Optic on interface xe-0/0/xx is showing optic reading for TX as -inf while RX is showing valid RX reading, on the remote device the optic reading is showing a valid RX reading which means the TX -inf is incorrect. Optic diagnostics is enabled on the device.

 root@QFX5100> show interfaces diagnostics optics  xe-0/0/xx    <<<<<< Laser bias current and  Laser output power  is showing zero   
Jan 06 16:18:40
Physical interface: xe-0/0/xx
   Laser bias current                       : 0.000 mA
   Laser output power                       : 0.0000 mW / - Inf dBm
   Module temperature                       : 34 degrees C / 92 degrees F
   Module voltage                           : 3.2870 V
   Laser receiver power                     : 0.7333 mW / -1.35 dBm

root@QFX5100> show interfaces diagnostics optics  xe-0/0/xx    <<<<< about 6 minutes before the data is refreshed

Jan 06 16:29:33
Physical interface: xe-0/0/xx
   Laser bias current                       :  40.186 mA
   Laser output power                       : 0.7160 mW / -1.45 dBm
   Module temperature                       : 36 degrees C / 97 degrees F
   Module voltage                           : 3.2820 V
   Laser receiver power                     : 0.7328 mW / -1.35 dBm

Optic reading for TX is showing -inf while remote device is showing valid RX light

Root-Cause

Due to more number of SFPs getting polled during the specified interval, fxpc utilization spikes up.

Workaround

To avoid this issue, please consider to reduce the polling frequency by setting a longer interval (for example 60 sec or above).