Abstract: To provide an apparatus for manufacturing a glass particles deposit in which it is possible to effectively prevent the foreign matter from being deposited on or mixed into the glass particles deposit during the manufacturing operation. The apparatus for manufacturing the glass particles deposit comprises an upper funnel, a reaction vessel and a lower funnel, wherein the glass particulates are deposited around the outer circumference of a starting rod supported by a support rod within the reaction vessel while the starting rod is being rotated around its axis and reciprocated up and down, characterized in that a sleeve made of quartz separating an inner wall of the reaction vessel and a central rotation member is installed inside the reaction vessel.

Abstract: The present invention provides a method for manufacturing a glass particles deposit body that is formed on the periphery of a starting rod by an OVD method, whereby an optical fiber with enhanced optical transmission characteristics can be produced by reducing the number of disconnections and preventing the alien substances from being mixed into the glass particles deposit body. This invention involves the use of the OVD method in which (1) before or after starting to deposit fine glass particles, a reaction vessel is enclosed to suck and exhaust a gas within the reaction vessel after a removal operation of deposited fine glass particles from the inside of the reaction vessel, (2) when not in operation, a purge gas is passed at a flow rate of 1 m/min or more through each gas line of a burner, (3) when not in operation, a clean air (CA) is introduced into the reaction vessel to make the inner pressure of vessel positive, or (1) and (2) or (1), (2) and (3) are combined.

Abstract: The present invention provides methods for fabricating optical fiber preforms and optical fibers. According to one embodiment of the invention, a method for making an optical fiber preform includes the steps of providing at least one sacrificial rod having an outside surface; forming a material on the outside surface of each sacrificial rod to yield a structured body, the structured body including a structured material in substantial contact with the at least one sacrificial rod; removing each sacrificial rod from the structured body; and including the structured body in the optical fiber preform. The preform may be drawn into an optical fiber. The methods of the present invention are especially useful in the fabrication of microstructured optical fibers.

Abstract: The present invention is directed to methods of producing soot used in the manufacture of optical waveguides. Both non-aqueous liquid reactants and aqueous solutions containing one or more salts are delivered through an atomizing burner assembly to form a homogenous soot stream containing the oxides of the selected elements contained within the non-aqueous liquid reactant and the aqueous solution. The resulting multi-component soot is collected by conventional methods to form preforms used in the manufacture of optical waveguide fibers. Preforms formed by the methods are also disclosed.

Abstract: An object of the present invention is to reduce the adhesion of floating glass particulates to the surface of a soot preform during the manufacture of the soot preform, thereby reducing the voids generated in the transparent glass preform made from the soot preform, and to improve the quality of the optical fiber manufactured from the transparent glass preform. The equipment of the invention is equipped with a reaction vessel 1, a burner 2 provided within the reaction vessel 1 into which raw material gas and combustion gas are supplied so as to generate glass particulates by hydrolysis reaction, and a starting rod 5 onto which the glass particulates generated by the burner 2 are deposited. By drawing up the starting rod 5 while turning it around its axis, the glass particulates are deposited on the tip of or around the starting rod 5 to form a soot preform 6 in column-like shape.

Abstract: Methods and apparatus for producing fused silica members having high internal transmission are disclosed. The apparatus and methods are capable of producing fused silica having internal transmission of at least 99.65%/cm at 193 nm.

Abstract: An apparatus for manufacturing a glass base material, which is a base material of an optical fiber, comprising: a base rod, around and along which said glass base material is formed; a burner that hydrolyzes and accumulates a gas material, which is a base material of said glass base material, around and along said base rod; a first burner-moving-unit that moves said burner in a direction parallel with a longitudinal direction of said base rod; and a second burner-moving-unit that moves said first burner-moving-unit in a same moving direction of said first burner-moving-unit.

Abstract: The present invention is directed to a method and apparatus for forming soot used in making glass, and in particular, optical waveguides. A liquid precursor (66) is first fed into orifice (52) of a liquid orifice insert (48) within an injector (44) positioned within an atomizing burner assembly, and is thereafter discharged from the injector into a pressurization chamber (56). An atomization gas (70) is also fed into the pressurization chamber (56) to mix with the liquid precursor liquid stream (68) which breaks into droplets (76). The liquid precursor and atomization gas arm forced under pressure out of an atomization orifice (32) on the face of the burner (30) assembly. Flame gas (74), reaction gas (84) and shield gas (82) are ejected from burner orifices (40, 38, 36 and 34) to produce the flame.

Abstract: Methods and apparatus for adding metals such as aluminum to fused silica glass articles are disclosed. The methods and apparatus allow for controlled, low level addition of metals into fused silica glass articles. The fused silica glass articles containing added aluminum exhibit improved internal transmission and decreased absorption change when irradiated with a laser.

Abstract: A silica glass member for use with a light having a specific wavelength of 250 nm or shorter, in which the difference in the maximum and the minimum values of hydroxyl group concentration as measured in a plurality of points within a plane vertical to an optical axis whose center is the crossing point of its optical axis with the optical axis of the silica glass member is 50 ppm or lower; and in which the plurality of signed birefringence values obtained based on the birefringence values measured on several points within a plane vertical to an optical axis whose center is the crossing point of its optical axis with the optical axis of the silica glass member and the direction of the fast axis fall within a range of from −2.0 to +2.0 nm/cm. Thus, a silica glass member having high optical transmittance and a high resistance against ultraviolet radiations is provided.

Abstract: A method for manufacturing a glass preform includes supplying a first gaseous or vapor phase composition to a reaction chamber; supplying water as a second gaseous or vapor phase composition to the reaction chamber; reacting the water and the first gaseous or vapor phase composition to form an aerosol of glass particles; directing the aerosol along the reaction chamber, out of the reaction chamber, and toward a target; and depositing glass particles of the aerosol onto the target. The first gaseous or vapor phase composition is disposed to provide a hydrolyzable glass precursor. Walls of the reaction chamber have a temperature gradient in which a temperature of the walls increases in a direction of flow of the aerosol along the reaction chamber. Alternatively, a flow of the aerosol along the reaction chamber has a temperature gradient in which a temperature of the aerosol increases in the direction of flow.

Abstract: An apparatus for the production of a porous optical fiber preform preventing cracks in the preform and stabilizing quality over the longitudinal direction. The apparatus includes a reaction portion, a feed port for introducing a stream of gas, and a main exhaust port. A rotating mechanism is provided for mounting, rotating, and pulling up a seed rod for forming the porous optical fiber preform. A first burner emits a flame carrying fine particles of glass forming the core portion, and a second burner emits a flame carrying fine particles of glass forming the cladding portion. A portion adjusts the flow of the stream from the feed port to the main exhaust port so that the flames carrying the glass particles are not disturbed by the stream and so that the stream does not directly contact a fine glass particle deposit formed at a bottom end of the seed rod.

Abstract: A method and apparatus for manufacturing optical components. A burner generates soot, and a surface area collector collects the soot. The burner is disposed such that the soot collected within the surface area collector is substantially not reheated by subsequently deposited soot. Magnetic forces direct the soot to desired location(s) within the surface area collector. The surface area collector operates at relatively low temperatures sufficient to retain rather volatile substances, such as fluorine, in the soot.

Abstract: An optical fiber is formed by performing vapor phase deposition of SiO2 on the outside of a glass rod comprising a core section and a first cladding section and drawing a glass preform which formed by a second cladding section. Also, a single mode optical fiber is manufactured so that the ratio of the diameter D of the first cladding section and the diameter d of the core section is in a range of 4.0 to 4.8, and OH concentration is 0.1 ppm or less. Also, an optical fiber is manufactured so that a value of D/d>4.8, and the OH concentration is 0.1 ppm or less. It is thereby possible to maintain an initial loss in the 1380 nm wavelength range even if hydrogen diffusion occurs.

Abstract: An article of relatively pure silica, and a furnace and method of producing the article. The article is produced by collecting molten silica particles in a refractory furnace in which at least a portion of the refractory has been exposed to a halogen-containing gas to react with contaminating metal ions in the refractory.

Abstract: A method for manufacturing optical fiber preform and fiber. According to the method, a core cane segment is formed with a refractive index delta preferably between 0.2% and 3% that is most preferably formed by an OVD method. A sleeve is formed including at least one down-doped moat preferably having a refractive index delta between −0.1% and −1.2% and at least one up-doped ring preferably having a refractive index delta between 0.1% and 1.2%. The sleeve is formed by introducing glass precursor and dopant compounds into a cavity of a preferably silica glass tube (e.g., one of an MCVD and PCVD method). The core cane segment is inserted into the sleeve and the sleeve is collapsed onto the core cane segment to form a core-sleeve assembly. The core-sleeve assembly is again drawn into a cane and additional cladding is preferably formed thereon. Optical fiber may be drawn from the preform in a conventional draw apparatus.

Abstract: An object of the present invention is to provide a method and apparatus for producing a glass particles deposit in which a soot body having less fluctuation in the outer diameter in a longitudinal direction can be produced without increasing an ineffective portion formed at an end portion of the soot body.

Abstract: An object of this manufacturing method for an optical fiber preform is to provide an optical fiber preform which has no defects such as shearing and stripping between the core and the cladding region. The above object can be achieved by providing the manufacturing method for optical fiber preform, involving depositing glass particles in the radial direction on an outer peripheral portion of a cylindrical starting material provided with glass material which forms a core, thereby forming a porous layer to form an optical fiber precursor porous material, and sintering the porous material to manufacture an optical fiber preform, wherein a heating step for heating the surface of the starting material is provided adjacently before a step for forming the porous layer.

Abstract: Provided are a process for producing an optical fiber preform by depositing glass soot on the periphery of a glass rod and then sintering the glass soot to form a new transparent glass layer and also a process for producing an optical fiber preform by repeating the above procedures, wherein bubble is prevented from occurring in glass layers and interfaces between them. The process includes the steps of forming a glass soot layer by depositing glass soot on the periphery of a glass rod formed by undergoing a sintering heat treatment; and carrying out subsequently another heat treatment for the glass soot to carry out sintering thereof and transform the glass soot layer into a glass layer; wherein, provided that the glass soot is treated at a sintering temperature T′(° C.) and that the glass rod is formed at a sintering temperature T(° C.

Abstract: Three or more glass particle synthesizing burners are arranged to be opposed to a rotating glass rod. The glass rod and the glass particle synthesizing burners are reciprocated in parallel and relatively to deposit glass particles synthesized by the burners on the surface of the glass rod, thereby producing a soot body. The glass particle synthesizing conditions of the burners arranged at both ends are changed to have a greater deposition amount of glass particles per unit time in part or all of its movement range than other burners.

Abstract: A method is disclosed for fabricating a preform suitable for use in manufacturing a wide bandwidth multi-mode optical fiber. The method includes steps of employing a liquid phase spray pyrolysis technique for generating silica soot at a high rate, in combination with a non-chlorine containing liquid silica precursor and a refractory, index of refraction raising additive that overcomes the problems inherent in the use of germanium-based chemistry at typical sintering temperatures. The refractory, index of refraction raising additive is preferably comprised of a Group VB element oxide, such as a tantalum oxide. The liquid precursor is preferably comprised of a polymethylsiloxane, such as hexamethyl di-siloxane, octamethylcyclotetrasiloxane (OMCCTS), or tetramethylcyclotetrasiloxane.

Abstract: A method for producing an optical fiber preform starting with a first-generation target typically comprising pure silica. A plasma torch deposits an annular region of doped silica to form an intermediate structure. The intermediate structure is drawn down to a second-generation target and another annular region of doped silica is deposited. The process is repeated a plurality of times until an Nth generation target is formed. The deposition optionally employs repeated cycles of depositing a plurality of layers of silica at a high traversal rate without sintering, followed by periodic sintering. In a further embodiment, stabilizer bars extending out from the plasma coils improve distribution of the deposition material. Another embodiment injects the source gas into a particular region of the plasma for control of soot deposition.

Abstract: A method of manufacturing an optical fiber preform (3) comprising: forming at least one silica-based outer deposition layer (23) by depositing silica on a primary preform (24) constituted by a bar mainly comprising silica and including a silica-based outer peripheral portion (22), the method being characterized in that the viscosity of the outer deposition layer (23) is adjusted to be substantially identical to the viscosity of the outer peripheral portion (22) of the primary preform (24) by adding to the silica, over a substantial portion of the outer deposition layer (23), at least one compound selected from the group formed by the following compounds: CaF2, MgF2, AlF3, B2O3, and Al2O3.

Abstract: In a known procedure for manufacture of a quartz glass body, a glass starting material and fuel gas are fed to a rotationally symmetrical deposition burner (1) having several annular gap nozzles (7-9) and being formed by coaxial arrangement of a number of quartz glass tubes (2-5), such glass starting material in a burner flame forming SiO2 particles which, under back and forth motion of the deposition burner (1) along the longitudinal axis of a rotating mandrel (12), are deposited on such rotating mandrel under formation of an essentially cylindrical porous blank. To enable replacement of such deposition burner without major efforts in terms of work and costs, the procedure of the inventioin proposes to use a deposition burner (1) the annular gap nozzles (7- 9) of which have gap widths with a maximum dimensional deviation of 0.

Abstract: Natural or synthetic silica is deposited on a preform set into rotation in front of a plasma torch which moves back and forth substantially parallel to a longitudinal direction of the preform, a first feed duct feeds the plasma with grains of natural or synthetic silica while a second feed duct feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas. Any sodium or lithium contained in the grains of natural or synthetic silica react with the fluorine or chlorine of the fluorine or chlorine compound, thereby making it possible to improve the optical quality of fibers drawn from a preform built up with natural or synthetic silica, and to do so at reduced cost.

Abstract: In an apparatus for producing glass particles deposit according to the present invention, a plurality of glass particle synthesis burners are placed on a front face of a reaction vessel, and at least one exhaust port is provided on a rear face of the reaction vessel. Two wall faces extending from both sides of the exhaust port and being in contact with two side faces of the reaction vessel are provided so that its contained angle is 90 degrees or less. Assuming that the shorter distance between the shortest distance from a rotation axis of a target rod to the side face of the reaction vessel and the shortest distance from the rotation axis of the target rod to the wall face is L, and the outer diameter of the glass particles deposit deposited on the target rod is d, L is greater than d.

Abstract: A method for producing an optical quartz glass for use in excimer lasers, comprising a step of forming a porous silica preform by depositing silica in a soot-like form formed by flame hydrolysis of a high-purity volatile silicon compound, followed by a step of vitrifying said porous silica preform into transparent glass in an atmosphere containing water vapor and hydrogen, and a vertical type heating furnace for carrying out the production method therein.

Abstract: Device and method for chemical deposition on an elongated member of vitreous material in which a rotating gripping member causes a first end portion of the elongated member to rotate. The second end portion of the elongated member is borne by a pair of supporting members which are axially spaced apart (L1) and are capable of permitting angular rotational movement and axial sliding of the second end portion. Each supporting member also applies a radial constraint preventing the second end portion from moving away from the axis of rotation, thus forcing the second portion and the elongated member to lie with a longitudinal axis coaxial with the axis of rotation. Any curvature of the elongated member is corrected and recovered in this way.

Abstract: This invention relates to production of high purity fused silica glass doped with titania using titanium chelates. Useful chelates include titanium acetylacetonate, and titanium ethyl acetoacetate among others.

Abstract: A method for making silica includes delivering a silica precursor comprising a pseudohalogen to a conversion site and passing the silica precursor through a flame to produce silica soot.

Abstract: The present invention discloses novel methods for fabricating optical fiber glass preforms which may contain alumina, germania, erbium, or other rare earth metals as dopants. Doping with a higher concentration of alumina enhances the solubility of the erbium, or other rare earth, dopant within the glass and the resultant optical properties of the fiber. However, the addition of an alumina dopant can cause processing difficulties due to the formation of inclusions, such as gas bubble, seeds or crystallite formation, within the glass preform or glass cane. The present invention overcomes these processing difficulties and produces glass preforms or canes that are inclusion-free.

Abstract: The invention relates to a procedure for manufacture of a quartz glass body by deposition of SiO2 particles on the outer surface of a cylindrical mandrel rotating around its longitudinal axis under formation of an essentially cylindrical porous blank with an inside bore hole, and by removing the mandrel and sintering of the blank, characterized in that the mandrel in the area of one of the ends of the successively forming blank is surrounded by a shaping element rotating at the same rotation velocity as the mandrel, such shaping element having a core area facing the blank which is at least partially removably embedded into the front face of the successively forming blank and which is removed before sintering after having widened the inside bore hole of the blank with a shape complementary to that of the core area.

Abstract: The invention provides a low cost method of manufacturing high capacity preforms by chemical vapor deposition. More particularly, there is described a method of manufacturing an optical fiber preform, which method comprises the steps of providing a substrate tube of silica doped with sufficient chlorine to obtain an OH concentration of less than 100 ppb and doped with sufficient fluorine proportional to the chlorine doping to obtain a refractive index that is lower than that of a natural silica, depositing inner cladding and an optical core inside the substrate tube, collapsing the substrate tube to form a primary preform, and depositing outer cladding of said natural silica on the resulting primary preform. The invention is applicable to manufacturing optical fibers.

Abstract: In a method of manufacturing a porous glass preform for an optical fiber which preform is formed as a deposit of fine glass particles by using a burner, a method to prevent the contamination of any glass particles having failed to be properly deposited so that the generation of voids may be minimized in a transparent glass preform which is produced by heating the porous glass preform. An inert gas is caused to flow through the burner at a rate of at least 25 m/s before fine glass particles are formed by the hydrolysis and/or oxidation of a glass material in a flame produced by the burner supplied with a mixture of a gas of the glass material and a gas for combustion and are deposited on a rotating starting member. It is desirable to elevate the pressure of the inert gas above the atmospheric pressure by a device connected to the burner by a pipeline, and cause it to flow rapidly through the burner.

Abstract: In a known procedure for manufacture of a quartz glass body, a glass starting material and fuel gas are fed to a rotationally symmetrical deposition burner (1) having several annular gap nozzles (7-9) and being formed by coaxial arrangement of a number of quartz glass tubes (2-5), such glass starting material in a burner flame forming SiO2 particles which, under back and forth motion of the deposition burner (1) along the longitudinal axis of a rotating mandrel (12), are deposited on such rotating mandrel under formation of an essentially cylindrical porous blank. To enable replacement of such deposition burner without major efforts in terms of work and costs, the procedure of the invention proposes to use a deposition burner (1) the annular gap nozzles (7-9) of which have gap widths with a maximum dimensional deviation of 0.

Abstract: Disclosed is a method of making an optical fiber preform having at least one annular region of depressed refractive index. A tube of silica doped with fluorine and/or boron is overclad with silica soot. A core rod is inserted into the overclad tube and the resultant assembly is heated while chlorine flows between the tube and the core rod to clean the adjacent surfaces. When the soot sinters, the tube collapses onto and fuses to the rod. The resultant tubular structure is formed into an optical fiber which exhibits low attenuation as a result of the low seed count at the interface between the inner core and the region that is doped with florine and/or boron.

Abstract: Fused silica created by pyrolysis of SiCl4 are introduced in a powder state into a vacuum chamber. Pluralities of jet streams of fused silica are directed towards a plurality of heated substrates. The particles attach on the substrates and form shaped bodies of fused silica called preforms. For uniformity the substrates are rotated. Dopant is be added in order to alter the index of refraction of the fused silica. Prepared soot preforms are vitrified in situ. The material is processed into quartz tubes for fiber optics and other applications, quartz rods for fused silica wafers for semiconductors and various optical applications and quartz plates for wafer processing and optical windows.

Abstract: A method for producing an optical fiber preform is provided in which the variation of the outer diameter in the longitudinal direction is minimized and a target quantity of glass is accumulated as a whole. Based on a predetermined relationship between three variables: the outer diameter of a starting rod being a first variable, the outer diameter of an optical fiber preform a second variable, and the timing for ending the glass particles depositing process a third variable, the starting rod and burners are subjected to relative reciprocating movement so as to deposit glass particles on the starting rod until the timing for ending the depositing process, and then the resulting deposit body is vitrified. The third variable may be the traverse velocity, the glass particles deposition time, or the weight of a soot glass deposit body.

Abstract: A method of manufacturing synthetic silica glass includes the steps of pressurizing a liquid storage tank including a liquid silicon compound therein, generating bubbles in the liquid silicon compound using a foamer, removing the bubbles using a degassed, displacing the liquid silicon compound into a vaporizer while controlling an amount of the liquid silicon compound displaced by a liquid mass flow meter, mixing the displaced liquid silicon compound with a carrier gas to generate a gaseous silicon compound, injecting the gaseous silicon compound into a synthesis furnace, and forming synthetic silica glass by hydrolyzing the gaseous silicon compound in the synthesis furnace.

Abstract: A method for preparing high-purity, bulk fused silica includes supplying silane gas, a gaseous fuel, and oxygen gas to a combustion burner. Silica particles are formed by passing the silane gas into a flame formed by the combustion reaction of the gaseous fuel with the oxygen gas while maintaining the ratio of the flow rate of the gaseous fuel to the flow rate of the silane gas no less than twelve and the ratio of the flow rate of the gaseous fuel to the flow rate of the oxygen gas no less than three. The silica particles formed are immediately deposited onto a hot bait to form a boule.

Abstract: A method is provided for manufacturing a silica glass that is substantially free of chlorine. The method includes the step of separately expelling a silicon tetrafluoride gas, a combustion gas, and a combustible gas from a burner made of silica glass, the flow velocity of the silicon tetrafluoride gas being within the range of about 9 slm/cm2 to about 20 slm/cm2. The method further includes the steps of producing minute silica glass particles by reacting the silicon tetrafluoride gas with water produced by a reaction of the combustion gas with the combustible gas, depositing the minute silica glass particles on a target, and producing the silica glass by fusing and vitrifying the minute silica glass particles deposited on the target.

Abstract: A synthetic silica glass having a high transmittance for vacuum ultraviolet rays, for example F2 excimer laser beam with a wavelength of 157 nm, a high uniformity and a high durability and useful for ultraviolet ray-transparent optical glass materials is produced from a high-purity silicon compound, for example silicon tetrachloride, by heat treating an accumulated porous silica material at a temperature not high enough to convert the porous silica material to a transparent silica glass in an inert gas atmosphere for a time sufficient to cause the OH groups to be condensed and removed from the glass, and exhibits substantially no content of impurities other than OH group a difference between highest and lowest fictional temperatures of 50° C.

Abstract: An apparatus for producing a glass soot includes a first a burner having a droplet-emitting first region, a gas-emitting second region surrounding the first region, and a gas-emitting third region surrounding the second region. The first region emits a glass-forming mixture, the second region emits an inert gas, and the third region emits a combination of oxygen and a combustible gas. The apparatus further includes a combustion area having a first section proximate the first burner and a second section distal from the first burner. A glass-forming mixture is at least partially vaporized in the first section of the combustion area. The apparatus further includes at least one secondary burner having gas-emitting fourth and fifth regions. The fourth region of the secondary burner emits oxygen and the fifth region of the secondary burner emits a combustible gas.

Abstract: There is disclosed a method for producing a synthetic fused silica member comprising vaporizing a raw material silane compound, hydrolyzing or oxidizing by combustion the vaporized silane compound in oxyhydrogen flame to form silica microparticles so that the silica microparticles should deposit on a rotating refractory carrier, and melting the silica microparticles during the deposition to form the synthetic fused silica member, wherein sulfur impurities are preliminarily removed from the raw material.

Abstract: A method of manufacturing synthetic silica glass includes the steps of pressurizing a liquid storage tank including a liquid silicon compound therein, generating bubbles in the liquid silicon compound using a foamer, removing the bubbles using a degasser, displacing the liquid silicon compound into a vaporizer while controlling an amount of the liquid silicon compound displaced by a liquid mass flow meter, mixing the displaced liquid silicon compound with a carrier gas to generate a gaseous silicon compound, injecting the gaseous silicon compound into a synthesis furnace, and forming synthetic silica glass by hydrolyzing the gaseous silicon compound in the synthesis furnace.

Abstract: A hooded glass particulate synthesizing torch, provided with at least a glass particulate synthesizing torch body having a feedstock gas injection passage formed at the center of its front end, a combustible gas injection passage formed concentrically at the outer circumference of the feedstock gas injection passage, and a plurality of small diameter combustion aid gas injection passages formed in the combustible gas injection passage along the outer circumference of the feedstock gas injection passage and a hood projecting out at the outer circumference of the front end of the torch body, the torch hood satisfying 0.5≦D/L≦2.0, where, L is the focal distance, that is, a distance from a point P, to which the small diameter combustion aid gas injection passages are directed and on an extension of the center line of the torch body in front of the torch body, to the front end of the torch body, and D is the hood length, that is, the distance from the front end of the hood to the front end of the torch body.

Abstract: In a method of manufacturing a porous glass preform for an optical fiber which preform is formed as a deposit of fine glass particles by using a burner, a method to prevent the contamination of any glass particles having failed to be properly deposited so that the generation of voids may be minimized in a transparent glass preform which is produced by heating the porous glass preform. An inert gas is caused to flow through the burner at a rate of at least 25 m/s before fine glass particles are formed by the hydrolysis and/or oxidation of a glass material in a flame produced by the burner supplied with a mixture of a gas of the glass material and a gas for combustion and are deposited on a rotating starting member. It is desirable to elevate the pressure of the inert gas above the atmospheric pressure by a device connected to the burner by a pipeline, and cause it to flow rapidly through the burner.

Abstract: In a process for producing an optical fiber preform, a starting member and a glass synthesizing burner are reciprocated relative to each other so that fine glass particles synthesized with the burner are deposited layer by layer on the starting member, and a heating power of the glass synthesizing burner in a nonsteady outside diameter portion at either end of the soot preform is adjusted to control the temperature of the nonsteady outside diameter portion at either end against local elevation. The starting member is formed of a transparent glass rod that is held within a vessel and rotatable about its own axis, the burner is fitted on a lateral side of the vessel at right angles to the rotating axis of the starting member and is movable towards or away from the starting member.

Abstract: In a known process for the manufacture of an elongated porous SiO2 preform, SiO2 particles are deposited on the mantle surface of a cylindrical carrier rotating about its longitudinal axis. The SiO2 particles are formed by means of a plurality of deposition burners which are arranged, at a distance from one another, in at least one burner row extending parallel to the longitudinal axis of the carrier. The burners are moved in a repeated cycle back and forth along the forming preform and between turnaround points where the direction of their motion is reversed. Measures are taken in the process to prevent or reduce overheating of the preform in the turnaround point regions. These measures can lead to variations in the rate of deposition.

Abstract: There is disclosed a method for producing a porous optical fiber base material comprising depositing fine glass powder on a rotating member, wherein pore size of the deposited fine glass powder is controlled, and preferably, mode of the pore size is controlled to be 0.1 to 1 &mgr;m, or wherein a total amount of absorbed H2O amount and OH group amount on the fine glass powder per square meter of fine glass powder surface area is controlled to be 3.5×10−5 to 7.5×10−5 g. Such porous optical fiber base materials have an improved weight of fine glass powder deposited on the member per batch, or an improved fine glass powder deposit efficiency, which may greatly contribute to improvement of production ability and reduction of production cost.