[c-nsp] XENPAK packet loss

[FF]

I've been trying to solve an odd problem and can't seem to make any headway.
I'm in the process of upgrading two DF links that were formerly served
by 1GB/ZX optics to XENPAK-DWDM optics. 1 lamba only on each.

The ZX link for the first span ran fine. When the DWDM XENPAK is
installed, both ends see about -15db receive power and ping fine until
traffic is put on them. At about 200-300 mb/s they start losing 1500
byte packets. The more traffic, the more the problem. At night, when
traffic is lower, the link looks clean. No attenuators are on this
link.

On a longer span (140km) link, I have the same setup, with two EDFAs.
The input power comes in right around -24dbm. It tests clean mostly,
but drops 2 packets out of 10,000 when empty. More traffic, more
drops.  I figured it was a strength problem (-24dbm is right at the
edge). So went in with a some fiber cleaners and rejumpered
everything. Got it down to -22dbm which should be well within the
tolerances. If anything the problem got worse, not better.

There are some input/CRC errors incrementing on one side or the other.
Not as many as there are dropped packets, but clearly some do
correlate to dropped packets (for example 6 input errors out of 25,000
packets).

I looked up the data sheet on the Cisco DWDM transceivers (all the
optics and the EDFAs are Cisco) and they say you may get burst errors
above -15dbm, but nothing about bursts at below. I have no idea how to
diagnose for burst errors anyway. I don't know if this is a signal
strength problem, or something else. On the long span, I could
theoretically be hitting issues like dispersion, but on the short span
I should be running perfectly since everything is within tolerances.
Since they are both seeing the same sort of behavior, I am wondering
if its something I've overlooked.

So now I have two spans, of drastically different lengths, both
dropping packets directly related to the amount of traffic moving over
them. Only BGP and static routes are on these. All are 6500/SUP32 or
SUP720s running 12.22-33SXH5 or SXHI1.

Any help/advice/assistance would be appreciated it. I'm trying to
avoid spending 8+ hrs on the phone with TAC.

Thank you very much.

-- 
My opinions aren't even my own. FF