Evelio Vila evelio at thousandeyes.com
Wed Apr 22 22:01:46 UTC 2015

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.


On Wed, Apr 22, 2015 at 1:51 PM, Baldur Norddahl <baldur.norddahl at gmail.com>

> 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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