High-sensitivity measurement of low-frequency vibration signals based on an optoelectronic oscillator with an intra-loop Michelson interferometer.

A high-sensitivity demodulation method for the vibration-induced frequency shift of an optoelectronic oscillator (OEO) using an acousto-optic modulator (AOM) has been proposed and experimentally demonstrated. This is achieved by separating the optical carrier (OC) and the first-order sideband, directing them into the reference and sensing arms of a Michelson interferometer (MI), respectively. Additionally, since the system sensitivity depends on the optical frequency rather than the oscillating frequency, high-sensitivity vibration sensing can be achieved at OEO oscillating frequencies as low as 80 MHz. Experimental results indicate that for low-frequency vibration signals in the range of 200-800 Hz, the system achieves a vibration amplitude sensitivity of up to 1.77 GHz/cm and a minimum detectable vibration amplitude of 5.1 pm, representing the best result within our current knowledge for low-frequency vibration demodulation using OEO.