In this paper, we propose a Fresnel reflection-based optical fiber sensor system for remote refractive index measurement using the optical time domain reflectometry technique as an interrogation method. The surroundin...In this paper, we propose a Fresnel reflection-based optical fiber sensor system for remote refractive index measurement using the optical time domain reflectometry technique as an interrogation method. The surrounding refractive index from a long distance away can be measured easily by using this sensor system, which operates based on testing the Fresnel reflection intensity from the fiber-sample interface. This system is a simple configuration, which is easy to handle. Experimental results showed that the range of this measurement could reach about 100.8km, and the refractive index sensitivities were from 38.71 dB/RIU to 304.89 dB/RIU in the refractive index （RI） range from 1.3486 to 1.4525.展开更多
Distributed temperature sensing(DTS)using heated cables has been recently developed for distributed monitoring of in-situ soil moisture content.In this method,the thermal and electrical properties of heated cables hav...Distributed temperature sensing(DTS)using heated cables has been recently developed for distributed monitoring of in-situ soil moisture content.In this method,the thermal and electrical properties of heated cables have a significant influence on the measurement accuracy of soil moisture content.In this paper,the performances of two heated cables,i.e.the carbon-fiber heated cable(CFHC)and the metalnet heated cable(MNHC),are studied in the laboratory.Their structures,uniformity in the axial direction,measurement accuracy and suitability are evaluated.The test results indicate that the MNHC has a better uniformity in the axial direction than CFHC.Both CFHC and MNHC have high measurement accuracy.The CFHC is more suitable for short-distance measurement(500 m),while the MNHC can be used for longdistance measurement(>500 m).展开更多
Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a ...Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a distributed measurement system for in-situ soil moisture content （SM-DTS） is introduced.The system is based on carbon-fiber heated cable （CFHC） technology that has been developed to enhancethe measuring accuracy of in-situ soil moisture content. Using CFHC technique, a temperature characteristicvalue （Tt） can be defined from temperatureetime curves. A relationship among Tt, soil thermalimpedance coefficient and soil moisture content is then established in laboratory. The feasibility of theSM-DTS technology to provide distributed measurements of in-situ soil moisture content is verifiedthrough field tests. The research reported herein indicates that the proposed SM-DTS is capable ofmeasuring in-situ soil moisture content over long distances and large areas.展开更多
当前通信光缆故障检测时,主要通过单向光时域反射仪(Optical Time Domain Reflectometer,OTDR)测试获取光缆运行数据,但仪表测试距离的限制会影响采集数据的完整程度,导致故障智能检测结果F1值较低。因此,提出一种以双向OTDR测试为核心...当前通信光缆故障检测时,主要通过单向光时域反射仪(Optical Time Domain Reflectometer,OTDR)测试获取光缆运行数据,但仪表测试距离的限制会影响采集数据的完整程度,导致故障智能检测结果F1值较低。因此,提出一种以双向OTDR测试为核心的通信光缆故障智能检测方法。应用多个光时域反射仪建立双向OTDR测试方案,实时采集通信光缆运行数据,并结合双向拉曼分布式放大技术,弥补光纤传输损耗。依托于小波变换算法分解测试信号,从时域和频域2个方面提取光缆运行信号特征。利用故障树概念构建通信光缆故障树,检测出当前通信光缆存在故障类型,并定位故障点具体位置。实验结果表明:所提方法应用后,得出的通信光缆故障智能检测结果F1值为0.93,满足智能检测精度要求。展开更多
光缆维护时存在着故障点的位置定位不精确的问题,给光缆维护和抢修带来了困难。为解决这一问题提出了基于光时域反射仪(Optical Time Domain Reflectometer,OTDR)的光缆故障点精确定位方法。该方法结合了OTDR和偏振光时域反射技术(Polar...光缆维护时存在着故障点的位置定位不精确的问题,给光缆维护和抢修带来了困难。为解决这一问题提出了基于光时域反射仪(Optical Time Domain Reflectometer,OTDR)的光缆故障点精确定位方法。该方法结合了OTDR和偏振光时域反射技术(Polarization Optical Time Domain Reflectometry,POTDR),使用OTDR得到光缆故障点的光纤光学长度,利用POTDR分别获取光缆弯曲时和光缆恢复原状时的两组后向散射数据,用差值法和寻找斜率变化的方法对两组后向散射数据进行处理,可以确定光缆弯曲点的位置。结合光纤光学长度、弯曲点的位置及光缆余长系数,得出弯曲点与光缆故障点的距离,当弯曲点距离光缆故障点位置比较近时(小于200m),对光缆故障点的定位很精确。实验结果表明,该方法能够精确地定位光缆故障点位置,结构简单,操作方便且不损伤光缆。展开更多
文摘In this paper, we propose a Fresnel reflection-based optical fiber sensor system for remote refractive index measurement using the optical time domain reflectometry technique as an interrogation method. The surrounding refractive index from a long distance away can be measured easily by using this sensor system, which operates based on testing the Fresnel reflection intensity from the fiber-sample interface. This system is a simple configuration, which is easy to handle. Experimental results showed that the range of this measurement could reach about 100.8km, and the refractive index sensitivities were from 38.71 dB/RIU to 304.89 dB/RIU in the refractive index （RI） range from 1.3486 to 1.4525.
基金The financial supports provided by the National Natural Science Foundation of China(Grant Nos.41230636,41372265,41427801)National Basic Research Program of China(973 Project)(Grant No.2011CB710605)
文摘Distributed temperature sensing(DTS)using heated cables has been recently developed for distributed monitoring of in-situ soil moisture content.In this method,the thermal and electrical properties of heated cables have a significant influence on the measurement accuracy of soil moisture content.In this paper,the performances of two heated cables,i.e.the carbon-fiber heated cable(CFHC)and the metalnet heated cable(MNHC),are studied in the laboratory.Their structures,uniformity in the axial direction,measurement accuracy and suitability are evaluated.The test results indicate that the MNHC has a better uniformity in the axial direction than CFHC.Both CFHC and MNHC have high measurement accuracy.The CFHC is more suitable for short-distance measurement(500 m),while the MNHC can be used for longdistance measurement(>500 m).
基金The financial supports provided by the National Natural Science Foundation of China(Grant Nos.41230636,41372265,41427801)National Basic Research Program of China(973 Project)(Grant No.2011CB710605)
文摘Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a distributed measurement system for in-situ soil moisture content （SM-DTS） is introduced.The system is based on carbon-fiber heated cable （CFHC） technology that has been developed to enhancethe measuring accuracy of in-situ soil moisture content. Using CFHC technique, a temperature characteristicvalue （Tt） can be defined from temperatureetime curves. A relationship among Tt, soil thermalimpedance coefficient and soil moisture content is then established in laboratory. The feasibility of theSM-DTS technology to provide distributed measurements of in-situ soil moisture content is verifiedthrough field tests. The research reported herein indicates that the proposed SM-DTS is capable ofmeasuring in-situ soil moisture content over long distances and large areas.
文摘当前通信光缆故障检测时,主要通过单向光时域反射仪(Optical Time Domain Reflectometer,OTDR)测试获取光缆运行数据,但仪表测试距离的限制会影响采集数据的完整程度,导致故障智能检测结果F1值较低。因此,提出一种以双向OTDR测试为核心的通信光缆故障智能检测方法。应用多个光时域反射仪建立双向OTDR测试方案,实时采集通信光缆运行数据,并结合双向拉曼分布式放大技术,弥补光纤传输损耗。依托于小波变换算法分解测试信号,从时域和频域2个方面提取光缆运行信号特征。利用故障树概念构建通信光缆故障树,检测出当前通信光缆存在故障类型,并定位故障点具体位置。实验结果表明:所提方法应用后,得出的通信光缆故障智能检测结果F1值为0.93,满足智能检测精度要求。
文摘光缆维护时存在着故障点的位置定位不精确的问题,给光缆维护和抢修带来了困难。为解决这一问题提出了基于光时域反射仪(Optical Time Domain Reflectometer,OTDR)的光缆故障点精确定位方法。该方法结合了OTDR和偏振光时域反射技术(Polarization Optical Time Domain Reflectometry,POTDR),使用OTDR得到光缆故障点的光纤光学长度,利用POTDR分别获取光缆弯曲时和光缆恢复原状时的两组后向散射数据,用差值法和寻找斜率变化的方法对两组后向散射数据进行处理,可以确定光缆弯曲点的位置。结合光纤光学长度、弯曲点的位置及光缆余长系数,得出弯曲点与光缆故障点的距离,当弯曲点距离光缆故障点位置比较近时(小于200m),对光缆故障点的定位很精确。实验结果表明,该方法能够精确地定位光缆故障点位置,结构简单,操作方便且不损伤光缆。
