3 - Transmission media

Abstract

Data communications is all about moving or copying data from one place to another. This may be from a personal computer to a file server on a local area network (LAN), or may be from the Internet to a personal computer. In all cases, data must be carded over a copper cable or an optical fiber cable at some point. This chapter describes the types of cable and about their respective performances. It is important to know the limitations of the transmission media in order to understand why modems, repeaters and other Data Communications Equipment (DCE) are necessary. The transmission path in a data communications system may comprise cables, amplifiers/regenerators, attenuators, filters, and diplexers. The electrical characteristics of such items are usually specified in terms of one or more of the following parameters: gain or loss, input impedance, output impedance, frequency response, bandwidth, phase shift, equivalent circuit of a transmission element, and frequency response of a transmission element.