Abstract: A method of manufacturing at least one optical fibre preform comprising: providing a plurality of partially porous intermediate preforms, each partially porous intermediate preform having a longitudinal axis and comprising a respective soot intermediate clad layer formed around a respective glass core rod comprising a central core region of radius a and an inner clad region of radius b to define a first core-to-clad ratio a/b; consolidating the formed soot intermediate clad layers to form a respective plurality of intermediate glass preforms, each of the plurality of intermediate glass preforms comprising an intermediate clad region having an external radius c to define a second core-to-clad ratio a/c of from 0.20 to 0.

Abstract: Methods are described for manufacturing silica-based glass, in which silica precursor material is supplied to a synthesis flame in the form of an emulsion. The methods involve the steps of: forming an emulsion of an aqueous phase in a non-aqueous liquid silica precursor material; supplying the emulsion as a spray of droplets into a synthesis flame, whereby the precursor material is converted in the flame into a silica-containing soot; and collecting the soot on a substrate, either as a porous soot body for subsequent consolidation to glass or directly as a substantially pore-free glass.

Abstract: A glass particle deposit producing method capable of preventing the variation in the outside diameter of a glass particle deposit and enhancing the yield of a glass raw material is provided. A glass particle deposit is produced by mounting a starting rod 11 and a glass particle generating burner 22 inside a reaction vessel 2, introducing a glass raw material into the burner 22, subjecting the glass raw material to a flame decomposition reaction inside a flame formed by the burner 22 to generate glass particles, and depositing the generated glass particles on the starting rod 11. At this time, the dispersion angle of the glass raw material jetted from the burner 22 with respect to the center axis of the burner 22 is set to the range of 5 to 70 degrees.

Abstract: Methods of forming an overclad portion of an optical fiber are described which include positioning a core cane member in an overclad tube to form a rod and tube assembly. Thereafter, glass soot pellets are positioned in the rod and tube assembly between the core cane member and an interior sidewall of the overclad tube. The rod and tube assembly is then redrawn under conditions effective to form the overclad tube and the glass soot pellets into a continuous, void-free glass layer surrounding the core cane member at a sintering time tsinter of at least 1800 seconds thereby forming an overclad portion of an optical fiber.

Abstract: A known method for producing synthetic quartz glass comprises: (a) reacting a carbonic silicon compound-containing raw material with oxygen in a reaction zone into SiO2 particles, (b) precipitating the SiO2 particles on a sedimentation area by forming a porous SiO2 soot body containing hydrogen and hydroxyl groups, (c) drying the porous SiO2 soot body, and (d) glazing to the synthetic quartz glass by heating the soot body up to a glazing temperature. In order to facilitate cost-efficient production of quartz glass by means of pyrolysing or hydrolysing a carbon-containing silicon compound using a carbon-containing raw material, the invention describes the production of a soot body with a carbon content within the range of 1 ppm by weight to 50 ppm by weight.

Abstract: A titania-doped quartz glass suited as an EUV lithographic member is prepared by feeding a silicon-providing reactant gas and a titanium-providing reactant gas through a burner along with hydrogen and oxygen, subjecting the reactant gases to oxidation or flame hydrolysis to form synthetic silica-titania fine particles, depositing the particles on a rotating target, and concurrently melting and vitrifying the deposited particles to grow an ingot of titania-doped quartz glass. The target is retracted such that the growth front of the ingot may be spaced a distance of at least 250 mm from the burner tip.

Abstract: A porous layer is formed by depositing a silica glass particle around a core rod. The porous layer is dehydrated. The dehydrated porous layer is sintered under a decreased pressure until the dehydrated porous layer becomes a translucent glass layer containing a closed pore. The translucent glass layer is vitrified under an ambient atmosphere including an inert gas other than a helium gas.

Abstract: A method of manufacturing an optical fiber preform by depositing glass fine particles onto a surface of a glass rod while the glass rod is reciprocated relative to a plasma torch, including: moving the glass rod in a first direction relative to the plasma torch while the plasma torch is applied to the glass rod and supplied at least with a dopant material and a glass material to deposit the glass fine particles onto the surface of the glass rod, in such a manner that a plasma power is set higher during a first time interval starting from a beginning of the movement of the glass rod in the first direction than during a second time interval starting from an end of the first time interval; and moving the glass rod in a second direction relative to the plasma torch, where the second direction is opposite to the first direction.

Abstract: A synthetic quartz glass ingot is prepared by vapor phase hydrolyzing or oxidatively decomposing a silica feedstock in a flame to form fine particles of silica, depositing the silica particles on a target and melting and vitrifying the particles to form a synthetic quartz glass ingot on the target while the target is moved back and forth. The method further comprises: (i) continuously feeding the silica feedstock at a predetermined rate, (ii) keeping the flame in constant contact with an overall growing face, (iii) cyclically repeating the back and forth movement of the target at a predetermined speed, and (iv) maintaining the shape of the growing ingot unchanged.

Abstract: The invention relates to a known method for the production of a cylinder from quartz glass, comprising a step, wherein an SiO2 body which comprises a porous SiO2 soot layer and has a lower end, an upper end, and an outer casing, is sintered to form said quartz glass cylinder in a vitrification furnace, and is being held in a vertical orientation by means of a retaining device, which comprises an upper retaining element connected at the upper end of the SiO2 body, and a lower retaining element disposed on the lower end. In order to provide a method based thereon, by means of which even heavy bodies made of porous SiO2 can be safely retained during vitrification, the invention provides that the retaining device has a dimensionally stable connecting part, which extends inside the vitrification furnace along the outer casing of the SiO2 body and which connects the upper and the lower retaining elements to each other.

Abstract: A method of manufacturing an optical fiber base material having very little impurity which deteriorates the transmission characteristic of an optical fiber is provided. The method of manufacturing an optical fiber base material including: producing a core member for the optical fiber base material by dehydrating and transparently vitrifying a base material formed by depositing glass particles; and drawing the core member and then adding a cladding thereto at a desired core to cladding ratio, wherein the dehydrating includes suspending the base material in a furnace tube having a heating region in a first atmosphere at a first temperature, the base material passing through the heating region as upwardly moving, and the transparently vitrifying includes situating the base material below once and then allowing the base material to pass through the heating region in a second atmosphere at a second temperature as upwardly moving again.

Abstract: A titania and sulfur co-doped quartz glass member is provided. Due to co-doping of titania and sulfur, the quartz glass member undergoes zero expansion at a certain temperature and low thermal expansion over a wide temperature range, and is thus suited for use in a commercial EUV lithography tool. A manufacturing method and an optical member for EUV lithography are also provided.

Abstract: The present invention provides a method for producing a glass preform capable of improving the deposition efficiency of produced glass fine particles to a starting rod or a glass soot body. The method for manufacturing a glass preform includes controlling the temperature of SiCl4 used as a source gas to 100° C. or more, producing glass fine particles having an average outer diameter of 90 nm or more in a flame of a burner for producing glass fine particles, and depositing the glass fine particles on a starting glass rod 13.

Abstract: A known method for producing a hollow cylinder of synthetic quartz glass comprises the steps of: (a) providing an inner tube of synthetic quartz glass having an inner bore defined by an inner wall, (b) cladding the inner tube (3?) with an SiO2 soot layer (4?), and (c) sintering the SiO2 soot layer with formation of the hollow cylinder. Starting therefrom, to indicate a method in which on the one hand the sintering process is completed before the hollow cylinder is further processed together with the core rod, and in which on the other hand a complicated machining of the inner bore of the hollow cylinder of quartz glass is not required, the invention suggests that during sintering the surface temperature of the inner wall of the inner tube should be kept below the softening temperature.

Abstract: A method of making a fused silica article that is loaded with hydrogen. A fused silica glass near net shape part is provided and is loaded with a molecular hydrogen in a range from about 0.1×1017 molecules/cm3 up to about 1×1019 molecules/cm3. The thinner shape of the near net shape part enables the shape to be loaded more quickly than previous methods. A fused silica article loaded with hydrogen using the method is also described.

Abstract: A multi-nozzle type burner is used for producing a porous glass preform, the burner having small variations in deposition efficiency with the burner tip being not burned even when axial shift occurs at the concentric multi-tube part of the burner. The present invention provides a burner for producing a porous glass preform with a concentric multi-tube structure, comprising a glass material gas jet port in a center, a plurality of gas jet ports concentrically disposed outside the glass material gas jet port, and small-diameter gas jet ports which are disposed in a line or a plurality of lines concentrically to the glass material gas jet port so as to be enclosed in one of the gas jet ports other than the gas jet ports in the center and at an outermost side, the small-diameter gas jet ports in the same line having an identical focal length.

Abstract: The present invention provides a burner for manufacturing a porous glass preform, which is provided with a combustible gas injection port involving a plurality of small-diameter supporting gas injection ports such that the injection ports of the same row have the equal focal distance, the small-diameter supporting gas injection ports being arranged on the outside of a glass source gas injection port in the center so as to be in a row or in a plurality of rows and concentric with the glass source gas injection port, wherein the small-diameter supporting gas injection ports are bent toward the burner center axis at predetermined positions from the tip ends of the small-diameter supporting gas injection ports so that the focal points of the small-diameter supporting gas injection ports of the same row agree with each other, and the bend angle of the small-diameter supporting gas injection port row closest to the glass source gas injection port in the center of the small-diameter supporting gas injection port row

Abstract: An object of the invention is to provide a process for producing a synthetic quartz glass while taking account of a refractive index distribution remaining in the synthetic quartz glass; a jig for use in the synthetic-quartz-glass production process; and a synthetic quartz glass for an optical member, produced by the process.

Abstract: A method of making an optical fiber preform includes depositing silica glass soot on the inside of a substrate tube via a chemical vapor deposition operation. The silica glass soot is consolidated into silica glass under controlled conditions such that the consolidated silica glass on the interior of the substrate tube contains a non-periodic array of gaseous voids in a cladding region of the optical fiber preform. The optical fiber preform may be used to produce an optical fiber having a core and a cladding containing voids formed from the gaseous voids of the cladding region of the optical fiber preform. The core of the optical fiber has a first index of refraction and the cladding has a second index of refraction less than that of the core.

Abstract: A dehydration-sintering furnace includes a core tube configured to dehydrate and sinter a porous base material in fabrication of an optical fiber and having an outlet configured to discharge a vapor. The furnace includes a pressure-variation damper connected to the outlet of the core tube. The furnace includes a trap between the core tube and the pressure-variation damper for collecting the vapor.

Abstract: A dehydration-sintering furnace includes a core tube configured to dehydrate and sinter a porous base material in fabrication of an optical fiber and having an outlet configured to discharge a vapor. The furnace includes a pressure-variation damper connected to the outlet of the core tube. The furnace includes a trap between the core tube and the pressure-variation damper for collecting the vapor.

Abstract: Fused silica injected or 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. Particles are heated, surface softened and agglomerated in mass and are collected in a heated crucible and are softened and flowed through a heated lower throat. The material is processed into quartz plates and rods for wafer processing and optical windows.

Abstract: A method of making an optical fiber preform includes depositing silica glass soot on the inside of a substrate tube via a chemical vapor deposition operation. The silica glass soot is consolidated into silica glass under controlled conditions such that the consolidated silica glass on the interior of the substrate tube contains a non-periodic array of gaseous voids in a cladding region of the optical fiber preform. The optical fiber preform may be used to produce an optical fiber having a core and a cladding containing voids formed from the gaseous voids of the cladding region of the optical fiber preform. The core of the optical fiber has a first index of refraction and the cladding has a second index of refraction less than that of the core.

Abstract: A guide hole guides a primary-coated optical fiber to a tubular inlet hole. An inner diameter of the guide hole is larger than that of the tubular inlet hole. An inner diameter of the tubular inlet hole is in a range from 1.5 times to 2.0 times that of the primary-coated optical fiber. A length of the tubular inlet hole is in a range from 1.0 mm to 2.0 mm. A depth of the guide hole is in a range from 2.0 mm 9.0 mm. A relation B?A is satisfied, with B equal to or larger than 7.0 mm, where A is an inner diameter of a leading edge of the guide hole continued to a trailing edge of the tubular inlet hole, and B is an inner diameter of a trailing edge of the guide hole.

Abstract: In a synthetic quartz glass ingot which is produced by vapor phase hydrolyzing or oxidatively decomposing a silica-forming starting compound in an oxyhydrogen flame such that silica growth in a direction occurs at a silica particle deposition and melting face, striae visible when viewed from a direction perpendicular to the silica growth direction are distributed periodically over the silica growth direction. The ingot can be used in the production of optical-grade high-homogeneity synthetic quartz glass elements for excimer laser applications, particularly ArF excimer laser applications, in the production of laser damage-resistant optical elements used with light sources such as excimer lasers, and in the production of UV optical fiber.

Abstract: A method of manufacturing a glassy optical preform is disclosed that includes providing a preform having a silica soot layer and then sintering the soot layer into a glassy layer, and water is selectively added to the preform by exposing the soot layer to a gaseous water-containing atmosphere during the sintering step. The preform is controllably doped with water.

Abstract: The present invention relates to a method of manufacturing an optical fibre suitable for high transmission rates, which method comprises: i) supplying one or more glass forming precursors, and possibly a dopant, to a quartz substrate tube, ii) forming a plasma in the quartz substrate tube for the purpose of bringing about a reaction mixture so as to form glass layers, which may or may not be doped, on the interior of the substrate tube, iii) collapsing the substrate tube obtained in step ii) into a perform while heating, and iv) drawing an optical fibre from the perform while heating. The present invention furthermore relates to an optical fibre suitable for high transmission rates.

Abstract: A method of fabricating an optical fiber preform using a modified chemical vapor deposition method and a nonlinear optical fiber fabricated using the method. The method comprises the steps of: forming a cladding layer and a core layer in a quartz glass tube; partially sintering the core layer; partially shrinking both ends of the quartz glass tube, in which the cladding layer and the core layer partially sintered are formed; and doping a sintered portion of the core layer with an impurity component, so that the optical fiber preform fabricated has a predetermined function. The nonlinear optical fiber being fabricated by a process comprising the steps of: forming the cladding layer and the core layer in a quartz glass tube; partially sintering the core layer; partially collapsing both ends of the quartz glass tube; and doping a sintered portion of the core layer with a predetermined impurity component.

Abstract: A method of making an optical waveguide preform includes forming a preform including a first portion and a second radial portion, wherein the second portion includes a dopant, and wherein the first portion exhibits a density greater than the second portion. The method further includes stripping at least a portion of the dopant from the second portion. In a preferred embodiment, the stripped dopant has migrated in a previous processing step.

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: 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: A double-clad optical fiber includes a core, a multimode inner cladding disposed about the core, and a second cladding layer disposed about the inner cladding. The core includes an active material for absorbing pump radiation received by the inner cladding. The multimode inner cladding includes truncated regions including a first material, where the first material has an index of refraction that is different than the material of the inner cladding that surrounds said truncated regions, for promoting the scattering of pump radiation propagating in the multimode inner cladding for increasing the absorption of the pump radiation by the active material of the core. The truncated regions can include voids that are empty or that comprise a gas. Particles can be distributed in a soot and/or voids formed in the soot, where the soot can be deposited via Outside Vapor Deposition for forming the truncated regions in an optical fiber drawn from a preform.

Abstract: A process for producing synthetic quartz glass using a burner composed of a plurality of concentric nozzles involves the steps of feeding a silica-forming raw material gas and a fluorine compound gas to a reaction zone from a center nozzle, feeding oxygen gas from a second nozzle outside the center nozzle, and feeding oxygen gas and/or hydrogen gas from a third nozzle. The silica-forming raw material gas is hydrolyzed to form fine particles of silica, which particles are deposited on a rotatable substrate so as to form a porous silica matrix, which is then fused to give the quartz glass. The flow rate of the oxygen gas fed from the second nozzle and the flow rate of the raw material gas are controlled so as to provide a 1.1- to 3.5-fold stoichiometric excess of oxygen. The excess oxygen suppresses Si—Si bond formation in the quartz glass, enabling the production of synthetic quartz glass having a high transmittance in the vacuum ultraviolet region.

Abstract: Applicants have discovered the existence of loss peaks in optical fiber transmission systems using wavelengths in the E-band and the L-band. Specifically, they have discovered the existence of narrow loss peaks at 1440 nm, 1583 nm and 1614 nm. Because the peaks are relatively narrow, they cannot be easily removed by conventional gain equalizers in long haul transmission systems, and although the peaks are relatively small, they can nonetheless cause transmission channels to drop out in amplified DWDM transmission systems. Applicants have further discovered that these loss peaks are due to carbon contamination of the transmission fiber. Thus optical fibers should be fabricated essentially free of carbon contamination. This means eliminating carbon-containing reagents in preform and tube-making processes.

Abstract: The optical fiber which enables the optical fiber transmission stabilized in the wavelength range of the pump light also, which is not used conventionally, and suppresses the non-linear effect on the occasion of WDM transmission is offered. The optical fiber for WDM transmission has at least three or more layers wherein the first core doped with germanium is located at the center and surrounded by the second core having a refractive index lower than the first core, and cladding having a refractive index lower than the first core and higher than second core surrounds the second or last core layer.

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: In a synthetic quartz glass ingot which is produced by vapor phase hydrolyzing or oxidatively decomposing a silica-forming starting compound in an oxyhydrogen flame such that silica growth in a direction occurs at a silica particle deposition and melting face, striae visible when viewed from a direction perpendicular to the silica growth direction are distributed periodically over the silica growth direction. The ingot can be used in the production of optical-grade high-homogeneity synthetic quartz glass elements for excimer laser applications, particularly ArF excimer laser applications, in the production of laser damage-resistant optical elements used with light sources such as excimer lasers, and in the production of UV optical fiber.

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 optical fiber preform (1) serving as a material of an optical fiber has a shoulder portion (12) thrusting beyond a middle portion (M) in a base end region (K) which is on the upper side when the optical fiber preform is suspended for a drawing process. The optical fiber preform (1) of this configuration can be easily produced by appropriately setting the heating condition, etc. for the sintering step in the production process. Thus, it is possible to omit the elongating step after the sintering step, thereby simplifying the production process. Further, in the prior-art technique, turbulence is generated in the gas flow in the furnace of the drawing apparatus toward the end of the drawing step, making it impossible to draw in a stable manner.

Abstract: A method and apparatus are disclosed for the manufacture of an optical fiber preform having incorporated therein a comparatively high concentration of rare earth dopant material, and which thus can be drawn and processed into an optical fiber having low numerical aperture, low core attenuation, and high pumping power absorption. The high concentrations of rare earth dopant material are accomplished through either the “hybrid vapor processing” (HVP) method or a “hybrid liquid processing” (HLP) method, each capable of being practiced in combination or independently of one another. The HVP method involves the vaporization of a rare earth halogen by the exposure thereof to a sufficiently elevated temperature, independently, or contemporaneously with the transport of the resultant rare earth halogen laden vapor, into a glass forming oxidation reaction zone on a flowing stream of essentially an unreactive inert gas, such as helium.

Abstract: The present invention relates to a single-mode optical fiber having a configuration which enables lowering of dispersion slope while securing a sufficient MFD. This single-mode optical fiber has a refractive index profile in which an indent with a sufficient width is provided at the center of its core region.

Abstract: The present invention discloses novel methods for fabricating glass articles, particularly optical fiber glass preforms, which may contain alumina, yttrium, lanthanum, erbium, or other rare earth metals as dopants. The glass articles made in accordance with the present invention exhibit radially uniform dopant profiles relative to conventional dopant methods. In addition, the overall concentration of the dopant is increased relative to analogous dopant methods.

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: Disclosed is a method of fabricating an optical fiber preform using a modified chemical vapor deposition method and a nonlinear optical fiber fabricated using the method, in which an impurity component is doped after both ends of a quartz glass tube are partially collapsed, so that an impurity doping process can be stably executed and the doped quantity of the impurity component can be increased. The method comprises the steps of: forming a cladding layer and a core layer in a quartz glass tube; partially sintering the core layer; partially shrinking both ends of the quartz glass tube, in which the cladding layer and the core layer partially sintered are formed; and doping a sintered portion of the core layer with an impurity component, so that the optical fiber preform fabricated has a predetermined function.

Abstract: There are disclosed a method for producing an optical fiber base material ingot comprising depositing a soot on a starting core member, and subjecting the soot to dehydration, vitrification by sintering, and then cylindrical grinding, wherein the cylindrical grinding is performed while a core portion central axis is brought into line with a rotation axis of cylindrical grinding machine, and an optical fiber base material ingot produced by the method. According to the present invention, there are provided an optical fiber base material ingot having excellent ingot roundness and excellent core portion eccentricity, and a production method capable of producing the optical fiber base material ingot in a short period of time.

Abstract: Fused silica injected or 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. Particles are heated, surface softened and agglomerated in mass and are collected in a heated crucible and are softened and flowed through a heated lower throat. The material is processed into quartz plates and rods for wafer processing and optical windows.

Abstract: There are disclosed a method for producing an optical fiber base material ingot comprising depositing a soot on a starting core member, and subjecting the soot to dehydration, vitrification by sintering, and then cylindrical grinding, wherein the cylindrical grinding is performed while a core portion central axis is brought into line with a rotation axis of cylindrical grinding machine, and an optical fiber base material ingot produced by the method. According to the present invention, there are provided an optical fiber base material ingot having excellent ingot roundness and excellent core portion eccentricity, and a production method capable of producing the optical fiber base material ingot in a short period of time.

Abstract: An optical fiber comprising a core region 100 doped with Cl which raises the refractive index; and a cladding region 200, provided at the outer periphery of the core region 100, having a cladding layer 201 doped with F which lowers the refractive index is formed. The cladding region 201 to become the outermost cladding layer is configured such that the doping amount of F successively decreases within an outer peripheral part 205 including the outer periphery thereof to a predetermined doping amount which is the minimum doping amount of F within the cladding layer 201. Therefore, the stress within the optical fiber is dispersed into the outer peripheral part 205 having an enhanced viscosity, whereby the stress concentration into the core is suppressed. Since the favorable tension range at the time of drawing the optical fiber becomes wider at this time, tension control is facilitated.

Abstract: This invention relates to the production of high purity fused silica glass through oxidation or flame hydrolysis of a vaporizable silicon-containing compound. More particularly, this invention is directed to the use of vaporizable, halide-free compounds in said production. In the preferred practice, a polymethylsiloxane comprises said vaporizable, halide-free compound.