Flexible Optical Fiber Fabry–Perot Interferometer Based Acoustic and Mechanical Vibration Sensor

We have proposed and demonstrated a novel flexible optical fiber Fabry-Perot interferometer (FPI) based vibration sensor with broadband frequency response. The sensor consists of a flexible FP cavity formed by soft splicing using polydimethylsiloxane (PDMS) material with low Young's Modulus and a compact fiber cantilever of low moment inertia as the vibration receiver. Acoustic or mechanical waves experienced by the fiber cantilever can result in obvious change of the FPI cavity length and finally be transduced to the intensity variation of the sensor signal, which makes the sensor highly sensitive to external acoustic or mechanical vibrations. Taking advantage of the superior elasticity of PDMS and compact structure of cantilever, a broadband frequency response for vibration detection has been achieved together with high sensitivity without extra external vibration receiver. The vibration detection is theoretically analyzed, and acoustic vibrations up to 20 kHz and damped mechanical vibrations from tens of hertz to tens of kilohertz, covering both the sound and part of ultrasound range, have been experimentally detected. Moreover, each event of the ball hitting and rebounding has been accurately identified by our sensor, showing excellent vibration sensing only by a thin optical fiber. We believe such a broadband, compact and cost-effective sensor would be a promising candidate for monitoring both acoustic and mechanical vibrations.