Gambling, W.A. and Matsumura, H.
A comparison of single-mode and multimode fibres for long-distance telecommunications.
In, Fiber and Integrated Optics Conference, Cargese, Corsica, France,
When research on optical fibre communications was first started in 1966 the main interest was in single-mode fibres since it was thought that the bandwidth of step-index fibres, the only type under consideration at the time, would be rather limited. Subsequently, with the development of SELFOC and other types of graded-index fibres, a high degree of equalisation of the group velocities of the fibre modes became possible so that the bandwidth available with multimode fibres was greatly increased. Interest then shifted away from single-mode fibres because of the difficulties of handling, launching, jointing and fabrication and also because the lifetimes of semiconductor lasers, the only small and relatively efficient sources possible, were not high. However the limits of bandwidth which are theoretically possible with an optimum refractive-index distribution are difficult to achieve in practice and the technology has now advanced to the stage where single-mode fibres may not be as difficult to incorporate into a practical system as was first thought. A renewed interest has therefore been shown in small-core fibres and a comparison of their properties with those of multimode fibres is presented here.
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