The focus of this thesis is the study of microscopic characterization of optical fibres and fibre Bragg gratings, by the use of a non-invasive microscopic technique, namely differential interference contrast microscopy. The thesis aims to provide detailed information on the structural and optical properties of optical fibres and fibre Bragg gratings. Furthermore, the thesis provides researchers with a new tool in the determination of various specimen parameters such as phase and refractive index distribution.