Enhanced Quasi-Distributed Accelerometer Array Based on φ-OTDR and Ultraweak Fiber Bragg Grating

We propose and experimentally demonstrate an enhanced quasi-distributed accelerometer array based on phase-sensitive optical time-domain reflectometry (
$\phi $
-OTDR) and ultraweak fiber Bragg grating (UWFBG). By utilizing a transducer cylinder, the vibration can be easily converted to an axial strain of the sensing fiber, which enables a high sensitivity in vibration measurement. Furthermore, a UWFBG array that contains backscattering enhanced points along the fiber is employed to improve the signal-to-noise ratio (SNR). Consequently, quasi-distributed vibration sensing with a resolution of 0.03 g and a flat sensitivity of 1.4 rad/g in a frequency range from 50 to 800 Hz is realized over 500-m long UWFBG. The proposed sensing system offers high-sensing sensitivity, large multiplexing capacity, and anti-interference fading, which can be applied for structural health monitoring of large buildings and machinery.