Effect of H2/O2 ratio on the GeO2 concentration profile in SiO2:GeO2 glass preforms prepared by vapor-phase axial deposition

GeO2 radial concentration in silica glass preforms, prepared by vapor-phase axial deposition (VAD) method, was analyzed by X-ray fluorescence (XRF) measurements. The results were used to evaluate the effect of the H2/O2 ratio used during the deposition process in the formation of the GeO2 concentration profile. Considering four different H2/O2 ratios, GeO2 distribution was observed to decrease monotonically with the increasing radius for H2/O2⩽1.5, and the acute shape around the core center of the GeO2 concentration profile, decreased with increasing H2/O2 ratio. When the ratio H2/O2=2.5, the central doping of GeO2 was minimal, and a constant distribution was obtained along glass preform radii. The results seem to indicate that the control of spatial distribution in the concentration of GeO2 deposited is favorable for the ratio H2/O2⩽1.5.