Propagation characteristics of optical fibres

A theoretical and experimental study has been made of propagation in multimode optical fibre. The fibre used in the experiments mainly consists of a capillary of ME1 glass filled with hexachlorobuta-1,3-diene. The main topics considered in this thesis are single-mode propagation and mode conversion effects due to bending, undulation and stress or strain. A measured pulse dispersion of less than 0.4ns/km has been achieved. A contributing factor is the high-loss cladding which results in a preferential mode filtering of higher-order modes so that the pulse dispersion for a beam of high launching angular width is reduced for a relatively small increase in attenuation. Pulse dispersion and mode conversion are not strong functions of bending and undulation of the fibre, but strongly depend on stress or strain. The graded-index fibre has also been considered and its pulse dispersion is predicted to be half that of the pulse dispersion of the liquid-core fibre.