PURPOSE: To obtain the optical switch which is tolerant to the coupling rate setting error of a directional coupler and has a superior extinction ratio by composing an optical switch element of three optical waveguides, i.e., by-pass optical waveguides in addition to input optical waveguides and output optical waveguides and including two Mach-Zehnder optical interferometer circuits which have an optical path length difference equivalent to a 1/2 wavelength in an OFF state in the optical waveguide element.
CONSTITUTION: Parts of the by-pass optical waveguides 33a and 33b come close to the input waveguides 31a and 31b at two places to constitute two directional couplers 34a and 35a. Similarly, other parts of the by-pass optical waveguides 33a and 33b come close to the output optical waveguides 32a and 32b at two places to constitute two directional couplers 34b and 35b. Then the 1st and 2nd Mach-Zehnder optical interference circuits 38a and 38b which have the optical path length difference of 1/2 wavelength in the OFF state are provided. Therefore, the two couples of directional couplers 34a and 35a, and 34b and 35b are coupled in mutually opposite-phase relation to each other and their coupling operations cancel each other.
OKUNO MASAYUKI
KATO KUNIHARU
KATO KATSUMI
