PROTECTING COVER FOR SINGLE-MODE DIRECTIONAL COUPLER

摘要

PURPOSE: To provide a protective cover for the direction coupler of a single mode without causing deviation in a phase in the direction coupler even when temperature change is present. CONSTITUTION: At least two opened cover components 2 and 3 composed of at least two optical waveguide bodies mutually welded along a connection section to be introduced and led out and connected to an annularly closed cover are provided. In this case, the material of the cover components 2 and 3 is provided with the same expansion coefficient as the optical waveguide material of the direction coupler of the single mode and this cover 1 is mechanically firmly connected to the optical waveguide bodies 4 and 5 to be introduced and led out while opening the connection section 10. In the case that the temperature change is present, the connection section 10 is air-tightly sealed by the cover 1 so as not to generate mechanical stress in the connection section 10.