Time-domain resolution enhanced fiber loop ring-down system based on microwave photonics for pressure and curvature measurement

A dual-channel fiber loop ring-down (FLRD) sensing system with enhanced time-domain resolution based on microwave photonics is proposed and experimentally demonstrated. The integration of FLRD and microwave photonics enables fast response, high SNR and pure frequency domain measurement compared to traditional time-domain FLRD systems. The system employs the ring-down time for demodulation, which is extracted from the fitted ring-down curve of the time-domain signal. By structure optimization and efficient utilization of time intervals, the pulsed signals from two loops are interleaved, thereby trading shorter signal observation time for higher time-domain resolution. The increased time resolution enhances the signal quality and peak-fitting accuracy, leading to more precise ring-down time estimation and demodulation. The proposed system successfully realizes the sensing of pressure and curvature, with sensitivities of 5.154 ns/N and 0.1716 μs/cm^-1, respectively. The R² coefficients improve to 0.995 and 0.991, while RMSE values decrease to 0.116 N and 0.162 m^-1, demonstrating superior performance over the existing multi-function FLRD sensing system.