Changes of light

The paper is concerned with the technology of optoelectronic communications. It describes the basic technology and the effect of very high speed connectivity on the design and use of communications and information systems. Developments in these systems can be characterised into three revolutions: hardware, software and communications. The hardware revolution started with the invention of the electronic valve, continued with the transistor, and has permeated our daily lives in the form of the integrated circuit. The software revolution started later with the invention of languages and sophisticated operating systems, greatly increasing the ability to produce complex systems quickly. The communications revolution is in its early stages; it is based on optoelectronic technology. The paper describes the fundamentals of transmitting light through optical fibre including the evolution from low capacity systems to the latest ideas on multichannel high capacity techniques. Optoelectronics transmission technology evolved in response to the demands of telecommunications, and it has been widely applied at high capacity routes over recent years. The technology affecting the architecture and design of complex systems, such as mainframe computers and digital telephone exchanges, is illustrated for the hardware and for the software of such systems. The conclusion is that the changes being caused by the use of light as a connecting technique represent the third revolution in information technology. Furthermore, these changes are magnifying and accelerating the effects of the two earlier revolutions of hardware and software technologies. The full extent of the changes being caused by light are only just becoming apparent.