Distributed Optical Fiber Acoustic Sensing Based on Linear Frequency Modulated Signal Sidelobe Suppression

Abstract While the linear frequency modulation (LFM) pulse compression technique effectively enhances the signal-to-noise ratio (SNR) and spatial resolution in distributed acoustic sensing (DAS) systems, the high sidelobes generated during the compression process significantly constrain the system’s dynamic range. To address this limitation, this paper proposes a sidelobe suppression method based on matched filter optimization. An optimized mismatch filter model is constructed to suppress range sidelobes while maintaining the mainlobe width effectively. Experimental validation was conducted using LFM signals with a pulse width of 50 μs and a bandwidth of 50 MHz over a 10 km sensing fiber. The results demonstrate that the optimized system achieves a terminal SNR of 37.05 dB, representing a significant improvement over conventional single-pulse system. Furthermore, a 24.13 dB SNR enhancement was observed for 100 Hz vibration signals, with waterfall plots confirming a clearer response to disturbances. The proposed method provides an effective signal processing solution for improving the overall performance of DAS systems.