A robust and dither-free technique for controlling driver signal amplitude for stable and arbitrary optical phase modulation.

We propose a robust and dither-free technique using a delay line interferometer, a balanced detector and simple signal processing to adjust the amplitude of the driver signal of an optical phase modulator automatically for stabilizing the modulated phase of an optical carrier at any arbitrary value. The technique is analytically shown to be robust against practical device imperfections. A stable 45 degrees phase shift with deviation less than ± 0.8 degrees is experimentally demonstrated.