When Receive Optical Power Is Excessively Low Because of the End Face Problem of the Fiber Jumper, the OAU Board Reports the MUT_LOS Alarm

The receive optical power is excessively low because of the end face problem of the fiber jumper. The OAU board reports the MUT_LOS alarm.

Product

OptiX OSN6800,OSN8800,OTN

Fault Type

Abnormal optical power

Fiber

MUT_LOS

R_LOS

Symptom

In a network consisting of the OptiX BWS 1600G equipment, a fiber jumper on the ODF is removed and then inserted when the RPC laser is enabled. In this case, the fiber connector is burnt out. After the fiber and fiber jumper are replaced, the receive optical power of the RPC is excessively low (-53 dB).

The OAU board at the station reports the MUT_LOS alarm.

Cause Analysis

Measure the optical power on the entire optical path. The results are as follows:

• The transmit optical power on the FIU at the opposite station is normal.
• The optical power on the receive side of the ODF at the local station is normal. That is, the line attenuation is normal.
• The optical power at the receive end of the OAU board at the local station is excessively low.
• The input optical power at the IN optical interface on the FIU at the local station is excessively low.
• The fiber jumper between the SYS optical interface on the RPC and the IN optical interface on the FIU is normal.

According to the preceding results, it is determined that the exception is located between the ODF and the FIU. The possible causes are as follows:

• The fiber jumper between the ODF and the RPC is faulty.
• The RPC is faulty.

Procedure

1. Check the fiber jumper between the ODF and the RPC. It is found that the fiber jumper of the FC/PC-LSH/UPC type is used. The connector for the LINE optical interface on the RPC used on the OptiX BWS 1600G is of the LSH/APC type. The end face of the UPC connector is flat while that of the APC connector is tilted. As a result, there is air spacing between the LINE optical interface on the RPC and the connector of the fiber jumper from the ODF, and therefore the pump light of the RPC cannot be normally transmitted on the optical path. Consequently, the receive optical power is excessively low. After the fiber jumper is changed to FC/PC-LSH/APC, the system is normal.

Result

The problem is resolved.

Reference Information

• Disable the lasers on a Raman optical amplifier before performing any operations on the optical path with the Raman optical amplifier.
• The optical module interfaces for Raman optical amplifiers provided by different equipment vendors are different. Huawei and certain vendors use LSH/APC while other vendors use LSH/UPC.

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