Each holder of Registrable Shares
included in any registration shall furnish to the Company such information
regarding such holder and the distribution proposed by such holder as the
Company may reasonably

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request in writing and as shall be required in connection with any registration,
qualification or compliance referred to in this Agreement.

             2.8 CONFIDENTIALITY OF NOTICES. Any Stockholder receiving any
written notice from the Company regarding the Company's plans to file a
Registration Statement shall treat such notice confidentially and shall not
disclose such information to any person other than as necessary to exercise its
rights under this Agreement.

             2.9 RULE 144 REQUIREMENTS. The Company hereby agrees to:

                 (1) make and keep current public information about the Company
available, as those terms are understood and defined in Rule 144;

                 (2) file with the Commission in a timely manner all reports and
other documents required of the Company under the Securities Act and the
Exchange Act; and

                 (3) furnish to any holder of Registrable Shares upon request
(i) a written statement by the Company as to its compliance with the reporting
requirements of Rule 144 and of the Securities Act and the Exchange Act, (ii) a
copy of the most recent annual or quarterly report of the Company, and (iii)
such other reports and documents of the Company as such holder may reasonably
request to avail itself of any similar rule or regulation of the Commission
allowing it to sell any such securities without registration.

             2.10 TERMINATION. All of the Company's obligations to register
Registrable Shares under Sections 2.1 and 2.2 of this Agreement shall terminate
five years after the date hereof.

         3. TRANSFERS OF RIGHTS. This Agreement, and the rights and obligations
of each Investor hereunder, may be assigned by such Investor to any person or
entity to which at least 25% of the Shares held by such Investor are transferred
by such Investor, provided, however, that for purposes of Section 2.1(a), any
such transferees, together with the transferring Investor if such Investor
continues to hold any Registrable Securities, shall be counted as one Investor,
and any decision to demand a registration pursuant to Section 2.1(a) shall be
made by the holders of a majority of the Registrable Securities held by the
transferring Investor and such transferees.

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         4. GENERAL.

             (1) SEVERABILITY. The invalidity or unenforceability of any
provision of this Agreement shall not affect the validity or enforceability of
any other provision of this Agreement.

             (2) SPECIFIC PERFORMANCE. In addition to any and all other remedies
that may be available at law in the event of any breach of this Agreement, each
Investor shall be entitled to specific performance of the agreements and
obligations of the Company hereunder and to such other injunctive or other
equitable relief as may be granted by a court of competent jurisdiction.

             (3) GOVERNING LAW. This Agreement shall be governed by and
construed in accordance with the internal laws of the Commonwealth of
Massachusetts (without reference to the conflicts of law provisions thereof).

             (4) NOTICES. All notices, requests, consents, and other
communications under this Agreement shall be in writing and shall be deemed
delivered (i) two Business Days after being sent by registered or certified
mail, return receipt requested, postage prepaid or (ii) one Business Day after
being sent via a reputable nationwide overnight courier service guaranteeing
next Business Day delivery, in each case to the intended recipient as set forth
below:

         If to the Company, to:  NEON Communications, Inc.
                                 2200 West Park Drive
                                 Westborough, MA 01581
                                 Attention: President

or at such other address or addresses as may have been furnished in writing by
the Company to the Investors

         with a copy to:         Hale and Dorr LLP
                                 60 State Street
                                 Boston, MA 02109
                                 Attention:  Alexander A. Bernhard, Esq.
                                 Facsimile Number: (617) 526-5000

         If to Exelon, to:       Exelon Ventures Corp.
                                 2301 Market Street
                                 Philadelphia, PA 19101
                                 Attention: President
                                 Facsimile: (215) 841-6374

         with a copy to:         PECO Law Department
                                 2301 Market Street, 23rd Floor
                                 Philadelphia, PA 19101
                                 Attention: John Halderman
                                 Facsimile Number: 215-841-4474]

                                      -13-
<PAGE>

         If to CEC:              Consolidated Edison Communications, Inc.
                                 132 West 31st Street 13th Floor
                                 New York, NY 10001
                                 Attention: President
                                 Facsimile Number: (212) 324-5050

         with a copy to:         Consolidated Edison, Inc.
                                 4 Irving Place, Room 1800
                                 New York, NY 10003
                                 Attention: Senior Vice President and
                                    General Counsel
                                 Facsimile Number: (212) 324-5001

or at such other addresses as may have been furnished in writing by CECD or
Exelon to the Company.

         Any party may give any notice, request, consent or other communication
under this Agreement using any other means (including, without limitation,
personal delivery, messenger service, telecopy, first class mail or electronic
mail), but no such notice, request, consent or other communication shall be
deemed to have been duly given unless and until it is actually received by the
party for whom it is intended. Any party may change the address to which
notices, requests, consents or other communications hereunder are to be
delivered by giving the other parties notice in the manner set forth in this
Section.

             (5) COMPLETE AGREEMENT. This Agreement constitutes the entire
agreement and understanding of the parties hereto with respect to the subject
matter hereof and supersedes all prior agreements and understandings relating to
such subject matter.

             (6) AMENDMENTS AND WAIVERS. Any term of this Agreement may be
amended or terminated and the observance of any term of this Agreement may be
waived (either generally or in a particular instance and either retroactively or
prospectively), with the written consent of the Company and the holders of at
least 51% of the Registrable Shares held by all of the Stockholders; PROVIDED,
that this Agreement may be amended with the consent of the holders of less than
all Registrable Shares only in a manner which applies to all such holders in the
same fashion. Any such amendment, termination or waiver effected in accordance
with this Section 4(f) shall be binding on all parties hereto, even if they do
not execute such consent. No waivers of

                                      -14-
<PAGE>

or exceptions to any term, condition or provision of this Agreement, in any one
or more instances, shall be deemed to be, or construed as, a further or
continuing waiver of any such term, condition or provision.

             (7) PRONOUNS. Whenever the context may require, any pronouns used
in this Agreement shall include the corresponding masculine, feminine or neuter
forms, and the singular form of nouns and pronouns shall include the plural, and
vice versa.

             (8) COUNTERPARTS; FACSIMILE SIGNATURES. This Agreement may be
executed in any number of counterparts, each of which shall be deemed to be an
original, and all of which together shall constitute one and the same document.
This Agreement may be executed by facsimile signatures.

             (9) SECTION HEADINGS. The section headings are for the convenience
of the parties and in no way alter, modify, amend, limit or restrict the
contractual obligations of the parties.


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                                      -15-
<PAGE>

         Executed as of the date first written above.

                             NEON COMMUNICATIONS, INC.


                             By:_____________________________________

                             Name:___________________________________

                             Title:__________________________________


                             CONSOLIDATED EDISON COMMUNICATIONS, INC.


                             By:_____________________________________

                             Name:___________________________________

                             Title:__________________________________


                             EXELON VENTURES CORP.


                             By:_____________________________________

                             Name:___________________________________

                             Title:__________________________________