ONU Frequently Goes Online and Offline(2) - Unmatched Optical Fiber Connectors

SmartAX MA5600T/MA5603T Multi-service Access Module Troubleshooting: ONU Frequently Goes Online and Offline: TC-C6311 An ONT Frequently Goes Online and Offline Because of Unmatched Optical Fiber Connectors

This topic describes how to troubleshoot the fault when the deployed ONT frequently goes online and offline because the optical fiber connectors do not match.

Fault Description

When an ONT is installed in the deployment, the optical path attenuation is -23 dBm, which is within the normal attenuation range. After the optical fibers are connected, the LED of the PON port blinks. In addition, the ONT fails to register with the OLT normally, and the ONT goes online and offline frequently.

Alarm Information

The up and down alarms about the ONT (OT928) are generated on the OLT.

Cause Analysis

l The optical path attenuation is very large.

l The optical fiber connectors are not clean or not connected properly.

Procedure

Step 1 Use an optical power meter to measure the optical path attenuation. It is found that the optical path attenuation is -23 dBm, which is within the normal range of the optical path attenuation.

Step 2 It is suspected that the poor quality of optical signals is caused by the dirty optical fiber connectors of the ONT (OT928). Clean the optical fiber connectors, and remove and then insert the optical fiber connectors again. The fault, however, persists.

Step 3 Replace the ONT with another ONT (OT928) to conduct a test. The fault, however, persists, which indicates that the hardware of the ONT (OT928) is normal.

Step 4 Check the fiber patch cord of the ONT (OT928). It is found that the connector of the fiber patch cord does not match the optical fiber connector of the ONT. Though the connector of the fiber patch cord is square, the color is different. After verification, the optical fiber connectors used in the ONT (OT928) are green, square, and SC/APC.

NOTE

The BOM is 14130252, and the name is Patch Cord, SC/APC-FC/PC, Singlemode-G.652, 3mm, 3m.

Step 5 Replace the fiber patch cord with a correct fiber patch cord (SC/APC-FC/PC). As a result, the LED of the PON port is stable, and the ONT can register with the OLT normally.

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Suggestion and Conclusion

Currently, the type of the fiber patch cord used in the ONT (OT928) is seldom used in China, but is mostly used abroad. Therefore, note that you should use the correct fiber patch cord.

The greatest difference between green and blue fiber patch cords is as follows: The

interconnection section between the fiber patch cord with green connectors and the OT928 is oblique. The interconnection section between the fiber patch cord with blue connectors and the ONT is plane, which can result in 3-6 dBm optical attenuation.