Optical Networks: A Practical Perspective - Part 63. This book describes a revolution within a revolution, the opening up of the capacity of the now-familiar optical fiber to carry more messages, handle a wider variety of transmission types, and provide improved reliabilities and ease of use. In many places where fiber has been installed simply as a better form of copper, even the gigabit capacities that result have not proved adequate to keep up with the demand. The inborn human voracity for more and more bandwidth, plus the growing realization that there are other flexibilities to be had by imaginative use of the fiber, have led people. | This Page Intentionally Left Blank chapter Access Networks In previous chapters we have explored the use of optical networks for metro and long-haul network applications. The access network is the last leg of the telecommunications network that runs from the service provider s facility to the home or business. With fiber now directly available to many office buildings in metropolitan areas networks based on SONET SDH or Ethernet-based technologies are being used to provide high-speed access to large business users. Business users are big consumers of data services many of which are delivered in the form of leased lines at various speeds ranging from Mb s to several gigabits per second. While this is happening the telephone and cable companies are also placing a significant emphasis on the development of networks that will allow them to provide a variety of services to individual homes and small to medium businesses. This is the focus of this chapter. Today homes get essentially two types of services plain old telephone service POTS over the telephone network and broadcast analog video over the cable network. Recently added to this mix are data services for Internet access using either digital subscriber line DSL technology over the telephone network or cable modem service over the cable network. Early efforts on developing high-capacity access networks were devoted to developing networks that would accommodate various forms of video such as video-on-demand and high-definition television. However the range of services that users are expected to demand in the future is vast and unpredictable. Today end users 591 592 Access Networks Table Different types of services that must be supported by an access network. The bandwidth requirements are given for each individual stream. Service Type Downstream Bandwidth Upstream Bandwidth Telephony Switched 4 kHz 4 kHz ISDN Switched 144 kb s 144 kb s Broadcast video Broadcast 6 MHz or 2-6 Mb s 0 Interactive video Switched
