Path: utzoo!attcan!uunet!husc6!bloom-beacon!bu-cs!kwe
From: kwe@bu-cs.BU.EDU (kwe@bu-it.bu.edu (Kent W. England))
Newsgroups: comp.dcom.lans
Subject: Re: In search of an inexpensive fiber "backbone"
Summary: I would recommend a FO multiport repeater
Message-ID: <25271@bu-cs.BU.EDU>
Date: 7 Oct 88 20:59:10 GMT
References: <1581@csun.edu>
Reply-To: kwe@buit13.bu.edu (Kent England)
Followup-To: comp.dcom.lans
Organization: Boston Univ. Information Tech. Dept.
Lines: 49

In article <1581@csun.edu> djc@csun.edu (Dave Crawford) writes:
>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.  

	You certainly can use fiber optic transceivers at the devices
and this is relatively cheap.

> 
>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.
>

	You can't really economically set up a fiber optic ethernet
bus, you should use a fiber optic multiport repeater in a star
configured arrangement.

	If you are going to the trouble to install fiber at all, I
recommend using at least 12 strand cable, if not 24 or 48 strand
cable.  Most of the cost is in the installation.  You could run a
multistrand cable in a daisychain between your buildings and then
connectorize or splice the fibers together in a logical star (with the
hub in any building) without losing too much signal in the
splice/connector.  Then use fiber optic transceivers on the end of
each spoke and an 8 port fiber optic multiport repeater at the hub.
Much easier to maintain and that's the way most vendors design their
fiber optic Ethernet systems.

                splice            splice         connect
    HUB |---------|----------------|---------------|--+
        |---------|----------------|------+           |
        |---------|---+                   |          FOT
    MPR |             |                  FOT
       FOT           FOT

	You will have spare fiber left over and the star configuration
is easier to manage so long as the hub is at the easiest location (ie
in your area or machine room).  You can always break this
configuration up and splice it together in a new way if you ever have
to move the hub or use the fiber for something like FDDI.

	Kent England, Boston University