Fiber Bragg grating sensors: principles and applications

Following the early work on the formation of photogenerated gratings in germanosilicate optical fiber by sustained exposure of the core to the interference pattern produced by oppositely propagating modes of argon-ion laser radiation that was first reported in 1978 (Hill et al., 1978), the pioneering sensor work at the United Technology Research Centre, which has been regarded as a milestone for in-fiber Bragg grating (FBG) sensors, was published 11 years later (Meltz et al, 1989). Their side-writing technique makes a Bragg grating directly in the fiber core using a holographic interferometer illuminated with a coherent ultraviolet (UV) source. Versatility in the fabrication of FBGs has been gained from the fact that the Bragg wavelength is independent of the writing laser used. Subsequent to this initial work the interest in FBGs has increased considerably in recent years.