Patent ID: 8406578

Claim:
A Mach-Zehnder waveguide type optical modulator, comprising: a thin plate with a thickness of 20 μm or less formed of a material having an electro-optical effect, an optical waveguide formed on a front surface or a rear surface of the thin plate, and a modulation electrode modulating light passing through the optical waveguide, wherein the optical waveguide comprises an input optical waveguide, branched optical waveguides, and an output optical waveguide, wherein the branched optical waveguides comprise an input branching portion in which the input optical waveguide is branched into a plurality of optical waveguides, an output merging portion in which the plurality of optical waveguides connected to the output optical waveguide is merged, and a parallel portion formed between the input branching portion and the output merging portion, and wherein at least one of the input branching portion and the output merging portion has a ratio l/d of a length l along a symmetry axis of the branched optical waveguides to a gap d of the optical waveguide in the parallel portion in the range of 33 to 100.