A fibre Bragg grating (FBG) is a type of distributed Bragg reflector constructed in a short segment of optical fibre that reflects particular wavelengths of light and transmits all the others. As such, FBGs can be used as inline optical filters to block certain wavelengths, or as wavelength-specific reflectors. Applications include optical fibre communications, sensors and fibre lasers. This book addresses the critical challenge of developing Fibre Bragg Gratings (FBGs) for applications as sensors in harsh and space environment. Coverage ranges from the basic principles through design, fabrication, and testing to their industrial implementation. A thorough review includes the in-depth examination of the FBGs properties and the most important developments in devices and applications. A particular emphasis is given to the applications of fibre optic sensors in the space environment, which is characterized mainly by vacuum, high thermal gradients, mechanical vibrations and various types of cosmic radiation. The book concludes with a summary and overview of challenges faced by FBG technology. The book is supplemented by an extensive survey of published papers, books and conference reports. As an added benefit, the book is structured in such a way as to provide useful and in-depth training and skills development to graduate/undergraduate students, specialised engineers, and academic/industrial experts.