How to deal with Abnormal Switching of SNCP service on ONT line board NS4 of Huawei OSN8800?

This is a case about handling abnormal switching of SNCP service on ONT line board NS4 of Huawei OSN8800.

Problem Description

100G line board TN54NS4 of a customer is configured with SNCP services. It is reported that multiple abnormal switching occurs on the live network, no fiber cut occurs on the optical cable, and the optical power is normal. Therefore, the root cause analysis needs to be performed.

The networking is as follows:

Alarm information:

ODU_SNCP_PS

Handling Procedure

1. Query the NMS alarms. It is found that the ODU_SNCP_PS alarm occurs multiple times and the SNCP switching occurs.

2. Check the current and historical alarms of the device. It is found that no fiber cut alarm is generated.

3. Continue to check the receive optical power of TN54NS4. It is found that the receive optical power is stable. Therefore, the switching is not caused by the bit errors caused by the power jitter.

4. According to the networking analysis (as shown in the following figure), it is found that SNCP switching occurs at a certain time, and services are switched from SNCP-to SNCP-protection. The switching cause may be caused by bit errors on the line. Because there is only one span between A-B, it can be confirmed that the problem is caused by this span.

5. The customer performed an OTDR test on the optical cable between the site A and the site B. It was found that the problem was caused by the reflection point of the optical cable.

6. The reflection point has a hop contact. After the connector is cleaned, the OTDR test shows that the reflection is normal and the SNCP switching is normal.

Root Cause

The fiber jumper connector is faulty. As a result, bit errors occur due to reflection and SNCP switching is triggered.

Suggestions and Summary

1. Alarm, performance, and optical power are the basic methods for locating WDM problems.

2. Common factors related to bit errors on the line side: a, non-linear effect; b, there is an abnormal reflection point on the line side

If you encounter same issue about NS4, you can refer to this article, it would be helpful.