The Minimum Optical Power of the SC2 Is Detected As -35 dBm

Because the fibers or the fiber jumpers are in fault, the minimum optical power of the SC2 is detected as -35 dBm.

Product

OptiX BWS 1600G, Huawei OSN3500, Huawei MA5683T, MA5608T

Fault Type

Optical power abnormity

Optical Supervisory Channel Unit

Symptom

A WDM chain with the OptiX BWS 1600G NEs is deployed in an office. The line attenuation between site A and site B is about 30 dB. One day, the received optical power of the two sites decreases by 8 dB and the OSNR also decreases. The optical power of the supervisory channel, however, remains unchanged, which is -35 dBm.

Cause Analysis

As the optical power of the supervisory channel remains unchanged, the cause does not lie in the fiber cable or out-frame ODF, but in the span between the in-frame FIU and OAU of the two sites.

Procedure

1. Test the optical power of MON interfaces of the OBU and FIU boards for transmitting signals to the opposite end at the two sites.
2. The optical power difference of the two MON interfaces is as slight as not more than 1 dB. It can be concluded that the no problem exists between the OBU at the transmit end and the RC port of the FIU, and no problem exists on the OUT interface of the FIU. The detected optical power of MON interfaces is 1% of the optical power of the OUT interface. If the OUT interface is faulty, the receiving of the SC2 at the opposite end is affected.
3. The previous analysis shows that the problem lies in the receive port of the FIU or the fiber from the FIU to OAU. There is low possibility that the two stations have the same fault. In addition, for further test, the optical path must be disconnected. To locate the problem for once, re-compose the fault locating scheme.
4. The cable problem can be excluded if the detected optical power of the SC2 is consistent with the actual optical power. The received optical power of the SC2 for receiving signals from the opposite end is tested after suspicion. The actual value is -35 dBm. If the transmitted optical power of the SC2 is -4.2 dBm, it is concluded that the attenuation of the supervisory channel is around 40 dB and the attenuation of the service channel is around 38 dB.
5. It can be concluded that cables and the fiber jumper between the FIU and ODF of the two stations are faulty. Then, test cables and the ODF with the cooperation of users. Locate and rectify the fault.

Reference Information

None.

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