Summary:
The TN55NPO2(E) board reports an OTU2_LOF alarm on corresponding channels because of large leakage current on the X5R capacitor of the board. This problem has been reported several times on live networks.
Huawei osn 8800 products:
[Problem Description]
Trigger condition:
None
Symptom:
When the problem occurs, the TN55NPO2(E) board reports an OTU2_LOF alarm on corresponding channels and services on the channels are interrupted.
Identification method:
The problem is caused by defective GN2405 components, which are used only on TN55NPO2(E) boards. If a TN55NPO2(E) board reports an OTU2_LOF alarm on corresponding channels, identify whether the board is involved in the problem using either of the following methods:
- On the peer board, run the command for bypassing the PLL for each of the channels with the OTU2_LOF alarm. If the alarm is cleared and services are restored on the channels, the board is involved in the problem.
- On the peer board, run the command for collecting the value of the LOL status register inside the GN2405 component for about 200 times for each of the channels with the OTU2_LOF alarm and send the collected data back to Huawei R&D for identification.
[Root Cause]
The GN2405 components in a lot are defective. To be specific, the X5R filter capacitors of the LF pins on the GN2405 components in the lot generate large leakage current (as large as uA) because of cracks or gaps caused by unqualified materials, mechanical stress, or electrical stress, or because of environment changes such as temperature or humidity changes. When the problem occurs on a GN2405 component, the PLL inside the component works abnormally and locks a non-service frequency, causing the OTU2_LOF alarm.
[Impact and Risk]
The TN55NPO2(E) boards are faulty, affecting customer experience.
The OTU2_LOF alarm is reported and services on corresponding channels are interrupted.
[Measures and Solutions]
Recovery measures:
Perform either of the following recovery measures:
- Replace the faulty boards.
- Run the command for bypassing the PLL for each of the channels with the OTU2_LOF alarm. In this manner, the OTU2_LOF alarm can be cleared and services can be quickly restored. Pay attention to the following points when running the command for bypassing the PLL:
- If you run the command for a channel without the OTU2_LOF alarm, services on the channel will be interrupted for approximately 1s. Therefore, confirm the channels with the OTU2_LOF alarm or perform SNCP switching to switch services on a faulty board to the related protection board before running the command.
- The command applies only to V100R006C01SPC200 and later versions.
- You can run the command for channels that do not carry services to prevent the problem.
- Do not perform cold resets or power-off restarts on boards where services have been restored by running the command. If such boards undergo cold resets or power-off restarts, run the command again on the boards.
Workarounds:
None
Preventive measures:
Perform either of the following preventive measures to resolve the problem:
- Software Solution：On the peer board, run the command for bypassing the PLL for each of the channels with the OTU2_LOF alarm, achieving quick service restoration. Do not run the command for a channel that has no OTU2_LOF alarm; otherwise, services on the channel will be transiently interrupted for approximately 1s.
- Hardware Solution：Replace the faulty board with a newly delivered board.Replace the X5R filter capacitor with the X7R filter capacitor used on the LF pin of the GN2405 component. The BOM list has been updated in June, 2013.
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