Abnormal Decline of the Optical Power

Symptom
The optical power of all OTUs in the local station sharply declines, and the optical signal-to-noise
ratio (OSNR) is lower than the OSNR tolerance of the OTU.

NOTE
Lower OSNR is caused by lower receiving optical power.

Impact on System
A large number of bit errors occur in the services and the services are transiently interrupted
frequently.

Possible Causes
Cause 1: Any fiber jumper in the multiplexing part, or an optical cable degrades or is
physically damaged.
Cause 2: The gain of the optical amplifier board in the upstream station or downstream
station declines.

Tools, Equipment and Materials
U2000, Optical power meter, Cassette cleaner, Ring fiber adapter

Procedure:

Cause 1: Any fiber jumper in the multiplexing part, or an optical cable degrades or is
physically damaged. Hence, the attenuation of the fiber increases and the received optical
power declines. As a result, the OSNR decreases.
1. Check whether the fiber jumper in the multiplexing part is faulty. If yes, replace the
fiber jumper.
2. Remove the fault of the optical cable.

NOTE
The fiber jumpers in the multiplexing part are the fiber jumpers between:
The equipment and ODF
The OA and FIU
The OA and MUX/DEMUX
ODFs
TDC and RDC of the OAU
Cause 2: The gain of the optical amplifier board in the upstream station or downstream
station declines.

1. Check whether the gain of the optical amplifier board is abnormal. If yes, replace the
board.

Thanks for sharing, it helped a lot in rectifying optical power degradation issues on our live network, also degraded OSNR.

nice written, but sometimes optical power degradation also caused by pressure point in the line optical fiber .

the same fault occurs quite often especially when OFC terrain is tough, or OFC having high number of cuts, resulting increase in overall attenuation of the link, good read!

Thanks for sharing your experiences, much appreciated!

Thanks for sharing a troubleshooting case.

regular issue while maintaining the network. Good read.