Abstract: Method of producing glass components and preforms for use in the method. The preform includes a primary rod having a constant outside diameter and a square bottom and a sacrificial tip having a first end attached to the bottom of the primary rod, a second end opposite the first end, and a hollow interior region extending from the first end to the second end. The sacrificial tip is circular in cross section and the first end of the sacrificial tip has an outside diameter equal to the outside diameter of the primary rod. When the preform is heated in a furnace, the sacrificial tip melts and collapses into a drawing bulb which either draws the primary rod directly into the glass fiber or results in a tapered (i.e. tipped) preform for subsequent fiber draw. Material waste as well as the drip time is reduced and the cladding-to-core ratio, crucial for waveguide properties, is maintained for the whole preform compared to a square cut preform without the sacrificial tip.

Abstract: A method of manufacturing a tuned optical fiber includes providing a first preform from a set of like preforms each having substantially the same refractive index profile, including amount of axial variation relative to a target refractive index profile. The method includes drawing a reference optical fiber from the first preform and measuring a variation in an optical or physical property as a function of axial position. The method also includes drawing from a second preform from the set of like preforms the tuned optical fiber. The drawing includes using a time-varying tension that reduces the amount of variation of the optical or physical property of interest. The time-varying tension is defined by an amount of axial stress imparted to the tuned fiber needed to alter the refractive index profile and the at least one optical or physical property based on a stress-optic effect.

Abstract: An optical fiber manufacturing method includes: coating an outer periphery of a bare optical fiber with a resin before curing by a coating device; and curing the resin with a coating curing device. The following equations are satisfied: t×sin ?>T1× tan ? and ?=tan?1 (d/L), where T1 is a tension in the upstream of the coating device, t is the shear force applied to the bare optical fiber by the resin, d is the design maximum value of a deviation amount of an entry position of the bare optical fiber into the resin in the coating device with respect to the center axis of the die hole of the coating device, and L is the contact length between the resin and the bare optical fiber in the coating device along the center axis.

Abstract: A method of manufacturing an optical fiber of the invention includes: preparing a direction changer; drawing the bare optical fiber from an optical fiber preform; providing a coated layer on a periphery of the bare optical fiber; obtaining an optical fiber by curing the coated layer; changing a direction of the bare optical fiber at a position between a bare-optical-fiber formation position and a coated-layer provision position; and measuring the outer diameter of the coated layer; and adjusting the length of the bare optical fiber from a drawing unit to a coating unit by controlling a position of the direction changer based on a measurement value of the outer diameter, the drawing unit forming the bare optical fiber, the coating unit providing the coated layer on the periphery of the bare optical fiber.

Abstract: Provided is a method of processing a glass base material for optical fiber in which the glass base material for optical fiber is elongated to reduce a diameter thereof until reaching a final elongation diameter and form a completed base material. The method includes measuring an outer diameter distribution that includes an outer diameter of the glass base material for optical fiber; setting an effective region; calculating a target elongation diameter that is larger than the final elongation diameter and less than an average diameter of the effective region, and elongating the glass base material for optical fiber until reaching the target elongation diameter; and after reaching the target elongation diameter, further elongating the glass base material for optical fiber until reaching the final elongation diameter.

Abstract: A glass base material elongating method of elongating a glass base material to make a diameter of the glass base material smaller by connecting a pulling dummy at an end of the glass base material and then gripping and pulling the pulling dummy with a pair of rollers that grip or release the pulling dummy is provided. The method includes forming a rough surface part on the pulling dummy before elongating the glass base material. The rough surface part may be formed by grinding the pulling dummy. Also, the rough surface part of the pulling dummy may have a roughness of 5 ?m or more.

Abstract: Embodiments of the invention relate to a gas delivery system. The gas delivery system includes a fast gas exchange module in fluid communication with one or more gas panels and a process chamber. The fast gas exchange module has first and second sets of flow controllers and each of first and second sets of flow controllers has multiple flow controllers. The flow controller is configured such that each of the flow controllers in the first and second sets of the flow controllers is independently operated to selectively open to divert gas to the process chamber or an exhaust. The first and second sets of flow controllers are operated for synchronized switching of gases in a pre-determined timed sequence of flow controller actuation. The invention enables fast switch of resultant gas flow in the process chamber while having individual flow controller operated at lower switching speed to provide longer service life.

Abstract: A mat includes a first principal face, a second principal face opposite to the first principal face, entangled points, and unentangled portions. The entangled points are provided by entangling inorganic fibers with one another. The unentangled portions are provided from the first principal face to the second principal face. The inorganic fibers are not entangled with one another and are arranged substantially parallel to one another in said unentangled portions.

Abstract: To manufacture glass base material with high manufacturing yield, provided is a glass base material elongating method comprising forming a tapered portion where the outer diameter of the glass base material changes continuously, holding the glass base material with chucks, heating the glass base material held by chucks with a heat source, and with a portion of the glass base material softened, increasing the distance between the chucks to elongate the glass base material. The elongation begins from a state in which a position of the heat source at a position at which the outer diameter of the glass base material is set in a range from no less than 95% to no more than 98% of an average outer diameter of the trunk portion of the glass base material.

Abstract: The present invention provides an apparatus and a method for fabricating a glass rod from a glass preform capable of suppressing a diameter fluctuation of the drawn glass rod even when there is a relatively large diameter reduction ratio between the glass preform and the glass rod, such as 60 to 95%. The diameter (D) of the glass preform for determining the ratio from a measured diameter data is acquired from measured diameter data of the glass preform, the measured diameter data is obtained by measuring the diameter of the glass preform along the longitudinal length of the preform before drawing the glass preform, and the feed speed (V1) is determined so that the feed speed (V1) varies depending on fluctuations of the measured diameter data in the longitudinal direction.

Abstract: A method of manufacturing quartz glass includes depositing soot generated by flame hydrolysis of a raw material gas to a starting member, while the starting member is raised and rotated, to form a soot deposition member that includes an effective portion having a substantially constant outer diameter, the effective portion to become a material of a glass product, an upper ineffective portion formed at an upper end of the effective portion, and a lower ineffective portion formed at a lower end of the effective portion, each of the ineffective portions having an outer diameter changing in a tapering form, wherein the depositing includes forming the lower ineffective portion while decreasing a peripheral speed of a surface of the starting member to a predetermined final peripheral speed in a ratio of 1.3 m/minute or below per second during a period after the effective portion is formed.

Abstract: Provided is a method of manufacturing a porous glass deposition body for optical fiber comprising depositing silica powder on a starting member being raised and rotated by using burners with different deposition positions. With a glass raw material flow rate supplied to a core deposition burner represented by F1 and a total flow rate of glass raw material supplied to a cladding deposition burner adjacent to the core deposition burner represented by F2, during an initial deposition stage occurring before gas conditions reach a stable state, glass raw material is supplied to points at the same longitudinal position of the deposition body such that a glass raw material flow rate ratio F2/F1 is no less than 0.69 and no greater than 1.03.

Abstract: In an optical fiber manufacturing method, the cooling device and the coating device are connected in an airtight manner and by preventing a cooling gas, flowing inside the cooling device, from flowing into the coating device by a meniscus of resin inside of the coating device, a flow of the cooling gas inside the cooling device is discharged to an outside of an upper end of the cooling device as an upward stream; helium gas as the cooling gas flows into a lower portion of the cooling device and carbon dioxide gas as the cooling gas which is separated from the helium gas flows into a side lower than a position where the helium gas flows in, during the forcible cooling; and a flow rate of the helium gas and a flow rate of the carbon dioxide gas are individually controlled.

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: 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 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: Method for overcladding an optical fiber preform with a given target diameter (D0) of the final preform includes providing a primary preform to be overcladded, and successively depositing first overcladding layers by projecting and vitrifying silica particles on the primary preform moving in relative translation with a plasma torch. Each first overcladding layer has a given uniform thickness (d) and is deposited at a given, constant silica particle flow rate and at a given, constant translation speed. The method also includes the detection of a preform diameter (D1) greater than a given threshold (S) and the deposition of a final overcladding layer having the remaining required thickness (D0?D1) at a constant silica particle flow rate and at a reduced translation speed. The inventive method enables a preform to be overcladded efficiently with improved yield and high quality.

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 and device for making high precision glass tubes. A glass rod is pushed into a heated chamber and the tube is pulled from the chamber. Preferably, both the push rate and the pull rate are controlled. Fiber optic glass ferrules and other components manufactured by the use of this invention have precision dimensions that fall well within the tight dimensional tolerances required for ferrules and others.

Abstract: The present invention provides an apparatus and a method for fabricating a glass rod capable of suppressing a diameter fluctuation of a drawn glass rod even in a case of a relatively large diameter reduction ratio between a glass preform and a glass rod, such as 60 to 95%. The diameter (D) of the glass preform for determining the ratio from a measured diameter data is acquired, the measured diameter data is obtained by measuring a diameter of the glass preform before being drawn along a longitudinal direction of the preform, and the feed speed (V1) is determined so that the feed speed (V1) varies depending on a fluctuation of the measured diameter data in the longitudinal direction.

Abstract: A manufacturing process of a microstructured optical fiber including a void-containing region, includes the steps of: drawing a microstructured optical fiber along a longitudinal direction from a heated preform, wherein the optical fiber is continuously advanced along the longitudinal direction; directing a radiation beam at a longitudinal position in the longitudinal direction of the optical fiber so as to produce an interference pattern; detecting the interference pattern and producing at least one electrical detection signal corresponding to the interference pattern and including a plurality of signal fringe cycles; feeding the first detection signal into a first counter circuit; determining a first number of interference fringe increments in the plurality of signal wave fringe cycles of the at least one detection signal by using the first counter circuit; determining the outer diameter of the optical fiber, and controlling the microstructure of the optical fiber during advancement of the optical fiber.

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: A manufacturing method of a photonic band gap fiber which includes measuring a hole diameter d0 and a distance-between-holes ?0 in a preliminary experiment capillary body by first drawing a preliminary experiment preform, calculating a confinement loss to a normalized wavelength ?/? being a wavelength ? normalized by an optional distance-between-holes ? using a ratio d0/?0 and the optional distance-between-holes ? as design parameters, setting a distance-between-holes by calculating the set distance-between-holes ?1 to a desired transmission wavelength ?1 of a photonic band gap fiber to be manufactured using a value of the normalized wavelength ?/? in which the confinement loss becomes about a minimum value, and second drawing a preform for a photonic band gap fiber by using the same members as those of the preliminary experiment preform and by setting a distance-between-holes to the set distance-between-holes ?1, in a drawing temperature condition used for the first drawing.

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: To provide a elongating method for elongating an optical fiber parent material with high reliability by implementing a high precision control for the outer diameter in short time. This elongating method includes a process for switching a control method for at least one of the control items of measurement object, based on at least one of a difference between measured value and target value and a change rate of the difference per unit time, in measuring the outer diameter of a glass parent material elongating portion and making a feedback control for the elongating conditions based on the difference from the target outer diameter.

Abstract: A method and device for making high precision glass tubes. A glass rod is pushed into a heated chamber and the tube is pulled from the chamber. Preferably, both the push rate and the pull rate are controlled. Fiber optic glass ferrules and other components manufactured by the use of this invention have precision dimensions that fall well within the tight dimensional tolerances required for ferrules and others.

Abstract: An object of the present invention is to provide a method for manufacturing a glass particle deposited body in which a taper portion formed at an end portion of the glass particle deposited body is reduced without increasing the number of burners.

Abstract: In a known method for the production of a blank mold for optical fibers, a fluorine-doped SiO2 enveloping glass is produced on a core glass cylinder that rotates about its longitudinal axis, wherein a silicon-containing starting substance is fed to a plasma burner, said substance is then oxidized in a plasma flame assigned to the plasma burner to obtain SiO2 particles, the SiO2 particles are deposited by layers on the enveloping surface of the cylinder of the core glass cylinder in the presence of fluorine and sintered into the enveloping glass. The invention aims at providing an economical method, which builds upon the above-mentioned method, in order to produce a blank mold from which optical multi-mode fibers (52) can be obtained.

Abstract: A glass base material, which is a base material of an optical fiber, comprising: a core; and a clad surrounding the core; wherein: a rate of change in a relative-refractive-index-difference between the core and the clad in a longitudinal direction of the glass base material is substantially 6% or less.

Abstract: Methods for substantially improving the stability of a melting furnace system including bushings and cooling apparatus for converting molten mineral material to continuous fibers is disclosed. Apparatus and methods for maintaining the molten material throughput and the electrical power load on fiberizing bushings substantially constant are disclosed. The orifice plate, with or without tips or nozzles, is subjected to a more rapid rate of heat removal after the bushing breaks out than it did while the bushing was in a desired fiberizing mode. Apparatus for blowing cooling air upward onto the orifice plate during the time the bushing is breaking out and/or hanging to provide additional cooling is disclosed along with optional additional or alternative apparatus to use for optional additional or alternative cooling is also disclosed.

Abstract: A method of manufacturing an elongated glass body by elongating a glass body of columnar or cylindrical shape. The method comprises: (1) a first elongating step for obtaining an intermediate elongated body, where the glass body is softened by heating and elongated, while the diameter of the softened part is measured, so that the measured value may become equal to a first controlled diameter which is larger than the target diameter, where the diameter of the intermediate elongated body satisfies the relationship at each position thereof: (the target diameter?10 ?m)<(the diameter of the intermediate elongated body)<(the target diameter+500 ?m); and (2) a second elongating step for obtaining an elongated glass body having the target diameter, where the intermediate elongated body is softened by heating and elongated.

Abstract: A planar laser gain medium and laser system. The novel laser gain medium includes an active core having a high aspect ratio cross-section with a fast-axis dimension and a slow-axis dimension, signal claddings adapted to form reflective boundaries at fast-axis boundaries of the core, and a material adapted to minimize reflections at slow-axis boundaries of the core. In an illustrative embodiment, the laser gain medium is an optical fiber. The core and claddings form a waveguide adapted to control modes propagating in the fast-axis direction. When the laser gain medium is employed as a laser oscillator, a high reflectivity mirror and an outcoupler are positioned at opposite ends of the core to form a laser resonator adapted to control modes in the slow-axis direction.

Abstract: A glass concentrator for manufacture of solar energy conversion module is provided including a webbing that has a load sustenance characteristic and a hail impact resistance characteristic based on a first thickness of the webbing. The concentrator also includes a plurality of elongated concentrating elements integrally formed with the webbing. Each of the elongated concentrating elements has an aperture region, an exit region and two side regions, which bears a geometric concentration characteristic provided by a highly reflective side regions and an aperture-to-exit scale ratio in a range from about 1.8 to about 4.5. The glass concentrator can be attached with a plurality of photovoltaic strips cumulatively on each and every exit regions and clamped with a rigid or flexible back cover member to form a solar concentrator module for converting sunlight to electric energy. The solar concentrator module based on certain embodiments meets the industrial qualification standards.

Abstract: A method of elongating a glass body is provided, in which method the axial variation in the inner refractive index structure of a glass body can be restrained.

Abstract: A glass body with at least one curve is formed from a glass blank in bar form in a bending device for bending the glass blanks. The bending device has grippers which are movable in relation to one another. The glass blank is taken up by the grippers and clamped. Subsequently, the bending region between the grippers is heated up to a bending temperature by heating means. After that, the grippers are moved in a predetermined way, the bending region being freely bent. The advantageous effects of the invention are seen as being that any desired curves can be produced on glass blanks without requiring moulds that rely on pressing or contact. The free bending takes place without touching the surface in the heated-up bending region, so that instances of damage to the surface are avoided. This allows curved glass bodies with good optical properties to be produced.

Abstract: A process and apparatus for elongating an optical fibre preform includes heating the preform so as to soften one region thereof; elongating the preform by submitting the preform to a traction; determining, during the step of elongating, the preform diameter in at least one measuring point along the preform; and controlling the step of elongating on the basis of the determined diameter. During the step of elongating, at least a geometrical parameter of the preform is measured, and the position of said diameter measuring point is controlled according to the measured geometrical parameter. Measuring at least a geometrical parameter of the preform may be accomplished by determining the profile of at least a portion of the softened region, e.g., an image of the neck region profile.

Abstract: There is provided robust diameter-controlled optical fiber during optical fiber drawing process and an optical fiber drawing process which comprises drawing the optical fiber from a perform therefor under tension to form the optical fiber while heating and melting the preform, wherein an outer diameter of the preform is measured (at a safe position immediately) above the furnace, an outer diameter of the optical fiber on which no coating has been provided is measured at one process position or two process positions before coating, and drawing conditions are robustly controlled based on the deviation of the measured optical fiber diameter data and the measured preform diameter data from a preselected outer diameter of the optical fiber and a preselected outer diameter of the preform.

Abstract: An apparatus for fabricating a soot preform for an optical fiber. The soot preform is fabricated by depositing glass particles on a starting rod capable of being rotated and pulled up. The apparatus comprises elements as follows. A reaction chamber is used for depositing the glass particles on the starting rod. An upper room is located above the reaction chamber for receiving the soot preform formed in the upper portion of the reaction chamber. At least one core burner is installed in the reaction chamber. A gas-supplying inlet is located in the top part of the sidewall of the reaction chamber closest to burner(s), and a gas-exhausting outlet is located in the top part of another sidewall opposite to the gas-supplying inlet. In addition, at least one cladding burner is installed in the reaction chamber.

Abstract: A method for manufacturing an optical fiber preform that can produce an optical fiber having desired characteristics over the longer length thereof. A crude preform provided with a core region and a cladding region is prepared (Step S1), and at a plurality of positions in the longitudinal direction of the crude preform, a refractive index profile in the cross-section of the crude preform is measured (Step S2). Then, the shape of the cladding region is demarcated based on the shape of the profile (Step S3). Subsequently, the crude preform is ground based on the results of the demarcation (Step S4). Thus, an optical fiber preform that enables the manufacture of an optical fiber having target characteristics is manufactured.

Abstract: Based on an intermediate 20A in which a cladding portion 22 is formed on the outer periphery of a core portion 21, a pair of holes 23 and 24 are provided parallel to the z axis on both sides of the core portion 21 within the cladding portion 22, and an intermediate 20 is thereby fabricated. In this intermediate 20, a width Ry in the y-axis direction is made smaller than a width Rx in the x-axis direction. Moreover, a cylindrical stress applying part 33 is inserted into a hole 23 of the intermediate 20, and a cylindrical stress applying part 34 is inserted into a hole 24 thereof. Thus, a preform 40 is formed. These materials are drawn and integrated together, and a polarization maintaining optical fiber is thereby manufactured.

Abstract: An apparatus for manufacturing a glass-base-material, which is a base material of an optical fiber, includes a driving unit that drives a glass rod around an axis of the glass rod; a burner for accumulating glass soot around outside surface of the glass rod, which is driven by the driving unit, to form the glass-base-material; a weight-deducting unit, on which the driving unit is mounted, for deducting a predetermined weight from a total weight of the driving unit and the glass-base-material formed by the burner; and a measuring unit provided under the weight-deducting unit for measuring the total weight, from which the predetermined weight is deducted by the weight-deducting unit.

Abstract: An apparatus for manufacturing a glass-base-material, which is a base material of an optical fiber, includes a driving unit that drives a glass rod around an axis of the glass rod; a burner for accumulating glass soot around outside surface of the glass rod, which is driven by the driving unit, to form the glass-base-material; a weight-deducting unit, on which the driving unit is mounted, for deducting a predetermined weight from a total weight of the driving unit and the glass-base-material formed by the burner; and a measuring unit provided under the weight-deducting unit for measuring the total weight, from which the predetermined weight is deducted by the weight-deducting unit.

Abstract: According to a prior art method for producing a cylindrical component comprised of silica glass, a cylinder comprised of a softened silica glass mass is drawn in a predetermined drawing direction along a drawing axis by means of a drawing device which acts upon said cylinder. The aim of the invention is to provide a method which prevents, to the greatest possible extent, warping of the drawn cylinder and other deviations from the ideal cylinder dimensions and to prevent, to the greatest possible extent, the outer surface of the drawn cylinder from being touched. To these ends, the invention provides that the drawing device comprises a plurality of guide elements which are arranged one behind the other along the drawing axis, and which can be displaced independently of one another in a drawing direction and in a direction opposite thereto.

Abstract: The method of manufacturing an optical fiber in accordance with the present invention comprises a step of yielding an optical fiber by drawing an optical fiber preform softened upon heating, wherein a temperature at which the optical fiber preform is softened is at least 1800° C., whereas the optical fiber preform or optical fiber has a glass cooling rate of 4000° C./sec or less when attaining a temperature of 1800° C.

Abstract: Methods and apparatuses estimate and control optical fiber primary coating diameter for wet-on-wet optical fiber manufacturing. The primary coating diameter for a particular length of optical fiber is calculated based upon a measurement of the weight of primary and/or secondary coating material consumed during optical fiber manufacturing. Control of the primary coating diameter is effected by a coating controller which can increase or decrease the primary coating diameter through control of glass temperature, coating viscosity and/or other parameters during wet-on-wet fiber manufacture.

Abstract: The specification describes a VAD method for dynamically controlling the growth rate of both the core soot and the cladding soot in response to separate growth monitors.

Abstract: The invention relates to a method of fabricating an optical fiber with improved control of transmission characteristics. It proposes determining variations in the characteristics of the preform departing from the design characteristics and modifying the diameter of the fiber during drawing as a function of the measured variations. By varying the diameter of the fiber, variations in the preform departing from its design values can be compensated, in other words irregularities of the preform can be smoothed out. This variation limits the effect of preform variations on the propagation characteristics of the fiber.

Abstract: The drawing method of the present invention uses a drawing furnace comprising a furnace muffle tube, a furnace body and a heater. According to the method, an optical fiber preform is inserted from the inlet of the furnace muffle tube, the optical fiber preform is melted by means of a heater, under a specified gas atmosphere, and is drawn toward the outlet of the furnace muffle tube by means of a specified drawing tension. The optical fiber preform and the drawing furnace used in this method both satisfy the condition of below-indicated formula (1): L/D?8??(1) wherein L indicates the length of the furnace body in the drawing direction and D indicates the diameter of the optical fiber preform.

Abstract: A method for producing an optical fiber preform is provided in which the variation of the outer diameter in the longitudinal direction is minimized and a target quantity of glass is accumulated as a whole. Based on a predetermined relationship between three variables: the outer diameter of a starting rod being a first variable, the outer diameter of an optical fiber preform a second variable, and the timing for ending the glass particles depositing process a third variable, the starting rod and burners are subjected to relative reciprocating movement so as to deposit glass particles on the starting rod until the timing for ending the depositing process, and then the resulting deposit body is vitrified. The third variable may be the traverse velocity, the glass particles deposition time, or the weight of a soot glass deposit body.