Patent ID: 7848644

Claim:
A method comprising: splitting an incoming optical signal into a first and a second optical signals; sending the first and the second optical signals to a first and a second equipments in an optical network node, respectively, the second equipment being a protection module for the first equipment; monitoring a first and a second outgoing optical signals from the first and second equipments; using a switch to select only one of the first and the second outgoing optical signals from the optical network node; outputting the only one of the first and the second outgoing optical signals selected; declaring a failure of the optical network node if only one of the first and the second outgoing optical signals has failed; and if both of the first and the second outgoing optical signals have failed, determining a failure is outside of the optical network node, and maintaining a signal selection state of the switch to continue outputting the only one of the first and the second outgoing optical signals in the same direction without declaring that the optical network node has failed.