1 channel + 1 channel (1+1)
1 Channel + 1 Channel is a method of protecting data traffic in which a protection channel is available to each traffic channel.
In optical transmission systems, the fiber link of the protection channel can be routed over a path that is separate from the traffic channel. In this case, the traffic is routed via bridge circuits to both transmitters, the one with the protection signal and the one with the traffic. This allows the protection signal to be routed very quickly to the traffic signal if an error occurs there.