Abstract: For communicating over optical routes, route monitoring and protection are provided. In routes carrying signals on each of a number of wave lengths a tapped fraction of the signal is demultiplexed and an individual wave length is detected for determining performance and for triggering switching to alternative monitored routes carrying the same signal. Switching of all wave lengths if one shows faulty, with either a single wave length or all wave lengths being monitored is shown. Performance of a long wave length component is employed to determine route quality for shorter wave lengths as well. In bi-directional communication systems, performance of a wave length moving in one direction through a route determines route quality for transmission in the other direction, as well. Progressive sampling and digitization of the tapped signal and comparison to a digitized reference enables high sensitivity of monitoring.