OPTICAL PHASE MONITOR CIRCUIT, OPTICAL RECEIVER, AND OPTICAL TRANSMISSION/RECEPTION SYSTEM

PROBLEM TO BE SOLVED: To extract nonlinear phase noise from phase noise of an optical multi-value modulation signal deteriorated by passing through an optical fiber transmission path and to monitor the nonlinear phase noise of the optical multi-value modulation signal.SOLUTION: The optical phase monitor circuit erases a data phase modulation component from electrical field data obtained by coherent-receiving an optical multi-value modulation signal to extract a phase error, and a change in a spectrum shape of a phase or electrical field acquired in converting, into a frequency region, electrical field data in which a phase error or a phase error with no data phase modulation component is a phase component is detected to monitor non-linear phase noise of an optical multi-value modulation signal.