Abstract: Apparatuses and methods for processing optical fiber preforms are disclosed. According to one aspect, an apparatus generally includes a furnace body and a muffle disposed within the furnace body. A space between the muffle and the furnace body defines a first interior volume. The muffle defines a second interior volume sealed from the first interior volume. An annulus gas is supplied to the first interior volume and a process gas is supplied to the second interior volume. A differential pressure gauge is coupled to the interior volumes. A flow controller is coupled to at least one of the gas sources and to the differential pressure gauge. The flow controller receives a differential pressure signal from the differential pressure gauge and adjusts a flow of a gas such that the pressure differential between the first interior volume and the second interior volume is minimized.

Abstract: An optical fiber manufacturing method includes: drawing an optical fiber preform to form a bare optical fiber; cooling the bare optical fiber; coating an uncured coating layer that includes a resin precursor on an outer periphery of the bare optical fiber; curing the uncured coating layer to form a semi-cured coating layer; further curing the semi-cured coating layer; and cooling the semi-cured coating layer by at least one non-contact direction changer between the curing of the uncured coating layer and the curing of the semi-cured coating layer.

Abstract: An optical fiber draw furnace muffle includes a body portion defining a substantially cylindrical cavity extending along a centerline axis of the muffle. A tapered portion has an interior surface which defines a first curved portion with a first radius of curvature and a second curved portion with a second radius of curvature. At least one of the first and second radii of curvature has a radius greater than a radius of the cylindrical cavity.

Abstract: A system for drawing optical fiber in microgravity including a sealed housing to prevent infiltration of at least humidity and filled with a dry environment, a preform holder located within the sealed housing to hold preform material, a furnace located within the sealed housing to receive the preform material from the preform holder and to heat the preform material from which the optical fiber is pulled, a feed system to move the preform material from the preform holder to the furnace, a drawing mechanism located within the sealed housing to pull the optical fiber from the preform material within the furnace, a diameter monitor located within the sealed housing to measure a diameter of the optical fiber and a fiber collection mechanism located within the sealed housing to gather and store the optical fiber.

Abstract: A method for producing substrate tubes of quartz glass includes continuously supplying a hollow cylinder of quartz glass to a heating zone, softening the hollow cylinder zonewise in the heating zone, and drawing off a tubular strand from the softened portion. The hollow cylinder has an outer diameter Ca, an inner diameter Ci and an inner bore. The tubular strand has an outer diameter Ta and an inner diameter Ti. The following parameters are applicable to the hollow cylinder and the tubular strand: Ca>180 mm, Cr>3 with Cr=Ca/Ci, Tr<1.6 with Tr=Ta/Ti and Ci/Ti<2.5. The blow pressure in an inner bore is adjusted to a value in the range of 4 to 10 mbar. Substrate tubes, obtained by cutting the tubular strand to the desired length, serve as semi-finished products for the manufacture of preforms for optical fibers.

Abstract: A method of processing an optical fiber of the invention includes: a determination step of determining at least an ambient temperature of conditions of a diffusion treatment that causing an optical fiber to be subjected to an non-oxygen bridging atmosphere; an exposure step of exposing the optical fiber to a gas including an oxygen bridging element that is capable of processing the Non-Bridging Oxygen Hole Centers by being bonded to a non-bridging oxygen in the optical fiber, and causing the oxygen bridging element to infiltrate into the optical fiber; and a diffusion step of subsequently causing the optical fiber to be subjected to the non-oxygen bridging atmosphere in the exposure ambient temperature which is determined by the determination step and at which the optical fiber is subjected to the non-oxygen bridging atmosphere, and thereby diffusing the oxygen bridging element into the optical fiber.

Abstract: A manufacturing method of an optical fiber includes drawing an optical fiber preform and forming a bare optical fiber, coating an outer circumference of the bare optical fiber with a coating layer including a resin, curing the coating layer and forming an optical fiber by curing the coating layer, and changing a direction of the bare optical fiber using one or a plurality of direction changing devices at any position between a position where the bare optical fiber is formed and a position where the coating is performed. The direction changing device includes a guide groove which guides the bare optical fiber, and an internal space portion into which a fluid is introduced from an outside, and in the guide groove, an outlet through which the fluid in the internal space portion is blown to float the bare optical fiber in the guide groove is formed.

Abstract: A manufacturing method of an optical fiber includes drawing an optical fiber preform and forming a bare optical fiber, coating an outer circumference of the bare optical fiber with a coating layer including a resin, and holding the bare optical fiber using one or a plurality of non-contact holding portions at any position between a position where the bare optical fiber is formed and a position where the coating is performed. The non-contact holding portion includes a guide groove which guides the bare optical fiber, and an internal space portion into which a fluid is introduced from an outside, in the guide groove, and an outlet through which the fluid in the internal space portion is blown to float the bare optical fiber in the guide groove is formed.

Abstract: Method for removing bubbles from a molten substrate. The molten substrate from a furnace passes through a downtube to reach additional manufacturing tools, such as an extrusion bushing. One or more ultrasonic sensors are arranged along the downtube. The ultrasonic sensor(s) transmit ultrasonic energy into the molten substrate and measure a characteristic of the ultrasonic energy, such as a propagation time for the ultrasonic energy to be reflected back to the ultrasonic sensor(s). A bubble is detected when a change in the Characteristic of the ultrasonic energy is detected. When a bubble is detected, flow through the downtube is diverted to a duct to remove a slug of molten substrate that includes the bubble.

Abstract: A method for forming an optical fiber preform and fibers drawn from the preform. The method includes forming a soot cladding monolith, inserting a consolidated core cane into the internal cavity, and processing the resulting core-cladding assembly to form a preform. Processing may include exposing the core-cladding assembly to a drying agent and/or dopant precursor, and sintering the core-cladding assembly in the presence of a reducing agent to densify the soot cladding monolith onto the core cane to form a preform. The preform features low hydroxyl content and low sensitivity to hydrogen. Fibers drawn from the preform exhibit low attenuation losses from absorption by the broad band centered near 1380 nm.

Abstract: In harsh and hazardous environments, the presence of elevated levels of hydrogen gas is an indicator of chemical and/or radiological activity. The present hydrogen-sensing optical fiber provides rapid and reliable hydrogen detection and quantification, irrespective of temperature fluctuations. The hydrogen-sensing optical fiber does not exhibit significant irreversible hydrogen-induced attenuation losses after exposure to a hydrogen-rich atmosphere.

Abstract: Apparatus, systems and methods for making a fibrous products form molten material into fibers. The fibers are sprayed with a coolant liquid to cool the fibers. A flow rate of the sprayed coolant liquid is controllable. The fibers are also sprayed with a binder dispersion. The fibers are directed toward a conveyor to form an uncured fibrous pack. A thickness of the uncured pack is measured and the flow rate of the sprayed coolant liquid is controlled based on the measured thickness of the uncured pack.

Abstract: In the method for manufacturing a glass-fine-particle-deposited body according to the present invention, at least a part of a gas supplying pipe 25 from a temperature controlled booth 24 to a burner 18 for cladding is temperature-controlled so that the temperature at the burner side becomes high and temperature gradient becomes 5° C./m or more. The temperature control is performed so that the temperature gradient becomes preferably 15° C./m or more, more preferably 25° C./m or more. Specifically, the part is controlled to the predetermined temperature gradient by winding a tape heater 26 that is a heating element on the outer circumference of the gas supplying pipe 25 from the temperature controlled booth 24 to the burner 18 for cladding and temperature-controlling the tape heater 26.

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 coloring optical fibers during the optical fiber drawing that includes the steps of feeding a natural fiber coating material and a colorant to a mixer; mixing the natural fiber coating material and the colorant in the mixer to obtain a colored coating material; and supplying the colored coating material to a coating die. The feeding step includes exerting on the natural fiber coating a first gas pressure variable with at least one fiber drawing parameter; and exerting on the colorant a second gas pressure variable with at least one fiber drawing parameter.

Abstract: A method of manufacturing an optical fiber base material includes: forming a porous glass base material by depositing glass particles; providing a vessel which employs a composite tube, the composite tube including a portion formed by jacketing a first quartz glass containing aluminum equal to or less than 0.01 ppm with a second quartz glass containing aluminum equal to or more than 15 ppm; introducing dehydration reaction gas and inert gas into the vessel; heating the jacketed portion in the vessel which contains the dehydration reaction gas and the inert gas; and inserting the porous glass base material into the heated vessel to dehydrate and sinter the porous glass base material.

Abstract: A porous preform production apparatus having a reaction vessel which includes an upper deposition chamber having an air supply inlet and an exhaust outlet, a lower deposition chamber having an air supply inlet, and a top chamber disposed on top of the upper deposition chamber and adapted to lift and store a porous preform formed by deposition, characterized in that the floor of the upper deposition chamber is disposed at a height between the lower end of a straight body part and the deposition tip of the porous glass preform during deposition, and a connection opening which connects the upper deposition chamber with the lower deposition chamber, is provided on the floor of the upper deposition chamber, and that when the aperture diameter of the connection opening is designated as A and the diameter of the porous preform passing through the connection opening as B, the ratio B/A satisfies the expression 0.05?B/A?0.6.

Abstract: A gas supplying unit supplies a nitrogen gas into a furnace body of a graphite heating furnace in which at least a part of the furnace body is formed with a graphite. An exhausting unit exhausts a gas inside the furnace body to outside the furnace body. A dew-point temperature of the nitrogen gas supplied into the furnace body is equal to or lower than ?80° C. A pressure inside the furnace body is equal to or higher than 140 Pa with respect to an atmospheric pressure outside the furnace body.

Abstract: A method of manufacturing an optical fiber base material includes: forming a porous glass base material by depositing glass particles; providing a synthetic quartz glass vessel at least partly made of quartz glass which contains aluminum equal to or less than 0.01 ppm; introducing dehydration reaction gas and inert gas into the vessel; heating a portion made of quartz glass which contains aluminum equal to or less than 0.01 ppm in the vessel that contains the dehydration reaction gas and the inert gas; and inserting the porous glass base material into the heated vessel to dehydrate and sinter the porous glass base material.

Abstract: An optical fiber production system and method are provided for producing optical fiber. An optical fiber is drawn from a preform in a furnace and passes through a treatment device under a reduced pressure in the range of 0.01 to 0.80 atm. The treatment device cools the bare optical fiber as it cools to a temperature in the range of at least 1,600° C. to 1,300° C. A non-contact fiber centering device is located near an exit of the treatment device to provide centering of the optical fiber as it exits the treatment device.

Abstract: The invention relates to a tapered optical fiber and a method and drawing tower for producing such an optical fiber. The tapered optical fiber comprising a core region that is capable of guiding light along a longitudinal axis of said optical fiber and a cladding region surrounding said core region. The optical fiber comprises a tapered section arranged between a first longitudinal position and a second longitudinal position, said tapered section comprising a first taper section having a first length, L1, over which the optical fiber is tapered down to a taper waist, and a second taper section having a second length, L2, over which said optical fiber is tapered up.

Abstract: The disclosed Plasma Chemical Vapor Deposition (PCVD) process uses the injection of plasma-reactive gas to control deposition oscillation and refractive-index oscillation (e.g., alpha oscillation). This PCVD process, which may employ a modified PCVD apparatus, achieves more uniform glass deposition. This, in turn, results in optical preforms and optical fibers having more uniform optical properties.

Abstract: A method for manufacturing an optical fiber preform is described that includes detecting structural integrity of the tube during a collapsing phase utilizing a fluid flow that is fed to the tube. Also, a system for manufacturing optical fiber preforms is described that comprises a holder configured to hold a tube, a heater configured to heat at least part of the tube to a tube collapsing temperature, and a fluid supply system configured to supply a fluid to the tube held by the holder. The system comprises a tube integrity monitor configured to monitor structural integrity of the tube, during a collapsing phase, by monitoring the fluid.

Abstract: A dehydration-sintering furnace includes a muffle tube that accommodates therein the porous preform, a heater that heats the porous preform from outside of the muffle tube, a furnace body that accommodates the heater at an outer periphery of the muffle tube. When a gas required for dehydrating and sintering the porous preform is supplied in the muffle tube, and a pressure in the muffle tube is measured, an average value of the pressure in the muffle tube P0 and a standard deviation of the pressure in the muffle tube ?0 are controlled to satisfy a relation P0?3×?0>0.

Abstract: A method of manufacturing a microstructured fiber, includes: providing a preform having a plurality of elongate holes; mating at least one, but not all, of the holes with a connector to connect the hole(s) to an external pressure-controller; drawing the preform into the fiber while controlling gas pressure in the hole(s) connected to the pressure-controller.

Abstract: A glass-melting device for producing glass fibers capable effectively reducing inclusion of bubbles into glass fibers to be spun, and a method for producing glass fibers using the same are provided. A glass-melting device 100 for producing glass fibers comprises: a first glass-melting tank 12; a conduit 14 extending downward from the first glass-melting tank 12; a sucking device 18 for exposing the first glass-melting tank 12 to a reduced-pressure atmosphere; a second glass-melting tank 20 provided on a lower portion of the conduit 14 and exposed to an atmospheric-pressure atmosphere; and a bushing 22 provided at a bottom portion of the second glass-melting tank 20 and equipped with a number of nozzles 22a.

Abstract: A method of manufacturing a holey fiber includes forming a preform and drawing the preform. The forming includes arranging a core rod at a center of a jacket tube and arranging capillary tubes having hollows around the core rod inside the jacket tube. The drawing includes heat melting the preform in a heating furnace while controlling at least one of a gas pressure to be applied to insides of the hollows of the capillary tubes, a temperature of the heating furnace, and a drawing speed, based on a structure of air holes to be formed in a first layer from the core region.

Abstract: A method of manufacturing an optical waveguide preform includes providing a first process gas atmosphere to a soot preform contained in a vessel. The first atmosphere is held in the vessel for a first reacting time sufficient to at least partially dope or dry the soot preform. The vessel is then at least partially refilled with a second doping or drying atmosphere. The second doping or drying atmosphere is held in the vessel for a second reacting time sufficient to further dope or dry the soot preform.

Abstract: The invention relates to a method for manufacturing a final optical fiber preform by overcladding, said method comprising the steps of providing a primary preform; positioning said primary preform within at least one tube, wherein the at least one tube partly covers the primary preform to create a zone to be overcladded, being an overclad zone, which overclad zone is located on the primary preform outside the at least one tube; injecting a gas into the annular space between the primary preform and the at least one tube under overpressure relative to the pressure outside the at least one tube; overcladding the primary preform in the overclad zone with an overcladding material using an overcladding device. The invention also relates to an apparatus for carrying out the method. The invention allows overcladding a primary preform at low cost while maximally limiting the incorporation of impurities into the silica overclad.

Abstract: A method of making an optical fiber preform includes depositing silica glass on the inside of a tube substrate via a plasma chemical vapor deposition (PCVD) operation. The parameters of the PCVD operation are controlled such that the silica glass deposited on the interior of the tube substrate contains a non-periodic array of 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 void containing cladding. 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: In a glass processing method according to the invention, in the case of performing chemical vapor deposition or diameter shrinkage of a substrate glass tube G by relatively moving a heating furnace 20 comprising a heating element 21 for annularly enclosing the circumference of the substrate glass tube in a longitudinal direction of the substrate glass tube G with respect to the substrate glass tube G in which an outer diameter is 30 mm or more and a wall thickness is 3 mm or more and is less than 15 mm and an ovality of the outer diameter is 1.0% or less using a glass processing apparatus 1, a temperature of at least one of the heating element 21 and the substrate glass tube G is measured and the amount of heat generation of the heating element 21 is adjusted based on the measured temperature.

Abstract: Microstructured optical fiber and method of making. Glass soot is deposited and then consolidated under conditions which are effective to trap a portion of the consolidation gases in the glass to thereby produce a non-periodic array of voids which may then be used to form a void containing cladding region in an optical fiber. Preferred void producing consolidation gases include nitrogen, argon, CO2, oxygen, chlorine, CF4, CO, SO2 and mixtures thereof.

Abstract: A non-contact method for measuring the tension applied to a drawn optical fiber includes drawing an optical fiber and displacing the optical fiber by applying a pressurized fluid to the optical fiber. The pressurized fluid may be applied to the optical fiber using a fluid bearing. The fluid bearing may include a fiber support channel. The optical fiber may be directed through the fiber support channel and is displaced relative to the fluid bearing by supplying the pressurized fluid to the fiber support channel. The displacement of the optical fiber caused by the application of the pressurized fluid to the optical fiber may then be measured. The tension applied to the optical fiber may then be determined based on the determined displacement.

Abstract: The invention relates to a method and an apparatus for positioning a feeder needle, and to a production line for optical components, in which a feeder needle of an apparatus for portioning fluid material, preferably softened glass, in particular of a needle feeder, has its position relative to a seat for the feeder needle recorded by means of a force-measuring device, and to further apparatuses which realize this method and to objects produced by the process.

Abstract: A method of fabricating a photonic crystal or photonic band gap optical fiber comprises providing a preform that includes a plurality of holes in an outer diameter, wherein the holes extend from a first end of a preform to a second end of the preform, and forming at least one radially inwardly-extending slot within the preform such that the slot intersects at least some of the holes, wherein the slot does not intersect at least one hole. The method also includes establishing a first pressure in the holes intersected by the slot by introducing the first pressure to the slot, and establishing a second pressure in the at least one hole not intersected by the slot by introducing the second pressure to an end of the at least one hole not intersected by the slot. The method further includes drawing the preform into a fiber while independently controlling the first and second pressures.

Abstract: A method is described for manufacturing an optical fiber preform, including a tube collapsing phase, and including monitoring the concentration of at least one fluid component of a fluid that is exhausted from the tube, to detect structural integrity of the tube. A system is also described for manufacturing optical fiber preforms. The system comprising a holder configured to hold a tube, a heater configured to heat at least part of the tube to a tube collapsing temperature, a fluid exhaust configured to discharge fluid from the tube, held by the holder. The system also includes a tube integrity monitor configured to monitor structural integrity of the tube, during a collapsing phase, by monitoring fluid that is discharged from the tube.

Abstract: A method for manufacturing an optical fiber preform is described that includes detecting structural integrity of the tube during a collapsing phase utilizing a fluid flow that is fed to the tube. Also, a system for manufacturing optical fiber preforms is described that comprises a holder configured to hold a tube, a heater configured to heat at least part of the tube to a tube collapsing temperature, and a fluid supply system configured to supply a fluid to the tube held by the holder. The system comprises a tube integrity monitor configured to monitor structural integrity of the tube, during a collapsing phase, by monitoring the fluid.

Abstract: A method and device for vaporizing a liquid reactant. A vaporizing plate having a top surface defines a liquid flow channel, the channel being laterally delimited by edges having a height greater than a minimum thickness of liquid reactant required to generate vapor under film or nucleate boiling regime. A heating system is associated to the vaporizing plate for heating the liquid reactant over a minimum temperature required to generate vapor under nucleate or, preferably, film boiling regime. A cap covers the vaporizing plate to collect the vapor at a predetermined pressure and provided with a vapor exit and a liquid feeder feeds the liquid reactant onto the vaporizing plate.

Abstract: A mold-press forming apparatus for applying a molding pressure to a mold containing a forming material to perform press forming includes a loading chamber (that is, an airtight chamber) P1 kept airtight. The loading chamber P1 is connected to a pressure reducing member which includes evacuating members 14 and 13 arranged in an evacuating path 7 connected to the loading chamber P1 for evacuating a gas in the loading chamber P1, and a plurality of valves 11 and 12 arranged in the evacuating path 7 in parallel to each other. When the loading chamber P1 is evacuated, the pressure reducing member changes a pressure reducing rate in the course of pressure reduction.

Abstract: A method of making optical quality films is described. A silica film is deposited on a wafer by PECVD (Plasma Enhanced Chemical Vapor Deposition). The deposited film is then subjected to a first heat treatment to reduce optical absorption, wafer warp, and compressive stress. A second film is deposited. This step is then followed by a second heat treatment to reduce optical absorption, wafer warp and tensile stress. The two heat treatments have similar temperature profiles.

Abstract: A non-contact method for measuring the tension applied to a drawn optical fiber includes drawing an optical fiber and displacing the optical fiber by applying a pressurized fluid to the optical fiber. The pressurized fluid may be applied to the optical fiber using a fluid bearing. The fluid bearing may include a fiber support channel. The optical fiber may be directed through the fiber support channel and is displaced relative to the fluid bearing by supplying the pressurized fluid to the fiber support channel. The displacement of the optical fiber caused by the application of the pressurized fluid to the optical fiber may then be measured. The tension applied to the optical fiber may then be determined based on the determined displacement.

Abstract: An optical fiber has a section of the first kind having a chromatic dispersion not less than a given positive value x and a negative chromatic dispersion slope at a given wavelength and a section of the second kind has a chromatic dispersion not more than ?x and a positive chromatic dispersion slope at the same wavelength. Another optical fiber has a chromatic dispersion higher than a positive value x and a negative chromatic dispersion slope at a given wavelength band.

Abstract: A Micro-Electro-Mechanical System (MEMS) and double-layer nozzle based high efficiency, lightweight, low cost, compact, portable fiber-optic connector cleaning apparatus useful for various fiber optic communications applications such as fiber optic cable plant maintenance. The double-layer nozzle design enables the delivery of compressed, filtered air and solvent to connector surfaces. A built-in MEMS pump sucks the air and solvent back to remove particles and contaminations without leaving residues and without scratching the connector surfaces. An interchangeable external needle allows the cleaner to quickly adapt to all kinds of fiber optic connectors. No disassembly is required. The connector cleaner is therefore both fast and effective at cleaning various male and female fiber optic connectors. The fiber optic connector cleaner with 3–5 cc solvent weighs less than half a pound and can be held and operated by one hand.

Abstract: To provide a method for producing a glass particle deposit and a method for producing a glass preform, in which outer diameter variation of the glass particle deposit can be reduced to thereby improve quality. A flow rate of clean gas (CG) introduced into a container potion 10 is limited to thereby prevent the outermost layer of a glass particle deposit 20 from being locally cooled and reduce variation in bulk density in the longitudinal direction of the glass particle deposit 20, that is, outer diameter variation and breakage.

Abstract: This invention discloses a method and an apparatus for sintering a gel tube formed by a sol-gel change. The sintering apparatus comprises a reaction chamber for accommodating the gel tube, sealed under a vacuum condition; a vacuum pump for adjusting the degree of vacuum inside the reaction chamber according to a control signal; a vacuum gauge for measuring the degree of vacuum inside the reaction chamber; a movable part for supporting the gel tube and for rotating and vertically moving the gel tube according to the control signal; a temperature sensor for measuring the temperature inside the reaction chamber; a heater for adjusting the temperature inside the reaction chamber according to the control signal so as to sinter the gel tube; and, a controller for controlling the vacuum pump, the heater, and the movable part for sintering the gel tube under the vacuum condition.

Abstract: A light fiber comprising (a) a tubular clad having a predetermined length and (b) a solid core formed by reacting a filler material with which the clad is filled, the clad and the core being closely contacted with each other by shrinkage of the clad, characterized in that: the clad is expandable under pressure, shrinkage of the clad is initiated before the completion of the reaction of the filler material and is carried out in conformity with volume reduction of the core, which accompanies the reaction of the filler material, and the number of air gap between the clad and the core, which is measured per length of 10 m, is 3 or less.

Abstract: A method of producing a glass particle-deposited body having a reduced amount of longitudinal diameter fluctuations with few imperfect points. The method comprises the steps of (a) synthesizing glass particles with at least one burner and (b) moving the at least one burner, a starting material, or both so that the glass particles can adhere onto the surface of the starting material to be deposited there. Two types of vertical spaces in a reaction container are defined; one is the space in which the at least one burner, the starting material's surface onto which the glass particles are to adhere, or both move, and the other is the space enclosed by (a) the position of the at least one burner, (b) the position at which the extended center axis of the at least one burner intersects the opposite wall of the reaction container, and (c) the position of the at least one gas-discharging port.

Abstract: A method capable of stably drawing an optical fiber with a gas-seal system and an apparatus for implementing the method. The method produces an optical fiber 40b by drawing the optical fiber preform 30 by heating and softening the leading-end portion of it while feeding it into a drawing furnace 20. The drawing furnace 20 allows a gas 15 to blow against the optical fiber preform 30. The inside of the drawing furnace 20 is sealed with a seal ring 14U and a shutter 14L located at the top and bottom portions of it, respectively. While the gas 15 is fed, the inner diameter of the seal ring 14U is adjusted according to the diameter of the optical fiber preform 30. Consequently, even when the preform diameter varies, the clearance between the seal ring 14U and the optical fiber preform 30 can be maintained constant, thereby enabling a stable drawing operation.

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

Abstract: The present invention relates to a method of manufacturing a solid preform by moving a heat source parallel to the longitudinal axis of a substrate tube, whose inner surface is coated with one or more doped or undoped glass layers, so as to collapse the substrate tube into the solid preform in a number of passes, with an etchant being supplied to the interior of the substrate tube after a number of passes of the heat source.