Continuous-wave backreflection measurement of polarization modedispersion

Experimental results of continuous-wave polarization mode dispersion (PMD) measurements are presented. The proposed technique is based on the backscattered signal given by the Fresnel reflection at the fiber far-end. Experimental statistical distribution of the differential group delay of the round-trip is reported. It presents a Rayleigh distribution whose mean value is simply related to the fiber mean differential group delay. Finally, the statistical distribution of the round-trip dispersion vector is found experimentally and numerically. The proposed method can be easily used for one-end measurement of PMD in installed optical cables     

Self-consistency of polarization diversity measurement of rainfall

Polarization diversity measurements of rainfall, namely the reflectivity factor, differential reflectivity, and specific differential propagation phase, vary in a constrained three-dimensional space. Algorithms are derived to quantify this self-consistency of measurements. In particular, estimation of the specific differential propagation phase shift based on reflectivity and differential reflectivity is analyzed in detail. Theoretical simulation as well as radar observations of rainfall at S (CSU-CHILL) and C (Polar 55C) bands are used to demonstrate that the range profiles of differential propagation shift can be constructed from measurements of reflectivity and differential reflectivity     

CLASSIFICATION OF MULTI-LOOK POLARIMETRIC SAR IMAGERY AND POLARIZATION CHANNEL OPTIMIZATION

In this paper, a new maximum likelihood (ML) classification algorithm is proposed to classify the multi-look polarimetric synthetic aperture radar (SAR) imagery. Experimental results with the NASA/JPL airborne L-band polarimetric SAR data demonstrate the effectiveness of the new algorithm. Furthermore, when using the algorithm in the classifications with subsets of the multi-look polarimetric SAR data, the polarization-channel optimization for the terrain type classification is implemented.     

保偏光纤拍长的测量方法

介绍了保偏光纤拍长测量的几种常用方法,就其测量原理,试验装置及优缺点分别进行了较为详细的分析和说明.并就目前多数测量方法适用于高双折射光纤的不足,介绍了一种较好的测量低双折射光纤拍长的方法.     

Long-term measurement of PMD and polarization drift in installedfibers

We report the most detailed long-term measurement of polarization mode dispersion (PMD) made to date. We measured two separate fibers under the same time period, which makes it possible to compare the drift properties of two similar fibers in the same environment. The measured Jones matrices suffers from both random and systematic errors, a generic problem which we discuss in detail and solve. The results confirmed the well-known statistical properties of the PMD-vector. Furthermore, the drift averaged over wavelength is very well (96%) correlated between the two fibers. We finally quantified the temporal drift by computing the autocorrelation function of the PMD-vector analytically, both with respect to wavelength and to drift time. The analytical theory shows good agreement with the measurements     

Two-states method for polarization dependent loss measurement

We report a two-states method for measuring polarization dependent loss (PDL) in an optical fiber system. Based on the property that the Mueller matrix governing the transmission property of any linear, time-invariant optical system with birefringence and PDL satisfies Lorentz transformation, we prove that PDL depends on the first column of the Mueller matrix. Hence only two orthogonal input polarization states are required to explicitly determine PDL. Experiment results show the agreement of our method with previously reported methods.     

基于偏振光的精密角度测量及传递技术

调制偏振光可作为方位信息的载体,实现方位角度信息沿角度矢量方向传递和精密测量,在精密计量、航空航天、军事、生物医药等领域具有广泛的应用前景.基于调制偏振光用于方位信息传递技术的实现原理,深入分析了磁旋光玻璃对传递和测量精度影响的作用机理,实现了优于1"的传递精度.介绍了利用调制偏振光进行三维方位信息传递以及精密角度测量系统的实现方案,并对主要的技术问题给出理论分析结果.     

Analysis and measurement of polarization conversion in a periodically loaded dielectric waveguide

The full-vectorial beam-propagation method with the improved finite-difference formula is applied to the analysis of a TE/TM mode converter based on an asymmetric periodic loaded waveguide. The polarization conversion behavior is measured at a microwave frequency. It is demonstrated that the calculated complete conversion length is in agreement with the experimental result.     

系统误差对分布目标极化散射测量的影响

首先统一推广了现有极化定标模型.系统地评估了极化通道幅相不平衡、天线串扰、法拉第旋转、地形坡度导致的极化角度偏转、干扰和系统环境噪声等因素对分布目标全极化散射测量的影响.在此基础上,结合应用需求对上述因素的约束条件,通过仿真得到了一些对极化合成孔径雷达系统设计和极化定标有参考价值的结论.     

Method of polarization reflection matrix measurement in the submillimeter wave range

Homodyne method of measurement of polarization reflection matrix, providing the possibility of simultaneous measurement of all four complex coefficients of polarization reflection matrix in submillimeter quasi-optical (QO) circuits is presented. Technical realizability of the method for QO waveguides of the class of "hollow dielectric wavequide" is shown.     

Accurate measurement of antenna gain and polarization at reduced distances by an extrapolation technique

A new technique is described for determining power gain and polarization of antennas at reduced range distances. It is based on a generalized three-antenna approach which, for the first time, permits absolute gain and polarization measurements to be performed without quantitative a priori knowledge of the antennas. The required data are obtained by an extrapolation technique which includes provisions for rigorously evaluating and correcting for errors due to proximity and multipath interference effects. The theoretical basis provides a convenient and powerful approach for describing and solving antenna measurement problems, and the experimental method employed illustrates the utility of this approach. Examples of measurements are included which exhibit errors in gain as small aspm0.11dB (3sigma).     

Study on monopulse angle measurement method based on virtual polarization matching

A monopulse angle measurement method for polarization array radar is studied in this paper. The receiving signal model is established and then a monopulse angle measurement method based on virtual polarization matching is proposed. To analyze the estimation performance, the Cramer-Rao Lower Bound （CRLB） of angle estimation is derived. Both theoretical analysis and simulation show that： firstly, the proposed method is superior to the traditional angle measurement methods based on the single polarization. Secondly, the performance of the new method is unrelated to the echo polarization. Thirdly, angle estimation of this method is asymptotically optimal. The results show that this method has great potential to be used in polarization array radar.     

基于相应簇回声状态网络静态分类方法

借鉴模仿哺乳动物大脑皮层分簇结构的复杂网络拓扑结构,提出一种基于相应簇储备池回声状态网络的分类方法.将时间窗函数机制引入到回声状态网络储备池的构建中,利用具体问题中需分类数据的类别数量,生成具有对应分簇数目的储备池,以期提高分类精度.基于标准数据集和模拟电路故障诊断的实验验证结果表明,本文方法与标准回声状态网络等方法相...     

A precision measurement technique for residual polarization in integrated circuit capacitors

Accurate measurement of residual polarization (charge-voltage (Q-V)hysteresis) in integrated circuit capacitors has been obtained by a simple new technique. Resolution of 4 ppm has been achieved, far better than is possible with conventional CV measurements. Polysilicon (n+) to bulk (n+) capacitors with 500 Å of thermal silicon dioxide as the dielectric exhibit no residual polarization at this level.     

Single-end polarization mode dispersion measurement usingbackreflected spectra through a linear polarizer

Routine characterization of polarization mode dispersion of single-mode fibers in installed cables requires simple and fast techniques. All standardized techniques use both fiber ends, one connected to the optical source and the other one for signal detection. Clearly, this causes several drawbacks in field tests because the two fiber ends are usually far from each other. Among standardized techniques, the fixed-polarizer method (also called wavelength scanning method) is one of the simplest to implement. In this work we present a new single-end measurement scheme based on the fixed polarizer method applied to the signal backreflected by the fiber far-end. We report analytical equations and numerical solutions that permit to calculate the mean value of the differential group delay measuring the crossings and/or extreme densities of the spectrum transmitted through a linear polarizer. We also show that the mean value of the differential group delay can be calculated using the Fourier transform of the detected signal. Finally, experimental results on cascades of single-mode step-index fibers confirm the robustness and easiness of our proposal for polarization mode dispersion measurements     

基于偏振相关损耗测量磁场的高精度方法

为提高测量精度,提出了一种利用光纤光栅测量磁场的方法.依据磁场与光纤光栅偏振相关损耗成正比的理论,运用正交共轭反射镜来消除线性双折射,以Muller矩阵为基本方法,设计磁场测量原理图.数值仿真表明,通过正交共轭反射镜可以大幅度减少测量过程中的线性双折射,从而提高磁场的测量精度.     

单模单偏振光纤基模截止波长的测量

本文给出了单模单偏振光纤基模截止波长的测量原理和测量装置,对W－型单模单偏振光纤的基模截止波长进行了测量,并将测量结果和数值计算进行了比较,它们较好的吻合一致。     

地-井时域激电拟牛顿法反演问题研究

基于地-井时域激电三维有限差分正演模拟工作,以井旁目标体方位、埋深等为待反演参数,选择极化规则形体解析式构建反演目标函数和偏导数矩阵;采用变尺度法和共轭梯度法结合正演模拟利用地井激电方位测量数据对井旁类球状极化体进行反演.结果表明：反演结果和拟合效果较好,反演方法具有一定的可行性和适用性.     

Autocorrelation function of the principal State of polarization vector for systems having PMD

The autocorrelation function (ACF) for the principal state of polarization (PSP) vector is reported. It is shown that the PSP vector ACF and the magnitude of the polarization-mode dispersion vector, i.e., the differential group delay (DGD) ACF are not independent. The PSP vector correlation bandwidth is verified to be narrower than that of the DGD.     

保偏光纤偏振耦合应力传感器的研究

作用在保偏光纤上的横向应力可以引起偏振耦合现象,通过测量耦合强度可以检测应力的位置和大小,实现应力传感.设计了应力施加装置,包括底座、手动微位移台、数显测力计、施力探头、旋转台、光纤夹持机构和受力支架.在1根直径125μm,拍长2.1 mm的保偏光纤上进行了应力大小和作用长度对偏振耦合强度影响的实验研究.结果表明作用长度为拍长一半的奇数倍时,耦合强度最大.在部分区域耦合强度和应力大小成线性关系,可应用于应力传感器中.