Single sideband optical modulator for lightwave systems

An optical transmitter comprising:

• a plurality of optical signal sources for generating optical signals comprising modulated optical carriers at different optical carrier frequencies, each of said optical signal sources comprising:
• a laser for generating an optical carrier,
• a single sideband optical phase modulator coupled to the output of said laser, and
• modulation means for providing first and second modulation signals to said single sideband modulator for modulating said optical carrier, said first and second modulation signals being selected such that an output optical signal from said single sideband modulator has only a single sideband;
• and
• means for coupling the output optical signal from each of said optical signal sources to an optical waveguide for transmission, each optical signal having only a single sideband so that said optical carrier frequencies can be closely spaced.

A single sideband optical intensity modulator comprising:

• a single sideband optical phase modulator having an input for receiving an optical carrier and an output for providing a modulated optical carrier;
• an optical waveguide section;
• an input polarization maintaining optical divider for coherently coupling an input optical carrier to said single sideband optical phase modulator and to an input of said polarization-maintaining optical waveguide section;
• an output polarization maintaining optical combiner for coherently combining the output of said single sideband optical phase modulator and the output of said optical waveguide section and providing an output optical signal;
• and
• modulation means for providing first and second modulation signals to said single sideband optical phase modulator, said first and second modulation signals being selected such that said modulated optical carrier has only a single sideband.

An optical communication system comprising:

• an optical transmitter comprising a plurality of optical signal sources for generating optical signals comprising modulated optical carriers at different optical carrier frequencies, each of said optical signal sources comprising:
• a laser for generating said optical carrier,
• a single sideband optical phase modulator coupled to the output of said laser, and
• modulation means for providing first and second modulation signals to said single sideband modulator for modulating said optical carrier, said first and second modulation signals being selected such that an output optical signal from said single sideband modulator has only a single sideband;
• a coherent optical receiver for receiving said optical signals;
• and
• an optical waveguide for coupling said optical signals from said optical transmitter to said coherent optical receiver, the outputs of said optical signal sources being coupled to said optical waveguide.

A single sideband optical phase modulator comprising:

• first and second optical waveguides;
• first and second electrodes positioned for phase modulating lightwaves carried in said first and second optical waveguides, respectively;
• polarization-maintaining optical divider for coherently coupling an optical carrier to said first and second optical waveguides;
• an polarization-maintaining optical combiner for coherently combining modulated optical carriers from said first and second optical waveguides and providing an output optical signal;
• and
• modulation means for providing a first modulation signal v.sub.s (t) to said first electrode and for providing a second modulation signal v.sub.c (t) to said second electrode, said first and second modulation signals being selected such that said output optical signal has only a single sideband.