That length you're probably going to need Raman amps. As others have mentioned, if you're planning on 10G or higher you'll need to think about Chromatic and Polarization dispersion. If the fiber is still in the process of being laid it shouldn't be too bad assuming the fiber is of high quality.
--chip On Fri, Mar 5, 2010 at 3:58 PM, Chris Tracy <ctr...@es.net> wrote: > It would be helpful to know what type of fiber you are working > with...SMF-28(e) G.652, NZDSF G.655, ...? > > You not only need to account for dB loss over the span, but also chromatic > dispersion. > > At 1550nm, you can expect <= 0.22 dB/km for SMF-28 G.652 if you have a nice > clean fiber path...possibly even <= 0.20 dB/km. (Got any OTDR or CD test > results? Your provider might be able to give them to you...) > > 80km DWDM XFPs typically launch between -1 to +3 dBm, and are only > sensitive down to about -24 to -25 dBm. Unfortunately, I don't have any > data sheets on the 120km versions handy, but I suspect you will be close to > the edge. :-) > > As Dale mentioned, long-reach optics typically have something like "path > penalty at 1450 ps/nm = 2.5dB" in the optical characteristics, so you need > to factor that into your budget as well. The amount of chromatic dispersion > can either be measured or estimated -- but it will greatly depend on which > type of fiber you are using. In general, find out what the maximum amount > of chromatic dispersion the receiver can handle for whatever optics you are > considering. Then look at a datasheet for the fiber you have (or actually > measure it) to see if you are within the spec given in the transceiver > datasheet. > > Cheers, > -Chris > > > On Mar 5, 2010, at 3:36 PM, Justin M. Streiner wrote: > > > A dark fiber path was recently ordered to a remote location on our > network, and to my surprise, the engineering report on the path is coming > back at around 130 km, which is substantially longer than I expected the > span to be. > > > > While I am researching gear that will drive a signal this far without a > mid-span regen, I'm also inquiring with the carrier to see if there is any > way to shorten the span, but I also have to be prepared for the chance that > a shorter span is not possible. > > > > I've seen some pieces from MRV and Transition that might be up to the > job, though most of the options I've seen are rated to 120 km, tops. > > > > That said, I'd be interested in hearing about what people who are driving > similar spans. I don't think I'm going to have the budget to go out and buy > Ciena/Infinera/Cisco ONS kit just for this, since I don't have any at the > present time. The link is still being built, so I haven't gotten an > engineering report yet. My gut tells me that the 2-point loss on the span > at 1550nm will be somewhere around 30-35 dB. > > > > jms > > > > > > > > > -- Just my $.02, your mileage may vary, batteries not included, etc....
