Cause analysis
In the case of WDM equipment service interruption, the common troubleshooting method is to check boards one by one from the faulty point to the upstream section.
The possible causes of the fault are as follows:
- The TN11NS2 board at site A is faulty.
- At site B, the TN11NS2 board cannot receive services properly from site C. This may be due to a line fault or a hardware fault.
- A cross-connection fault exists between the two TN11NS2 boards at site B. The fault may be located on the TN11NS2 board, the cross-connect board or the backplane.
- At site C, a cross-connection fault exists between the TN11TDX and TN11NS2 boards. The fault may be located on the TN11NS2 board, the TN11TDX board, the cross-connect board or the backplane.
Procedure
- Query the alarms and performance events in the received services on the WDM side of the TN11NS2 board at site A.
- The TN11NS2 board reports no alarm. The pre-FEC BER is 8 and the post-FEC BER is 0. No bit errors related to OTU2/ODU2 services are generated.
- Enable the non-intrusive monitoring function of four ODU1 channels on the TN11NS2 board. ODU1_PM_SS alarms are generated on the four channels.
The TN11NS2 board at site A and the lines from site B to site A are normal. The alarms are transmitted transparently from upstream sites.
- Ensure that there are no alarms on the system side of the BD-1 TN11NS2 board.
- Ensure that there are OTU2_DEG and ODU2_PM_DEG alarms on the WDM side of the BD-2 TN11NS2 board.
- Query performance events in the received services on the WDM side of the BD-2 TN11NS2 board. The pre-FEC BER is 8.
- Query history alarms on the BD-2 TN11NS2 board. It is found that the transient OTU2_DEG and ODU2_PM_DEG alarms are reported for several times.
- Query history performance events in the received services on the WDM side of the BD-2 TN11NS2 board. The pre-FEC BER varies in the range of two to eight in several periods.
- Query history performance events in the received services on the WDM side of the BD-2 TN11NS2 side. The received optical power varies in the range of -11 dBm to -7 dBm.
The fault is caused by degradation of the receive optical power of the BD-2 TN11NS2 board at site B. Still, the cause of the degraded receive optical power needs to be identified.
- Ensure that current alarms and performance events of the input optical port on the upstream OA of the BD-2 TN11NS2 is normal.
- Query history alarms and performance events of the input optical port on the upstream OA of the BD-2 TN11NS2 board. The transient MUT_LOS alarm is reported once and the minimum input optical power is -60 dBm in several performance periods.
- Query history alarms and performance events of the upstream TN12FIU board of the BD-2 TN11NS2 board. No history alarm is generated on the TN12FIU board and the input optical power decreases by 8 dBm.
- Query history alarms and performance events of the upstream TN11SC2 board the BD-2 TN11NS2 board. No history alarm is generated on the TN11SC2 board and the minimum input optical power is -60 dBm in several performance periods.
Transient interruption occurs on the main optical path from site C to site B. An optical cable fault can be identified because the input optical power received by the OA and the OSC decreases.
NOTE:
Lines are interrupted transiently. Due to different detection sensitivity of each board, part of the boards do not report MUT_LOS alarms and the minimum receive optical power of these boards is not -60 dBm. However, by querying the LOS and IN_PWR_LOW alarms in the history alarm and the maximum and minimum values in history performance events, check whether the optical power degrades.
- Ensure that history performance events of the transmit optical power from site C to the OA at site B is normal.
- Ensure that history performance events of the transmit optical power from site C to the TN12SC2 board at site B is normal.
By performing Step 3 and 4, it is further identified that the fault is due to a defective customer optical cable.
