Design approach and characterization of an integrated oscillator switched by an optical power are discussed. The oscillator is driven into oscillation at a frequency of 4.9 GHz under a light excitation power upper than a threshold value of 40 mW at a wavelength of 800 nm. On-off Keying modulation of the oscillator is performed with a digital optical power modulation allowing thus direct data transfer from optical to microwave carrier by photoconductivity. Illumination of the oscillator with optical pulses reveals the generation of short oscillations. The number of the generated signal periods depends on the optical power level and optical pulses width