Method and apparatus for transmitting a modulated optical signal

A method of transmitting a modulated optical signal comprising:

• modulating a continuous optical signal in response to a radio frequency (RF) driving signal and a DC bias signal to produce an optical pulse stream;
• modulating the optical pulse stream with a data signal to produce the modulated optical signal;
• dithering the phase of the RF driving signal with a first dither signal;
• and
• dithering the level of the DC bias signal with a second dither signal.

An apparatus for transmitting a modulated optical signal comprising:

• a first Mach-Zehnder modulator, for receiving a optical signal and being responsive to a radio frequency (RF) driving signal and a DC bias signal to produce therefrom an optical pulse stream;
• a second Mach-Zehner modulator, for modulating the optical pulse stream with a data signal to produce the modulated optical signal;
• and
• a digital signal processor, for dithering the phase of the RF driving signal with a first dither signal and dithering the level of the DC bias signal with a second dither signal;
• wherein the digital signal processor phase aligns the optical pulse stream with respect to the data signal by adjusting the phase of the RF driving signal to substantially null the first dither signal after the first dither signal is detected in the modulated optical signal, and the processor biases the first modulator by adjusting the level of the DC bias signal to substantially null the second dither signal after the second dither signal is detected in the modulated optical signal.