A flow rate fluctuation of the liquid raw material of the organic siloxane supplied to the vaporizer is suppressed and a deposition density of the silica fine particles is uniformizes. The method of manufacturing the porous glass base material according to the present invention, a liquid organic siloxane raw material stored in a raw material tank of internal pressure P.sub.1 is controlled by a mass flow controller at a predetermined flow rate and pumped through pipe of internal pressure P.sub.2 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. The present invention is characterized by the method of manufacture described above, wherein P.sub.1≤P.sub.2 is satisfied.

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 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 device for aligning an impact of a tubular preform of an optical waveguide. The device incudes a turning device which rotates the preform about an axis of rotation, a reactive gas supply which supplies a reactive gas to an inside of the preform, a burner device which is movably associated with the preform in a longitudinal direction along the axis of rotation of the preform and which control a temperature of an outer surface of the preform via a coating flame so that the reactive gas is partially deposited from the inside on an inner wall of the preform and melted to form a transparent layer, and an impact correction device having a compressed air device which applies compressed air. The impact correction device is arranged at a first longitudinal distance along the longitudinal direction from the coating flame so that the preform is aligned via the compressed air.

A method for manufacturing a glass ingot includes preparing a supply system including a gasifier that gasifies a raw material compound and a burner that combusts the gasified raw material compound; adding an oxygen-containing gas to the raw material compound at a plurality of addition places including an upstream addition place located in the gasifier or on an upstream side of the gasifier and a downstream addition place located on a downstream side of the gasifier in which locations of the raw material compound in a flow direction are different in the supply system so as to form a raw material mixture; and adding the oxygen-containing gas at the upstream addition place so that a concentration of oxygen or a concentration of the raw material compound in the raw material mixture is not in a combustible range of the raw material mixture.

A method for manufacturing an optical fiber preform including a core part and a cladding part is disclosed. The method includes: adding an alkali metal to an inner surface of a silica-based glass pipe; etching the inner surface of the silica-based glass pipe to which the alkali metal is added; making a glass rod by collapsing the silica-based glass pipe after the etching; and making an optical fiber preform using the glass rod. The silica-based glass pipe is heated in the adding such that a surface temperature of the silica-based glass pipe falls within a temperature range of 1500 C. or higher to lower than 2000 C.

A method of producing bi-modal particles includes the steps of igniting a first precursor gas using a primary burner thereby producing a first plurality of particles of a first size, fluidly transporting the first plurality of particles down a particle tube, igniting a second precursor gas using a secondary burner thereby producing a second plurality of particles of a second size, flowing the second plurality of particles into the first plurality of particles, and capturing the first and second plurality of particles.

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.

A method of producing bi-modal particles includes the steps of igniting a first precursor gas using a primary burner thereby producing a first plurality of particles of a first size, fluidly transporting the first plurality of particles down a particle tube, igniting a second precursor gas using a secondary burner thereby producing a second plurality of particles of a second size, flowing the second plurality of particles into the first plurality of particles, and capturing the first and second plurality of particles.

Provided is an optical fiber containing an alkali metal element or the like having a smaller diffusion coefficient than K and having a low Rayleigh scattering loss. An optical fiber is composed of silica glass and includes a core and a cladding arranged to surround the core which has a lower refractive index than the core. The core includes a first core including a central axis and a second core arranged to surround the first core. The average concentration of an alkali metal element or alkaline-earth metal element in the first core is 10 mol ppm or less. The average concentration of chlorine in the first core is 2000 mol ppm or more. The average concentration of an alkali metal element or alkaline-earth metal element in the second core is 10 mol ppm or more. The average concentration of chlorine in the second core is 10 to 600 mol ppm.