Testing LANs optically to the Gigabit Ethernet standard

Gigabit Ethernet is a third-generation technology that builds on both the original Ethernet, with its 10-Mb/s data rate, and the second-generation, 100-Mb/s Fast Ethernet. Moving data at 1 Gb/s, Gigabit Ethernet meets the demands of emerging applications like desktop videoconferencing, high-resolution graphics, and high-speed networking in general trough the use of optical fibre links. High-speed optical communications opens up a tremendous learning opportunity for many LAN designers, introducing a host of new testing issues and techniques. For those engineers accustomed to working with lower-speed electrical transmission, the different equipment and measurements required for characterizing optical transmission may at first seem intimidating. But examined step by step, they are really not all that difficult to master. A LAN designer needs nothing more than an optical spectrum analyzer and an advanced communications oscilloscope-equipped with an optical-to-electrical converter-to ensure that the light source, the transmitter, and the system comply with the optical portions of the Gigabit Ethernet standard. To be sure, additional instruments and measurements will help refine a LAN design. But with just the optical spectrum analyser, the designer can determine that the light source's spectrum is sufficiently narrow and powerful, and with the oscilloscope, he or she can examine the data signal's potential for error from noise, jitter and attenuation     

光纤控制器局域网的通讯系统分析

光纤控制器局域网发展是基于对双绞线控制器局域网存在着自身的弱点而提出改进的。现代工业通信网络中为了解决大容量、高速率、远距离数据传输问题,会逐步大量使用光纤通信。文中对光纤控制器局域网的通讯系统结构以及实现等进行分析,旨在为其工程应用探讨相关的技术支持。研究结果对合理配置光纤控制器局域网通讯系统具有重要意义。     

影响空地激光通信链路通信时段选择方案的背景光及大气湍流效应因素

对空地激光通信链路通信时段选择与背景光、大气湍流效应的关系进行了理论分析、仿真及实验研究 ,指出了空地激光通信链路通信时段选择方案一般应遵循的原则 :1)由于夜晚时段大气湍流强度较弱 ,空地激光通信可多选择夜晚时段 ;2 )晴天天气条件下 ,空地激光通信应避免在太阳光强烈的中午时段建立通信 ,建议多使用清晨和下午时段 3 )阴天天气条件下 ,背景光和大气湍流效应对空地激光通信链路的影响较小 ,因此只要链路通信光能量能满足链路功率分配指标要求 ,空地激光通信链路适合在阴天天气条件下进行     

Data services for space station Freedom

The data services that are available between the space station Freedom and the users of Freedom located on the ground are described from a user's perspective. These services consist of path service on the onboard LAN to provide minimum service and maximum throughput for telemetry, ISO protocol services on the LAN to provide robust end-to-end communications and applications services, path and bitstream services over dedicated high-rate links from payloads to communications and tracking system input ports for telemetry, audio service for two-way voice communications with the ground, and video services for two-way videoconferencing and standard video-image data. The space station will use virtual channels (VCSs) to deliver predefined data sets (packaged in a VC) to the correct destinations for data traveling in both the forward (ground-to-space) and return (space-to-ground) directions. The VC provides a means of dividing the single physical RF link into a number of smaller `virtual' links that can be reassigned as required, and also of creating a virtual link between the two end points of the VC     

The IEEE 802.16 Working Group on broadband wireless

This article describes the new initiative on broadband wireless access (BWA) that has formed Working Group 802.16 in the IEEE 802 LAN/MAN Standards Committee. The aim is to provide the reader with highlights of the IEEE 802 activities in order to enable better dissemination of these standards into marketable products as well as seek new ideas to be brought into the IEEE 802 arena. BWA systems, utilizing base stations to provide broadband data to business or homes, offer an alternative to wired “last-mile” access links using fiber, cable, or telephone lines. As illustrated, the base stations may be either terrestrial, in orbit, or mounted on airplanes or dirigibles in the stratosphere. The customer terminals can carry two-way communications for Internet access, digital video, telephony, and other services     

Trends in network media and wiring strategies: LAN life cycle cost implications

The main objective of this paper is to present this author's assessment of the impact that alternative network media and wiring strategies have on the life-cycle cost of a local area network (LAN). In terms of trends and issues related to media such as twisted-pair, optical fiber and coaxial cable and wiring strategies, the author sees the following: 1) a general feeling of confusion among many potential LAN customers, 2) for those organizations which did choose a particular media and wiring strategy such as broadband or baseband coaxial cable, an increased move toward multiple media networks which can support various communication architectures, and 3) increasing management concern for LAN life-cycle costs. These subjects are addressed further as part of this paper.     

Atmospheric optical communications systems

The increasing sophistication of optical (and infrared) components and techniques, combined with rapidly expanding communication requirements, suggests that optical systems operating partly or entirely within the atmosphere may soon represent desirable solutions to real communications problems. The design of such systems will be strongly influenced by considerations of atmospheric turbulence, molecular absorption, and aerosol scattering. The most promising alternatives are heterodyne systems operating at the 10.6 µ wavelength, and direct-detection systems at near-infrared or visible wavelengths. Feasible links include horizontal, ground-to-satellite, and satellite-to-ground (or aircraft) geometries. System requirements and atmospheric effects are reviewed. Components, signaling, and diversity techniques which will partially overcome atmospheric limitations are discussed. Specific representative systems designs are presented.     

硅芯塑管在光缆通信线路中的应用

目前，先进国家普遍采用硅芯塑管作为光缆通信干线及高速公路通信的管道。经多年实践证明，光缆通信管道化在保证通信质量、安全，提高建设施工速度，降低生产成本等诸方面都有不可比拟的优越性。     

海底光通信市场近况

跨洋海底光通信是海底光通信市场的主体,目前的跨洋海底光缆都是使用光放大器的系统,并已发展到了第3代。跨大西洋和跨太平洋的海底光通信仍为此类市场的主导,但原来海底光通信并不发达的地区如亚太、非洲和拉丁美洲近来也呈现出蓬勃发展的迹象。     

大容量中心束管式光纤带光缆的设计与制造

随着通信行业向着数字化、宽带化、智能化方向的发展,光纤网络的建设将由骨干网转向局域网与城域网,由于连接的节点较多,往往需要铺设大芯数的光纤光缆。中心束管式光纤带光缆因其集成度高、占用路由资源少、成本低等特点,将会得到广泛应用。本文就大容量中心束管式光纤带光缆的设计与制造进行探讨。     

Overview of a Broad-Band Local Area Network Protocol Architecture

The protocol architecture of a broad-band local area network (LAN) must consider a realm of issues ranging from user device requirements to the characteristics of the underlying broad-band cable medium. The primary environment for which these protocols are intended consists of a collection of multichannel broad-band local networks, connected by point-to-point links. This paper describes one example of a broad-band LAN protocol architecture, LocalNet (^TMSytek Inc.). Particular attention is paid to those design decisions and practical considerations which were prompted by the intended environment.     

一种DWM光缆传输性能自动监测系统

光缆线路是传输光信号的通道 ,是光纤通信不可分割的部分 ,但由于其本身的及外在的因素造成通信中断带来的经济损失是重大的。因此 ,有必要建立一个可实现实时、在线自动监测光缆传输性能的监测系统。在介绍一种光缆监测系统的工作原理、硬件构成及基本功能的同时给出一个检测的具体实例     

Terabit-per-Second Satellite Links: a Path Toward Ubiquitous Terahertz Communication

Due to the demand for high-speed wireless communications, carrier frequencies have increased in the search for both available and wider bands. The millimeter-wave and terahertz bands (0.1–3 THz) are commonly believed to be impractical for all but short-range links due to severe attenuation by atmospheric water vapor. However, the field of submillimeter radio astronomy has demonstrated that this can be effectively mitigated by the construction of large aperture telescopes in very dry high-altitude locations, such as the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean Andes. Modeling has shown that Earth-satellite links in excess of 1 Tb per second can be achieved with a system patterned off observatories, since the loss of a satellite link from a dry location equals a sea-level path of only several kilometers. Despite advantages over optical satellite links, THz links have not been an area of active study. We review the technology and science necessary to develop a terabit-per-second THz satellite link and argue that a satellite link offers a good first step toward the development of ubiquitous THz communications.     

门类齐全 优势尽显

凯乐依托规模宏大的产业优势。为客户提供具有国际品质的常规光纤光缆、带状光缆、电力光缆、室内光缆、碟形光缆、数据电缆六大系列近千个品种规格的产品以及优质的工程设计施工服务。在光通信应用领域获得广大客户的赞誉。我们将以此为起点。继续为建立强势品牌而全力以赴。     

各种激光星间链路特点分析

通过对不同激光星间链路特点的分析,找出应用于不同链路的空间光通信系统研制中所面临的主要问题,这有利于今后空间光通信研究的进展。     

Architectures for broadband residential IP services over CATVnetworks

The current state of the art in digital broadband access technologies to support emerging telecommunications services makes imminent the introduction of interactive broadband services-including data, video and the Internet-into the residential market. Over the last few years, much attention has been paid to the development of media access control protocols for cable TV networks that will allow the immediate support of broadband data services as the first step toward enhanced communications services for residential users. We review some of the architectural options that must be carefully considered in order to deliver Internet protocol (IP) services to such users in an efficient yet flexible manner. Future residential cable data services are expected to deliver Internet access, work-at-home applications, small business access, local area network LAN-LAN interconnect, and LAN emulation services over cable (CATV) networks     

基于浮空平台的星地激光中继通信系统设计

针对星地激光通信受大气环境影响较大,无法全天候工作的难题,可考虑在18~22 km的平流层高度部署星地激光中继通信系统。其中卫星与平流层中继系统间采用激光通信,平流层中继系统与地面间采用大容量毫米波通信,基本消除大气环境(云、雨、雾、大气湍流等)对激光通信的影响,提高星地激光馈电链路可用度。受限于平流层平台成熟度不足,需首先开展基于成熟浮空平台的星地激光中继通信系统研究,先期对缓慢移动浮空平台搭载激光通信载荷与卫星间链路对准,激光通信载荷在浮空平台顶部柔性表面安装可行性等关键技术进行验证,为后续在平流层高度部署临近空间信息网络提供技术支撑。     

中国光纤通信网的发展及市场

９０年代以来,中国电信事业发展迅速,成就卓然。文中阐述了光缆建设,光缆通信设备建设,光纤传输网体系及全光网发展的前景,并对光缆,光纤,ＳＤＨ设备及光连接器等市场进行了估测。     

光纤综合业务局域网

本文扼要地介绍了把光通信技术和计算机技术组合应用,以光纤为传输介质,组成一个以一根光纤同时传输图象信息、话音信息、文字真迹信息和数据信息等不同业务的综合业务局域网。并叙述了网络的拓扑形式、功能、用途及光端机的构成,计算机的作用等。     

All light now-fibre amplifiers and their impact on telecoms

A large proportion of the UK trunk communications for data and telephony needs are now met by single-mode optical fibre cable systems. Network planners need to increase the capacity of optical systems but this is becoming increasingly difficult. The preferred way to increase the distance over which an optical cable can operate is to place optical amplifiers in the line. The author looks at how optical amplifiers can be improved to make this idea feasible