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best values sfp power rx and tx

  • 1.  best values sfp power rx and tx

    Posted 11-04-2019 10:30 AM
    Hi good day.
    I am optimizing the SAN of my company and I wanted to know based on your experience what are the acceptable light values (rx and tx) and what would be a critical number, for example one of my trunk ports is at -9:
    TrunkLW_2_ID9 port35 RX -9,1 HP_SW840_DOM10 E-Port TrunkLW_2_ID9 39 Online Online

    Is this value critical?
    I hope you can guide me.

  • 2.  RE: best values sfp power rx and tx

    Posted 11-05-2019 10:08 AM
    I have two ports on one of my Brocade 6520s that occasionally report some enc out or pcs errors. Cables are all good, connections have been cleaned, and the errors are not excessive. The only thing different about these ports is the RX power reported by sfpShow is quite a bit lower than on other ports, suggesting a problem with the SFP or HBA on the end device.

    The RX power below which I see some errors is around 240uW (approx -6 dBm).


  • 3.  RE: best values sfp power rx and tx

    Posted 11-05-2019 10:25 AM

    @Sebastian Gorla, the acceptable values depend on the SFPs you're using. The datasheets of the SFPs state the needed Rx and Tx values.  ​

    For a 16G SWL SFP+ this would for example:
    Optical Transmit Power  max:  -1 dBm,  min:  -8 dBm
    Optical Receive Power  max:  0 dBm,  min:  -10.2 dBm

    So if your example is from a 16G SWL SFP+, it is quite close to the min Rx value and might lead to some physical layer issues.

    You could setup alerts for all the SFPs types using MAPS and the different SFP groups therein.  Usually it's better to alert proactive, so raise an alert a bit earlier than the listed min values.

    Senior Systems Engineer
    Broadcom - Brocade Storage Networking