<PAGE>   1
                                                                    Exhibit 10.3

                       QUANTUM BRIDGE COMMUNICATIONS, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN


     This is the 2000 Employee Stock Purchase Plan of Quantum Bridge
Communications, Inc.

     1. PURPOSE. The purpose of the Plan is to provide employees of the Company
with an opportunity to purchase Common Stock of the Company through accumulated
payroll deductions. The Company intends to have the Plan qualify as an "Employee
Stock Purchase Plan" under Section 423 of the Code. Accordingly, the provisions
of the Plan shall be construed so as to extend and limit participation in a
manner consistent with the requirements of that section of the Code.

     2. DEFINITIONS.

          (a) "BOARD" shall mean the Board of Directors of the Company.

          (b) "CODE" shall mean the Internal Revenue Code of 1986, as amended.

          (c) "COMMON STOCK" shall mean the Common Stock of the Quantum Bridge
Communications, Inc.

          (d) "COMPANY" shall mean Quantum Bridge Communications, Inc. and any
Designated Subsidiary of Quantum Bridge Communications, Inc.

          (e) "COMPENSATION" shall mean the amount of money reportable on an
Employee's Federal income Tax Withholding Statement (Form W-2) before any
withholdings for health insurance or under a Section 401(k), 125, 129 or similar
plan, including without limitation, salary, wages, and sales commissions, but
excluding overtime, shift premium, bonuses and incentive compensation (other
than sales commissions), third party sick or disability pay, allowances or
reimbursements for expenses such as relocation allowances or travel expenses,
whether specifically designated as such or designated as signing bonuses, income
or gains attributable to restricted stock, stock options, stock appreciation
rights or other similar equity-based compensation, imputed income or non-cash
items, such as life insurance premiums, and similar items, whether or not
specifically itemized on the Form W-2.

          (f) "DESIGNATED SUBSIDIARIES" shall mean the Subsidiaries which have
been designated by the Board from time to time in its sole discretion as
eligible to participate in the Plan.

          (g) "EMPLOYEE" shall mean any individual who is an Employee of the
Company for tax purposes whose customary employment with the Company is at least
twenty (20) hours per week and more than five (5) months in any calendar year.



<PAGE>   2

          (h) "ENROLLMENT DATE" shall mean the first day of each Offering
Period.

          (i) "EXERCISE DATE" shall mean the last day of each Purchase Period.

          (j) "FAIR MARKET VALUE" shall mean, as of any date, the value of
Common Stock determined as follows:

               (1) If the Common Stock is listed on any established stock
exchange or a national market system, including without limitation the Nasdaq
National Market or The Nasdaq SmallCap Market of The Nasdaq Stock Market, its
Fair Market Value shall be the closing sales price for such stock (or the
closing bid, if no sales were reported) as quoted on such exchange or system for
the last market trading day prior to the time of determination, as reported in
The Wall Street Journal or such other source as the Board deems reliable;

               (2) If the Common Stock is regularly quoted by a recognized
securities dealer but selling prices are not reported, its Fair Market Value
shall be the mean of the closing bid and asked prices for the Common Stock on
the date of such determination, as reported in The Wall Street Journal or such
other source as the Board deems reliable; or

               (3) In the absence of an established market for the Common Stock,
the Fair Market Value thereof shall be determined in good faith by the Board.

          (k) "OFFERING PERIODS" shall mean the periods of approximately
twenty-four (24) months during which an option granted pursuant to the Plan may
be exercised, commencing on the first Trading Day on or after February 15 and
August 15 of each year and terminating on the last Trading Day in the periods
ending twenty-four months later. The duration and timing of Offering Periods may
be changed pursuant to Section 4 of this Plan.

          (l) "PLAN" shall mean this 2000 Employee Stock Purchase Plan.

          (m) "PURCHASE PERIOD" shall mean the period commencing the day after
an Exercise Date and ending on the Trading Day closest to the day that is six
months after the preceding Exercise Date, except that the first Purchase Period
of any Offering Period shall commence on the Enrollment Date and end with the
Trading Day that is six months after the Enrollment Date. The duration and
timing of Purchase Periods may be changed pursuant to Section 4 of the Plan.

          (n) "PURCHASE PRICE" shall mean an amount equal to 85% of the Fair
Market Value of a share of Common Stock on the Enrollment Date or on the
Exercise Date, whichever is lower.

          (o) "RESERVES" shall mean the number of shares of Common Stock covered
by each option under the Plan which have not yet been exercised and the number
of shares of Common Stock which have been authorized for issuance under the Plan
but not yet placed under option.


                                      -2-
<PAGE>   3


          (p) "SUBSIDIARY" shall mean any present or future subsidiary
corporation as defined in Section 424(f) of the Code.

          (q) "TRADING DAY" shall mean a day on which national stock exchanges
and the Nasdaq System are open for trading.

     3. ELIGIBILITY.

          (a) Any Employee who shall be employed by the Company on a given
Enrollment Date shall be eligible to participate in the Plan; provided, however,
that an Employee may not participate in more than one Offering Period at the
same time.

          (b) Any provisions of the Plan to the contrary notwithstanding, no
Employee shall be granted an option under the Plan:

               (1) to the extent that, immediately after the grant, such
Employee (or any other person whose stock would be attributed to such Employee
pursuant to Section 424(d) of the Code) would own capital stock of the Company
or of any Subsidiary and/or hold outstanding options to purchase such stock
possessing five percent (5%) or more of the total combined voting power or value
of all classes of the capital stock of the Company or of any Subsidiary; or

               (2) to the extent that his or her rights to purchase stock under
all employee stock purchase plans of the Company and its Subsidiaries accrues at
a rate which exceeds Twenty-Five Thousand Dollars ($25,000) worth of stock
(determined at the Fair Market Value of the shares at the time such option is
granted) for each calendar year in which such option is outstanding at any time.
In the event that an Employee may not be granted an option under the Plan
because of the foregoing restrictions, the Employee shall be granted an option
to purchase the maximum number of shares that would not violate the foregoing
restrictions.

     4. OFFERING PERIODS. The Plan shall be implemented by consecutive,
overlapping Offering Periods with a new Offering Period commencing on the first
Trading Day on or after February 15 and August 15 each year, or on such other
date as the Board shall determine, and continuing thereafter until terminated in
accordance with Section 19 hereof, provided, however, that (i) the first
Offering Period under the Plan (the "First Offering Period") shall commence upon
the effectiveness of a registration statement filed by the Company pursuant to
the Securities Act of 1933, as amended, with the Securities and Exchange
Commission for an initial public offering of shares of Common Stock and (ii) the
First Offering Period shall terminate on the last trading day prior to the
February 15 or the August 15 that is closest to the twenty-four month
anniversary of the commencement of the First Offering Period, provided that the
First Offering Period shall not be longer than twenty-seven months. The Board
shall have the power to change the duration of Offering Periods and Purchase
Periods (including the commencement dates thereof) with respect to future
offerings without stockholder approval.

     5. PARTICIPATION.


                                      -3-
<PAGE>   4


          (a) An eligible Employee may become a participant in the Plan by
completing a subscription agreement authorizing payroll deductions in the form
of EXHIBIT A to this Plan and filing it on or prior to the applicable Enrollment
Date with the Company's payroll office or such other office as the Company may
direct.

          (b) Payroll deductions for a participant shall commence on the first
payroll following the Enrollment Date and shall end on the last payroll in the
Offering Period to which such authorization is applicable, unless sooner
terminated by the participant as provided in Section 10 hereof.

     6. PAYROLL DEDUCTIONS.

          (a) At the time a participant files his or her subscription agreement,
he or she shall elect to have payroll deductions made on each pay day during the
Offering Period in an amount not exceeding twenty percent (20%) of the
Compensation which he or she receives on each pay day during the Offering
Period. Such payroll deductions shall be in whole percentages only.

          (b) All payroll deductions made for a participant shall be credited to
his or her account under the Plan. A participant may not make any additional
payments into such account.

          (c) A participant may discontinue his or her participation in the Plan
as provided in Section 10 hereof, or may increase or decrease the rate of his or
her payroll deductions during the Offering Period by completing and filing with
the Company a new subscription agreement authorizing a change in payroll
deduction rate. The Board may, in its discretion, limit the number of
participation rate changes during any Offering Period. The change in payroll
deduction rate shall be effective with the first full payroll period following
ten (10) business days after the Company's receipt of the new subscription
agreement. A participant's subscription agreement shall remain in effect for
successive Offering Periods unless terminated as provided in Section 10 hereof.

          (d) At the time the option is exercised, in whole or in part, or at
the time any of the Company's Common Stock issued under the Plan is disposed of,
the participant must make adequate provision for the Company's federal, state,
or other tax withholding obligations, if any, which arise upon the exercise of
the option or the disposition of the Common Stock. At any time, the Company may,
but shall not be obligated to, withhold from the participant's compensation the
amount necessary for the Company to meet applicable withholding obligations,
including any withholding required to make available to the Company any tax
deductions or benefits attributable to sale or other disposition of Common Stock
by the Employee.

     7. GRANT OF OPTION. On the Enrollment Date of each Offering Period, each
eligible Employee participating in such Offering Period shall be granted an
option to purchase (at the applicable Purchase Price) up to a whole number of
shares of the Company's Common Stock the ("Option Shares") determined by
dividing $50,000 by the Fair Market Value of a share of Common Stock on the
Enrollment Date (subject to any adjustment pursuant to Section 18), and provided
that



                                      -4-
<PAGE>   5

such purchase shall be subject to the limitations set forth in Sections
3(b) and 12 hereof. The option shall be exercisable as to 25% of the Option
Shares on each Exercise Date during the Offering Period. Exercise of the option
shall occur as provided in Section 8 hereof, unless the participant has
withdrawn pursuant to Section 10 hereof. The option shall expire on the last day
of the Offering Period.

     8. EXERCISE OF OPTION. Unless a participant withdraws from the Plan as
provided in Section 10 hereof, his or her option for the purchase of shares
shall be exercised automatically on each Exercise Date during the Offering
Period, and a number of full shares not exceeding the number of shares as to
which such participant's option is exercisable on such Exercise Date shall be
purchased for such participant at the applicable Purchase Price with the
accumulated payroll deductions in his or her account. No fractional shares shall
be purchased. Any payroll deductions accumulated in a participant's account
which are not sufficient to purchase a full share of Common Stock shall be
retained in the participant's account for the subsequent Purchase Period or
Offering Period, subject to earlier withdrawal by the participant as provided in
Section 10 hereof. Any other monies left over in a participant's account after
the Exercise Date shall be returned to the participant. During a participant's
lifetime, a participant's option to purchase shares hereunder is exercisable
only by him or her.

     9. DELIVERY. As promptly as practicable after each Exercise Date on which a
purchase of shares occurs, the Company shall arrange the delivery to each
participant or to his or her designee, as appropriate, of a certificate
representing the shares purchased upon exercise of his or her option. The
Company may, in its sole discretion and in compliance with applicable laws,
authorize the use of book entry registration of shares in lieu of issuing
certificates.

     10. WITHDRAWAL; TERMINATION OF EMPLOYMENT.

          (a) A participant may withdraw all but not less than all the payroll
deductions credited to his or her account and not yet used to exercise his or
her option under the Plan at any time by giving written notice to the Company in
the form of EXHIBIT B to this Plan. All of the participant's payroll deductions
credited to his or her account shall be paid to such participant promptly after
receipt of notice of withdrawal and such participant's option for the Offering
Period shall be automatically terminated, and no further payroll deductions for
the purchase of shares shall be made for such Offering Period. If a participant
withdraws from an Offering Period, payroll deductions shall not resume at the
beginning of the succeeding Offering Period unless the participant delivers to
the Company a new subscription agreement.

          (b) Upon a participant's ceasing to be an Employee, for any reason, he
or she shall be deemed to have elected to withdraw from the Plan and the payroll
deductions credited to such participant's account during the Offering Period but
not yet used to exercise the option shall be returned to such participant or, in
the case of his or her death, to the person or persons entitled thereto under
Section 14 hereof, and such participant's option shall be automatically
terminated. If, prior to the last day of the Offering Period, the Designated
Subsidiary by which the Employee is employed shall cease to be a Subsidiary of
the Company, or if the Employee is transferred to a



                                      -5-
<PAGE>   6

Subsidiary of the Company that is not a Designated Subsidiary, the Employee
shall be deemed to have terminated employment for purposes of this Plan.

          (c) A participant's withdrawal from an Offering Period shall not have
any effect upon his or her eligibility to participate in any similar plan which
may hereafter be adopted by the Company or in succeeding Offering Periods.

     11. INTEREST. No interest shall accrue on the payroll deductions of a
participant in the Plan.

     12. STOCK.

          (a) Subject to adjustment as provided in Section 18(a) hereof, the
maximum number of shares of Common Stock which shall be made available for sale
under the Plan shall be 2,000,000 shares, provided, however, that an annual
increase to the number of shares of Common Stock available for issuance under
the Plan shall be added on January 1 of each year beginning on January 1, 2002
equal to the lesser of (i) 2% of the total outstanding shares of the Company on
such date and (ii) an amount determined by the Board. Notwithstanding the
foregoing, in no event shall the aggregate number of shares of Common Stock
available for issuance under the Plan exceed 10,000,000 shares of Common Stock.
If, on a given Exercise Date, the number of shares with respect to which options
are to be exercised exceeds the number of shares then available under the Plan,
the Company shall make a pro rata allocation of the shares remaining available
for purchase in as uniform a manner as shall be practicable and as it shall
determine to be equitable.

          (b) The participant shall have no interest or voting right in shares
covered by his option until such option has been exercised.

          (c) Shares to be delivered to a participant under the Plan shall be
registered in the name of the participant or in the name of the participant and
his or her spouse.

     13. ADMINISTRATION. The Plan shall be administered by the Board or a
committee of members of the Board appointed by the Board. The Board or its
committee shall have full and exclusive discretionary authority to construe,
interpret and apply the terms of the Plan, to determine eligibility and to
adjudicate all disputed claims filed under the Plan. Every finding, decision and
determination made by the Board or its committee shall, to the full extent
permitted by law, be final and binding upon all parties.



                                      -6-
<PAGE>   7

     14. DESIGNATION OF BENEFICIARY.

          (a) A participant may file a written designation of a beneficiary who
is to receive any shares and cash, if any, from the participant's account under
the Plan in the event of such participant's death subsequent to an Exercise Date
on which the option is exercised but prior to delivery to such participant of
such shares and cash. In addition, a participant may file a written designation
of a beneficiary who is to receive any cash from the participant's account under
the Plan in the event of such participant's death prior to exercise of the
option. If a participant is married and the designated beneficiary is not the
spouse, spousal consent shall be required for such designation to be effective.

          (b) Such designation of beneficiary may be changed by the participant
at any time by written notice. In the event of the death of a participant and in
the absence of a beneficiary validly designated under the Plan who is living at
the time of such participant's death, the Company shall deliver such shares
and/or cash to the executor or administrator of the estate of the participant,
or if no such executor or administrator has been appointed (to the knowledge of
the Company), the Company, in its discretion, may deliver such shares and/or
cash to the spouse or to any one or more dependents or relatives of the
participant, or if no spouse, dependent or relative is known to the Company,
then to such other person as the Company may designate.

     15. TRANSFERABILITY. Neither payroll deductions credited to a participant's
account nor any rights with regard to the exercise of an option or to receive
shares under the Plan may be assigned, transferred, pledged or otherwise
disposed of in any way (other than by will, the laws of descent and distribution
or as provided in Section 14 hereof) by the participant. Any such attempt at
assignment, transfer, pledge or other disposition shall be without effect,
except that the Company may treat such act as an election to withdraw funds from
an Offering Period in accordance with Section 10 hereof.

     16. USE OF FUNDS. All payroll deductions received or held by the Company
under the Plan may be used by the Company for any corporate purpose, and the
Company shall not be obligated to segregate such payroll deductions.

     17. REPORTS. Individual accounts shall be maintained for each participant
in the Plan. Statements of account shall be given to participating Employees at
least annually, which statements shall set forth the amounts of payroll
deductions, the Purchase Price, the number of shares purchased and the remaining
cash balance, if any.

     18. ADJUSTMENTS UPON CHANGES IN CAPITALIZATION, DISSOLUTION, LIQUIDATION,
         MERGER OR ASSET SALE.

          (a) CHANGES IN CAPITALIZATION. The maximum number of shares of Common
Stock available for sale under the Plan, the Reserves, the maximum number of
shares each participant may purchase during each Purchase Period (pursuant to
Section 7), as well as the Purchase Price per share and the number of shares of
Common Stock covered by each option under the Plan which has not yet been
exercised, shall be proportionately adjusted for any increase or decrease in the
number of issued shares of Common Stock resulting from a stock split, reverse
stock



                                      -7-
<PAGE>   8

split, stock dividend, combination or reclassification of the Common Stock, or
any other increase or decrease in the number of shares of Common Stock effected
without receipt of consideration by the Company; provided, however, that
conversion of any convertible securities of the Company shall not be deemed to
have been "effected without receipt of consideration". Such adjustment shall be
made by the Board, whose determination in that respect shall be final, binding
and conclusive. Except as expressly provided herein, no issuance by the Company
of shares of stock of any class, or securities convertible into shares of stock
of any class, shall affect, and no adjustment by reason thereof shall be made
with respect to, the number or price of shares of Common Stock subject to an
option granted hereunder.

          (b) DISSOLUTION OR LIQUIDATION. In the event of the proposed
dissolution or liquidation of the Company, the Offering Periods shall terminate
immediately prior to the consummation of such proposed action, unless otherwise
provided by the Board.

          (c) REORGANIZATION EVENTS.

               (1) DEFINITION. A "Reorganization Event" shall mean: (a) any
merger or consolidation of the Company with or into another entity as a result
of which the Common Stock is converted into or exchanged for the right to
receive cash, securities or other property, (b) any exchange of shares of the
Company for cash, securities or other property pursuant to a share exchange
transaction, or (c) any sale of all or substantially all of the assets of the
Company, each while unexercised options remain outstanding under the Plan.

               (2) CONSEQUENCES OF A REORGANIZATION EVENT ON OPTIONS. Upon the
occurrence of a Reorganization Event, or the execution by the Company of any
agreement with respect to a Reorganization Event, the Board shall provide that
all outstanding options shall be assumed, or equivalent options shall be
substituted, by the acquiring or succeeding corporation (or an affiliate
thereof). For purposes hereof, an option shall be considered to be assumed if,
following consummation of the Reorganization Event, the option confers the right
to purchase, for each share of Common Stock subject to the option immediately
prior to the consummation of the Reorganization Event, the consideration
(whether cash, securities or other property) received as a result of the
Reorganization Event by holders of Common Stock for each share of Common Stock
held immediately prior to the consummation of the Reorganization Event (and if
holders were offered a choice of consideration, the type of consideration chosen
by the holders of a majority of the outstanding shares of Common Stock);
provided, however, that if the consideration received as a result of the
Reorganization Event is not solely common stock of the acquiring or succeeding
corporation (or an affiliate thereof), the Company may, with the consent of the
acquiring or succeeding corporation, provide for the consideration to be
received upon the exercise of options to consist solely of common stock of the
acquiring or succeeding corporation (or an affiliate thereof) equivalent in fair
market value to the per share consideration received by holders of outstanding
shares of Common Stock as a result of the Reorganization Event.

     Notwithstanding the foregoing, in the event that the acquiring or
succeeding corporation refuses to assume, or substitute for, the options, any
Offering Periods then in progress shall be



                                      -8-
<PAGE>   9

shortened by setting a new Exercise Date (the "New Exercise Date"), determined
by the Board. The New Exercise Date shall be before the date of the proposed
Reorganization Event. The Board shall notify each participant in writing at
least ten (10) business days prior to the New Exercise Date that the Exercise
Date for the participant's option has been changed to the New Exercise Date and
that the participant's option shall be exercised automatically on the New
Exercise Date, unless prior to such date the participant has withdrawn from the
Offering Period as provided in Section 10 hereof.

     19. AMENDMENT OR TERMINATION.

          (a) The Board of Directors of the Company may at any time and for any
reason terminate or amend the Plan. Except as provided in Section 18 hereof, no
such termination can affect options previously granted, provided that an
Offering Period may be terminated by the Board on any Exercise Date if the Board
determines that the termination of the Plan is in the best interests of the
Company and its stockholders. Except as provided in Section 18 hereof, no
amendment may make any change in any option theretofore granted which adversely
affects the rights of any participant. To the extent necessary to comply with
Section 423 of the Code (or any successor rule or provision or any other
applicable law or regulation), the Company shall obtain stockholder approval in
such a manner and to such a degree as required.

          (b) Without stockholder consent and without regard to whether any
participant rights may be considered to have been "adversely affected," the
Board (or its committee) shall be entitled to change the Offering Periods, limit
the frequency and/or number of changes in the amount withheld during an Offering
Period, establish the exchange ratio applicable to amounts withheld in a
currency other than U.S. dollars, permit payroll withholding in excess of the
amount designated by a participant in order to adjust for delays or mistakes in
the Company's processing of properly completed withholding elections, establish
reasonable waiting and adjustment periods and/or accounting and crediting
procedures to ensure that amounts applied toward the purchase of Common Stock
for each participant properly correspond with amounts withheld from the
participant's Compensation and establish such other limitations or procedures as
the Board (or its committee) determines in its sole discretion advisable which
are consistent with the Plan.

     20. NOTICES. All notices or other communications by a participant to the
Company under or in connection with the Plan shall be deemed to have been duly
given when received in the form specified by the Company at the location, or by
the person, designated by the Company for the receipt thereof.

     21. CONDITIONS UPON ISSUANCE OF SHARES. Shares shall not be issued with
respect to an option unless the exercise of such option and the issuance and
delivery of such shares pursuant thereto shall comply with all applicable
provisions of law, domestic or foreign, including, without limitation, the
Securities Act of 1933, as amended, the Securities Exchange Act of 1934, as
amended, the rules and regulations promulgated thereunder, and the requirements
of any stock exchange upon which the shares may then be listed, and shall be
further subject to the approval of counsel for the Company with respect to such
compliance.




                                      -9-
<PAGE>   10

     22. EFFECTIVE DATE. The Plan shall become effective upon the effectiveness
of a registration statement filed by the Company pursuant to the Securities Act
of 1933, as amended, with the Securities and Exchange Commission for an initial
public offering of shares of Common Stock, provided, however, that the Plan
shall not become effective prior to the earlier to occur of its adoption by the
Board of Directors or its approval by the stockholders of the Company.

     23. AUTOMATIC TRANSFER TO LOW PRICE OFFERING PERIOD. To the extent
permitted by any applicable laws, regulations, or rules of the established stock
exchange, national market system, or over-the-counter market on which the Common
Stock trades, if the Fair Market Value of the Common Stock on the Enrollment
Date of the next Offering Period is lower than the Fair Market Value of the
Common Stock on the Enrollment Date of any current Offering Period, then all
participants in such current Offering Period shall be automatically withdrawn
from such Offering Period immediately after the exercise of their option on the
Exercise Date and shall be automatically re-enrolled in the next Offering Period
as of the first day thereof.

     24. GOVERNMENTAL REGULATIONS. The Company's obligation to sell and deliver
Common Stock under this Plan is subject to listing on an established stock
exchange or quotation on a national market system or an over the counter market
(to the extent the Common Stock is then so listed or quoted) and the approval of
all governmental authorities required in connection with the authorization,
issuance, or sale of such stock.

     25. SPECIAL PROVISIONS FOR FIRST PLAN PERIOD. The following provisions of
this Section 25 shall apply with respect to the first Purchase Period of the
First Offering Period (the "First Plan Period") notwithstanding any provision of
the Plan to the contrary:

          (a) Every eligible Employee shall automatically become a participant
in the Plan for the First Plan Period at the highest percentage of Compensation
permitted under Section 6. No payroll deductions shall be required for the First
Plan Period; however, a participant may, at any time after the effectiveness of
the Plan's Registration Statement on Form S-8, elect to have payroll deductions
up to the aggregate amount which would have been credited to his or her account
if a deduction of twenty percent (20%) of the Compensation which he or she
received on each pay day during the First Plan Period had been made (the
"Maximum Amount") or decline to participate by filing an appropriate
subscription agreement.

          (b) Upon the automatic exercise of a participant's option on the
Exercise Date for the First Plan Period, a participant shall be permitted to
purchase shares with (i) the accumulated payroll deductions in his or her
account, if any, (ii) a direct payment from the participant, or (iii) a
combination thereof; provided, however that the total amount applied to the
purchase may not exceed the Maximum Amount.

     26. GOVERNING LAW. The Plan shall be governed by Delaware law except to the
extent that such law is preempted by federal law.



                                      -10-
<PAGE>   11


     27. SOURCE OF SHARES. Shares may be issued upon exercise of an option from
authorized but unissued Common Stock, from shares held in the treasury of the
Company, or from any other proper source.

     28. NOTIFICATION UPON SALE OF SHARES. Each employee agrees, by
participating in the Plan, to promptly give notice to the Company of any
disposition of shares purchased under the Plan where such disposition occurs
within two years after the date of the grant of the option pursuant to which
such shares were purchased or within one year of the date of exercise of such
option pursuant to which such shares were purchased.







                                      -11-

<PAGE>   12



                                    EXHIBIT A


                       QUANTUM BRIDGE COMMUNICATIONS, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN

                             SUBSCRIPTION AGREEMENT



_____ Original Application                         Enrollment Date: ___________
_____ Change in Payroll Deduction Rate
_____ Change of Beneficiary(ies)
_____ Decline Participation


1. ___________________________________________hereby elects to participate in
the Quantum Bridge Communications, Inc. 2000 Employee Stock Purchase Plan (the
"Employee Stock Purchase Plan") and subscribes to purchase shares of the
Company's Common Stock in accordance with this Subscription Agreement and the
Employee Stock Purchase Plan.

2. I hereby authorize payroll deductions from each paycheck in the amount of
____% (1 to 20%) of my Compensation on each payday during the Offering Period in
accordance with the 2000 Employee Stock Purchase Plan. (Please note that no
fractional percentages are permitted.)

3. I understand that said payroll deductions shall be accumulated for the
purchase of shares of Common Stock at the applicable Purchase Price determined
in accordance with the 2000 Employee Stock Purchase Plan. I understand that if I
do not withdraw from an Offering Period, any accumulated payroll deductions will
be used to automatically exercise my option on each Exercise Date.

4. I have received a copy of the complete Employee Stock Purchase Plan. I
understand that my participation in the 2000 Employee Stock Purchase Plan is in
all respects subject to the terms of the Plan.

5. Shares purchased for me under the 2000 Employee Stock Purchase Plan should be
issued in the name(s) of (Employee or Employee and Spouse
only):______________________.

6. I hereby agree that if I dispose of any shares received by me pursuant to the
Plan within 2 years after the Enrollment Date (the first day of the Offering
Period during which I purchased such shares) or one year after the Exercise Date
on which I purchased such shares, I will notify the Company in writing within 30
days after the date of any disposition of my shares.



                                      -1-
<PAGE>   13

7. I hereby agree to be bound by the terms of the Employee Stock Purchase Plan.
The effectiveness of this Subscription Agreement is dependent upon my
eligibility to participate in the 2000 Employee Stock Purchase Plan.

8. In the event of my death, I hereby designate the following as my
beneficiary(ies) to receive all payments and shares due me under the Employee
Stock Purchase Plan:


BENEFICIARY:

NAME:
(Please print)
               -----------------------------------------------------
                   (First)         (Middle)               (Last)

--------------------------------     ------------------------------
Relationship                                         Percentage

--------------------------------------------
Address

SECONDARY BENEFICIARY
NAME:
(Please print)
              -------------------------------------------------------
                   (First)         (Middle)               (Last)

------------------------------      -------------------------------
Relationship                                         Percentage

--------------------------------------------
Address


Employee's Social
Security Number:
                 ---------------------------


Employee's Address:

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

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




                                      -2-
<PAGE>   14



I UNDERSTAND THAT THIS SUBSCRIPTION AGREEMENT SHALL REMAIN IN EFFECT THROUGHOUT
SUCCESSIVE OFFERING PERIODS UNLESS TERMINATED BY ME.



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

      ----------------------------------
      Signature of Employee


      --------------------------------------------------------
      Spouse's Signature (If beneficiary other than spouse)






                                      -3-
<PAGE>   15


                                    EXHIBIT B


                       QUANTUM BRIDGE COMMUNICATIONS, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN

                              NOTICE OF WITHDRAWAL



     The undersigned participant in the Offering Period of the Quantum Bridge
Communications, Inc. 2000 Employee Stock Purchase Plan which began on
_________________ (the "Enrollment Date") hereby notifies the Company that he or
she hereby withdraws from the Offering Period. He or she hereby directs the
Company to pay to the undersigned as promptly as practicable all the payroll
deductions credited to his or her account with respect to such Offering Period.
The undersigned understands and agrees that his or her option for such Offering
Period will be automatically terminated. The undersigned understands further
that no further payroll deductions will be made for the purchase of shares in
the current Offering Period and the undersigned shall be eligible to participate
in succeeding Offering Periods only by delivering to the Company a new
Subscription Agreement.

         Name and Address of Participant:

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

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

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


         Signature:


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


         Date:
              ---------------------------





                                      -4-