多芯光纤安防工程一体化同步感知系统

Multicore Fibre Based Monolithic Sensing System of Security Engineering

光纤传感技术可用于安防工程中的各类扰动探测。然而,常规单模光纤安防系统无法同步实现感知入侵模式、量化扰动强度、火灾预警等重要功能。本研究提出基于空分复用多芯光纤的一体化同步感知系统,将多种光纤传感技术复用于一根7芯光纤,其中,光纤光栅纤芯监测结构点式应变与细部温度,相位敏感纤芯实现扰动定位与强度定量,同时拉曼纤芯测量分布式温度场。面向安防实际需求,在后处理阶段通过高阶中心矩、信号极差、空间平均峰度与特征频率等4种方法实现了多参量入侵定位;提出多指标扰动定量方法,其中,面向瑞利散射信号的扰动量化算法利用瑞利散射模型与多参数优化方法,根据光强信号图样求解分布式应变场,搭配光栅纤芯的应变时程,以此构建扰动强度指标,实现多指标扰动定量评估及模式区分;通过拉曼温度场实现火灾(过热)预警,同时提供温度补偿。在防护围栏上通过7种模拟工况测试了系统的工作性能,结果表明:本系统的4种定位方法得到了各工况事件的不同时空频特征,能准确定位各事件(定位误差<1 m),其中特征频率法还能有效识别出微小地面振动;定量识别15种强度的冲击荷载,各量化指标与扰动强度的正相关性较好;可同步感知光纤沿线温度场并定位过热点,光栅纤芯与拉曼测温纤芯的结果相符合。本系统解决了传统安防系统监测信息单一、容易误漏报、可信度不足的问题,突破了温度应变交叉敏感、缺乏定量感知能力等技术瓶颈。

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 calcu lated 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.