Improving the operation of optoelectronic oscillator by stabilizing the electrooptic modulator

In an optoelectronic oscillator (OEO) system, it is crucial to keep the frequency as constant as possible. Electrooptic modulator (EOM) is a key component in this system having a big influence on OEO stabilization. The EOM is characterized by its voltage to optical output transfer function which unfortunately undergoes a drift during time leading to changes of the EOM characteristics and finally to a drift of the oscillation frequency. A twofold instrumentation system has been developed for controlling the EOM. Its first part is dedicated to the EOM temperature control. By using this part, the OEO frequency drift can be reduced by a factor 1.39 for one hour duration. The second part of the instrumentation system is used for compensating the drift of the EOM transfer function. With these two parts operating simultaneously, the frequency drift reduction can reach a factor up to 3.44 for one hour. These results demonstrate the efficiency of the compensation method.