Mikael Abrahamsson swmike at swm.pp.se
Thu Apr 23 04:01:34 UTC 2015

On Wed, 22 Apr 2015, Rodrigo Augusto wrote:

> Buy 80km sfp+ dwdm modules? c21 and c51.
> On this scenario a don¹t have a EDFA, only put these sfp+ and I have link
> on other side( 60km) but I have a -19dbm and other side I have -21dbm( ddm
> sfp+ output).. I think I have a better signal than this? because I use
> 80km sfp+ and my distance is 60km? can I  have a chromatic dispersion? I
> think to use a EDFA, but i¹m not sure this? if I have a chromatic
> dispersion I have to use a DCM not a ADFA or a booster?
> Right?!

If you use 80km SFP+ then they should be able to handle the CD (chromatic 
dispersion) of your 68km fiber stretch, and if you have a power problem, 
then you can solve that by adding EDFA mid-span.

CD causes "noise" (OSNR) to the receiver, it doesn't cause your power 
levels to be low. So if you want to solve your power problem, add EDFA 
mid-span. If you want to be able to use 40km optics (they might be 
cheaper), add DCM as well if the manufacturer rates them as not being able 
to electronically compensate for dispersion more than 40km.

Mikael Abrahamsson    email: swmike at swm.pp.se

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