Abstract: An optical oscillator uses a monochromatic light beam passing through a poelectric crystal subjected to acoustic vibrations which cause the emission of a diffracted light beam. The undiffracted beam is detected by photodetecting means and generates a first voltage signal. The diffracted beam is passed through a unit for delaying the passage of the beam, e.g. a fiber optics loop, and detected by photodetecting means to generate a second voltage signal. The signals are combined and fed to a control unit which allows a radio frequency signal to reach the piezoelectric crystal, causing acoustic vibrations. The time delay and voltage output relationships in the loop associated with the diffracted beam cause oscillation and control the frequency of such oscillations. The oscillations can be amplitude and frequency modulated by variation of appropriate circuit parameters.