Patent ID: 7324760
Filing Date: 2008-01-29
Classification: H04B

Abstract:
1. An optical return-to-zero transmitter comprising: means for providing a pulsed optical signal; an optical modulator arranged to receive a non-return-to-zero electrical data signal and a bias signal, to modulate said optical signal with said data signal; whereby said optical signal providing means and said modulator provide a return-to-zero optical output signal modulated with said data signal; means for controlling the difference in phase between said pulsed optical signal and said data signal in response to a phase control signal; means for adding a first dither signal to said difference in phase and a second dither signal, having a different frequency than said first dither signal, to said bias signal; means for monitoring the amplitude of variations in the power of the optical output signal corresponding to cross-modulation of said first and second dither signal frequencies; and means responsive to said monitored amplitude for adjusting said phase control signal to maintain phase synchronization between said pulsed optical signal and said data signal.