Highly efficient full-vectorial integral equation solution for the bound, leaky, and complex modes of dielectric waveguides

A full-vectorial contour integral equation analysis of the natural modes of dielectric waveguides (DW) of arbitrary cross section is presented. The Galerkin method, together with the Analytical Regularization procedure, is applied to discretizing and solving the eigenvalue problem. This ensures the fast convergence and superior accuracy of the numerical algorithms. The waveguide cross section is characterized by a parametrical curve defining its contour, with a limited curvature at each point. This avoids the singularity points at corner regions and provides accurate results, even for waveguides with virtually sharp corners. Both fundamental and higher order mode propagation characteristics are studied in the bound, leaky, and complex regimes. Numerical results consistent with other theories and experimental data are presented for a wide range of practical dielectric waveguides that demonstrate the efficiency, accuracy, and versatility of the method developed. Finally, the technique is applied to model a fused fiber coupler.     

基于模态技术和Q-U曲线的一种电压稳定性指标

结合电力系统自身的特点和要求,利用稳态运行情况下电力系统中的信息,采用模态分析技术和CPF法得出关键节点的Q-U曲线和临界电压。并在此基础上,利用一个新的电压稳定性指标(U/Ucr)2,来分析故障情况下系统的电压稳定性。用IEEE39母线系统进行了仿真计算,结果表明该方法计算速度快,准确性好,适用于在线电压稳定性分析。     

基于模态技术和Q-U曲线的一种电压稳定性指标

结合电力系统自身的特点和要求,利用稳态运行情况下电力系统中的信息,采用模态分析技术和CPF法得出关键节点的Q-U曲线和临界电压.并在此基础上,利用一个新的电压稳定性指标(U/Ucr)2,来分析故障情况下系统的电压稳定性.用IEEE39母线系统进行了仿真计算,结果表明该方法计算速度快,准确性好,适用于在线电压稳定性分析.     

Mode coupling analysis for the design of refractive ion exchangeintegrated optical components

Refractive integrated optical planar components such as prisms and lenses, consist of alternating regions of high- and low-index planar waveguides. Boundary transmission losses depend on the coupling efficiency between the fundamental modes in the two regions. Hence, a choice of appropriate parameters to achieve maximum coupling efficiency is an important design criterion of these components. We propose the use of the Ritz-Galerkin (RG) procedure to characterize the modal fields in planar graded index waveguides for obtaining coupling efficiency and, hence, the optimal design features. The procedure is “exact” and simple analytical expressions have been obtained for coupling efficiency. Further, coupling to higher order modes can also be obtained to estimate the background noise in component design when parameters deviate from the optimum. To confirm the convergence, results have been compared with the exact numerical procedure based on the multilayer staircase approximation. Various variational procedures limited to the fundamental mode coupling efficiency calculations are also summarized in this paper along with a discussion on their accuracies     

Self-alignment of optical fibers with optical quality end-polishedsilicon rib waveguides using wet chemical micromachining techniques

This paper presents a new cost-effective method for self-aligning optical fibers on silicon platforms and for achieving optical quality end-polished silicon-on-insulator (SOI) rib waveguide devices using wet chemical micromachining techniques. Through accurate alignment to the (011) plane of the (100) device layer of a SOI wafer, rib waveguide devices with self-alignment features are fabricated with the ends of each waveguide wet etched and concurrently polished providing an optical quality facet or fiber-to-waveguide interface. Eliminating the need to saw cut and then mechanically polish the ends of fabricated devices, the overall fabrication process is simplified whilst also providing an integrated optic fiber alignment capability at the ends of the fabricated waveguide devices with an alignment accuracy limited by fiber size tolerance. Experimental measurements were carried out to verify the optical quality of the waveguide facets formed using this new technique which proved excess facet losses of practically unmeasurable quantities     

A comparison of scalar singular finite elements applied to the analysis of homogeneous waveguides with sharp edges

When we solve the wave equation by the finite element method, the order of convergence and the accuracy of the solution are reduced by the presence of sharp edges. The employment of singular elements improves the solution and allows us to reduce the cost of computation. In this paper, three types of scalar singular finite elements with the capacity to handle singularities in the derivative, and which have previously been applied to mechanical problems, are examined, together with standard elements, in the context of homogeneous waveguide analysis. We solve two examples of homogeneous waveguides showing the different behaviour of the singular elements and obtaining information on the order of convergence and the approximation of the gradient of the unknown function. © 1997 John Wiley & Sons, Ltd.     

Propagation and radiation field characteristics of nanometer electromagnetic waves in x‐ray dielectric waveguides with random media

X‐rays in the nanometer electromagnetic region are useful for nanospace fabrication, information and high‐energy transmission and control techniques of angstrom‐size structures in biomedical sciences and technology. In this paper, the electromagnetic fields in X‐ray gradient fiber with random refractive index media are studied. Statistical mode conversion of beam propagation, beam broadening, and beam center are investigated by the stochastic process theory of electromagnetic fields. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(3): 53–61, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.10002/eej.1160     

A GSM analysis of E‐plane waveguide junctions filled with piecewise homogeneous dielectric

A specific generalized scattering matrix (GSM) approach to the analysis of a piecewise homogeneous E‐plane waveguide junction with plane interfaces is presented. The object is cascaded into homogeneously filled regions, whose GSMs are found in solving two uncoupled scalar problems related to longitudinal section electric and magnetic modes, and interfaces responsible for interaction of the said modes. The GSMs of irregular constituents are determined with the help of triangular blocks. Scattering parameters of the last ones are obtained by means of the domain‐product technique. The approach was successfully verified via test problems and was applied to the analysis of scattering of the TE₁₀ mode by an E‐plane slant interface between two dielectric media. Copyright © 2011 John Wiley & Sons, Ltd.     

基于模态分析的运动负荷牵引电网谐波谐振分析

为了防止牵引网谐波谐振发生时产生的系统过电压,须获得准确的谐波谐振频率及位置,从而消除运动负荷谐波谐振对牵引网的影响.利用模态分析法,对牵引网络节点导纳矩阵的特征根进行分析,从而得出运动负荷牵引电网谐波谐振的产生与频率及机车运行位置的关系.仿真分析所得谐波谐振与频谱分析的比较结果证明此方法正确.理论分析及实际应用均证明该方法是进行运动负荷牵引网谐波分析的有效工具.     

A rigorous comparative analysis of directional couplers and multimode Interferometers based on ridge waveguides

We present a rigorous comparison of the unique characteristics of directional couplers and multimode interferometers based on the unique properties of high-index contrast ridge waveguides. The two devices are intimately related as the multimode interference (MMI) is derived from the directional couplers (DCs). We show for the first time the continuous evolution from the two-mode coupling characteristic of DC to the multimode mixing and interference characteristic of MMI, as the DC is structurally transformed into the MMI. We also show that DC can be designed to have the MMI features of compactness and polarization-insensitivity, two traits that reflect their shared lineage. The performance of MMI and DC are compared in terms of coupling length, polarization dependence, crosstalk, excess loss, and fabrication tolerances. We show that the DC, as long as it is designed to have nearly the same coupling length for transverse electric and transverse magnetic, can potentially have better performance than the MMI in terms of crosstalk and polarization sensitivity. Such a DC, however, requires careful control of many design parameters, while the MMI design is more robust and involves fewer design variables. Finally, the effect of higher-order modes and mode filtering are also considered.     

A new modal analysis theory for multiconductor nonuniform transmission-line structures: application to the analysis of line junctions

This paper is the second part of a two-paper set concerning a generalized modal analysis approach to the study of multiconductor nonuniform transmission-line structures. In the first part, a very detailed theoretical analysis was developed aimed at establishing the foundations of the method. Here, numerical results are presented for the purpose of illustrating the various steps involved in the application of the new modal technique. To demonstrate the effectiveness of this new analysis method an example of a nonuniform structure, comprising the junction of two chain-connected power lines with different cross sections, is considered. The frequency-dependent propagation properties of such a structure are evaluated, the computation results revealing that important resonance phenomena take place at certain critical frequencies.     

Numerical analysis of electron optical system with microchannel plate

This paper describes a numerical development of image converters and intensifiers which incorporate an inverting electron optical system (EOS) and a microchannel plate (MCP) as an amplifier. The numerical design of the system includes calculation of the electrostatic field in the device, trajectories of electrons emitted from a photocathode, and determination of the modulation-transfer-function (MTF) which gives the objective estimation for the image quality.     

SSOR preconditioned GMRES for the FEM analysis of waveguide discontinuities with anisotropic dielectric

The anisotropic media and active properties of the perfectly matched layer (PML) absorbers significantly deteriorate the finite element method (FEM) system condition and as a result, convergence of the iterative solver is substantially slowed down. To address this issue, the symmetric successive over‐relaxation (SSOR) preconditioning scheme is applied to the generalized minimal residual (GMRES) for solving a large sparse and non‐symmetric system of linear equations resulting from the analysis of ferrite waveguide device by use of edge‐based FEM. Consequently, this preconditioned GMRES (PGMRES) approach can reach convergence ten times faster than GMRES for the typical structures. Copyright © 2004 John Wiley & Sons, Ltd.     

Determination of single mode condition in dielectric rib waveguide with large cross section by finite element analysis

The single mode condition in large cross section rib waveguides is of great interest because almost every kind of active and passive integrated optoelectronic device or sensor is designed to sustain only the fundamental mode of propagation for better matching with optical fibers. In this paper we present a criterion to determine the single mode condition for a large cross section rib waveguides, by comparison between the numerical solutions found with Neumann boundary conditions and Dirichlet boundaries conditions applied when solving the eigenvalues problem.     

A novel fuzzy index for steady state voltage stability analysis and identification of critical busbars

In this paper, a novel fuzzy index is proposed for the prediction of steady state voltage stability conditions in transmission networks. The uncertainties in the input parameters are efficiently modeled in terms of fuzzy sets by assigning trapezoidal and triangular membership functions. The results include fuzzy load flow solutions for the base case and critical conditions with and without contingencies. The proposed fuzzy voltage stability index clearly indicates the location and status of critical busbars. Case studies have been conducted on standard test systems (IEEE 14-bus, 30-bus, and 57-bus) with proper validation of the results.     

基于Nuttall窗三谱线插值的介损角测量方法

采用FFT谐波分析方法进行介质损耗角测量时,由于非同步采样会导致频谱泄露和栅栏效应,给介质损失角测量带来较大误差。为提高介损测量精度,文中提出基于Nuttall窗的三谱线插值介损测量方法。通过加Nuttall窗进行FFT得到离散序列,由三谱线插值进行频谱校正得到电压电流基波相位,根据两者相位差来计算介质损耗角。在基波频率波动、三次谐波含量变化、白噪音存在和采样点数变化的情况下测量介损角。仿真分析结果表明,Nuttall窗具有良好的旁瓣性能,能更好抑制频谱泄露,减小测量误差,所提方法测量介质损耗角时具有较高计算精度。     

A finite-element analysis of the electrostatic force on a uniformlycharged dielectric sphere resting on a dielectric-coated electrode in adetaching electric field

In the electrophotographic process, charged toner particles are transferred from one surface to another with an electric field. To enable electric field transfer of toner, the externally applied field strength must be greater than a threshold value, so that the Coulomb force can overcome the toner adhesion force at the supporting surface. In this paper, the threshold field strength to detach a charged dielectric particle is determined efficiently by using the Galerkin finite-element method to simultaneously solve the Laplace equation for the field distribution and an overall constraint equation for the force balance. This computational method also enables calculation of the electrostatic adhesion force and is applicable to various particle-electrode configurations. For illustrative purposes, however, we consider the axisymmetric problem of electric field detachment of a dielectric sphere with uniform surface charge resting on a planar dielectric-coated electrode. The analysis is particularly focused on the dependence of the electrostatic force upon the dielectric overcoating thickness and spacing between parallel plate electrodes. The electrostatic force on a uniformly charged particle in contact with a surface is found to be influenced significantly by the thickness of dielectric overcoating and the spacing between electrodes when either becomes less than five times the particle radius     

A new composite index of reliability of supply in the industrial systems with distributed generation

Distributed generators (DGs) integrated into distribution networks could affect the host network in number of ways. In this paper an assessment of the impact of the DG continuously operated, which output behavior is non-stochastic, on the reliability of supply in the industrial networks, is performed. A set of new indices representing impact of DG on the interruption frequency, interruption duration and expected energy not supplied to every single customer, is introduced. In addition, a new composite index compiling the impacts of DG on the overall reliability of supply, including interruption frequency, interruption duration and expected energy not supplied, is proposed. Results obtained from several case studies using real-life industrial network are presented and discussed.     

A simulation-based analysis of motor unit number index (MUNIX) technique using motoneuron pool and surface electromyogram models

Motor unit number index (MUNIX) measurement has recently achieved increasing attention as a tool to evaluate the progression of motoneuron diseases. In our current study, the sensitivity of the MUNIX technique to changes in motoneuron and muscle properties was explored by a simulation approach utilizing variations on published motoneuron pool and surface electromyogram (EMG) models. Our simulation results indicate that, when keeping motoneuron pool and muscle parameters unchanged and varying the input motor unit numbers to the model, then MUNIX estimates can appropriately characterize changes in motor unit numbers. Such MUNIX estimates are not sensitive to different motor unit recruitment and rate coding strategies used in the model. Furthermore, alterations in motor unit control properties do not have a significant effect on the MUNIX estimates. Neither adjustment of the motor unit recruitment range nor reduction of the motor unit firing rates jeopardizes the MUNIX estimates. The MUNIX estimates closely correlate with the maximum M-wave amplitude. However, if we reduce the amplitude of each motor unit action potential rather than simply reduce motor unit number, then MUNIX estimates substantially underestimate the motor unit numbers in the muscle. These findings suggest that the current MUNIX definition is most suitable for motoneuron diseases that demonstrate secondary evidence of muscle fiber reinnervation. In this regard, when MUNIX is applied, it is of much importance to examine a parallel measurement of motor unit size index (MUSIX), defined as the ratio of the maximum M-wave amplitude to the MUNIX. However, there are potential limitations in the application of the MUNIX methods in atrophied muscle, where it is unclear whether the atrophy is accompanied by loss of motor units or loss of muscle fiber size.