A method of forming an optical fiber preform includes the steps: igniting a burner having a fume tube assembly to produce a first spray size of silicon dioxide particles; depositing the silicon dioxide particles on a core cane to produce a soot blank; and adjusting an effective diameter of an aperture of the fume tube assembly to produce a second spray size of the silicon dioxide particles. The second spray size is larger than the first spray size.

A multiple tube burner for synthesizing a porous material includes three or more glass tubes are arranged coaxially with one another, the glass tubes having a substantially circular shape on a cross section perpendicular to a longitudinal direction. Out of the three or more glass tubes, a first glass tube and a second glass tube that is arranged on an outer side of the first glass tube are connected with each other on a gas introducing side, and a thickness near a joint portion of the second glass tube connected with the first glass tube is thicker than a thickness of the second glass tube on the gas spouting side.

An optical fiber base material manufacturing apparatus including a reaction chamber; a burner that has a portion thereof inserted into the reaction chamber through an insertion opening that creates a connection between the inside and outside of the reaction chamber, and emits a flame toward a starting member positioned within the reaction chamber; and a seal connection member that creates an air-tight seal between the burner and the reaction chamber at the insertion opening. One end of the seal connection member firmly contacts the burner inserted therethrough, another end of the seal connection member firmly contacts the reaction chamber and has a through-hole formed therein through which the burner is inserted without contacting the seal connection member, and the seal connection member includes a connecting portion that connects the one end to the other end, while preventing transfer of stress between the one end and the other end.

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.

An apparatus for manufacturing a porous glass soot body to be formed into an optical fiber preform includes: a reaction chamber; a burner to form the porous glass soot body by depositing glass particles onto a seed rod hung inside the reaction chamber; and a heat-blocking element filling a gap between the burner and an opening for inserting the burner into the reaction chamber. A purpose is to prevent damage to the burner in the apparatus for manufacturing a porous glass soot body. In the manufacturing apparatus, the heat-blocking element may include a fibriform material. Also, in the manufacturing apparatus, the heat-blocking element may include a quartz wool material. Further, in the manufacturing apparatus, the content of iron in the quartz wool material may be 1 ppm or less.

A method for producing a porous glass fine particle body includes: a first layer formation step of continuously forming in a longitudinal direction of a rotating starting base material without a break, a first soot layer on a surface of the rotating starting base material; and an second layer formation step of forming second soot layers on an outside of the first soot layer while supplying a raw material gas to each of a burner among burners of a burner group and moving the burner group in a reciprocating manner in the longitudinal direction relative to the rotating starting base material. The burner group and the starting base material move relatively to each other along the longitudinal direction.

Provided is a glass particulate deposit manufacturing method for manufacturing a glass particulate deposit comprising mounting a fixing jig on an outer periphery of an outermost pipe of a burner; inserting a burner cover from a tip end of the outermost pipe of the burner; and sandwiching and compressing a part of the fixing jig between the burner cover and the outermost pipe of the burner to fix the burner cover to the burner, wherein an outer diameter of a part of the fixing jig that is not compressed is greater than an inner diameter of a part of the burner cover inserted to the tip end of the outermost pipe of the burner.

A method for manufacturing an optical fiber preform includes a core part deposition process and a clad part deposition process. The number of burners used in the core part deposition process is less than the number of burners used in the clad part deposition process. A distance between turning back points in a first reciprocating motion for the core deposition process is equal to or greater than a length of an effective portion of the optical fiber preform. At least three burners are used in the clad part deposition process. A distance between turning back points in a second reciprocating motion for the clad part deposition process is shorter than a distance between turning back points in the first reciprocating motion. The turning back points in the second reciprocating motion vary during the clad part deposition process.

The invention relates to a process for preparing a quartz glass body comprising the process steps i.) Providing a silicon dioxide granulate, ii.) Making a glass melt from the silicon dioxide granulate in a melting crucible, and iii.) Making a quartz glass body from at least a part of the glass melt, wherein the melting crucible is comprised in an oven and is made of at least one material comprising tungsten or molybdenum or a combination thereof. The invention further relates to a quartz glass body which can be obtained by this process. Further, the invention relates to a light guide, an illuminant and a formed body, each of which can be obtained by processing the quartz glass body further.

Provided is a manufacturing method for a porous glass deposit, comprising by depositing glass fine particle onto a starting material being pulled up in a rotating manner within a reaction chamber using a plurality of burners by which glass fine particles are deposited at positions that are different from each other, supplying humidified clean air to the reaction chamber through an air inlet provided on a wall surface of the reaction chamber in a manufacturing process of the porous glass deposit.