<PAGE>   1
                                                                   EXHIBIT 10.1

                             SECOND LEASE AMENDMENT

            This First Lease Amendment, dated September ______, 1997
                by and between ATRIUM AT CLEARWATER, LIMITED, a
                          Florida limited partnership,
                                    LANDLORD
                                      AND
                        DIGITAL LIGHTWAVE, INCORPORATED
                                    (Tenant)


                                  WITNESSETH:

         WHEREAS, ATRIUM AT CLEARWATER, LIMITED, Landlord, and DIGITAL
LIGHTWAVE, INC., Tenant, did make and execute a Lease Agreement dated October
7, 1994 for space designated as Suite 500, comprising approximately 7,796
square feet located within the project known as THE SUN BANK BUILDING,
CLEARWATER SQUARE or THE ATRIUM AT SUN BANK BUILDING located on the real
property described in Exhibit "A" attached hereto with an address of 601
Cleveland Street, Clearwater, Florida (the "Property"); and

         Whereas, Landlord and Tenant did make and execute a First Lease
Amendment dated February 16, 1996, whereby Tenant expanded the size of its
Original Premises (with 7,796 rentable square feet) by adding 8,028 rentable
square feet on the 5th floor of the Building which additional area represented
the balance of the 5th floor of the Building with 15,824 rentable square feet
in total ("the Existing Premises") all identified as Suite 500 as depicted on
the attached Exhibit "B-1"; and

         WHEREAS, the parties hereto desire to further extend and alter and
modify said Lease the manner hereinafter set forth;

         NOW THEREFORE, in consideration of the mutual and reciprocal promises
herein contained, Tenant and Landlord hereby agree that said Lease shall hereby
be amended and modified as follows:

               1. EXPANSION OF PREMISES. Tenant hereby agrees to expand the
size of its Existing Premises containing 15,824 rentable square feet of area on
the 5th floor, as set forth in the Lease (hereinafter referred to as the
"Existing Premises") by adding to the Existing Premises an area comprised of
15,824 rentable square feet located on the 6th floor, 4,227 rentable square
feet located on the 2nd floor and 2,312 rentable square feet also located on
the 2nd floor (hereinafter referred to as the "Expansion Premises".) TENANT AND
LANDLORD HAVE HAD THE OPPORTUNITY TO MEASURE THE EXISTING AND EXPANSION
PREMISES 

                                       1

<PAGE>   2



AND THEREFORE, BOTH ACCEPT THE MEASUREMENTS AGREED TO IN THIS SECOND LEASE
AMENDMENT AND ALL PRIOR LEASE DOCUMENTS.

The Existing Premises and the Expansion Premises are hereinafter collectively
referred to as the Expanded Premises and any reference to the Premises as may
be set forth in the Lease shall hereinafter be meant to refer to the Expanded
Premises as referred to and defined herein. Thus, any reference after this date
to the Premises or the Expanded Premises shall be deemed to refer to the areas
constituting portions of the 2nd floor and all of the 5th and 6th floors
consisting collectively of 38,187 rentable square feet as depicted on the
attached Exhibits "B-1", "B-2" and "B-3", which set forth the dimensions,
locations and configurations (existing and proposed) of both the Existing and
Expansion Premises which together are referred to as the Expanded Premises or
the Premises. The Expanded Premises are intended to include the total rentable
office area on the 5th and 6th floors of the Building including the 5th and 6th
Floor elevator lobby areas, within which lobby areas Tenant shall be allowed to
locate a reception or other working areas provided that Tenant at all times
shall comply with all governmental codes and regulations (including fire and
building regulations) regarding the use of such lobby space and provided Tenant
shall bear and assume all risks regarding security or loss of property in this
lobby area which Tenant acknowledges cannot be locked off from the rest of the
Building or from the remaining Premises of Tenant since the lobby area is part
of the Common Area of the Building. Tenant shall include the 5th and 6th floor
lobby areas in its insurance policy regarding liability and property coverages
as required in the Lease. Tenant shall not be entitled to use any portion of
the 2nd floor common area hallways.

Notwithstanding the above, Tenant at its expense may implement an elevator
system or install added elevator equipment and/or one-way locks on the fire
stairways provided such comply with local fire, building and other regulations
so the Tenant can "lock off" access to the 5th and 6th floors after Normal
Business Hours, provided such equipment does not unreasonably interfere with
the Landlord's or any other tenant's use of and/or operations within the
Building and does not violate any local governmental codes or regulations.


               2. LEASE TERM. Landlord and Tenant agree that the lease terms
for the Expansion Premises shall commence as follows: Suite 240 on September
15, 1997, Suite 260 on October 15, 1997 and Suite 600 on December 1, 1997. The
Lease Term for the Existing Premises on the fifth floor shall be extended from
January 1, 1998 through November 30, 1998. The Lease Term applicable to all
areas leased by Tenant and all suites referred to herein shall expire on
November 30, 1998, this new expiration date (November 30, 1998) shall
hereinafter be referred to as the Termination Date of the Lease. Since Tenant
is solely responsible for making any changes to the existing physical
construction of all portions of the Premises, Tenant shall not be entitled to
delay rent if construction work is not completed timely.


                                       2

<PAGE>   3




AT THE TERMINATION OF THE LEASE OR ANY EXTENSION THEREOF, TENANT SHALL RETURN
THE PREMISES TO LANDLORD IN BROOM-CLEAN CONDITION, WITH NORMAL WEAR AND TEAR
EXCEPTED.


               3. RENT. The Rent for the Expanded Premises with 38,187 rentable
square feet, plus all applicable state and local sales taxes, shall commence as
of the dates set forth above and continuing through November 30, 1998. The
current Rent and the Rent for the balance of the Lease Term are summarized in
the charts below.

<TABLE>
<CAPTION>

=================================================================================================
           DIGITAL LIGHTWAVE, INC. - SUITE 240 RENTAL CALCULATIONS
-------------------------------------------------------------------------------------------------
                              TENANT'S                            BASE RENTAL         BASE RENTAL
    DATES                       SF          RATE PSF                ANNUALLY            MONTHLY
-------------------------------------------------------------------------------------------------
<C>                           <C>           <C>                   <C>                 <C>
-------------------------------------------------------------------------------------------------

09/15/97 - 09/14/98           2,312           16.00               36,992.00             3,082.67
09/15/98 - 11/30/98           2,312           16.00               36,992.00             3,082.67
</TABLE>


<TABLE>
<CAPTION>
=================================================================================================
            DIGITAL LIGHTWAVE, INC. - SUITE 260 RENTAL CALCULATIONS
-------------------------------------------------------------------------------------------------
                              TENANT'S                           BASE RENTAL          BASE RENTAL
    DATES                       SF          RATE PSF              ANNUALLY              MONTHLY
-------------------------------------------------------------------------------------------------

<S>                           <C>           <C>                  <C>                  <C>
10/15/97 - 10/14/98           4,227          16.00               67,632.00              5,636.00
10/15/98 - 11/30/98           4,227          16.00               67,632.00              5,636.00
</TABLE>

<TABLE>
<CAPTION>
=================================================================================================
            DIGITAL LIGHTWAVE, INC. - SUITE 600 RENTAL CALCULATIONS
-------------------------------------------------------------------------------------------------
                              TENANT'S                           BASE RENTAL          BASE RENTAL
    DATES                       SF           RATE PSF             ANNUALLY              MONTHLY
-------------------------------------------------------------------------------------------------

<C>                           <C>            <C>                 <C>                  <C>
12/01/97 - 11/30/98           15,824          16.00              253,188.00            21,099.00
</TABLE>


<TABLE>
<CAPTION>
=================================================================================================
            DIGITAL LIGHTWAVE, INC. - SUITE 500 RENTAL CALCULATIONS
-------------------------------------------------------------------------------------------------
                              TENANT'S                         BASE RENTAL           BASE RENTAL
     DATES                       SF          RATE PSF           ANNUALLY               MONTHLY
-------------------------------------------------------------------------------------------------
<S>                           <C>            <C>               <C>                   <C>    

</TABLE>

                                       3


<PAGE>   4
<TABLE>
<CAPTION>
=================================================================================================
            DIGITAL LIGHTWAVE, INC. - SUITE 500 RENTAL CALCULATIONS
-------------------------------------------------------------------------------------------------

<C>                           <C>             <C>              <C>                    <C>
9/1/97 - 1/31/98              15,824          17.64            279,135.36             23,261.28
2/1/98 - 11/30/98             15,824          16.00            253,188.00             21,099.00
</TABLE>



Paragraph 5(b) of the Lease shall be amended by the terms of the Letter
Agreement between the parties, dated June 10, 1997, with regard to the
extension of the due date of rental invoices to the tenth (10th) of every month
and the addition of a five percent (5%) "Late Charge" for any rental payments
not received by the tenth of any month.

This rent shall be deemed on a gross basis and Tenant shall not make any
separate reimbursement to Landlord for operating expenses, except that Tenant
shall pay for overtime use of air conditioning services requested for the
Premises based on a charge of $30.00 per hour, per floor, for hourly periods
after Normal Business Hours (referred to as "Overtime Usage") as set forth in
the Lease.

The $2.00 per square foot reimbursement to Landlord for certain tenant finish
work in Suite 500 which was above building standard for the fifth floor
(Existing Premises) shall continue to be paid by Tenant on a monthly basis
through January 31, 1998 in addition to the rent as set forth above for the
period expiring January 31, 1998 as otherwise provided in the Lease and First
Lease Amendment for the 15,824 sq. ft. of the Existing Premises only. However,
this tenant reimbursement shall NOT be paid during the extension of the Lease
Term for the Existing Premises from January 31, 1998 through November 30, 1998,
as set forth in this Second Lease Amendment. Furthermore, no such reimbursement
shall be due for any portion of the Expansion Premises as defined in this
Second Lease Amendment.


4.       LIMITED EXPENSE REIMBURSEMENT.

         a. The Limited Reimbursement provisions of Paragraph 5 of the First
Lease Amendment shall no longer be applicable for the period from December 1,
1997 through November 30, 1998, it being the understanding that there will not
be any limited reimbursements for the calendar year 1997 or for the partial
year of 1998 for any portion of the Premises.

         b. Tenant shall not be responsible for payment or reimbursement to
Landlord for any portion of the Operating Expenses of the Building or the
Premises during the initial term of this lease as extended hereby until
November 30, 1998, except that Tenant shall pay for overtime use of air
conditioning services requested for any portion of the Premises based on a
charge of $30.00 per hour, per floor, for hourly periods after Normal Business
Hours (referred to as "Overtime Usage") as set forth in the Lease. It is also
understood that all of the utilities consumed within the Premises and the
Building during Normal Business Hours shall be paid for by Landlord including
the cost of electric consumption, air conditioning, water, and other customary
office services. However, if Tenant requires the use of services not
customarily provided in a full service office building, Landlord reserves the
right to make 
                                       4

<PAGE>   5



reasonable additional charges for such unusual additional services.

         c. Tenant shall provide for all Janitorial Services and Security
Services for the interior portion of its Expanded Premises and shall pay for
such services. Landlord shall provide Janitorial Services to the common
elevator areas and rest rooms for the 2nd, 5th and 6th floors (Tenant's
Premises).


5. SECURITY DEPOSIT. SECURITY DEPOSIT SHALL MEAN A SUM EQUAL TO ONE MONTH'S
GROSS RENT INCLUDING SALES TAX IN THE TOTAL AMOUNT OF $56,263.69, OF WHICH
$10,394.67 IS ALREADY PREVIOUSLY HELD BY LANDLORD AND TENANT SHALL PAY TO
LANDLORD THE DIFFERENCE OF $45,869.02, SIMULTANEOUSLY WITH THE SIGNING OF THIS
SECOND LEASE AMENDMENT. THIS SECURITY DEPOSIT IS IN ADDITION TO AND INDEPENDENT
OF THE PREPAID RENT DEPOSIT AS REFERENCED IN PARAGRAPH 6 BELOW .


6. PREPAID RENT. Tenant shall pay to Landlord the first month's gross rent
INCLUDING SALES TAX FOR THE EXPANSION AREAS ONLY AT SUITES 240, 260 AND 600 IN
THE TOTAL AMOUNT OF $31,606.73 simultaneously with the signing of this Second
Lease Amendment WHICH PREPAID RENT DEPOSIT IS IN ADDITION TO AND INDEPENDENT OF
THE SECURITY DEPOSIT AS REFERENCED IN PARAGRAPH 5 ABOVE . Tenant shall not make
any additional prepayment of the last month's rental obligations. LANDLORD
HEREBY ACKNOWLEDGES THAT A PREPAID DEPOSIT IN THE AMOUNT OF $10,394.67 IS
CURRENTLY BEING HELD FOR THE LAST MONTH'S RENT FOR SUITE 500 AND SHALL CONTINUE
TO BE HELD IN ACCORDANCE WITH THE LEASE TERMS, EXCEPT THAT THIS DEPOSIT IS NOW
EXPECTED TO BE APPLIED TO A PORTION OF THE RENT DUE FOR THE MONTH OF NOVEMBER,
1998.


7. PARKING. Tenant shall have no rights to use any portion of the Parking
Garage unless set forth herein. The following provisions shall be applied and
enforced on a non-discriminatory basis among all tenants.

         a) Neither Tenant nor any of its invitees shall have any right to
access the Parking Garage except as specifically provided for herein.

         b) During the Lease Term, Tenant shall have the right to use 10
covered garage parking spaces which shall be provided AT A COST OF $25.00 PER
SPACE, PER MONTH PLUS SALES TAX to tenant, plus 80 covered garage spaces at a
cost of $25.00 per space, per month plus sales tax. In addition, Tenant shall
have the right to use 30 uncovered rooftop garage spaces which shall be
PROVIDED AT A COST OF $25.00 PER SPACE, PER MONTH PLUS SALES TAX to Tenant. The
foregoing parking costs shall NOT BE SUBJECT TO INCREASE UNTIL AFTER NOVEMBER
30, 1998, AT WHICH TIME, DURING ANY OPTIONAL LEASE TERM EXTENSION PERIOD THE
PARKING CHARGES SHALL increase by five percent in each lease year assuming the
Lease is extended pursuant to the renewal terms herein of Paragraph 10 or 11.
The foregoing parking spaces which total 120, shall be available to Tenant and
shall be allocated by Tenant to employees

                                       5

<PAGE>   6



of Tenant at the discretion of Tenant. Tenant shall provide Landlord with the
names of employees to be located in these spaces and the vehicle make and
license number for such employees who obtain their parking rights directly
through Tenant. The parking charges for "covered" and "uncovered" parking
spaces shall be paid for by Tenant as provided above and shall be due each
month as stated herein with Tenant's monthly installments of Base Rent and
shall be subject to all terms, provisions, conditions and covenants of this
Lease pertaining to defaults in the payments of Rent. LANDLORD RESERVES THE
RIGHT TO REASSIGN, CHANGE OR RELOCATE ANY OF THE 120 ABOVE PERMANENT PARKING
SPACES WITH TWENTY (20) BUSINESS DAYS PRIOR NOTICE TO TENANT.

         c) In addition to the fixed parking spaces allotted to Tenant as
provided in subparagraph (b) above, which Tenant may allocate among its
employees, Landlord may provide additional "Temporary Parking" spaces to Tenant
or directly to employees of Tenant provided that Landlord reserves the right to
terminate any of these "Temporary Parking" spaces upon TWENTY (20) business
days prior notice to the respective party.

As of September 30, 1997, Landlord shall provide various employees of Tenant
with UP TO 80 additional "Temporary Parking" spaces of which 41 shall
constitute uncovered rooftop parking spaces at a cost of $35.00 per space, per
month plus sales tax, plus 39 covered garage parking spaces at a cost of $35.00
per space, per month plus sales tax, all of which shall be located at
Landlord's sole discretion and all of which shall be subject to the unilateral
cancellation rights of Landlord with the above noted TWENTY (20) business days
prior notice. The spaces referred to in this subparagraph (c) "Temporary
Parking" shall also be subject to the other restrictions and conditions as set
forth in this Paragraph 7, including but not limited to the conditions
precedent set forth in subparagraph (f) below).

         d) Access to such parking spaces shall be through the driveways and
walkways located in the Parking Garage and/or on the Property which shall be
used by Tenant on a non-exclusive basis with Landlord and other tenants of the
Building or other authorized users of the Parking Garage. Landlord shall have
the right, in Landlord's sole and reasonable discretion, to establish rules and
regulations for use of the driveways, elevators, skybridge, walkways, parking
spaces and areas and to designate the right for the exclusive use of particular
parking spaces to other tenants in the Building, visitors and handicapped.
Landlord reserves the right to, at any time, reassign, change or relocate any
designated parking spaces within the Property or the Parking Garage. Landlord
shall also have the right to establish or modify the methods used to control
traffic and parking on the Property and the Parking Garage, including, without
limitation, the installation of traffic control devices, security devices,
Parking Garage gate entrance controls, or the hiring of parking attendants.
LANDLORD RESERVES THE RIGHT TO ENFORCE THE RESTRICTIONS OR DESIGNATIONS SET
FORTH HEREIN BY TOWING VIOLATORS OR OTHER ENFORCEMENT ACTIONS AS LANDLORD DEEMS
NECESSARY.

         e) No commercial or recreational vehicles shall be parked in the
Garage or in any parking areas on the Property.

         f) In order to allow Landlord to enforce the provisions of the
Paragraph and this

                                       6

<PAGE>   7



Lease including, but not limited to, provisions relating to designated parking
spaces, each employee of Tenant who expects to park in the garage in an
assigned parking space shall first provide Landlord with the name of each such
employee and the vehicle make and license number of such person, as a condition
precedent to each person's right to a parking space in the garage. Only those
persons so pre-registered with Landlord shall be permitted to park in the
parking spaces specifically designated and assigned to Tenant per subparagraph
(b) above, or directly to each employee as provided in subparagraph (c) herein.
Landlord may paint Tenant's name on any "covered" and/or "uncovered" parking
spaces ("Rooftop") or number such parking spaces and if any such employee or
designee does not park in such space and parks somewhere else in the Parking
Garage or elsewhere on the property of Landlord not granted to Tenant, Landlord
may tow such automobile of any employee or party violating these restriction
whether or not the Tenant or employee is financially complying with its parking
charge payments to Landlord.

         g) No permanent or part time employee, invitee, agent, or
subcontractor of Tenant shall be permitted to park in any parking space
designated as "Visitor" or in any space designated (by letter identification on
such parking space) for use by another tenant ("Other Tenant") as such Other
Tenant spaces may be designated from time to time by Landlord in Landlord's
sole discretion. The Visitor Parking Spaces or other tenant spaces as
designated from time to time by Landlord shall not be occupied by any person
who conducts part-time or full-time work on or about Tenant's Premises.
Landlord may designate various ground level parking spaces on the North side of
Park Street (to the East of the Building) as Visitor Parking none of which
shall be utilized by any employees of Tenant and Landlord shall prescribe
whatever controls, charges and supervision of such Visitor Parking areas as
Landlord may establish in Landlord's sole discretion. Landlord reserves the
right to enforce the restrictions or designations set forth herein by towing
violators or other enforcement actions as Landlord deems necessary.

         h) Landlord shall have the right, after reasonable notice to Tenant or
directly to Tenant's employee and in Landlord's sole and reasonable discretion,
to change the location of any designated or undesignated parking spaces whether
for visitors, other tenants, handicapped or otherwise.

         i) Tenant agrees that it will collect the parking charges from its
employees who have parking spaces pursuant to subparagraph (b) above and Tenant
shall remit the monthly collections to Landlord in one single payment with a
notice in writing of any non-paying employee, should Tenant so elect to make
such notice, which notice may be relied upon by Landlord in enforcing the
parking provisions herein. Landlord may alternatively accept payments for
Temporary Parking spaces from employees directly for parking charges as
required herein according to subparagraph (c) above, provided such parking
privileges may be revoked automatically and immediately if payment is not made
and Tenant hereby consents to such termination. Tenant and Landlord agree that
such termination of a direct employee parking arrangement for Temporary Parking
space shall not affect the status of Landlord or Tenant under the Lease and
provided further that any parking agreement negotiated directly between
Landlord and an employee of Tenant under subparagraph (c) may

                                       7

<PAGE>   8



include monthly rental rates as determined by Landlord from time to time in
Landlord's sole discretion with such parking rights in all respects being
subject to cancellation by Landlord upon THIRTY (30) business days prior notice
to such employee of Tenant.

         j) Notwithstanding anything to the contrary set forth elsewhere in
this Lease, any default in the payment of monthly parking charges which is to
be paid directly by Tenant as set forth in subparagraph (b) above shall
constitute a monetary default under this Lease provided Landlord shall also
have the right to unilaterally discontinue parking privileges for any space for
which parking charges are not paid current. If parking rights are so
discontinued by Landlord for such non-payment, Landlord may enforce such
discontinuance by towing, tagging, or any other measures necessary.

LANDLORD SHALL NOT BE LIABLE FOR ANY DAMAGE TO OR ANY THEFT OF ANY VEHICLE, OR
ANY CONTENTS THEREFROM, WHILE IN OR ABOUT THE PARKING AREAS LOCATED ON OR ABOUT
THE PROPERTY OR THE PARKING GARAGE AREA.


8. SIGNAGE. Landlord at its sole cost shall provide for FOUR separate lines on
Landlord's first floor Building Directory with the Directory strips to read as
follows:

             Digital Lightwave, Inc. - Executive Offices - Suite 500
             Digital Lightwave, Inc. - Technical Offices - Suite 600
             Digital Lightwave, Inc. - Accounting Offices - Suite 240
             Digital Lightwave, Inc. - Sales and Marketing Offices - Suite 260

Tenant at its sole cost shall install signage on the doors to its Premises
after Landlord's prior approvals to the size, construction and materials to be
used by Tenant with Landlord's approval not to be unreasonably withheld. In all
instances Tenant shall be solely responsible for the removal of such signage at
the termination of the Lease and for the cost of restoring the Premises to the
conditions that existed prior to the installation of such signage. Tenant shall
also restore the Premises and repair the Premises due to any signage that may
be existing on the 5th floor as of the date this Lease Amendment is being
executed.


9. RULES AND REGULATIONS. The Rules and Regulations attached as Exhibit "C"
shall replace those Rules and Regulations attached to the Original Lease and
the First Lease Amendment to Lease.


10. OPTION TO EXTEND TERM. The Landlord hereby grants to the Tenant the right
to renew this Lease for ONE (1) additional period of THREE (3) years, which
right shall be conditional upon the Tenant's satisfying all the following
conditions:

         a) The option(s) for renewal must be exercised with written notice of
that intention delivered to Landlord prior to January 15, 1998. If written
notice is not received by Landlord 

                                       8

<PAGE>   9



within the foregoing time period, the option to extend shall be considered null
and void.

         b) The option to renew granted herein is only exercisable in the event
that the Tenant is not in default of the Lease or in the performance of any of
the terms and conditions of this Lease at the time of exercise or the option
and at the commencement date of the option term.

         c) If the option to renew is exercised, all of the conditions in the
Lease shall remain the same, with the following exception:

                  (i) The Gross Rent shall be $17.00 per square foot for the
                  first year of the Option Period and then increased by five
                  percent (5%) for each year thereafter over the monthly Base
                  Rental payable for the preceding one year period.

                  (ii) IN THE EVENT TENANT EXERCISES ITS RIGHT TO EXTEND ITS
                  LEASE UNDER THIS PARAGRAPH 10, TENANT SHALL NOT BE ENTITLED
                  TO ANY CREDIT IN THE RENTAL OBLIGATION FOR ANY PORTION OF THE
                  PREMISES WHICH CREDIT WOULD HAVE REPRESENTED A RETURN OF
                  ABOUT $2.00 PER SQUARE FOOT PER YEAR IN RENT WHICH TENANT
                  WOULD HAVE PAID BETWEEN MAY 1, 1996 AND JANUARY 31, 1998 AS A
                  REIMBURSEMENT TO LANDLORD FOR UPGRADED TENANT FINISH COSTS
                  PAID FOR BY LANDLORD FOR SUITE 500.

                  (iii) TENANT SHALL AGAIN BE LIABLE FOR LIMITED EXPENSE
                  REIMBURSEMENTS OF THE OPERATING EXPENSES AS SET FORTH IN
                  PARAGRAPH 5(A) OF THE FIRST LEASE AMENDMENT, EXCEPT THAT
                  TENANT WILL BE PAYING FOR ANY INCREASED COSTS OF INSURANCE
                  OVER AND ABOVE THE AMOUNT OF SUCH COSTS FOR THE CALENDAR YEAR
                  1997.

         d) THE OPTION WITH RESPECT TO SUITE 260, IS SUBJECT TO A RIGHT OF
FIRST REFUSAL OR LEASE OF A PORTION OF SUITE 260 WHICH LEASE RIGHTS ARE HELD BY
MCKIM & CREED AND WHICH RIGHTS GENERALLY GRANT MCKIM & CREED THE RIGHT TO
OCCUPY ABOUT 1,037 SQUARE FEET AS PART OF SUITE 260 WHICH OCCUPANCY IS TO BE
EFFECTIVE AS OF DECEMBER 1, 1998. SINCE TENANT MAY WANT TO RENEGOTIATE THE
TERMS OF MCKIM & CREED'S FUTURE USE OF PORTIONS OF SUITE 260, LANDLORD HEREBY
GRANTS TENANT THE RIGHT TO HAVE DIRECT DISCUSSIONS WITH MCKIM & CREED TO
DISCUSS PLANS FOR SUITE 260 OR PORTIONS THEREOF. IN EXERCISING THIS OPTION TO
EXTEND THE LEASE TERMS, TENANT MAY ELECT TO DELETE SUITE 260 FROM THE PREMISES
TO BE EXTENDED, AND MAY, THEREFORE, EXTEND THE LEASE TERMS FOR THE 5TH AND 6TH
FLOORS ALONE WITHOUT SUITE 260.

11.      ALTERNATE OPTION TO EXTEND TERM. The Landlord hereby grants to the 
Tenant the right to renew this Lease for ONE (1) additional period of NINE (9)
months, which right shall be conditional upon the Tenant's satisfying all the
following conditions:

         a) The option(s) for renewal must be exercised with written notice of
that intention delivered to Landlord prior to January 15, 1998. If written
notice is not received by Landlord within the foregoing time period, the option
to extend shall be considered null and void.

                                       9

<PAGE>   10




         b) The option to renew granted herein is only exercisable in the event
that the Tenant is not in default of the Lease or in the performance of any of
the terms and conditions of this Lease at the time of exercise or the option
and at the commencement date of the option term.

         c) If the option to renew is exercised, all of the conditions in the
Lease shall remain the same, with the following exception:

                  (i)      The Gross Rent shall be $18.00 per square foot

                  (ii)     IN THE EVENT TENANT EXERCISES ITS RIGHT TO EXTEND ITS
                  LEASE UNDER THIS PARAGRAPH 11, TENANT SHALL NOT BE ENTITLED 
                  TO ANY CREDIT IN THE RENTAL OBLIGATION FOR ANY PORTION OF THE
                  PREMISES WHICH CREDIT WOULD HAVE REPRESENTED A
                  RETURN OF ABOUT $2.00 PER SQUARE FOOT PER YEAR IN RENT WHICH
                  TENANT WOULD HAVE PAID BETWEEN MAY 1, 1996 AND JANUARY 31,
                  1998 AS A REIMBURSEMENT TO LANDLORD FOR UPGRADED TENANT
                  FINISH COSTS PAID FOR BY LANDLORD FOR SUITE 500.

                  (iii)    TENANT SHALL NOT BE LIABLE FOR LIMITED EXPENSE
                  REIMBURSEMENTS OF THE OPERATING EXPENSES AS SET FORTH IN
                  PARAGRAPH 5(A) OF THE FIRST LEASE AMENDMENT.

d) THE OPTION WITH RESPECT TO SUITE 260, IS SUBJECT TO A RIGHT OF FIRST REFUSAL
OR LEASE OF A PORTION OF SUITE 260 WHICH LEASE RIGHTS ARE HELD BY MCKIM & CREED
AND WHICH RIGHTS GENERALLY GRANT MCKIM & CREED THE RIGHT TO OCCUPY ABOUT 1,060
SQUARE FEET AS PART OF SUITE 260 WHICH OCCUPANCY IS TO BE EFFECTIVE AS OF
DECEMBER 1, 1998. SINCE TENANT MAY WANT TO RENEGOTIATE THE TERMS OF MCKIM &
CREED'S FUTURE USE OF PORTIONS OF SUITE 260, LANDLORD HEREBY GRANTS TENANT THE
RIGHT TO HAVE DIRECT DISCUSSIONS WITH MCKIM & CREED TO DISCUSS PLANS FOR SUITE
260 OR PORTIONS THEREOF. 

12. TENANT FINISH. Tenant shall be solely responsible for the payment of all
construction costs, architectural costs, design costs and permitting costs for
any changes to the condition of the Premises as they exist as of August 22,
1997, provided that Tenant shall first obtain the written approval of Landlord
to the design, plans and construction materials to be specified, used and
installed in the Premises. LANDLORD SHALL PROVIDE TO TENANT A WRITTEN REPLY TO
TENANT'S REQUEST FOR LANDLORD'S APPROVALS BY FACSIMILE WITHIN THREE (3)
BUSINESS DAYS OF LANDLORD'S RECEIPT OF SUCH REQUEST PROVIDED THAT TENANT'S
REQUEST SHALL BE DELIVERED TO LANDLORD TO THE ATTENTION OF BOTH WALTER J.
MACKEY AND ANTHONY E. FEILBACK, BY MAIL OR OVERNIGHT DELIVERY (NOT FAXED)
TOGETHER WITH ALL DOCUMENTS, PLANS OR SPECIFICATIONS INCLUDED WHICH MAY BE
REQUIRED FOR LANDLORD'S DETERMINATION. SHOULD LANDLORD'S APPROVAL BE WITHHELD,
LANDLORD SHALL PROVIDE TO TENANT AN EXPLANATION AS TO WHY SUCH APPROVAL IS
DENIED AND, WITHIN REASON, ONE OR MORE POSSIBLE ALTERNATIVE SOLUTIONS AS
DETERMINED IN LANDLORD'S OPINION. SHOULD LANDLORD AND TENANT BE UNABLE TO AGREE
ON SUCH SOLUTIONS, THE PARTIES HEREBY AGREE TO SUBMIT SUCH DISPUTE TO
ARBITRATION.



                                       10

<PAGE>   11




Before starting any construction work within the Premises, Tenant shall comply
with the following:

         a) Tenant shall obtain written approval of the Landlord for the
identity of the general contractor suggested to be used by Tenant which
approval shall not be unreasonably withheld by Landlord provided such
contractor supplies the proof of insurance and workman's compensation, and
releases any lien rights which contractor might have against Landlord's
property.

         b) Tenant shall obtain Landlord's written approval to the plans and
specifications to be used for the construction of any improvements to be made
to the Premises WHICH APPROVAL SHALL NOT BE UNREASONABLY WITHHELD OR DELAYED
WITH LANDLORD'S REPLY DELIVERED TO TENANT WITHIN THREE (3) BUSINESS DAYS
SUBJECT TO THE OTHER REQUIREMENTS PROVIDED ABOVE IN THIS PARAGRAPH 12. ONCE THE
PLANS FOR THE PREMISES ARE MUTUALLY ACCEPTED BY LANDLORD AND TENANT, LANDLORD
AND TENANT AGREE THAT SUCH APPROVED PLANS AND SPECIFICATIONS SHALL BE ATTACHED
AS EXHIBITS "G".

         c) Tenant shall pay all engineers, architects and planners who may
have contributed to the development or preparation of the plans and
specifications or building criteria for the Premises.

         d) Tenant shall provide TO LANDLORD GENERAL CONTRACTOR'S OR
SUB-CONTRACTOR'S RISK OR OTHER INSURANCE COVERAGE WITH LANDLORD AND ITS LENDER
(PRINCIPAL MUTUAL) AS ADDITIONAL INSUREDS, as LANDLORD OR LENDER may reasonably
require for the period during which any construction work is being undertaken
by Tenant, its agents or subcontractors.

Tenant recognizes that a portion of the 6th floor expansion area may have some
smoke damage from the prior tenant "smoking" in the Premises and hereby
releases Landlord from any responsibility for such smoke damage. IT IS
EXPRESSLY AGREED BETWEEN TENANT AND LANDLORD THAT THERE SHALL BE NO LIABILITY
TO LANDLORD TO CURE ANY EXISTING CONDITION AND TENANT ACCEPTS THIS 6TH FLOOR
EXPANSION AREA, AS WELL AS ALL OTHER EXPANSION AREAS, ON AN "AS IS" BASIS.

Pursuant to a meeting between Landlord and Tenant in early 1997, Landlord
proceeded to purchase a 10 ft. double glass door with 2 glass side lights which
Tenant shall purchase from Landlord at a cost of $2,500.00 and which Tenant may
install at its option. Tenant shall also reimburse Landlord the amount of
$7,500.00 by November 1, 1997 for change orders for construction on the 5th
floor which is still outstanding (INVOICE FOR WHICH IS ATTACHED HERETO AS
EXHIBIT "F".)

Tenant shall have the right to utilize the doors, ceilings and lighting
fixtures as may be currently installed in the portion of the 6th floor which
has already received a certificate of occupancy. Tenant shall be responsible
for the demolition of any interior portion of the Premises if approved on the
plans by Landlord, but Tenant shall not change the common

                                       11

<PAGE>   12



areas unless approved by Landlord.

Tenant shall use (not optional) the existing lighting fixtures that are part of
Landlord's existing uninstalled inventory for the lighting requirements in the
unimproved portions of the 6th and 2nd floors and Tenant shall be responsible
for retrofitting these lighting fixtures with new ballasts and lenses. Tenant
shall pay $65 for the Landlord's existing electronic ballasts, tombstone,
reflectors and new replacement paracube lenses. Tenant shall also install
Landlord's Standard unfinished wood baseboard in all of its Premises at a cost
of $1.50 per linear foot which baseboard shall be stained by Tenant in a manner
similar to that installed on the 5th floor. The cost of the lighting fixtures
is $25 per 2x4 fixture in original box (2 fixtures per box with lamps in
place), but existing tar ballasts will be replaced by Tenant with electronic
ballasts. THE FLOOR STOCK AND UNINSTALLED INVENTORY TO BE SUPPLIED BY LANDLORD
WILL BE IN WORKING ORDER, SUBJECT TO THE STATED REQUIREMENT THAT THE EXISTING
LIGHTING FIXTURES BE RETROFITTED AS PROVIDED ABOVE. TENANT WILL NOT BE
OBLIGATED TO INSTALL MORE OF THE LANDLORD'S INVENTORY OF TENANT FINISH ITEMS
THAN ARE NEEDED TO COMPLETE CONSTRUCTION OF TENANT'S PREMISES AND TO COMPLY
WITH THE APPROVED PLANS AND LOCAL CODES.

Tenant shall use USG #323 ceiling tile throughout for each floor of its
Premises.

Tenant shall be responsible for installing all fire protection systems and
complying with all governmental codes relating to the 6th floor and other
suites to be occupied by Tenant. TENANT SHALL BE RESPONSIBLE FOR INSTALLING ALL
AUDIBLE EQUIPMENT, ANNUNCIATORS, STROBES, HORNS, EXIT LIGHTS, DUCT DETECTORS,
FIRE DAMPERS, FIRE WALLS, THE RELOCATION OF SPRINKLER HEADS AND ADDING
SPRINKLER HEADS WHERE NECESSARY PER CODE OR PER APPROVED PLANS. TENANT WILL NOT
DISCONNECT OR INTERFERE WITH ANY EXISTING FIRE PROTECTION EQUIPMENT OR CHANGE
EXISTING EQUIPMENT WITHOUT LANDLORD'S APPROVAL. TENANT WILL COMPLY WITH ALL
LOCAL CODES FOR ALL OF THE IMPROVEMENTS TO BE UNDERTAKEN BY TENANT.

IN THE EVENT THAT TENANT, IN ITS SOLE DISCRETION, DETERMINES TO UTILIZE
LANDLORD'S SERVICES WITH RESPECT TO THE CARPETING OF SUITE 240, Tenant will
advance the cost of the carpeting to Landlord after which Landlord will order
such carpeting with Tenant paying its (or Landlord's) designated installer for
all installation costs and any moving or storage costs associated therewith.
REGARDLESS OF WHO ORDERS OR INSTALLS CARPETING, TENANT WILL BE RESPONSIBLE FOR
ALL COSTS OF SUCH CARPETING AND INSTALLATION.

There shall be no obligation on this Second Lease Addendum until Landlord and
Tenant agree on plans and specifications. Tenant is to pay for all design,
architectural and engineering and all permitting fees for the agreed upon
plans.

Tenant shall indemnify Landlord from any liens in conjunction with the
buildout.

The architectural and engineering plans and specifications to be prepared by
Tenant and approved by Landlord for Tenant's space will comply with all current
ADA legislation.

                                       12

<PAGE>   13




Landlord will be responsible for the common areas being in compliance with ADA.

SINCE TENANT MAY WANT TO RENEGOTIATE THE TERMS OF MCKIM & CREED'S FUTURE USE
EFFECTIVE DECEMBER 1, 1998, OF PORTIONS OF SUITE 260, LANDLORD HEREBY GRANTS
TENANT THE RIGHT TO HAVE DIRECT DISCUSSIONS WITH MCKIM & CREED TO DISCUSS PLANS
FOR SUITE 260 OR PORTIONS THEREOF. IN AS MUCH AS MCKIM & CREED HAS THE RIGHT TO
RECOVER AND LEASE A 1,037 SQUARE FOOT PORTION OF SUITE 260 AS OF DECEMBER 1,
1998. MCKIM & CREED WILL BE RESPONSIBLE FOR OTHERWISE DIVIDING SUITE 260 AS OF
DECEMBER 1, 1998 OR LATER.

13. PROHIBITION OF LIENS

         a) In accordance with the provisions of Section 713.10 of the Florida
Construction Lien Law, Landlord (Owner) has apprised the Tenant that the
Landlord (Owner) has or will be filing a Notice of Lien Prohibition in the
public records of the County in which the building is located advising the
public that any improvement work undertaken by Tenant on the subject property
shall be only for the Tenant's account and that the Landlord (Owner's) interest
in the property shall not be subject to any construction or Mechanic Liens in
connection therewith.

         b) The Tenant shall promptly, at the time of or prior to undertaking
any contract for improvements for the Premises, apprise any contractor of the
Landlord's Notice of Lien Prohibition and shall require that Tenant's selected
contractor sign an Acknowledgment of the Owner's Prohibition of Mechanic Liens
in a form substantially as that set forth hereto as Exhibit "E". Tenant shall
provide the original signed Acknowledgment form to Landlord (Owner) at or
before the time that work commences in connection with any improved improvement
on the Premises.

         c) The Landlord (Owner) has advised the Tenant that Tenant's failure
to notify a contractor of the Landlord's (Owner's) Lien Prohibition on the
subject property shall render any contract between the Tenant and such
contractor voidable at the option of the contractor.

         d) Regardless of whether or not Landlord (Owner) approves the scope of
construction work that might be performed by Tenant, any agent or subcontractor
of Tenant, or any party working with authorization of Tenant or at the request
of Tenant, Tenant shall be solely responsible for the payment of all
construction costs associated therewith and no such party working on behalf of
Tenant shall have the right to file a lien against Landlord's (Owner's)
property and such contractor or agent shall look solely to Tenant for payment.
Tenant acknowledges and represents that any work undertaken or authorized by
Tenant shall be for the benefit of Tenant and that such work shall not be
deemed to benefit the Landlord or the Landlord's interest in the Premises or
the Building.

Tenant specifically acknowledges that Landlord (Owner) has precluded liens
against its property. Tenant also specifically acknowledges that Tenant is
precluded from creating directly or authorizing any other party to create or
file any lien against Landlord's (Owner's) interests in the Property, the
Building or the Premises as defined in the Lease.


                                       13

<PAGE>   14





         e) As a condition precedent to Tenant authorizing any construction
work to be performed (even after Landlord's prior written consent as required
in the Lease), Tenant shall provide all of its contractors with a copy of the
attached "NOTICE OF LIEN PROHIBITION IN LEASE FLORIDA CONSTRUCTION LIEN LAW
713.10 (F.S. 1995)".

         f) Any violation of the foregoing covenants of Tenant shall constitute
a material breach of this Lease and be a material default in this Lease and,
therefore, provide Landlord (Owner) with all default remedies as permitted in,
but not limited to, this Paragraph 13. Similarly, if any agent or contractor
dealing with Tenant should file a lien against Landlord's (Owner's) interests
in the Property, the Buildings or the Premises, then this act of such third
party shall also constitute a material default in this Lease and entitle
Landlord (Owner) to pursue any one or more of the Default Remedies or Options
available.


14.      MISCELLANEOUS.
         a) Tenant is currently in possession of and is presently conducting
business at the Premises referred to in the Lease, First Lease Amendment, and
this Second Lease Amendment. There are no actions, either voluntary or
involuntary, pending against the Tenant under the bankruptcy laws of the United
States.

         b) Tenant is not entitled to any credit, offset or reduction in rent
for any reason whatsoever and Tenant has no defenses to the enforcement of the
Lease, as amended, by Landlord. There exist no claims or potential claims by
Tenant against Landlord. If other than a living person, Tenant is existing and
in good standing in the jurisdiction of its formation, is qualified to do
business in Florida, and Tenant and the individual signing below has the full
power and authority to execute this Second Lease Amendment.

         c) All terms in the Second Lease Amendment shall have the same meaning
ascribed to them in the Lease and/or in the First Lease Amendment, except as
expressly provided to the contrary in this Second Lease Amendment. In the event
of a conflict between the terms and conditions of the Lease or First Lease
Amendment and terms and conditions of the Second Lease Amendment, this Second
Lease Amendment shall govern and supersede.

         d) Except as specifically and expressly modified herein, the Lease is
ratified and confirmed in all respects and shall remain binding on and inure to
the benefit of the parties hereto, and their successors and assigns.

         e) The expenses of Cushman and Wakefield (C&W) and/or Andy May
regarding negotiation of this Second Lease Amendment, SPECIFICALLY FOR THE
EXISTING AREA IN SUITE 500 WITH 15,824 RENTABLE SQUARE FEET, shall be paid for
exclusively by LANDLORD WHICH COMMISSION SHALL BE EQUAL TO THREE PERCENT (3%)
OF THE NET RENTS TO BE RECEIVED BY LANDLORD WITH THE NET RENTS TO BE DEFINED AS
THE GROSS RENTS PAYABLE PURSUANT TO THE LEASE LESS OPERATING EXPENSES WHICH ARE
ESTIMATED AND AGREED TO BE $7.10 PER SQUARE FOOT FOR 1997 AND WHICH ARE
MUTUALLY AGREED TO ESCALATE BY FIVE PERCENT (5%) PER ANNUM THEREAFTER. WITH
REGARD TO THE EXPANSION PREMISES CONSISTING OF SUITES 240, 260

                                       14

<PAGE>   15



AND 600 AS DEFINED ABOVE, LANDLORD SHALL PAY A COMMISSION EQUAL TO THREE
PERCENT (3%) OF THE "GROSS RENTS" FOR THE INITIAL LEASE TERM THROUGH NOVEMBER
30, 1998. THE LEASING COMMISSIONS TO C&W SHALL BE PAYABLE UPON THE MUTUAL
EXECUTION OF THIS SECOND LEASE AMENDMENT. WHEN AND IF TENANT ELECTS TO EXTEND
OR EXPAND ANY OR ALL OF ITS PREMISES AS DEFINED HEREIN, INCLUDING BUT NOT
LIMITED TO SUITES 240, 260, 500 AND 600, C&W SHALL BE ENTITLED TO AN ADDITIONAL
THREE PERCENT (3%) COMMISSION APPLIED TO THE GROSS RENTS. GROSS RENTS SHALL BE
AS DEFINED IN THE COMMISSION AGREEMENT OF JANUARY 9, 1997. THIS COMMISSION
STRUCTURE SHALL PREVAIL OVER ANY CONTRARY PROVISIONS AS MAY HAVE EXISTED IN A
PREVIOUSLY EXECUTED COMMISSION AGREEMENT BETWEEN LANDLORD AND C&W OR ANY OTHER
WRITTEN OR ORAL AGREEMENT PRIOR TO THIS DATE. Tenant, by execution of this
Second Lease Amendment shall indemnify Landlord of any other brokerage
commissions or fees incurred by Tenant or its agents OTHER THAN THE COMMISSION
TO C&W FOR SUITES 240, 260, 500 AND 600 AS AGREED ABOVE WHICH LANDLORD IS
PAYING. Landlord represents that it has not authorized any brokers OTHER THAN
C&W to act on its behalf and will similarly indemnify Tenant for any cause of
action for fees or commissions relating to agents acting on behalf of Landlord.

All other terms of the Lease and First Lease Amendment as amended to this date
shall remain in full force and effect except as provided to the contrary as set
forth herein.


         IN WITNESS WHEREOF, Tenant and Landlord have caused this instrument to
be executed as of the date first above written by their respective officers or
parties thereunto duly authorized.


WITNESSES:                             LANDLORD:
                                       ATRIUM AT CLEARWATER, LIMITED,
                                       a Florida limited partnership

                                       BY: 
-------------------------                  -----------------------------------
                                           Walter J. Mackey, Jr.,  President
                                           Atrium at Clearwater, Incorporated,
-------------------------                  General Partner
                                           Date Signed: 
                                                        ----------------


WITNESSES:                             TENANT:
                                       DIGITAL LIGHTWAVE, INC.


                                       BY: 
-------------------------                  -----------------------------------

                                       TITLE:
-------------------------                     --------------------------------

                                                Date Signed: 
                                                             -----------------

                                       15

<PAGE>   16


WITNESSES:                             BROKER:
                                       CUSHMAN & WAKEFIELD OF FLORIDA, INC.


                                       BY: 
-------------------------                  -----------------------------------

                                       TITLE:
-------------------------                     --------------------------------

                                                Date Signed: 
                                                             -----------------

EXHIBITS ATTACHED:
Exhibit A - Legal Description of Property
Exhibit B-1, B-2, B-3 - Expanded Premises (including Original and Expansion 
  Premises) 
Exhibit C - New Updated Rules and Regulations 
Exhibit D - Non-Disturbance Agreement 
Exhibit E - Acknowledgment of Owner's Prohibition of Mechanic's Liens 
Exhibit F - Landlord's Invoice for Previous 5th Floor Construction Change 
  Orders 
Exhibit G - Plans and Specifications


                                       16