Germanium chemistry in the MCVD process for optical fiber fabrication

Doping of optical fiber preforms via porous silica layer infiltration with salt solutions

“…The germanium oxide yield in the reaction of germanium tetrachloride with oxygen depends on the deposition temperature of the SiO 2 /GeO 2 layer [13]. In connection with this, to produce a porous layer of the desired composition we first examined the dependence of the germanium oxide yield on the temperature of the reaction zone (assumed to be equal to the temperature of the outer wall of the silica substrate tube in the area heated by an oxygen-hydrogen torch, as determined by an IRCON-7000 IR pyrometer).…”

Jet‐Assisted Aerosol CVD for Multicomponent Particle Deposition

“…It is also noted that the GeO 2 mass fraction becomes smaller for higher temperature jet case, which would be due to the reverse reaction of GeCl 4 oxidation. [6] The deposition mass profile for each component along the axial direction can be easily obtained from the overall deposition mass (Fig. 2) and the measured composition (Fig.…”

“…[5] Wood et al [6] experimentally investigated germanium chemistry in MCVD by varying the torch temperature, reactant composition, and gas flow rates, and then proposed a simple model predicting the extent of germanium incorporation in the preform deposit. Theoretical studies of simultaneous chemistry, heat and mass transfer during the multicomponent MCVD process, and aerosol dynamics were carried out.…”

Chemical Vapour Deposition for Optical Fibre Technology

“…At low temperature the reactions are controlled by kinetics, but at the higher temperature encountered in the practice the gas concentrations and glass composition are controlled by thermodynamic equilibria. [7] shows the effluent composition, determined by infrared spectroscopy, versus the reaction temperature for an MCVD using Sic& (0.5 glmin). GeCLq (0.05 g/min), POC13 (0.016 g/min) and 02 (1540 cclmin): under 1200 OK the effluent concentration are unchanged from the initial values, between 1200 and 1600 OK the reaction of S i Q with 02 is indicated by small quantity presence of Si@C16, while over 1600 O K the reaction is complete (Si@ does not appear in the plot because it was filtered out to avoid scattering in the optical measurement apparatus).…”

“…Particle growth occurs as the result of coagulation of colliding particles, as the finely divided solids suspended in the gas pass through the hot zone. Collisions induced by Brownian motion result in aggregates of individual glass particles, which sinter together by viscous flow if the glass is sufficiently fluid [7], up to a diameter of 0.2 pm. A soot particle placed in a field with a temperature gradient, tends to move towards the cooled area, as a result of the impact with particles at higher temperature.…”