Patent ID: 8666200

Claim:
An optical modulation device, comprising a semiconductor Mach-Zehnder modulator splitting and propagating input light, and multiplexing and outputting the propagated lights, wherein the semiconductor Mach-Zehnder modulator includes: a first optical waveguide and a second optical waveguide propagating splitted lights; a first electrode applying a first modulation signal and a first DC bias voltage to the first optical waveguide; and a second electrode applying a second modulation signal and a second DC bias voltage to the second optical waveguide, wherein a length of the first electrode is set to be L 1 , a length of the second electrode is set to be L 2 , the first DC bias voltage is set to be A, and the second DC bias voltage is set to be B, the first DC bias voltage and the second DC bias voltage are applied so that a rate of a product AL 1 of the length of the first electrode L 1 and the first DC bias voltage A and a product BL 2 of the length of the second electrode L 2 and the second DC bias voltage B is a pre-determined value under the condition of A:B≠(L 2 ) 1/2 :(L 1 ) 1/2 .