A Field Trial of Fiber Optic Subscriber Loop Systems Utilizing Wavelength-Division Multiplexers

Future subscriber loops will provide various services including broad-band video. Fiber optic technology is the key for introducing these services. The Electrical Communication Laboratories (ECL) of Nippon Telegraph and Telephone Public Corporation (NTT) have been promoting research and development on basic technology of fiber optic subscriber loops, and studying the ways to use fiber optic subscriber loops for new services. As one of the programs, a field trial of fiber optic subscriber loops was planned and conducted in the Yokosuka area from April 1980 until May 1981. This paper first describes fiber optic transmission technologies for subscriber loops. Then, the system configuration and experimental results of the Yokosuka field trial are presented.     

Digital optical CATV system using hubbed distribution architecture

A hubbed distribution architecture based on a bus-star configuration, three-level single single-mode fiber transmission using M-TPC line code, and high-speed IC technology is proposed. The architecture is cost-effective and compact. It is well suited to metropolitan area CATV systems and would allow a gradual transition to a broadband ISDN (integrated-services digital network) subscriber loop in the future. The proposed architecture is applied to a digital optical CATV system prototype. The equipment making up this system consists of a transmitter, hubs including video selectors, and subscriber unit. Two video channels are selected for each subscriber from eight video channels at hub stations. The transmission speed is 900 Mb/s, three-level for the trunk line and 200 Mb/s, three-level for each subscriber loop. Very compact and low-cost equipment is realized by using recently developed high-speed ICs. Experimental results show that the system satisfies requirements and that its commercial application is feasible     

A Review of Broad-Band Fiber System Activity in Japan

In the future information society, various kinds of services will be required in offices, factories, homes, and communities. Fiber optic broad-band systems will play the most important role in the integrated services networks that will provide such services. This paper reviews field trials of fiber optic broad-band systems in Japan, focusing on subscriber loop system technology.     

An evolvable ATM-based video network design supporting multipleaccess network technologies

This article describes an overall video network architecture with primary focus on the ATM subnetwork. The ATM subnetwork provides efficient switching capability for providing constant bit rate and variable bit rate video communication services. The ATM subnetwork can support multiple access networks like hybrid fiber coax (HFC), asymmetric digital subscriber line (ADSL), and fiber to the curb (FTTC). A broadband network controller is presented as the external controller for the ATM subnetwork which performs the functions of the session/network manager and the ATM-based connection management. The initial deployment of video is likely to be permanent virtual connection (PVC)-based, so a dynamic PVC-based scenario is described. The ATM switch architecture presented here has been optimized to support video applications. An evolution to the switched virtual connection environment and support of multiple services over the ATM subnetwork is also addressed. Traffic management schemes are discussed which provide the negotiated quality of service to the connections     

Design of a Switched Broad-Band Communications Network for Interactive Services

The congestion in broad-band communications networks resulting from the increased demand for interactive services is considered. It is shown that services such as a video library could not be provided to the majority of subscribers in a conventional CATV network. A design is developed for a space division multiplex broad-band network which can be expanded at minimum cost to meet an increasing demand for interactive services. The network contains two signal distribution networks: a cablecast system similar to the Rediffusion system, and a switched communication network providing point-to-point circuits for both one-way and two-way services. All broad-band signals are transmitted to the subscribers in the 1- to 10-MHz spectrum, permitting the use of twisted pair video cables and a minimum number of cable amplifiers. The broad-band cable network (BCN) is organized around 15 local switching exchanges and one central exchange. Multipoint switches in local exchanges under wired-logic circuit control connect individual subscriber communication lines to any channel. Crosspoint matrix switching groups in the local and central exchanges connect communication circuits in the broad-band communication network under programmed computer control. This network is accessed via links terminating on one channel of the multiposition switches. Per-subscriber costs are estimated to be 190 dollars for a cablecast system serving 3800 subscribers. Additional expenditures per subscriber of 40 dollars for fixed costs and 40 dollars for variable costs would provide interactive services. The range of interactive services provided would be extremely flexible, including both one-way video library service and point-to-point two-way communications.     

Local access optical networks

Both broadcast CATV and switched telephony access networks have evolved, over decades, to deliver their respective services efficiently. But these networks are not necessarily optimal for services that are rapidly emerging. This suggests that the access infrastructure will likely change in the future, driven by demands for new services and the costs of providing them. Will fiber optic networks play an important role? Trade-offs in desirable network properties (low initial costs, high capacity, flexible provisioning, enhanced maintenance and operations, etc.) are strongly influenced by the network architecture. We classify architectures on two characteristics: delivery mode (i.e., broadcast vs. switched) and carrier utilization (i.e., shared vs. dedicated), examining the trade-offs these imply with several examples of existing and proposed architectures. We show that optical networks can, by virtue of recent component development, be reconfigured to change their characteristics without changing the outside plant     

Configuration and Characteristics of a Fiber-Optic Video Distribution System

A multiservice fiber-optic subscriber system using wavelength division multiplexing technology has been developed by Nippon Telegraph and Telephone Corporation to provide both 64 kbits/s and broad-band communication services on a single multimode fiber. The subscriber network is formed in a star topology to facilitate bidirectional connection. The system was put in service in March, 1985, as part of the information network system (INS) model system. This paper describes the configuration and characteristics of the video distribution system of this fiber-optic subscriber system. The distribution system uses analog baseband video transmission at a 0.89μm wavelength. The video channel selection is made by an FDM video tuner installed in a central office. The overall performance successfully met design objectives.     

Present Status of Mechanical Connectors for Optical Fiber

Trunk transmission network systems connecting exchange offices were the first transmission systems using optical fiber cables. Subscriber network systems connecting the exchange office with each subscriber including local area networks or CATV network systems are under development at present. Two main techniques are newly required to be developed for making optical fiber mechanical connectors for optical fiber subscriber network system realization. The first is to realize a new connector with a high return loss and a low connecting loss. The second is to cut the joining cost of optical fibers. The newly developed "optical contact connector" realized a high return loss of more than 25 dB and a low connecting loss of 0.15 dB average value. A newly developed "multifiber connector" which can connect many optical fibers at the same time can save time and space for joining fiber cables, and also a "plastic molding technique" can save the cost of the connector. The performance of all these connectors is the same as that of the "optical contact connector." This paper describes the present status of the technique to obtain a high return loss connector, a multifiber connector, and a plastic molded connector for the subscriber network system.     

The fiber-optic subscriber network in Japan

Nippon Telegraph and Telephone Corporation (NTT) has two primary aims regarding the installation of optical fiber cables for subscriber networks as the access network: to provide high-speed broadband services, and to provide narrowband services through optical fiber cables with subscriber-line multiplex technology. Thus, NTT is preparing an infrastructure to support the forthcoming B-ISDN subscriber networks. NTT has been developing technologies for implementing the full-scale construction of fiber-optic subscriber networks. The present article describes the deployment methodology for these networks, their current status, and plans for their future development     

Technique de multiplexage pour réseau optique de vidéocommunication

The paper describes the building of the subscriber equipment for a fiber optic local cable network. Three signals are multiplexed on the user access: video, digital audio and anIsdn channel. The multiplexing procedure is matched to a video signal in an analogue format likely to evolve towards the digital format of the future. This procedure is based on the properties of the video signal: the periodicity of a line structure and the availability of a time slot between active sections of the video lines.     

Fiber to the Home Using a PON Infrastructure

Traffic patterns in access networks have evolved from voice- and text-oriented services to video- and image-based services. This change will require new access networks that support high-speed (> 100 Mb/s), symmetric, and guaranteed bandwidths for future video services with high-definition TV quality. To satisfy the required bandwidth over a 20-km transmission distance, single-mode optical fiber is currently the only practical choice. To minimize the cost of implementing an FTTP solution, a passive optical network (PON) that uses a point-to-multipoint architecture is generally considered to be the best approach. There are several multiple-access techniques to share a single PON architecture, and the authors addressed several of these approaches such as time-division multiple access, wavelength-division multiple access, subcarrier multiple access, and code-division multiple access. Among these multiple techniques, they focus on time-division multiplexing (TDM)-PON and wavelength-division multiplexing (WDM)-PON, which will be the most promising candidates for practical future systems. A TDM-PON shares a single-transmission channel with multiple subscribers in time domain. Then, there exists tight coupling between subscribers. A WDM-PON provides point-to-point optical connectivity using a dedicated pair of wavelengths per user. While a TDM-PON appears to be a satisfactory solution for current bandwidth demands, the combination of future data-rate projections and traffic patterns coupled with recent advances in WDM technology may result in WDM-PON becoming the preferred solution for a future proof fiber-based access network     

High-Speed and Broad-Band Communication Systems in Japan

This paper presents the current state of each high-speed and broad-band system and the development of the high-speed and broad-band network (HBN) in Japan. System configuration of a video conference system, a video transmission system, a high-speed digital circuit system, and so on, are introduced. Fundamental technologies to realize HBN, 1) switching technologies to handle broad bit-rate class transmission, 2) high-capacity transmission and high-speed digital terminal technology, 3) economical fiber optic subscriber loop technology, and 4) high-performance video codec technology, are discussed. Based on the above discussion, configuration of HBN is proposed.     

Plans for data communications in Germany

The Electronic Data Switching system (EDS) and its introduction into the network of the Federal German Post Office are presented. The great demands of future data transmission will be unable to be met by conventional techniques. Therefore, special networks for data traffic are being discussed in several countries. This paper deals with the plans of the Deutsche Bundespost (Federal German Post Office) to establish a data network by making use of the newly developed EDS system. Furthermore, it describes the individual components of the network, such as the connection of the subscriber and the techniques for transmission, concentrating, and switching. The new network will offer a great number of operational and technical facilities which cannot be provided using conventional techniques. Starting from the present international agreements, the most important operational facilities of the data network are described, and an outlook is given on future synchronous modes of operation with the EDS system.     

An adaptive congestion control scheme for real time packet videotransport

We show that modulating the source rate of a video encoder based on congestion signals from the network has two major benefits: the quality of the video transmission degrades gracefully when the network is congested and the transmission capacity is used efficiently. Source rate modulation techniques have been used in the past in designing fixed rate video encoders used over telephone networks. In such constant bit rate encoders, the source rate modulation is done using feedback information about the occupancy of a local buffer. Thus, the feedback information is available instantaneously to the encoder. In the scheme proposed, the feedback may be delayed by several frames because it comes from an intermediate switching node of a packet switched network. The paper shows the proposed scheme performs quite well despite this delay in feedback. We believe the use of such schemes will simplify the architecture used for supporting real time video services in future nationwide gigabit networks     

Wide-Band Interactive Services Experiment (WISE): A First Test of Future Video Services

An experiment of wide-band switched interactive services (video services) is presented. The experiment, named WISE (Wide-Band Interactive Services Experiment) is limited to a small number of subscribers but is representative of a future domestic environment. After a brief presentation of the scope of the activity, the video services that have been implemented, both unidirectional and bidirectional, are described. The system organization, based on a wide-band switching matrix and on the transmission of video signals on a single optical fiber by wavelength-division multiplexing, is then discussed, and the solutions adopted for the transmission equipment are examined. The structure of the service center is afterwards described, together with the subscriber procedures required to access the different services. Finally, some improvements and future possible developments of wide-band interactire systems are briefly highlighted.     

HDTV communication systems in broadband communication networks

Two high-definition television (HDTV) communication systems created for broadband communication networks are discussed. Nationwide HDTV transmission and distribution services and HDTV subscriber distribution services are examined. A network architecture for high-quality HDTV transmission is described. The transmission bit rates of HDTV services, which are the basic factors in constructing the network frame, are considered. Two HDTV coding algorithms, subband discrete cosine transform (DCT) and subband differential pulse-code modulation (DPCM) are described, and their coding bit rates discussed. A synchronous-digital-hierarchy-based synchronous transfer mode network design suitable for the transmission of HDTV signals in broadband communication networks are described     

基于HFC的宽带接入网关键技术

随着通信的发展和“信息高速公路”概念的提出,网络运营商越来越倾向集视频、话音、数据于一体的宽带综合业务,如今世界各国相继开发了基于现有铜缆的接入网技术高比特率数字用户环路(HDSL)和不对称数字用户环路(ADSL)、基于光缆接入技术的光接入网(OAN)、混合光纤同轴电缆(HFC)网络以及无线接入技术等宽带用户接入网技术,文章详细分析了HFC宽带接入网的网络结构及其关键技术。     

Fiber Optic Analog--Digital Hybrid Signal Transmission Employing Frequency Modulation

Investigations are carried out on the SNR performance in fiber optic FM transmission systems which use multimode fibers and 1.3 μm laser diodes. Both laser diode noise and modal noise are quantitatively evaluated in systems with and without employing a superimposed pulse modulation scheme. Based on these investigations, parameters for analog-digital hybrid signal transmission systems employing FM are determined. The hybrid signal consists of audio, video, and 2 Mbit/s digital data. The results obtained in transmission experiments satisfied the design objectives and confirmed the technical feasibility of an analog-digital hybrid transmission employing FM. The obtained results make the fiber optic FM transmission system with a 1.3mumLD an attractive alternative in subscriber systems, and video transmission systems for microwave IF links and CATV trunks.     

Broadband Switching System Architecture

The architecture, the design concept, and the network organization for NTT's broadband switching system field trials are described. The features of this system are: a variety of connection-type services such as reservation-based and asymmetric connections, the installation of small-size remote concentrating switch, and a system integration using various subscriber transmission media such as optical fiber, satellite, and radio. This paper also presents the system architecture along with a study of the broadband switching system through a close look at the results obtained from field trials.     

Implementation of a broadband integrated services hybrid network

The issues involved in the design of a broadband integrated services digital network (B-ISDN), that utilizes optical fibers in the subscriber loop, are considered. A hybrid scheme that provides integrated access to ISDN and broadband services by delivering voice/data signals in a digital format while using an analog format for full-motion video services to subscribers is proposed. The discussion covers planning for a B-ISDN, the system concept, implementation, the loop fiber network, subscriber equipment, and cost comparison and analysis