ABSTRACT
This chapter explains photosensitivity, the fabrication of photosensitive fibre, in-fibre grating writing techniques and some applications that we have developed at CSIR-Central Glass & Ceramic Research Institute (CGCRI). It describes the different types of photosensitive fibres and their characteristics in terms of the generation of defects to increase efficiency. Photosensitivity means that the index of refraction of the fibre changes when exposed to light. Germanium-doped silica fibre exhibits permanent change in the refractive index of its core when it is exposed to intense ultraviolet (UV) light of a specific wavelength. The grating characteristics change due to environmental conditions, such as stress, strain and temperature, and the resulting shift in the central wavelength determines the magnitude of the stress/strain and temperature at a minute scale, which helps sensitive sensing in smart structures in particular.
