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

摘要

A method and apparatus is provided that yields improved performance by modulating the optical phase and polarization of an optical signal with a periodic waveform having harmonic content that is more complex than that associated with a simple sinusoidal waveform. A phase modulator receives an optical signal onto which data has been modulated at a predetermined frequency. The phase modulator modulates the phase of the optical signal in a continuous manner with the periodic waveform with complex harmonics where the fundamental phase modulation frequency is equal to the same predetermined frequency at which the data is modulated onto the optical signal. In another illustrative embodiment of the invention, a polarization modulator further processes the optical signal by modulating the state-of-polarization of the signal in a continuous fashion with the periodic waveform with complex harmonics where the fundamental polarization modulation frequency is equal to the same predetermined frequency at which the data is modulated onto the optical signal. In addition to being continuously modulated, the polarization modulation is performed so that the average value of the state of polarization over each modulation cycle is substantially equal to zero.