The downstream optical amplifier board does not report MUT_LOS when the service between the upstream optical amplifier board and the FIU board is interrupted.
Product

OptiX Metro 6100
OptiX Metro 6040
Fault Type

Service Interruption
Optical Power Abnormity
Optical Multiplexer and Demultiplexing Unit
Optical Amplifier Unit
MUT_LOS
Symptom

The downstream optical amplifier board does not report MUT_LOS when the service between the upstream optical amplifier board and the FIU board is interrupted because of fiber jumper failure.
Cause Analysis

The transmit optical power of the SC2 ranges from 0 dBm to -4 dBm. The threshold for the downstream optical amplifier board to report MUT_LOS is -35 dBm. Assume that the transmit optical power of the upstream SC2 is -2 dBm. When the loss on the line side is no less than 19.5 dB (35-2-1.5-12, where 1.5 is the insertion loss of the FIU and 12 is the isolation of the FIU), the downstream optical amplifier board reports the MUT_LOS alarm.
When the WDM equipment is used in a MAN, the line loss is normally smaller than 19.5 dB. In this case, the downstream optical amplifier board does not report the MUT_LOS alarm when there is a fiber cut between the upstream optical amplifier board and the FIU.
Procedure

Check the output optical power of the upstream optical amplifier board. The output optical power is within the normal range.
Check the input optical power of the upstream FIU. The input optical power is very low. This indicates that the fiber between the optical amplifier board and the FIU is faulty.
Replace the fiber between the upstream optical amplifier board and the FIU. Then, the services become normal.
Reference Information

None.