Patent ID: 8340532

Claim:
An optical signal receiving apparatus comprising: a serial to parallel conversion section for parallelizing an electric signal array generated from an optical signal received and subjected to multi-valued phase modulation; a bit separation circuit for separating the electric signal array parallelized by the serial to parallel conversion section into an odd number part and an even number part; a splitter section for splitting each of the odd number part and the even number part outputted from the bit separation circuit into plural; a plurality of logical operation circuits for making a logical operation on the odd number part and the even number part after splitting outputted from the splitter section; a plurality of synchronizing detection circuits for detecting the detection state of a fixed pattern in parallel by comparing the output of each of the plurality of logical operation circuits with the fixed pattern for frame synchronization extracted from the received optical signal; a selector for selecting the output from any of the plurality of synchronizing detection circuits; and a selector control section for controlling the selector to output a signal array outputted from the synchronizing detection circuit when detecting a notification of the detection state of the fixed pattern from the one synchronizing detection circuit.