[c-nsp] ASR9k CWDM

[Matt Addison]

On Sat, Oct 15, 2011 at 09:39,  <cisconsp at secureobscure.com> wrote:
> Purchase the tunable 10G 80km optics from Cisco such as the DWDM-XFP-C=
> "10G Multirate C Band Tunable DWDM XFP" and use passive DWDM muxes such as
> the OptoSpan DWDM-T16SUL-000
> http://www.optospan.com/passive-wdm-dwdm-mux.php and use that to build
> multiple 10gig links across the metro fiber.

I'd recommend getting 'fixed color' optics rather than tunable.
Tunable is more useful if you're looking at a ROADM system, or need to
reduce spare inventory.

> Another question that I was not able to specifically answer while looking at
> the 10gig xfp dwdm optics page:
> http://www.cisco.com/en/US/prod/collateral/modules/ps5455/data_sheet_78-4585
> 30.html was: what is the maximum supported distance of the DWDM-XFP-C,
> especially through a passive mux. My understanding was that there would be
> power loss when muxing/demuxing and our sites are ~50km in some cases. Do
> the DWDM XFP optics support that kind of distance?

50km without amps is going to be a stretch, especially if you're
piggybacking this on top of an existing CWDM system. eg the Optolink
Mux (8ch) is max 3.4dB on the drop ports, then if you're dropping this
into a CWDM mux (assuming Cisco MUX8) that's another 2.4dB of loss. So
even before you're on the line you're at -5.8dB, then go through that
again at the other end -11.8dB and you're halfway into your ~23 dB
budget for LR2. Once you add in 10dB of line loss you don't have a lot
to spare for connectors.

Without CWDM in the path it's on the difficult side of possible, with
CWDM in the path you're probably going to need pre-amps at either end
on the drop path from the CWDM.

~Matt