A method of manufacturing a porous glass preform includes depositing glass particles on an outer periphery of a target rod while a burner for synthesizing glass particles and the target rod that is rotating are relatively reciprocated, wherein V and r are gradually reduced while a variation in sweeping pitch P [mm] expressed as V/r is caused to be within a range of a central value±10% when a glass particle deposition layer of a portion satisfying a relation 0.5L≦R≦0.8L is synthesized; where a final outer diameter of the manufactured porous glass preform for an optical fiber is L [mm], an outer diameter of a glass particle deposition body in the middle of the manufacture is R [mm], a rotating speed of the target rod is r [rpm], and a relative moving speed between the target rod and the burner is V [mm/min.].

A method of manufacturing a porous glass preform includes depositing glass particles on an outer periphery of a target rod while a burner for synthesizing glass particles and the target rod that is rotating are relatively reciprocated, wherein V and r are gradually reduced while a variation in sweeping pitch P [mm] expressed as V/r is caused to be within a range of a central value±10% when a glass particle deposition layer of a portion satisfying a relation 0.5 L≤R≤0.8 L is synthesized; where a final outer diameter of the manufactured porous glass preform for an optical fiber is L [mm], an outer diameter of a glass particle deposition body in the middle of the manufacture is R [mm], a rotating speed of the target rod is r [rpm], and a relative moving speed between the target rod and the burner is V [mm/min.].

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.

A method of manufacturing synthetic quartz glass through an outside vapor deposition (OVD) process with improved deposition efficiency. When a hollow cylindrical synthetic quartz glass product is manufactured through an OVD method or the like, it is environmentally friendly in view of using a smaller amount of chlorine and is economical in view of requiring no separate treatment equipment, as compared to a conventional technique using silicon chloride (SiCl.sub.4). Also, the method, in which octamethylcyclotetrasiloxane is supplied to a deposition burner while being sprayed in the form of a droplet along with a high-pressure carrier gas and vaporized by the deposition burner, can effectively address the high-temperature heating and slow decomposition involved when octamethylcyclotetrasiloxane ([(CH.sub.3).sub.2SiO].sub.4) is used as a source for depositing silicon dioxide particles.

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 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.

A method is provided that includes: forming a low-index trench region with a first density; forming an inner barrier layer comprising silica around the trench region at a second density greater than the first density; depositing silica-based soot around the first barrier layer to form an overclad region at a third density less than the second density; inserting a core cane into a trench-overclad structure; forming an outer barrier layer comprising silica in an outer portion of the overclad region at a fourth density greater than the third density; flowing a down dopant-containing gas through the trench-overclad structure to dope the trench region with the down dopant, and wherein the barrier layers mitigate diffusion of the down-dopant into the overclad region; and consolidating the trench-overclad and the core cane.

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.

In a device for producing a large-sized porous base material by a VAD process, the cracking and variation of the outer diameter of the base material are suppressed by forming a smooth tapered part, without changing the length of a non-effective part. In producing the porous base material by a VAD process, the time for a gas to reach a flow amount of the gas in a steady state from starting of the deposition is extended more in a burner that deposits glass microparticles on a layer closer to the outside of the base material.

A deposition system for depositing a chemical vapor onto a workpiece is disclosed, including a deposition chamber having a plurality of components for performing chemical vapor deposition on the workpiece. The workpiece is held by a lathe that rotates the workpiece relative to chemical burners that deposit silica soot on the workpiece. The deposition system has a gas panel for regulating the flow of gases and vapors into the deposition chamber, and a computer for controlling operation of the gas panel and the components in the deposition chamber. Multiple sets of chemical burners are disposed longitudinally along the length of the workpiece. Each set of burners is separated from other sets, such that each set of burners deposit silica particles onto generally different portions of a workpiece. The respective portions include an overlap segment in which one or more burners from one burner set will deposit silica particles on the same portion of the workpiece as one or more burners from another set.