光纤电流传感技术研究进展

电力系统计量和继电保护对电流传感器技术的要求越来越高,传统的电磁式互感器已经不能满足要求。自从光纤电流传感器问世以来,主要研究集中在如何减小双折射和温度对传感器性能的影响。从光纤电流传感技术的原理着手分别阐述了光纤电流传感领域的研究现状、新技术、新发现以及发展前景等内容,并进行了综合分析、归纳整理,详细介绍了光纤电流传感器的研究进展。     

基于配焦椭流线法和梯度优化的自由反射面设计

结合配焦椭流线法和梯度算子,提出了一种针对LED扩展光源的自由反射曲面优化设计方法,其中配焦椭流线法负责生成自由反射曲面,梯度算子实现逐代优化。以线度为5 mm的LED扩展光源的轴对称均匀投光为例,完成了单个光滑连续自由反射面的设计和优化。光学仿真结果表明,优化前初级照度均匀度约为0.77,而优化后达到0.98,效果良好,并具有向非轴对称自由反射曲面设计拓展的可能性。     

光纤光栅传感网络在油气出地管内腐蚀监测的应用研究

油气管线内部腐蚀是导致管线失效的主要因素。针对这一问题,采用复用技术设计了一种基于光纤布拉格光栅的管线内腐蚀监测系统。该系统通过出地管线外表面的应力变化来确定内表面的腐蚀程度,利用7路光纤光栅传感器组成阵列式传感网络,通过温度补偿光栅实现温度补偿。实验表明,该系统测压精度较高,系统误差小于2.23%。用现场实际压力数据验证了系统的可行性与稳定性,该系统完全满足油气管线内部缺陷在线监测的要求。     

基于VB、Matlab和Access的石油井架应力测量系统

基于分布式光纤光栅传感器网络和Modbus RTU通讯协议,实现了石油井架应力多点测量与数据自动采集、记录和分析.通过OLE技术和MatrixVB组件,VB与Matlab、Acces8的无缝连接,现场数据经算术平均滤波后写入到Access后台数据库中.Matlab计算模块根据测试点应力值计算出的井架承载能力及绘制杆件和...     

The effect of plane booster reflectors on the performance of a solar air heater with solar cells suitable for a solar dryer

We present a theoretical study of a solar photovoltaic-thermal (hybrid) system consisting of a flat-plate solar air heater mounted with solar cells and a plane booster. A conventional flat-plate collector is converted into a hybrid system by mounting solar cells directly on the absorber plate. A hybrid system is self-sufficient in the sense that the electrical energy required by the pump is supplied by the panel. Such systems are well suited to applications such as solar drying. The combined system is analysed for the case when the radiative and absorptive properties of the cell surface and the absorber plate are nearly the same. The solar cell efficiency is a linearly-decreasing function of the absorber plate temperature. The performance of the system has been evaluated for various combinations of boosters. The minimum area of the solar cells required to run the pump at a given flow rate has been calculated as a function of time, with and without boosters. The minimum cell area required decreases with the use of boosters. High cost cells may be replaced by low cost reflectors. The solar air heaters presently available on the market are not suitable for direct conversion to hybrid systems.     

Experimental and simulation study of thin film silicon solar cells with intermediate reflector

Optical and electrical simulations were carried out for thin film silicon solar tandem cells with intermediate reflector layer (IRL) between top and bottom cell and compared with experimental external quantum efficiency and current voltage characteristics results. Reference data were collected from a series of tandem cells with different thicknesses of the top cell absorber layer (160–240 nm), the bottom cell absorber layer (1750–2100 nm), and the transparent conductive oxides based IRL (10–80 nm). It turned out that for capturing correctly the influence of the IRL on the light management as a function of the IRL thickness, the conventional semicoherent approach is not sufficient. Whereas the optical properties of a very thin IRL are governed by interference effects that are best calculated using a fully coherent model, increasingly thicker IRL show a more and more incoherent behavior. By taking into account, the interface morphology and angular light distribution within the cell stack an algorithm for the effective IRL reflectivity was proposed that explains the experimental findings very well. The consecutive electrical simulations were carried out with the device simulator ASA. The dependence of short circuit current density j_sc and fill factor FF on the thickness d_IRL of the IRL is in qualitative agreement between simulation and experiment showing coincident extrema in j_sc(d_IRL) and FF(d_IRL) at the current matching point. Copyright © 2013 John Wiley & Sons, Ltd.     

线形腔半导体可饱和吸收镜被动锁模掺镱光纤激光器

皮秒脉冲在超连续谱光源中具有重要应用,基于线形腔搭建了半导体可饱和吸收镜(SESAM)被动锁模皮秒脉冲掺镱光纤激光器,详细分析对比了激光器中所用光纤光栅的反射率、反射带宽以及SESAM的宏观特性参数对锁模激光器输出脉冲特性的影响。实验结果表明:选择10%反射率和0.3nm反射带宽的光纤光栅比较有利于激光器的稳定锁模;光纤激光器对SESAM参数的适用范围比较大,SESAM的非饱和损耗对激光器输出平均功率影响较大,SESAM的非饱和损耗越小,激光器输出脉冲的平均功率越高。     

正十二边形光子晶体光纤光栅特性的研究

设计了一种包层结构为圆形空气孔呈正十二边形对称排列的光子晶体光纤,通过Comsol软件结合有限元法,得出各波长与传输模式有效折射率之间的函数关系。结合耦合模理论和传输矩阵法,利用Matlab软件,对正十二边形结构的光子晶体布拉格光纤光栅的反射谱特性进行了研究分析,具体分析了不同占空比下的传输模式以及反射谱特性。研究表明随着光波波长的增加,传输模式的有效折射率随之下降;随着空气孔层数的增加,谐振波长增大,谐振峰强度增强。随着占空比的增大,传输模式数增多,谐振波长减小,而谐振峰强度基本不变。     

单FBG双波长掺铒光纤激光器的设计与实验研究

为给密集波分复用(DWDM)光纤通信及光纤传感系统提供理想光源,设计了一种双波长环形腔掺铒光纤激光器。该激光器采用单支光纤光栅(FBG)和2个3dB耦合器构成可调谐光滤波器,结合多模光纤的偏振烧孔效应,通过改变系统的偏振态来获得波长可调谐的双波长激光输出。实验结果表明:改变系统的偏振态时,可分别获得单波长和双波长激光输出,双波长光纤激光器的最大波长差为4.692nm。引入多模光纤后,激光跳模现象得到明显抑制。     

Strain and Displacement Controls by Fibre Bragg Grating and Digital Image Correlation

Test control is traditionally performed by a feedback signal from a displacement transducer or force gauge positioned inside the actuator of a test machine. For highly compliant test rigs, this is a problem since the response of the rig influences the results. It is therefore beneficial to control the test based on measurements performed directly on the test specimen. In this paper, fibre Bragg grating (FBG) and Digital Image Correlation (DIC) are used to control a test. The FBG sensors offer the possibility of measuring strains inside the specimen, while the DIC system measures strains and displacement on the surface of the specimen. In this paper, a three‐point bending test is used to demonstrate the functionality of a control loop, where the FBG and DIC signals are used as control channels. The FBG strain control was capable of controlling the test within an error tolerance of 20 µm m^?1. However, the measurement uncertainty offered by the FBG system allowed a tolerance of 8.3 µm m^?1. The DIC displacement control proved capable of controlling the displacement within an accuracy of 0.01 mm.