Cisco DOM – Digital Optical Monitoring and does cleaning your fiber cables make any difference?

Cisco has intercorperated monitoring of optical interfaces a while back, but what is relatively new is that the DOM-support is the new default mGBIC from Cisco.
You can recognize the DOM-support by the model name GLC-LH-SMD and GLC-SX-MMD (Notice the D at the end).
Have a look at this link to view full list of supported transceivers.
www.cisco.com/c/en/us/td/docs/interfaces_modules/transceiver_modules/compatibility/matrix/DOM_matrix.html

I thought I’d check out DOM in my lab and was fortunate enough to have an abnormal situation with regards to signal strength.

lab-sw01#show 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)
--------- ------------------  ----------  ---------  ---------  ---------
Gi1/0/27    41.1                85.0        75.0        -5.0      -10.0
Gi1/0/28    31.0                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)
---------  ---------------    ----------  ---------  ---------  ---------
Gi1/0/27   3.28                  3.60        3.50        2.90       2.80
Gi1/0/28   3.31                  3.60        3.50        3.10       3.00

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Transmit Power     Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
---------  -----------------  ----------  ---------  ---------  ---------
Gi1/0/27    -5.3                 0.0        -1.0       -11.0      -12.0
Gi1/0/28    -5.5                 1.0        -3.0        -9.5      -13.5

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Receive Power      Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
-------    -----------------  ----------  ---------  ---------  ---------
Gi1/0/27   -20.9                -3.0        -4.0       -24.9      -26.0
Gi1/0/28    -4.2                 1.0        -3.0       -19.0      -23.0


lab-sw01#
Jun 25 03:22:27.013: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/27, changed state to down
Jun 25 03:22:27.055: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/28, changed state to down
Jun 25 03:22:28.014: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/27, changed state to down
Jun 25 03:22:28.056: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/28, changed state to down

As we can see from the above output, the receive power of Gi1/0/27 was somewhat close the warning threshold.
I used my Fluke networks IBC Cleaner 1.25mm and cleaned all mGBICs and optical cables involved and the result can be seen underneath.

Jun 25 03:23:34.614: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/27, changed state to up
Jun 25 03:23:34.630: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/28, changed state to up
Jun 25 03:23:35.616: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/27, changed state to up
Jun 25 03:23:35.631: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/28, changed state to upshow 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)
--------- ------------------  ----------  ---------  ---------  ---------
Gi1/0/27    41.1                85.0        75.0        -5.0      -10.0
Gi1/0/28    31.1                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)
---------  ---------------    ----------  ---------  ---------  ---------
Gi1/0/27   3.28                  3.60        3.50        2.90       2.80
Gi1/0/28   3.31                  3.60        3.50        3.10       3.00

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Transmit Power     Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
---------  -----------------  ----------  ---------  ---------  ---------
Gi1/0/27    -5.2                 0.0        -1.0       -11.0      -12.0
Gi1/0/28    -5.5                 1.0        -3.0        -9.5      -13.5

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Receive Power      Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
-------    -----------------  ----------  ---------  ---------  ---------
Gi1/0/27    -5.2               -3.0        -4.0       -24.9      -26.0
Gi1/0/28    -4.0                 1.0        -3.0       -19.0      -23.0


lab-sw01#

 

Here we can see the signal strenght has what seems to be normal values. So does cleaning your optical transceivers and cables make a difference? Yes. =)

Digital Optical Monitoring Commands

Switch# show interfaces transceiver
Switch# show interfaces transceiver detail

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