A method of manufacturing synthetic quartz glass through an outside vapor deposition (OVD) process with improved deposition efficiency. When a hollow cylindrical synthetic quartz glass product is manufactured through an OVD method or the like, it is environmentally friendly in view of using a smaller amount of chlorine and is economical in view of requiring no separate treatment equipment, as compared to a conventional technique using silicon chloride (SiCl.sub.4). Also, the method, in which octamethylcyclotetrasiloxane is supplied to a deposition burner while being sprayed in the form of a droplet along with a high-pressure carrier gas and vaporized by the deposition burner, can effectively address the high-temperature heating and slow decomposition involved when octamethylcyclotetrasiloxane ([(CH.sub.3).sub.2SiO].sub.4) is used as a source for depositing silicon dioxide particles.

Vaporizers and systems for vaporizing liquid precursor for forming glass optical fiber preforms are provided. The vaporizer includes an expansion chamber at least partially enclosed by a side wall, the expansion chamber comprising an upper end and a lower end with the side wall disposed between the upper end and the lower end. The vaporizer further includes a closed-loop liquid delivery conduit positioned in the expansion chamber proximate to the upper end of the expansion chamber, wherein the closed-loop liquid delivery conduit comprises a plurality of nozzles oriented to direct a spray of liquid precursor onto an inner surface of the side wall. Further, the vaporizer includes at least one supply conduit positioned proximate the upper end of the expansion chamber and coupled to the closed-loop liquid delivery conduit, and a vapor delivery outlet coupled to the expansion chamber and configured to direct vaporized liquid precursor from the expansion chamber.

A method for producing titanium-doped synthetic quartz glass includes: (A) providing a liquid SiO.sub.2 feedstock material that comprises more than 60% by weight of the polyalkylsiloxane D4; (B) evaporating the liquid SiO.sub.2 feedstock material to produce a gaseous SiO.sub.2 feedstock vapor; (C) evaporating a liquid TiO2 feedstock material to produce a gaseous TiO2 feedstock vapor; (D) converting the SiO.sub.2 feedstock vapor and the TiO2 feedstock vapor into SiO2 particles and TiO2 particles, respectively; (E) depositing the SiO2 particles and the TiO2 particles on a deposition surface while forming a titanium-doped SiO.sub.2 soot body; (F) vitrifying the titanium-doped SiO.sub.2 soot body while forming the synthetic quartz glass, whereby the TiO2 concentration of the synthetic quartz glass is between 5% by weight and 11% by weight. The liquid SiO.sub.2 feedstock material comprises at least one additional component made of the polyalkylsiloxane D3 having a weight fraction of mD3 and one additional component made of the polyalkylsiloxane D5 having a weight fraction of mD5 at a weight ratio of mD3/mD5 in a range of 0.01 to 1, and the liquid SiO.sub.2 feedstock material provided is evaporated while maintaining the weight ratio of mD3/mD5 and at least 99% by weight thereof are evaporated to form the gaseous SiO.sub.2 feedstock vapor.

A method of producing a glass preform including: forming a porous glass soot configured by an inner deposition soot deposited on a start material and an outer deposition soot deposited outside the inner deposition soot; and sintering, after the forming, the porous glass soot while doping with fluorine to form a glass body including an inner glass portion and an outer glass layer. An amount of the fluorine, with which the inner deposition soot is doped at the sintering, is equal to or more than 0 g/cm.sup.3 and less than an amount of the fluorine with which the outer deposition soot is doped.

A process for producing a fluorinated quartz glass is described, including providing an SiO.sub.2 soot body; reacting the SiO.sub.2 soot body with a fluorinating agent having a boiling point of greater than or equal to −10° C. to obtain a fluorinated SiO.sub.2 soot body; and vitrifying the fluorinated SiO.sub.2 soot body.

A process for the production of a fluorinated quartz glass including the steps of generating SiO.sub.2 particles in a synthesis burner; depositing the resulting SiO.sub.2 particles into a body; and vitrifying the resulting body, wherein a fluorinating agent having a boiling point greater than or equal to −10° C. is supplied to the synthesis burner.

A manufacturing method of a porous glass preform for optical fiber by depositing glass microparticles on a starting member, including supplying a vaporizer with organic silicon compound raw material in a liquid state and a carrier gas; in the vaporizer, mixing and vaporizing the organic silicon compound raw material in a liquid state and the carrier gas to convert the organic silicon compound raw material and the carrier gas into a raw material mixed gas; supplying a burner with the raw material mixed gas and a combustible gas, combusting the raw material mixed gas and the combustible gas in the burner, and ejecting SiO.sub.2 microparticles generated by the combustion from the burner; and depositing the SiO.sub.2 microparticles ejected from the burner on the starting member by repeatedly moving a single body, in which the vaporizer and the burner are synchronized, parallel to the starting member in a longitudinal direction thereof.

When organic siloxane in a liquid state is used as a raw material for glass particles, the formation of polymerized substances is suppressed when the raw material is vaporized in a vaporizer. In the manufacturing method of porous glass base material according to the present invention, the liquid organic siloxane, which is the raw material, is mixed with a carrier gas in the vaporizer, vaporized by the heat generated from the inner wall of the vaporizer heated by a heater unit, and supplied to the burner as a gas raw material. The porous glass base material is manufactured by depositing the glass particles generated by the combustion of the gas raw material on the starting material. The heating output of the heater unit is controlled so that the maximum temperature of the inner wall of the vaporizer is 230° C. or lower.

A method of producing an optical fiber preform includes a silica glass body forming step of forming a silica glass body to be at least a portion of a core portion. The method includes an alkali-metal-doped silica glass body forming step of forming an alkali-metal-doped silica glass body doped with an alkali metal around the silica glass body such that the alkali-metal-doped silica glass body contacts the silica glass body. The method further includes a diffusing step of diffusing the alkali metal from the alkali-metal-doped silica glass body to the silica glass body by a heat treatment.

Provided is a device for producing a fine glass particle deposited body by depositing fine glass particles on a starting rod disposed within a reaction vessel, the device being provided with: a burner for synthesizing fine glass particles by jetting out a source gas; a transfer mechanism to which the burner is disposed and which causes the burner to move backward in association with an increase in the diameter of a fine glass particle deposited body; a vaporizer which is disposed to the transfer mechanism so as to be moved backward integrally with the burner and which converts a liquid siloxane into a source gas through vaporization; piping through which the source gas is fed from the vaporizer to the burner; and a heating mechanism which heats up the piping with a heating temperature of at least 230° C.