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 the vaporizer and the burner together, in a synchronized manner, parallel to the starting member in a longitudinal direction thereof.

Provided is a method of manufacturing a porous glass deposition body for optical fiber comprising depositing silica powder on a starting member being raised and rotated by using burners with different deposition positions. With a glass raw material flow rate supplied to a core deposition burner represented by F.sub.1 and a total flow rate of glass raw material supplied to a cladding deposition burner adjacent to the core deposition burner represented by F.sub.2, during an initial deposition stage occurring before gas conditions reach a stable state, glass raw material is supplied to points at the same longitudinal position of the deposition body such that a glass raw material flow rate ratio F.sub.2/F.sub.1 is no less than 0.69 and no greater than 1.03.

A method for producing a glass particulate deposit, said method comprising using siloxane as a raw material for glass, discharging the siloxane gasified in a vaporizer and a combustion gas from a burner and combusting, and thus forming a glass particulate deposit in a reaction vessel, wherein: after producing a good section of the glass particulate deposit, the supply of the siloxane that is the raw material for glass to the burner is ceased while continuously supplying the combustion gas to the burner; then the glass particulate deposit is taken out from the reaction vessel; a raw material gas port from the vaporizer to the burner is purged by flowing an inert gas therethrough; and, when a color derived from the combustion of the siloxane gas is not observed any more in the flame of the burner, then the supply of the combustion gas is ceased.

A manufacturing method of a porous glass base material for optical fiber includes: supplying an organic siloxane raw material supplied from a raw material tank is fed to a vaporizer; mixing and vaporizing the raw material and carrier gas in the vaporizer; and externally depositing SiO.sub.2 fine particles through combustion reaction by supplying the mixed gas of raw the material and the carrier gas to the burner in the manufacturing apparatus of porous glass base material for optical fiber. Before starting to supply the raw material to a raw material gas supply pipe of the burner, the burner and the inside of a manufacturing apparatus of porous glass base material for optical fiber are pre-heated by flowing purge gas of 60° C. or higher into the raw material gas supply pipe and supplying combustible gas and combustion supporting gas to the burner.

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.

A manufacturing method of an optical fiber preform used to produce an optical fiber includes: etching a surface of a core preform that forms a core of the optical fiber with a plasma flame in a chamber; obtaining a porous preform by depositing glass particles on an etched surface of the core preform to form an outside vapor-deposited layer that forms a cladding of the optical fiber in a state where the core preform is put into the chamber; and heating and sintering the porous preform. When obtaining the porous preform, the outside vapor-deposited layer is formed by repeatedly performing the deposition of the glass particles multiple times through supply of source material gas. In a first deposition among the multiple times of deposition of the glass particles, a flow rate of the source material gas is less than or equal to 50% of a stable value.

A method for manufacturing a glass preform, the method having: a depositing step for installing a starting rod and a burner for generating glass fine particles in a reaction container, introducing a siloxane as a glass raw material to the burner, oxidizing the glass raw material in a flame formed by the burner and generating glass fine particles, depositing the generated glass fine particles on the starting rod and fabricating a glass fine particle deposited body; and a transparentizing step for heating the glass fine particle deposited body and manufacturing a transparent glass preform, wherein, after the depositing step, the transparentizing step is performed after the glass fine particle deposited body is heated for a time range of one to eight hours in an oxygen-containing atmosphere at a temperature lower than the temperature of the transparentizing step.

A method of manufacturing an optical fiber glass preform, the method comprising depositing glass particles on a base material, the glass particles being generated by glass making feedstock gas being supplied while a burner and the base material that is rotating are reciprocated relatively to each other, wherein when a portion corresponding to an outer diameter equal to or more than 0.80 L and equal to or less than L is deposited, wherein L represents a final outer diameter of a part of the optical fiber glass preform manufactured, the part being formed by the deposition of the glass particles, the deposition is performed under a first condition where an angle formed by a first line extending from a center O of a cross section of the base material to a rotational position r0 at which one round trip of the relative reciprocation starts and a second line extending from the center O to a rotational position r1 at which the one round trip of the relative reciprocation ends is an angle excluding 0, 120, 240, 72, 144, 216, and 288; or the deposition is performed under a second condition where the angle is 120 or 240, thereby to deposit the glass particles to a thickness corresponding to a thickness equal to or less than 0.03 L; or the deposition is performed under a third condition where the angle is 72, 144, 216, or 288, thereby to deposit the glass particles to a thickness corresponding to a thickness equal to or less than 0.02 L; or the deposition is performed under a fourth condition where the angle is 0, thereby to deposit the glass particles to a thickness corresponding to a thickness equal to or less than 0.01 L.

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.

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.