Abstract: A glass preform which is used for fabricating an optical fiber, has substantially no bubbles therein and contains sufficient amount of fluorine is produced by a method comprising steps of: forming a porous glass soot body from a glass-forming raw material, removing trapped gas and water from pores of the soot body by heating the soot body under pressure lower than several ten Torr. at a temperature at which the soot body is not vitrified, filling the pores of the soot body with a gas containing SiF.sub.

Abstract: A glass preform which is used for fabricating an optical fiber, has substantially no bubbles therein and contains sufficient amount of fluorine is produced by a method comprising steps of: forming a porous glass soot body from a glass-forming raw material, removing trapped gas and water from pores of the soot body by heating the soot body under pressure lower than several ten Torr. at a temperature at which the soot body is not vitrified, filling the pores of the soot body with a gas containing SiF.sub.

Abstract: A glass preform is produced by forming a glass soot composite body having a core portion consisting of a solid glass and a peripheral portion consisting of a porous glass mass, removing trapped gas and water from pores of the soot composite body by heating the soot composite body under a pressure lower than several ten Torr. at a temperature at which the porous glass mass is not vitrified, filling the pores in the porous glass mass of the soot composite body with a gas containing SiF.sub.4, the partial pressure of which is a function of the desired specific difference of refractive index, thus uniformly adding fluorine to the soot glass mass, and vitrifying the fluorine-added soot glass mass into a transparent glass mass to form a glass preform.

Abstract: An apparatus is provided for the production of a porous preform of SiO.sub.2 used in the manufacture of optical fiber wherein damage to the preform caused by falling clusters of SiO.sub.2 or GeO.sub.2 formed on the wall of the deposition chamber is eliminated. In accordance with the invention, a conductive shielding member is provided inside the wall defining the deposition chamber. This shielding member eliminates an electrostatic field produced on the wall by charging, therefore preventing the adherence of fine particles thereto.

Abstract: A process for producing a glass member includes subjecting a silicon, boron, phosphorous or aluminum compound or both a silicon, boron, phosphorous or aluminum compound and a dopant compound to vapor phase reaction to form a fine powder of fused silica, borate, phosphate or alumina or doped fused silica, borate, phosphate or alumina. Then the powder is partially sintered to form a porous glass body which subsequently is immersed in a solution containing a dopant compound thereby depositing the dopant compound on the surfaces of the pores in the glass body. Thereafter, the porous glass body is dried before the pores are collapsed to form the glass member.