From: ericd@shop.internet.net (Eric Davis)
Date: Sun, 18 Feb 1996 13:02:58 +0800
To: SINCLAIR  DOUGLAS N <dsmith@midwest.net (David E. Smith)
Subject: Re: Using lasers to communicate
Message-ID: <v02130501ad4c4a9c8e31@[205.179.23.30]>
MIME-Version: 1.0
Content-Type: text/plain



Woooa there....

Lasers are not exactly expensive or complicated....

Check out www.lasercomm.com. 4-15Mb/s lasers.
or Cannon 10-100Mb/s lasers.

I have installed these products *many* times and their setup and operation
is fast and efficient. (used to work for Interop)

Exmaple:
We used a pair of these, and MBONE, to provide a 2 way real time video
confrence link joining an IETF session between a room of
users at Japan Interop (local) and a group in Sweeden (IETF). The setup
a was last minute point to point Ethernet link from the confrence center
to a local hotel acress the road. We had 1.5 hours to perform ALL
of the work, from wiring both roofs, seting up the lasers, wiring
the internal hotel/confrence center, and setting up systems and projectors.
!!The Laser setup took about :15 minutes, tops!!

BTW: With this system the transmit "beam" is focused into a "spot" half
way between the sending and receiving units. The receiving unit
is tuned to look for that focused "spot". This means that there is a
very large (area wise) low power laser pattern behind each of the
receivers! With a sensitive enough receiver, it is possible to hear
this signal!

When you need to transport a data stream (1-155Mb/s) to a remote
site, this solution works out to be *MUCH* cheaper than leasing
circuits from bell, bypass folks, etc..

Another case in point: We (ISN) needed to transport a 100Mb/s (FDDI) between \
2 sites. Upon checking, the price of PacBell "dim" fiber was outrageous!
We had no MFS/TCG/etc fiber in the man hole to latch onto. The choice was
clear.

As for security, the bottom line is that encryption devices are cheap.

Last plus for these units is that most foreign countries do not prevent
the use of these point to point optical devices. This is not the case
for spread spectrum multipoint or microwave point to point radio devices.

Eric Davis



At 10:44 PM 2/17/96, SINCLAIR  DOUGLAS N wrote:
>> If you have a secure link you don't need encryption.  Arguably, the
>> converse is true; if you have secure encryption you don't need
>> a secure link.  Isn't the ability to transmit secure data over
>> insecure channels one of the primary justifications for encryption?
>>
>
>Of course.  My point, though I seem to have failed to state it,
>is that encryption is a cheap software thing while laser beams
>are expensive, complicated, and still not secure.

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