To reduce the mounting area of an optical circuit using a fiber fused stretchable optical component.

In the fiber fused stretchable optical component in which a plurality of fibers are arrayed and then heated, fused and stretched, the fused stretchable part is fixed at the end of a substrate. From both ends of the fused stretchable part on the substrate, fibers are bent with a certain radius of curvature R and drawn out of a mounting case. As a result, the length of the coupler case is shortened, with the area for processing an extra fiber length reduced, thereby reducing the area for mounting parts.