The fiber Bragg grating, with its periodical perturbation of the refra
ctive index in the fiber core, is a very attractive optical device. Th
ere are Various applications for fiber Bragg gratings, not only in sim
ple reflecting filters but, for example, in wavelength tuning devices
or sensing devices. In this paper, the principle of the grating format
ion, the fabrication techniques and some applications are described.