dark fiber and sfp distance limitations

Alexander Harrowell a.harrowell at gmail.com
Sat Jan 2 00:23:09 UTC 2010

On Friday 01 January 2010 23:19:30 Richard A Steenbergen wrote:
> On Fri, Jan 01, 2010 at 02:52:33PM -0800, Mike wrote:
> > I am looking at the possibility of leasing a ~70 mile run of fiber. I
> > don't have access to any mid point section for regeneration purposes,
> > and so I am wondering what the chances that a 120km rated SFP would be
> > able to light the path and provide stable connectivity. There are a lot
> > of unknowns including # of splices, condition of the cable, or the
> > actual dispersion index or other properties (until we actually get
> > closer to leasing it). Its spare telco fibers in the same cable binder
> > they are using interoffice transport, but there are regen huts along the
> > way so it works for them but may not for us, and 'finding out' is
> > potentially expensive. How would someone experienced go about
> > determining the feasibillity of this concept and what options might
> > there be? Replies online or off would be appreciated.
> That shouldn't be too difficult, especially at only 1G (though pesonally
> I can't imagine why you would bother leasing dark fiber for that :P).
> There are several ways you could do it, including 120km+ rated SFPs
> (iirc there have been 200km SFPs out for a while too), an external
> optical amplifier (ideally you'd want to amp in the middle, but with a
> single channel you should be fine w/pre-amp), and a digital FEC wrapper
> to extend the receive sensitivity. Remember that the distance spec on
> optics is mostly a rough guideline, so depending on the fiber conditions
> and number of splices/panels along the way you could potentially expect
> to get the entire distance out of a "standard" 100km optic.

There was an excellent thread on this list last year about using "unusual" 
high power lasers for long range optical networking.

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