[c-nsp] Catalyst 3750-X with SFP-10G-ZR transceiver - troubleshooting‏

Joe Crap joec423 at hotmail.com
Mon Oct 14 02:53:37 EDT 2013

We need to run 10GbE dark fiber between two 3750-X switches (each with 

a C3KX Service Module installed) over a 30km distance where the 

measured insertion loss makes ER transceivers marginal (total loss> 12

dB) - so we're forced to use ZR transceivers with their greater reach. 

As of the Aug 28th release of IOS 15.2(1)E the ZR optics are now 

supported in this switch - however our initial testing using 3rd-party 

transceivers has been unsuccessful: we are unable to get a link light 

on the port and the logical port never comes up when the fiber is 

plugged in. I was hoping someone could help me sanity check the testing


We're using 3rd-party SFP-10G-ZR clones that report VID: V01 to the 

switch. They support DOM, and we've also tested LR transceivers from 

the same 3rd-party successfully. My testing has been pretty simple so 


Connect Tx-to-Rx and vice versa between the two transceivers using a 2m

 duplex OS1 SMF patch lead that has 15dB fixed inline attenuators 

connected to bring the received signal strength down to the supported 

range (-6 to -27 dBm)

Connected this way however we are unable to get a link light or port-up

 state on these ports. The ZR transceivers show up in a "show inv" 

output, and the DOM on the transceivers is reporting a valid strength 

Rx signal:


switch1#sho int te1/1/2 trans detail

ITU Channel not available (Wavelength not available),

Transceiver is internally calibrated.

mA: milliamperes, dBm: decibels (milliwatts), NA or N/A: not applicable.

++ : high alarm, +  : high warning, -  : low warning, -- : low alarm.

A2D readouts (if they differ), are reported in parentheses.

The threshold values are calibrated.


           Optical          High Alarm  High Warn  Low Warn   Low Alarm

           Transmit Power   Threshold   Threshold  Threshold  Threshold

Port       (dBm)            (dBm)       (dBm)      (dBm)      (dBm)

---------  ---------------  ----------  ---------  ---------  ---------

Te1/1/2      1.7               4.7         4.0         0.0       -0.9


           Optical          High Alarm  High Warn  Low Warn   Low Alarm

           Receive Power    Threshold   Threshold  Threshold  Threshold

Port       (dBm)            (dBm)       (dBm)      (dBm)      (dBm)

-------    ---------------  ----------  ---------  ---------  ---------

Te1/1/2    -12.2              -5.9        -7.2       -25.4      -27.2


If we take the same patch cable, remove the attenuators and plug it 

into the other LR transceivers in the same switches they get a link 

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

 into the same ports the LRs are working fine in, it makes no 


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.

Thanks in advance for any assistance!

- J 		 	   		  

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