Shawn L shawnl at up.net
Wed Apr 22 22:52:54 UTC 2015

Remember, distance ratings are just generalizations.  It all comes down to
power budget.  When fiber is laid there are slack loops for potential
future service and for use if a cable is cut,  splice cases -- because it's
hard to work with a fiber spool with more than 5 miles of cable on it,
other connectors, hand holes with slack coils, etc.  If the route is 80km
the actual fiber distance  could be more like 100 or 120km with all of the
slack.  Then you add on DB loss for every splice and connector.  As others
have said, the only way to really know is to shoot it with a power meter
and see what the end to end loss is, and then get the correct optics for
the path you have

On Wed, Apr 22, 2015 at 6:43 PM, Rodrigo 1telecom <rodrigo at 1telecom.com.br>

> Nothing is wrong with the fiber... Attenuation is good... Gbics specs says
> -23db as a limit of your sensibility ...i have tried to put bidi sfp+ 80km
> on this fiber and have -25dbi on other side( not connect) this module have
> -20dbi sensibility ...
> This scenario have a 4 channels... And i use 2 10gb channels... C21 and
> c22 on side A and c51 and c52 on side B....
> Enviado via iPhone 
> Grupo Connectoway
> > Em 22/04/2015, às 19:01, Evelio Vila <evelio at thousandeyes.com> escreveu:
> >
> > I think the OP is asking about whether it should account for chromatic
> dispersion or not. Intramodal dispersion may very well be a limit on your
> link even the power budget (as presented before) is fine.  As Mikael said,
> I would stick to the specs from the manufacturer for that specific module,
> or rent an OTDR and make the measurements.
> >
> > --
> > Evelio
> >
> >> On Wed, Apr 22, 2015 at 1:51 PM, Baldur Norddahl <
> baldur.norddahl at gmail.com> wrote:
> >> First: buy a power meter. They are really cheap and the only way to know
> >> for sure how much signal you got. It will also tell you how much launch
> >> power you have. The fiberstore modules are listed as 0 to +5 dBm launch
> >> power - if you got lucky it might be +5 and if you got a lower end
> module
> >> it might be close to 0. Obviously this makes a huge difference for how
> much
> >> power you get on the other end. Also it is said that the laser will lose
> >> power over time.
> >>
> >> Second you need to think in terms of power budget, not distance. So you
> got
> >> 68 km and the module is rated for 80 km - but not all fiber is not born
> >> equal. A power meter allows you to measure the true link loss.
> >>
> >> Third you did not tell what DWDM multiplexer you are using. A 44 channel
> >> DWDM multiplexer from Fiberstore can have up to 4.5 dB insertion loss.
> You
> >> might have two of those on your link for a total of 9 dB loss. Your 80
> km
> >> module has a 23 dB link budget, so this leaves you with 23-9 = 14 dB
> >> budget. If your fiber has 0.25 dB loss per km, that is only 56 km.
> >>
> >> Regards,
> >>
> >> Baldur
> >

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