A method for manufacturing an optical fiber preform includes: producing a core preform including a core portion made of transparent glass and a first cladding layer obtained by adding fluorine to the core portion; and forming, on an outer periphery of the first cladding layer, a second cladding layer made of glass having a refractive index higher than that of the first cladding layer. Further, a refractive index profile is formed in the first cladding layer due to a fluorine concentration profile, the refractive index profile being provided at least near a boundary surface with the second cladding layer and having a profile such that a refractive index difference between a refractive index of the first cladding layer and a refractive index of the second cladding layer decreases in accordance with a reduction in a distance from the boundary surface with the second cladding layer.

A method and an apparatus for producing a porous glass preform by using organosiloxane raw material is provided. The apparatus for producing the porous glass preform 12 according to the present embodiment is configured to mix organosiloxane in a liquid state being a raw material with a carrier gas in a vaporizer 6, heat this mixture to be vaporized, supply this vapor to a burner 13 as a gas raw material, and produce a porous glass preform by depositing a glass fine particle produced by combusting the gas raw material on a starting material, herein the apparatus for producing a porous glass preform includes a moisture removing apparatus 8 configured to remove moisture in the carrier gas and supply the vaporizer with the carrier gas.

The invention relates to a method and a device for producing a preform for glass fiber production. The method comprises the steps of providing a carrier gas with a desired, precisely adjusted temperature, loading the carrier gas with halide vapor, mixing the loaded carrier gas with additional gases, and producing the preform in a reaction chamber with substrate.

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.

An aspect of the present disclosure enables prediction of a refractive index profile of a transparent glass preform obtained in a production stage of a glass particulate deposit by a VAD method. The glass preform production apparatus includes a gas supply system, a burner, and a signal processing device. The signal processing device includes an imaging device that images a particle flow of glass fine particles, and a calculation unit. The calculation unit extracts, at any one or more time points during a period from the start of production to the end of production of the glass particulate deposit, image data representing a state of at least the flame or the particle flow from an image obtained by the imaging device, and regressively predicts a refractive index profile of the transparent glass preform serving as an objective variable from an explanatory variable including the image data.

A manufacturing method of a porous glass base material for optical fiber includes: controlling a flow rate of a raw material liquid of an organic siloxane by a liquid mass flow controller; introducing raw material liquid to a raw material liquid nozzle of a vaporizer by a raw material liquid pipe; ejecting raw material liquid into the vaporizer; mixing raw material liquid and carrier gas to vaporize raw material liquid to form mixed gas; supplying mixed gas to a burner; combusting mixed gas together with a combustible gas and a combustion supporting gas in the burner to produce SiO.sub.2 particles; depositing SiO.sub.2 particles on a starting core base material to form the porous glass base material; and closing an open/close valve on a flow path of the raw material liquid pipe to stop supply of raw material liquid, while continuing to supply carrier gas, combustible gas, and combustion supporting gas.

A method and an apparatus for producing a porous glass preform by using organosiloxane raw material is provided. The apparatus for producing the porous glass preform 12 according to the present embodiment is configured to mix organosiloxane in a liquid state being a raw material with a carrier gas in a vaporizer 6, heat this mixture to be vaporized, supply this vapor to a burner 13 as a gas raw material, and produce a porous glass preform by depositing a glass fine particle produced by combusting the gas raw material on a starting material, herein the apparatus for producing a porous glass preform includes a moisture removing apparatus 8 configured to remove moisture in the carrier gas and supply the vaporizer with the carrier gas.

The porous glass base material manufacturing apparatus releases gas of organic siloxane raw materials into the flame of a group of burners that moves relative to a starting base material along the longitudinal direction of the starting base material rotating around a rotation axis along the longitudinal direction to form soot of porous glass particles on the surface of the starting base material. The porous glass base material manufacturing apparatus is equipped with a vaporizer that vaporizes liquid raw materials containing organic siloxane in a liquid state supplied from a raw material tank to make a raw material mixed gas mixed with raw material gas and carrier gas and a raw material gas pipe that supplies the raw material mixed gas to the burner. The raw material gas pipe is insulated and kept warm by double insulation.

A gas branching apparatus that branches and supplies a gas to first to N-th supply targets, includes first to N-th pipes wherein the first to N-th pipes are each branched into first to N-th branch pipes on a downstream end side, and wherein the i-th branch pipes of the respective first to N-th pipes are connected in common to the i-th supply target, and the i-th branch pipes of the respective first to N-th pipes are provided with valves, respectively, where i denotes each of integers of 1 to N.

A manufacturing apparatus of a porous glass base material for optical fiber includes: a liquid mass flow controller for controlling a flow rate of a raw material liquid of an organic siloxane; a vaporizer for mixing the raw material liquid and a carrier gas to vaporize the raw material liquid to form a mixed gas in which a raw material gas and the carrier gas are mixed; a raw material liquid nozzle for ejecting the raw material liquid into the vaporizer; a carrier gas supply pipe for supplying the carrier gas into the vaporizer; a raw material liquid pipe for introducing the raw material liquid into the raw material liquid nozzle; a burner for combusting the mixed gas together with a combustible gas and a combustion supporting gas to produce SiO.sub.2 fine particles; a mixed gas pipe; an open/close valve; and a purge gas supply pipe.