A metal diaphragm-based omnidirectional fiber-optic acoustic sensor with high sensitivity has been developed in this work. The acousto-optic transducer of the sensor is a single-wavelength extrinsic Fabry–Pérot interferometer (EFPI) that is highly sensitive to the displacement of the diaphragm’s center. The sensor can stably work in the linear response region of the EFPI in a wide range of temperature from −20 to 60 °C. The pressure sensitivity of the sensor is larger than 800 mV/Pa, and the sensitivity fluctuation in the frequency range from 100 Hz to 6 kHz is smaller than 3 dB. The noise-limited minimum detectable pressure obtained at 1 kHz of the sensor is 126 μPa/Hz1/2. In addition, the above-prepared fiber-optic acoustic sensors present excellent phase consistency with each other, which facilitates the formation of a sensor array for sound source localization. In this work, a cross-shaped fiber-optic sensor array was prepared and then used to detect and track a small drone flying in the field. The experimental results show that the sensor array can capture the acoustic fingerprint of the drone at a distance as far as 300 m. This detection distance is more than ten times longer than that of a conventional electret condenser microphone. The azimuth angle of the drone obtained with the fiber-optic acoustic sensor array has a deviation of smaller than 10° relative to the GPS data from the drone.

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