A Compact, Low-Cost, Highly Sensitive and High Speed Fiber Optic Vibration Sensor Based on Liquid Mass Block

Currently, for fiber optic vibration sensors (FOVS), realizing high sensitivity (sub-μg) and high speed (~ kHz) simultaneously is still a challenge. Herein, a high speed and highly sensitive FOVS was demonstrated by using the liquid mass block (silicone oil), which can transmit the inertial force to all the direction inside the FOVS for omnidirectional sensing. Owing to the liquid nature of oil, the inertial force can be uniformly applied on the diaphragm without deteriorating its mechanical properties. The response magnitude of FOVS can be enhanced ~48 dB by employing the liquid mass block. Moreover, because without using any optical interference effect, precise control on the light wavelength and cavity length is no longer needed, which simplifies sensor fabrication and demodulation system for compact and low cost. An omnidirectional detection limit of 0.1 μg, a sensitivity of 3.2 V/g, and a resonance frequency of 2.7 kHz was realized for the FOVS.