Optically controlled fast switching of a microstrip resonator has been investigated. Theoretical model of the resonator including losses in the photoconductive semiconductor switch was considered. An additional microstrip line coupled with one of the arms of the resonator was employed to detect the oscillations appearing in the resonator. Up to 6 periods of damped oscillations at a frequency 2.1 GHz have been observed experimentally in the coupled microstrip line using optically controlled microstrip resonator with GaAs switch.