The BA2 board at station A reports an abnormal alarm. After the input optical wavelength is changed to the range from 1530 nm to 1560 nm, the fault is rectified.
Symptom
The OptiX OSN 1500 equipment at stations A and B form the 1+1 linear multiplex section protection (MSP). Station A contains the SLD4 board, the CXL4 boards (working and protection boards), and two BA2 boards. Station B contains the SLD4 board, the CXL4 boards (working and protection boards), and one BA2 board. The optical interface on the SLD4 board is of the Ve-4.2 type, and the optical interface on the CXL4 board is of the L-4.1 type. The output optical power of each BA2 board is +14 dBm. The distance between stations A and B is 120 km.
When the commissioning test is performed after the fibers are connected properly, the PUM_BCM_ALM and OUT_PWR_ABN alarms are detected on the two BA2-S boards of station A, but no alarm is detected on the BA2-D boards of station B.
Cause Analysis
The PUM_BCM_ALM alarm indicates that the driving current of the remote pump laser crosses the specified threshold. When the driving current exceeds the specified maximum working current, the PUM_BCM_ALM alarm is generated.
The OUT_PWR_ABN alarm indicates that the output optical power is abnormal. When the input optical power is within the specified range (BA: -6 dBm to +3 dBm; PA: -36 dBm to -10 dBm), no alarm is generated for the working current, and the working current is not adjusted, the output optical power exceeds the specified range (BA: +13 dBm to +15 dBm; PA: gain < 19 dB), the OUT_PWR_ABN alarm is generated. Generally, the following causes are possible. The EDFA module is aged or faulty. The driving circuit is damaged or the drive current detection circuit is faulty.
Procedure
- Check the performance value of one BA2-S board of station A on the T2000.
- Right-click the NE of station A in the Main Topology and choose NE Explorer.
- Select one BA2 board from the board list in NE Explorer.
- Select from the Function Tree.
- Select Gauge in the right pane, and then select Transmitted Optical Power and Receive Optical Power. In Display Options, select Display Current Value.
- Click Query.
- Analyze the data. In the case of the BA2 board, the input optical power is -2.6 dBm, which is within the specified range (-6 dBm to +3 dBm); but the output optical power is +12.9 dBm, which is beyond the specified range (+13 dBm to +15 dBm). Hence, the OUT_PWR_ABN alarm is generated. In the case of the EDFA module, the specified maximum working current is 138 mA, but the actual working current is 188 mA. Hence, the PUM_BCM_ALM alarm is reported.
- Replace one BA2 board.
- Check the alarms on the T2000. If the OUT_PWR_ABN and PUM_BCM_ALM alarms persist, rectify the fault of the board.
- Check the fiber connection. At station A, the BA2 board is connected to the CXL4 board. The output optical wavelength of the CXL4 board ranges from 1280 nm to 1335 nm and is beyond the specified amplification range (1530 nm to 1560 nm) of the EDFA module. Hence, the input optical signals cannot be amplified properly.
- Remove the fiber jumper between the CXL4 board and the BA2 board.
- Connect the SLD4 board to the BA2 board by using fiber jumpers.
- Query the current alarms of the NE. The abnormal alarms are cleared automatically.
Related Information
In the project or maintenance work, the related specifications (such as the wavelength and power of the input optical signals and the power of the output optical signals of the BA2/BPA boards) must meet the specified requirements.
The working wavelength of the PA module is 1550.12 nm. When the working wavelength of the PA module is highly offset from 1550.12 nm, the offset value of the input optical power and output optical power is high. The normal input optical power ranges from -36 dBm to -10 dBm. If the input optical power is too high, the life of the laser may be shortened. If the input optical power is too low, the EDFA module cannot amplify the optical power properly.
The input working wavelength of the BA module ranges from 1530 nm to 1560 nm, which is the 1550 nm window wavelength. When the input working wavelength of the BA module is beyond the range, the BA module cannot amplify the input optical signals properly. The PUM_BCM_ALM and OUT_PWR_ABN alarms may also be generated. The normal input optical power of the BA module ranges from -6 dBm to +3 dBm. If the input optical power is beyond the range, an alarm is generated, indicating that the input optical power is abnormal. If the input optical power is too high, the life of the laser may be shortened.
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