Spatiotemporal Source Trajectory Tracking Using Multiplexed Optomechanical Fiber-Optic FPI Sensors

Low-frequency acoustic source tracking is essential for early fault diagnosis and structural health monitoring, yet conventional fiber-optic acoustic sensors that use circular diaphragms face fundamental trade-offs among radius, thickness, and material strength that limit sensitivity and robustness. This work proposes an optomechanical fiber-optic acoustic sensor employing an aluminum spiral-beams–supported diaphragm with a tunable resonant frequency, integrated into a Fabry–Pérot interferometer. Finite-element-guided design and experiments demonstrate a calibrated sensitivity of 6.127 V/Pa, a minimum detectable pressure of 51.23 µPa/ √Hz at 112 Hz, and a frequency response spanning 50 Hz to 20 kHz. To enable spatiotemporal tracking, we build a four-sensor array and develop a real-time adaptive strong-tracking unscented Kalman filter (AST-UKF) pipeline that enhances TDOA-based localization under low-SNR, reverberant conditions, reconstructing moving-source trajectories with 0.88 cm RMSE. The combination of low-frequency-optimized sensing and array-level inference yields a compact, passive, and electro-magnetic interference immune platform for weak-signal detection and trajectory tracking, providing practical support for online monitoring and decision-making in industrial environments.