Abstract: A method of producing a porous glass-particle-deposited body by effectively depositing the glass particles synthesized by a burner for synthesizing glass particles on a starting member with increased bonding strength between the deposited glass particles and decreased possibility of developing cracks and other problems, and a burner to be used for the production method. In the method of producing the deposited body by depositing the glass particles synthesized by a burner on the surface of the starting member, the glass particle deposition surface has (a) a region that is hit by the center portion of the flame issuing from the burner and (b) another region that has a temperature higher than that of the region hit by the center portion of the flame and that is located at the outside of the region hit by the center portion of the flame.

Abstract: A concentric multi-tubular burner for synthesizing glass particles having a center port group constituted by a combination of jet ports of raw material gas, combustible gas and oxygen gas, wherein an outer wall of the oxygen gas jet port in the center port group protrudes more toward a burner head than an inner wall of the oxygen gas jet port. The flow rate of oxygen gas jetted from the oxygen gas jet port of the center port group is controlled to be in a proper range.

Abstract: The present invention provides a simple method for fabricating fiber-optic glass preforms having complex refractive index configurations and/or dopant distributions in a radial direction with a high degree of accuracy and precision. The method teaches bundling together a plurality of glass rods of specific physical, chemical, or optical properties and wherein the rod bundle is fused in a manner that maintains the cross-sectional composition and refractive-index profiles established by the position of the rods.

Abstract: A silica glass member manufacturing method of the present invention includes the steps of making a silicon compound react in oxyhydrogen flame using a burner having a multi-tubular structure to obtain fine silica glass particles, depositing the fine silica glass particles on a support rotating and placed to oppose the burner to obtain a silica glass ingot with a temperature distribution in at least one plane perpendicular to a rotational axis of the silica glass ingot, the temperature distribution being symmetrical with respect to the rotational axis and having a maximal value between a center and a peripheral portion of the plane, and obtaining a distribution of signed birefringence values on the basis of birefringence values and directions of phase advance axes measured at a plurality of points in the plane perpendicular to the rotational axis of the silica glass ingot and cutting, from the silica glass ingot, a silica glass member whose signed birefringence values monotonously increase from the center to t

Abstract: Germanium-silicon oxide, germanium-silicon oxynitride and silica-germania-titania materials and oxynitride materials suitable for fabricating optical waveguides for liquid crystal based cross-connect optical switching devices have a refractive index of from about 1.48 to about 1.52 at 1550 nm, and a coefficient of thermal expansion at room temperature of from about 3×10−6° C.−1 to about 4.4×10−6° C.−1. The compositions are adjusted so that the refractive index of the germanium-silicon oxide, germanium-silicon oxynitride or silica-germania-titania material is closely matched to the refractive index of a typical liquid crystal material whereby improved optical performance of a liquid crystal based cross-connect optical switching device is achieved.

Abstract: A method for increasing the photosensitivity of a selected portion of an optical fiber and for producing a grating in the selected portion of an optical fiber. The method includes the step of placing the selected portion of the optical fiber in a hydrogen containing atmosphere. The volume of the hydrogen-containing atmosphere immediately surrounding only the selected portion of the optical fiber is heated to a temperature of at least 250° C. Only the selected portion of the optical fiber is exposed to the heated volume of the hydrogen-containing atmosphere at a temperature of at least 250° C. for a predetermined time.

Abstract: A method of forming an optical fiber by heat treating a consolidated glass article, doped with at least one refractive index-modifying dopant, at a temperature between about 1100° C. and 1400° C. and for a time between about 1 hour and 12 hours in a helium-containing atmosphere. The consolidated glass article is an optical fiber precursor. The optical fiber drawn from the heat treated consolidated glass article exhibits an attenuation lower than an optical fiber drawn from a substantially identical optical fiber precursor that has not been heat treated in accordance with the present invention.

Abstract: Burners (14) are used to make glass bodies (19) from OMCTS. The burners have six concentric regions. Putting certain gases through the regions results in thicker bodies than can be achieved with existing techniques and with improved efficiency.

Abstract: A method for doping silica soot with fluorine during laydown, including providing a bait rod, and providing a burner, wherein the burner emits a reactant flame. The method also including providing at least one first gas-feed separate from the burner, wherein the gas-feed supplies a first jet of fluorine-based gases, and depositing a layer of silica soot on the bait rod by vaporizing a silica producing gas within the reactant flame of the burner. The method further including supplying the first jet of fluorine-based gases to the silica soot deposited on to the bait rod via the first gas-feed subsequent to vaporizing at least a portion of the silica producing gas within the reactant flame of the burner.

Abstract: A mandrel for producing quartz glass, comprising at least two columnar or cylindrical, carbon fiberreinforced carbon composite material made members joined in series by screw thread parts. The mandrel is carbon-impregnated and/or carbon-coated on the screw thread parts, and, in addition, may be provided with reinforcing members on the outer sides of the screw thread parts. Quartz glass fine particles obtained by flame-hydrolyzing a volatile silicon compound are deposited, using this mandrel, on the surface of a heat-resisting substratum or on a starting rod at the end of the mandrel to easily form a large porous quartz glass mother material, the porous quartz glass mother material is dehydrated and transparently vitrified to produce a large optical fiber mother material, and further the optical fiber mother material is drawn to produce a low-cost, high-precision optical fiber.

Abstract: An apparatus and method for fabricating an optical fiber, an optical fiber preform, and an optical fiber core rod are disclosed herein. In particular, the process of fabricating an optical fiber preform involves, during a modified chemical vapor deposition process, collapsing the substrate tube into an optical fiber preform, and compressing the optical fiber preform in the longitudinal direction. An optical fiber preform that is shorter, but larger in diameter is thus formed. The optical fiber preforms therefore can be stacked during the optical fiber fabrication process, which is useful in drawing longer optical fibers with comparable outer diameter and core diameter to that used as the industry standard.

Abstract: The present invention is directed to a system and method for delivering liquid reactants through a burner assembly to form soot used in the manufacture of glass, and in particular, optical waveguides. Due to the tendency of liquid reactants to react to form solids when exposed to water in the air, an evaporative liquid is first delivered through the burner assembly to the combustion zone. Once steady state liquid flow has been achieved in the system, the evaporative liquid is transitioned to the liquid reactant. The liquid reactant is delivered along the same path to the burner assembly, which discharges the liquid reactant into the combustion zone as an atomized liquid to form soot used in the manufacture of glass. Once the desired quantity of soot has been formed, the liquid reactant is transitioned back to the evaporative liquid while maintaining steady state flow. After the liquid reactant has cleared the system, flow of the evaporative liquid is terminated and the burner assembly flame turned off.

Abstract: Burners and methods for producing fused silica members. The burner includes seven gas-emitting regions, including four regions for emitting a mixture of oxygen and combustible gas.

Abstract: The present invention includes a method of growing a doped glass films suitable for optical applications on a substrate comprising the steps of conveying an organometallic compound of the formula (R3SiO)jM(OR′)k to the substrate and reacting the silica forming substance and the organometallic compound to form the optical layer on the substrate, where M is a metal; R is methyl, ethyl or propyl; R′ is methyl, ethyl, n-propyl, n-butyl, isobutyl or s-butyl; j is 1, 2, 3 or 4; and k=4−j. The present invention also includes planar optical devices made by the above method. Additionally, the present invention includes an optical fiber made by the above method.

Abstract: A method for performing high aspect ratio gap fill during planar lightwave circuit top clad deposition. A plurality of waveguide cores are formed on a substrate, the waveguide cores having a plurality of gaps there between. A cladding layer is formed over the waveguide cores and the substrate using a high-density plasma deposition process. The refractive index of the waveguide cores are controlled by using a dopant to be higher than the refractive of the cladding layer. An anneal process is performed on the cladding layer after the high-density plasma deposition process. The gaps between the waveguide cores can be smaller than 2 microns. The aspect ratio of the gaps between the waveguide cores can be greater than 3. The high-density plasma deposition process provides a very high purity USG (undoped silica glass) and BPSG (Boron Phosphorous silica glass) layers having a uniform refractive index.

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: 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: 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: In a method of coating a CMC fiber, the fiber is passed through a reaction zone along a path substantially parallel to a longitudinal axis of the zone, a flow of fiber coating reactant is passed though the reaction zone, at least a portion of the flow of reactant is disrupted from a path substantially parallel to the fiber path to create a mixing flow adjacent the fiber. A coating reactor includes a reactor chamber to accommodate a fiber passing along a path substantially parallel to a longitudinal axis of the chamber and a flow of fiber coating reactant. The reactor chamber further includes a flow disrupter located within the reactor chamber to disrupt at least a portion of the flow of reactant from a path substantially parallel to the fiber path to create a mixing flow adjacent the fiber.

Abstract: A core glass for making a preform for an optical fiber particularly useful for the transmission of ultraviolet radiation and methods for making the core glass are disclosed. The core glass is obtained by the flame hydrolysis of a silicon compound, deposition of finely granular SiO2 on a substrate with direct vitrification and formation of a synthetic quartz glass. The quartz glass has a hydrogen content of less than 1×1018 molecules/cm3.

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 of depositing a core layer for an optical waveguide structure of a planar lightwave circuit. A GePSG core for an optical waveguide structure of a planar lightwave circuit is fabricated such that the optical core comprises doped silica glass, wherein the dopant includes Ge and P. In depositing a core layer from which the optical core is formed, two separate doping gasses (e.g., GeH4 and PH3) are added during the PECVD process to make Ge and P doped silica glass (GePSG). The ratio of the Ge dopant and the P dopant is configured to maintain a constant refractive index within the core layer across an anneal temperature range and to reduce a formation of bubbles within the core layer. The ratio of the Ge dopant and the P dopant is also configured to reduce refractive index birefringence within the core layer across an anneal temperature range.

Abstract: Methods of fabricating solid state optical waveguide structures comprising a doped silicon dioxide core layer sandwiched between lower and upper doped silicon dioxide cladding layers on a silicon substrate. The core and upper cladding layers are deposited using a plasma enhanced CVD process. The core layer is patterned to define one or more waveguide cores. The lower cladding layer is preferably also deposited using a plasma enhanced CVD process but alternatively may be formed by thermal oxidation.

Abstract: An optical waveguide substrate is prepared by forming grooves in a silicon substrate in accordance with the pattern of a desired waveguide device, thermally oxidizing the silicon substrate to form a peripheral quartz layer surrounding the grooves, burying in the grooves a doped quartz glass layer having a higher refractive index, abrading the surface of the resulting structure to be flat, and forming on the flat surface a glass layer having a lower refractive index. An optical waveguide substrate featuring no distortion of the core pattern, little warp, and a low loss can be produced in a simple manner.

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: Burners (40) for producing fused silica boules are provided. The burners employ a tube-in-tube (301-306) design with flats (56, 50) on some of the tubes (305, 301) being used to limit the cross-sectional area of certain passages (206, 202) within the burner and/or to atomize a silicon-containing, liquid source material, such as OMCTS. To avoid the possibility of flashback, the burner has separate passages for fuel (205) and oxygen (204, 206), i.e., the burner employs nozzle mixing, rather than premixing, of the fuel and oxygen. The burners are installed in burner holes (26) formed in the crown (20) of a furnace and form a seal with those holes so that ambient air cannot be entrained into the furnace through the holes. An external air cooled jacket (60) can be used to hold the temperature of the burner below a prescribed upper limit, e.g., 400° C.

Abstract: An optical waveguide is formed on a substrate by first depositing an undercladding layer over the substrate. At least one core is formed over the undercladding layer. An uppercladding layer is then formed over the cores with a high-density plasma process. Deposition of the uppercladding layer may proceed by flowing an oxygen-containing gas, such as O2, a silicon-containing gas, such as SiH4, and a fluorine-containing gas, such as SiF4, into a process chamber to produce a gaseous mixture. A high-density plasma, i.e. having a density of at least 1011 ions/cm3, is generated from the gaseous mixture and then used to deposit a fluorinated silicate glass layer.

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 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 preform overcladding device is provided. The preform overcladding device includes an injector for providing particles having a predetermined material, and a preheater for preheating the particles provided by the injector. The preform overcladding device also includes a heater for heating and depositing onto a preform the particles preheated by the preheater.

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: In an optical fiber of this invention, the MFD is increased to effectively suppress the influence of nonlinear optical effects. A method of manufacturing the optical fiber effectively prevents bubble occurrence in a transparent preform, deformation of the preform, and flaws on the preform surface during the manufacture. The optical fiber has, from its center to the peripheral portion, a first core having a first refractive index n1, a second core having a second refractive index n2 (<n1), a first cladding having a third refractive index n3 (<n2), and a second cladding having a fourth refractive index n4 (>n3, <n2). The outer diameter of the second core is set to be 25 to 40 &mgr;m. Specifically, the refractive indices of the first and second claddings of the optical fiber preferably increase in the radial direction from the inner side thereof to the peripheral side thereof.

Abstract: Methods for producing high purity fused silica (HPFS) glass having desired levels of dissolved hydrogen are provided. The methods involve measuring the level of hydrogen in the cavity of the furnace used to produce the glass and controlling the pressure within the furnace and/or gas flows to the furnace's burners so that the measured concentration has a desired value. In this way, the level of dissolved hydrogen in the glass can be controlled since, as shown in FIG. 3, there is a direct correlation between the hydrogen concentration in the cavity atmosphere and level of dissolved hydrogen in the glass.

Abstract: A method of depositing a dual layer top clad for an optical waveguide of a planar lightwave circuit (PLC). The method includes a first step of providing a high flow rate of a Boron dopant gas for a first top cladding layer deposition process. Then, a low flow rate of a Boron dopant gas is provided for a second top cladding layer deposition process. The second top cladding layer deposition process is performed directly on the first top cladding layer deposition. The first and second top cladding layer deposition processes are combined to form a dual layer top clad of the PLC having a high Boron portion covering a plurality of optical cores and a low Boron portion covering the first portion. The first top cladding layer deposition process can comprises three deposition and anneal cycles using the high flow rate for the Boron dopant gas. The three deposition and anneal cycles are used to fill gaps between the plurality of optical cores of the PLC.

Abstract: A method of making an optical waveguide structure having improved thermal isolation and stress reduction. The method etches both deep trenches and shallow trenches in a single step. The method includes the step of depositing a partial top clad layer over a first and second waveguide core. An etch back is then performed on the partial top clad layer to obtain a desired thickness of the partial top clad layer. A first hard mask layer is subsequently deposited over the partial top clad layer. A set of hard masks are then formed over the first and second waveguide cores by patterning and etching the first hard mask layer. A full top clad layer is then deposited over the partial top clad layer and the set hard masks to form a top clad. A second hard mask layer is then deposited over the top clad. A deep trench area and first and second shallow trench areas are then exposed by patterning and etching the second hard mask layer.

Abstract: The present invention relates to a method of manufacturing an optical fiber by carrying out one or more chemical vapor deposition reactions in a substrate tube, with the optical fiber exhibiting a low sensitivity to the hydrogen induced attenuation losses at a transmission wavelength of 1550 nm. The present invention furthermore relates to an optical fiber comprising a cladding layer and a light conducting core, which fiber has been obtained by using the present method.

Abstract: The present invention relates to a method and apparatus for fabricating a glass preform used in the manufacture of optical waveguides. The method utilizes a gas phase hydrolysis of a silica precursor without using a carrier gas. The flow of the reactants in the reaction chamber is confined and deposited on the target preform by careful control of the thermal profile in the system.

Abstract: A method of depositing a top clad layer for an optical waveguide of a planar lightwave circuit. A GeBPSG top clad layer for an optical waveguide structure of a planar lightwave circuit is fabricated such that the top clad layer comprises doped silica glass, wherein the dopant includes Ge (Germanium), P (Phosphorus), and B (Boron). In depositing a top clad layer for the optical waveguide, three separate doping gasses (e.g., GeH4, PH3, and B2H6) are added during the PECVD (plasma enhanced chemical vapor deposition) process to make Ge, P and B doped silica glass (GeBPSG). The ratio of the Ge, P, and B dopants is configured to reduce the formation of crystallization areas within the top clad layer and maintain a constant refractive index within the top clad layer across an anneal temperature range. A thermal anneal process for the top clad layer can be a temperature within a range of 950C to 1050C.

Abstract: The crosstalk characteristics of an arrayed waveguide grating or the like are improved. One or more of substrates are placed at a circumferential position centering the table rotational center C on a turntable that rotates at a constant angular speed of rotation &ohgr; and the turntable is rotated. A burner is moved to and fro in the radial direction of the turntable between positions r1 and r2 in the radial direction of the turntable and is reciprocated across the substrates. A material gas of glass, an oxygen gas and a hydrogen gas are passed through the burner to generate a hydrolysis reaction of the material gas in a hydrogen oxygen flame and an under cladding glass particle, a core glass particle and an over cladding particle are sequentially deposited on the substrates to form an optical waveguide part.

Abstract: The present invention relates to a synthetic quartz glass, which is a material for producing an optical member having an excellent excimer laser resistance, and a production method thereof with a good productivity. That is, the synthetic quartz glass produced by vitrifying glass fine particles obtained by flame hydrolysis of an organodisilazane compound directly on a substrate having a birefringence index of 5 nm/cm or less, a refractive index difference (&Dgr;n) of 2×10−6/cm or less, and an ArF saturated absorbance of 0.05/cm or less at a pulse energy density of 100 mJ/cm2/pulse.

Abstract: Embodiments of the invention include a method for making optical fibers that have reduced aging loss, hydrogen aging and other losses over the life of the fiber, and optical systems including such optical fibers. Improved conditions in fiber manufacturing environments are provided to reduce the likelihood of generating defects in optical fiber preforms that, in optical fiber drawn therefrom, attract and bond with hydrogen atoms to form molecules that increase transmission loss in the fiber. The improved conditions include the establishment and adjustment of the oxygen stoichiometry in one or more of the environments in which optical fiber manufacturing process steps occur. Optical fiber made by methods according to embodiments of the invention have improved transmission characteristics, e.g., transmission loss at 1385 nanometers that is less than 0.33 dB/km and the change in transmission loss thereafter is less than 0.05 dB/km.

Abstract: An apparatus for manufacturing a glass base material, which is a base material of an optical fiber, the glass base material having a core rod as a central axis, comprises a holding unit having a plurality of scroll chucks connected in series along the core rod for holding an end of the core rod; and a burner that hydrolyzes a gas material, which is abase material of the glass base material, into glass particles and accumulates the glass particles around the core rod to form the glass base material.

Abstract: A method of making a phosphosilicate fiber comprises the steps of: (i) manufacturing a preform containing phosphorus doped silica; and (ii) drawing phosphosilicate fiber from said preform at a temperature in the range of 1700° C. to 1900° C.

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 core glass for making a preform for an optical fiber particularly useful for the transmission of ultraviolet radiation and methods for making the core glass are disclosed. The core glass is obtained by the flame hydrolysis of a silicon compound, deposition of finely granular SiO2 on a substrate with direct vitrification and formation of a synthetic quartz glass. The quartz glass has a hydrogen content of less than 1×1018 molecules/cm3.

Abstract: Disclosed is a method of making a hydrogen resistant optical waveguide fiber. The soot preform is heated and immersed in a metal halide gas. A reduced metal species is thus incorporated into the glass soot prior to sintering or consolidation of the soot preform. A hydrogen absorption band around 1530 nm is substantially eliminated from waveguides made from a precursor gas treated preform.

Abstract: The invention relates to a method and apparatus for a glass manufacturing facility. The apparatus includes a glass production system providing an exhaust stream entrained with particulate material including germanium—containing particulate. The apparatus further includes an exhaust filtration system including a PTFE fabric material. The exhaust filtration system is connected to the production system to receive the exhaust stream an capture the particulate material. A collection system is connected to the exhaust system to collect the captured particulate material from the exhaust system. The particulate material collected contains at least about 2% by weight germanium. The invention further includes incorporating the aforementioned apparatus into the operation of a glass manufacturing facility.

Abstract: Fused silica boules (19) having improved radial homogeneity are produced by controlling the air flow around the boule (19) during its formation. The boule is formed in a cup-like containment vessel (13) which collects silica particles from a plurality of burners (14). The containment vessel (13) rotates and oscillates relative to the burners (14) as the boule (19) is formed. The containment vessel (13) is bounded by a cup-like containment wall (22), and a shadow or air flow wall (130) is spaced apart from and surrounds the containment wall (22) forming a gap or air flow passage (175) therebetween. A radially-outwardly extending deflecting wedge portion (23) is formed at the upper extent of the containment wall (22) and at an outlet end of flow passage (175).

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.