The following description about 1+1 optical line protection, which is wrong?

The following description about 1+1 optical line protection, which is wrong?
A . The default switching mode is non-recovery
B . The default switching mode is double-ended switching
C . The initial difference between the main and standby input light defaults to 0
D . The main and standby input optical difference gate defaults to 5dB

View Answer

Answer: B