Passband flattening of integrated optical filters

An wavelength dispersive device, comprising:

• a first side comprising at least one substantially single-moded optical waveguide;
• a second side comprising a plurality of substantially single-moded optical waveguides;
• a frequency dispersive element optically coupling said waveguides between said first and second sides across at least one optical interaction region;
• and
• a multi-moded waveguide disposed on an end of at least one of said waveguides adjacent to said interaction region.

An arrayed waveguide device, comprising:

• a first and a second optical interaction region;
• at least one first single-moded optical waveguide optically coupled to a first side of said first optical interaction region;
• a plurality of optical waveguides optically coupled between a second side of said first optical interaction region and a first side of said second optical interaction region and having respective phase lengths with predetermined differences therebetween;
• at least one second single-moded optical waveguide optically coupled to a second side of said second optical interaction region;
• and
• a multi-moded waveguide interposed between at least one of said first and second optical waveguides and a neighboring one of said first and second optical interaction regions.

An optical filter, comprising:

• at least one single-moded input waveguide;
• at least one single-moded output waveguide;
• at least one optical interaction region and a frequency dispersive element operatively connected thereto, receiving at least one optical input signal on said at least one input waveguide, and dividing said at least one input signal according to wavelength into said at least one output waveguide;
• at least one multi-mode interference filter disposed between one of said waveguides and said at least optical interaction region.

A drop-add circuit, comprising:

• a single-mode input waveguide;
• a first multi-mode waveguide receiving signals from said input waveguide;
• a second mult-mode waveguide;
• a single-mode output waveguide receiving signals from said second multi-mode waveguide;
• a plurality of feedback waveguides;
• at least one optical interaction region receiving signals on a first side from said first multi-mode waveguide and first ends of said feedback waveguides and sending signals on a second side to said second multi-mode waveguide and second ends of said feedback waveguides;
• a frequency dispersive element operatively disposed in said at least one optical interaction region;
• and
• at least one interexchange element disposed on a respective one of said feedback waveguides, selectively interchanging an optical signal carried on said respective feedback waveguide for another optical signal.

An optical switch comprising:

• a first and a second wavelength dispersive system, each comprising:
• at least one optical interaction region having a first side receiving an input signal on a substantially single-moded input waveguide and a second side from which an output signal is transmitted on a substantially single-moded output waveguide,
• a waveguide dispersive element operatively associated with said at last one optical interaction region, and
• a plurality of feedback waveguides linking said first and second sides;
• and
• selective interexchange elements connected between pairs of said feedback waveguides of said first and second waveguide dispersive systems, and
• wherein said input and output waveguides are single-moded and multi-mode interference filters are interposed between said at least one optical interaction regions and at least some of said input and output waveguides in each of said waveguide dispersive systems.

An optical switch comprising:

• at least one optical interaction region receiving two input signals on a receiving side thereof and sending two output signals from a sending side thereof;
• a wavelength dispersive element associated with said at least one optical interaction region;
• plural feedback channels linking different respective positions on said sending side with corresponding positions on said receiving side;
• selectively activable connections between said feedback channels;
• and
• at least two multi-mode interference filters on at least one side of said at least one optical interaction region carrying respective ones of said input and output signals.

An optical switch comprising:

• at least one optical interaction region receiving two input signals on a receiving side thereof and sending two output signals from a sending side thereof;
• a wavelength dispersive element associated with said at least one optical interaction region;
• plural feedback channels linking different respective positions on said sending side with corresponding positions on said receiving side;
• selectively activable connections between said feedback channels;
• respective substantially single-moded waveguides carrying said input and said output signals;
• and
• at last one multi-moded waveguide disposed between said single-moded waveguides and said at least one optical interaction region.

A multi-wavelength laser source, comprising formed on a chip:

• a plurality of semiconductor lasers emitting at a plurality of respective wavelengths;
• a plurality of single-moded first waveguides receiving respective outputs of said semiconductor lasers;
• at least one optical interaction region receiving said single-moded first waveguides;
• a wavelength dispersive element coupled to said at least one optical interaction region;
• a single-moded second waveguide receiving an output of said at least one optical interaction region;
• and
• at least one multi-moded waveguide coupled between one of said waveguides and said at least one optical interaction region.

A 2.times.2 optical switch for switching signals between either a first or a second single-moded input optical waveguiding means and a first or a second single-moded output optical waveguiding means, said switch comprising

• a first and a second demultiplexer and a first and a second multiplexer,
• a plurality of multiple-mode interference couplers individually connecting said first and second input optical waveguiding means to said first and second demultiplexers and said first and second multiplexers to said first and second output waveguiding means, respectively,
• a plurality of first single-mode waveguides connecting said first demultiplexer to said first multiplexer,
• a plurality of second single-mode waveguides means connecting said second demultiplexer to said second multiplexer,
• crossing waveguides between said first and second waveguiding means, and
• routing switch means for connecting said crossing waveguides to said first and second waveguides.

A 2.times.2 optical switch for switching signals between either a first or a second single-moded input optical waveguiding means and a first or second single-moded output optical waveguiding means, said switch comprising

• first optical interaction means for each of said input waveguiding means,
• second optical interaction means for each of said output waveguiding means,
• a first and a second plurality of grating waveguides inter-connecting said first and second interaction means,
• a plurality of multiple-mode interference couplers individually connecting each of said interactions means to its waveguiding means,
• a first and a second plurality of feedback waveguides inter-connected between said first and second interaction means, and
• routing switch means for interconnecting individual ones of said feedback waveguides of said first and second pluralities.

A 2.times.2 optical switch for switching signals between either a first or a second single moded input optical waveguiding means and a first or a second single-moded output optical waveguiding means said switch comprising

• a first and a second interaction region,
• multiple-mode interference couplers connecting said first interaction region individually to the first and second single-moded input waveguiding means and connecting said second interaction region individually to the first and second single-moded output waveguiding means,
• grating waveguides connecting said first and second interaction regions,
• feedback waveguides connecting said first and second interaction regions, and
• optical cross-connects connecting individual pairs of said feedback waveguides.

A 2.times.2 optical switch for switching signals between either a first or a second single-moded input optical waveguiding means and a first or a second single-moded output optical waveguiding means, said switch comprising,

• first means defining a first path between the first input waveguiding means and the first output waveguiding means and including a first plurality of single-mode wave guides,
• second means defining a second path between the second input waveguiding means and the second output waveguiding means and including a second plurality of single-mode wave guides,
• each of said first and second means including a pair of multiple mode interference couplers, a demultiplexer and a multiplexer, and
• means for selectively interconnecting individual ones of said first and second pluralities of single-mode waveguides.

A 2.times.2 optical switch for switching signals between either a first or a second single-moded input optical waveguiding means and a first or a second single-moded output optical waveguiding means, said switch comprising

• first means defining a first path between the first input waveguiding means and the first output waveguiding means and including a first plurality of single-mode wave guides,
• second means defining a second path between the second input waveguiding means and the second output waveguiding means and including a second plurality of single mode wave guides,
• each of said first and second means including a pair of multiple mode interference couplers and a first and a second optical interactions means, and
• means for selectively interconnecting individual ones of said first and second pluralities of single-mode waveguides.

A wavelength-division laser transmitter comprising a

• plurality of semiconductor lasers in an array and each designed to emit at its respective and predetermined wavelength,
• a multiplexer,
• individual single-mode waveguides connecting each of said lasers to said multiplexer,
• a single-mode output waveguide, and
• a multi-mode interference coupler connecting said multiplexer to said output waveguide.