The Glass Structure Change: A Novel Technique of Refractive Index Modification in Optical Fibers

摘要

It is shown that the glass structure change is a simple and widely applicable method to modify the refractive index in various glass fibers. The glass structure can be changed by heat treatments including annealing and rapid solidification. Index differences of dispersive fibers fabricated from optical glasses are controlled by the glass structure change induced by annealing. Multimode dispersive fibers are changed into single-mode fibers by annealing under suitable conditions. Wavelength-insensitive couplers are made of the annealed dispersive fibers. The mode-field expander and reducer are fabricated by heating locally dispersive fibers at low and high temperatures. Long-period fiber gratings are written in conventional silica fibers by rapid solidification, and the resonance wavelengths are tuned by heating.