Systematic design of novel wide-angle low-loss symmetric Y-junctionwaveguides

To construct a low-loss and wide-branching-angle symmetric Y-junction waveguide, a novel structure is proposed. The structure consists of a pair of microprisms for precompensation and a microprism for phase-front acceleration. The structure of the Y-junction and the associated refractive indexes of microprisms are systematically derived. The simulated results using the fast Fourier transformation beam propagation method (FFT-BPM) demonstrate the performances of the proposed structure. The normalized transmitted power is more than 95% even though the branching angle is up to 200     

Novel optical single-mode asymmetric Y-branches for variable powersplitting

Single-mode asymmetric Y-branches using microprisms are proposed. With a bend prism designed by the bend phase compensation rule (bend PCR) and a pair of Y-branch prisms designed by the Y-branch PCR, the phase front mismatch at the branching point is greatly eliminated, resulting in wide-angle low-loss 3-dB asymmetric Y-branches. Furthermore, control of power-splitting ratios is fulfilled through varying the lengths of prisms for a fixed branching angle and a fixed prism index. Finally, cascades of the proposed structures are studied. It is shown that the construction of a satisfactory 1×N tree power divider based on the cascaded structures is possible     

New design method for low-loss Y-branch waveguides

We propose a new method to design low-loss Y-branch waveguides. In conventional design methods, a specific geometry of branching structure is given first, and then structural parameters describing the details of the proposed geometry (for example, location, sizes, and refractive index of microprisms or phase-adjusting elements) are determined by ray optics or other means. In this paper, we take quite a different approach. Given a complex field distribution, one complex refractive index distribution that supports it is determined uniquely, according to the scalar Helmholtz equation. Using this relation, we first make up an ideal field distribution for dividing optical waves smoothly in the branching region. Next, we calculate the refractive index distribution corresponding to the ideal field. Finally, the imaginary part of the refractive index is set to be zero and its real part is discretized into three levels from the practical viewpoint. Numerical simulations show that the present design method offers extremely low-loss Y-branch waveguides     

密集矩阵式聚光模组二次微棱镜设计与研究

针对二次聚光器结构复杂、加工工艺难度大、成本高的问题,结合实际工程应用,设计了应用于密集矩阵式聚光模组的二次微棱镜,用Solidworks建立了三维模型,借助Zemax光学模拟仿真手段,对二次微棱镜的倾角和高度等重要参数进行了优化仿真,结果表明当二次微棱镜高度为5 mm、上底面边长为7 mm、工作面倾角为67.38时,太阳能电池接收的太阳辐射能量最大,达到最大值2.466 9 W,与不带二次微棱镜接收能量1.876 0 W相比,提高了31%,该二次微棱镜对提高聚光模组效率作用显著。     

Single-mode optical Y-branching circuit using deposited silica guides (DS guides)

A new optical Y-branching circuit using embedded single-mode glass waveguides is presented. The glass waveguides were made by depositing core glass on a silica substrate after forming grooves to contain the core (DS guides). Waveguide transmission loss is 0.6 dB/cm. The loss caused at a branching point is 0.13 dB when the branching angle is 0.3°.     

An asymmetric Y-branching circuit using total reflectionfor semiconductor integrated optical circuits

A new structure for a compact optical branching circuit is proposed. An asymmetric Y-branching circuit using total reflection is fabricated on an AlGaAs/GaAs wafer. Good branching operation is observed in a single-mode branching circuit with a branching angle of 45°. The exact origins of loss in the branching circuit are also clarified     

Low radiation loss branching/combining of optical circuits using high-silica channel waveguides

A new branching/combining optical circuit structure using high-silica channel waveguides was proposed to reduce radiation loss where branching occurs. In this structure, an additional low-refractive-index layer was formed at the junction surface between the main and branching channels. The loss in a conventional circuit could be successfully reduced by over 0.4 dB in the through channel and 0.1 dB in the reflecting channel. The allowable conditions for a low-refractive-index layer were obtained through experimental and theoretical studies.     

Bandwidth Analysis and Simulation of Reliable Multicast Transport Protocols

In this paper, an analytical bandwidth evaluation of generic reliable multicast protocols is presented. Our analysis is based on a realistic system model, including data packet and control packet loss, asynchronous local clocks and imperfect scope-limited local groups. Of particular importance are two new classes with aggregated acknowledgments. In contrast to other approaches, these classes provide reliability not only in case of message loss but also in case of node failures. Finally, we have analyzed the influence of the branching factor, i.e. the size of local groups in tree-based approaches, on a protocol's performance, which is an important parameter to improve performance. Our results prove that hierarchical approaches are superior. They provide higher throughput as well as lower bandwidth consumption. However, their performance is influenced by the optimal branching factor setting. The optimal branching factor depends mainly on the probability for receiving messages from other local groups. If this probability is zero, a small branching factor leads to the best results. On the other hand, if this probability is nonzero, which is likely if TTL scoping is used, larger local groups provide better performance. Finally, we have confirmed our analysis with simulation studies of XTP, SRM, RMTP and TMTP.     

Integrated optic Y-branching waveguides with an asymmetricbranching ratio

Integrated optic Y-branching waveguides with an asymmetric branching ratio are proposed by using a novel and simple waveguide configuration. Realisation of a controllable wide branching ratio, simply by shifting the centre axes of the input taper waveguide and the branching waveguide group is clarified both theoretically and experimentally. 1×2 Y-branch splitters with an asymmetric branching ratio of 50.0~75.6%, a low excess loss of <0.2 dB and based on planar lightwave circuits are demonstrated     

一种带有锥形多模过渡区的Y分支光波导

为减小Y分支波导的分支损耗,提出在输入波导和两输出波导间引入锥形多模过渡波导.与已被用于减小Y分支波导分支损耗的矩形多模过渡波导相比,所引入的锥形多模过渡波导,不仅可以减小过渡波导的长度,还可进一步减小分支损耗.利用三维有限差分光束传播法,对具有锥形过渡波导的退火质子交换铌酸锂Y分支光波导进行了数值模拟.数值结果为该类Y分支光波导的设计和制备提供参考.     

A New Band-Splitting Filter for Guided-Millimeter-Wave Transmission Systems

A new Michelson-interferometer (MI) hybrid having a miter angle is developed for use as a millimeter-wave band-splitting filter. The construction and operating principle of the filter are described. The design method and the experimental results are also presented. This filter has low branching loss, yet keeps very wide band characteristics. For the 4W-120-GHz-frequency-range filter with 35/spl deg/ miter angle, the branching loss is 0.68-1.56dB. This is about 40 percent lower than that of the conventional MI filter. The input VSWR is less than 1.29 and the guard bandwidth is less than 250 MHz. This filter can be used for the 40-120-GHz guided-millimeter-wave transmission systems.     

Input impedance and reflection coefficient in fractal-like modelsof asymmetrically branching compliant tubes

A mathematical model is described, based on linear transmission line theory, for the computation of hydraulic input impedance spectra in complex, dichotomously branching networks similar to mammalian arterial systems. Conceptually, the networks are constructed from a discretized set of self-similar compliant tubes whose dimensions are described by an integer power law. The model allows specification of the branching geometry, i.e., the daughter-parent branch area ratio and the daughter-daughter area asymmetry ratio, as functions of vessel size. Characteristic impedances of individual vessels are described by linear theory for a fully constrained thick-walled elastic tube. Besides termination impedances and fluid density and viscosity, other model parameters included relative vessel length and phase velocity, each as a function of vessel size (elastic nonuniformity). The primary goal of the study was to examine systematically the effect of fractal branching asymmetry, both degree and location within the network, on the complex input impedance spectrum and reflection coefficient. With progressive branching asymmetry, fractal model spectra exhibit some of the features inherent in natural arterial systems such as the loss of prominent, regularly-occurring maxima and minima; the effect is most apparent at higher frequencies. Marked reduction of the reflection coefficient occurs, due to disparities in wave path length, when branching is asymmetric. Because of path length differences, branching asymmetry near the system input has a far greater effect on minimizing spectrum oscillations and reflections than downstream asymmetry. Fractal-like constructs suggest a means by which arterial trees of realistic complexity might be described, both structurally and functionally     

Novel mode scrambler for reducing mode dependence in multimode optical waveguides

A novel mode scrambler for multimode optical waveguides is proposed to stabilise branching characteristics against the mode excitation conditio. A 2 × 2 optical star coupler is fabricated using this mode scrambler, and a stable branching ratio is realised with an excess insertion loss of 2.7 dB.     

A guided-wave optical arbiter circuit

An optical waveguide circuit which can be used as an arbiter for priority allocation in data communication system is proposed. The waveguide circuit was fabricated by silica deposition and its basic performance as an arbiter was measured. The average insertion loss and the crosstalk level for a 10-port circuit was measured to be 9.8 and -26.8 dB, respectively. In obtaining a large number of fan-out on a compact substrate, it is important to provide large refractive-index difference between the core and cladding to allow for a sharp bend and to decrease the excess branching loss. The number of fan-out of about 250 is expected on a 50-mm-square substrate.     

Semicircular Waveguide-Type Diplexers Used for the Millimeter Wave Waveguide Transmission System

A semicircular waveguide-type diplexer consisting of semicircular hybrids and high-pass filters as a band-splitting filter for millimeter-wave multiplexing-demultiplexing networks has been newly developed. The construction and the operating principles of the diplexer are described; the design method and the experimental results are also discussed. The branching characteristics for a diplexer for dividing the frequency band 43.4-86.8 GHz into two equal parts have proved tolerably flat, with the resulting branching loss amounting to as small as 1.2-1.4 dB. The total length for the experimental model is 1.17 m, which is one-half to one-third shorter than the conventional Michelson interferometer-type diplexer. It is concluded that the semicircular waveguide-type diplexer can be effectively used for millimeter-wave waveguide transmission system.     

Design for Y-branch waveguides with wide angle and low loss

A novel method to design Y-branch waveguides is proposed by using total internal reflection, and the optical properties areanalyzed. The simulated results show that the optical loss values of two Y-branch waveguides with the branching angles of 12° and 30° are only 0.310 dB and 0.645 dB, respectively. Compared with conventional Y-branch waveguides, the opticalperformance of the proposed ones is well improved, which has many advantages such as wide angle, low loss, simplestructure and easy for fabrication.     

A new type of Ti-LiNbO3 integrated optical Y branch

A report on the experimental verification of the basic operation of the proposed type of integrated optical Y branch using Ti-diffused lithium niobate is presented. The advantages of this Y branch include low-branching loss, compact size, no need for extra bending or curved elements when used as a 3-dB coupler in M-Z type switches, and freedom from critical fabrication requirements. A branching loss of 0.5 dB is achieved. The necessary three-dimensional analysis of the Ti-diffused Y-branch structure is described     

Radiation loss in dielectric waveguide Y-branch structures

Volume current method is used to calculate the radiation loss of dielectric waveguide Y-branch structures. Radiation loss of a Y-branch in the power-dividing mode of operation is calculated accurately for the first time, obtaining proper zero loss in the limit of the zero branching angle. Radiation loss of a Y-branch with parallel output guides is calculated and compared to the loss of a three guide coupler-divider; the Y-branch has smaller loss. Simple analytical formulas are given for approximate loss calculation in these structures.     

Square ring laser diode with MMI coupler cavity

A square ring laser diode is designed and fabricated in which a multimode interference 3-dB coupler operates as an output coupler and a ring resonator simultaneously. This merged structure allows a shorter cavity length and a lower loss in the output branching. Lasing in the ring cavity is confirmed and the spectra are also measured.     

New Type of Y-junction Hybrid Polymer Waveguide Couplers

Optical couplers are the key components for signal distribution in optoelectronic transmitters and receivers. A new low-loss, large-angle Y-junction hybrid polymer optical coupler with an integrated microprism has been fabricated and demonstrated experimentally for use in a mixed-signal module environment. The results show that the radiation loss is small with relatively wide branching angle as compared to a conventional Y-junction coupler.