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Why do I see Port Transceiver Rx High Warning

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TitleWhy do I see Port Transceiver Rx High Warning
Question
Why does a SFP LX (Industrial Temperature) sometimes showing Rx High power warning
Environment
  • EXOS
  • Summit All
  • SFP LX (Industrial Temperature)
Answer
The data sheet for this LX type of optic shows the Tx output is -9 dBm to -3 dBm with typical being -5 dBm. In the lab we measured the link at -5.05dBm with a short length of SM cable.
The warning limits in the device are set for -6 dBm as a high power warning and -3 dBm for High power alarm
This -6 dBm warning is too low.
There must be about -1dBm attenuation in order to make the warning not show up. -1dBm attenuation would be around 3km of distance and these links should be allowed to work down to 2m per IEEE specification.

It is verified with the optic vendor and they confirmed that the Rx Warning high actually should be -4dBm and Rx Alarm high -3dBm
As this is programmed in the optic EEPROM it is not something that can be changed and the EXOS reports from the optic is based on the measurements/readings done by the optic module itself.
EXOS just interprets the values. It is not possible to change this threshold from EXOS.

So, as long the Rx power value does not exceed -4dBm we can safely ignore the warning for these type of optics.
 
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