Bias control in an optical modulator and transmitter

A method for controlling an optical modulator, comprising:

• (a) applying a first optical signal, a first bias signal, and a first RF modulating signal to the optical modulator and measuring a performance parameter thereof, wherein a magnitude of the first bias signal is selected so as to obtain a pre-determined value of the measured performance parameter;
• (b) while applying the first optical signal, the first RF modulating signal, and the first bias signal of the magnitude selected in step (a) to the optical modulator, applying a dither signal to the optical modulator and measuring a target peak-to-peak optical power variation of the first optical signal due to the dither signal application;
• (c) storing a magnitude of the first bias signal and the measured target peak-to-peak optical power variation in a memory;
• (d) upon completion of steps (a) to (c), applying a second optical signal, a second RF modulating signal, a second bias signal, and the dither signal to the optical modulator, and measuring an operational peak-to-peak optical power variation of the second optical signal due to the dither signal application;
• and
• (e) adjusting the second bias signal, so as to lessen a difference between the operational peak-to-peak optical power variation measured in step (d) and the target peak-to-peak optical power variation stored in step (c), thereby obtaining the pre-determined value of the performance parameter without having to re-measure the performance parameter,
• wherein steps (a) to (c) are performed during calibration of the optical modulator, and steps (d) and (e) are performed during subsequent operation of the optical modulator.