1. General

An optical fiber is a light waveguide made up of two concentric cylindrical layers called the "core" and the "cladding". Although optical fibers can be made from polymers (most often polymethyl methacrylate or PMMA), this dossier focuses solely on silica-based fibers. For the latter, the core is generally doped with germanium oxide to increase its refractive index relative to that of the cladding, which is made of pure silica. By this means, light is carried into the core by the mechanism of total internal reflections at the core-cladding interface (see figure 1 for an illustration of this mechanism)....