ystems in metropolitan areas, scriber radio, IEEE International Conference on Communica- IEEE International Conference on Communications, ICC'84, tions, ICC'86, Toronto, Canada, 3 pp. 1758-1762. Amsterdam, Netherlands, pp. 946-950. Yoshida, T. (1984) Digital subscriber radio system in the 26GHz Okubo, H. Miura, S. and Nagasawa, S. (1988) Building block band, Japan Telecom. Rev., 26, (3), pp. 188-194. design of large capacity PCM-TDMA subscriber system and direct digital interface to digital exchange, IEE International Conference on Rural Telecommunications, London, U.K., Con- 52.6 Bibliography ference Publication No. 286, pp. 69-73. Omtveit, O. (1989) Development of a radio network, Communica- CCITT (1970) GAS-4, Primary sources of energy, Geneva. tions Engineering International, 10, (10), pp. 46-48. CCITT (1989) GAS-7, Vol II, Training Handbook of Rural Telecom- Raju, G.S. and Prasad, K.V.K.K. (1990) A TDMA point to multi- munications, Geneva. point rural radio system for trunking and local loop applications, CCITT/CCIR (1979) Rural Telecommunications, Geneva. Fibre optic communications Takis Hadjifotiou Bell Northern Research (Sections 53.1-53.6) John McFarlane Northern Telecom (Section 53.7) Contents 53.1 Principles of light transmission 53/3 53.2 Optical sources 53/9 53.3 Optical detectors 53/14 53.4 Optical receivers and transmitters 53/18 53.5 Optical system design 53/22 53.6 Applications of fibre optic communications 53/24 53.7 The future of fibre networks 53/25 This page intentionally left blank Principles of light transmission 53/3 53.1 Principles of light transmission light into medium II ceases completely. This critical angle is given by Equation 53.2. 53.1.1 Basics of optical fibre transmission (53.2) The propagation of light is governed by Maxwell's equations but a good insight of the propagation in dielectric material can be gained through Snell's law on refraction and reflection. When the incident angle light propagates into me- Consider two media I and II with refractive indices, n, and n2 respect