Characterization of Long-Term Drift of LiNbO3 Intensity Modulators

The drift in the intensity versus applied voltage transfer function of lithium-niobate-based intensity modulators is an effect that can severely hinder the performance of telecommunication systems that rely on the device’s linear operation. Characterization of the most impactful effects associated to this drift allows for the proposal of a long-term stabilization technique based on analyzing the first and second harmonics of an applied monitoring tone. Results of the long-term drift of an off-the-shelf device are presented and the time-constant associated to its drift is analyzed; the parameter that translates the dependence of the drift’s magnitude on the applied bias voltage is shown to be in contrast of well-established models of the drift phenomenon. Nevertheless, the characteristics of the drift are still in accordance with a low-frequency monitoring tone solution, and the application of an FPGA-based Goertzel algorithm for identifying the operation region of the intensity modulator is put forward.