Improving Opto-Electronic Oscillator stability by controlling the Electro-Optic Modulator

This paper presents a study concerning the improvement of the stability of an Opto-Electronic Oscillator (OEO). It seems to be the first publication about this subject. An advanced method for controlling the optical bias point of the Electro-Optic Modulator (EOM) has been developed. 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 implemented with PSoC microcontrollers is designed in order to keep the bias point at the quadrature position for minimizing the second order non-linear component. By this way the medium term stability can be greatly improved. Without bias point position control the OEO operates only for a few hours (2 or 3 h) but with the control it can operate for at least a working day (8 h).