The present invention provides a method and system for monitoring
composite optical signals carried over plural fiber-optic lines within an
optical network. Methods and systems in accordance with the present
invention each utilize a single OPM to monitor each one of a set of
sample proportions of composite signals split off from respective
fiber-optic lines. In one embodiment, an optical performance monitoring
system comprises a plurality of fiber-optic lines, each fiber-optic line
carrying a respective composite optical signal, a plurality of optical
taps, each optical tap being optically coupled to a respective one of the
fiber-optic lines and splitting a portion of the composite optical signal
thereof, a plurality of optical switches, each optical switch being
optically coupled to a respective one of the optical taps and comprising
either an Open configuration and a Closed configuration, an optical
coupler, and an Optical Performance Monitor (OPM).