Patent ID: 7289703

Claim:
An optical waveguide device, comprising: a substrate having an electro-optical effect; and a Mach-Zehnder type optical waveguide formed on said substrate and including a branching waveguide for branching propagation light into two propagation lights, two linear waveguides for propagating the two propagation lights branched by said branching waveguide, and a multiplexing waveguide for multiplexing the propagation lights from said two linear waveguides; said multiplexing waveguide including two input waveguides for inputting the propagation lights from said linear waveguides, a waveguide coupling element for coupling said two input waveguides with a distance d 1 , and two output waveguides branched from said waveguide coupling element with another distance d 2 ; the distance d 1 in said waveguide coupling element being set to less than one half of width w 01 at a portion at which each of said input waveguides is connected to said waveguide coupling element; width w w1 of said waveguide coupling element on said input waveguides side being set to 2.5 times to 3.5 times the width w 01 ; the length of said waveguide coupling element being set so that light propagating in one of said two input waveguides is branched to said two output waveguides with a power ratio of 1:1.