An Interactive Local Distribution Network Using Fiber Optic Technologies

Abstract

AbstractThis paper presents a complete interactive teledistribution network based on fiber optic technologies, with a modular design allowing a total flexibility in terms of number of pro­ grammes and number of subscribers as well as future evolution towards integration of narrow band or future broadband switched services, without modifying the basic existing infrastruc­ ture.IntroductionThe fast increasing demand for domestic or professional information and communications services, plus the availability of new technologies (fiber optics, satellites) are already enabling the creation of high performance, expandable networks.These networks will gradually open the way to a large range of services based on signals which transmit sound (telephone), image (television), and data (data processing, videotex). This paper presents a complete interactive teledistribution network based on fiber optic technologies, with a modular design allowing a total flexibility in terms of number of pro­ grammes and number of subscribers as well as future evolution towards integration of servi­ ces provided by the switched network, or future broadband services, without modifying the basic existing infrastructure.An integrated local communication network is an assembly of hardware and software lin­ king the subscribers to those providing the services, or linking the subscribers among them­ selves; a remote control unit or a terminal gives the subscriber physical access to the in­ formation source. (Figure 1).The communications between subscribers and those offerring services can use various types of networks and concern information of the following types :- distribution (cable TV),- collection (alarm, security),- interactive (videotex, enhanced videotex).Person to person communications (telephone, hardcopy, visiophony) are related to swit­ ched networks.Analysis of servicesOur first task consists of trying to organize and analyse the needs, expressed in such a way as to translate them into elementary and modular functions. A symbolic representation of services is related to interactivity (See Figure 2 ), it means, information flows in both transmission directions on the subscriber network (upstream and downstream).The density of information received at the subscriber terminal unit is represented on x-axis, the density of information emitted by the subscriber is represented on y-axis.Consequent, ly, strictly distributed services, like conventional CATV, are located on the axis y = o, when strictly collected ones, like alarms, security and meter reading are located on the axis x = o.The bissectrix of this figure corresponds to services with a maximum interactivity, as telephone services and later on visiophony; they correspond to person to person communica­ tion services using switching techniques.On the same figure, we have shown the potential evolution of both fields covered by con­ ventional telephone and CATV networks.It is clear that, even if some services can be indifferently provided by the two approa­ ches, their fields seem to be limited very quickly.