Patent ID: 8005373

Claim:
A signal reception device for receiving and demodulating an optical signal modulated by a Differential Quadrature Phase Shift Keying (DQPSK) modulation scheme, said signal reception device comprising: a reception demodulation unit that includes a plurality of delay interferometers and a plurality of opto-electric conversion elements for receiving the DQPSK optical signal and converting the DQPSK optical signal into an in-phase signal and a quadrature-phase signal; a multiplexer that multiplexes the in-phase signal and the quadrature-phase signal; a de-serializing unit that converts the multiplexed signals from the multiplexer into parallel signals; and a reception processing unit that receives the parallel signals from the de-serializing unit, and performs frame processing including frame synchronization processing, wherein the reception processing unit includes a frame synchronization circuit that establishes frame synchronization, a reception state identification circuit that identifies reception states based on the parallel signals, and a logic processing circuit that performs logic inversion, bit delay, and bit swap corresponding to a reception state other than an object reception state identified by the reception state identification circuit, and corresponding to a reception state related to a de-serializing timing in the de-serializing unit.