Optical fibres with an Al2O3-doped silicate core composition

Optical fibres consisting of Al2O3-SiO2 and Al2O3-P2O5-SiO2 cores have been fabricated by MCVD with a minimum attenuation of 0.7 dB/km at 1.6 μm. Both single-mode and multimode fibres were produced, the latter with a numerical aperture as high as 0.29. The tendency for Al2O3-SiO2 glasses produced by flame hydrolysis processes to devitrify during consolidation is diminished by MCVD processing, thus allowing higher Al2O3 doping and versatility with regard to the incorporation of other ions.