<P>PROBLEM TO BE SOLVED: To perform control logical inversion and other control to transit to the object reception state, regarding an optical signal receiving device that receives, and demodulates an optical signal modulated by DQPSK, DPSK. <P>SOLUTION: The disclosed device includes: a front end 1 including a delay interferometer and an opto-electric conversion element, that receive the DQPSK optical signal and convert it into an in-phase signal I and an orthogonal signal Q; a clock-reproducing parts 3, 4 that reproduce clock signals CLK, based on the in-phase signal I and the orthogonal signal Q; a multiplexing part 6 that multiplexes the in-phase signal I and the orthogonal signal Q; a reception frame processing part 9 that detects frame synchronization, based on the signal multiplexed by the multiplexing part 6 and de-maps the received frames; and a control part 10 that, based on out-of-frame synchronization information (LOF/OOF) from the reception frame processing unit 9, performs logical inversion control in the clock reproducer 3, 4, multiplexing timing control in the multiplexing part 6, and controls the delay interferometer in the front end 1 so as to transit to the object receiving state. <P>COPYRIGHT: (C)2007,JPO&INPIT 
OPTICAL SIGNAL RECEPTION DEVICE