Low-loss optical glass fibre with Al 2 O 3 -SiO 2 core

Optical glass fibres, consisting of an Al2O3-SiO2 core and SiO2 cladding, were produced by using a glass growth technique of vapour deposition in a flame. The core measured from 4 to 10 μ in diameter, and the difference in refractive index between the core and the cladding was 0.003. The lowest loss of this fibre was 10 dB/km at 0.66 μm.