Wide-band optical fibre local distribution systems

The concept of a wide-band optical local network is presented and the technical aspects are discussed in detail. The types of service are outlined and grouped according to the requirements for transmission capacity. The components available and their characteristics are presented. The modulation characteristics of the semiconductor laser are scrutinized and show that the laser is unfit for high-quality analogue intensity modulation. The aspects of digital and analogue transmission of television are examined and compared. Analogue transmission can provide transmission of only a few TV channels at the present level of quality whereas digital transmission can provide improved quality with a comfortable system margin. However, none of the schemes are suited for simultaneous transmission of many TV channels, which shows that the direct optical equivalent of a conventional CATV network cannot yet be constructed. The concepts of central switching and customer switching are outlined together with the options for multiplexing and network structure. Finally a review is made of known activities. The review covers eleven studied, planned and implemented experimental networks. Nearly all of the networks employ central switching. The older experiments use exclusively analogue transmission whereas there is a growing tendency to use digital transmission in recently planned networks.