Abstract: The present disclosure provides a system, apparatus and method to provide for monitoring of characteristics of optical signals, as part of wavelength division multiplexed signals for example, transmitted over a network infrastructure. The characteristics of each optical signal may be monitored and maintained at desired values in order to optimize system performance. A system including a coherent detector, as part of a coherent receiver for example, may be employed to associate each transmitted optical signal with a modulated source. Control signals generated by the system can then be provided to elements of the modulated source to control characteristics, such as optical power, optical frequency, and optical phase, for example, of the transmitted optical signal.