Cross-connections for 10 wavelengths are done successfully in a ROADM site. Due to some fiber link problem with customer site, not all wavelengths are available in one particular path. Suppose there are only 4 wavelengths coming out,
however, unusual noises are appearing (which results in 10 wavelengths coming out) when using OSA to measure the TOA port of RMU9.
Remove or disable any cross-connections of unused channel on the ROADM NE.
There is no alarm detected in T2000, therefore, possible causes of this problem are
1. Optical power too high which cause Noise power to increase significantly.
2. Hardware (board) is faulty.
1. The attenuation of the pair WSD9 + RMU9 boards is check to verify the configured attenuation. The attenuations are set to auto in WSD9, so the board automatically set a default value for attenuation in both WSD9 + RMU9 boards. From
this point, we know that the optical power is not at the highest value, so we try to increase attenuation of both boards. Then, we measure again with OSA, however, the noises are still appearing. Thus, it seems the possibility of high optical
power is voided.
2. We disable all the cross-connections except one. Then we check with OSA and the wavelength is appearing normally. Then we enable the cross-connections one by one and check with OSA each time we enable one cross-connection. We noticed that all the noises appear when we enable the cross-connections that are not in use yet. Then we try to disable all the unused cross-connections except the original 4 wavelengths that suppose to pass-through the site and we found that the noises are gone when we measure with OSA. From this point, we can conclude that the boards are not faulty and the noises are appearing due to the cross-connections of unused channels.
The possible cause of this problem is leakage of minimal power from existing 4 channels that are going through the WSD9 + RMU9.
Only enable or create the cross-connections that are currently available on the network in order to prevent the unusual appearance of noise.