Abstract: A transparent glass preform for an optical fiber is produced by heating a glass soot preform to remove gas from the soot preform at a temperature at which the soot preform is not vitrified under reduced pressure, and then heating the preform at a temperature at which the preform is vitrified under reduced pressure, whereby the transparent glass preform containing no or little bubbles and having a uniform outer diameter is produced.

Abstract: The invention relates to lenses, prisms or other optical members which are subjected to high-power ultraviolet light having a wavelength of about 360 nm or less, or ionizing radiation, particularly optical members for use in laser exposure apparatus for lithography, and to blanks for such optical members. The homogeneity of the refractive index distribution and the resistance to optical deterioration when the optical members are exposed for a long period of time to short wavelength ultraviolet light from a laser beam are improved. The optical members are made of high-purity synthetic silica glass material containing at least about 50 wt. ppm of OH groups, and are doped with hydrogen.

Abstract: A surface of an optical fiber is coated by a method for coating a surface of an optical fiber with carbon comprising steps of introducing an optical fiber in a reaction chamber in the same direction as the flow of a coating raw material comprising carbon, hydrogen and halogen atoms and depositing on the surface of the optical fiber a carbon layer formed from the raw material by chemical vapor deposition, whereby the coated optical fiber has improved initial tensile strength and absorbs less hydrogen.

Abstract: According to the invention, a hollow silica bar (2) is produced with a thick wall and high geometrical precision, the bar is then cleaned and an oven (24) is used able to heat the silica to its melting temperature and with respect to which the bar is moved so as to embody an external thermic glazing of the bar, an internal vapor phase depositing a vitreous coating in this bar by making circulate inside it a mixture of suitable gaseous constituents, this coating being intended for the subsequent formation of the core of the optical fibers, and an area contraction of the bar, the various temperatures of the bar required to embody these operations being obtained by varying the temperature of the oven or speed of the bar with respect to the oven.

Abstract: Low attenuation, low dispersion of optical waveguides are provided by a process initiating with axial deposition of a high velocity core soot stream impinging on a target at a high angle of incidence relative to the axis of rotation of the target. A core cylinder is built up axially by relative movement between the soot stream and target during deposition, the movement being non-constant in order to maintain a substantially constant diameter with a constant deposition rate. A cladding layer is then built up by deposition of soot radially on the core. Subsequent drying and sintering provides a vitreous preform which may be drawn directly into optical waveguides. Alternatively, the sintered product may be drawn down to smaller rods, which then are covered with further deposited soot cladding to a desired final thickness, and after further drying and sintering may be drawn to optical waveguides.

Abstract: An optical waveguide fiber with a core region 1 and a cladding region 2, wherein said cladding region 2 includes an outer cladding region 3 is disclosed wherein said outer cladding region 3 is a very thin (less than 1 .mu.m in thickness) layer of TiO.sub.2 --SiO.sub.2 glass which results in a substantial reduction in the number of fiber breaks resulting from the fiber drawing process and having a predetermined TiO.sub.2 concentration less than or equal to about 10 wt. %. A method for making said fiber is also disclosed.

Abstract: The present invention provides a fiber coupler manufacturing apparatus comprising a pair of fiber holding portions and a fiber clamp disposed on each of the fiber holding portions for holding at least two optical fibers. A weight and pulley system is arranged wherein a first weight is coupled to each of the fiber holding portions to pull the fiber holding portions away from each other to apply tension to the optical fibers. A heating unit is disposed between the fiber holding portions and proximate to the optical fibers to heat the optical fibers. A second weight is coupled to either the fiber holding portions or the first weight and rests on a movable platform. As the movable platform descends in a vertical direction, the second weight applies additional force to the fiber holding portions and thus applies additional tension to the optical fibers.

Abstract: A glass preform for an optical fiber containing a dopant in a core portion at a high concentration is produced by providing a glass tube, forming a coating film of a sol-gel solution containing a dopant compound on an inner wall of the glass tube, vitrifying and collapsing the glass tube having the coating of the sol-gel solution to obtain a glass rod.

Abstract: The present invention providesa process for the dehydrating and purifying treatment by heating a porous glass preform for an optical fiber comprising passing the porous glass preform through a muffle tube having a SiC layer at least on its inner surface at a high temperature under an atmosphere comprising an inert gas and a silicon halogenide gas;a process for the fluorine-doping treatment by heating a porous glass preform for an optical fiber comprising passing a porous glass preform through a muffle tube having a SiC layer at least on its inner surface at a high temperature under an atmosphere comprising a fluorine compound gas and an inert gas; anda process for the vitrifying treatment by heating a porous glass preform for an optical fiber comprising passing the preform, which has been previously dehydrated and purified, through a muffle tube having a SiC layer at least on its inner surface at a high temperature under an atmosphere gas.

Abstract: A high-power acceptable optical fiber comprises a core and cladding provided on the outer peripheral surface of the core. The dopant concentrations in the core and cladding each change in the axial direction of the optical fiber. The core has a same relative refractive index profile in any cross section thereof taken in a direction perpendicular to the axial direction thereof. The relative refractive index profile is normalized by a maximum refractive index of the core.

Abstract: A mass production method of hermetic coating optical fiber where a bare fiber drawn from a preform is hermetically coated by CVD method in a reactor vessel, wherein a liquid flushes solid particles or by-products sticking to the reactor inner wall. The liquid may be supplied continuously or intermittently, to flush carbon particles generated during carbon coating process. The invention enables to produce a long hermetic coating optical fiber without choking the reactor, and improves a yield rate and productivity.

Abstract: A vapor deposition method for making preforms from which optical waveguide fibers are drawn wherein at least a first precursor compound is oxidized at one oxidation site and at least a second precursor compound, which is different from the first precursor compound, is oxidized at a second oxidation site. The method is particularly applicable in cases where the first and second precursor compounds are chemically incompatible with one another or where the flow rate of the second precursor compound is substantially lower than the flow rate of the first precursor compound.

Abstract: A first process of the invention comprises forming two constricted portions (28) at a quartz reaction tube (4), charging a solution of a compound of a rare earth element as a solution into the section between the constricted portions (28) for doping. By this, the doping concentration becomes uniform along the length of an optical fiber preform (30) with defects being rarely produced. This process does not involve any complicated operation.A second process of the invention comprises impregnating a solution in the form of a mist in a soot-like core glass (26) by which it becomes possible to control the doping concentration in high accuracy.A third process of the invention comprises impregnating a solution while controlling the concentration in response to a quantity of a transmitted laser beam through a soot-like core glass (26), by which the doping concentration is ensured independently of the density of the soot-like core glass.

Abstract: A hermetic coated optical fiber is produced by preparing a bare optical fiber by melting and drawing an optical fiber preform in a fiber drawing furnace and introducing the bare optical fiber in a reactor in which a raw material gas is introduced and forming a hermetic coating film around a surface of the bare optical fiber by a chemical vapor deposition method or pyrolysis in the reactor, wherein a part of an inert gas for purging the fiber drawing furnace which has been heated by a heater equipped in the furnace is exhausted and a rest of the inert gas is introduced in the reactor for diluting the raw material gas.

Abstract: In a VAD method for making optical fiber preforms, the yield is increased by terminating or significantly reducing the supply of glass raw material to the torch (24) just after glass jacket soot (23, FIG. 4) has been deposited at the bottom end of the glass rod (20). The fuel supply to the torch is maintained, however, and the flame continues to be projected from the torch toward the deposited soot boule (23). The rate of vertical movement of the glass rod is increased until the flame is directed at the bottom end (27') of the soot boule. The flame is then allowed to dwell for a sufficient period to increase significantly the temperature of the bottom end of the soot boule and to consolidate partially the bottom end of the soot boule. This has the effect of containing the soot and countering the effects of gravity on the delicate soot boule that might otherwise cause it to crack.

Abstract: Metal halide compositions of enhanced purity are produced by vapor phase deposition via reactions involving organometallic starting materials in a process wherein a carbon getter is provided in the reaction zone and/or adjacent the developing metal halide deposit. The carbon getter reduces carbon contamination in the product which can result from side decomposition reactions involving the organometallic starting materials.

Abstract: A method of manufacturing a radiation-resistant optical fiber includes steps of a) heating a bare optical fiber to remove residual hydrogen gas present in the bare optical fiber and b) forming a coating layer consisting of a substance which does not allow permeation of hydrogen gas on the surface of the bare optical fiber from which the residual hydrogen gas has been removed.

Abstract: There is disclosed an optical waveguide comprising a K.sub.1-x Rb.sub.x TiOmO.sub.4 single crystal substrate, wherein x is from 0 to 1 and M is P or As, having at least one optically smooth surface wherein sufficient K.sup.+ and/or Rb.sup.+ have been replaced by ions selected from at least one of H.sup.+ and NH.sub.4.sup.+ and, optionally, at least one monovalent ion selected from Rb.sup.+, Cs.sup.+, Tl.sup.+, and/or at least one divalent ion selected from Ba.sup.+2, Sr.sup.+2, Ca.sup.+2 and Pb.sup.+2 to chance the surface index of refraction at least a 0.00025 with respect to the index of refraction of the single crystal substrate. One process disclosed for producing an optical waveguide comprises the steps of contacting at least one optically smooth surface of a single crystal of K.sub.1-x Rb.sub.x TiOmO.sub.4 with an ion exchange medium capable of supplying said replacement ions, at a temperature of from about 100.degree. C. to about 600.degree. C.

Abstract: A heating furnace for heating a porous preform made of fine particles of quartz base glass for an optical fiber which comprises a heater and a muffle tube positioned inside the heater to separate a heating atmosphere from the heater, wherein the muffle tube body consists of highly pure carbon and an inner wall and an outer wall of the body is coated with a carbon material selected from the group consisting of pyrolytic graphite and solid-phase carbonized glassy carbon.

Abstract: A glass soot deposit is produced at a high deposition rate by blowing a gaseous glass-forming raw material together with a fuel gas from a combustion burner in a closed muffle, hydrolyzing the glass-forming raw material in a flame to generate glass soot, and depositing the glass soot on a tip end or a peripheral surface of a starting member which is rotated to form a glass soot deposit, in which a lowest surface temperature of the muffle tube is maintained at 50.degree. C. or higher and an average surface temperature of the muffle is maintained in a range between 50.degree. C. and 150.degree. C., whereby corrosion of the muffle is prevented.

Abstract: The method of manufacturing a silica glass preform comprises the steps of inserting a rod-like member mainly containing a ductile material, into a forming space of a mold, charging the remaining space of the forming space with a forming material containing silica glass powder or doped silica glass powder, compressing the mold charged with the forming material from outside such as to form a porous glass body of the forming material around the rod-like member, removing the rod-like member from the porous glass body, inserting a glass rod into the hole formed after removal of the rod-like member, purifying said porous glass body in which the glass rod is inserted, and consolidating said porous glass body purified in the above purifying step.

Abstract: The invention is a method for producing a porous preform for use in the fabrication of an optical fiber at least two burners synthesize glass soot particles, one of which generates a double-layer flame and one of which is used for forming a core part of the preform. The method comprises the steps of supplying SiCl.sub.4 and optionally GeCl.sub.4 to the inner flame of the double-layer flame, and only SiCl.sub.4 to an outer flame of the double-layer flame to flame hydrolyze the supplied compounds and synthesize glass soot particles. Compounds SiCl.sub.4 and GeCl.sub.4 as glass-forming raw materials are supplied to the burner for forming the core part of the preform by depositing the generated glass soot particles on the lower end of a rotating starting member. The generated porous preform comprises a core part containing at least partly GeO.sub.2, and a surface having a low concentration of GeO.sub.2 which reduces cracking or peeling.

Abstract: Disclosed is a method of forming a doped glass article. Heated glass particles are deposited on a mandrel where they adhere together to form a porous glass preform having interconnective pores. The mandrel is removed to form a tubular preform having an axial aperture. The preform is suspended in a consolidation furnace by a gas conducting handle having a dopant containing chamber. As the handle and preform are heated, there is flowed through the chamber a gas that reacts with the heated dopant to form a reactant gas that flows into the aperture and into pores, whereby a dopant is incorporated into the porous glass preform. The doped preform is heat treated to consolidate it into an elongated non-porous glass body containing the dopant. The glass body can be provided with cladding glass and drawn into an optical fiber.

Abstract: A glass preform for use in the fabrication of an optical fiber having a reduced transmission loss is produced by synthesizing a soot preform by a vapor synthesis method and consolidating the soot preform in an electric furnace to obtain a glass preform, wherein an intermediate body consisting of a core portion and an inner part of a cladding portion is consolidated under atmospheric pressure and an outer part of the cladding portion which surrounds a periphery of the intermediated body is consolidated under reduced pressure or in vacuo.

Abstract: A method of producing a hollow core optical fiber comprises the steps of depositing a thermal buffer layer on the interior wall of a silica tube, depositing a film of germanium silicate cladding on said buffer layer, heating the composite structure so formed to its drawing temperature, and drawing the heated composite structure to form a hollow core optical fiber.

Abstract: A method for producing a glass preform, which method comprises forming a soot preform of glass fine particles comprising SiO.sub.2 by flame hydrolysis or solution hydrolysis of a starting glass material and sintering the soot preform in an atmosphere containing at least SiF.sub.4 to obtain a glass preform which is free from an increase in absorption due to impurities and has sufficiently low attenuation of light transmission.

Abstract: A method and apparatus for rapidly forming a porous glass preform is provided in which an array of burners is oscillated along a path parallel to the longitudinal axis of the preform. Unlike existing soot deposition techniques, the oscillation amplitude is limited so that each burner deposits soot on only a portion of the preform, e.g., 20% of the preform. By controlling inter-burner variability and the air flow in the burner-array/preform region, preforms having substantially uniform axial properties are obtained notwithstanding the fact that different burners are used to laydown different parts of the preform.

Abstract: Redeposition of glass particles is prevented by a method for heating a glass body comprising heating a part of the glass body with relatively moving the glass body and a heating source, wherein an inert gas is blown from inert gas-blowing means onto a surface of the glass body near a heated part of the glass body.

Abstract: A method for producing internally coated glass tube preforms for drawing er optic conductors. The internally coated glass tubes are halogen coated, preferably coated with metal fluorides, so that an optical fiber formed will have a halogen core which conveys light having a wavelength of about 2 to 4 microns, which is in the infrared region, with low attenuation. With one aspect of the method, a carrier gas and a halogenated alkoxide are introduced into a glass tube which has an inner wall and which is surrounded by a resonator for producing a plasma from the halogenated alkoxide in the tube. With another aspect of the method, a blend of a carrier gas, an organometallic compound, and a halogen-containing gas are introduced into a glass tube which has an inner wall and which is surrounded by a resonator for producing a plasma. In both cases, the tube is moved relative to the resonator to form a plasma zone within the tube such that a halide coating is formed on the inner wall of the tube.

Abstract: In the optical fiber, the concentration of fluorine doped in the core portion is made nonuniform in the radial direction to be greater at the center portion of the core portion and less at the outer circumferential portion of the core portion. As a result, the distribution of the refractive index of the core portion and the cladding portion before the process of transparent glassification becomes a profile which is high at the outer circumferential portion of the core portion and which is low at the center portion. The reduction of the refractive index at the outer circumferential portion of the core portion due to the dispersion of the GeO.sub.2 etc., the oxide included in the core portion, in the cladding portion in the transparent glassification processed is and as a result, the profile of the refractive index of the core portion becomes one which sticks out in a step form with respect to the cladding portion.

Abstract: A glass article is produced at a high production rate and a high yield by jetting a glass-forming raw material from a multi-port burner, synthesizing glass soot through hydrolysis of the glass-forming raw material, depositing the glass soot to form a soot preform and heating and vitrifying the soot preform to produce a transparent glass article, wherein the glass-forming raw material is vaporized by heating it at a temperature higher than its boiling point and directly supplied to the burner, the vaporized glass-forming raw material and a fuel gas for synthesizing glass soot are supplied to an inner port of the multi-port burner and a fuel gas for heating a formed preform is supplied to an outer port of the multi-port burner, and a molar ratio of water generated by a reaction of the fuel gas for synthesizing glass soot to the glass-foring raw material is from to 2 to 3.

Abstract: A method and an apparatus for measuring the thickness of a coating provided around a cylindrical object such as an optical fiber optically. The cylindrical object is irradiated by a measuring light and the light derived from the object is received by a photo-detector so that the intensity of the derived light is measured to thereby detect the thickness of the coating.

Abstract: An improved method for making preforms by vapor deposition soot laydown processes is provided wherein an oxidizing atmosphere is used during at least part of the laydown process, e.g., during the laydown of the center portion of the preform. The use of such an atmosphere has been found to result in enhanced dopant capture, reduced axial trends, and an overall stabilization of the laydown process. A method for selecting burner flows which optimize the laydown process is also provided.

Abstract: A preform tube (31) is caused to be collapsed into a preform rod by causing a heat zone (54) provided by a torch assembly (50) to traverse the tube longitudinally in a plurality of passes. During this so-called collapse mode, a muffle tube (100) encloses that portion of the tube which extends through the torch assembly. Advantageously, the muffle tube projects a predetermined distance beyond one major face of the torch assembly. The torch assembly comprises annular semi-circular end plates and an annular semi-circular center portion having a plurality of exit ports through which gases are directed into engagement with the tube. The center portion is caused to be recessed between the end plates thereby causing the heat zone generated by the gases to be narrowed.

Abstract: Disclosed is a method of forming a glass tube doped with boron and fluorine. A B.sub.2 O.sub.3 -doped tubular porous preform is heated, and a fluorine-containing gas is flowed into its aperture. The temperature is sufficiently high to cause the fluorine-containing gas to decompose and form fluorine which dopes the preform. Also flowed into the aperture is a sufficient amount of BF.sub.3 to prevent fluorine from reacting with the B.sub.2 O.sub.3 in the porous preform and forming a B.sub.2 O.sub.3 -depleted region near the aperture surface. The particles are then fused to form a fluorine-containing dense glass tube.

Abstract: A glass preform which is used for fabricating an optical fiber, has substantially no bubbles therein and contains sufficient amount of fluorine is produced by a method comprising steps of: forming a porous glass soot body from a glass-forming raw material, removing trapped gas and water from pores of the soot body by heating the soot body under pressure lower than several ten Torr. at a temperature at which the soot body is not vitrified, filling the pores of the soot body with a gas containing SiF.sub.

Abstract: Method of outside plasma deposition onto a rod (17,22) of silica substantially free from hydroxyl ions, possibly doped to change its refractive index, by reaction with oxygen of a silicon compound and possibly of doping compounds, in the presence of a gas plasma raised to a very high temperature (16) by induction with the help of a high frequency generator (15). The rod on which the silica deposit is made is kept in a sealed chamber (19) separated from the surrounding atmosphere and supplied by a pipe (20) with atmospheric air that is successively passed through a filter (31), a compressor (32) a cooling means (33), a condensation water drain (35) and a final desiccation by adsorption (36, 38). A device for implementing the method is also claimed.

Abstract: In the PCVD method glass is deposited in layers on the inner wall of a glass tube by heating the tube to a temperature between 1100.degree. and 1300.degree. C., by passing a reactive gas mixture through the glass tube from a gas inlet side at a pressure between 1 and 30 hPa, by forming a plasma in the interior of the glass tube, and by reciprocating the plasma between two reversal points. After a quantity of glass corresponding to the desired fiber optical construction has been deposited, the tube is collapsed to form a solid preform from which optical fiber are draw. The range of nonconstant deposition geometry at the preform entrance, (i.e. on the gas inlet side), is reduced by interrupting the reciprocating movement of the plasma at the reversal point on the gas inlet side.

Abstract: An optical fiber soot synthesis apparatus which synthesizes around a fiber starting member forming a core of an optical fiber an optical fiber soot forming a cladding and which accurately calculates in real time the mass of the optical fiber soot when deposited so as to control the synthesis of the optical fiber soot. The optical fiber soot synthesis apparatus measures the weight of the rotating fiber starting member and optical fiber soot by a pair of soot weight detection sensors arranged at a fiber starting member support and rotational drive mechanisms divided so as to prevent the weight of the rotational drive mechanisms from having much of an effect. The computation and control apparatus performs operational processing from the measured weights and calculates the mass of only the optical fiber soot synthesized on the fiber starting member in real time. The computation and calculation apparatus refers to the calculated mass to control the synthesis of the optical fiber soot.

Abstract: A method of making an optical waveguide fiber with a fatigue resistant TiO.sub.2 -SiO.sub.2 outer cladding, and a substantially glass blank for drawing into such fiber, wherein a glass soot TiO.sub.2 -SiO.sub.2 outermost layer, with an initial TiO.sub.2 concentration greater than 10.5 wt. %, is deposited on a preform, and the preform is exposed to an atmosphere of chlorine and oxygen at a high temperature, and the resulting TiO.sub.2 concentration in the outermost layer of the TiO.sub.2 -SiO.sub.2 outer cladding of the substantially glass blank is less than the initial TiO.sub.2 concentration. In the glass blank form, the outermost layer includes a substantial volume percentage of crystalline phases and in the fiber form, the outermost layer includes inhomogeneities.

Abstract: A method of making an optical fiber having an oblong core comprising the steps of depositing layers of core glass particles and cladding glass particles on an enlarged mandrel, removing the mandrel to form a tubular porous preform, consolidating the porous preform to form a dense glass preform, evacuating the central hole of the dense glass preform while stretching that preform to collapse the central hole thereof and form a flattened rod, applying cladding material to the rod, and drawing the resultant composite to form an optical fiber. To facilitate the flat collapse of the central hole of the dense glass preform and to cause the core to have a large aspect ratio, the inside diameter-to-outside diameter ratio of the dense glass preform should be within the range of 0.3 to 0.9. For preferred core and cladding glasses, this ratio should be between 0.5 and 0.6. Also, the mandrel diameter should be at least 12 mm, and it is preferably between 25 mm and 50 mm.

Abstract: A preform tube (31) is caused to be collpased into a preform rod by causing a heat zone (54) provided by a torch assembly (50) to traverse the tube longitudinally in a plurality of passes. During this so-called collapse mode, a muffle tube (100) encloses that portion of the tube which extends through the torch assembly. Advantageously, the muffle tube projects a predetermined distance beyond one major face of the torch assembly. The torch assembly comprises annular semi-circular end plates and as annular semi-circular center portion having a plurality of exit ports through which gases are directed into engagement with the tube. The center portion is caused to be recessed between the end plates thereby causing the heat zone generated by the gases to be narrowed.

Abstract: An optical waveguide that has low (0.16 to 0.28 db/km) attenuation but can be subjected to sharp radii of curvature of the order of 2 mm has an index of refraction difference between core and cladding of less than 0.75% and a cutoff wavelength that is 50 micrometers or more greater than the operating wavelength. The waveguide is a "virtual single mode" device, because even though a second order mode can be sustained in the waveguide, the waveguide length or bending losses, or both, differentially attenuates the second order mode so that the primary mode strongly predominates and both modal noise and attenuation are within acceptable limits.

Abstract: In accordance with the present invention, the dopant within one gradient index optical element has two independent concentration distributions. Particularly to use the present invention to obtain a gradient index optical element having an excellent chromatic aberration correction ability, it is only needed to make such dopant distributions as shown in the previously stated Japanese Patent Application No. 280897/1989. However, as to the doping of a dopant into a porous body, there is a limit in the amount which can be doped. This is a disadvantage of the molecular stuffing method, but the reason for this is that the dopant must be supplied into the holes as a solution and it is largely restricted by the solubility of the dopant in the solvent. In addition, since the intra-hole fixing of the dopant depends on the solubility difference by temperature or that by solvent exchange, it is further restricted.

Abstract: A glass tube (31) from which optical fiber is to be drawn is heated by a torch assembly comprising a plurality of nozzles (54--54) disposed on a carriage. In order to avoid contamination of the tube by particles of the torch assembly resulting from thermal degradation,the nozzles are disposed in a plane which is normal to an axis (36) of the tube with each nozzle axis inclined so that flame fronts associated with the nozzles are substantially closer to the tube than to the torch assembly. Reaction of materials which are flowed into the tube is enhanced by including a second row of nozzles (91--91) which are inclined within a plane which is inclined to the longitudinal axis of the tube. In order to collapse the tube into a rod, a muffle member (100) preferably is caused to be disposed about the tube with an opening in the periphery of the muffle member to allow portions of the gas flows to converge and to allow heat energy to be transferred from the flame fronts to the tube.

Abstract: A method for producing a glass preform for use in the fabrication of an optical fiber, which comprises adding fluorine to a soot preform in an atmosphere comprising a fluorine-coating compound at a temperature at which the soot preform is in the porous state and then keeping or inserting it in an atmosphere containing a fluorine-containing compound at a higher temperature to vitrify it to form a glass preform, from which glass preform, an optical fiber homogeneously containing fluorine is fabricated.

Abstract: For the drawing of an optical fiber from a solid blank, the latter is conducted vertically through a furnace and, during this process, is heated to the drawing temperature at its lower end, from which the fiber is drawn out in the form of a drawing onion. The drawn fiber is then cooled down from the drawing temperature by means of a gas stream moving in the opposite direction to the drawing direction and, in this process, a rotational flow is impressed on the cooling gas stream in addition to the longitudinal flow.

Abstract: A method for producing a glass preform for use in the fabrication of an optical fiber, which includes the steps of forming a glass soot preform from a glass-forming raw material and heating the soot preform in an atmosphere containing SiF.sub.4 under a pressure higher than 2 atm. for a period of time sufficient to add fluorine during the time between the formation of the soot preform and the vitrification of it, fluorine is added at a high rate and in a larger amount.

Abstract: A method of fabricating preforms for making optical fibers by drawing, in which a silica deposit, including a doping agent, is formed in successive layers inside a silica-based tube (1) from a chemical vapor containing a gaseous compound of silicon, oxygen, and a gaseous compound of an element for doping the silica, with the composite tube then being subjected to collapsing so as to cause the empty axial zone (3), the tube hollow, to disappear. The silica of the initial tube is then eliminated, by removal, after which a recharge of silica (5) is made around the remaining cylinder (4) by plasma torch deposition from a gas comprising oxygen and a halogen derivative of silica.

Abstract: This invention relates to production of high purity fused silica glass doped with titania through oxidation or flame hydrolysis of a gaseous mixture and containing rutile crystals comprising a vaporizable, silicon-containing compound. Titanium-2-ethylhexyloxide, titanium cyclopentyloxide, and a titanium amide, or a combination thereof, constitute the operable titanium-containing compounds.