Nanoscopic photodeposited structures analyzed by an evanescent optical method

The evanescent field propagating in waveguides was used to evaluate the profile and growth rate of laser photodeposited a-Se. A pulsed KrF excimer laser was used for deposition. The differential-evanescent light leaking image, was used to analyze the nanostructures in the deposited zones. The relation between the emerging light intensity of the evanescent wave and the optical light intensity propagating in the waveguide was connected to an effective range of the evanescent wave leaking power into the deposited material. The technique provides the nanometric profiles of the ultra-thin photodeposited structures.     

Free-space fiber hybrid distributed optical cross-connect interconnect module

We propose implementing a large-scale optical cross-connect network based on a free-space-fiber hybrid interconnect system. The free-space portion of the system is designed to handle shuffle operation of optical beams that need to intersect each other. The fiber portion is used to guide these signals to and from optical transceivers, which can be distributed at different locations. A compact and packaged prototype that handles 256x256 input-output channels is demonstrated.     

带温度补偿的分布式光纤温度传感系统设计

针对分布式光纤温度传感系统(Distributed Optical Fiber Temperature Sensing System,DTS)在线测温精度不高的问题,提出了使用光纤布拉格光栅(Fiber Bragg Grating,FBG)解调仪对DTS进行温度补偿。对不带温度补偿的DTS进行了温度测量和数据分析,证明了进行温度补偿的必要性。设计了带温度补偿的DTS并进行了温度测试。实验结果表明,在使用FBG解调仪对DTS进行温度补偿后,DTS的温度精确度可以达到0.3℃。     

基于分布式光纤的埋地自来水管多点泄漏定位方法分析

基于拉曼散射测温原理,利用分布式光纤对UPVC（硬脂聚氯乙烯）和铸铁自来水管道进行模拟泄漏点定位实验。首先对采集到的原始Anti-Stokes光信号进行滤波平滑处理,再利用相关系数法对温度检测信号进行分类分析,识别自来水管有无泄漏发生,最后通过选择性阈值法识别出UVPC管以及铸铁管中的泄漏点位置。实验结果表明,该系统运行稳定且能够准确识别自来水管泄漏情况。选择性平均阈值法的使用,能够对200 m的埋地自来水管道准确地进行泄漏点的定位,定位误差为0.25 m～0.65 m。     

超长距离分布式光纤振动传感器的并发事件信号重构方法

针对超长距离分布式振动检测传感器在复杂地表振动环境下性能指标下降的问题,提出了借鉴雷达信号处理技术领域脉冲分选技术的振动信号特征分析提取、分选和融合方案,实现了对并发振动随机混合信号的同源振动的信号分选和事件的恢复重构。对两起和四起并发事件进行了现场测试,传感器检测和报警结果准确。为超长距离分布式光纤振动传感器在复杂地表振动环境下的应用提供了可能。     

超长距离分布式光纤振动传感器的并发事件信号重构方法

针对超长距离分布式振动检测传感器在复杂地表振动环境下性能指标下降的问题,提出了借鉴雷达信号处理技术领域脉冲分选技术的振动信号特征分析提取、分选和融合方案,实现了对并发振动随机混合信号的同源振动的信号分选和事件的恢复重构。对两起和四起并发事件进行了现场测试,传感器检测和报警结果准确。为超长距离分布式光纤振动传感器在复杂地表振动环境下的应用提供了可能。     

Experimental determination of superheated liquid density by the optical fiber method

An experimental approach to determination of the density of liquid superheated with respect to the liquid-vapor equilibrium temperature, including the range of high degrees of superheating, is developed. The approach is based on application of an optical fiber method combined with a pure bubble chamber. Performance of the method for investigation of the refractive index and density for superheated liquids as functions of temperature and pressure is illustrated in experiments with n-hexane as a reference substance for thermophysical measurements. The relative density measurements are performed with a resolution up to 10^?4 at a characteristic time of 1 ms. For absolute measurements, the setup should be calibrated by the known data on the liquid density for the saturation line.     

基于环结构的新型分布式光纤振动传感系统

提出并验证了一种新颖的基于环形马赫-泽德干涉仪结构的全分布式光纤振动传感系统.采用直流光实时动态定位技术，通过在干涉仪光路中引入环结构，将直线型干涉仪转化为环型回路，使得一个马赫-泽德干涉仪中相向传输两路光波，相当于构成双马赫-泽德干涉仪.当振动信号作用于传感光纤时，相向传输的两路直流光同时产生相同的相位信号并沿不同的路径传输至光接收单元，采用数字信号处理技术分析接收信号即可实时获得振动的空间位置和频率、幅度等特性参数.实验中成功实现了监测距离为1.01km的分布式振动传感，单点振动的空间分辨率小于40m.另外，从理论上分析并模拟了系统对多点同时振动进行检测和定位的可行性.     

新型分布式光纤拉曼光子温度传感器系统

讨论了2kmFGC-W2，10kmFGC-W10和30kmFGC-W30分布式光纤拉曼光子温度传感器系统的工作原理和系统的结构，介绍了国内外分布式光纤拉曼光子温度传感系统的研究现状，提出了分布式光纤拉曼光子温度传感器系统的发展方向。     

分布式光纤中的稳健时间延迟估计方法

在分布式光纤传感系统定位中,传统时延估计算法常由于噪声相关性较强而失效。采用一种削弱相关噪声的改进型广义相关法,并针对系统特点,为进一步改善分布式光纤传感定位的准确度与稳定度,提出了一种先对数据按事件信号进行分帧,再采用卡尔曼滤波器对分帧时延估计结果进行跟踪的时延估计方案。系统仿真实验与实际数据测试结果均表明:提出的时延估计方案能够有效抑制强相关性的噪声,提高时延估计的准确度与稳定度。经大量现场测试,本文的方案能够有效地将时延估计误差稳定地控制在0.2个采样间隔以内,能够满足系统实际定位精度要求。     

分布式光纤Bragg光栅波长校准方法

提出了一种利用标准参考光谱进行波长校准的方法。实验中利用由宽带光源和光纤可调谐滤波器组成的可调谐光源分别扫描了参考光谱和传感光栅的光谱。在参考通道,ITU标准参考模块的输出是具有固定波长的梳状光谱。利用高斯拟合算法计算出由标准参考透射谱峰值输出的对应的驱动电压,通过样条插值函数获得了滤波器输出波长与驱动电压的关系。计算光栅反射谱峰值对应的驱动电压,利用上面获得的滤波器输出波长与驱动电压的关系式可以计算出传感光栅的Bragg波长。实验结果表明,在较大的波长范围内实现了对多个传感光栅的波长校准,减小了由滤波器非线性输出造成的测量误差,具有较高的重复性。     

Estimation of coupling efficiency of optical fiber by far-field method

Coupling efficiency to a single-mode optical fiber can be estimated with the field amplitudes at far-field of an incident beam and optical fiber mode. We call it the calculation by far-field method (FFM) in this paper. The coupling efficiency by FFM is formulated including effects of optical aberrations, vignetting of the incident beam, and misalignments of the optical fiber such as defocus, lateral displacements, and angle deviation in arrangement of the fiber. As the results, it is shown the coupling efficiency is proportional to the central intensity of the focused spot, i.e., Strehl intensity of a virtual beam determined by the incident beam and mode of the optical fiber. Using the FFM, a typical optics in which a laser beam is coupled to an optical fiber with a lens of finite numerical aperture (NA) is analyzed for several cases of amplitude distributions of the incident light.     

Measurement of optical fiber parameters by the backscattering method (Review)

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 3, pp. 359–372, March, 1988.     

Incident circularly polarized Raman optical activity spectrometer based on circularity conversion method

A simple incident circular polarization Raman optical activity (ICP ROA) spectrometer was constructed by applying the method of circularity conversion. The circular polarization of the incident laser light was modulated between right and left by the insertion of a half‐wave plate and not by using a Pockels cell which is usually used in ICP ROA instruments. On the basis of the concept of the virtual enantiomer (Hug, W. Applied Spectroscopy, 2003, 57, 1), circularity converters were inserted in the optical train, which could effectively compensate the systematic offset. The new instrument successfully attained photon shot‐noise‐limited conditions for all bands except for the very strongly polarized Raman band. The ROA spectra of some standard chiral samples were measured to demonstrate the performance of the spectrometer. Copyright © 2010 John Wiley & Sons, Ltd.     

偏振态对分布式光纤泄漏检测系统的影响研究

研制了一种基于Sagnac干涉仪的直线型分布式光纤传感器,可实时进行管道泄漏检测与定位。分析和研究了该干涉仪的泄漏检测原理、泄漏源定位方法以及光偏振态对传感器性能的影响。当两束光偏振态相同时,系统具有最佳的性能;当两束光正交时,无法实现信号检测。管道泄漏的实验结果表明,该系统能较准确地确定泄漏源位置,且定位误差为0.69%。     

分布式光纤温度压力传感器设计

为了实现油田井下温度压力的全分布式测量,提出了一种基于光纤散射原理的分布式温度压力测量方法。该方法通过对普通光纤进行封装设计,制作成传感光纤。由于光纤传感器周围流体的温度和压力会对传感光纤内的散射光产生调制作用,通过光纤解调仪解调出光纤拉曼散射参数和布里渊散射频移就能够实现温度和压力的实时在线测量。实验结果表明:设计的分布式光纤温度压力传感器可以实现的温度测量分辨率为0.1 ℃,压力测量分辨率为0.07 MPa。基本满足油田井下温度压力测量的全分布式、实时在线、可靠性高、精度高、抗干扰能力强等要求。     

Dual-source distributed optical fiber sensor for simultaneous temperature and strain measurements

A dual-source distributed optical fiber sensor system with combined Raman and Brillouin scatterings is designed for simultaneous temperature and strain measurements. The optimal Raman and Brillouin signals can be separately obtained by adjusting the powers of the two sources using an optical switch. The temperature and strain can be determined by processing the optimal Raman and Brillouin signals. The experimental result shows that 1.7 ?C temperature resolution and 60-με strain resolution can be achieved at a 24.7-km distance.     

分布式光纤声波振动传感系统研发及应用

针对油气田勘探开发需获取微声波信号完整波形的问题,开展了基于双脉冲外差调制与反正切外差解调方案的分布式光纤声波传感（DAS）技术研究与配套系统研发。通过特征参数室内振动模拟实验,新型DAS系统的响应频率范围20 Hz～25 kHz、最大动态范围60 dB、信噪比49 dB,满足微声波信号幅度、频率、相位等信息的探测需求。同时,该系统在新疆油田稠油热采井下蒸汽腔探测方面成功开展了现场应用,实测有效声压强度?195 dB,验证了系统的可靠性,具有良好的应用前景。     

Radiative properties of optical board embedded with optical black holes

Unique radiative properties, such as wavelength-selective transmission or absorption, have been intensively studied. Historically, geometries for wavelength-selective of light absorption were developed based on metallic periodical structures, which were only applied in the case of TM wave incidence due to the excitation of surface plasmons. In this paper, we develop an alternative approach to selective wavelength of light absorption (both TE and TM waves), based on an optical board periodical embedded with optical black holes. Numerical work was carried out to study such structure’s radiative properties within the wavelength range of 1-100 μm. The electromagnetic wave transmission through such a structure is predicted by solving Maxwell’s equations using the finite-difference time-domain (FDTD) method. Spectral absorptance varies with the period of optical black holes. When the incidence wavelength is much larger than the inner core radius, most of the light energy will be transmitted through the inner core. Otherwise, the energy will be mainly absorbed. Numerical results of the radiative properties of the optical board with different incidence wavelengths are also obtained. The effect of the oblique incidence wave is investigated. This study helps us gain a better understanding of the radiative properties of an optical board embedded with optical black holes and develop an alternative approach to selective light absorption.     

光纤分子背向散射的温度效应及其在 分布光纤温度传感网络上应用 研究的进展

讨论了光纤分子瑞利(Rayleigh)背向散射精细结构谱和光纤分子喇曼(Ra man)背向散射光谱及其温度效应,以及在分布型光纤温度传感网络上应用研究的进展。