Patent ID: 9494810
Filing Date: 2016-11-15
CPC Classification: G01J,G02F,H04B

Claim Text:
1. A method of automatic bias stabilization, the method comprising: simultaneously dithering DC-bias voltage of each of an X polarization in-phase child Mach-Zehnder modulator (MZM), an X polarization quadrature-phase child MZM, and an X polarization parent MZM included in an X polarization arm of a dual-polarization in-phase and quadrature optical modulator (IQM) according to three first dither patterns that are different from each other; detecting, at a first tap monitor photodiode coupled to an output of the X polarization arm, an X polarization interference term between the three first dither patterns; sampling an output of the first tap monitor photodiode to generate an X polarization interference signal indicative of the X polarization interference term; calculating an in-phase child MZM error signal, based on the interference signal between a quadrature-phase child MZM error signal and an X polarization parent MZM error signal; updating an in-phase child MZM DC-bias set point to minimize the in-phase child MZM error signal; calculating the quadrature-phase child MZM error signal, based on the interference signal between the in-phase child MZM error signal and the X polarization parent MZM error signal; updating a quadrature-phase child MZM DC-bias set point to minimize the quadrature-phase child MZ error signal; calculating the X polarization parent MZM error signal, based on the interference signal between the in-phase child MZM error signal and the quadrature-phase child MZM error signal; and updating a parent MZM DC-bias set point to minimize the X polarization parent MZM error signal.