40G WDM OLP switching

1. For a 40G system (DQPSK/ODB), because the dispersion window of the 40G optical module is relatively narrow, the dispersion difference between the working and protection channels must be small and generally within ±100 ps/nm.
2. Currently, the LSXL boards all have built-in TDC modules on the live network. In this project, 12LSXL boards are delivered, and the dispersion compensation is ±800 ps/nm. In the Dispersion Compensation Management window, the Fine Tune Switch parameter is provided and is set to Enable by default. When a dispersion change is detected during the running, fine tuning is performed, which will not interrupt services. If the WDM detects the LOS or LOF alarm, it will start the TDC coarse adjustment, which will interrupt services for 1 minute (time taken by the board TDC to search for the dispersion value).
3. When a fiber cut triggers OLP protection switching and the LSXL board detects a LOS or LOF alarm, the TDC module starts the coarse adjustment, which will interrupt services for several minutes. This is because the coarse adjustment cannot be disabled for the TDC (the function of disabling the coarse adjustment is not provided on the NMS). During the switching, the coarse adjustment is started, interrupting services for several minutes.
4. Currently, the dispersion value is searched during OLP protection switching in a 40G system, which takes several minutes.

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