Properties of fluorosilicate glass prepared by MCVD

Multilayer and two-layer fiber preforms with a fluorosilicate glass core have been produced by the modified chemical vapor deposition (MCVD) process with SiF4 as a fluorination agent. The fluorine profile across the preforms has been studied, the fluorine concentration in the glass has been determined as a function of the initial vapor mixture composition, and the effect of the fluorine concentration on the refractive-index difference between the fluorosilicate and silica glasses and on the mechanical stress in the glass has been examined. Comparison of the present results with literature data demonstrates that the above parameters depend significantly on the fluorosilicate glass preparation process: MCVD or plasma chemical vapor deposition (PCVD). This is tentatively attributed to the difference in structure between the glasses made by MCVD and PCVD.