A method of producing an optical fiber preform includes a silica glass body forming step of forming a silica glass body to be at least a portion of a core portion. The method includes an alkali-metal-doped silica glass body forming step of forming an alkali-metal-doped silica glass body doped with an alkali metal around the silica glass body such that the alkali-metal-doped silica glass body contacts the silica glass body. The method further includes a diffusing step of diffusing the alkali metal from the alkali-metal-doped silica glass body to the silica glass body by a heat treatment.

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

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 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.

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.

The present invention relates to a method for manufacturing a preform of silica for optical fiber production, as well as to a method for the production of optical fibers comprising a step of drawing the optical fiber from such a preform of silica, the method comprising a step of vaporization of a siloxane feedstock added with a compound having the following formula (I): wherein R, R′ and R″, equal or different each other, are an alkyl group having from 1 to 5 carbon atoms, and A is a saturated or unsaturated chain of atoms selected from the group consisting of carbon atom, nitrogen atom, and oxygen atom, said chain A forming with the nitrogen atom linked thereto a saturated, unsaturated or aromatic heterocyclic moiety. ##STR00001##

An optical fibre, for use in the field of distributed measurement of temperature or deformation by optical reflectometry in the frequency domain using the Rayleigh backscattered signal in the fibre, includes a core doped with nanoparticles for example formed from gold particles covered with zirconium oxide, and can be subjected to high temperatures during the measurement. A method for producing the optical fibre includes a step of heat treatment during which the optical fibre is subjected, for a duration of at least one hour, to a heat treatment temperature higher than a maximum temperature to which it will be subjected during a measurement.

An optical fiber with low attenuation and methods of making same are disclosed. The optical fiber has a core, an inner cladding surround the core, and an outer cladding surrounding the inner cladding. The outer cladding is chlorine-doped such that the relative refractive index varies as a function of radius. The radially varying relative refractive index profile of the outer cladding reduces excess stress in the core and inner cladding, which helps lower fiber attenuation while also reducing macrobend and microbend loss. A process of fabricating the optical fiber includes doping an overclad soot layer of a soot preform with chlorine and then removing a portion of the chlorine dopant from an outermost region of the overclad soot layer. The soot preform with the modified chlorine dopant profile is then sintered to form a glass preform, which can then be used for drawing the optical fiber.