US Patent 6885823 Wavelength multiplexing/demultiplexing unit, wavelength multiplexing/demultiplexing apparatus and wavelength multiplexing/demultiplexing method

An optical multiplexing/demultiplexing apparatus in which a plurality of optical multiplexing/demultiplexing units operating in different wavelength bands are connected hierarchically. Each of the plurality of optical multiplexing/demultiplexing units includes an input waveguide for receiving wavelength multiplexed optical waves, a filter for separating the wavelength multiplexed optical wave from the input waveguide into a first optical wave in a corresponding operating wavelength band and a second optical wave in the other wavelength bands. Each of the multiplexing/demultiplexing units also includes an AWG optical multiplexer/demultiplexer for separating the first optical wave from the filter into individual optical waves each of a single wavelength, and a branch waveguide for directing the second optical waves from the filter to an input waveguide of a succeeding optical multiplexing/demultiplexing unit.