<PAGE>

                                                                     EXHIBIT 4.1


                                  Tycom Ltd.


   TyCom Ltd (the "Company") will furnish without charge to each shareholder who
so requests a copy of the powers, designations, preferences and relative,
participating, optional or other special rights of each class of shares or
series thereof, and the qualifications, limitations, or restrictions of such
preferences and/or rights.

   Keep this Certificate in a safe place. If it is lost, stolen or destroyed,
the Company may require presentation of satisfactory evidence as to title to the
Common Shares represented by this Certificate, a bond of indemnity (or both) and
payment of associated costs and expenses as a condition to the issuance of a
replacement certificate.

   The Common Share(s) represented by this Certificate have been issued by TyCom
Ltd., a company organized and existing under the laws of Bermuda. The Company
has authorized the Transfer Agent to register the transfer of the Common
Share(s) on its behalf, which registration is required by Bermuda law.

   The following statement is a summary of bye-laws 38-42 of the Bye-Laws of the
Company. Such summary does not purport to be a complete statement of such
provisions and is qualified in its entirety by reference to the Bye-Laws. Such
summary is exclusive of the effect of the laws of Bermuda.

   The transfer of Common Shares requires a duty executed instrument of
transfer. The transfer or remains the holder of the Common Shares until the
transferee is registered in the register of members of the Company as the
holder. The executed transfer must be delivered to either ChaseMellon
Shareholder Services, L.L.C. at P.O. Box 3316, South Hackensack, New Jersey
07606 or Reid Management Limited at Windsor Place, 4th Floor, 22 Queen Street,
Hamilton HM11, Bermuda, together with the certificate for the Common Shares
being transferred. The company may decline to register transfers of shares in
certain circumstances.

   The following abbreviations, when used in the inscription on the face of this
certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:


   TEN COM - as tenants in common        UNIF GIFT MIN ACT-.......CUSTODIAN.....
   TEN ENT - as tenants by the contracts             (Cust)        (Minor)
   IT TEN  - as joint tenants with right of       under Uniform Gifts to Minors
             suvivorship and not as tenants       Act................
             in common                                  (???)

    Additional abbreviations may also be used though not in the above list.

   FOR VALUE RECEIVED......................hereby sell, assign and transfer unto


   Please Insert Social Security or Other
     Identifying Number of Assignee

  [                               ]



  ........................................................................
            (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS OF ASSIGNEE)

  ........................................................................

  ........................................................................

  ........................................................................
  common shares represented by the within Certificate and do hereby
  irrevocably continue and appoint

  ..............................................................Attorney
  to transfer the said shares on the books of the within-named Company with
  full power of substitution in the premises.

  Dated.............................


                ...........................................................
                   NOTICE: The Signature to this assignment must correspond
                   with the name as written upon the face of the Certificate in
                   every particular, without alteration or enlargement, or any
                   change whatever.


  Signature(s) Guaranteed:__________________________________________
                                [Unreadable Copy]

                          THE SIGNATURE SHOULD BE GUARANTEED BY AN ELIGIBLE
                          GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS
                          AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH
                          MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE
                          MEDALLION PROGRAM), PURSUANT TO S.E.C. RULE 17Ab-1s.

<PAGE>

[LOGO OF TYCOM]

COMMON SHARES
PAR VALUE US $0.25


INCORPORATED UNDER THE LAWS
    OF BERMUDA

<TABLE>
<CAPTION>

<S>                                                                                              <C>
          THIS CERTIFICATE IS TRANSFERABLE                                                         SHARES
          IN NEW YORK, NEW YORK,
          RIDGEFIELD PARK, NEW JERSEY                                                            PLEASE SEE REVERSE FOR
          OR HAMILTON, BERMUDA                                                                   CERTAIN DEFINITIONS
                                                                                                 CUSIP 69144B 10 6
</TABLE>


                                                             [GRAPHIC]

                                                             TYCOM LTD.



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THIS CERTIFIES THAT



IS THE OWNER OF
--------------------------------------------------------------------------------
                                 FULLY PAID AND NON ASSESSABLE COMMON SHARES OF
TYCOM LTD. transferable only on the books of the company by the holder hereof in
person or by attorney duly authorized, upon surrender of this certificate duly
endorsed or assigned. This certificate and the shares represented hereby are
subject to the laws of Bermuda and to the Memorandum of Association and Bye-Laws
of the company as now or hereafter amended. This certificate is not valid until
countersigned by the Transfer Agent and registered by the Registrar.

Witness the facsimile seal of the company and the facsimile signatures of its
duly authorized officers.

dated

COUNTERSIGNED AND REGISTERED:                                         /S/
CHASEMELLON SHAREHOLDER SERVICES, L.L.C.                              PRESIDENT


                                TRANSFER AGENT
                                 AND REGISTRAR

BY /S/                                              /S/
               AUTHORIZED SIGNATURE                 VICE PRESIDENT AND SECRETARY