Switch Keeps Losing Discovery of Next Switch

[JWHolm81891]

I have  Cisco IE-3000-4TC switches in a traffic light cabinet that is daisy-chained to other IE switches along a path. Our fiber provider did work on the fiber between two of these switches and now the first one keeps causing the next switch to go down about every 4 days by losing it's neighbor discovery of the downstream switch which causes the switch after that to go down as well. I'm not seeing much in logs except for duplex mismatches that appear to correct themselves. One switch is set to half and the one that keeps going down to full. The fiber provider won't admit to whatever they might have done and act like they didn't even know they did work out there so I'm not sure where to begin troubleshooting this issue. Looking for advice. 

[Kasun Bandara]

seems like its some connectivity issue in fiber lines as per your explanation. better verify fiber connectivity db levels and data path is in correct measurements. do passive cable testing first to make sure cable is working properly as expected.

[JWHolm81891]

I'm not an seasoned optical guy, but light levels look good. (?) I'm not sure how to do a passive test? I'm also not sure what you mean when stating data path is in correct measurements. Please advise, thanks. 

Downstream switch that goes down as a result of losing neighborhship with 1 switch:

Transmit Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
--------- ----------------- ---------- --------- --------- ---------
Gi1/1 -11.9 -5.0 -8.0 -15.0 -20.0
Gi1/2 -12.4 -5.0 -8.0 -15.0 -20.0

Optical High Alarm High Warn Low Warn Low Alarm
Receive Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
------- ----------------- ---------- --------- --------- ---------
Gi1/1 -15.5 -5.0 -8.0 -27.9 -32.2
Gi1/2 -11.1 -5.0 -8.0 -27.9 -32.2

Upstream switch that stops seeing the downstream switch :

Optical High Alarm High Warn Low Warn Low Alarm
Transmit Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
--------- ----------------- ---------- --------- --------- ---------
Gi1/1 -11.9 -5.0 -8.0 -15.0 -20.0
Gi1/2 -11.1 -5.0 -8.0 -15.0 -20.0

Optical High Alarm High Warn Low Warn Low Alarm
Receive Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
------- ----------------- ---------- --------- --------- ---------
Gi1/1 -13.9 -5.0 -8.0 -27.9 -32.2
Gi1/2 -13.5 -5.0 -8.0 -27.9 -32.2

[Georg Pauwen]

Hello,

I don't know if your SFPs have DOM support, but try the command:

show int x transceiver detail

and post the output.

[MHM Cisco World]

I know it old post, two months ago but that time I was not have answer, all I have some website talk about the dBM But I need something official doc. from cisco and finally I found I, please make review below link. 
good luck friend 
https://www.cisco.com/c/en/us/support/docs/optical/synchronous-digital-hierarchy-sdh/29000-db-29000.html

[MHM Cisco World]

start troubleshooting by 
1- Check the Queue of Interface, 
if there are many control traffic then the Queue can drop some and this some cause peer not see each other and declare drop 
2- Check the Fiber failure