Synchronous polarization and phase modulation using a periodic waveform with complex harmonics for improved performance of optical transmission systems

An apparatus, comprising:

• an optical signal source for generating an optical signal onto which data is modulated at a predetermined frequency;
• a phase modulator coupled to said optical signal source for modulating the phase of said optical signal;
• a periodic waveform generator coupled to said phase modulator for generating a periodic control signal for controlling the modulation cycle of said phase modulator;
• and
• a clock coupled to said phase modulator having a frequency that determines the periodicity of said control signal, wherein said clock frequency is equal to said predetermined frequency,
• wherein said control signal is a function of time f(t) described by f(t)=sin (t)+0.4*sin (2t)+0.2*sin (4t).

An apparatus, comprising:

• an optical signal source for generating an optical signal onto which data is modulated at a predetermined frequency;
• a phase modulator coupled to said optical signal source for modulating the phase of said optical signal;
• a periodic waveform generator coupled to said phase modulator for generating a periodic control signal for controlling the modulation cycle of said phase modulator;
• and
• a clock coupled to said phase modulator having a frequency that determines the periodicity of said control signal, wherein said clock frequency is equal to said predetermined frequency,
• wherein said control signal is a periodic signal having a fundamental frequency and at least one higher harmonic frequency.

A method for modulating an optical signal comprising the steps of:

• receiving an optical signal onto which data has been modulated at a predetermined frequency;
• and
• phase modulating said received optical signal with a periodic waveform at said predetermined frequency
• wherein said periodic waveform includes a fundamental frequency substantially equal to said predetermined frequency and at least one higher harmonic frequency.

An apparatus, comprising:

• a polarization modulator adapted to receive an optical signal that is modulated with data at a predetermined frequency and for modulating the state of polarization of the optical signal by tracing the polarization of said optical signal along at least a portion of a Poincaré sphere such that an average value of the state of polarization over a modulation cycle is substantially equal to zero;
• a phase modulator coupled to said polarization modulator for modulating the phase of said optical signal;
• and
• a first periodic waveform generator coupled to said phase modulator for generating a first periodic control signal for controlling the modulation cycle of said phase modulator where said first periodic control signal includes a fundamental frequency substantially equal to said predetermined frequency and at least one higher harmonic frequency.