All-Fiber Acoustic Sensor Based on Anti-Resonant Reflective Optical Waveguide

This article proposed and experimentally demonstrated a high-sensitivity all-fiber and diaphragm-free acoustic sensor based on the hollow-core fiber (HCF) anti-resonant reflecting optical waveguide (ARROW). The sensor takes advantage of the self-imaging and collimated and beam expansion properties of gradient-index multimode fiber (GIMF) to precisely control the optical mode field coupled into the HCF to improve the spectral contrast. Acoustic sensing is achieved through the shift of transmission spectrum characteristic wavelength caused by acoustic interaction and combined with the anti-resonance reflection effect in the HCF to improve sensitivity. Using the quadrature point ( $Q$ -point) intensity demodulation, we can know that the frequency response of the sensor is in the range of 100 Hz–14.2 kHz. When the frequencies are 290 Hz, 5.6 kHz, and 9.2 kHz, the acoustic pressure sensitivities are 1.189, 0.165, and 0.392 V/Pa, respectively. This sensor is diaphragm-free structure, and the performance is not affected by factors, such as diaphragm material, and has good acoustic pressure response and repeatability. In addition, it is compact, high sensitivity, and potential to resist high static pressure, which has good application prospects.