Mutual Coupling Between Parallel-Plate Waveguides

The radiation field and mutual coupling between two identical parallel-plate waveguides having the same axis of symmetry are investigated. Jones' method of formulation is applied and a modified Wiener-Hopf equation is obtained. Expressions for the radiated field in free space, reflected field in the exciting waveguide, and transmitted field in the coupled waveguide are obtained and the reflected and transmitted fields are expressed in terms of waveguide modes. The reflection coefficient for each mode is represented by three terms, two of which are due to reflections at the open end of the exciting waveguide and are constant along the waveguide. The third term is the contribution from the field scattered by the open end of the coupled waveguide and decays along the waveguide according to the radiation condition. Similarly, the transmission coefficient of each mode is represented by three terms, two of which decay along the coupled waveguide and the third one is constant. The radiation field is also divided into three terms. One of them is due to the radiation from the open end of the exciting waveguide and the other two are the contribution of multiple interactions between the two waveguides. Computed results for the reflection and transmission coefficients and the radiation field are shown for TE/sub 0,1/ excitation and various separation distance of the waveguides. The results for the reflection and transmission coefficients are oscillating functions of period /spl pi/, and approach gradually the well-known final values of a single excited wavegnide.     

On the cooperative MIMO communication for energy-efficient cluster-to-cluster transmission at wireless sensor network

Energy-efficient data transmission is one of the key factors for energy-efficient wireless sensor networks (WSN). Cooperative multiple input multiple output (MIMO) explores the wireless communication schemes between multiple sensors emphasizing the MIMO structure. In this paper, an energy-efficient cooperative technique is proposed for a WSN where selected numbers of sensors at the transmitting end are used to form a MIMO structure wirelessly connected with a selected number of sensors at the receiving end. The selection of nodes in the transmitting end is based on a selection function, which is a combination of channel condition, residual energy, inter-sensor distance in a cluster, and geographical location, whereas the selection in the receiving side is performed on the basis of channel condition. Data are sent by the sensors in a cluster to a data-gathering node (DGN) using a multihop transmission. We are concentrating our design on the intermediate hop, where sensors in a cluster transmit their data to the sensors in another cluster with MIMO communication. Energy models are evaluated for both correlated and uncorrelated scenarios. The delay model of the proposed cooperative MIMO is also derived. Experimental results show that the selected MIMO structure outperforms the unselected MIMO in terms of total energy consumption. They also show energy-efficient performance by around 20% over unselected MIMO when they are compared with single-input-single-output structure. Also, the proposed approach takes around 50 more rounds than the geographically selected approach before dying at distance d?>?20 m.     

Orthogonal Hybrid Waveguides: An Approach to Low Crosstalk and Wideband Photonic Crystal Intersections Design

A low crosstalk and wideband photonic crystal (PC) waveguide intersection design based on two orthogonal hybrid waveguides in a crossbar configuration is proposed. The finite-difference time-domain (FDTD) and coupled-mode theory (CMT) methods are used to simulate the hybrid waveguides of square lattice. The bandwidth (BW) and crosstalk of the intersection are investigated for various radii of the coupled cavities. It is shown that simultaneous crossing of the lightwave signals through the intersection with negligible interference is possible. The transmission of a 200-fs pulse at 1550 nm is simulated by using the FDTD method, and the transmitted pulse shows negligible crosstalk and very little distortion.     

Thermal properties of channel optical waveguides based on sol–gel materials

Temperature characteristics of various channel waveguides fabricated using the sol–gel technology are analyzed. It is shown that the limitation of transverse sizes of waveguides leads to significant variations in the temperature characteristics due to field concentration in the sol–gel material of the waveguide, which depends on the type of the channel waveguide and its parameters (geometrical sizes and refractive index of the sol–gel material). Recommendations on the selection of the type of waveguide and its parameters for specific applications in multiplexers, switches, optical cavities, etc. are presented.     

Q 波段波导环形电桥的设计与实现

本文介绍了一种采用波导来实现的环形电桥的设计与实现方法。它是在基于微带环形电桥的奇偶模分析的基 础上,用矩形波导代替微带线,实现了Q 波段的环形电桥,环路电桥的输入输出端口均为BJ400 波导。其中为了改 善输入端口的反射,在输入端口的不连续性处加入了一个销钉,销钉的尺寸由HFSS 优化仿真确定。实测结果得到, 在43-46GHz 范围内,环形电桥的反射小于-20dB,输出端口的传输系数均大于-3.4dB,隔离度大于20dB。从测量结 果可以看出,与微带线的实现方式相比,波导环形电桥具有更小的传输损耗。     

一种基于缺陷光子晶体的解复用器

在二维正方晶格光子晶体的基础上,构建了一种晶格常数渐变的变晶格结构,设置线缺陷形成主波导和多个耦合波导以及相应的耦合点缺陷(微腔),利用该缺陷态结构实现了六信道波分解复用器.采用时域有限差分法研究了微腔的谐振特性及主波导和各耦合波导的传输特性.计算结果表明:点缺陷共振模可以实现几乎连续的变化,有相近的强度,缺陷峰线宽均约为0.01μm左右;六信道的中心波长在2.667μm～2.802μm之间,信道间隔平均值小于0.025μm.     

Coupling Between Two Collinear Parallel-Plate Waveguides of Unequal Widths

The problem of coupling between two collinear parallel-plate waveguides of unequal widths is investigated using the moment methods. The exciting mode of the waveguide is assumed as the incident field and an integral equation for the induced currents is expressed in terms of the reflected, the transmitted, and the evanescent currents on the walls of the waveguides. This integral equation is solved numerically and the results for the reflections and the transmission coefficients and the radiated field are obtained. The effect of varying the coupled waveguide width and the separation distance of the waveguides is investigated.     

Analysis of a phase mismatched three waveguide coupler with an optical amplifier

A novel optical amplifier is proposed and analyzed. This device consists of three parallel waveguides and each has a slightly different propagation constant, that is, each waveguide is slightly phase mismatched and couplings among these waveguides are weak. Two adjacent waveguides are passive and the third one is active and all end facets of waveguides are antireflection coated, so that optical feedback can be eliminated and the active waveguide is a traveling wave type amplifier. Because of a phase mismatched configuration, this device can be used to tap optical signals without much power reduction in optical transmission lines. Signals coming into the device are weakly coupled to the active waveguide via the passive waveguide in between and they are amplified through the active waveguide. Characteristics of this device are studied and parameters which are required to design the device are also given as an example.     

Adaptive MIMO Transmission for Exploiting the Capacity of Spatially Correlated Channels

We consider a novel low-complexity adaptive multiple-input multiple-output (MIMO) transmission technique. The approach is based on switching between low-complexity transmission schemes, including statistical beamforming, double space-time transmit diversity, and spatial multiplexing, depending on the changing channel statistics, as a practical means of approaching the spatially correlated MIMO channel capacity. We first derive new ergodic capacity expressions for each MIMO transmission scheme in spatially correlated channels. Based on these results, we demonstrate that adaptive switching between MIMO schemes yields significant capacity gains over fixed transmission schemes. We also derive accurate analytical approximations for the optimal signal-to-noise-ratio switching thresholds, which correspond to the crossing-points of the capacity curves. These thresholds are shown to vary, depending on the spatial correlation, and are used to identify key switching parameters. Finally, we propose a practical switching algorithm that is shown to yield significant spectral efficiency improvements over nonadaptive schemes for typical channel scenarios     

氟化聚合物光谱响应平坦化阵列波导光栅的优化设计和制备

本文基于阵列波导光栅(AWG)的传输理论,利用含氟聚合物(PFS-co-GMA)共聚物材料,对17×17信道光谱响应平坦化AWG波分复用器进行了参数优化.由于在聚合物阵列波导光栅器件的制备过程中,选用了反应离子刻蚀(RIE)工艺和蒸汽回溶技术,形成的梯形截面波导芯,使AWG传输的光产生相位移,导致传输光谱移动,引起串扰...     

Numerical Solution of Coupling Between Two Collinear Parallel-Plate Waveguides

The problem of coupling between two collinear parallel-plate waveguides is investigated numerically using moment methods. The exciting mode in the waveguide is assumed as the incident field, and the integral equation for the induced current is expressed in terms of the reflected, transmitted, and evanescent currents on the waveguides. The integral equation is then solved numerically by a point-matching method and the reflection and the transmission coefficients and the radiated fields are obtained. To examine the accuracy of the results, the special case of a semi-infinite exciting waveguide coupled to a finite coupled waveguide is also considered and is solved numerically by treating the singularities of the induced currents using a transformation method. For a TE/sub 0,1/ excitation of the exciting waveguide, the results of both numerical methods are compared with the analytical results obtained previously using the Wiener-Hopf technique, and are found to be in good agreement. The methods are then used to study the effect of the coupled waveguide on the radiation field.     

一种基于过模波导的高功率8 mm微波传输系统

过模波导是一种突破传统单模波导功率容量的波导结构。在高功率微波系统中,基于过模波导的模式过渡器和模式滤波器都是传输系统的关键器件。本文讨论了这些器件的理论设计依据,并设计了一套包括过模波导、模式过渡器、模式滤波器的8 mm 高功率过模波导传输系统,其中,模式滤波器分别通过膜片和窄缝滤除高次模。并用 CST Microwave Studio建模并仿真。仿真结果表明,该过模传输系统能够有效抑制高次模带来的谐振效应,提高微波的传输效率。     

Ultra-fast all-optical full-adder based on nonlinear photonic crystal resonant cavities

In this paper, a new photonic crystal-based full-adder for the summation of three bits has been proposed. For realizing this device, three input waveguides are connected to the main waveguide. An optical power splitter is placed at the end of this waveguide. Concerning the amount of optical intensity inside this waveguide, two nonlinear resonant cavities transmit the waves toward the correct ports. When the cavities do not drop the optical waves, the splitter guides them toward the output ports. The maximum delay time of the presented structure is around 0.5 ps and shows the fastest response among the reported works. This improvement is obtained due to using the resonant cavities. The time analysis results in a maximum working frequency of 2 THz. Also, designing the structure in 93 µm² demonstrates that it is more compact than the previous works. The normalized low and high margins are obtained around 10% and 85%, respectively. So, the proposed device is capable of considering optical processing circuits.

     

Angled-Facet Spot-Size-Converter Integrated Semiconductor Optical Amplifiers Using Asymmetric Twin Waveguide Technology

The extinction ratio (defined as the difference in the optical power between 0-dB fiber-to-fiber loss and the off state level) is enhanced with the introduction of an S-bend waveguide structure using asymmetric twin waveguide techniques for a spot-size converter integrated semiconductor optical amplifier (SSC-SOA) with a polarization-insensitive offset superlattice. Angled waveguides are introduced in order to obtain low facet reflectivity without the need for antireflection coating. A curved waveguide is introduced to connect the angled and straight waveguide, minimizing their coupling loss while achieving a lateral spatial mode filter. The SSC-SOA, operating at 1.62-mum wavelength, achieves an extinction ratio up to 70 dB and a fiber-to-fiber gain of 10 dB using cleaved, flat end single-mode optical fibers.     

Gain constant of two-wave mixing in periodically poledphotorefractive crystal waveguide

A photorefractive crystal waveguide with its c-axis periodically reversed along the waveguide axis is studied to realize enhanced two-wave mixing. The gain constant of two-wave mixing in the periodically poled photorefractive waveguide is theoretically derived in terms of mode-coupling analysis. It is found that, in BaTiO₃ periodically poled waveguides, the net two-wave mixing gain constant is increased by 1.5 to 5 times over that of conventional waveguides without periodical poling because the largest electrooptic coefficient r₄₂ can be effectively used by appropriately setting the angle between the c- and z-axes. Several types of test BaTiO₃ periodically poled waveguides are successfully fabricated by using the electrical poling technique. Typical lateral dimensions of the waveguides are O.5 to 1 mm, and the lengths are several millimetres. The measured two-wave mixing gain constants of the fabricated waveguides are well predicted by the theory     

Measurement of RF Transmission Mode in ITER Relevant EC H&;CD Transmission Line

The preliminary results of mode measurement in the ITER relevant 40 m long transmission test line composed from 63.5 mm diameter corrugated waveguides and miter bends are presented. The field patterns were measured by taking temperature profiles on a paper screen placed in front of the waveguide end using an infrared imaging camera. The complex electric field at the waveguide end was retrieved from the measured temperature profiles. As a result, the transmission power includes 87% of HE₁₁ mode and 6% of LP₁₁ odd (HE₂₁+TE₀₁) mode and small ratios of other modes. The mode content had small dependence on length of the transmission line. This result indicated that the higher order mode content generated at the input of the transmission line is conserved and propagated through the transmission line. This suggests that the initial RF coupling to the waveguide is critical since it affects the launcher efficiency.     

组合形变对三角形脊波导传输特性的影响

脊波导的传输特性包括截止波长、单模带宽、衰减常数、功率容量以及特性阻抗。脊波导器件在装配使用中所产生的错位形变与边侧形变很难单独发生,因此,有必要研究错位形变、底部形变、单侧形变、双侧形变结合的组合形变。利用ANSYS建立模型与MATLAB编写有限元程序相结合的方法计算了三角形脊波导组合形变对其传输特性的影响。研究结果表明,组合形变对三角形脊波导的截止波长、单模带宽影响较小,三边形变与错位底部形变对三角形单脊波导功率容量、衰减常数及特性阻抗影响较大,研究结果将为三角形脊波导的应用提供了理论依据。     

Low-loss optical branching waveguides consisting of anisotropicmaterials

Low-loss branching waveguides of the mode-conversion type consisting of anisotropic materials are proposed, and their basic wave-guiding characteristics are studied by means of coupled-mode theory. Two mode-conversion sections are introduced on both input and output sides of a conventional symmetric branching waveguide. Each arm of the branching waveguides is assumed to be a single-mode slab waveguide except for the tapered section. A coupled-mode system of equations describing mode-conversion phenomena with respect to the transverse magnetic (TM) mode in the branching waveguides is derived from the field expansion in terms of local normal modes. A Runge-Kutta-Gill method is used to numerically solve the coupled-mode equations. It is found that the proposed branching waveguides suffer mode-conversion losses to a much lesser extent than conventional branching waveguides     

基于后焦面成像的聚合物平面波导光学参数测量仪

基于后焦面成像确定波导传播特性的基本原理,结合平面波导中的菲涅尔反射理论,设计了一种聚合物平面波导光学参数测量仪.通过MATLAB拟合处理数据实现了对样品局部折射率和厚度高精度、高空间分辨率的实时测量,平面波导厚度测量精度可以达到纳米量级,空间分辨率可达到300 nm.该测量仪结构简单、易于操作,在光学传感和细胞内生物传感领域具有很高的应用价值.     

Non-leaky coplanar (NLC) waveguides with conductor backing

In this paper, we present a structure called a non-leaky coplanar (NLC) waveguide with conductor backing. It is a multilayered structure with two possible configurations. The spectral domain approach with a complex root searching procedure is used to investigate leakage phenomena. The simulation results confirm that the leakage in conductor-backed coplanar waveguide (CBCPW) occurs in the form of wave in the parallel plate waveguide with infinite width. The results show that the leakage in the multilayered structure can be removed if the geometrical and material parameters of the structure are chosen appropriately. Experiments were carried out to investigate the transmission of these structures. It was found that the resonance in the transmission of finite-width conductor-backed coplanar waveguide (FW-CBCPW) is caused by the energy leakage from the dominant CPW mode. The resonance is eliminated in the NLC waveguides. These NLC waveguides are feasible and practical in the uniplanar MMIC design due to their planar nature