Path: utzoo!attcan!uunet!husc6!cs.utexas.edu!sm.unisys.com!csun!djc
From: djc@csun.edu (Dave Crawford)
Newsgroups: comp.dcom.lans
Subject: In search of an inexpensive fiber "backbone"
Summary: What's the best cheap fiber ethernet technology?
Message-ID: <1581@csun.edu>
Date: 6 Oct 88 22:04:11 GMT
Reply-To: djc@csun.edu (Dave Crawford)
Organization: California State University, Northridge
Lines: 48

We would like to connect ethernet devices in four separate
buildings with a fiber-optic backbone.  Since we are linking
together DEVICES rather than CABLE SEGMENTS, we hoped that we
could use relatively inexpensive fiber-optic transceivers rather
than fiber repeaters or star-topology hubs.  The backbone we
envision would look something like this:

   ---------        ---------        ---------        ---------
   | FIBER |________| FIBER |________| FIBER |________| FIBER |
   | XCVR  |        | XCVR  |        | XCVR  |        | XCVR  |
   ---------        ---------        ---------        ---------
       |                |                |                |
       |                |                |                |
  -----------      -----------      -----------      -----------
  |  CISCO  |      | NOVELL  |      | NOVELL  |      |CABLETRON|
  |ETHER-X25|      | SERVER  |      | SERVER  |      |MULTIPORT|
  | GATEWAY |      |         |      |         |      |  XCVR   |
  -----------      -----------      -----------      ----------- 
 
In other words, we would like to set this up just as we would if
we were using standard thick ethernet cable and transceivers. 
The entire fiber run would be less than half a mile.  The
buildings are virtually in a straight line.

Is this a feasible plan?  We are novices in using fiber, so we
would welcome any advice, warnings or product testimonials.

For instance, several companies (Black Box, Cabletron) market
fiber transceivers that can only be used to terminate lengths of
fiber.  Since we are planning a daisy-chain, not a star, this
type of transceiver wouldn't do the job.  We've spoken with a
company called Versitron that sells a "bus-topology fiber
transceiver" that seems to be what we are looking for, but we
have no experience with this company or its products.

The alternative would be to replace each of the middle
transceivers with two fiber repeaters connected to either end of
a coax segment, then tap off of the coax with a standard
transceiver.  The sales rep from Black Box advised against this
and said that we needed at least one "star-topology hub" in the
network (we're not sure why).  Is there an advantage in using
repeaters and/or a central hub?  This is a far more expensive
solution to the problem.

                              Dave Crawford
                              Technical Analyst
                              Cal State University, Northridge
                              djc@csun.edu