Range using single-mode SFPs across multi-mode fiber - was Re: NANOG Digest, Vol 47, Issue 56

Keegan Holley keegan.holley at sungard.com
Wed Dec 14 20:37:07 UTC 2011

> > inappropriate. We are attempting to use Juniper single-mode SFPs (LX
> > variety) across multi-mode fiber. Standard listed distance is always
> > for SFPs using the appropriate type of fiber. Does anyone out there
> > know how much distance we are likely to get? Thanks for your help in
> > advance.

Single mode just has a smaller core size for the smaller "beam" emitted by
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 connecting
the router to a long line.  I've never heard of a 10K MM fiber run since SX
optics can't shoot that far.  You should be able to get through the 500m or
so that MM optics are rated for, but YMMV (errors, light levels, bounces,
etc etc)

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