On 10/14/2013 07:53 AM, Joe Crap wrote:
light instantly. I realise these two sets of transceivers are operating
at different frequencies (1310nm vs 1550nm) but afaik an OS1 cable
should be fine with both, right? We've also swapped the ZR transceivers
Yes, OS1 should work fine at 1550.
into the same ports the LRs are working fine in, it makes no
difference.
Is there any chance you've blown the RX input on one or both xcvr? ZRs
typically can't tolerate bright light on RX, and if someone ever
connected them without an attenuator...
As a general operational thing, I prefer fixed LC simplex attenuators to
attenuated patch leads, because you can then leave the attenuator
"attached" to the ZR RX input, and avoid any forgetfulness about the
nature of what you're doing. Attenuated patch leads OTOH are too easy to
forget about.
I'm afraid my own fiber knowledge is quite limited (much of it learned
from trying to troubleshoot this!), but can anyone suggest further
troubleshooting steps? We don't have the equipment to run an OTDR test
on the patch leads, and I'm trusting the DOM reporting to be at least
vaguely accurate for signal strength.
Couple of things:
If you don't have a handheld lightmeter, consider getting on in the
future - they're useful. If you do, use it! Sadly that'll only verify
TX, which is unlikely to be where the problem lies.
The other thing you can try is substituting an LR for ZR at one end; the
receivers in the xcvr are normally wideband and in theory a 1310 and
1550 optic can link-up (although the last time I tried this, I think it
failed). Obviously you'll need attenuate asymmetrically for this to work
- the ZR will likely overdrive the LR RX, and vice-versa, but by
different values (~3 and ~7dB, respectively). Again simplex attenuators
win here!
Of course it's also possible that Cisco have messed up in IOS; do you
have another device (another vendor?) you can put the xcvr in to test?
If it's an xcvr fault, and only one is dead, you might be able to
determine which one by disabling autoneg - if one end comes up and the
other doesn't, the link-down end has dead RX (or far-end dead TX).
Good luck!
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