The ideal situation in constructing a broadband communication network is that all kinds of services are provided by a single network. Such a structure is not necessarily advantageous at the present state of technology. From such a viewpoint, the best approach would be first to construct an economically‐optimum system, mostly considering the CE type broadband distribution service, which is estimated to have the highest demand, and gradually extend the network for other services. This paper first describes that the configuration combining the star‐type subscriber link and the tree‐type trunk lines is economical and has the functional expandability. Next another configuration is considered, in which the optical fiber is used for the subscriber link and the frequency division switch is used for the channel selections in the conversion of network topology. It is shown that the system is the optimum from the viewpoint of the cost per subscriber. By applying the notion of the cross‐contact switch, it is shown that the proposed system can be extended to the CE type video retrieval service and EE type transmission service. The optical distribution system will be utilized effectively in the future new media, providing the basis for the broadband communication network.
As one approach to the realization of post 64 kbit/s ISDN, studies have been made on the optic broadband distribution system, based on the fiber optic transmission by tree (or bus) trunk line and star subscriber line. To realize a more versatile C‐E communication system, however, not only must the service functions such as distribution of multichannel video information, character, still picture and data be provided, but also the information retrieval function with random access such as videotex.
This paper discusses theoretically the realizability of the information retrieval service by the optic broadband distribution system from the viewpoint of whether or not a sufficient number of subscribers can be accommodated.
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