Patent ID: 8644715

Claim:
A method for monitoring a phase difference based on DQPSK (Differential Quadrature Reference Phase Shift Keying) modulation, comprising the following steps of: performing a n th power multiplication operation respectively on a first differential current signal and a second differential current signal output after DQPSK demodulation so as to correspondingly obtain a first monitor signal and a second monitor signal, where, n is a positive integral multiple of 4; monitoring a phase difference between two arms of a first demodulator according to the first monitor signal, wherein, the first demodulator is used to perform phase rise and phase cancellation operations on optical signals transmitted by the two arms thereof and output a first phase rise optical signal and a first phase cancellation optical signal for obtaining the first differential current signal; monitoring a phase difference between two arms of a second demodulator according to the second monitor signal, wherein, the second demodulator is used to perform phase rise and phase cancellation operations on optical signals transmitted by the two arms thereof and output a second phase rise optical signal and a second phase cancellation optical signal for obtaining the second differential current signal.