Patent ID: 7706695

Claim:
An optical DQPSK receiver apparatus, comprising: an optical splitter for splitting an optical DQPSK signal and for guiding the signal to a first optical path and a second optical path; a delay element provided in the first optical path; a phase shift element provided in the second optical path, for shifting the phase of an optical signal by nπ/8 (where n is an odd number); a coupler element for combining an optical signal output from said delay element and an optical signal output from said phase shift element and generating first and second optical signals; a photo detector circuit for generating a detection signal corresponding to the first and the second optical signals; and a recovery circuit for generating two-bit information based on the detection signal, wherein said recovery circuit comprises: a first decision unit for outputting one-bit information based on the detection signal; and a second decision unit for outputting one-bit information based on a squared value of the detection signal.