1
                                                                    EXHIBIT 10.6

                                     EXABYTE
                               SUBLEASE AGREEMENT

         THIS EXABYTE SUBLEASE AGREEMENT ("Agreement") dated and effective this
10th day of August, 1998, ("Effective Date"), between Exabyte Corporation, a
Delaware corporation, having its principal place of business at 1685 38th
Street, Boulder, Colorado 80301, ("Sublessor") and ILX Lightwave Corporation, a
Minnesota corporation, having its principal place of business at 31950 Frontage
Road, Bozeman, MT 59715 ("Sublessee"), also known as the parties, agree as
follows:

WHEREAS, Sublessor is the tenant of the Premises (described as, 4665 Nautilus
Court, Boulder, CO 80302) pursuant to the terms of a Lease dated May 18, 1995
("Lease"), a copy of which is attached hereto as Exhibit A and incorporated
herein by reference; and

WHEREAS, Sublessor desires to sublease to Sublessee a portion of the Premises,
subject to the terms and conditions as contained herein and in the Lease.

NOW, THEREFORE, in consideration of the rent reserved hereunder and the mutual
promises, covenants, warranties, and representations contained herein, Sublessor
and Sublessee agree as follows:

1.       Scope of Agreement

         1.1.     Sublessee shall assume all obligations of the Sublessor in the
                  Lease dated May 18, 1995 as applicable only with respect to
                  the area which is subleased containing 10,560 square feet in
                  the Northwest section of the Premises, which floor plan is
                  attached hereto as Exhibit B ("Subleased Premises") except as
                  otherwise set forth herein. The terms, conditions and
                  respective obligations of Sublessor and Sublessee to each
                  other under this Agreement shall be the terms and conditions
                  of the Lease, except for those provisions of the Lease which
                  are directly contradicted by this Agreement, in which event
                  the terms of this Agreement shall take precedent to the Lease.

         1.2.     During the term of this Agreement, Sublessee hereby expressly
                  assumes and agrees to perform and comply with, each and every
                  obligation of Sublessor as tenant under the Lease. The
                  obligations which Sublessee has assumed under this Section 1.2
                  which are consistent with the terms of this Agreement
                  hereinafter referred to as the "Sublessee's Assumed
                  Obligations" except for Lease section(s) 29w and 31.

         1.3.     Sublessee shall hold Sublessor free and harmless of and from
                  any liability, judgment, costs and damages, claims and
                  demands, including reasonable attorney's fees, arising out of
                  Sublessee's failure to comply with or perform Sublessee's
                  Assumed Obligations as of the Effective Date of this Sublease.
                  Sublessor shall hold Sublessee




                                       -1-

   2



                  free and harmless of and from any liability, judgment, costs,
                  damages, claims and demands, including reasonable attorney's
                  fees, arising out of Sublessor's failure to comply with its
                  obligations as Tenant under the Lease.

         1.4.     Sublessor agrees to do all things necessary on its part, as
                  tenant under the Lease, to maintain the Lease in full force
                  and effect during the entire term of this Agreement, subject
                  to however, to any early termination on the Lease without any
                  fault on the part of Sublessor.

         1.5.     Sublessor represents and warrants to Sublessee that, as of the
                  date hereof, the Lease is in full force and effect and the
                  copy attached is a complete copy, and that no default exists
                  on the part of either party to the Lease, nor does any set of
                  facts or circumstances exist which, with notice or the passage
                  of time, or both, could constitute an event of default.

         1.6.     Sublessor shall have all rights as defined in Section 23 of
                  the Lease in the event of default by Sublessee.

    2.   Term

         This Agreement shall become effective as of the Effective Date above
         upon its execution by the authorized representatives of the parties. In
         the event the improvements specified in Exhibit D are not complete by
         August 17, 1998, Sublessee may, at its option, delay the initial Rent
         payment due hereunder by an amount of days equal to the days
         commencement was delayed. This Agreement shall expire June 30, 2001,
         unless terminated earlier pursuant to the Lease.

    3.   Premises

         3.1.     The parties agree that the Subleased Premises hereunder
                  consists of approximately 10,560 square feet as noted in
                  Exhibit B hereto. As of the Effective Date of this Agreement,
                  Sublessor warrants that the Subleased Premises complies with
                  all restrictive covenants and governmental regulations and
                  Sublessor shall be responsible to complete the improvement
                  specified on Exhibit D, secure and demise such Subleased
                  Premises and cause such to comply with all governmental and
                  quasi-governmental codes, requirements, and permits, etc. Both
                  parties acknowledge that the Subleased Premises shall be taken
                  on an "as-is" basis subject to Sublessor's obligations to
                  complete improvements.

         3.2.     Sublessee shall be responsible for pro-rata portion of the
                  operating expenses as defined in the Lease for the Subleased
                  Premises. As of the Effective Date, such pro-rata share is
                  28.45%.


                                       -2-

   3



         3.3.     Sublessee shall be responsible for contracting for telephone,
                  gas, electric service, janitorial service and trash removal
                  and the expenses thereof. Gas and electric service expenses
                  are metered separately.

         3.4.     Sublessee shall have the right to use its pro rata share of
                  the available surface parking spaces at no additional charge
                  for the term of this Agreement. As of the Effective Date of
                  this Agreement, the quantity of such parking spaces total
                  twenty-eight (28) and shall be designated as Sublessee's.

         3.5.     Sublessor shall make available the equipment and fixtures
                  specified on Exhibit C for Sublessee's use during the terms of
                  this Agreement. Unless a purchase agreement is executed by the
                  Parties, Sublessor retains title and ownership of such
                  equipment. Sublessor represents that the equipment and
                  fixtures are free and clear from any liens.

         3.6.     Sublessor will pay up to $3,000 to Sublessee as a recarpeting
                  allowance upon Sublessee's submitting a receipt for such.

    4.   Insurance

         Sublessee shall be responsible to maintain throughout the term of this
         Agreement, fire and extended coverage insurance for the personal
         property owned by Sublessee. Additionally, throughout the term of this
         Agreement, Sublessee shall maintain commercial general liability
         insurance including minimum limits of coverage as follows: (i) $1
         million per occurrence; (ii) $1 million general aggregate; (iii) $1
         million products/completed operations aggregate limit; (iv) $1 million
         personal injury. Coverage shall be maintained with insurance companies
         acceptable to Sublessor, which acceptance shall not be unreasonably
         withheld. A certificate of insurance shall be provided to Sublessor
         evidencing this coverage and shall provide that this coverage shall not
         be changed, modified, reduced or cancelled without thirty (30) days
         prior written notice to Sublessor. Sublessee insurance shall be
         endorsed to name Sublessor as an additional insured.

    5.   Rent

         5.1.     Sublessee shall pay to Sublessor, as rent for the Premises,
                  the sum of $7.24 per square foot per annum in advance
                  ("Rent"), on the first day of every month during the term of
                  this Sublease. Monthly Rent shall be $6,371.20 ($7.24 x 10,560
                  square feet / 12). The first month's Rent shall be due
                  September 1, 1998. Any increase in the above specified Rent
                  shall be in accordance Section 5b of the Lease.

         5.2.     Late Charge. If any installment of Rent or of the sum due from
                  Sublessee shall not be received by Sublessor within five (5)
                  days said amount is due, then Sublessee shall pay to Sublessor
                  a late charge equal to five percent (5%) of such overdue
                  amount. The parties hereby agree that such late charges
                  represents a fair and reasonable


                                       -3-

   4



                  estimate of the cost that Sublessor will incur by reason of
                  the late payment by Sublessee. Acceptance of such late charges
                  by the Sublessor shall in no event constitute a waiver of
                  Sublessee's default with respect to such overdue amount, nor
                  prevent Sublessor from exercising any of the other rights and
                  remedies granted hereunder.

         5.3.     Additional Rent. If any sum or amount in addition to or in
                  excess of the Rent provided for in Section 5.1 above is due
                  pursuant to the Lease as Rent for the Subleased Premises, then
                  the Sublessee shall promptly pay any such sum or amount, and
                  Sublessee shall Indemnify and hold harmless Sublessor of and
                  from any and all claims, damages, or loses incurred or
                  suffered by Sublessee as a result of or arising out of any
                  failure or refusal on the part of Sublessee to pay any such
                  amount.

                  Sublessee shall be responsible for a pro-rata portion of the
                  operating expenses as specified in Section 3.2 above. Such
                  operating expenses are estimated at $7.15 per square foot per
                  annum. Additional Rental shall be $1,892.00 ($2.15 x 10,560
                  square feet/12). The first month's additional rent shall be
                  due September 1, 1998. Any increase in operating expenses
                  shall be in accordance with Section 7, of the Lease.

         5.4.     The termination of this Sublease by Sublessor or landlord due
                  to default of Sublessor: (a) does not relieve Sublessee of its
                  obligations to pay Rent accrued under this Sublease through
                  the date of termination; (b) does not waive any claim that
                  Sublessor may have against Sublessee, including, without
                  limitation, claims or indemnification as a result of any claim
                  asserted by Sublessor against by any third party relating to
                  Sublessee's use and occupancy of the Premises; and (c) does
                  not waive any right Sublessor may have to collect money
                  judgments against Sublessee that it may have or may obtain in
                  the future as a result of Sublessee's default under this
                  Sublease prior to such termination.

         5.5.     The parties agree the above-specified Rent includes the
                  equipment systems, cubicles, and telephone equipment currently
                  owned by Sublessor as specified as Exhibit C hereto.

    6.   Security Deposit

         6.1.     A security deposit in the amount of one (1) month's Rent shall
                  be required from Sublessee with respect to this Agreement and
                  held in accordance with respect to this Agreement and held in
                  accordance with the Lease. Such security deposit shall be paid
                  to Sublessor upon execution of this Agreement. Upon the
                  expiration of this Sublease, Sublessor shall return such
                  security deposit to Sublessee, provided all Sublessee's
                  obligations under this Sublease have been fulfilled.



                                       -4-

   5



         6.2.     Sublessor shall provide written notice to Sublessee in the
                  event of any default under this Sublease. If Sublessee shall
                  (i) fail to pay the Rent, or any other sum required by this
                  Sublease to be paid to Sublessor at the time or in the manner
                  provided; or (iii) if Sublessee shall, voluntarily or
                  involuntarily, seek the protection of the Bankruptcy Act and
                  such matter is not dismissed within sixty (60) days; or (iv)
                  if default shall be made in any of the other covenants or
                  conditions on Sublessee's part agreed to be performed, and if
                  such failure to pay Rent or such other sum or such default in
                  performance shall continue for more than thirty (30) days
                  after the written notice of default then Sublessee shall be in
                  default. Sublessee expressly recognizes the right of Sublessor
                  and its agents to retain and have a key to the Premises.
                  Sublessor shall abide by Section 20 of the Lease.

         6.3.     Any such termination, refusal, cancellation, retention, entry,
                  or ejection shall in no manner prejudice any claim Sublessor
                  may then or thereafter have against Sublessee for any charges
                  due or other amounts, including collection and reasonable
                  attorney's fees incurred in connection with Sublessor's effort
                  to collect funds owed to it by Sublessee, or for damages for
                  breach of any of the terms and conditions hereof. Sublessee
                  does hereby agree to indemnify and hold Sublessor harmless for
                  any loss, liability, damage, or deficiency (including
                  reasonable attorney's fees and court costs) arising out of or
                  in any way related to any breach by Sublessee of any terms,
                  conditions, or provisions of this Sublease. Sublessor shall in
                  no way be liable to compensate Sublessee for any damages which
                  Sublessee may suffer by reason of such rightful termination,
                  refusal, cancellation, retention, entry, or ejection hereunder
                  or any other action taken by Sublessor pursuant hereto.
                  Sublessor is not and shall not be responsible for any of
                  Sublessee's personal property including, but not limited to,
                  business and financial records and files located in the
                  Premises in the event that Sublessor exercises its rights
                  against Sublessee pursuant hereto. In addition, Sublessor may
                  exercise all or any rights of a Sublessor as from time to time
                  permitted under Colorado law.

         6.4.     If Sublessee shall not remove all effects and personal
                  property belonging to it from the Subleased Premises or
                  Premises at the termination of this Agreement, Sublessor may,
                  at its option, consider such effects and personal property
                  abandoned and dispose of them in any manner that Sublessor
                  sees fit in Sublessor's sole discretion, or, as Sublessor's
                  option, remove all or part of such effects and personal
                  property and store them without liability to Sublessor for
                  loss thereof, and Sublessee shall be liable to Sublessor for
                  all expenses incurred in such removal and storage as
                  additional Rent.

    7.   Indemnification

         7.1.     Sublessee will indemnify and hold Sublessor harmless from and
                  against any loss, damage, or liability occasioned by or
                  resulting from any default hereunder or any



                                       -5-

   6



                  willful or negligent act on the part of Sublessee, its agents,
                  employees, invitees, or persons permitted within the Premises.

         7.2.     Sublessor will indemnify and hold Sublessee harmless from and
                  against any loss, damage, or liability occasioned by or
                  resulting from any default hereunder or any willful or
                  negligent act on the part of Sublessor, its agents, employees,
                  invitees, or persons permitted within the Premises.

         7.3.     Neither Sublessor nor Sublessee shall be liable to the other
                  or to any insurance company (by way of subrogation or
                  otherwise) insuring them for any loss or damage to any
                  property or loss of income deriving therefrom, or losses under
                  Worker's Compensation laws and benefits, even though such
                  losses or damages might have been occasioned by the negligence
                  of the other party, its agents, or employees.

    8.   Rules and Regulations

         Sublessee and Sublessee's agent's, employees, licensees, and invitees
         shall faithfully observe and comply with any reasonable rules and
         regulations set forth by Sublessor or stated in either this Agreement
         or the Lease from time to time governing the Premises. Such rules and
         regulations may apply, but need not be limited to, safety regulations,
         and matters relating to security. Such rules and regulations shall be
         binding upon Sublessee by delivery of a copy thereof to Sublessee. Such
         rules and regulations current as of the Effective Date shall be
         attached hereto as Exhibit B.

    9.   Headings

         Headings, which include the underlined portion following the section
         number, have been used for reference purposes only and shall have no
         operative effect in the construction of the rights or obligations
         pursuant to this Agreement.

    10.  References

         Any reference to a section number shall include all subsections of such
         section.

    11.  Jurisdiction and Venue

         This Agreement shall be construed under and governed by the laws of the
         State of Colorado, and the competent federal courts in the State of
         Colorado shall decide any disputes between the parties with respect to
         this Agreement.


                                       -6-

   7



    12.  Entire Agreement Counterparts

         This Agreement is intended to be the sole and complete statement of the
         obligations of the parties as to the sublease of the Premises and
         supersedes all previous understandings, negotiations and proposals.
         This Agreement may not be altered, amended, rescinded or modified
         except by written agreement between the parties and signed by an
         officer of each party that expressly amends, rescinds, supersedes or
         terminates this Agreement, and that specifically references this
         Agreement.

    13.  Enforcement

         In the event any provisions of this Agreement are declared
         unenforceable by a duly authorized court having jurisdiction, then this
         Agreement with respect to enforceable provisions shall continue in
         force, and all rights and remedies under the remaining enforceable
         provisions shall survive any such judicial declarations, provided this
         Agreement still expresses the general intent of the parties. In the
         event the general intent of the parties cannot be preserved, this
         Agreement shall either be renegotiated or rendered null and void.

    14.  Notices

         Notices and other communications by a party under this Agreement shall
         be given in writing by mail, postage prepaid, certified, recorded, or
         registered and addressed to the parties at their respective addresses
         as set forth below:

         Sublessee:

         ILX Lightwave Corporation
         31950 E. Frontage Road
         Bozeman, MT  59715
         Attn:  Mr. Larry Johnson

         Sublessor:

         Exabyte Corporation
         1685 38th Street
         Boulder, Colorado  80301  U.S.A.
         Attn:  Mr. Stephen F. Smith

         Such notices shall be deemed to have been given upon mailing. Notices
         may also be given by facsimile, if in the case of Sublessee, they are
         sent to the following number: (406) 586-9405, and in the case of
         Sublessor, they are sent to the following number, (303) 417-7142. If
         given by facsimile, notices shall be deemed to have been given on the
         date of



                                       -7-

   8



         transmission. All facsimile notices shall be confirmed by written
         notice mail, as provided above, within five (5) days of the date the
         facsimile is sent.

    15.  Assignment

         This Agreement is not assignable by either party without written
         permission of the other party, which shall not be unreasonably withheld
         or delayed. Sale of stock or assets of the Parties shall not constitute
         assignment. Sublessee may not sublet the Subleased Premises or any part
         thereof, or any right or privilege appurtenant thereto, or suffer any
         other person (the employees, agents, servants and invitees of Sublessee
         excluded) to occupy or use the Subleased Premises without the prior
         written consent of the landlord and Sublessor, which consent shall not
         be unreasonably denied.

    16.  Waiver

         The waiver by Sublessor or Sublessee of any breach of any term
         covenant, or conditions contained herein shall not be deemed to be a
         subsequent waiver of such terms, covenants, or conditions. The
         subsequent acceptance of payment of Basic Rent or Additional Rent shall
         not be deemed a waiver of any preceding breach of payment by Sublessee
         regardless of Sublessor's acknowledgment of such preceding breach at
         the time of acceptance of such payment.

    17.  No Agency Created

         Neither party is a partner, joint venturer, agent, legal
         representative, or employee of the other. Neither party is granted the
         right or authority to assume or create any obligation or
         responsibility, express or implied, on behalf of or in the name of the
         other party or to bind such other party in any manner to anything
         whatsoever.

IN WITNESS WHEREOF, the parties have executed this Agreement by their duly
authorized representatives, effective as of the date first set forth above.

EXABYTE CORPORATION
         ILX LIGHTWAVE  CORPORATION

By:                                   By:
   -------------------------------       ---------------------------------------
    Stephen F. Smith                      Lawrence A. Johnson

Title:                                Title: President/Chief Executive Officer
      ----------------------------          ------------------------------------

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



                                       -8-

   9



                         CONSENT BY LANDLORD TO SUBLEASE


The undersigned Landlord, under the Lease dated May 18, 1995 by Nautilus Court
II Partnership, Ltd. (Landlord) and Exabyte Corporation (Tenant) hereby
acknowledges the Sublease by and between Exabyte Corporation (Sublessor) and ILX
Lightwave Corporation (Sublessee) and by its signature hereon consents to such
Sublease as of the day and year set forth herein below.

Landlord further agrees to give Sublessee written notification within five days
in the event of any default in the Lease by the Tenant. In the event of a
default by the Tenant, the Landlord, at the Sublessee's option, will enter into
a new lease with the Sublessee to remain in the premises for the remainder of
the original Sublease term. The new lease will include substantially the same
terms and conditions of the current Sublease, except for rent which will be at
market rate, to be reasonably determined by the Landlord.

Landlord:

Nautilus Court II Partnership


By:
   ----------------------------------

Title:
      -------------------------------

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




   10


                             ASSIGNMENT OF SUBLEASE

For value received and effective December 21, 1999, EXABYTE CORPORATION, a
Delaware corporation, Assignor, hereby assigns all its right, title and interest
in and to that certain Sublease Agreement dated August 10, 1998 by and between
EXABYTE CORPORATION, Sublessor, and ILX LIGHTWAVE, a Minnesota corporation,
Sublessee, including a security deposit in the amount of $6,371.20 unto NAUTILUS
COURT II PARTNERSHIP, LTD., a Colorado limited partnership, Assignee, its
successors and assigns. In consideration of this Assignment, said Assignee
hereby assumes and agrees to perform all the covenants and agreements in said
Sublease contained by the Sublessor therein agreed to be made and performed,
including but not limited to the use of the equipment and fixtures by Sublessee
in accordance with Section 3.5 of the Sublease.

ASSIGNOR:                                 ASSIGNEE:

EXABYTE CORPORATION
         NAUTILUS COURT II PARTNERSHIP, LTD.
a Delaware corporation                    a Colorado limited partnership


By:                                       By:
   ---------------------------------         ---------------------------
    Stephen F. Smith                          Valtec Associates, Ltd.
    Vice President and CFO                    by Byron Chrisman, General Partner

CONSENT TO ASSIGNMENT:

The undersigned Sublessee under the Sublease hereby consents to this Assignment
of Sublease as aforesaid.

ILX LIGHTWAVE CORPORATION


By:
   -----------------------------------

Printed Name:
             -------------------------

Title:
      --------------------------------