In the last years, the Optoelectronics has been established as a top field of research able to drive towards new technological solutions. The abundant achievements in the field of optics as well in optical communications have been of great importance and triggered a number of innovations. Among the large group of existing optical components, optical fiber components are mainly relevant due to three factors: their simplicity, their nature as an optical fiber based component and the capability of optical fiber to carry information. In this book the focus is on one of these optical components: optical fiber gratings, which have unique optical processing properties and are quite interesting for the development of devices for optical communications and sensing applications. The inscription of fiber gratings is addressed in this book and a detailed analysis of the acousto-optic modulation in fiber gratings in silica and polymer optical fiber is also discussed.