In this thesis the design and fabrication of dispersion decreasing fibres has been investigated. Such novel fibres have a number of novel uses in pulse train generation and loss compensation. The use of fibre diameter control for the production of dispersion decreasing fibres has been investigated. This has proved to be a good technique, and has facilitated the production of a number of useful fibres. A fibre suitable for the generation of 40GHz trains of optical pulses has been produced. This fibre has successfully been used for the generation of optical pulse trains at this data rate. Modelling has been performed to predict the likely propagation characteristics of these pulses. This indicates that propagation with this source is limited to 750km with an amplifier spacing of 30km. The use of dispersion decreasing fibres for loss compensation has been investigated through numerical simulation. The results indicate that there are a number of key high order effects which all affect such fibres. In order for such a dispersion decreasing fibre the initial dispersion must be as low as possible. Further the use of a dispersion flattened preform may also be advisable. Dispersion decreasing fibres have also been used to produce dark soliton trains. The pulses produced have good propagation characteristics over a number of soliton periods. and appear bandwidth limited. The behaviour of the source is shown to be in good agreement with numerical modelling results.