Patent ID: 7116917

Claim:
An optical transmitter comprising: a light source which is a single mode longitudinal light source; a pre-coding device that receives an NRZ signal and generates a pre-coded NRZ signal or a differential pre-coded NRZ signal whose logic inverts each time a mark bit is input; an optical phase modulating device that uses a Mach-Zehnder optical intensity modulator driven by either the pre-coded NRZ signal or the differential pre-coded NRZ signal generated by the pre-coding device, and carries out optical phase modulation of the optical phase of a single longitudinal mode optical signal from the light source using the pre-coded NRZ signal or the differential pre-coded NRZ signal generated by the-coding device and outputs an RZ optical phase modulated signal in which a plurality of duobinary optical signal components are included in an optical RZ signal spectrum with carrier suppressions; and an optical filter device that converts the RZ optical-phase modulated signal generated by the optical phase modulating device to an RZ optical intensity modulated signal and outputs an RZ optical intensity modulated signal from an output terminal.