Receiving method and separating apparatus for light outputted from multi-core optical fiber

A separating apparatus of separating light outputted from a multi-core optical fiber, the separating apparatus comprising a light-receiving waveguide which guides light outputted from cores of the multi-core optical fiber, the light-receiving waveguide having a plurality of cores, and a refractive index structure of depressed-type or trench-assisted type in which each of the cores is surrounded by a layer having a refractive index lower than that of a cladding,

• wherein the light-receiving waveguide is disposed at a position where light outputted from the multi-core optical fiber reaches,
• 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,
• wherein light enters one or more cores on a first end face of the multi-core optical fiber, and
• wherein light outputted from the respective cores on a second end face of the multi-core optical fiber is separated by guiding the outputted light through the light-receiving waveguide, the second end face opposing the first end face of the multi-core optical fiber.