基于OTDR的集成监控管理系统的设计与实现分析

光时域反射仪(OTDR)是光纤测量中最主要的仪器,被广泛地应用于光纤光缆工程的测量、施工、维护和验收工作中,是光纤系统中使用频度最高的现场仪器,被人形象地称为光通信中的“万用表”。为了更好地解决传统OTDR价格相对昂贵、无法进行实时监测等弊端,明确提出了一种采用虚拟仪器技术设计的基于PC的OTDR新方案,采用PC-DAQ系统结构,由数据采集卡和数据处理方法两大部分组成,可实现光纤回传数据信号的实时采集、存储和解析,具有一定的工程实用价值。

基于PSO-SVM的Φ-OTDR系统模式识别研究

针对相位敏感光时域反射仪(phase sensitive optical time domain reflectometer,Φ-OTDR)系统中误报率高的问题,提出一种多域特征提取与粒子群算法优化支持向量机(particle swarm optimization-support vector machine,PSO-SVM)相结合的模式识别算法。首先,对原始信号进行差分处理后提取时域特征,并利用小波包分解方法,通过验证不同分解层数下的事件分类准确率,设定最优分解层数为6层,提取差分信号的能量特征。然后以SVM分类器为基础,利用PSO算法优化SVM分类器参数,提高光纤振动信号识别准确率。最后利用Φ-OTDR事件数据集进行验证,实验结果表明,该模式识别算法达到了95.6%的振动事件分类准确率。

Broadband multi-channel quantum noise suppression and phase-sensitive modulation based on entangled beam

We present a theoretical scheme for broadband multi-channel quantum noise suppression and phase-sensitive modulation of continuous variables in a coupled resonant system with quantum entanglement properties.The effects of different coupling strengths,pumping power in suppressing quantum noise and controlling the width of quantum interference channels are analyzed carefully.Furthermore,quantum noise suppression at quadrature amplitude is obtained with phase-sensitive modulation.It shows that the entanglement strength of the output field and the quantum noise suppression effect can be enhanced significantly by a strong pumping filed due to interaction of pumping light with the nonlinear crystal.The full width at half maxima(FWHM)of the noise curve at the resonant peak(△=0 MHz)is broadened up to 2.17 times compared to the single cavity.In the strong coupling resonant system,the FWHM at △=0 MHz(△=±3.1 MHz)is also broadened up to 1.27(3.53)times compared to the weak coupling resonant system case.The multi-channel quantum interference creates an electromagnetically induced transparent-like line shape,which can be used to improve the transmission efficiency and stability of wave packets in quantum information processing and quantum memory.

基于BOTDR分布式检测技术的光缆隐蔽性缺陷识别

提出基于布里渊光时域反射(Brillouin optic time domain reflectometer,BOTDR)分布式检测技术与解调信号的光缆隐蔽性缺陷识别方法,识别检测光缆隐蔽性缺陷。在生产阶段将光纤植入多股碳纤维导线复合芯内部作为传感器,依据BOTDR技术与光时域反射(optic time domain reflectometer,OTDR)技术原理,构建关于碳纤维导线光缆隐蔽性检测的分布式传感系统,利用光纤对温度、应力、传播损耗的高精度感知,多维度地分析碳纤维导线光缆的隐蔽性缺陷及位置分布,实现光缆的隐蔽性缺陷识别。利用morlet小波解调布里渊散射信号,提取包络信息,去除信号噪声,采用列文伯格-马夸尔特算法,拟合布里渊散射谱数据,精确估计最优Brillouin频移量参数,提升整体缺陷识别精度。实验证明:该方法可以准确地对光缆的隐蔽性缺陷进行表征,实现多股碳纤维导线光缆隐蔽性缺陷的快速、有效识别,促进碳纤维导线光缆更好地应用于增容、大跨越等工程中。

基于OTDR的汽车动力电池温度解调与采集研究

加强动力电池安全管理技术研发已成为新能源汽车产业发展过程中的一个重要课题,文章采用基于光时域反射仪(OTDR)技术的测温原理对电池组单体电池进行分布式采集。对比单路解调法和双路解调法,得到采用双通道的双路解调法更适合动力电池温度的解调。搭建由波分复用模块、放大器模块、模数转换模块、温度显示及报警系统等组成的温度采集系统,对微弱的斯托克斯及反斯托克斯光进行采集,在Proteus8.9软件中搭建了测温系统的电路图并进行仿真测试,使用变阻器模拟信号源验证了系统温度显示和异常报警的功能。

φ-OTDR相位提取程序的设计

阐述相位敏感型光时域反射仪(φ-OTDR)利用光纤实现沿线振动的分布式测量,φ-OTDR通过光相位变化反映光纤沿线的振动状态,相位提取是φ-OTDR技术的关键。针对相位提取过程中的数字正交解调、振动定位和相位解卷绕的主要步骤,介绍程序设计的实现方法,并给出流程图。通过对数据的处理,验证实现方法的有效性。

Φ-OTDR系统的数字信号处理及应用

相位敏感光时域反射(Φ-OTDR)传感系统具有高动态响应、高灵敏等特点,在大型工程结构健康监测领域具有巨大的应用潜力。而Φ-OTDR系统仪器化水平和工程应用很大程度上取决于数字信号处理(DSP)技术。本文对比分析了近年来Φ-OTDR系统在信号的量化、解调、抑噪以及模式识别上主要的数字信号处理方法和技术,并通过架空输电线路状态监测、埋地电缆外破预警两个应用实例,阐述了工程应用中数字信号处理与行业背景知识相结合的重要性和方法,并对Φ-OTDR系统中数字信号处理方法的发展现状和趋势进行了总结与展望。

基于OTDR的电力通信光纤性能测量与数据分析技术研究

光纤通信系统中的光纤性能测量,对于电力系统的正常工作具有重要意义。针对大范围电力通信数据存在检测困难的问题,文中通过引入高灵敏度的光时域反射仪,有效提高了检测的空间分辨率,同时也保证了测量的范围。为解决干扰信号对后续数据分析的影响,在对光信号进行分析的基础上采用噪声补偿的方法显著降低了传感器的噪声损失,从而防止了恶劣环境下传感器性能的下降。静态实验测量结果表明,当光纤长度在500 m以内时,其信号标准差均在0.055 rad以内,基于实验结果进一步明确了该测量技术的最佳适用范围,证明了该系统具有良好的抗干扰能力。

基于频分复用φ-OTDR的高频振动检测与解调

相位敏感光时域反射计(φ-OTDR)是一种借助光纤为传感媒介,检测外部振动信息的可靠方案。为提高系统的探测频率,设计了一种双脉冲频分复用结构的φ-OTDR系统。通过对双脉冲信号中的其中一路采用频分复用技术处理,产生用于检测动态相位变化的不同频率载波信号,使更多的探测脉冲可以同时在光纤中传输。并针对振动信号的解调,提出一种微分自交叉相除的反正切(PGC-DSD-Arctan)算法,解决了传统算法中解调效果受调制深度影响的问题,具有更好的适用性和更高的稳定性。通过搭建系统平台,可以有效地在10 km传感范围内检测并解调出20 kHz振动信号的相位和频率信息。

Phase-sensitive fat suppression steady-state free procession sequence with phase correction

Robust and fast fat suppression is a challenge in balanced steady-state free precession （SSFP） magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short scan time, phase errors, especially spatially-dependent phase shift, caused by a variety of factors may result in misplacement of fat and water voxels. In this paper, a novel phase correction algorithm was used to calibrate those phase errors during image reconstruction. This algorithm corrects phase by region growing, employing both the magnitude and the phase information of image pixels. Phantom and in vivo imagings were performed to validate the technique. As a result, excellent fat-suppressed images were acquired by using single-acquisition phase-sensitive SSFP with phase correction.

Delay enhancement patterns in apical hypertrophic cardiomyopathy by phase-sensitive inversion recovery sequence

Objective:Late gadolinium enhancement(LGE) patterns of cardiovascular magnetic resonance (CMR) relying on PSIR(phase-sensitive inversion recovery sequence) techniques had been used to determine the characteristics of LGE in apical hypertrophic cardiomyopathy(ApHCM). Methods:Forty patients pure ApHCM[age,(60.2±10.4) years,31 men]were enrolled.LGE images were acquired using PSIR,and analyzed using a 17-segment model.Summing the LGE areas in all short axis slices yielded the total volume of late enhancement,which was subsequently presented as a proportion of total LV myocardium(%LGE).Results:Mean maximal apical wall thickness was(17.9±2.3) mm,and mean left ventricular(LV) ejection fraction was(67.7±8.0)%.LGE was detected in 130 segments of 30 patients(75.0%),occupying(4.9±5.5)% of LV myocardium.LGE was mainly detected at the junction between left and right ventricles in 12(30%) and at the apex in 28(70%),although LGE-positive areas were widely distributed,and not limited to the apex.Focal LGE at the non-hypertrophic LV segments was found in some ApHCM patients,even without LGE of hypertrophied apical segments.Conclusions:LGE was frequently observed not only in the thickened apex of the heart but also in other LV segments,irrespective of the presence or absence of hypertrophy.The simple presence of LGE on CMR was not representative of adverse prognosis in this population.

Phase-Sensitive Optical Time-Domain Reflectometer Based on a 120°-Phase-Difference Michelson Interferometer

A phase-sensitive optical time domain reflectometer （φ-OTDR） based on a 120°-phase-difference Michelson in- terferometer is proposed. The Michelson interferometer with arm difference of 4m is used to test the phase difference between the Rayleigh scattering from two sections of the fiber. A new demodulation method called the inverse transmission matrix demodulation scheme is utilized to demodulate the distributed phase from the backward scattering along the long fiber, The experimental results show that the 120°-phase-difference inter- ferometer φ-OTDR can detect the phase along the 3km fiber, and the acoustic signal within the whole human hearing range of 20 Hz-20 kHz is reproduced accurately and quickly.

一种融合Φ-OTDR和MZI的PCCP断丝监测系统

设计了一种融合相位敏感型光时域反射计(Φ-OTDR)和马赫-曾德尔干涉仪(MZI)的预应力钢筋混凝土管(PCCP)断丝监测系统。通过引入优化的IQ解调算法,减少了40%以上的数据运算量。实验结果证明该系统的单端测量距离不低于20 km,频率响应不低于20 kHz,空间定位误差在±2 m以内,具备长距离定位断丝故障和分辨振动事件特征频率的能力,为PCCP的全生命周期在线结构健康监测提供了一种可靠的技术手段。

Comparison between magnitude reconstruction and phase-sensitive mR imaging in the detection of myocardial infarction

Objective:To determine the deference between phase sensitive magnetic resonance(MR) imaging and magnitude reconstruction to detect infracted myocardium.Methods:Twenty patients(16 men;4 women;mean age,56 years),experienced Q-wave myocardial infarction 2 weeks earlier were examined with a 3.0-T MR system 10 minutes after administration of 0.1 mmol/kg body weight gadobenate dimeglumine.To determine the optimal TI,a TI scout sequence was used.A segmented 2D IR true fast imaging with steady-state precession(trueFISP) sequence that produces both phase-sensitive and magnitude-reconstructed images were used at TI values of 200-600 msec(TI values were varied in 100-msec steps) and at optimal TI(mean value,330 msec).Contrast- noise ratios(CNRs) of normal and infarcted myocardium and the area of infarcted myocardium were determined.Two-tailed unpaired sample Student t test was used to compare CNRs,and area of infarction.Results:MMean CNR phase-sensitive and magnitude-reconstructed images at optimal TI(mean value,330 msec) were 6.2,and 6.1,respectively.For a TI of 200 msec,CNR values were 5.5,and 4.2,respectively;for TI of 600 msec,CNR values were 5.8 and 4.3,respectively.Area of infarcted myocardium was underestimated on magnitude-reconstruction images(P = 0.002-0.03) for short TI values(ie.,200 msec) but not on phase sensitive reconstructed when compared with IR tureFISP images obtained at optimal TI.Conclusions: LPhase-sensitive image reconstruction results in reduced need for precise choice of TI and more consistent image quality.

Fifth-order phase-sensitive detection of ultrafast polarization beats in cascade four-level system

We study the colour-locked twin-noisy-field correlation effects in the fifth-order nonlinear susceptibility of ultrafast polarization beats in a cascade four-level system. More importantly, the fifth-order phase-sensitive heterodyne detection of ultrafast polarization beats has been exploited. The fifth-order nonlinear optical response can be controlled and modified through the colour-locked correlation of twin noisy fields. Thus, this method with the phase dispersion information is a good way to measure the real and imaginary parts of the fifth-order nonlinear susceptibility.

基于KNN算法与φ-OTDR系统的高铁声屏障故障识别方法

提出了一种基于K近邻(K-nearest neighbors,KNN)算法和相位敏感光时域反射(Phase-sensitive optical time domain reflectometry,φ-OTDR)系统的高铁声屏障故障识别方法。设计了V字型光缆敷设方式,能够感知声屏障不同高度吸声板在脉动力冲击下的振动,并利用φ-OTDR系统采集振动信号。对振动信号进行多域特征提取以及K近邻分类后,可以实现对声屏障故障状态识别。实验结果表明,在复杂场景下对于故障点的识别正确率达到了90.9%。该方法为声屏障故障识别提供了一条可行的技术路线,能够减少对专业人员的依赖,对于提升高铁声屏障智能运维水平具有重要意义。

基于两级SVM的Φ-OTDR系统振动事件识别算法

相位敏感光时域反射计(Φ-OTDR)对于振动信号能够实现高灵敏度的连续分布式测量,目前的振动事件识别算法常从一个或者两个维度来提取特征,如时域或频域等,未能实现多维度大样本特征参量的融合分析;现有的算法一般采用简单的单级识别算法,结构比较简单,导致最终的模型识别准确率不高、泛化能力较差。针对上述问题,对实验采集的振动信号从时域、频域和空间域的多参量特征进行提取和融合,针对具体的振动信号识别问题,构建了一种两级支持向量机(SVM)识别算法,对振动事件进行两级分类,能够实现对相似振动事件的精确识别,识别准确率达90%以上。

基于φ-OTDR的分布式光纤声波传感系统性能改进研究

为了满足复杂的工程现场环境对相敏光时域反射仪(φ-OTDR)的各项性能指标的需求,提出基于自适应卡尔曼滤波(AKF)和频分复用(FDM)的高性能φ-OTDR,利用FDM提升系统的频响带宽,引入AKF对线性响应于外界振动的相位状态的噪声统计特性进行实时估计和修正,抑制了衰落和串扰导致的相位失真。实验结果表明,改进后φ-OTDR系统的传感线性度被有效提升,系统本底噪声降低到-83.7dB2/Hz,应变分辨率达到了0.28pε/Hz1/2。

基于Φ-OTDR的海风机与海底电缆在线状态监测方法

利用自研的Φ-OTDR系统,在福建省某海上风电场开展了演示验证,实现了对海风机机组的启动-运行-停机等不同工况下的状态分析与诊断,总结了不同工况下的振动特征及诊断依据;以及针对海底电缆的水流冲击、锚害拖拽、抵近船只航行等监测预警功能,总结了不同海缆状态下及周边环境感知目标事件特征。实测结果证明该方案能够在线监测海风机与海底电缆状态,并有效感知周围环境,为提升海上风电场运维水平提供了可靠的技术途径。

基于双向OTDR测试的通信光缆故障智能检测方法

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。