A Feedback Control Loop for Frequency Stabilization in an Opto-Electronic Oscillator

A new method for the long-term frequency stabilization of an opto-electronic oscillator (OEO) is proposed. All existing methods are based on the precise temperature stabilization of specific components of an OEO, for example, the optical fiber and the microwave band-pass filter. We propose a new method based on a feedback control loop that detects the oscillator frequency using a frequency discriminator and modifies the laser wavelength to keep the oscillator frequency constant using the fiber chromatic dispersion. With the proposed method we achieved a frequency-temperature coefficient of 0.2 ppm/K. Unlike previous methods, our method also compensates the effects of other unstabilized OEO components on the OEO´s frequency. Other benefits are that there is no need for an accurate temperature stabilization of the optical fiber and mode hopping is prevented.