US Patent 7512336 Optical failure detection using polarization

Systems and methods for evaluating an optical communication link are provided. The evaluation is based on a polarization analysis of received optical power. Such an analysis is able to differentiate between received noise and received optical signal power, even for typical multi-channel signals. By appropriately analyzing the polarization of received optical power, the link quality can be evaluated. Failures may be detected and optical signal to noise ratio may be measured.