Path: utzoo!attcan!uunet!bu.edu!bu-it!kwe
From: kwe@bu-it.bu.edu (Kent England)
Newsgroups: comp.dcom.lans
Subject: Re: ST or SMA fiber connectors
Message-ID: <58608@bu.edu.bu.edu>
Date: 11 Jun 90 17:58:02 GMT
References: <61655@sgi.sgi.com> <30971@ut-emx.UUCP>
Sender: news@bu.edu.bu.edu
Reply-To: kwe@bu-it.bu.edu (Kent England)
Organization: Boston University
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In article <61655@sgi.sgi.com>, vjs@rhyolite.wpd.sgi.com (Vernon
Schryver) writes:
> 
> The FDDI standard requires neither STs nor SMAs, but MICs.

	That is true, but if you are building a campus backbone fiber optic
cable plant, you may wish to build your patch panels with STs and not FSDs
(Fixed Shroud Duplex) or MICs or whatever we call the FDDI connector.
> 
> Much of the FDDI hardware now being shipped uses STs, often hidden behind
> the shells that turn a pair of ST plugs into a MIC recepticle.  I do not
> know if such shells are available for anything except STs.

	We are piloting some desktop fiber using the AMP FSDs.  AMP (and
others) let you make FSD wall outlets and patch panel outlets using a pair
of STs and a jig to create a FSD.  You can field terminate a pair of STs,
plug them into a mechanical connector, and, presto!, you have a FSD.

	But we are talking "horizontal fiber" or "desktop fiber" and not
"vertical fiber" or "riser".  There is a big difference between inter-
building and intra-building distribution.  The desktop fiber needs to
take account of the FSDs of the workstations/routers, but the intra-
building cable plant does not (unless you decide that the duplex connector
is a great idea).
> 
> If you use STs now, you can later use such shells and some short MIC jumper
> cables to convert your cable plant.  It would cost the insertion loss of an
> extra connector, but would be easier and could be cheaper than
> reterminating.  (Actually, unless you are good with the polishing pads, you
> might have less insertion loss with two machine terminations than with one
> field termination, and so might come out ahead in loss budget by using such
> jumpers.)  Also, if you use STs, you might be able to connect them directly
> to your FDDI equipment, after discarding a shell or jumper cable.
> 
> 
	We are finding the AMP FSD kits to be quite difficult to do in the field.
The mechanical tolerances are quite tight, and you are forced to polish both
ferrules simultaneously.  If one connector is ruined, you are forced to redo
both.  Makes us wonder whether we should use FSDs any more than we have to.
But the technology is still young and we are hopeful that we will find better
field termination strategies for the FSDs.

	But we are planning to use patch cords to a wall outlet with the
fiber pair terminated on a patch panel, cross-connected to the f/o equipment.
This standard approach requires connector matings at the:

	workstation
	wall outlet
	patch panel (2)
	concentrator

	I would not think it wise to try to eliminate any of these connections,
or one would lose the flexibility needed in the cable plant.  This methodology
is independent of medium; we use this approach on unshielded twisted pair,
thin coax and everything else.

	Thanks, Vernon.  I'm not disagreeing with what you said, just pointing
out some other considerations in deploying fiber.

	--Kent England, Boston University