PURPOSE: To provide an optical signal receiver with which high-speed processing is made possible with relatively simple constitution by constituting a more specific processing means of observed interference patterns effective for application as an identifier of high-speed digital light signals.

CONSTITUTION: Locally emitted light synchronized with the signal light is generated by a phase synchronizing means 2. This locally emitted light is modulated by a modulating means 3 and the light rays of the respective frequency components generated by modulation are respectively spatially separated by a frequency separating means 12 and are arranged in order of these frequencies. The signal light and the locally emitted light outputted from a frequency separating means are received by a photodetector array 1. The spatial distribution of the photoelectric currents thereof is observed and the photoelectric currents between the adjacent photodetectors of the photodetector array 1 are compared by a comparator 9 and the difference therebetween is outputted.