Abstract: A device and method for generating long fibers having a nanoscale diameter by combined application of a gas jet and laser radiation. The invention also relates to nanoscale fibers generated by the device and method.

Abstract: A preform element, it production and fiber production methods from preform assemblies are disclosed. The preform element has a length and a center axis along its length, a first and second end defined by its length and an outer preform element surface. The preform element comprises a plurality of longitudinal structures disposed to form longitudinal hole(s) in a background material. At least one slot extending from its outer preform element surface and intersecting at least one of the longitudinal holes, wherein the at least one slot does not fully intersect the preform element. The preform element may be a preform center element or a preform ring element and may be assembled to a form part of a preform assembly for an optical fiber.

Abstract: In a method of forming a conical shape on a glass rod including an effective portion and an ineffective portion adjoining the effective portion to form a conical shape in the effective portion by simultaneously heating a boundary and the vicinity of the boundary between the effective portion and the ineffective portion and pulling an end of the ineffective portion, the temperature of a heater is raised and a heating target on the glass rod is simultaneously moved from the ineffective portion to the boundary.

Abstract: Disclosed herein is an optical fiber comprising a plurality of dopant concentration profiles in a core of the optical fiber; where the first dopant concentration and the second dopant concentration are each varied in a stepwise manner and wherein a ratio of the first dopant concentration to the second dopant concentration is operative to result in an interaction of a fundamental optical mode at a given wavelength with a plurality of acoustic modes thereby increasing a ratio of Brillouin Scattering intensity ratio of secondary, tertiary or quarternary peak relative to a Brillouin Scattering intensity of a primary peak to be greater than 0.4 in a Brillouin Scattering spectrum.

Abstract: Methods of melting particulate feedstocks in a submerged combustion melter employing an arrangement of one or more submerged combustion burners emitting combustion products into turbulent molten material. Operating the burners such that there is established a turbulent melting region extending vertically from the floor to a splash region, the splash region extending vertically between the turbulent melting region and a head space region, the head space region extending vertically between the splash region and the melter ceiling, the ceiling positioned above the floor a height H2. Feeding the particulate feedstock into the splash region through one or more inlet ports, the inlet ports positioned at a height H1 measured from the floor, where H1/H2 ranges from about 0.33 to about 0.67. The SCM may have a baffle extending from the ceiling into the splash region. A particulate feedstock conduit may be employed, having an exit port in the splash region.

Abstract: A water-processing filter having a high dimensional accuracy and an improved filterability (such as a capability to remove turbidity components) is provided. The water-processing filter comprises (A) a hollow cylindrical filter which comprises (a1) a granular activated carbon having a median particle size of 30 to 80 ?m and (a2) a fibrillated fibrous binder. The cylindrical filter (A) has an upstream outer surface having an arithmetical mean deviation of a waviness profile adjusted to not more than 30 ?m and an arithmetical mean deviation of a primary profile adjusted to 35 to 45 ?m. The cylindrical filter (A) may have a downstream inner surface having an arithmetical mean deviation of a waviness profile of not more than 30 ?m and an arithmetical mean deviation of a primary profile of 35 to 45 ?m. The cylindrical filter (A) may have a grounded outer surface.

Abstract: The present invention provides a direct laser writing fabrication method and system for devices having periodic refractive index modulation structures, for example, Bragg gratings. By focusing a modulated pulsed laser beam into a transparent material substrate, a path of laser modified volumes can be formed with modified refractive index compared with the unprocessed material. Modulation of exposure conditions provides periodic or modified periodic waveguide structures such that the waveguide structures exhibit grating responses and can be used for a variety of optical applications, for example, as spectral filters, Bragg reflectors, grating couplers, grating sensors, or other devices.

Abstract: In a device for producing a large-sized porous base material by a VAD process, the cracking and variation of the outer diameter of the base material are suppressed by forming a smooth tapered part, without changing the length of a non-effective part. In producing the porous base material by a VAD process, the time for a gas to reach a flow amount of the gas in a steady state from starting of the deposition is extended more in a burner that deposits glass microparticles on a layer closer to the outside of the base material.

Abstract: In various embodiments, an optical fiber includes a core having a relatively large area selected so as to raise a threshold of stimulated Raman scattering or stimulated Brillouin scattering, or both, the core having a high aspect ratio elongated cross-section and having a first refractive index. The core is narrower in a fast-axis direction and wider in a slow-axis direction, such that the fiber is mechanically flexible in the fast-axis direction and is mechanically rigid in the slow-axis direction.

Abstract: A glass base material elongating method of sequentially feeding rod-like glass base materials hung by a glass base material feeding mechanism into a heating furnace, and pulling a glass rod with a smaller diameter by a pulling chuck at a lower part of the heating furnace, includes: aligning, by an alignment guiding device that guides the glass rod, a guiding center of the alignment guiding device with an axis of the glass rod, the alignment guiding device guiding the glass rod between the heating furnace and the pulling chuck.

Abstract: The present invention relates to a winding section (10) and to an apparatus (20) in a slitter winder for bringing a fastening means onto the surface of each partial web (w?). The apparatus (20) has an applicator head (22, 22?), which is arranged to apply the fastening means onto the web surface. The apparatus (20) has support members (24) by means of which the apparatus can be mounted into the slitter winder and by means of which the apparatus (20) can be arranged movably substantially in a cross-direction with respect to the slitter winder.

Abstract: A method comprises flowing an oxidant and a fuel into a submerged combustion burner in a glass tank furnace, the glass tank furnace receiving a feed of glass forming material and producing molten glass, the burner and furnace comprising a melting system. The melting system has a variable system vibration and/or oscillation due to the nature of submerged combustion. One method includes predicting a value of at least one property, such as viscosity, of the molten glass using the variable system vibration and/or oscillation.

Abstract: A multicore fiber 1 includes a plurality of cores 3 disposed at predetermined intervals and surrounded by a cladding 5. The multicore fiber 1 also includes a marker 7 formed apart from the cores 3. The refractive index of the marker 7 is different from those of the cores 3 and the cladding 5. For example, the marker 7 may be made of a material having lower refractive index than that of the cladding 5. In this case, for example, the cores 3 may be made of germanium-doped quartz. The cladding 5 may be made of pure quartz. The marker 7 may be made of fluorine-doped quartz. Further, the marker 7 may be an empty hole.

Abstract: A twin fiber laser arrangement is configured with active and passive fibers supporting respective signal and pump lights and a reflective coating surrounding the fibers along a section of the arrangement. The passive fiber has regions covered by respective protective layer and coating-free regions alternating with the layer covered regions, wherein the reflective coating is configured to overlap the protective layer which shields the end of the reflective coating from high power pump light.

Abstract: In an apparatus for conveying a glass tube strand or glass rod strand having a cross-section that is different from a circular cross-section, in particular having an oval cross-section, a plurality of support and guide members are arranged, if viewed in the direction of movement of the glass tube strand or glass rod strand, one after the other such that the moving glass tube strand or glass rod strand is directly supported thereon and guided by them. The support and guide members are disposed tilted in said direction of movement so that the moving glass tube strand or glass rod strand is directly supported on edges of the support and guide members. Thus, one-sided heat losses due to heat dissipation via the support and guide members can be significantly reduced to thereby reduce the curvature of the glass tube strand or glass rod strand.

Abstract: Provided is a quartz glass manufacturing method that involves using one or more burners, supplying hydrogen and oxygen to the one or more burners to generate an oxyhydrogen flame, introducing a silicide into the oxyhydrogen flame, forming a porous base material by depositing silicon dioxide generated from a flame hydrolysis reaction with the silicide, and heating and sintering the porous base material to form transparent glass, the method comprising supplying hydrogen that is stored or made at a normal temperature to the one or more burners; controlling a hydrogen flow rate using a measurement apparatus or control apparatus that performs measurement based on heat capacity of a gas; vaporizing liquid hydrogen stored in a low-temperature storage chamber, and supplying the vaporized liquid hydrogen to the one or more burners as backup hydrogen; switching from the hydrogen to the backup hydrogen; and when switching, adjusting the hydrogen flow rate to a value obtained by multiplying the hydrogen flow rate immedia

Abstract: Methods and apparatus are provided for transmitting light along multiple pathways using a multi-core optical device. One example apparatus generally includes a plurality of large diameter optical waveguides, each having a core and a cladding, and a body having a plurality of bores with the optical waveguides disposed therein, wherein at least a portion of the cladding of each of the optical waveguides is fused with the body, such that the apparatus is a monolithic structure. Such an apparatus provides for a cost- and space-efficient technique for feedthrough of multiple optical waveguides. Also, the body may have a large outer diameter which can be shaped into features of interest, such as connection alignment or feedthrough sealing features. For some embodiments, at least some of the cores may have different structural parameters (e.g., size and/or shape).

Abstract: A deposition system for depositing a chemical vapor onto a workpiece is disclosed, including a deposition chamber having a plurality of components for performing chemical vapor deposition on the workpiece. The deposition chamber includes an inner skin made of Hasteloy for sealing the plurality of components and the workpiece from the air surrounding the deposition system, and an outer skin that encloses the inner skin and is separated from the inner skin by an air gap. The outer skin includes vents that create a convection current in the air gap between the inner skin and outer skin of the deposition chamber. The deposition system also has a gas panel for regulating the flow of gases and vapors into the deposition chamber, and a computer for controlling operation of the gas panel and the components in the deposition chamber.

Abstract: Provided is a glass base material elongation method for elongating a glass base material with a large diameter to manufacture a glass rod with a smaller diameter, the method comprising, when elongating a glass base material that has a transparent glass tapered portion at one end of a trunk portion and a glass tapered portion including a non-transparent glass portion at the other end of the trunk portion, prior to the elongation, fusing a hanging dummy to an end of the transparent glass tapered portion, setting the hanging dummy in communication with a feeding mechanism, inserting the glass base material into a heating furnace beginning with the other end, and performing elongation.

Abstract: Processes and systems for producing glass fibers having regions devoid of glass using submerged combustion melters, including feeding a vitrifiable feed material into a feed inlet of a melting zone of a melter vessel, and heating the vitrifiable material with at least one burner directing combustion products of an oxidant and a first fuel into the melting zone under a level of the molten material in the zone. One or more of the burners is configured to impart heat and turbulence to the molten material, producing a turbulent molten material comprising a plurality of bubbles suspended in the molten material, the bubbles comprising at least some of the combustion products, and optionally other gas species introduced by the burners. The molten material and bubbles are drawn through a bushing fluidly connected to a forehearth to produce a glass fiber comprising a plurality of interior regions substantially devoid of glass.

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: Provided is a process for producing an optical fiber including a processing process where an optical fiber work made of a glass is held by a processing apparatus for an optical fiber work to be heated and processed, wherein in the processing process, vibration caused by an abnormality of the optical fiber work in the heated state or vibration caused by an abnormality of a glass body which is a portion of the processing apparatus for an optical fiber work and is in the state where the glass body portion is heated due to the heating of the optical fiber work is detected by using an acoustic emission sensor.

Abstract: A glass base material elongating method of sequentially feeding rod-like glass base materials hung by a glass base material feeding mechanism into a heating furnace, and pulling a glass rod with a smaller diameter by a pulling chuck at a lower part of the heating furnace, includes: aligning, by an alignment guiding device that guides the glass rod, a guiding center of the alignment guiding device with an axis of the glass rod, the alignment guiding device guiding the glass rod between the heating furnace and the pulling chuck.

Abstract: A method for manufacturing an optical fiber preform includes a process A of applying flame polishing to a center glass rod, a process B of determining a ratio ra/rb, which is a ratio of a radius ra of the center glass rod expressed in millimeters with respect to a radius rb of a target optical fiber preform expressed in millimeters, based on a refractive index profile of a target optical fiber preform, and a process C of determining an amount of fine glass particles to be deposited on the center glass rod so that a ratio ra/rb/c falls within a range from 0.002 to 0.01, where “c” is a maximum value of hydroxyl group concentration expressed in ppm in the vicinity of a boundary between the center glass rod and an outer layer, which is formed by depositing fine glass particles on the center rod and by being vitrified.

Abstract: A single-mode fiber with certain parameters into the core of another fiber with different parameters; in particular single-mode guided light of a shorter wavelength is coupled into the core of a fiber which is a single-mode fiber at a longer wavelength but acts as multimode fiber for the shorter wavelength. Fabrication involves use of a model to determine a length of a pre-taper.

Abstract: A method for producing an optical fiber preform. Glass soot particles are formed by jetting and combusting a gaseous glass-forming material and a fuel gas from a burner in the presence of oxygen. The glass soot particles are deposited on a deposition rod while rotating the deposition rod about its axis and reciprocating the burner in parallel to the deposition rod so as to form the preform and varying at least one of the translation velocity of the burner and the rotation velocity of the rod so as to obtain a predetermined radial soot density distribution in the preform.

Abstract: It is an objective of the present invention to provide a method for sintering a porous glass base material that can experience an earthquake or large vibration without the base material falling or decreasing in quality when performing sintering, dehydration, and transparent vitrification on the porous glass base material. Provided is a method of sintering a porous glass base material including sintering by lowering the porous glass base material vertically through a furnace from above while rotating the porous glass base material, the method comprising changing rotational speed of the porous glass base material during the sintering.

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: A method for producing synthetic quartz glass comprises providing a liquid SiO2 feedstock material containing octamethylcyclotetrasiloxane D4, vaporizing the SiO2 feedstock material into vapor, converting the vapor into SiO2 particles, depositing the particles to form a porous SiO2 soot body, and vitrifying the soot body, forming the synthetic quartz glass. To produce cylindrical soot bodies with outer diameters above 300 mm and improved material homogeneity, the liquid feedstock material contains additional components comprising hexamethylcyclotrisiloxane D3 and the linear homolog thereof with a weight fraction mD3, decamethylcyclohexasiloxane D6 and the linear homolog thereof with a weight fraction mD6, and tetradecamethylcycloheptasiloxane D7 and/or hexadecamethylcyclooctasiloxane D8 and the linear homologs thereof with a weight fraction mD7+, wherein the weight ratio mD3/mD6 is between 0.5 and 500 and the weight fraction mD7+ is at least 20 wt. ppm.

Abstract: A method comprises flowing an oxidant and a fuel into a submerged combustion burner in a glass tank furnace, the glass tank furnace receiving a feed of glass forming material and producing molten glass, the burner and furnace comprising a melting system. The melting system has a variable system vibration and/or oscillation due to the nature of submerged combustion. One method includes predicting a value of at least one property, such as viscosity, of the molten glass using the variable system vibration and/or oscillation.

Abstract: A method for manufacturing an optical fiber base material includes producing glass fine particles through a hydrolysis of a glass material gas in a flame created by an oxidizing gas and a combustible gas.

Abstract: A method of manufacturing an optical fiber includes a first step of drawing an optical fiber preform into a glass fiber and disposing a fiber coating on the outer circumference of the glass fiber to form a parent optical fiber; a second step of cutting the parent optical fiber into a plurality of individual optical fibers; a third step of determining, at, at least, one spot of the parent optical fiber, a failure strength F1 and a failure time T; a fourth step of determining a failure strength F2 of each of the individual optical fibers; and a fifth step of selecting an optical fiber having a failure strength F2 of 5.5 kgf or more from the individual optical fibers cut from the parent optical fiber whose failure strength F1 and failure time T satisfy the inequality T>2.6×10?11×exp(4.736×F1).

Abstract: A process for manufacturing an optical fiber, includes the steps of: a) producing a soot core preform by depositing a core material on a substrate; b) removing the substrate from the soot preform leaving an axial cavity along the longitudinal axis of the soot core preform; (c) drying and consolidating the soot core preform so as to obtain a glass core preform having an axial hole corresponding to the axial cavity; d) reducing a diameter of the axial hole; and e) stretching the glass core preform so as to substantially close the axial hole, wherein the process further includes the step of measuring at least one geometric characteristic of the axial hole of the glass core preform.

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 of producing inorganic fibers includes heating and melting an inorganic raw material that includes 70 wt % or more of silica and 10 wt % to 30 wt % of magnesia and calcia in total in a container to obtain a melt having a melt viscosity of 15 poise or less, supplying the melt to a rotor that rotates at an acceleration of 70 km/s2 or more, drawing the melt due to a centrifugal force caused by rotation of the rotor to obtain fibers, blowing the fibers off by blowing air around the rotor, and collecting the fibers to obtain fibers having an average fiber diameter of 5 ?m or less.

Abstract: A method for manufacturing an optical preform via an internal vapour deposition process, wherein during the inside deposition process the velocity of the reaction zone is set so that the velocity of the reaction zone over the length of the supply side-to-discharge side is higher than the velocity of the reaction zone over the length of the discharge side-to-supply side.

Abstract: Apparatus, systems and methods for monitoring and controlling the amount of moisture introduced into the forming hood area in the manufacture of mineral fiber insulation products. Moisture from coolant liquids, binder dispersions and binder diluents are all introduced deliberately into a forming hood; ambient moisture and water from combustion are additional sources. A series of global variable control valves, one for each fluid system; as well as individual variable control valves for each fiberizing unit are provided with associated meters. Sensors monitor fibrous pack conditions and ambient conditions and provide inputs to the valve control system. A specific 3-ring liquid dispensing system is also disclosed.

Abstract: According to one embodiment, there is provided a method of manufacturing a glass preform, including: obtaining a glass-fine-particle deposit by a VAD process; and heating the obtained glass-fine-particle deposit at a high temperature, thereby manufacturing a transparent glass preform, wherein, while depositing glass fine particles, in addition to monitoring a deposition shape of the glass-fine-particle deposit and controlling a pull-up rate of the glass-fine-particle deposit, there is controlled at least any of: flow rates of glass starting gases to be charged into glass-fine-particle producing burners; flow rates of flame forming gases to be charged into the glass-fine-particle producing burners; and positions of the glass-fine-particle producing burners relative to the glass-fine-particle deposit, so that the deposition shape may become a target shape, and wherein the deposition of the glass fine particles is stopped in a case where the deposition shape deviates from the target shape.

Abstract: A method of determining conditioning pulse parameters for an optical element includes directing a pump pulse to impinge on the optical element and directing a probe pulse to impinge on the optical element. The method also includes determining a first time associated with an onset of electronic excitation leading to formation of an absorbing region of the optical element and determining a second time associated with expansion of the absorbing region of the optical element. The method further includes defining a turn-off time for a conditioning pulse between the first time and the second time. According to embodiments of the present invention, pulse shaping of the conditioning pulse enables laser conditioning of optical elements to achieve improvements in their laser induced damage threshold.

Abstract: Techniques and systems suitable for performing low-loss fusion splicing of optical waveguide sections are provided. According to some embodiments, multiple laser beams (from one or more laser) may be utilized to uniformly heat a splice region including portions of the optical waveguide sections to be spliced, which may have different cross-sectional dimensions. According to some embodiments, the relative distance of the optical waveguide sections and/or the power of the multiple laser beams may be varied during splicing operations.

Abstract: A method for cleaning a glass substrate which ensures removal of abrasive and other foreign matter without making a cleaning step complicated involves cleaning the glass substrate by scrubbing using two or more types of cleaning liquid having different Si element elution abilities. The cleaning liquid having the highest Si element elution is used first, and the cleaning liquid having the lowest Si element elution is used last.

Abstract: A method for fabricating a glass substrate containing SiO2 as a main ingredient thereof and having a uniform and minute pattern of stripes formed on the surface thereof by ultraprecision polishing includes a step of inspecting whether or not, at the topmost surface portion of the glass substrate after polishing, a given property of a bound energy of the Si atom with respect to the electrons occupying a 2P orbit as determined by XPS is equal to or less than a predetermined value, and the given property is a shift amount of the bound energy or a half-value width of the bound energy distribution, the predetermined value is 0.10 eV or 2.15 eV, respectively.

Abstract: A method of making a glass is provided in which the time needed for doping a refractive index control substance such as fluorine into a soot glass deposit body can be reduced. The method comprises the steps of: (1) putting a soot glass deposit body in a container; (2) doping a refractive index control substance into the soot glass deposit body by supplying an doping gas into the container, the doping gas containing the substance; and (3) consolidating the soot glass deposit body by heating, wherein the final set-value concentration of the substance is determined beforehand depending on the target refractive index of the glass, and in step (2), the container is supplied with the doping gas including the substance having a concentration set to be higher than the final set-value concentration, and subsequently, the doping gas including the substance having the final set-value concentration is supplied into the container.

Abstract: According to an embodiment of the invention a method of manufacturing optical fiber cane comprises the steps of: (i) providing a core rod manufactured of relatively low viscosity glass; (ii) depositing SiO2 based soot around the core rod to form a soot preform, the soot being of relatively high viscosity material such that the softening point of the low viscosity glass is at least 200° C. lower than the viscosity of the high viscosity outer core region; and (iii) consolidating the soot of the soot preform by exposure to hot zone at temperatures of 1000° C.-1600° C. The soot is consolidated by heating the outer portion of the soot preform at a relatively fast heating rate, the heating rate being sufficient to densify the soot, so as to render the densified material with enough rigidity to confine the heated core rod and to prevent the heated core rod from puddling.

Abstract: A first generation portion divides an object to be analyzed into a plurality of finite elements to generate element division data. A first calculation portion defines and calculates a plurality of meshes dividing the object to be analyzed into units larger than the finite elements. A second generation portion assumes that a friction layer which has a thickness of “0” and a friction coefficient between a conductive material and a composite material of a predetermined value less than 1 exists at the interface between the conductive material and the composite material, and the second generation portion generates mesh data. A second calculation portion uses various solvers to calculate the physical amounts produced in the object to be analyzed on the basis of the mesh data and outputs the analysis result. In other words, the second calculation portion performs a simulation of the behavior of the object to be analyzed.

Abstract: A manufacturing apparatus for an optical waveguide structure including a clad structure having grooves in a curved surface thereof and a clad film attached to the curved surface includes a clad film shape retaining portion that has a curved surface along which the clad film is held. a position checking portion that checks the position of the clad film on the clad film shape retaining portion, and a first position adjusting portion that adjusts the position of the clad film shape retaining portion so that the clad film on the clad film shape retaining portion is disposed at a reference position while checking the position of the clad film with the position checking portion.

Abstract: Various embodiments of the present invention relate to glass fiber forming bushings, to methods of controlling the temperature of bushings having multiple segments, to systems of controlling the temperature of bushings having multiple segments, and to other systems and methods. In one embodiment, a method of controlling the temperature of a bushing having multiple segments comprises forming a plurality of filaments from a bushing comprising at least two segments, gathering the filaments into at least two ends, measuring the size of each of the at least two ends, comparing the measured size of the at least two ends to a desired end size, adjusting the amount of current passing through the at least two bushing segments in response to the end size comparisons.

Abstract: Methods for modifying preform core ovality during and subsequent to the formation of an optical fiber preform. After MCVD deposition forms the core rod, but prior to overcladding of the core rod, the code rod may be etched to change its ovality. In order to etch the core rod, the core rod may be mounted to lathe, rotated by at least two rotors, and subjected to a heat source. Additionally, one of the at least two rotors may be phase-shifted from another one of the at least two rotors after the core rod is mounted on the lathe.

Abstract: An optical fiber base material manufacturing method includes: supplying oxygen, hydrogen, and silicide to a core deposition burner; depositing silicon dioxide; adjusting a drawing up speed so that a deposition tip position remains at the same position in accordance with growth of a porous base material; calculating an average of the drawing up speed at each preset time interval; calculating a difference of the calculated average from a preset value of the drawing up speed; correcting a flow rate of silicon tetrachloride when the supplied hydrogen is hydrogen produced or stored at normal temperature, and correcting a flow rate of hydrogen when the supplied hydrogen is hydrogen obtained by vaporizing liquid hydrogen, where when correcting the flow rate of hydrogen, a flow rate of hydrogen supplied to a cladding deposition burner is also corrected in a ratio of before and after the correction of the flow rate of the hydrogen.

Abstract: A method for manufacturing a preform for optical fibers by means of a vapor deposition process, wherein plasma conditions are created and wherein the plasma is moved back and forth along the longitudinal axis of the hollow substrate tube between a reversal point near the supply side and a reversal point near the discharge side of the hollow substrate tube, so that the location where the soot deposition associated with one phase takes place is axially spaced from the location where the soot deposition associated with the other phase(s) takes place.