Sensitivity improvement of submicron dynamic displacement measurement system composed of phase-modulated fiber optic interferometer

Abstract

Abstract We investigated sensitivity improvement of a dynamic displacement measurement system composed of a phase-modulated fiber optic interferometer and a spatial optical system. We introduced a balanced photodetector to enhance the signal-to-noise ratio of the interference signal. The newly developed system was evaluated by using pseudo vibration made by a phase modulator and was proved to be able to measure the dynamic displacement with a high-frequency vibration of 100 kHz even when the reflected optical power from a sample was −50 dBm. We also performed experiments using a rubber or a mouse’s ear bone attached to a piezoelectric element driven by a 100 kHz sinusoidal signal and successfully confirmed that vibration with an amplitude of less than 10 nm was clearly observed even when a reflected optical power was –46.9 dBm.