[c-nsp] Transceiver oddity on Nexus switch

[Jonathan Stewart]

Hi Drew,

I have seen both N/A (none) and -40 dBm (lower limit) on optics.

It seems to depend on the optic--so maybe the codings are different.  I
wouldn't consider either behaviour "broken".

When I see N/A or -40, I read those both as "no light received by the
optic".

Cheers,
Jonathan

On Tue, Jul 21, 2026 at 9:20 AM Drew Weaver via cisco-nsp <
cisco-nsp at puck.nether.net> wrote:

> Howdy,
>
> I noticed that one QSFP-40G-PLRL4 (that doesn't appear to be working) is
> saying N/A for Rx Power:
>
> Lane Number:1 Network Lane
>            SFP Detail Diagnostics Information (internal calibration)
>
> ----------------------------------------------------------------------------
>                 Current              Alarms                  Warnings
>                 Measurement     High        Low         High          Low
>
> ----------------------------------------------------------------------------
>   Temperature   39.68 C        80.00 C    -10.00 C     75.00 C       -5.00
> C
>   Voltage        3.27 V         3.70 V      2.90 V      3.59 V        3.00
> V
>   Current       34.63 mA       75.00 mA    10.00 mA    70.00 mA      15.24
> mA
>   Tx Power      -1.61 dBm       4.49 dBm   -8.72 dBm    3.99 dBm     -8.21
> dBm
>   Rx Power          N/A         4.50 dBm  -12.50 dBm    4.00 dBm    -11.49
> dBm
>
> I've never seen N/A normally without signal I see something like Rx Power
>    -40.00 dBm -
>
> Is this just perhaps a badly coded transceiver or a broken one?
>
> Thanks,
> -Drew
>
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-- 
     Jonathan