Multi-cladding optical fibers with long-period gratings, e.g. for fiber amplifiers

摘要

Multi-cladding optical fiber comprises: (i) a core (40) made of germanium-doped silica (GeO2-SiO2) for guiding light; (ii) an inner cladding (42) surrounding the core, made of fluorine-doped silica (F-SiO2) with a lower refractive index than the core; and (iii) an outer cladding (44) of silica, with a refractive index between that of the core and the inner cladding. An Independent claim is included for the manufacture of a long-period optical fiber grating using the above fiber structure, including periodically changing the refractive index of the fiber structure by periodic annealing. Preferred Features: Annealing is performed by arc discharge or CO2 laser irradiation.