OPTICAL WAVEGUIDE CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide an optical waveguide circuit of a small size which is little in connection loss to an optical fiber. SOLUTION: A circuit of a basic optical waveguide 6 is formed on a substrate 1 and one end side of a narrow-width straight waveguide 8 of the width narrower than the width of the basic optical waveguide 6 is connected to a light input end and light output end 4 of this circuit. A tapered waveguide 7 of the width expanding from one end side toward the other end side of the narrow-width straight waveguide 8 is connected with the end side of the narrow- width straight waveguide 8. The width direction mode field diameter on the expanded width end face 2 of the tapered waveguide 7 is made nearly coincident with the mode field diameter of the optical fiber 15.