R_LOS alarm reported on an LWX2 board when its optical module normally receives optical signals

Question:
One OSN 1800 NE is used for point-to-point networking at each of sites A and B. According to a hardware loopback test on the client-side and WDM-client optical ports of LWX2 boards at site A, an R_LOS alarm is reported on the NMS. Site B has the same issue.
Analysis:
1. The receive optical power is lower than the lower limit.
2. The optical module is faulty.
Root cause:
None
Answer:
1. Use an optical power meter to measure the receive optical power of the optical module. It is found that the receive optical power is normal.
2. Replace the relevant optical module. The alarm is cleared.
3. According to relevant documents, if the WDM side emits light forcibly when no scrambled optical signal is added to the client side, the emitted light is white light. If the client side emits light forcibly when no scrambled optical signal is received on the WDM side, the emitted light is also white light. The current alarm detection mechanism cannot extract valid information from the white light. Therefore, the R_LOS alarm is reported.
4. Change the client-side service access rate of site A to 622 Mbit/s and add STM-4 optical signals from an SDH NE to site A. Then the R_LOS alarm is cleared on the client side of site A and the R_LOS alarm on the corresponding WDM side of site B is also cleared. Perform a hardware loopback using a fiber on the client side of site B. Then the R_LOS alarm is cleared on the client side of site B and the R_LOS alarm on the corresponding WDM side of site A is also cleared. After the preceding steps, this issue is resolved.
Suggestion and conclusion:
If the WDM side of an LWX2 board emits light forcibly when no scrambled optical signal is added to the client side, the emitted light is white light. If the client side emits light forcibly when no scrambled optical signal is received on the WDM side, the emitted light is also white light. The current alarm detection mechanism cannot extract valid information from the white light. Therefore, the R_LOS alarm is reported.

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