US Patent 10122489 Polarization state detector, optical transmitter, and optical receiver

An optical transmitter transmits optical signal including a first signal and a second signal. The second signal is subjected to change in a polarization state relative to a polarization state of the first signal. An optical receiver analyzes a reception characteristic of the second signal and detects, based on the analyzed result, a polarization state of the first signal indicative of a higher signal quality than that of the second signal.