Patent ID: 8380023

Claim:
A waveguide-type optical circuit comprising: an optical coupler being an optical branch coupler constructed from waveguide cores which are closely arranged to each other; and dummy patterns that lay along sides of the waveguide cores in the optical coupler for preventing optical major axes of the waveguide cores from inclining, wherein the optical coupler is a directional coupler, a length of the dummy pattern is equal to or greater than a length of a coupling portion, the coupling portion being a region in which a coupling efficiency of the optical coupler is greater than 0%, the dummy pattern extends to a region in which the waveguide cores curve so that a gap between the waveguide cores gradually spreads from a portion in which the waveguide cores are most closely arranged to each other, and a gap between the dummy pattern and the waveguide core in the optical coupler is equal to or greater than a gap size between the waveguide cores in the optical coupler.