Patent ID: 7187860

Claim:
A polarization anomaly locator system for an optical communication network, said system comprising: a transmitter configured to transmit a probe signal on a network having first and second optical transmission paths and a loop-back path, said first and second optical transmission paths supporting communication of optical signals in opposite directions on said network, said loop-back path coupling at least a portion of said probe signal from said first transmission path to said second transmission path as a returned probe signal; said transmitter having a modulation section optically communicating with said probe signal source, said modulation section configured to impart a depth of modulation on said probe signal at a particular frequency and comprising an amplitude modulator configured to modulate the amplitude of said probe laser output signal at a carrier frequency, and a polarization modulator configured to modulate the polarization of said probe laser output signal at a polarization frequency, said amplitude and polarization modulators thereby providing a modulated probe laser output signal, said transmitter further comprising: an optical switch configured to selectively switch said modulated probe laser output signal onto an optical path in response to a control signal, a loading laser configured to provide a loading signal, a loading laser optical switch configured to switch said loading signal on a loading signal optical path in response to a loading laser control signal, and a power combiner configured to combine optical power on said optical path and said loading signal optical path as a power combiner output; and a receiver coupled to said second transmission path and configured to receive said returned probe signal and to provide an output indicating an approximate position of a polarization anomaly in said optical communication network in response to said returned probe signal.