Optical wavelength multiplexer/demultiplexer and use method thereof

An optical wavelength multiplexer/demultiplexer comprising:

• an optical multiplexing/demultiplexing circuit that includes a Mach-Zehnder optical interferometer, said Mach-Zehnder optical interferometer being at least one stage and having a final stage, and including
• a first optical waveguide,
• a second optical waveguide arranged side-by-side with respect to said first optical waveguide, and
• a plurality of multi-mode optical interference waveguides respectively formed where a portion of said first optical waveguide is located adjacent to and in proximity to a portion of said second optical waveguide for a predetermined interval along a longitudinal direction of both said first and second optical waveguides,
• respective segments of the first optical waveguide and the second optical waveguide that are sandwiched between adjacent multi-mode optical interference waveguides having different lengths, the final stage having
• at least two optical output waveguides, and
• optical transmission filters provided in respective of the at least two optical output waveguides, said optical transmission filters being configured to transmit therethrough light having setting wavelengths determined in correspondence with wavelengths passed by the respective optical output waveguides.

An optical wavelength multiplexer/demultiplexer comprising:

• an optical multiplexing/demultiplexing circuit that includes a Mach-Zehnder optical interferometer, said Mach-Zehnder optical interferometer being at least one stage and having a final stage, and including
• a first optical waveguide,
• a second optical waveguide arranged side-by-side with respect to said first optical waveguide,
• a multi-mode optical interference waveguide, and
• a directional coupling portion formed where a portion of said first optical waveguide is located adjacent to and in proximity to a portion of said second optical waveguide for a predetermined interval along a longitudinal direction of both said first and second optical waveguides,
• respective segments of the first optical waveguide and the second optical waveguide being sandwiched between the directional coupling portion and the multi-mode optical interference waveguide having different lengths,
• the final stage having
• at least two optical output waveguides, and
• optical transmission filters provided in respective of the at least two optical output waveguides, said optical transmission filters being configured to transmit therethrough light having setting wavelengths determined in correspondence with wavelengths passed by the respective optical output waveguides.

An optical wavelength multiplexer/demultiplexer comprising:

• an optical multiplexing/demultiplexing circuit that includes a Mach-Zehnder optical interferometer, said Mach-Zehnder optical interferometer being at least one stage and having a final stage, and including
• a first optical waveguide,
• a second optical waveguide arranged side-by-side with respect to said first optical waveguide, and
• a plurality of a multi-mode optical interference waveguides,
• respective segments of the first optical waveguide and the second optical waveguide being sandwiched between adjacent multi-mode optical interference waveguides having different lengths, the final stage having
• at least two optical output waveguides, and
• optical transmission filters provided in respective of the at least two optical output waveguides, said optical transmission filters being configured to transmit therethrough light having setting wavelengths determined in correspondence with wavelengths passed by the respective optical output waveguides.

A method for using an optical wavelength multiplexer/demultiplexer having a Mach-Zehnder optical interferometer, comprising steps of:

• passing a first light signal at a first wavelength and a second light signal at a second wavelength through a first optical waveguide;
• coupling a portion of the second light signal into a second optical waveguide arranged side-by-side with respect to said first optical waveguide, said coupling step including
• passing the second light signal through a plurality of directional coupling portions respectively formed where a portion of said first optical waveguide is located adjacent to and in proximity to a portion of said second optical waveguide for a predetermined interval along a longitudinal direction of both said first and second optical waveguides,
• respective segments of the first optical waveguide and the second optical waveguide that are sandwiched between adjacent directional coupling portions having different lengths, and
• filtering with a filter disposed in a final stage of the Mach-Zehnder optical interferometer the second signal light that is output from the first optical waveguide prior to passing said first light signal to an optical output waveguide;
• and
• filtering with another filter disposed in the final stage of the Mach-Zehnder optical interferometer the first signal light that is output from the second optical waveguide prior to passing said second light signal to another optical output waveguide, so as to demultiplex the first optical signal and the second optical signal.

A method for using an optical wavelength multiplexer/demultiplexer having a Mach-Zehnder optical interferometer, with a final stage, comprising steps of:

• inputting a first optical signal at a first wavelength to an optical output waveguide disposed in the final stage;
• inputting a second optical signal at a first wavelength to another optical output waveguide disposed in the final stage;
• filtering the first optical signal and the second optical signal with an optical transmission filter provided in the respective optical output waveguides, said optical transmission filter being configured to transmit therethrough light having respective wavelengths determined in correspondence with the respective optical output waveguides;
• coupling at least a portion of the second light signal into a first optical waveguide, said coupling step including
• passing the second light signal through a plurality of directional coupling portions respectively formed where a portion of said first optical waveguide is located adjacent to and in proximity to a portion of a second optical waveguide for a predetermined interval along a longitudinal direction of both said first and second optical waveguides,
• respective segments of the first optical waveguide and the second optical waveguide that are sandwiched between adjacent directional coupling portions having different lengths, and
• outputting the first light signal and the second light signal as a multiplexed signal through the first optical waveguide.

An optical wavelength multiplexer/demultiplexer comprising:

• an optical multiplexing/demultiplexing circuit that includes a Mach-Zehnder optical interferometer, said Mach-Zehnder optical interferometer being at least one stage and having a final stage, and including
• a first optical waveguide,
• a second optical waveguide arranged side-by-side with respect to said first optical waveguide, and
• a plurality of directional coupling portions respectively formed where a portion of said first optical waveguide is located adjacent to and in proximity to a portion of said second optical waveguide for a predetermined interval along a longitudinal direction of both said first and second optical waveguides,
• respective segments of the first optical waveguide and the second optical waveguide that are sandwiched between adjacent directional coupling portions having different lengths, the final stage having
• at least two optical output waveguides, and
• gratings provided in respective of the at least two optical output waveguides, said fiber gratings being configured to transmit therethrough light having setting wavelengths determined in correspondence with wavelengths passed by the respective optical output waveguides.