Patent ID: 7689133
Filing Date: 2010-03-30
Classification: H04B,H04L

Abstract:
1. 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 front end including two delay interferometers and opto-electric conversion elements that receives the DQPSK optical signal and converts the DQPSK optical signal into an in-phase signal and a quadrature-phase signal; a clock and data recovery that regenerates a clock and a data signal based on the in-phase signal and the quadrature-phase signal; a multiplexer that multiplexes the in-phase signal and the quadrature-phase signal output from the clock and data recovery; a reception frame processing unit that detects frame synchronization based on the signal multiplexed by the multiplexer; and a controller that, based on a detection result from the reception frame processing unit indicating an out-of-frame-synchronization state, controls logical inversion operations in the clock and data recovery and controls a multiplexing timing in the multiplexer.