40G wavelengths are unavailable due to a DCM module connection problem.
Symptom
10G and 40G wavelengths are transmitted in an OptiX OSN 6800 network. The network topology is shown in the following figure. 40G wavelengths in two directions between station A and station G are unavailable. In addition, the performance of 10G wavelengths is lower than the expected performance although it is stable.
Cause Analysis
The optical power and OSNR after commissioning are normal and the optical fibers are newly routed. In this case, it is impossible that the PMD is excessively high. In addition, the link in the network is long, which results in use of many DCM modules. Therefore, it is possible that the DCM modules at a station are incorrectly connected.
Procedure
- Each station between station A and station G uses different DCM modules in two directions and the compensation distance of the two DCM modules differs by more than 40 km. In this case, incorrect connection of DCM modules at any station can make the 40G wavelengths unavailable.
- At each station, query the optical power of the optical amplifier boards and calculate the attenuation of the DCM modules. The attenuation of a DCM module increases with the compensation distance of the DCM module.
- Check station D. The result shows that station D is abnormal. That is, the attenuation of the DCM module connected to optical amplifier board A03 is lower than that of the DCM module connected to optical amplifier board A05.
- Check whether the DCM modules at station D are incorrectly connected. After rectifying the connections, confirm that the 40G wavelengths are available.
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