Design Considerations for Long-Haul Lightwave Systems

The following design considerations for long-haul lightwave systems are reviewed: outage and error rate requirements, terminal architecture, regenerator span design and performance specification, capacity upgrade alternatives, and broad-gauge economic factors.     

长途高速骨干网光传输系统的优化设计

为了改善长途高速骨干网光传输系统的传输性能,对其系统器件进行了优化配置,主要包括提出一种新的光放大器的配置方案,在光传送单元（OTU）中引入FEC技术。以便实现在确保低成本的条件下实现高效、高质量传输要求的目的。     

An Inexpensive Automatic Test System for Remote Supervision of Repeatered Lines

Salient features of a novel automatic fault location scheme for remote supervision of repeatered digital transmission lines is discussed. Looping back repeaters in succession by a single command on the power feed line eliminates the use of a separate supervisory cable pair. The scheme has been generalized in such a way as to facilitate its adoption to almost all type of repeaters, thus providing an inexpensive,simple supervisory scheme for a low density rural area line transmission hookups.     

High-Speed TDM–WDM Techniques for Long-Haul Submarine Optical Amplifier Systems

Optical amplifier techniques have led to the installation of large-capacity submarine systems and further capacity increases seem likely. This paper reviews the FSA submarine system, which flexibly operates at both 2.5 and 10 Gb/s and offers maximum transmission capacity of 60 Gb/s for commercial use. The system configuration as well as its characteristics and upgradability will be introduced, including measurement results on time-division-multiplexing/wavelength-division-multiplexing (TDM–WDM) transmission at bit rates of 10 and 20 Gb/s using non-return-to-zero or soliton pulses. To further increase transmission capacity, TDM–WDM techniques that permit more than 10 Gb/s signal transmission in each data channel should be developed. Thus, pulse formats, which include non-return-to-zero, return-to-zero, or soliton pulses, and dispersion allocation in transmission fibers are significant issues. We introduce and discuss our recent results from high-speed (10 to 40 Gb/s) TDM–WDM signal transmission experiments with regard to the above aspects.     

Numerical Analysis of Open-Ended Coaxial Lines

Numercal methods are applied in the analysis of coaxial structures used as sensors for in vivo permittivity studies of biological substances. The methods used for the solution of the resulting static conductor-dielectric problems are the Finite Element Method (FEM) and the Method of Moments (MOM) applied to a pair of coupled integral equations. A linear model which relates the sample permittivity to the fringing field capacitance of the sensor is discussed and values of the model parameters are calculated for different types of sensors.     

Propagation in Ferrite-Filled Coaxial Transmission Lines

The dispersion relations (/spl omega/-/spl beta/diagrams) for propagation of the quasi-TEM mode and higher-order symmetric modes in longitudinally magnetized ferrite-filled coaxial waveguide are presented. The dispersion relations for ferrite-filled coaxial cavity resonators are analyzed and presented graphically. The performance and operation of an X-band tunable ferrite filter is evaluated in light of the /spl omega/-/spl beta/diagrams     

Characteristic Impedance of Rectangular Coaxial Transmission Lines

The characteristic impedance of rectangular coaxial transmission lines can be readily and accurately computed by a simple equation when the capacitance per unit length is known. While the capacitance per unit length of the parallel sides is easily calculated, the calculation of the corner capacitance is a more difficult problem. This problem has been solved by Skiles and Higgins, using orthonormal block analysis. By using their formulas, the corner capacitances for a wide range of all variables were evaluated by means of a digital computer. The results are cataloged in graphical form.     

方同轴线内微放电效应预测

运用FDTD方法分析并计算了方同轴线内部的射频电场。根据微放电效应的基本方程对方同轴线内部的微放电阈值电平进行了预测，并和实验数据作了比较。结果表明该预测方法是有效的，能够满足工程上的应用。     

G.652光纤长途传输系统的色散补偿

针对当前国内长途传输光缆系统在扩容过程中，因光信号色散而影响传输质量的现象，结合实际工程建设，分析了光信号色散的危害及其成因，并提出了相应的解决办法及建议。     

Stratified Sampling Monte Carlo Algorithm for Efficient BER Estimation in Long-Haul Optical Transmission Systems

We propose an efficient stratified sampling (SS) algorithm for estimating the bit error rate (BER) of a digital communication system. Our algorithm efficiently exploits the observations of an approximate, but usually fast, model of the system under investigation to drive a clever Monte Carlo (MC) estimation based on SS. The proposed method is faster than standard MC even at BER in the range $10^{-3}$ to $10^{-5}$ . Moreover, it is possible to evaluate the estimated standard deviation of the measured BER, such as in an MC simulation, so that it is possible to associate a confidence to the results. We test the algorithm both in a simple optical system distorted by group velocity dispersion (GVD) and in more complex differential quadrature phase shift keying (DQPSK) systems. In the last case, we measured computational savings up to 70% compared with standard MC.      

The New Methodology for Long-Haul Time Dependent Vehicular Network

Wireless Personal Communications - This work aims to propose a new methodology for the vehicular network. In this work, long-haul transportation with time dependent is investigated. The fuzzy...     

一种基于同轴波导的异向传输线

该文提出了一种基于同轴波导的新型异向传输线,与现有基于微带电路的异向传输线相比,这种结构有更高的工作频率、损耗较低和更大的功率容量;与基于同轴波导和矩形波导的异向传输线相比,其结构更简单容易实现。等效电路与有限元仿真的结果均表明这种结构在特定的频段表现出明显的异向特性。     

The Exact Dimensions of a Family of Rectangular Coaxial Lines with Given Impedance

The potential problem associated with a capacitor bounded by concentric rectangles may be solved by conformably mapping a certain L-shaped region onto the upper half plane. In certain cases, the integral, by which the Schwarz-Christoffel transformation may be expressed, can be evaluated in terms of two elliptic integrals of the first kind. Then the odd- and even-mode impedance of the related transmission line is readily found.     

Calculation of Achievable Information Rates of Long-Haul Optical Transmission Systems Using Instanton Approach

A method for estimation of achievable information rates of high-speed optical transmission systems is proposed. This method consists of two steps: 1) approximating probability density functions for energy of pulses, which is done by the instanton approach, and 2) estimating achievable information rates by applying a method originally proposed by Arnold and Pfitser. Numerical results for a specific optical transmission system (submarine system at transmission rate 40 Gb/s) are reported     

Crosstalk Considerations for a 48 Channel PCM Repeatered Line

Extension of the 24 channelT1carrier concept to a 48 channel system requires a careful investigation of the limitations imposed by the increased crosstalk noise susceptibility of 48 channel regenerators. Results of this paper demonstrate the feasibility of dual cable and single-screened cable operation of 48 channel lines at repeater spacings comparable toT1spacing. Operation over singlecable facilities is limited by NEXT to cables with a large cross section and is further restricted to only selected conductors in such a cable. A final result establishes thatT1and 48 channel systems may operate simultaneously in facilities engineered according to 48 channel crosstalk requirements.     

Optimization of Single-Sideband DCS-RZ Format for Long-Haul 43-Gb/s/channel Ultradense WDM Systems

The optimization of the single-sideband (SSB) duobinary carrier-suppressed (DCS) return-to-zero (RZ) format for long-haul ultradense wavelength-division multiplexing (UDWDM) systems with a 43-Gb/s/channel and a channel spacing of 50 GHz is investigated numerically. It is shown that the optimized SSB-DCS-RZ format with an electrical transmitter bandwidth of 0.35 of the bit rate has about 1 dB of Q-factor improvement relative to the conventional SSB-DCS-RZ format (an electrical transmitter bandwidth of 0.25 of the bit rate) due to the reduction of noise bandwidth, smaller linear crosstalk, and better tolerance to the intra-channel fiber nonlinear effects. No substantially different UDWDM system performance is observed when varying the duty cycle of the DCS-RZ signal with optimized SSB filters settings. The UDWDM transmission performance of SSB-DCS-RZ formats is compared with the bandwidth-limited (BL)-duobinary formats. It is shown that generally, the SSB-DCS-RZ formats have poorer Q-factor and tolerance to the total residual dispersion but much higher tolerance to the in-line dispersion compensation and intra-channel nonlinear effects than the BL-duobinary formats     

An Efficient FDTD Model for Resistively Loaded Cylindrical Antennas With Coaxial Lines

A full coarse-grid based finite-difference time-domain (FDTD) model is proposed for an efficient analysis of resistively loaded cylindrical antennas driven by coaxial feed lines. In the case of the electrically thin resistive antenna, the thin-wire approximation is applied to the near fields around the antenna. The resistive antenna is equivalently represented by a series connection of piecewisely lumped resistors along the antenna axis. And the coaxial line is replaced by an equivalent source over the feed aperture of the line. Then the corresponding FDTD update equations make it possible to implement the full coarse-grid model without additional grid refinements for the antenna and the feed line. The transient reflected feed voltage and the input impedance of resistive antennas are calculated numerically and compared with those of a full fine-grid.      

任意截面形状同轴线高次模的直线法分析

本文应用直线法理论严格推导了在极坐标系统中分析任意截面形状同轴线高次模的公式。根据这些公式可求出各模式的截止波数和相应的场分布。计算结果与已有的数据的一致性，证明了本文分析的正确性。     

Validity of the Additive White Gaussian Noise Model for Quasi-Linear Long-Haul Return-to-Zero Optical Fiber Communications Systems

In this paper, we study the validity and limitations of the additive white Gaussian noise (AWGN) model in quasi-linear, long-haul, return-to-zero, direct-detection optical fiber communications systems. Our approach is to compare bit-error ratios (BERs) computed using the additive white Gaussian noise method to those obtained using standard and multicanonical Monte Carlo (MMC) simulations and to a noise-linearization method, referred to as the noise covariance matrix (NCM) method. We show that the AWGN method provides a very good approximation to the actual system BER for power levels and dispersion profiles that are used in typical modern-day quasi-linear systems. For example, the BER obtained using the AWGN method is within a factor of 4 of the actual system BER computed using MMC simulations for a realistic 10 Gb/s, 6000 km system based on dispersion-shifted fiber in which the peak signal power at the transmitter is 1 mW and the absolute residual dispersion at the receiver is less than 200 ps/nm. However, when the peak power is increased to about 4 mW, or the average map dispersion is zero and the absolute residual dispersion exceeds 200 ps/nm, the AWGN and NCM methods may simultaneously breakdown due to a combination of nonlinear signal–noise and noise–noise interactions during transmission. In addition, for a 5000 km system based on low-nonlinearity $D_+$ and $D_-$ fiber with an average map dispersion that is 4% of the dispersion variation within the map, and that operates at a peak power of 5 mW, we find that the BERs obtained using the AWGN and NCM methods are about 500 times smaller than the actual system BER computed using MMC simulations.      

Characteristics of 10-Gb/s Electroabsorption Modulator Integrated Distributed Feedback Lasers for Long-Haul Optical Transmission Systems

In this study, we review the characteristics of 10-Gb/s electroabsorption modulator integrated (EAMI) distributed feedback (DFB) lasers for long-haul optical transmission systems. The recent progress and issue of extinction ratio, chirp, and frequency response are described, which are important parameters to improve transmission performance. Except for the extinction ratio, frequency response and chirp characteristics are discussed further. The frequency response of packaged EAMI-DFB lasers has been improved using the novel impedance matching technique. The large signal chirp characteristics are calculated with varying bias voltage, facet reflectance, grating phase, and a coupling coefficient (κL) to predict the measured chirp characteristics. Finally, transmission performance (BER, eye margin, and eye opening penalty) is measured and estimated using the calculated chirp characteristics.