光纤数字用户环路系统

简要介绍了国际上光纤数字用户环路的发展概况及我们新近研究成功的光纤数字用户环路系统的原理、特点和功能     

Rural Subscriber Physical Loops

This paper briefly traces the development of physical subscriber loop design in the Rural Electrification Administration (REA) Program from 1949 to the present. Development of equipment for overcoming in the most economical manner the signaling and transmission problems encountered with long subscriber loops is also discussed. This includes loading systems for wider bandwidth, better structural return loss, less bridging effects with multiparty lines; loop extenders in place of costly long-line adapters (LLA's); lower cost voice-frequency repeaters (VFR's) and switching methods such as Common-Mode Operation (CMO) where less equipment is required. Discussion of the problems still encountered with transmission and signaling on rural subscriber loop is presented with ideas for solution. Development of VFR equipment with automatic gain control for use in CMO or Common-Control Central offices would permit designing to common circuit net loss and minimize contrast between circuits. Extension of signaling limits of central office equipment (COE) now being developed could eliminate the need for external loop extension equipment on better than 90 percent of rural subscriber loops. Development of a telephone instrument requiring less dc line current would eliminate the need for elevated line voltages.     

光纤用户接入网的可靠性研究

提出了研究光纤用户接入网可靠性的一般方法,探讨了光纤用户接入网的连通性,由网络生存性的角度提出了适用于光纤用户接入网的组网与保护方式。     

Millimeter Wave Subscriber Loops

Advantages and drawbacks of using millimeter waves in the telephone and data subscriber distribution network are listed. Fields in which it seems attractive to use millimeter wave loops are examined. For such applications, cost and reliability constraints led to the design of very simple systems. Two systems will soon be introduced into the French subscriber plant. The first one will be commissioned in 1983 to connect groups of remote subscribers, working at 31 GHz, using a homodyne millimetric front end. The second one, still under experiment, is designed for the connection of subscribers of the integrated service communication network; working at 23 GHz, it uses time-division multiplexing to assume duplex operation. The most drastic constraint when setting up such systems is the line-of-sight requirement. Investigations of that problem, using computer-aided coverage map plotting are discussed.     

Optical Fiber Multiservice Subscriber Connection System: SAFO

New services using moving pictures will be rapidly increasing within a few years. In a first analysis, they can be classified into three main categories: one-way broadcasted services; one-way video request services; and two-way interactive services. An important issue in their success is the cost of furnishing them. A SAFO project was undertaken to examine such service offerings, utilizing optical fiber and digital technologies. This paper describes the progress made to date by SAFO.     

Residential Fiber Optic Subscriber Loops: Information Pipeline or Technology Pipedream?

Fiber optic systems are now being considered for the "last mile" of the telecommunications network, the distribution portion of the subscriber loop. Early promoters have emphasized the enormous potential of fiber as an information pipeline. They view fiber as the key to revolutionizing the way in which we receive and interact with data in the developing information society. The investment of both technical and economic resources required to develop and deploy fiber optic systems for residential subscriber loops, however, will demand real economic returns. This will dictate new approaches to both the technology and the business strategies that strive to bring the system costs in line with the value of the information being carried. These approaches must also recognize the competitive service environment that is developing in the area of local distribution. This paper considers some of the major issues currently affecting the development of subscriber loop applications for fiber optics and their impact on technical and market requirements.     

Integrated Full-Digital U-Interface Circuit for ISDN Subscriber Loops

Reasons for using the echo-cancellation (EC) technique for full-duplex two-wire transmission of ISDN signals are given. Analysis of the performances achievable with different codes, such as 3B/2T, MMS43, partial response class 4 (PR4), and diphase, justifies the final selection of MMS43. A full-digital integrated U-interface circuit with MMS43 code and with Barker codeword synchronization is described. First laboratory test results are presented.     

Timing Recovery in Digital Subscriber Loops

Tradeoffs in the design of the timing recovery functions in a subscriber loop receiver are analyzed. The techniques considered are applicable to both the echo cancellation (EC) and time compression multiplexing (TCM) methods of full duplex transmission. Emphasis is on those techniques that lend themselves to implementation in MOSLSI technology, where the objective requirement is that timing recovery be implemented on a sampled-data signal (with the minimum possible sampling rate where EC is used). The wave difference method (WDM) for timing recovery appears to be the best candidate. A detailed study of its performance is carried out analytically and by computer simulation for the case of binary and alternate mark-inversion (AMI) line coding. A closed form expression describing the binary jitter performance of the WDM and its continuous time counterpart, the spectral line technique, is used to compare the two techniques. Analytical and simulation results for recovered phase and jitter are presented for various cable pulse responses carefully chosen to represent worst-case or nearly worst-case conditions. Two methods for including frequency detection in the WDM, the quadricorrelator and the rotational detector, are also simulated.     

高比特率数字用户环路

本文在介绍ＨＤＳＬ（高比特率数字用户环路）技术产生的背景基础上，着重论述了目前ＨＤＳＬ系统所采用的主要技术及其特点，概述了现行有关标准及相应产品。     

用户环路防雷问题新探讨

通过对用户环路系统，主要是交换机用户板和总配线架（ＭＤＦ）存在的防雷问题进行了分析，特别针对交换、电源设备、ＭＤＦ地线上雷电压降问题所带来的危害做了详细的理论分析和实验比较，并提出了几种改善地线压降的新方法，为进一步搞好电信网机房和设备规划设计和用户环路的防雷提供了新的思路。     

Design Philosophy and Hardware Implementation for Digital Subscriber Loops

This paper presents various requirements and configurations in the information network system (INS) NTT's version of the integrated services digital network (ISDN)- such as field trials, and technologies and equipment design of the digital subscriber loop using balanced wire pairs. The main aspects characterizing digital subscriber loops, are a customer access structure, a digital transmission system on existing subscriber loops, and customer interface. A configuration of two-wire digital subscriber loops with two customer access channels, which is adopted in the field trials, will be described. The time-shared two-wire digital transmission and power feeding methods on subscriber loops are discussed. The common mode rejection ratio (CMRR) is discussed in detail, since CMRR is one of the main factors which affects the transmission ability of balanced wire pairs. A proposed self-clocked four-wire customer interface utilizes time division multiplexing technique. The digital subscriber loop operates on a call-by-call basis for link establishment to avoid excessive power dissipations as well as to avoid impairments caused by crosstalk from other lines within a cable. Its design objectives and implementation are also discussed.     

Large-Scale Integration of Hybrid-Method Digital Subscriber Loops

This paper reports on studies concerning the feasibility of large-scale integrated realization of the circuits needed to provide hybrid-mode full-duplex digital transmission at 80 kbits/s or higher rates over standard local telephone loops. Alternative means of achieving the required 60 dB or so of echo cancellation have been studied in detail. The conclusion is that a combination of analog and digital circuit techniques permit practical MOSLSI realization of the complete modem, including filters, echo canceller, timing recovery, and A/D and D/A converters, without need for external circuit elements, trimming, or adjustments. The preferred system configuration has been evaluated by means of analysis, simulation, and laboratory and field measurements. A complete full duplex system, including an experimental NMOS integrated circuit echo canceller, was built and tested. Measurements showed a bit error rate lower thanl0^{-8}with line attenuation up to 40 dB, operating at 80 kbits/s. We conclude that a fully integrated MOSLSI ciruit to implement all functions for a hybrid-mode digital local loop is entirely feasible.     

Rural Subscriber Loops via Carrier and Radio

Ever since carrier was developed for trunk usage, carrier for subscriber use, either over wire or radio, has been considered as a means for providing telephone service in rural areas. Starting with the Bell System development of its"M"type power line carrier, there have been 34 years of progress and subscriber carrier is now a reality. It is now beginning to become widely accepted in the telephone industry. Every year improvements in the state of the art are made. There is little doubt today that more and more subscriber carrier on wire lines and radio will be used in future years. This concise paper includes the history of the development of subscriber carrier and radio in the Telephone Program of the Rural Electrification Administration (REA). Also, the authors attempt a prognosis of what will happen in the next ten years (or longer). Suggestions are made for improvements still deemed necessary in equipment of this type.     

农村光纤用户网的规划建设

阐述了农村用户光缆网规划设计和进村用户线路方式选择的原则,及光缆芯数的取定等。     

用户环路光纤网结构的探讨

本文对国外在实施用户环路光纤化的过程，如何结构具体条件，安排经济合理的网结构作了简要概述。     

基于光纤延时环路的单脉冲接收机

针对国外学者提出的基于光纤延时环路的高分辨多普勒接收机,深入分析了利用光学延迟环路复制脉冲串的信号检测方法。并在此基础上分析了两种可能的应用形式:单脉冲多普勒检测和单脉冲自相关检测,并为两种方法提供了单脉冲接收机的基本结构和试验参数。研究表明,基于光纤环路延时的单脉冲处理,本质上仍是一种通过光学拉长的方法实现了单脉冲的高速采样。     

Timing Recovery in Digital Subscriber Loops Using Baud-Rate Sampling

Sampled-data techniques are the most practical means of obtaining the necessary signal processing functions for timing recovery in the VLSI implementation of a digital subscriber loop transceiver. The sampled-data timing recovery techniques described in this paper are applicable to both echo cancellation and time-compression multiplexing systems. Timing recovery using baud-rate sampling in conjunction with a special pulse-shaping and timing function fulfills all the objectives for timing recovery in this application. It recovers a timing phase that has minimum precursor intersymbol interference, and makes possible the combination of decision feedback equalizer and echo canceler, reducing the convergence time and increasing the step size. The pulse-shaping function can be performed either in the transmitter by means of digital coding, or in the receiver by means of analog filtering. In the latter case, the transmitted pulse is compatible with more conventional approaches. The proposed partial-response line coding, a special form of AMI coding, is less susceptible to line impairments if detected as a two-level signal. Performance by analysis, simulation, and experimental measurements is reported on a variety of cable configurations, some including bridged taps. Analysis of jitter performance leads to design techniques for reducing the jitter magnitude.     

Economic Aspects of Multiservice Subscriber Loops in Telematics Networks

Since 1975, and in cooperation with the French Telecommunications Authority, we have been conducting field trials and feasibility studies to determine the capability of existing copper loop plant to support telematics services. This paper presents some of the economic information that has come out of our program. The economic analysis proceeds from a study of the technical options most likely to prove cost-effective in the foreseeable future. We present a method for comparing costs for telecommunications plant between subscriber premises and the central office of a multichannel, multiservice telematics network. The application of our method, to the possible technical solutions in any given case, leads to a series of conclusions Which could be valid for the coming stages of telematics network development.     

OSTS-2000用户光纤接入系统简介及其应用

湖北省邮电管理局下属的三高通信技术发展总公司与美国传输技术公司(TTS)于1994年合资组建湖北省三高百利恒通讯设备有限公司,其引进的光纤用户接入网系统(OSTS-2000)已在武汉、宜昌、襄樊等地开通使用,网上运行十余万线.为了更好地规划和应用该接入网系统,现将该系统的组成、特点及应用作一简单介绍.     

对天津市话光纤用户接入网存在问题的分析

结合天津市话光纤用户接入网的现状及存在的问题,讨论了设置光纤用户交接点的重要性和必要性,对光纤用户交接点的容量、设置方式等提出了建议。