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.

An apparatus for manufacturing an optical fiber preform includes: a holding part that rotatably holds a target with a center axis of the target as a rotation axis; a plurality of burner units that are arranged at mutually different positions in a circumferential direction of the target, forms flames for generating glass particles to be deposited on the target, and are capable of performing reciprocating movements along the target in a movable range between a first position on one end side of the target and a second position on the other end side of the target; and a control unit that controls the plurality of burner units so that speeds of return movements of the plurality of burner units that perform the reciprocating movements are different from each other.

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 manufacturing apparatus for an optical fiber porous preform includes a reaction chamber configured to accommodate a starting material; at least one main burner provided in the reaction chamber, the at least one main burner being configured to be supplied with a gas containing at least a source gas and a flammable gas, such that particulates are to be generated from reaction of the source gas and the flammable gas and deposited on the starting material; at least one auxiliary burner configured to be directed toward an end portion of the starting material on which the particulates are to be deposited; and an airflow guide provided such that at least part of the airflow guide is located across the at least one auxiliary burner from the starting material.

An apparatus for manufacturing an optical fiber preform, the apparatus including: a reaction vessel in which an initial substrate is arranged; a burner that can be inserted from an opening of the reaction vessel to spray a glass soot on the initial substrate in the reaction vessel; and a sealing member that has an internal space for accommodating the burner, and is extendable in accordance with a position of the burner and airtightly connects the opening and the internal space.

An optical fiber preform including a glass material and a refractive index adjusting additive is disclosed. This preform has striae due to difference in concentration of the additive and the striae have concentric refractive index periodicity in at least a part thereof from a radial center of the preform to an outer periphery thereof. The respective striae pitches each indicating a period of the refractive index periodicity increase from the center of the preform to the outer periphery thereof.

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.

A method of measuring a diameter of a core portion of an optical fiber preform including the core portion having a relatively high refractive index and a clad portion having a relatively low refractive index. The method includes applying parallel light to the optical fiber preform, and measuring the diameter of the core portion from an image captured by receiving the light having transmitted through the optical fiber preform.

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 of forming an optical fiber preform includes flowing a precursor stream through a burner toward a substrate, the precursor stream comprising a glass precursor gas and a carrier gas, the carrier gas having a kinematic viscosity at 2000 K of greater than 5 cm.sup.2/sec and a ratio of heat capacity to universal gas constant (C.sub.p/R) 2000 K of less than 4; flowing an inflammable gas through the burner; pyrogenically forming glass particles from the glass precursor gas, the pyrogenically forming comprising combusting the inflammable gas; flowing a shield gas through the burner, the shield gas flowing between the precursor stream and the inflammable gas, the shield gas having a kinematic viscosity at 2000 K of greater than 5 cm.sup.2/sec and a ratio of heat capacity to universal gas constant (C.sub.p/R) at 2000 K of less than 4; and depositing the glass particles onto the substrate.