<PAGE>   1

                                                                   EXHIBIT 10.15


                     EARLY EXERCISE STOCK PURCHASE AGREEMENT
                       (INCLUDING RIGHT OF FIRST REFUSAL)

        THIS AGREEMENT is made by and between Vixel Corporation, a Delaware
corporation (the "Corporation"), and Kurtis L. Adams ("Purchaser").

        NOW, THEREFORE, IT IS AGREED between the parties as follows:

        1. Purchaser hereby agrees to purchase from the Corporation, and the
Corporation hereby agrees to sell to Purchaser, an aggregate of one hundred
eighty-one thousand six hundred two (181,602) shares of the common stock (the
"Stock") of the Corporation, for an exercise price of $2.05 per share. The
closing hereunder shall occur at the offices of the Corporation on the date of
this Agreement or at such other time and place as the parties may mutually agree
upon in writing. At the closing, Purchaser shall deliver three (3) stock
assignments in the form of Exhibit B, duly endorsed (with date and number of
shares left blank), joint escrow instructions (the "Joint Escrow Instructions")
in the form of Exhibit C, duly executed by Purchaser, and the total exercise
price (including endorsed certificates representing the appropriate number of
shares of the Corporation's common stock if a portion of the total exercise
price is to be paid by common stock). At the closing or as soon thereafter as
practicable, the Corporation shall deliver to the Escrow Agent (as defined in
paragraph 10 below) share certificates for all of the Stock that is to be
subject to the Purchase Option (as defined in paragraph 2 below), and shall
deliver share certificates to Purchaser for all of the Stock, if any, that is
not to be subject to the Purchase Option. Upon the request of Purchaser during
the term of the escrow, certificates for shares that are no longer subject to
the Purchase Option shall be delivered to Purchaser.

        2. The Stock to be purchased by Purchaser pursuant to this Agreement
shall be subject to the following option ("Purchase Option"):

               (a) In the event that Purchaser shall cease to be an employee of
the Corporation for any reason (including his death), or no reason, with or
without cause, the Purchase Option may be exercised. The Corporation shall have
the right at any time within ninety (90) days after such cessation of employment
to purchase from Purchaser or his personal representative, as the case may be,
at the price per share paid by Purchaser pursuant to this Agreement ("Option
Price"), up to but not exceeding the number of unvested shares of the Stock set
forth on Exhibit A hereto which is incorporated herein by this reference.

               (b) In addition, and without limiting the foregoing Purchase
Option, if at any time during the term of the Purchase Option, there is a change
of control of the Company or a change in responsibilities (as set forth in the
offer letter dated August 20, 1998) (the "Employment Agreement"), then the
Purchase Option shall be terminated as to the number of shares subject to
accelerated vesting pursuant to such agreement.

               (c) The Corporation shall be entitled to pay for any shares
purchased pursuant to its Purchase Option, at the Corporation's option, in cash,
by offset against any indebtedness owing to the Corporation by Purchaser,
including, without limitation, any note given in payment for the Stock, or a
combination of both.

        3. The Purchase Option may be exercised by giving written notice of
exercise delivered or mailed as provided in paragraph 15 below. Upon providing
of such notice and



<PAGE>   2

payment or tender of the purchase price, the Corporation shall become the legal
and beneficial owner of the Stock being purchased and all rights and interests
therein or related thereto.

        4. If from time to time during the term of the Purchase Option there is
any stock dividend or liquidating dividend or distribution of cash and/or
property, stock split or other change in the character or amount of any of the
outstanding securities of the Corporation, then, in such event, any and all new,
substituted or additional securities or other property to which Purchaser is
entitled by reason of his ownership of Stock will be immediately subject to the
Purchase Option and be included in the word "Stock" for all purposes of the
Purchase Option with the same force and effect as the shares of Stock then
subject to the Purchase Option. While the total Option Price shall remain the
same after each such event, the Option Price per share of Stock upon exercise of
the Purchase Option shall be appropriately adjusted.

        5. [INTENTIONALLY DELETED.]

        6. CORPORATION'S RIGHT OF FIRST REFUSAL.

        (a) Subject to the limitations of subparagraph 6(b), in the event that,
prior to the date of the first registration of an equity security of the
Corporation under Section 12 of the Securities Exchange Act of 1934, Purchaser
desires to sell, encumber or otherwise transfer all or any portion of the Stock
received upon the exercise of Purchaser's Option, or any interest therein,
Purchaser will be required to first give written notice of the intent to
transfer to the Secretary of the Corporation. The notice will name the proposed
transferee and state the number of shares of Stock to be transferred, the
proposed consideration, and all other terms and conditions of the proposed
transfer. The Corporation and/or its assignee(s) will have the right (the "Right
of First Refusal") at any time within thirty (30) days after receipt of such
notice to purchase any portion of the Stock specified in the notice at the price
and upon the terms set forth in such notice (the "Notice Price"). In the case of
a gift, property settlement or other transfer in which the proposed transferee
is not paying the full price for the shares, the price will be deemed to be the
fair market value of the Stock at such time as determined in good faith by the
Board of Directors. In the event the Corporation and/or its assignee(s) elects
to purchase all or any portion of the Stock, it will provide Purchaser with
written notice of its election and cash payment at the Notice Price within
thirty (30) days after receipt of the transfer notice. If, however, the terms of
payment set forth in the transfer notice were other than cash against delivery,
the Corporation and/or its assignee(s) will pay for the Stock on the same terms
and conditions as set forth in the transfer notice. In the event the Corporation
and/or its assignee(s) do not elect to acquire all of the shares specified in
the transfer notice, Purchaser may, within the sixty (60)-day period following
the expiration of the Corporation's Right of First Refusal, transfer any portion
of the Stock specified in the notice which was not acquired by the Corporation
and/or its assignee(s) on the terms specified in the original notice. All shares
so sold by Purchaser will continue to be subject to the same restrictions as
before the transfer.

        (b) The following transactions shall be exempt from the provisions of
subparagraph 6(a): (i) Purchaser's transfer of any or all shares held either
during such Purchaser's lifetime or on death by will or intestacy to such
Purchaser's immediate family or to any custodian or trustee for the account of
such Purchaser or such Purchaser's immediate family and (ii) Purchaser's bona
fide pledge or mortgage of any shares with a commercial lending institution,
provided that any subsequent transfer of said shares to said institution shall
be conducted in the manner set forth in



<PAGE>   3

this Agreement. "Immediate family" as used herein shall mean spouse, lineal
descendant, father, mother, brother, or sister of the Purchaser making such
transfer;

        In any case, the transferee, assignee, or other recipient shall receive
and hold such Stock subject to the provisions of this Agreement, and there shall
be no further transfer of such Stock except in accord with this Agreement.

        7. All certificates representing any shares of Stock of the Corporation
subject to the provisions of this Agreement shall have endorsed thereon legends
in substantially the following form:

                      (i) "The shares represented by this certificate are
subject to an option and a right of first refusal set forth in an agreement
between the corporation and the registered holder, or his predecessor in
interest, a copy of which is on file at the principal office of this
corporation. Any transfer or attempted transfer of any shares subject to such
option is void without the prior express written consent of the issuer of these
shares."

                      (ii) "These securities have not been registered under the
Securities Act of 1933. They may not be sold, offered for sale, pledged or
hypothecated in the absence of an effective registration statement as to the
securities under said Act or an opinion of counsel satisfactory to the
corporation that such registration is not required."

        8. Purchaser acknowledges that he is aware that the Stock to be issued
to him by the Corporation pursuant to this Agreement has not been registered
under the Securities Act of 1933, as amended (the "Act"), on the basis that no
distribution or public offering of the Stock is to be effected, and in this
connection acknowledges that the Corporation is relying on the following
representations. In this connection, Purchaser warrants and represents to the
Corporation that he is acquiring the Stock for investment and not with a view to
or for sale in connection with any distribution of the Stock or with any present
intention of distributing or selling the Stock and he does not presently have
reason to anticipate any change in circumstances or any particular occasion or
event which would cause him to sell the Stock. Purchaser recognizes that the
Stock must be held indefinitely unless it is subsequently registered under the
Act or an exemption from such registration is available and, further, recognizes
that the Corporation is under no obligation to register the Stock or to comply
with any exemption from such registration.



        9. Purchaser is aware that the Stock may not be sold pursuant to Rule
144 adopted under the Act unless certain conditions are met and until Purchaser
has held the Stock for at least one (1) year. Among the conditions for use of
Rule 144 is the availability of specified current public information about the
Corporation. Purchaser recognizes that the Corporation presently has no plans to
make such information available to the public. Whether or not the Purchase
Option is exercised or has lapsed, Purchaser further agrees not to make any
disposition of any of the Stock in any event unless and until: (a) There is then
in effect a registration statement under the Act covering such proposed
disposition and such disposition is made in accordance with such registration
statement; or (b) (i) Purchaser shall have notified the Corporation of the
proposed disposition and shall have furnished the Corporation with a detailed
statement of the circumstances surrounding the proposed disposition, and (ii)
Purchaser shall have given the Corporation an opinion of counsel, which opinion
and counsel shall be satisfactory to the Corporation, to the effect that such
disposition will not require registration of the Stock under the Act.



<PAGE>   4

        10. As security for his faithful performance of the terms of this
Agreement and to insure the availability for delivery of Purchaser's Stock upon
exercise of the Purchase Option herein provided for, Purchaser agrees, at the
closing hereunder (or as soon thereafter as practicable), to deliver (or have
the Corporation deliver on the Purchaser's behalf) to and deposit with the
Secretary of the Corporation ("Escrow Agent"), as Escrow Agent in this
transaction, three (3) stock assignments duly endorsed (with date and number of
shares left blank) in the form attached hereto as Exhibit B, together with a
certificate or certificates evidencing all of the Stock subject to the Purchase
Option; said documents are to be held by the Escrow Agent and delivered by said
Escrow Agent pursuant to the Joint Escrow Instructions of the Corporation and
Purchaser set forth in Exhibit C attached hereto and incorporated herein by this
reference, which instructions shall also be delivered to the Escrow Agent at the
closing hereunder (or as soon thereafter as practicable).

        11. Except for transfers permitted pursuant to Section 9 of the Option
Agreement, purchaser shall not sell or transfer any of the Stock subject to the
Purchase Option or any interest therein so long as such Stock is subject to the
Purchase Option.

        12. The Corporation shall not be required (i) to transfer on its books
any shares of Stock of the Corporation which shall have been sold or transferred
in violation of any of the provisions set forth in this Agreement or (ii) to
treat as owner of such shares or to accord the right to vote as such owner or to
pay dividends to any transferee to whom such shares shall have been so
transferred.

        13. Subject to the provisions of paragraphs 11 and 12 above, Purchaser
(but not any unapproved transferee) shall, during the term of this Agreement,
exercise all rights and privileges of a stockholder of the Corporation with
respect to the Stock.

        14. The parties agree to execute such further instruments and to take
such further action as reasonably may be necessary to carry out the intent of
this Agreement.

        15. Any notice required or permitted hereunder shall be given in writing
and shall be deemed effectively given upon personal delivery or upon deposit in
any United States Post Office Box, by registered or certified mail with postage
and fees prepaid, addressed to the other party hereto at his address hereinafter
shown below his signature or at such other address as such party may designate
by ten (10) days' advance written notice to the other party hereto.

        16. This Agreement shall bind and inure to the benefit of the successors
and assigns of the Corporation and, subject to the restrictions on transfer
herein set forth, inure to the benefit of and be binding upon Purchaser, his
heirs, executors, administrators, successors, and assigns. Without limiting the
generality of the foregoing, the Purchase Option of the Corporation hereunder
shall be assignable by the Corporation at any time or from time to time, in
whole or in part.



<PAGE>   5

        IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the 20th day of May, 1999.

                                       VIXEL CORPORATION

                                       By: /s/ Kurtis L. Adams
                                           -------------------------------------
                                       Title: Chief Financial Officer

                                              11911 Northcreek Parkway South
                                              Suite 100
                                              Bothell, WA 98011

                                       PURCHASER

                                       /s/ Kurtis L. Adams
                                       -----------------------------------------
                                       Name:  Kurtis L. Adams



<PAGE>   6

                                    EXHIBIT A
                                       TO
                          NONSTATUTORY OPTION AGREEMENT
                                     VESTING

<TABLE>
<CAPTION>
                    Number of       Number of       Number of       Number of      Total Number
                  Vested Shares   Vested Shares   Vested Shares   Vested Shares     of Vested
Date of Vesting    Option #482     Option #483     Option #498     Option #499        Shares
<S>               <C>             <C>             <C>             <C>              <C>
    11/2/99                                           43,750                          43,750
    12/2/99                                           3,646                           47,396
     1/2/00                                           3,646                           51,042
     2/2/00                                           3,646                           54,688
     3/2/00                                           3,646                           58,334
     4/2/00                                           3,646                           61,980
    4/21/00            3352            9148                                           74,480
     5/2/00                                           3,646                           78,126
     6/2/00                                           3,646                           81,772
     7/2/00                                           3,646                           85,418
    7/21/00            838             2287                                           88,543
     8/2/00                                           3,646                           92,189
     9/2/00                                           3,646                           95,835
    10/2/00                                           3,646                           99,481
    10/21/00           838             2287                                          102,606
    11/2/00                                           3,646                          106,252
    12/2/00                                           3,646                          109,898
     1/2/01                                           3,646                          113,544
    1/21/01            736             2388                                          116,668
     2/2/01                                           3,646                          120,314
     3/2/01                                           3,646                          123,960
     4/2/01                                           3,646                          127,606
    4/21/01            736             2389                                          130,731
     5/2/01                                           3,646                          134,377
     6/2/01                                           3,646                          138,023
     7/2/01                                           3,646                          141,669
    7/21/01            736             2389                                          144,794
     8/2/01                                           3,646                          148,440
     9/2/01                                           3,646                          152,086
    10/2/01                                           3,646                          155,732
    10/21/01           737             2389                                          158,858
    11/2/01                                           3,646                          162,504
    12/2/01                                           5,729                          168,233
     1/2/02                                                            1294          169,527
    1/21/02                            3124                                          172,651
     2/2/02                                                            1294          173,945
     3/2/02                                                            1295          175,240
</TABLE>


<PAGE>   7

<TABLE>
<CAPTION>
                    Number of       Number of       Number of       Number of      Total Number
                  Vested Shares   Vested Shares   Vested Shares   Vested Shares     of Vested
Date of Vesting    Option #482     Option #483     Option #498     Option #499        Shares
<S>               <C>             <C>             <C>             <C>              <C>
     4/2/02                                                            1294          176,534
    4/21/02                            3125                                          179,659
     5/2/02                                                            1294          180,953
     6/2/02                                                            648           181,601
     7/2/02                                                                          181,601
    7/21/02                             1                                            181,602
</TABLE>




<PAGE>   8

                                    EXHIBIT B

                      ASSIGNMENT SEPARATE FROM CERTIFICATE

        FOR VALUE RECEIVED and pursuant to that certain Early Exercise Stock
Purchase Agreement (the "Agreement") dated as of May 20, 1999, Kurtis L. Adams
hereby sells, assigns and transfers unto Vixel Corporation, a Delaware
corporation (the "Corporation") _________________ (__________) shares of Common
Stock of the Corporation standing in the undersigned's name on the books of the
Corporation represented by Certificate No. _____ herewith, and does hereby
irrevocably constitute and appoint the Secretary of the Corporation attorney to
transfer the said stock on the books of the Corporation with full power of
substitution in the premises. This Assignment may be used only in accordance
with and subject to the terms and conditions of the Agreement, in connection
with the repurchase of shares of Common Stock issued to the undersigned pursuant
to the Agreement, and only to the extent that such shares remain subject to the
Company's Purchase Option under the Agreement.

Dated:  May 20, 1999                        /s/ Kurtis L. Adams
                                            ------------------------------------
                                                 [Signature]

                                                 Kurtis L. Adams



<PAGE>   9

                                    EXHIBIT C

                            JOINT ESCROW INSTRUCTIONS

Vixel Corporation
Attention:  Secretary

Dear Sir:

        As Escrow Agent for both Vixel Corporation, a Delaware corporation (the
"Company"), and the undersigned purchaser of stock of the Company ("Purchaser"),
you are hereby authorized and directed to hold the documents delivered to you
pursuant to the terms of that certain Early Exercise Stock Purchase Agreement
(the "Agreement"), dated May 20, 1999, to which a copy of these Joint Escrow
Instructions is attached as Exhibit B, in accordance with the following
instructions:

        1. In the event the Company or an assignee shall elect to exercise the
Purchase Option set forth in the Agreement, the Company or its assignee will
give to Purchaser and you a written notice specifying the number of shares of
stock to be purchased, the purchase price, and the time for a closing hereunder
at the principal office of the Company. Purchaser and the Company hereby
irrevocably authorize and direct you to close the transaction contemplated by
such notice in accordance with the terms of said notice.

        2. At the closing you are directed (a) to date any stock assignments
necessary for the transfer in question, (b) to fill in the number of shares
being transferred, and (c) to deliver same, together with the certificate
evidencing the shares of stock to be transferred, to the Company against the
simultaneous delivery to you of the purchase price (which may include suitable
acknowledgment of cancellation of indebtedness) of the number of shares of stock
being purchased pursuant to the exercise of the Purchase Option.

        3. Purchaser irrevocably authorizes the Company to deposit with you any
certificates evidencing shares of stock to be held by you hereunder and any
additions and substitutions to said shares as specified in the Agreement.
Purchaser hereby irrevocably constitutes and appoints you as his
attorney-in-fact and agent for the term of this escrow to execute with respect
to such securities and other property all documents of assignment and/or
transfer and all stock certificates necessary or appropriate to make all
securities negotiable and complete any transaction herein contemplated.

        4. This escrow shall terminate upon expiration or closing of the
exercise of the Purchase Option, whichever occurs first.

        5. If at the time of termination of this escrow you should have in your
possession any documents, securities, or other property belonging to Purchaser,
you shall deliver all of same to Purchaser and shall be discharged of all
further obligations hereunder; provided, however, that if at the time of
termination of this escrow you are advised by the Company that the property



<PAGE>   10

subject to this escrow is the subject of a pledge or other security agreement,
you shall deliver all such property to the pledgeholder or other person
designated by the Company.

        6. Except as otherwise provided in these Joint Escrow Instructions, your
duties hereunder may be altered, amended, modified or revoked only by a writing
signed by all of the parties hereto.

        7. You shall be obligated only for the performance of such duties as are
specifically set forth herein and may rely and shall be protected in relying or
refraining from acting on any instrument reasonably believed by you to be
genuine and to have been signed or presented by the proper party or parties or
their assignees. You shall not be personally liable for any act you may do or
omit to do hereunder as Escrow Agent or as attorney-in-fact for Purchaser while
acting in good faith, and any act done or omitted by you pursuant to the advice
of your own attorneys shall be conclusive evidence of such good faith.

        8. You are hereby expressly authorized to disregard any and all warnings
given by any of the parties hereto or by any other person or corporation,
excepting only orders or process of courts of law, and are hereby expressly
authorized to comply with and obey orders, judgments or decrees of any court. In
case you obey or comply with any such order, judgment or decree of any court,
you shall not be liable to any of the parties hereto or to any other person,
firm or corporation by reason of such compliance, notwithstanding any such
order, judgment or decree being subsequently reversed, modified, annulled, set
aside, vacated or found to have been entered without jurisdiction.

        9. You shall not be liable in any respect on account of the identity,
authority or rights of the parties executing or delivering or purporting to
execute or deliver the Agreement or any documents or papers deposited or called
for hereunder.

        10. You shall not be liable for the outlawing of any rights under any
statute of limitations with respect to these Joint Escrow Instructions or any
documents deposited with you.

        11. You shall be entitled to employ such legal counsel (including,
without limitation, the firm of Cooley Godward LLP) and other experts as you may
deem necessary properly to advise you in connection with your obligations
hereunder, may rely upon the advice of such counsel, and may pay such counsel
reasonable compensation therefor.

        12. Your responsibilities as Escrow Agent hereunder shall terminate if
you shall cease to be Secretary of the Company or if you shall resign by written
notice to each party. In the event of any such termination, the Company may
appoint any officer or assistant officer of the Company as successor Escrow
Agent and Purchaser hereby confirms the appointment of such successor or
successors as his attorney-in-fact and agent to the full extent of your
appointment.

        13. If you reasonably require other or further instruments in connection
with these Joint Escrow Instructions or obligations in respect hereto, the
necessary parties hereto shall join in furnishing such instruments.



<PAGE>   11

        14. It is understood and agreed that should any dispute arise with
respect to the delivery and/or ownership or right of possession of the
securities, you may (but are not obligated to) retain in your possession without
liability to anyone all or any part of said securities until such dispute shall
have been settled either by mutual written agreement of the parties concerned or
by a final order, decree or judgment of a court of competent jurisdiction after
the time for appeal has expired and no appeal has been perfected, but you shall
be under no duty whatsoever to institute or defend any such proceedings.

        15. Any notice required or permitted hereunder shall be given in writing
and shall be deemed effectively given upon personal delivery or upon deposit in
any United States Post Office Box, by registered or certified mail with postage
and fees prepaid, addressed to each of the other parties hereunto entitled at
the following addresses specified below, or at such other addresses as a party
may designate by ten days' written notice to each of the other parties hereto:

        16. By signing these Joint Escrow Instructions you become a party hereto
only for the purpose of said Joint Escrow Instructions; you do not become a
party to the Agreement.

        17. This agreement will be governed by, and construed in accordance
with, the internal laws (excluding the law of conflicts) of the State of
Delaware.


<PAGE>   12

        18. This instrument shall be binding upon and inure to the benefit of
the parties hereto and their respective successors and permitted assigns. It is
understood and agreed that references to "you" or "your" herein refer to the
original Escrow Agent and to any and all successor Escrow Agents. It is
understood and agreed that the Company may at any time or from time to time
assign its rights under the Agreement and these Joint Escrow Instructions in
whole or in part.



                                       Very truly yours,

                                       VIXEL CORPORATION

                                       By: /s/ Kurtis L. Adams
                                           -------------------------------------
                                           Name: Kurtis L. Adams
                                           Title: Chief Financial Officer

                                        PURCHASER:

                                        /s/ Kurtis L. Adams
                                        ----------------------------------------
                                        KURTIS L. ADAMS

ESCROW AGENT:

Secretary

Address:

11911 Northcreek Parkway South
Bothell, Washington  98011