Problem with the transceiver on Switch 2960

[Tai Nguyen]

Hello everyone,

I have a problem with transceiver on switch 2960:

Switch#sh interfaces transceiver detail
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.

                              High Alarm  High Warn  Low Warn   Low Alarm
          Temperature         Threshold   Threshold  Threshold  Threshold
Port       (Celsius)          (Celsius)   (Celsius)  (Celsius)  (Celsius)
--------- ------------------  ----------  ---------  ---------  ---------
Gi1/0/49    44.3                90.0        85.0        -5.0      -10.0
Gi1/0/50    45.1                90.0        85.0        -5.0      -10.0

                              High Alarm  High Warn  Low Warn   Low Alarm
           Voltage            Threshold   Threshold  Threshold  Threshold
Port       (Volts)            (Volts)     (Volts)    (Volts)    (Volts)
---------  ---------------    ----------  ---------  ---------  ---------
Gi1/0/49   3.28                  3.63        3.47        3.14       2.97
Gi1/0/50   3.29                  3.63        3.47        3.14       2.97

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Transmit Power     Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
---------  -----------------  ----------  ---------  ---------  ---------
Gi1/0/49    -7.2                 0.0        -3.0        -9.5      -13.0
Gi1/0/50    -7.2                 0.0        -3.0        -9.5      -13.0

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Receive Power      Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
-------    -----------------  ----------  ---------  ---------  ---------
Gi1/0/49   -23.7         --      0.0        -3.0       -19.0      -23.0
Gi1/0/50    -6.4                 0.0        -3.0       -19.0      -23.0

As you can see, Optical Receive Power is over threshold. What shoud I do to fix this problem.

Any suggestion will be appreciated.

Regards,

[Marvin Rhoads]

1. Reseat all of the jumpers between the 2960 and the upstream device.

2. Clean all of the connectors using a proper fiber cleaning kit. If you don't have one, buy it. (Cletop and ferrule cleaner)

3. Check the original installation documentation for your fiber plant (if available). If the link was tested good, then 1 and 2 are the likely culprits.

[Tai Nguyen]

Hi Marvin,

Sorry for delay, I tried reseat all of SFPs, replaced by another one, replace the fiber cable and cleaned the dust of the connectors but not help.

I have one more question, when I faced this issue, how does it affect ? because I still see port is up and the signal is OK.

Thanks so much

[Marvin Rhoads]

When operating below the Alarm Rx threshold as you are, you are in danger of losing the link.

It may work for a dB or two below but the link should be investigated and remedied as soon as possible - especially if there's not a backup

[Tom Randstrom]

taint1990

Did Marvin's suggestions correct your low signal level? It is good to leave comments for how you corrected your problem.  

For all users of fiber optic interfaces, it would be a good investment to purchase an optical power meter and optical light source for troubleshooting and maintenance.  The test equipment doesn't need to be very accurate.  We have purchased both the power meter and optical light source pair for $250 (new).  Great units to quickly test link loss, patch cords, transceiver output power, etc.  

As Marvin mentioned,  make sure you have plenty of cleaning supplies. When using singlemode fiber, it doesn't take very much dust/dirt on a connector end face to degrade the optical signal.  

Good luck!