<PAGE>
                                                                   Exhibit 10.38

                             STOCK PLEDGE AGREEMENT

     This STOCK PLEDGE AGREEMENT ("Pledge Agreement") is made and entered into
as of April 3, 2001, by JOSEPH Y. LIU ("Pledgor") in favor of OPLINK
COMMUNICATIONS, INC., a Delaware corporation ("Oplink" or "Pledgee").

                                    RECITALS

     WHEREAS, Pledgor executed that certain Promissory Note (the "Note") in
favor of Pledgee in the amount of $3,657,500, secured by an escrow comprising
all of the shares of Oplink common stock covered by the stock options granted to
the undersigned by Oplink;

     Whereas, pursuant to the escrow arrangement, all of the vested shares that
have been purchased by the Pledgor shall be pledged by Pledgor in favor of
Pledgee pursuant to this Stock Pledge Agreement and, if the undersigned elects
to purchase any more of the vested shares, the shares so purchased shall be
likewise pledged; and

     Whereas, Pledgor has purchased 2,216,666 of the vested shares.

                                    AGREEMENT

     NOW, THEREFORE, in consideration of the foregoing recitals and for other
good and valuable consideration, the receipt and adequacy of which are hereby
acknowledged, and intending to be legally bound, Pledgor hereby agrees as
follows:

     1.   As security for the full, prompt and complete payment and performance
when due (whether by stated maturity, by acceleration or otherwise) of all
indebtedness of Pledgor to Pledgee created under the Note (all such indebtedness
being the "Liabilities"), together with, without limitation, the prompt payment
of all expenses, including, without limitation, reasonable attorneys' fees and
legal expenses, incidental to the collection of the Liabilities and the
enforcement or protection of Pledgee's lien in and to the collateral pledged
hereunder, Pledgor hereby pledges to Pledgee, and grants to Pledgee, a first
priority security interest in all of the following (collectively, the "Pledged
Collateral"):

          (a)  2,216,666 shares of Common Stock of Pledgee represented by
Certificate numbered C-_________ (the "Pledged Shares"), and all dividends,
cash, instruments, and other property or proceeds from time to time received,
receivable, or otherwise distributed in respect of or in exchange for any or all
of the Pledged Shares;

          (b)  all voting trust certificates held by Pledgor evidencing the
right to vote any Pledged Shares subject to any voting trust; and

Stock Pledge Agreement


                                   Page 1 of 4

<PAGE>

          (c)  all additional shares and voting trust certificates from time to
time acquired by Pledgor in any manner (which additional shares shall be deemed
to be part of the Pledged Shares), and the certificates representing such
additional shares, and all dividends, cash, instruments, and other property or
proceeds from time to time received, receivable, or otherwise distributed in
respect of or in exchange for any or all of such shares.

     The term "indebtedness" is used herein in its most comprehensive sense and
includes any and all advances, debts, obligations and Liabilities heretofore,
now or hereafter made, incurred or created, whether voluntary or involuntary and
whether due or not due, absolute or contingent, liquidated or unliquidated,
determined or undetermined, and whether recovery upon such indebtedness may be
or hereafter becomes unenforceable.

     2.   At any time, without notice, and at the expense of Pledgor, Pledgee in
its name or in the name of its nominee or of Pledgor may, but shall not be
obligated to: (1) collect by legal proceedings or otherwise all dividends
(except cash dividends other than liquidating dividends), interest, principal
payments and other sums now or hereafter payable upon or on account of said
Pledged Collateral; (2) enter into any extension, reorganization, deposit,
merger or consolidation agreement, or any agreement in any way relating to or
affecting the Pledged Collateral, and in connection therewith may deposit or
surrender control of such Pledged Collateral thereunder, accept other property
in exchange for such Pledged Collateral and do and perform such acts and things
as it may deem proper, and any money or property received in exchange for such
Pledged Collateral shall be applied to the indebtedness or thereafter held by it
pursuant to the provisions hereof; (3) insure, process and preserve the Pledged
Collateral; (4) cause the Pledged Collateral to be transferred to its name or to
the name of its nominee; (5) exercise as to such Pledged Collateral all the
rights, powers and remedies of an owner, except that so long as no default
exists under the Note or hereunder, Pledgor shall retain all voting rights as to
the Pledged Shares.

     3.   Pledgor agrees to pay prior to delinquency all taxes, charges, liens
and assessments against the Pledged Collateral, and upon the failure of Pledgor
to do so, Pledgee at its option may pay any of them and shall be the sole judge
of the legality or validity thereof and the amount necessary to discharge the
same.

     4.   At the option of Pledgee and without necessity of demand or notice,
all or any part of the indebtedness of Pledgor shall immediately become due and
payable irrespective of any agreed maturity, upon the happening of any of the
following events: (1) failure to keep or perform any of the terms or provisions
of this Pledge Agreement; (2) failure to pay any installment of principal or
interest on the Note when due; (3) the levy of any attachment, execution or
other process against the Pledged Collateral; or (4) the insolvency, commission
of an act of bankruptcy, general assignment for the benefit of creditors, filing
of any petition in bankruptcy or for relief under the provisions of Title 11 of
the United States Code of, by, or against Pledgor.

     5.   In the event of the nonpayment of any indebtedness when due, whether
by acceleration or otherwise, or upon the happening of any of the events
specified in the last preceding paragraph, Pledgee may then, or at any time
thereafter, at its election, apply, set off,

Stock Pledge Agreement


                                   Page 2 of 4

<PAGE>

collect or sell in one or more sales, or take such steps as may be necessary to
liquidate and reduce to cash in the hands of Pledgee in whole or in part, with
or without any previous demands or demand of performance or notice or
advertisement, the whole or any part of the Pledged Collateral in such order as
Pledgee may elect, and any such sale may be made either at public or private
sale at its place of business or elsewhere, or at any broker's board or
securities exchange, either for cash or upon credit or for future delivery;
provided, however, that if such disposition is at private sale, then the
purchase price of the Pledged Collateral shall be equal to the public market
price then in effect, or, if at the time of sale no public market for the
Pledged Collateral exists, then, in recognition of the fact that the sale of the
Pledged Collateral would have to be registered under the Securities Act of 1933
and that the expenses of such registration are commercially unreasonable for the
type and amount of collateral pledged hereunder, Pledgee and Pledgor hereby
agree that such private sale shall be at a purchase price mutually agreed to by
Pledgee and Pledgor or, if the parties cannot agree upon a purchase price, then
at a purchase price established by a majority of three independent appraisers
knowledgeable of the value of such collateral, one named by Pledgor within 10
days after written request by the Pledgee to do so, one named by Pledgee within
such 10 day period, and the third named by the two appraisers so selected, with
the appraisal to be rendered by such body within 30 days of the appointment of
the third appraiser. The cost of such appraisal, including all appraiser's fees,
shall be charged against the proceeds of sale as an expense of such sale.
Pledgee may be the purchaser of any or all Pledged Collateral so sold and hold
the same thereafter in its own right free from any claim of Pledgor or right of
redemption. Demands of performance, notices of sale, advertisements and presence
of property at sale are hereby waived, and Pledgee is hereby authorized to sell
hereunder any evidence of debt pledged to it. Any sale hereunder may be
conducted by any officer or agent of Pledgee.

     6.   The proceeds of the sale of any of the Pledged Collateral and all sums
received or collected by Pledgee from or on account of such Pledged Collateral
shall be applied by Pledgee to the payment of expenses incurred or paid by
Pledgee in connection with any sale, transfer or delivery of the Pledged
Collateral, to the payment of any other costs, charges, attorneys' fees or
expenses mentioned herein, and to the payment of the indebtedness or any part
hereof, all in such order and manner as Pledgee in its discretion may determine.
Pledgee shall then pay any balance to Pledgor.

     7.   Upon the transfer of all or any part of the indebtedness Pledgee may
transfer all or any part of the Pledged Collateral and shall be fully discharged
thereafter from all liability and responsibility with respect to such Pledged
Collateral so transferred, and the transferee shall be vested with all the
rights and powers of Pledgee hereunder with respect to such Pledged Collateral
so transferred; but with respect to any Pledged Collateral not so transferred
Pledgee shall retain all rights and powers hereby given.

     8.   Until all indebtedness shall have been paid in full the power of sale
and all other rights, powers and remedies granted to Pledgee hereunder shall
continue to exist and may be exercised by Pledgee at any time and from time to
time irrespective of the fact that the

Stock Pledge Agreement


                                   Page 3 of 4

<PAGE>

indebtedness or any part thereof may have become barred by any statute of
limitations, or that the personal liability of Pledgor may have ceased.

     9.   Pledgee agrees that so long as no default exists under the Note or
hereunder, the Pledged Shares shall, upon the request of Pledgor, be released
from pledge as the indebtedness is paid. Such releases shall be at the
proportional rate of principal amount of indebtedness paid. Release from pledge,
however, shall not result in release from the provisions of those certain Joint
Escrow Instructions, if any, of even date herewith among the parties to this
Pledge Agreement and the Escrow Agent named therein.

     10.  Pledgee may at any time deliver the Pledged Collateral or any part
thereof to Pledgor and the receipt of Pledgor shall be a complete and full
acquittance for the Pledged Collateral so delivered, and Pledgee shall
thereafter be discharged from any liability or responsibility therefor.

     11.  The rights, powers and remedies given to Pledgee by this Pledge
Agreement shall be in addition to all rights, powers and remedies given to
Pledgee by virtue of any statute or rule of law. Any forbearance or failure or
delay by Pledgee in exercising any right, power or remedy hereunder shall not be
deemed to be a waiver of such right, power or remedy, and any single or partial
exercise of any right, power or remedy hereunder shall not preclude the further
exercise thereof; and every right, power and remedy of Pledgee shall continue in
full force and effect until such right, power or remedy is specifically waived
by an instrument in writing executed by Pledgee.

     12.  If any provision of this Pledge Agreement is held to be unenforceable
for any reason, it shall be adjusted, if possible, rather than voided in order
to achieve the intent of the parties to the extent possible. In any event, all
other provisions of this Pledge Agreement shall be deemed valid and enforceable
to the full extent possible.

     13.  This Pledge Agreement shall be governed by, and construed in
accordance with, the laws of the State of California.

                           PLEDGOR:


                           ----------------------------------------------------
                           JOSEPH Y. LIU



                           ACCEPTED AND AGREED TO BY:

                           OPLINK COMMUNICATIONS, INC.


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



                           DIRECTOR'S SIGNATURE


                           ----------------------------------------------------
                           NAME OF DIRECTOR AND TITLE

Stock Pledge Agreement


                                   Page 4 of 4