One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate I prepared from a pyrogenically produced silicon dioxide powder, treating the silicon dioxide granulate I with a reactant at a temperature in a range from 1000 to 1300 C., and making a glass melt out of the silicon dioxide granulate. A quartz glass body is made out of at least a part of the glass melt. Furthermore, one aspect relates to a quartz glass body obtainable by this process. Furthermore, one aspect relates to a light guide, an illuminant, and a formed body, each of which is obtainable by further processing of the quartz glass body. One aspect additionally relates to a process for the preparation of a silicon dioxide granulate II.

Described is a method of producing synthetic fused silica in which the synthetic flame used in the method has a ratio of the Full Width at Half Maximum (FWHM.sub.vert) vertical luminous intensity to the Full Width at Half Maximum (FWHM.sub.hori) horizontal luminous intensity greater than 10 in a targetless state, the luminous intensities being measured in candela/mm.sup.2.

In a method of manufacturing porous glass base for optical fiber, a liquid organic siloxane raw material stored in a raw material tank of internal pressure P1 is controlled by a mass flow controller at a predetermined flow rate and pumped through pipe of internal pressure P2 to a vaporizer, the liquid raw material is vaporized in the vaporizer and supplied as a gas raw material to a burner, and the silica fine particles formed by burning the gas raw material in the burner are deposited to form a porous glass base material, where P1?P2 is satisfied.

A method for manufacturing quartz glass, wherein (a) an appropriate liquid starting material is evaporated by spraying it into a vertically arranged evaporation chamber, (b) the vaporous starting material is oxidized to form SiO.sub.2, and the SiO.sub.2is collected. The method is characterized in that the starting material to be evaporated is sprayed in on the bottom of the evaporation chamber and the vaporous starting material is removed at the top end of the evaporation chamber, wherein the evaporation chamber is designed such that components depositing in the chamber accumulate on the bottom of the evaporator and are sprayed once again, as well as an evaporator for applying the method.

A method for producing synthetic fused quartz is provided. The method includes evaporating a feedstock material which contains at least one polymerizable polyalkylsiloxane compound, and supplying the feedstock material vapor to a reaction zone, wherein the feedstock material vapor is converted by oxidation and/or by hydrolysis into SiO.sub.2 particles. The feedstock material vapor is passed through a membrane filter as a cleaning device to reduce the formation of gel, which is typically associated with the production of synthetic fused quartz.

An optical fiber with large effective area, low bending loss and low attenuation. The optical fiber includes a core, an inner cladding region, and an outer cladding region. The core region includes a spatially uniform updopant to minimize low Rayleigh scattering and a relative refractive index and radius configured to provide large effective area. The inner cladding region features a large trench volume to minimize bending loss. The core may be doped with Cl and the inner cladding region may be doped with F.

A glass particle deposit producing method capable of preventing the variation in the outside diameter of a glass particle deposit and enhancing the yield of a glass raw material is provided. A glass particle deposit is produced by mounting a starting rod 11 and a glass particle generating burner 22 inside a reaction vessel 2, introducing a glass raw material into the burner 22, subjecting the glass raw material to a flame decomposition reaction inside a flame formed by the burner 22 to generate glass particles, and depositing the generated glass particles on the starting rod 11. At this time, the dispersion angle of the glass raw material jetted from the burner 22 with respect to the center axis of the burner 22 is set to the range of 5 to 70 degrees.

An optical fiber with large effective area, low bending loss and low attenuation. The optical fiber includes a core, an inner cladding region, and an outer cladding region. The core region includes a spatially uniform updopant to minimize low Rayleigh scattering and a relative refractive index and radius configured to provide large effective area. The inner cladding region features a large trench volume to minimize bending loss. The core may be doped with Cl and the inner cladding region may be doped with F.

An optical fiber with large effective area, low bending loss and low attenuation. The optical fiber includes a core, an inner cladding region, and an outer cladding region. The core region includes a spatially uniform updopant to minimize low Rayleigh scattering and a relative refractive index and radius configured to provide large effective area. The inner cladding region features a large trench volume to minimize bending loss. The core may be doped with Cl and the inner cladding region may be doped with F.

A soot glass deposit body is manufactured by placing a starting rod and a burner 22 for producing glass particulates in a reaction container, introducing a source material gas to the burner 22 through a supplying pipe 26, producing glass particulates by a pyrolytic oxidation reaction of the source material gas in a flame formed by the burner 22, and depositing the produced glass particulates on the starting rod. At the time, the source material gas to be supplied to the burner 22 is a siloxane, the burner 22 is heated so that temperature of the burner 22 falls within the range of from 30 C. to +30 C. relative to the boiling point of the siloxane, and also temperature of the supplying pipe is controlled within the range of from the boiling point of the siloxane to the boiling point plus 30 C.