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

GeO 2 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 H 2 /O 2 ratio used during the deposition process in the formation of the GeO 2 concentration profile. Considering four different H 2 /O 2 ratios, GeO 2 distribution was observed to decrease monotonically with the increasing radius for H 2 /O 2 ≤1.5, and the acute shape around the core center of the GeO 2 concentration profile, decreased with increasing H 2 /O 2 ratio. When the ratio H 2 /O 2 =2.5, the central doping of GeO 2 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 GeO 2 deposited is favorable for the ratio H 2 /O 2 ≤1.5.