Dispersion compensation is not required for 40 Gbit/s and 100 Gbit/s coherent systems because the dispersion tolerance of coherent boards is large. NG WDM products do not support hybrid transmission of non-coherent and coherent networks.

Loopback is a common operation for routine maintenance and troubleshooting. Which of the following statements about loopback operations are incorrect?

In the scenario where the non-convergence OTU processes OTN standard signals, both A and B are WDM sites. After receiving the OTUk_TIM alarm on the client side, the OTU board at station A sends the OTUk_BDI alarm to the upstream. When the TIM follow-up action is disabled, the alarm is no longer transmitted to the downstream. When the TIM follow-up action is enabled, an SF event is generated. The WDM side of the OTU board at station B reports the ODUk_PM_AIS alarm, and the ODUk_PM_AIS alarm is transmitted downstream. The client equipment reports this alarm. After the WDM side of the OTU board at station B receives the OTUk_TIM alarm and the TIM follow-up action is disabled, the alarm is no longer transmitted to the downstream. When the TIM follow-up action is enabled, an SF event is generated. After the client side of station B processes the SF event, the client equipment reports the ODUk_PM_AIS alarm.