ABSTRACT
The major area of application for optical fibers is communications. Optical fibers have already been used practically for public communication and various local area networks in such facilities as factories, office buildings, laboratories, and so on. For fiber communications, development has been made relating mainly to silica glass fibers. A fiber sensor has an optical element for sensing measurands in the optical path, consisting mainly of optical fibers. The intrinsic type and the extrinsic type of sensor element are used in interferometric fiber sensors. The quasi-distributed fiber sensors utilize discrete sensor elements that are properly arranged in the fiber network. For communication applications, refractive index profiles of fibers are properly designed for dispersion, mode field diameter, cutoff wavelength and so on as required by the system. Fiber sensors utilizing the interference of lightwaves consist of sensor element and fibers for optical paths.
