Patent ID: 7809281

Claim:
An optical transmitter comprising: a first encoder that generates a differentially encoded signal from a data signal, the differentially encoded signal comprising a positive phase differential signal and a reverse phase differential signal, the reverse phase differential signal being an inverted version of the positive phase differential signal, the first encoder including a one-bit delay circuit, an exclusive OR circuit, and a differential circuit that is electrically connected to the exclusive OR circuit and outputs an inverted output signal and a non-inverted output signal, wherein the first encoder is configured so that an output signal of the exclusive OR circuit is input to the differential circuit, the inverted output signal of the differential circuit is input to the one-bit delay circuit, and an output signal of the one-bit delay circuit and the data signal is input to the exclusive OR circuit, the inverted output signal of the differential circuit being the positive phase differential signal, and the non-inverted output signal of the differential circuit being the reverse phase differential signal; a second encoder to which a clock signal and the positive phase and the reverse phase differential signals are input, the second encoder being configured to generate an electric RZ (return-to-zero) differential signal as an RZ signal in an electric area from the differentially encoded signal, the electric RZ differential signal comprising a positive phase RZ signal and reverse phase RZ signal which are generated by the second encoder by synchronizing the positive phase and the reverse phase differential signals with the clock signal; and a Mach-Zehnder interferometer type intensity modulator that generates an optical RZ-DPSK (differential phase shift keying) signal as an RZ signal in an optical area based on the electric RZ differential signal.