Sagnac／Mach—Zehnder分布式光纤传感系探测及定位理论分析统

利用3×3耦合器解调算法实现对光纤沿线破坏行为的探测及预警．在确定破坏行为发生的基础上，通过将光源切换为窄带光源，使Mach—Zehnder干涉系统工作．利用互相关方法实现对破坏行为的精确定位．详细介绍并分析了该方法的系统光路和探测定位原理．     

红外吸收光谱法研究等离子体甲烷裂解规律

基于光谱吸收原理提出了利用3 391 nm He-Ne激光光源的甲烷探测方法,分析了交、直流辉光放电等离子体中甲烷裂解转化的过程和规律.探测对象选取甲烷3 390 nm附近的ν3谱带,采用单波长、双通道差分吸收探测,消除了光源不稳定及光电器件漂移等因素造成的误差影响.理论和实验表明,该方法有效地提高了系统探测的灵敏度及稳定性.     

基于萨格奈克/双马赫-曾德干涉原理的长途管道破坏预警技术研究

针对现有技术在灵敏度和监测距离上的限制,提出了一种基于萨格奈克/双马赫-曾德干涉原理的分布式光纤传感方案,并对其探测和定位原理进行了分析.结果表明,利用从萨格奈克干涉仪解调出的信号可以判断有无破坏行为的发生,利用两个马赫-曾德干涉仪的输出信号可以实现对破坏行为的定位,从而为长途管道的破坏预警提供了一种较为理想的方法.     

利用频谱组束获取双光谱光源的实验研究

 针对激光多光谱探测对多色激光光源的需求,提出利用外腔频谱组束技术获取多光谱激光探测光源的方法。报道了外腔2个大模面积双包层Er3+/Yb3+共掺光纤激光器频谱组束的实验结果,获得了一种3dB线宽分别为29.3nm和11.52nm的可调谐双光谱激光探测光源。实验结果和理论分析表明：外腔频谱组束技术是一种获得多光谱激光光源的可行方法。     

利用LED探测甲烷气体浓度的实验研究

报导了一个利用LED作光源探测甲烷浓度的差分探测系统,分析了系统中各光学元件的作用,给出甲烷浓度的计算方法及实验结果.选用甲烷在1.65 μm附近2ν3谱带中的R支作为探测对象.利用法布里-珀罗标准具的透过率曲线与甲烷吸收线相互匹配的方法滤掉无用光,并通过压电陶瓷改变标准具的腔长,从而实现了差分吸收探测,进一步提高了测量灵敏度,取得了较好的结果.     

新型LED光源气溶胶探测雷达系统优化设计与初步实验

为了实现近地面、多波长气溶胶时空探测,克服激光波长可选择性不足的问题,利用LED丰富的光谱特性,设计了一种新型发光二极管(LED)光源雷达。LED能量小且发散角大,其出光能量、发散角、接收视场角和几何重叠因子都会对LED光源雷达探测距离产生影响。针对共轴LED光源雷达系统的特点,分析了几何重叠因子的特征和计算方法,详细讨论了光源发散角和接收视场角对几何重叠因子的影响。结合LED光源的特点,利用美国标准大气模型对雷达系统的探测能力进行了仿真,优化了光源发散角和接收视场角,在LED能量一定的情况下获得了最大的探测距离。搭建了LED光源雷达系统并完成了初步实验观测,结果表明该雷达夜晚能够接收到240m远处的大气回波,验证了雷达探测低层大气气溶胶的能力。     

多波长发光二极管光源雷达系统与近地面低层大气气溶胶探测

设计并研制了一台多波长发光二极管(LED)光源雷达系统,用于探测近地面低层大气气溶胶特性.介绍了LED光源雷达系统的组成及工作原理,计算分析了系统几何重叠因子,从而确定了LED光源雷达系统的最低探测高度为60 m.研究了LED光源雷达散射回波信号的数据反演方法,根据LED光源雷达适合近距离探测的特点,采用了Fernald前向积分反演算法,并以地面能见度仪数据为基础,确定了气溶胶消光系数的边界值.利用所设计的475, 530和625 nm三个波长的LED光源雷达系统,分别在轻度污染、中度污染和重度污染天气情况下,对西安夜晚城区上空低层大气气溶胶进行了探测,获得了近300 m高度内三个波长的大气气溶胶消光系数高度分布曲线,并对近地面低层大气气溶胶的垂直分布与变化特征进行了探讨.     

双波长激光路面气象传感方法

为解决传统接触式路面气象传感器寿命低、安装不便、易破坏路基等问题,用1 310 nm、1 430 nm两种波长的激光器作为探测光源,结合红外测温辅助,研究了一种非接触的路面气象传感方法。该方法通过测量不同路面状态下由光源照射形成的后向散射光强,得到水、冰介质膜在两个特征波长下的反射率;通过设定反射率和红外温度信号的判别逻辑,可以分辨多种路面状态,包括干燥、潮湿、积水、结冰和结霜;以朗伯比尔定律为基础建模实现积水、结冰厚度检测,利用反射率零点自动判别校准测量模型参数,无需现场标定即可在不同道路条件下实现精准测量。实验证明,该方法路面状态判别准确,水/冰厚度检测量程达到3 mm,精度均为±0.2 mm,具有结构简单、探测距离远、成本低等特点,有良好的实用价值。     

用于微型生化分析的光探测系统

针对微生化芯片样品剂量少和与微流体芯片集成等要求,设计了两种在芯片内用分光光度法对混合后液体的吸收光谱进行探测的方法。实验利用510～840 nm的可见光光源,采用了直接探测法和消逝波探测法对样品进行探测。通过两种方法的比较证明：直接探测法具有原理简单、消耗样品量少和结构容易实现等优点;消逝波探测法具有需要样品量极少、灵敏度高和易于集成的优点。     

能见度仪探测光束平行度检测方法

为实现能见度计算中消光系数的正确测量,论述了光源平行度在能见度测量中的重要作用,设计了探测光束发散角检测方法与测量装置。该装置包括定焦成像系统和移动光源的直线系统,利用成像关系与空间几何关系推导了发散角表达式。以紫外LED作为实验光源,设计完成了测量系统成像装置与控制软件,计算得到水平方向与垂直方向发散角,利用所得发散角分析探测光束。实验结果表明,紫外LED光源的光束发散角水平与垂直方向分别为78°和69°,经比较得到未加入平行度的能见度与加入后的比值为051。该方法测得的能见度值更接近于实际值。     

An optical fiber sensor based on cladding photoluminescence for high power microwave plasma ultraviolet lamps used in water treatment

Low-pressure mercury lamps are commonly used for germicidal applications such as water and wastewater sterilisation. The germicidal effect is due to the emission of light at 254 nm, which leads to the destruction of most waterborne bacteria. The Microwave plasma ultraviolet lamp (MPUVL) is a new technology for generating a high intensity ultraviolet (UV) light. A Fluorescent optical fiber based sensor is presented which is used for monitoring the output of a high power microwave UV light source and its control. This sensor is a fiber which has had its cladding removed and been coated with a phosphor doped polymer. This paper was originally presented at the 2001 International Conference (2nd Joint OSJ-SPIE Conference) on Optical Engineering for Sensing and Nanotechnology, ICOSN 2001 which was held June 6–8, 2001 at the Pacifico-Yokohama Conference Center, Yokohama, Japan.     

白光干涉双环传感网络理论与实验研究

构造了一种基于双环形拓扑结构的白光干涉光纤传感网络．可用于智能结构中准分布应变或温度的测量。光纤传感网络基于空分多路复用技术(SDM)．目的是增强带载能力．降低单点传感器的测量成本,并借助丁双端口问询技术．增强传感网络的抗毁坏能力。分析了环形网络结构的低相干多路复用原理．根据空分复用的光程匹配条件．推导了传感器干涉信号的强度特性。实验中对连接9个传感器的双环传感网络特征及其抗损坏特性进行了验证．并对实验结果进行了分析和讨论。     

Simulation of the destruction of a woodland massif by the shock wave generated by the impact of a large cosmic body

The interaction of shock waves with woodland massifs with consideration given to vegetation destruction is examined. The results of numerical simulations of the propagation of a perturbation through a vegetation massif based on solving the Euler equations for two-dimensional and axisymmetric cases are presented. This approach was used by the present author in simulating the propagation of wave fronts through woodland massifs without regard for forest stand destruction. The effect of vegetation is reproduced by introducing bulk forces in the volume occupied by forest. An initial perturbation of explosion-in-flight type was specified in the form of an increased-pressure region located at various heights from the ground surface. Simple threshold models are used to examine the effect of the dynamic pressure on vegetation destruction. A refined model was developed to investigate the change in the configuration of woodland massifs with consideration given to vegetation fall and the effect of this process on the rate of perturbation dissipation. The system of equations was solved by the Godunov method implemented using parallel programming. Numerical experiments were conducted with the use of two types of models of forest stand destruction, with various threshold values of the destruction factor, various initial perturbation intensities, and various heights above the vegetation massif. The effects arising during the interaction of a high-intensity perturbation with a woodland massif were identified. An analysis of the results showed that the destruction of vegetation occurs during its interaction with the fronts of the incident and reflected shock wave and with the jet core of the perturbation. In some cases, the model taking into account the accumulation of fallen vegetation predicts situations where destruction will occur only in the upper part of the forest stand, without touching the canopy. This effect can explain the existence of such regions in the area of the Tunguska event. It was also demonstrated that estimates of the sizes of the destruction zones obtained with the use of the models taking into account the influence of vegetation on the perturbation and destructibility differ substantially from those obtained within the framework of the models without regard for vegetation resistance. The highest range of perturbation dissipation was predicted by the models simulating the formation of obstructions.     

常见氯盐溶液中阳离子对水分子氢键影响的拉曼光谱研究

为了全面认识地质流体中常见阳离子对水的结构的影响, 在室温下通过对NaCl—H₂O,CaCl₂—H₂O,MgCl₂—H₂O,CuCl₂—H₂O,ZnCl₂—H₂O和FeCl₃—H₂O体系中水的O—H伸缩振动拉曼谱3 400 cm-1左右的最大峰频率的移动和低于3 433 cm-1强肩峰强弱的系统研究,考察了常见阳离子的离子电荷、离子半径、离子所属族以及络合效应等因素对水的O—H伸缩振动拉曼光谱的影响。并首次通过络合物的生成和阳离子破坏效应的共同作用来讨论相同浓度的不同种类氯盐溶液中阳离子对水氢键的影响,得到结论,对水的氢键的破坏作用：CaCl₂＞MgCl₂＞FeCl₃＞NaCl＞ZnCl2＞CuCl₂。     

基于飞秒激光直写光纤光栅的掺镱光纤激光器

 利用飞秒激光微加工技术,可以在光纤纤芯内直写出布拉格光栅,它与传统的光纤光栅制作方法相比,具有耗时短、无需光敏光纤、周期可任意设定、光栅稳定性高等优点。采用800 nm钛宝石飞秒激光器,在Hi1060光纤内写入一支8 mm长的布拉格光栅,光纤光栅的周期为2.9 μm,这是中心波长为1 042 nm的八阶光纤布拉格光栅。将所得光栅与一段有源的双包层光纤熔接,作为激光输出镜,利用975 nm的LD光纤模块作为泵浦源,采用端泵浦技术构成双包层光纤激光器。双包层光纤采用Nufern公司镱(Yb³⁺)离子掺杂双包层光纤,光纤长度3 m。所得激光器的输出功率为71.1 W,中心波长1 042 nm,带宽约为0.8 nm。     

Theoretical Study on Destruction Mechanism of 2,3,7,8-TCDD by O3 and NO3

采用B3LYP/6-31G(d)方法优化获得O₃及NO₃降解2,3,7,8-TCDD反应通道上驻点的几何构型, 得到微观反应进程,并采用MP2/6-311G(d,p)//B3LYP/6-31G(d)方法计算得到相关反应的活化能. 研究表明,O₃和NO₃采用不同的方式对2,3,7,8-TCDD进行降解. O₃通过臭氧加成及碳碳双键断裂使2,3,7,8-TCDD降解,而NO₃通过氯取代反应使得2,3,7,8-TCDD上2,3,7,8取代位置上的氯原子被取代为氧原子,从而达到有效降解的目的. O₃降解2,3,7,8-TCDD的反应能垒显著小于NO₃降解2,3,7,8-TCDD的反应能垒,表明O₃降解2,3,7,8-TCDD的能力显著高于NO₃.     

外腔两束光纤激光频谱组束的实验研究

报道了外腔2个大模面积双包层Er3+/Yb3+共掺光纤激光器频谱组束的实验结果,获得了最大功率为0.80 W、组束效率高达82.5%的组束激光输出。演示和分析了光纤末端放置位置的改变、光栅的旋转对输出光谱和组束效率的影响,结果表明:当光纤末端距系统轴的位置超过某一定值时,输出光谱呈现多模;当光栅与水平面所成角度减小时,组束效率逐渐增大。     

Er^3＋／Yb^3＋掺杂全光纤环形激光器

本文报道利用Er~(3+)/Yb~(3+)掺杂单模光纤首次研制成功的环形谐振腔结构的可调谐(调谐范围宽于70nm)全光纤激光器的设计原理及其实验结果.     

Fiber fuse behavior in k W-level continuous-wave double-clad field laser

In this study, original experimental data for fiber fuse in k W-level continuous-wave(CW) high power double-clad fiber(DCF) laser are reported. The propagating velocity of the fuse is 9.68 m/s in a 3.1-k W Yb-doped DCF laser. Three other cases in Yb-doped DCF are also observed. We think that the ignition of fiber fuse is caused by thermal mechanism,and the formation of bullet-shaped tracks is attributed to the optical discharge and temperature gradient. The inducements of initial fuse and formation of bullet-shaped voids are analyzed. This investigation of fiber fuse helps better understand the fiber fuse behavior, in order to avoid the catastrophic destruction caused by fiber fuse in high power fiber laser.