Detection of high- and low-frequency vibrations using a feedback- stabilized differential fiber optic interferometer

Highly sensitive and stable detection of minute ac and pseudo-dc (i.e. , very low frequency) vibrations is performed by means of a differential fiber optic Michelson interferometer. Any residual instabilities are eliminated by means of an ac feedback control loop. The stabilization technique is not affected by the variations in the reflectivity of the sample and by launch inefficiencies into the fiber. This approach also provides a simple, quantitative method for calibrating sample vibrations. Results are presented on the operation of the system in stabilizing its output as well as on the detection of the vibration of a silicon sample.