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.
