OPTICAL COUPLER

摘要

An optical coupler comprises a tapered waveguide formed so that a waveguide width may be narrower as going from a predetermined starting position toward an emission end of a light signal. A difference between a first coupling factor and a second coupling factor is set within a predetermined range. The first coupling factor is the coupling factor to a waveguide having the same width as that in a first position in an inherent mode in the case where the tapered waveguide is cut in the first position. A second coupling factor is the coupling factor to a waveguide having the same width as that In a second position where is separated at a predetermined distance from the first position along a direction toward the emission end in an inherent mode in the case where the tapered waveguide is cut in the second position.