Electro-optic modulator drift compensation based on DSP system

This paper presents a study concerning the improvement of an electro-optic modulator operation by controlling its optical bias point. The evolution of the modulator characteristics can be followed through its non-linear behavior by detecting the second harmonic of a low-frequency modulating signal. The control system has been implemented in a kit based on a DSP board and a data acquisition card; it is designed in order to keep the bias point at the optimal value for minimizing the second order non-linear effects. So it is possible to compensate completely the effects of the modulator transfer function drift for more than 8 hours.