| 摘要 |
PROBLEM TO BE SOLVED: To solve such the problem that the conventional waveguide type variable light attenuator has large polarization dependence of the light attenuator when the light attenuation amount is increased in the variable light attenuator. SOLUTION: In the waveguide type variable light attenuator constituted of a waveguide formed on a substrate, the variable light attenuator includes an input waveguide, a first optical coupler, a second optical coupler, two arm waveguides connecting the first and second optical couplers, and an output waveguide. The first and second optical couplers are directional couplers that are structured including a region where the two arm waveguides approach. Particularly, the arm waveguide length is designed to be an integer multiple of the beat length obtained by dividing a used optical wavelength by the waveguide birefringence. COPYRIGHT: (C)2011,JPO&INPIT |
