In this thesis, I present my works on the fabrication, the characterization and the use of optical microfibres. Microfibres are optical fibres drawn down to sub-wavelength diameters by a temperature controlled process. Due to their small dimensions, microfibers have very special properties such as a high confinement of the electromagnetic field, a enhanced non-linear coefficient and a large evanescent tail. These properties are studied in the first chapter, after which a description of the techniques used for the drawing and manipulation of the microfibres is given. Next, we present our experiments on non-linear effects in silica microfibres. In particular, we show that it is possible to generate green light with a pump at 1:55μm thanks to phase-matched third harmonic generation. In order to obtain higher efficiency in this field, the opportunity of drawing microfibres with highly non-linear glasses is discussed. A model of a microfibre laser using erbium doped tellurite glass is also presented. In the last chapter, microfibres are studied in the near field, with a scanning near field optical microscope, revealing the inner characteristics of the propagation in microfibres.