OPTICAL RECEIVER AND OPTICAL SPACE COMMUNICATION SYSTEM

[Problem] To provide a technology in which a differential phase modulation manner can be applied to a space environment for satellite mounting.[Solution] This optical receiver 10 includes a differential optical detection unit 110 and a digital signal processing unit. The differential optical detection unit 110 has: an optical delay interferometer 210 which controls, for one bit, a delay between two optical signals, which are branched from an optical phase modulation signal, causes the two optical signals to interfere with each other, and outputs the two optical signals that interfere with each other; a wideband balanced optical detector 240 which performs differential optical detection for the two output optical signals and outputs a main signal; and a peak signal detection unit 230 which outputs a peak signal that indicates the intensity of a differential light between the two output optical signals. The digital signal processing unit has: a level fluctuation frequency suppression unit 320 which suppresses a level fluctuation frequency component of the peak signal; an optical delay interference control unit 330 which generates an optical delay interference control signal, which is overdrive-amplified, on the basis of the peak signal of which the level fluctuation frequency component is suppressed and applies the generated optical delay interference control signal to the optical delay interferometer 210; and a data recovery unit 310 which recovers output data on the basis of the main signal from the wideband balanced optical detector 240.