Patent ID: 8923668

Claim:
A light-receiving method of receiving light outputted from a multi-core optical fiber, the method comprising the steps of: disposing, at a position where light outputted from the multi-core optical fiber reaches, a light-receiving waveguide which guides light outputted from a core of the multi-core optical fiber, the light-receiving waveguide having a refractive index structure of depressed-type or trench-assisted type in which a core is surrounded by a layer having a refractive index lower than that of a cladding, wherein the layer constituting the depressed type or the trench-assisted type is constituted by only solid having a refractive index lower than that of the cladding, or formed as a layer in which an average refractive index thereof is lower than that of the cladding as a result of having holes in the solid; causing light to enter a first core on a first end face of the multi-core optical fiber; guiding light outputted from a second core through the light-receiving waveguide, the second core being different from the first core on a second end face opposing the first end face of the multi-core optical fiber; and receiving the light having been guided through the light-receiving waveguide.