[c-nsp] ASR9k CWDM Optics

[Thomas Weible - FLEXOPTIX]

> Generally speaking, WDM kit tends to be very reliable.  You plug it in and it
> works tirelessly until the day it's decommissioned.  They all have redundant
> power feed systems and almost all of them support -48VDC.  Some are
> better for monitoring than others.  Almost all of them support genuinely
> hitless management card upgrades, which is really nice.

Mmmmh, in terms of monitoring, cisco did a good job for the XFP and SFP+ optical monitoring, even for the colored optics. You get all needed information at least on the CLI updated in a period of 5 to 30 seconds. 
Don't forget when using an active WDM system you always have to monitor / troubleshoot 3 links (L2/L3 -> WDM -> Line -> WDM -> L2/L3) instead of one link for passive WDM.

> I like them.  They abstract out your 10G wave delivery platform from your
> particular choice of L2/L3 kit at a particular time, which can be very
> strategically beneficial.  Particularly from a cost point of view, actually.  What
> happens if you switch from one L2/L3 kit type to another, and there is a
> transceiver incompatibility? E.g. XENPAK->XFP for
> 7600->ASR9k migration.  Or a vendor migration and you find that your
> transceivers from the old kit either don't work on the new kit or else that
> they are crippled due to crappy vendor policies about DOM, etc.  They also
> open up the possibility of using SFP+ blades for long-haul.  While there is
> DWDM SFP+ available these days, it's still debatable as to whether it is or will
> ever be a good long-haul wave delivery transceiver format.  However with
> WDM transmission systems, you simply don't need to worry about that.

Looking at all the roadmap of different (non-WDM system) vendors , the SFP+ formfactor (DWDM or CWDM) will be the choice for metro distances up to 80km or 23dB power budget (depending how you watch it). Even when you gonna replace your L2/L3 equipment vendor you might reuse them in the other vendors gear - the physics of the SFP+ are in most cases the same (even more than for XFP) but it also depends on the programming which is solvable (e.g. for DDM /DOM capability or proper warning thresholds, etc.). 
For the ASR9k we already did tests / live installation with CWDM and DWDM, 16 and 23dB XFPs (without FEC) and all of them work fine with a BER of 10^-13 and better. SFP+ I couldn't arrange some setup yet because of the missing linecard. 

In terms of pricing CWDM und DWDM 10G transceivers are almost the same (don't compare it with 1G.. because the pricing is completely different). 

-- Thomas