Fiber Optics Sensors

Fiber optic technology started in 1970’s, for long distance telecommunications, and it has experienced an exponential growth during the last four decades. Sensing applications are a small spin-off from this technology, taking profit of developments done for optoelectronic components and concepts. Optical fibers are cylindrical dielectric waveguides for the propagation of the light, made out from high purity, low loss optical materials, usually silica (Optical fibers made from polymers and other transparent materials are also commercially available). The refractive index of the core (about 1.46 for silica) is slightly higher than surrounding material or cladding, due to the presence of dopants. Light is confined at the core, because optical rays arriving to the interface core/cladding with an angle higher than the total reflectance angle, as defined by the Snell law, will follow total reflections and will remain confined at the core. Only when the fiber is locally bent with a sharp radius, the light may escape.