Chlorination and vaporization of GeO2 component in SiO2:GeO2 porous preform in dehydration process by VAD method and spontaneous formation of SiO2 cladding layer during the dehydration by selective vaporization of GeO2

Germania nanocrystals in Modified Chemical Vapour Deposition

“…Recent studies of silica soot particles (SiO 2 ) in MCVD have found them to be invariably amorphous [7]. Several studies of the VAD process [8][9][10][11][12][13][14] have reported that under certain conditions some of the GeO 2 soot particles formed are crystalline. Crystalline GeO 2 has never been reported in MCVD.…”

Fundamental Understanding of Processes Involved in Optical Fiber Manufacturing Using Outside Vapor Deposition Method

“…While the germania loss is not appreciable for amorphous germania, a significant fraction of crystalline germania is lost because of its reaction with chlorine at temperatures typical of drying process in optical fiber manufacturing. 18 A model has also been reported in Tandon and Murtagh 17 that predicts the loss and migration of germania during sintering. Changes in germania profile during consolidation are estimated ( Fig.…”

“…However, germania etching because of reaction with chlorine is extremely sensitive to the germania crystallinity. While the germania loss is not appreciable for amorphous germania, a significant fraction of crystalline germania is lost because of its reaction with chlorine at temperatures typical of drying process in optical fiber manufacturing 18 …”

“…Germania crystallinity is known to appreciably affect the germania loss and migration behavior during the drying and sintering phase of optical fiber processing. 18 The loss of germania takes place primarily because of the following two reactions: (i) decomposition of germania into germanium oxide and oxygen (ii) reaction of germania with chlorine resulting in germanium tetrachloride and oxygen. The germania loss behavior is very similar for amorphous and crystalline germania because of the first reaction.…”

Automation for monitoring of the refractive index profile of vapor-phase-deposited soot preforms for optical fiber

“…On the other hand, the crystalline hexagonal phase, which is formed in lower temperature regions, is unstable for chlorination reaction in the dehydration process. 16 Previous experiments conducted in our laboratory showed that there are optimized processing conditions that maintain the germanium doping profile characteristics of unsintered soot preform related to the doping profile in the sintered preform. 10,17 To determine the radial distribution of the germanium doping profile a Rigaku RIX3100 x-ray fluorescence spectrometer was used.…”