High-Spatial-Resolution Quasi-Distributed Fiber Sensing Technique Based on Cascaded FP Cavities and DSP Algorithm

A quasi-distributed fiber sensing technique with high spatial resolution is proposed and achieved by multiplexing Fabry-Perot (FP) cavities with optical frequency-domain reflectometry (OFDR). Two types of FP cavities are designed and fabricated to realize temperature and relative humidity (RH) sensing, respectively. A digital signal processing (DSP) algorithm is developed to compensate for the nonlinear frequency tuning errors induced by the laser source. The FP sensors could be located in the spatial domain and demodulated in the wavelength domain, allowing the interference spectra for quasi-distributed sensing. The sensing experiment is carried out by using the OFDR combined with three sets of cascaded FP cavities, and the fiber link information with extremely high spatial resolution is obtained. The sensitivity of each sensor to RH and temperature is measured, and the stability of the system is numerically evaluated using the RH detection limit. The proposed method provides a novel approach to quasi-distributed sensing based on FP cavities and has significant application prospects.