CRC errors in Fiber connection interface

[q-le]

Hi All,

We have 2 x SFP fiber single-mode uplinks to the Core.

one pair is working perfectly , the other got thousands of 46920 input errors, 42586 CRC.

and the switch's log shown %SFF8472-5-THRESHOLD_VIOLATION: Te1/1/2: Rx power low alarm; Operating value: -20.2 dBm, Threshold value: -18.4 dBm.

How do we fix this with fiber connection ?

Any advise is much appreciated.

Thanks

Peter

[Philip D'Ath]

Have you got either spare SFP's or spare fibre?

Normally you try swapping out one thing at a time to you narrow it down to one thing that has the fault.

A low power alarm could also been the fibre is too long, is of a low grade, or is poorly terminated.

Has it ever worked (and then developed this issue) of have you only just started using it?

[q-le]

No, we do not have spare SFP.

We have replaced with a new patch lead - not make any different.

We have the electrician tested the connector and was told the loss is around 0.40 db - is this acceptable ?

It was working before and suddenly we got alerts one day ie could be someone working near it and tamper with it ????

we have 6 pairs fiber so does it mean we need the cabler to come in to re-do them again ?

Peter

[Philip D'Ath]

Are you sure the SFP's that are working are exactly the same model as the ones with the issue (show inventory in the device will give you the SFP model number).

[q-le]

Sorry they are not same model.

NAME: "TenGigabitEthernet1/1/1", DESCR: "SFP-10GBase-LRM"
PID: SFP-10G-LRM , VID: V03 , SN: AGD1905V0W1

NAME: "TenGigabitEthernet1/1/2", DESCR: "SFP-10GBase-LR"
PID: SFP-10G-LR-S , VID: V01 , SN: FNS1951084Y

It is a long story.

when we first setup they are both using SFP-10GBase-LRM and working perfectly.

Six months later , not sure what happen but we lost connection in Ten1/1/2 link.

Called cabler in , they tested it and said the fiber distant is too long > 530m so we need long range SFP.

We bought the new SFP-10GB_LR long range & installed in ten1/1/2 and we got the connection but now a lot of CCRs and errors !!!!!

Peter

[Philip D'Ath]

You did replace the SFP on both ends of the fibre so they are matching?

[q-le]

yes, 

Peter