The following description of 1+1 and 1:1 optical line protection, the fault is (). (Multiple Choice)

In the electrical layer overhead processing-sink function, the signal flow is from the OCh to the client direction, the PM ODUkP is detected first, and then the TCM ODUkT is detected.

On the ROADM board, you need to configure the virtual optical layer service before the optical power is commissioned. Otherwise, the ROADM limit board blocks all wavelengths by default.

In the WDM networking design, as long as there are enough EDFA cascades to compensate for the loss of optical power during transmission. Then the system can transmit a long distance without restriction.

Since the nonlinear effect is generated, its influence on the service signal cannot be repaired. Therefore, the treatment of the nonlinear effect of the existing network is to avoid the occurrence of nonlinear effects.