Special issue paper. Single-mode transmission systems for civil telecommunication

Owing to the low attenuation of optical fibres, transmission systems with repeater spacings of 10¿20 km become feasible. For future high-capacity systems this imposes great demands on the fibre bandwidth. Because of the inherent limitations of multimode fibres, single-mode fibre waveguides have to be taken into account. The transmission properties of single-mode fibres and their dependence on the fibre design are discussed, resulting in recommendations for practical fibre structures and statements of their production tolerances. For efficient coupling between two single-mode fibres the requirements are analysed and methods are described to achieve them in practice. As a transmitter for single-mode fibre systems mainly the GaAlAs-injection laser is considered. Its high speed modulation and spectral behaviour are discussed with reference to high-capacity transmission systems. Also the problem of launching is treated in detail. Finally, fast avalanche-photodiodes are considered as receivers for single-mode fibre transmission systems.