多 芯 光 纤 安 防 工 程 一 体 化 同 步 感 知 系 统

Optical fibre sensing techniques have been applied in security engineering to detect disturbances. However, most of the conventional single-mode-fibre based distributed security monitoring systems fail to simultaneously implement important functions such as recognizing intrusion patterns, quantifying the intensities and warning early fire. In this study, a monolithic multi-parameter sensing system using a multicore fibre based on spatial-division-multiplex sensing was developed to meet the expanding demands in security engineering. In the system, the local strains and temperatures were monitored by the core with fibre Bragg gratings (FBG), the external disturbances were localized and quantified by the phase-sensitive core, and the temperature field was measured and the overheated was identified by the Raman core. In the post-process, 4 intrusion localization methods were adopted for multi-level intrusion identification, namely the high-degree central moment, signal range, spatial average kurtosis and eigen-frequency method. The multi-index disturbance quantitative evaluation method was proposed, the strain field was calculated according to the signal patterns by the subsidiary disturbance quantification algorithm for Rayleigh backscattering signal, and the strain histories of FBG core were considered as well, such that the quantitative disturbance indices could be derived and utilized to quantify intrusion intensities as well as recognize the patterns; the fire alarms were released based on the real-time temperature field that also contributed to compensating strain measurement. The performance of the proposed system was evaluated by 7 practical tests on a steel fence structure. The results demonstrated that features of each intrusion event were acquired in time, space and frequency domain through 4 localization methods, intrusions were localized accurately (errors <1 m), and the moderate ground vibration could be identified through the eigen-frequency method; in the weight-impact test, 15 disturbance intensities were correctly quantified and the quantitative indices presented positive correlation with impact intensities; the temperature field along the fibre was synchronously obtained with the heated region localized, and the result of FBG agreed well with that of Raman core. The developed system serves as a novel method to overcome drawbacks of conventional systems, including monitoring parameter deficiency and poor reliability, and solves typical problems in security monitoring such as temperature-strain cross-sensitivity and disturbance quantification.