A Differential Fiber-Optic FPI Acoustic Sensor for UAV Detection With CNN-LSTM

This study designs and fabricates a differential fiber-optic Fabry–P´erot interferometric (FPI) acoustic sensor for detecting small rotor UAVs. By placing two optical fibers with a 45° inclination parallel on both sides of a polyethylene terephthalate (PET) diaphragm surface, a differential F-P cavity structure is formed. Results indicate that this differential configuration enhances the signal-to-noise ratio.We employ Mel-frequency cepstral coefficients (MFCC) as acoustic features and construct a CNN-LSTM model for binary classification in UAV detection. Signals from a DJI Mini3 UAV at a distance of 200 meters are collected using the fabricated sensor for recognition. The results demonstrate that after adopting the differential structure, the detection accuracy for UAVs reaches 99.24%, surpassing the 96.97% achieved without the differential structure, thereby validating the effectiveness of the differential design in enhancing the detection capability for weak UAV signals. This study provides a novel and effective solution for long-distance acoustic monitoring of UAV signals.