Optical multiplexer/demultiplexer

An optical multiplexer/demultiplexer comprising:

• a substrate;
• first and second slab waveguides provided on said substrate, each having a predetermined slab length:
• at least one input waveguide provided on said substrate, said input waveguide having an optical output end connected to an optical input end face of said first slab waveguide;
• a plurality of output waveguides flatly arrayed on said substrate in a state in which optical input ends of said output waveguides are connected to an optical output end face of said second slab waveguide, said output waveguides provided corresponding to respective signals of channel wavelengths set as signal channels at predetermined wavelength intervals;
• and
• a plurality of channel waveguides flatly arrayed on said substrate in a state in which optical input ends of said channel waveguides are connected to an optical output end face of the first slab waveguide so as to place said first slab waveguide between said channel waveguides and said input waveguide and in which optical output ends of said channel waveguides are connected to an optical input end face functioning as a lens surface of said second slab waveguide so as to place said second slab waveguide between said channel waveguides and said output waveguides, said channel waveguides having mutually different lengths,
• wherein an optical input end of at least either one of said output waveguides is located at a position apart from the optical input end face of said second slab waveguide by a distance shorter than a focal length of the optical input end face of said second slab waveguide.