Optical add/drop multiplexer device

An optical add/drop multiplexer device, comprising:

• a substrate member;
• a plurality of optical waveguides, formed over the substrate member in layers with a prescribed interval along a direction perpendicular to a plane of the substrate member, each optical waveguide having a portion arranged in parallel and in proximity to an adjacent optical waveguide to form a coupling section;
• and
• a diffraction grating member, provided at the coupling section and having a prescribed period along a light propagation direction, for reflecting light signals with a specific wavelength among light signals entered from one of adjacent optical waveguides to another one of the adjacent optical waveguides, the diffraction grating member having a reflectivity which is variable according to at least one of parameters including a length of a region in the light propagation direction for which the diffraction grating member is provided at the coupling section, a depth of the diffraction grating member with respect to the adjacent optical waveguides at the coupling section, and a distance between the adjacent optical waveguides at the coupling section.