Patent ID: 8270848

Claim:
A method for receiving a differential quadrature phase shift keying (DQPSK) signal, comprising: splitting, by a splitter, the DQPSK signal to obtain two optical signals; optically bandpass filtering the two optical signals respectively by using two optical bandpass filters that respectively have a positive frequency offset and a negative frequency offset from a central frequency of the DQPSK signal; and photoelectrically converting the filtered optical signals respectively to obtain data signals; wherein the DQPSK signal is obtained by: pre-coding input data according to pre-coding transforming equations of I k =ū v I k-1 +ūv Q k-1 +uvĪ k-1 +u v Q k-1 I k =ūI k-1 Q k-1 +vĪ k-1 Q k-1 +uĪ k-1 Q k-1 + v I k-1 Q k-1 Q k =ū v Q k-1 +u v Ī k-1 +ūvI k-1 +uv Q k-1 or Q k = v Ī k-1 Q k-1 +uĪ k-1 Q k-1 +ūI k-1 Q k-1 +vI k-1 Q k-1 to obtain two driving signals; modulating an input optical carrier respectively by using the two driving signals, so as to obtain a real-part signal and an imaginary-part signal; and combining the real-part signal with the imaginary-part signal to generate the DQPSK signal.