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Re: Range using single-mode SFPs across multi-mode fiber
From: Keegan Holley <keegan.holley () sungard com>
Date: Wed, 14 Dec 2011 16:08:26 -0500

2011/12/14 Jeff Kell <jeff-kell () utc edu>

On 12/14/2011 3:37 PM, Keegan Holley wrote:

Single mode just has a smaller core size for the smaller "beam" emitted
laser vs. LED.  it works although I've never done it outside of a lab (MM
is cheaper). As for the distance it theory that should come down to the
optics and your transmit power.  Hopefully this is just a cable
the router to a long line.  I've never heard of a 10K MM fiber run since
optics can't shoot that far.  You should be able to get through the 500m
so that MM optics are rated for, but YMMV (errors, light levels, bounces,
etc etc)

Cisco gives specs for SFP LX over MM (they aren't that great at gig, and
really suck at
10G; if you have 50u OM3/OM4 you can do much better at 10G).

See SFP/fiber/distance table at


They specify that line conditioning cables were used.  I would say if
you're going to bother purchasing why not purchase SM?

We have run LX-over-MM (62.5) on short building runs as a band-aid until
SM is
available, and trying to do all new building MM with 50u OM3/OM4.  We do
have some
dependence on 62.5u MM - used by our aging Simplex alarm system - which
point-to-point looped token ring <*cough*> on the alarm side.

What distances?

 I'm trying to get them to confirm 50u will work point-to-point, but at
some non-alarm-points there would be a
necessary 50-to-62.5 exchange taking place and I'm not certain how to
accomplish that
(50->62.5 would likely have tolerable loss, but not 62.5->50).

I don't think changing core sizes in the middle would work even with SM

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