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.

According to a fabrication method for fabricating a porous glass base material for optical fiber, the orientation of a clad forming burner used to form the outermost layer of a clad-corresponding portion is changed further upward while glass fine particles are deposited during the period between a first timing and a second timing. At the first timing, the outer diameter of the porous glass base material for optical fiber has not reached a target outer diameter. The second timing is later than the first timing, and either a timing at which the outer diameter of the porous glass base material for optical fiber reaches the target outer diameter for the first time, or a timing prior to this timing.

Described is a process for the production of synthetic fused silica in which the deposition surface is located for a period of at least 50% of the build-up time of the soot body at a burner distance in which the horizontally integrated luminous intensity of the flame of the burner used in the targetless state is still at least ⅔ of the maximum horizontally integrated luminous intensity of the flame.

This burner for producing a fine glass particle deposited body is provided with a metallic gas-feed pipe that forms a burner body, and a cover for covering the gas-feed pipe, wherein: the gas-feed pipe and the cover are integrally formed; the gas-feed pipe has connected thereto a piping through which material gas, oxyhydrogen gas, and seal gas are supplied; and the cover covers, in the axial direction of the burner over a prescribed length and in a given constant outer diameter, the gas-feed pipe and a connection part of the piping connected to a lateral surface of the gas-feed pipe.

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 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.

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.

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.

This invention provides a manufacturing method for an optical fiber. In this invention, when the core layer loose body and the cladding layer loose body are deposited, the oxyhydrogen flame is used make a temperature of an interface between the core layer and the cladding layer rise, such that silicon dioxide at the interface appropriately contracts to form an isolation layer with a relatively high density. In addition, in this invention, a hollow glass tube is used as a target rod, and the hollow glass tube which is the target rod is directly connected with the core layer loose body. During the subsequent dehydration, not only a dehydration atmosphere penetrates from the outside to the inside of the cladding layer loose body, but also the dehydration atmosphere directly enters the core layer through the hollow glass tube.

This invention provides a manufacturing method for an optical fiber. In this invention, when the core layer loose body and the cladding layer loose body are deposited, the oxyhydrogen flame is used make a temperature of an interface between the core layer and the cladding layer rise, such that silicon dioxide at the interface appropriately contracts to form an isolation layer with a relatively high density. In addition, in this invention, a hollow glass tube is used as a target rod, and the hollow glass tube which is the target rod is directly connected with the core layer loose body. During the subsequent dehydration, not only a dehydration atmosphere penetrates from the outside to the inside of the cladding layer loose body, but also the dehydration atmosphere directly enters the core layer through the hollow glass tube.