Wavelength multiplexing/demultiplexing unit, wavelength multiplexing/demultiplexing apparatus and wavelength multiplexing/demultiplexing method

An optical multiplexing/demultiplexing unit comprising:

• a first waveguide for receiving a wavelength multiplexed optical wave;
• first filter means optically connected with the first waveguide for separating the wavelength multiplexed optical wave from the first waveguide into a first optical wave in a first wavelength band and a second optical wave in a second wavelength band;
• second filter means optically connected with the first filter means for separating the first optical wave in the first wavelength band from said first filter means into a third optical wave in a third wavelength band and a fourth optical wave in a fourth wavelength band;
• means for optical-demultiplexing the third optical wave in the third wavelength band from said second filter means into optical waves each of a single wavelength;
• a second waveguide for outputting the second optical wave in the second wavelength band from said first filter means to a succeeding optical means;
• and
• a third waveguide for outputting the fourth optical wave in the fourth wavelength band from said second filter means to a succeeding optical means.

An optical multiplexing/demultiplexing unit comprising:

• a substrate;
• a first cladding layer stacked on said substrate;
• a core layer stacked on said first cladding layer;
• a second cladding layer stacked on said core layer;
• and
• said core layer including:
• a first waveguide for receiving a wavelength multiplexed optical wave;
• filter means optically connected with said first waveguide for separating the wavelength multiplexed optical wave from said first waveguide into a first optical wave in a first wavelength band and a second optical wave in a second wavelength band;
• means for optical-demultiplexing the first optical wave in the first wavelength band into optical waves each of a single wavelength;
• and
• a second waveguide for directing the second optical wave in the second wavelength band to a succeeding optical means.

An optical multiplexing/de multiplexing apparatus in which a plurality of optical multiplexing/demultiplexing units which are different from one another in operating wavelength band are connected hierarchically, each of said optical multiplexing/de multiplexing units comprising:

• a first waveguide for receiving a wavelength multiplexed optical wave;
• filter means optically connected with the first waveguide for separating the wavelength multiplexed optical wave from the first waveguide into a first optical wave having the corresponding operating wavelength band and a second optical wave having the other wavelength bands;
• means for optical-demultiplexing the first optical wave from said filter means into optical waves each of a single wavelength;
• and
• a second waveguide for directing the second optical wave from said filter means to a first waveguide of a succeeding optical multiplexing/demultiplexing unit.

A method of demultiplexing an incident wavelength multiplexed optical wave into different wavelength bands comprising:

• a first step of separating the wavelength multiplexed optical wave into a first optical wave in a first wavelength band and a second optical wave in a second wavelength band by a first filter means, and then outputting the first optical wave to succeeding optical means and the second optical wave to a second filter means;
• a second step of separating the first optical wave from said first filter means into a third optical wave in a third wavelength band and a fourth optical wave in a fourth wavelength band by a second filter means, and then outputting the third optical wave to multiplexing/demultiplexing means and the fourth optical wave to succeeding optical means;
• and
• a third step of optical-demultiplexing the third optical wave into optical waves each of a single wavelength from said multiplexing/demultiplexing means.