Patent ID: 7542631

Claim:
An optical transmitter comprising; precoding means for providing an output which is the same as the previous output when an input binary digital signal is 0, and an output which differs from the previous output when an input digital signal is 1, bandwidth restriction means for generating a ternary duobinary signal by restricting the bandwidth of a binary digital signal output from the precoding means, and a Mach Zehnder light intensity modulator driven by an output signal of the bandwidth restriction means, wherein the Mach Zehnder light intensity modulator has a substrate of X-cut Lithium-Niobate, on which a signal electrode, a first ground electrode and a second ground electrode are provided, the signal electrode is located between a first optical waveguide and a second optical waveguide which constitute the Mach Zehnder light intensity modulator, the first ground electrode is located opposite side of the signal electrode relative to the first optical waveguide, the second ground electrode is located opposite side of the signal electrode relative to the second optical waveguide, and electrical fields between the signal electrode and the first/second ground electrodes cross the first/second optical waveguides parallel to a surface of the substrate.