TABLE OF CONTENTS In this chapter we have looked at the wide ranging subject of transmission systems as used in telecommunications. In Section 4.2 we began with the basis mechanism of transmission and then looked at the physical transmission media: copper cable, coaxial cable, optical fibre and radio. Section 4.3 addressed the various ways of building a digital multiplexed payload for carrying over the transmission media, covering:
PCM and the basic 2 or 1.5 Mbit/s digital block the basic building block of digital networks;
PDH, the original digital transmission multiplex payload system;
SONET and SDH, the synchronous digital payload system that facilitates a managed transmission network, as well as eliminating the multiplexor mountain problems of PDH.
The wide range of transmission systems currently in use by network operators were then briefly reviewed in Section 4.4, including:
Metallic cable;
The family of xDSL (i.e. ISDN, ADSL,VDSL, HDSL and SDSL) systems;
Optical fibre systems, primarily point-to-point;
PON systems, for cost-effective access applications;
DWDM, which by using many colours of light is providing ever increasing capacity over optical fibre;
Microwave radio systems;
Earth satellite systems (geostationary, LEO and MEO);
Wireless LANs and wireless MANs.
The deployment of digital multiplexed payloads over radio, metallic line or optical fibre systems in the access, core and international transmission networks is covered in the next chapter.
