An interrogation system for fiber optic interferometric sensors is presented. The system consists of a digital signal processor, a codec, laser bias and modulation control circuits, an optical receiver and customized software. The system transmits a modulated light signal to the sensing interferometer, demodulates the returning interferometric signal using synthetic-heterodyne detection, while simultaneously relaying control and signal data via PC based software. The system was tested using a low-finesse Fabry-Perot cavity, consisting of a cleaved fiber end and a mirror mounted on a piezoelectric cylinder. The mirror was vibrated using a sinusoidal voltage applied to the piezoelectric cylinder. Using the interrogation systems, successful retrieval of the vibration signal was obtained for vibrating frequencies from 44 Hz to 4.41 kHz.
