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

Abstract: A method of making an optical fibre including providing an increased diameter portion on a rod. The rod is assembled by positioning the rod in a tube such that an annular gap is defined between an outer surface of the rod and an inner surface of the tube, and such that the increased diameter portion of the rod engages the tube and supports the rod with respect to the tube, and supporting the rod and tube assembly by gripping the tube. At the lower end of the rod and tube assembly, portions of the tube are collapsed onto the rod such that the tube portions fuse to the rod forming collapsed portions of the rod and the tube assembly. The collapsed portions are drawn to form an optical fibre. The vertically oriented rod and tube assembly can also be collapsed to form an optical fibre preform.

Abstract: Methods for making a preform for a large diameter optical waveguide such as a cane waveguide are disclosed. The method includes inserting a preform into a glass tube to serve as cladding that provides a thickened preform, simultaneously fusing and stretching the thickened preform, sectioning the stretched and still thickened preform and repeating the procedure if necessary to provide an even further thickened preform. The drawing apparatus can be configured to work with the preform disposed either horizontally or vertically and usually includes a graphite resistance furnace. Typically, the drawing apparatus is an upper portion of a draw tower used for drawing an optical fiber from an optical fiber preform. The draw tower includes a tractor pulling mechanism that can adjust to grip a wide range of diameters.

Abstract: Disclosed is an optical fiber article for receiving pump radiation of a first wavelength for amplifying or generating radiation of a second wavelength. The optical fiber article includes a core for propagating light of the second wavelength. The core has a first index of refraction and includes a rare earth material. A cladding surrounds the core and has a second index of refraction that is less than the first index of refraction. The outer circumference of the cladding can include a plurality of sections, where the plurality of sections includes at least one substantially straight section and one inwardly curved section. The optical fiber article can also include at least one outer layer surrounding the cladding, where the index of refraction of the outer layer is less than the second refractive index. Methods for producing the optical fiber article are also disclosed, as well as methods for providing a preform for drawing such an optical fiber article.

Abstract: A glass composition for a seal consists essentially of 70-75 wt % of PbO, 3-7 wt % of PbF2, 5-8 wt % of Bi2O3, 5-7 wt % of B203, 2-5 wt % of ZnO, 1-3 wt % of Fe2O3, 0-2 wt % of CuO, 0-2% of TeO2, and a trace <0.2% of MnO2, the composition having a flow temperature of <350° C. Such seals can be flowed at low temperatures, using different and less environmentally damaging constituents to those used before. Damage to temperature sensitive materials near the seals, can be reduced. Low flow temperatures can be achieved without excessive degradation of properties such as low viscosity, low expansion coefficient, good adhesion to glass and metals, low permeability of air, good long term hydrolytic stability. A filler such as a ceramic powder, is added to match the temperature expansion coefficient to the materials being sealed. It can be used to fix silica fiber into electro-optic devices to achieve hermetic joints with high mechanical stability.

Abstract: Embodiments of the invention include a method for making optical fiber having reduced aging or hydrogen aging loss over the life of the fiber and optical fiber systems including such optical fibers. The method includes the steps of dehydrating an optical fiber glass core rod in a first environment including oxygen and at least one of chlorine-containing gases, fluorine-containing gases and carbon monoxide; and adjusting the oxygen stoichiometry of the first environment so that it is neither oxygen-rich nor oxygen-deficient. Improved silicon-oxygen stoichiometry during one or more preform manufacturing steps reduces the amount of Si defects generated in the optical fiber preform. Also, deuterium exposure of optical fiber drawn from the preform reduces the likelihood of having atomic defects such as Si defects in the optical fiber that, over time, attract and bond with hydrogen atoms to form molecules that contribute to increased water absorption loss.

Abstract: A method of producing with the collapsing process an optical fiber preform capable of forming an optical fiber in which an increment in transmission loss due to OH absorption is reduced, and an optical fiber preform and an optical fiber produced with the method. The method comprises reducing the amount of hydrogen atom-containing substances in a glass pipe, sealing one end of the glass pipe, and collapsing the glass pipe to obtain a solid body. One aspect of the method comprises heating the glass pipe at 550° C. or below, sealing one end of the glass pipe, and collapsing the glass pipe to obtain a solid body. The preform produced with the method has a feature in that its portion formed by the interface portion at the time of the collapsing contains OH groups at a concentration of 100 wt. ppb or below. The optical fiber produced by drawing the preform has a feature in that its OH-originated loss is less than 0.5 dB/km at a wavelength of 1.38 &mgr;m.

Abstract: A method of forming an optical fiber by heat treating a consolidated glass article, doped with at least one refractive index-modifying dopant, at a temperature between about 1100° C. and 1400° C. and for a time between about 1 hour and 12 hours in a helium-containing atmosphere. The consolidated glass article is an optical fiber precursor. The optical fiber drawn from the heat treated consolidated glass article exhibits an attenuation lower than an optical fiber drawn from a substantially identical optical fiber precursor that has not been heat treated in accordance with the present invention.

Abstract: An optical fiber preform includes a core rod and an overclad tube having an open, distal end dimensioned to enter the mouth of a vertical fiber draw furnace. A plug is fixed in the region of the distal end of the tube, and the core rod is disposed axially inside the overclad tube so that a distal end of the rod is restrained from downward movement by the plug as the tube enters and descends into a hot zone of the draw furnace. The distal end of the tube is heated in the furnace hot zone until the tube and the plug soften and fuse with one another. The tube then collapses onto the core rod to produce a drop from which an optical fiber having desired properties may be drawn.

Abstract: A process produces a glass overcladding tube from a silica gel body. The process includes passing the gel body through a hot zone under conditions that cause partial sintering of the gel body and repassing the gel body through the hot zone under conditions that further sinter the gel body into a glass overcladding tube.

Abstract: The present invention provides a method of preparing preforms for optical fibers. The invention allows one to remove or significantly reduce undesirable refractive index variations in the central portion of the optical fibers. The method of preparing the preform having a central duct includes the steps of a first collapsing step, an etching step and a second collapsing step. The first collapsing step reduces the size of the central duct without closing the central duct by heating the preform at a first preform collapsing temperature. A portion of the last deposited layer of the core glass layers is etched by flowing an etchant gas through the central duct at a lower temperature than the preform collapsing temperature. The preform is finally collapsed at a second collapsing temperature to close the central duct of the preform and form a solid rod.

Abstract: Apparatus and methods are provided for reducing end effect on a preform assembly during manufacture of optical fiber. The present invention provides apparatus and methods that apply a first vacuum pressure to a preform assembly during a first portion of the draw of optical fiber from the preform assembly and a second lesser vacuum pressure during a second portion of the draw. The second vacuum pressure may be a step down pressure or a gradual or an incremental decrease in pressure over time. The present invention further provides apparatus and methods that use an intermediate rod such as a dummy preform core rod and/or a support rod placed at the back of the preform core rod, wherein the preform end effect occurs on the dummy preform core rod, as opposed to the core rod of the preform assembly or is eliminated altogether by the support rod.

Abstract: The present invention provides a method for making a multicore large diameter optical waveguide having a cross-section of at least about 0.3 millimeters, two or more inner cores, a cladding surrounding the two or more inner cores, and one or more side holes for reducing the bulk modulus of compressibility and maintaining the anti-buckling strength of the large diameter optical waveguide. The method features the steps of: assembling a preform for drawing a multicore large diameter optical waveguide having a cross-section of at least about 0.3 millimeters, by providing an outer tube having a cross-section of at least about 0.3 millimeters and arranging two or more preform elements in relation to the outer tube; heating the preform; and drawing the large diameter optical waveguide from the heated preform. In one embodiment, the method also includes the step of arranging at least one inner tube inside the outer tube.

Abstract: Methods, systems, and apparatus consistent with the present invention use a beam of laser energy to concentrically form an optical preform from two or more concentric glass objects, such as two glass tubes or a hollow glass tube and a solid glass rod. The glass objects are placed in a concentric configuration where the outer object has an inner surface that is placed proximate to an outer surface of the inner object. Once these are assembled, a beam of laser energy is generated, positioned, and applied to a starting point in the gap defined by the inner surface and the outer surface. Once the laser beam is applied and is reflecting down into the gap, the beam of laser energy is moved relative to the starting point as the beam is concurrently applied. This heats the inner surface and outer surface so that the two objects can be joined to form the optical preform. In another aspect of the invention, a coating layer is disposed within the gap and can be heated by the laser as it is applied within the gap.

Abstract: Embodiments of the invention include a method and apparatus for making optical fiber preforms and optical fiber. The method includes the steps of positioning an overclad tube around a preform core rod, heating the overclad tube along the length thereof in the presence of a pressure gradient to collapse onto the preform core to form the overclad optical fiber preform, and adjusting the radial size of a heated portion of the preform core rod and/or the overclad tube to actively match the radial dimensions of the preform core rod along the length thereof with corresponding portions of the overclad tube. The active matching reduces variations in the physical dimensions of the preform core rod and/or the overclad tube, which improves transmission and other performance characteristics of fiber drawn from the created preform, e.g., by maintaining a relatively constant D/d ratio of the preform.

Abstract: A method for making a glass ceramic, optoelectronic material such as a clad optical fiber or other component for use in an optoelectronic device. The method comprises preparing a glass composition batch to yield a precursor glass for a nanocrystalline glass-ceramic that is doped with at least one kind of optically active ion, such as a transition metal or lanthanide element; melting the batch; forming a glass cane; surrounding the cane with a chemically inert cladding material shaped in the form of a tube; drawing a glass fiber from the combined precursor-glass “cane-in-tube” at a temperature slightly above the liquidus of the precursor glass composition, and heat treating at least a portion of the drawn clad glass fiber under conditions to develop nanocrystals within the core composition and thereby forming a glass ceramic.

Abstract: Techniques are described for fabricating a preform from a soot body. In one described technique, a soot body is loaded into a substrate tube, and the position of the soot body is stabilized within the tube. The tube is then rotated around its longitudinal axis. Heat is applied from a heat source to the substrate tube at a first end of the soot body to cause the first end of the soot body to begin to sinter and to cause the substrate tube to begin to at least partially collapse around the sintered portion of the soot body. The heat source is then advanced along the substrate tube and the soot body to cause a progressive sintering of the soot body, and to cause a progressive, at least partial, collapse of the substrate tube around the sintered portion of the soot body.

Abstract: A method of manufacturing a cane suitable for forming an optical fiber, and a method of forming an optical fiber from the cane. A core composition having about 20% to 30% by weight of P2O5 is formed. An inner cladding composition is formed on an outer surface of the core composition and the core composition and the inner cladding composition are consolidated into a preform having a core and an inner cladding while substantially closing a center line hole of the preform. An outer cladding composition is formed on the preform to define a cane. The cane can then be transformed into an optical fiber.

Abstract: The invention provides a monomode optical fiber and a monomode preform (2) having a mother preform (22) housed in an outer sleeve tube (20). It is characterized in that it also includes an intermediate tube (21) between the mother preform (22) and the outer tube (20), the intermediate tube (21) possessing viscosity at fiber-drawing temperature which is less than the viscosity(ies) at fiber-drawing temperature of the mother preform (22) and of the outer tube (20). The invention also provides a method of manufacturing a monomode optical fiber. The fiber has a core that is better centered and less deformed than in the prior art. An application of the invention lies in making an optical amplifier.

Abstract: In a glass preform (10) to be subjected to fiber-drawing, use is made of a cylindrical glass tube (21) whose one end in an axial direction is sealed. A plurality of glass capillaries (22) extend in the glass tube in the axial direction. The glass capillaries are fused to one another into an integral structure. The glass capillaries have air holes periodically arranged on a plane perpendicular to the axial direction, respectively.

Abstract: Methods of bonding glass articles that are subsequently drawn into sheets, rods, fibers, etc. are disclosed. Bonding is achieved without use of adhesives or high temperature fusion. The invention is particularly useful for bonding optical fiber preforms prior to drawing of the optical fiber.

Abstract: An optical fiber preform having a low core noncircularity and eccentricity for producing an optical fiber having an improved polarization mode dispersion, a method for producing the preform, and an optical fiber produced from the preform. The optical fiber preform is produced by the following steps. Diameter-reduced portions 11a and 11b are formed in the vicinity of the ends of the glass pipe 11. A glass rod 12 is inserted into the glass pipe 11. The glass rod 12 is fixed to the glass pipe 11 at the diameter-reduced portion 11a. The glass pipe 11 and the glass rod 12 are heat-unified from the diameter-reduced portion 11b forward to the diameter-reduced portion 11a. The optical fiber preform has a core noncircularity of at most 1.5%. The optical fiber has a polarization mode dispersion of at most 0.15 ps/km1/2 at a wavelength of 1,550 nm.

Abstract: In a known procedure for the manufacture of an optical fiber by drawing from a preform with a core-clad structure or from a coaxial arrangement of several components forming a core-clad structure, a core cylinder is produced with a soot deposition method, with the core cylinder having a core glass layer of a higher refractive index, “nK”, and outer diameter, “dK”, said core glass layer being encased by a first cladding glass layer having a lower refractive index, “nM1”, and outer diameter, “dM1”, followed by applying a second cladding glass layer onto the core cylinder. The modification of this procedure according to the invention is characterized by its lower optical fiber production costs. This is achieved by providing the second cladding glass layer (4) in the form of a cladding tube manufactured in a separate step of the procedure, said cladding tube having a mean OH concentration of max. 1 wt.

Abstract: A method for fabricating gradient-index rods and rod arrays. A central rod of optical glass having predetermined properties and predetermined outside dimensions is placed inside a tube of optical glass having predetermined properties and predetermined outside dimensions, to form an assembly. The inside dimensions of the tube are substantially equal to the outside dimensions of the rod. The tube is formed of a plurality of coaxial sleeves, the outside dimensions of each interior sleeve being substantially equal to the inside dimensions of the next adjacent sleeve, each sleeve having a selected refractive index so that, together with the tube, the refractive indices from the central rod through the outermost sleeve approximate the refractive index profile of the gradient-index rod to be fabricated. The central rod and sleeve material is selected so that their respective thermal indices of expansion are substantially equal.

Abstract: In a method for manufacturing an optical fiber having a core portion for waveguiding lights, and a plurality of holes arranged around the core portion, the optical fiber is manufactured by puncturing the holes in a glass rod that is to become the optical fiber, by using an ultrasonic drill, and then drawing the glass rod with the holes to form the optical fiber.

Abstract: Optical fibers are produced by means of a direct sleeving technique that allows the sintering and collapsing of the outer jacket tube onto the inner core rod to be achieved directly during the drawing phase of optical fiber manufacture. In the course of the optical fiber manufacturing process, either a mechanical guide holding a sleeving tube concentrically around an annular gap and core rod or a preform having an enclosed annular gap/cavity are mounted in a drawing tower. A vacuum may be maintained in the annular gap/cavity of this assembly. A heat source is then applied to one end of the preform/assembly such that the extreme end of the tube is collapsed onto the core as fiber is drawn in a controlled manner. This single-step process allows to speed up the sleeving process, without introducing possible asymetries in the final preform and in the fibers drawn therefrom.

Abstract: A method for manufacturing optical fiber preform and fiber. According to the method, a core cane segment is formed with a refractive index delta preferably between 0.2% and 3% that is most preferably formed by an OVD method. A sleeve is formed including at least one down-doped moat preferably having a refractive index delta between −0.1% and −1.2% and at least one up-doped ring preferably having a refractive index delta between 0.1% and 1.2%. The sleeve is formed by introducing glass precursor and dopant compounds into a cavity of a preferably silica glass tube (e.g., one of an MCVD and PCVD method). The core cane segment is inserted into the sleeve and the sleeve is collapsed onto the core cane segment to form a core-sleeve assembly. The core-sleeve assembly is again drawn into a cane and additional cladding is preferably formed thereon. Optical fiber may be drawn from the preform in a conventional draw apparatus.

Abstract: A silica-based core rod is traversed by a heat source along its longitudinal axis, to provide heated, softened regions. During the traverse, compressive or tensile movements are provided along the rod's longitudinal axis, these movements inducing, respectively, increases or decreases in the core diameter at the softened regions. By providing selective core diameter increases and/or decreases across the entire length of the core rod, a desired core diameter profile is attained. It is possible to attain a substantially uniform core diameter, or a varying core diameter profile that provides particular properties, such as systematically varying dispersion. In addition, due to the ability to increase core diameter and core rod diameter in a controlled manner, it is possible to make larger core rods, and in turn larger fiber preforms, than presently possible.

Abstract: An optical fiber preform is a material used for fabricating optical fibers. The optical fiber preform has a target rod which will be the core for optical fibers and a glass layer formed around the outside thereof. A mass W (kg) of the optical fiber preform and a diameter D (cm) of the target rod satisfy a relational expression 0.4·(W)1/2<D. Satisfying this relational expression can prevent the optical fiber preform from being deformed and to have uneven diameters due to the weight thereof in the dehydrating and consolidating process in fabricating the optical fiber preform, even though it is a large-sized optical fiber preform having a diameter of 10 cm or more.

Abstract: There is provided a dispersion-managed fiber preform and a fabricating method thereof preform by modified chemical vapor deposition (MCVD). A core and a clad having the refractive index distribution of an optical fiber with a positive dispersion value are uniformly deposited in a glass tube. The preform with the positive dispersion value is heated at every predetermined period with a torch and the heated preform portions are etched to have a negative dispersion value. Then, the preform alternately having positions with the positive dispersion value and positions with the negative dispersion value along the length direction is collapsed.

Abstract: Disclosed is an apparatus for fabricating an optical fiber, which comprises a furnace for melting a sealed preform assembly to draw an uncoated optical fiber, a coater for coating the uncoated optical fiber, a capstan for drawing the optical fiber from the optical fiber preform by applying a drawing force, an adjoiner for holding a primary optical fiber preform inserted centrally into an overcladding tube with an equidistant space between the outer surface of the primary optical fiber preform and the inner surface of the overcladding tube, and a preform positioner for supporting the sealed preform assembly in a specified position with respect to the furnace.

Abstract: Embodiments of the invention include a method for making optical fiber having reduced aging or hydrogen aging loss over the life of the fiber and optical fiber systems including such optical fibers. Improved silicon-oxygen stoichiometry during one or more preform manufacturing steps reduces the amount of Si defects generated in the optical fiber preform. Also, deuterium exposure of optical fiber drawn from the preform reduces the likelihood of having atomic defects such as Si defects in the optical fiber that, over time, attract and bond with hydrogen atoms to form molecules that contribute to increased water absorption loss. The inventive method produces optical fibers with improved transmission characteristics, e.g., optical fibers made by methods according to embodiments of the invention have transmission loss at 1385 nanometers that is less than 0.33 dB/km and the aging loss increase thereafter is less than 0.04 dB/km.

Abstract: A method for manufacturing optical fiber preform and fiber. According to the method, a core cane segment is formed with a refractive index delta preferably between 0.2% and 3% that is most preferably formed by an OVD method. A sleeve is formed including at least one down-doped moat preferably having a refractive index delta between −0.1% and −1.2% and at least one up-doped ring preferably having a refractive index delta between 0.1% and 1.2%. The sleeve is formed by introducing glass precursor and dopant compounds into a cavity of a preferably silica glass tube (e.g., one of an MCVD and PCVD method). The core cane segment is inserted into the sleeve and the sleeve is collapsed onto the core cane segment to form a core-sleeve assembly. The core-sleeve assembly is again drawn into a cane and additional cladding is preferably formed thereon. Optical fiber may be drawn from the preform in a conventional draw apparatus.

Abstract: A method for welding a dummy tube to a quartz glass tube for use as an optical fiber preform, comprising chamfering the inner edge portion of the dummy tube and/or the quartz glass tube for use as the optical fiber preform before welding the quartz glass tube for use as the optical fiber preform with the dummy tube, and then melt welding them together.

Abstract: A tube-shaped, GeO2-doped silica glass pipe having a high refractive index is prepared (step S2), a cylindrical silica glass rod doped with F element is inserted inside the GeO2-doped silica glass pipe (step S3), and the GeO2-doped silica glass pipe and silica glass rod in thus inserted state are heated so as to be unified (step S4). Further, thus formed assembly is inserted inside the a pure silica glass pipe (step S5), and they are heated so as to be unified (step S6), whereby an optical fiber preform is manufactured.

Abstract: Embodiments of the invention include a method and apparatus for making a multiple overclad optical fiber preform. The method includes positioning a first overclad tube around a preform core rod, positioning at least one second overclad tube around the first overclad tube, and collectively heating the preform core and the overclad tubes under pressure to collapse the overclad tubes onto the preform core rod thus producing a multiple overclad optical fiber preform. The apparatus includes a preform core rod, a first overclad tube surrounding the preform core rod, and at least one second overclad tube surrounding the first overclad tube. A quartz disc with or without one or more quartz spacers is used for supporting the preform core rod and the first overclad tube within the additional overclad tubes.

Abstract: Disclosed is a method of making an optical fiber preform having at least one annular region of depressed refractive index. A tube of silica doped with fluorine and/or boron is overclad with silica soot. A core rod is inserted into the overclad tube and the resultant assembly is heated while chlorine flows between the tube and the core rod to clean the adjacent surfaces. When the soot sinters, the tube collapses onto and fuses to the rod. The resultant tubular structure is formed into an optical fiber which exhibits low attenuation as a result of the low seed count at the interface between the inner core and the region that is doped with fluorine and/or boron.

Abstract: A tube-shaped, GeO2-doped silica glass pipe having a high refractive index is prepared (step S2), a cylindrical silica glass rod doped with F element is inserted inside the GeO2-doped silica glass pipe (step S3), and the GeO2-doped silica glass pipe and silica glass rod in thus inserted state are heated so as to be unified (step S4). Further, thus formed assembly is inserted inside the a pure silica glass pipe (step S5), and they are heated so as to be unified (step S6), whereby an optical fiber preform is manufactured.

Abstract: An improved technique for assembling and drawing fiber from preforms is provided. In one embodiment, the technique involves providing a core rod assembly comprising a core rod and a bushing attached at an end of the assembly. The core rod assembly is inserted into an unsintered overcladding tube, and secured to the tube such that the core rod assembly is suspended within. The overcladding tube and the core rod assembly are heated to sinter the overcladding tube and thereby form a preform assembly. During the heating step, the bushing comes into contact with the interior of the overcladding tube, and, because the bushing has a larger diameter than the core rod, an annular gap is maintained between the core rod assembly and the interior of the overcladding tube. It is then possible to attach a draw handle to the preform assembly, place the preform assembly into a draw tower, and draw fiber from the preform assembly by an overclad during draw technique.

Abstract: An optical fiber having optical characteristics that systematically vary along its length is made by inserting a plurality of cylindrical tablets into a cladding glass tube and overcladding the tube with particles of cladding glass. Each tablet contains a core region, and it optionally contains a layer of cladding glass Adjacent tablets are capable of forming optical fiber sections having different optical properties. Prior to consolidating the glass particles, chlorine flows through the tube and over the tablets. When the tube begins to sinter, the chlorine flow is stopped and the sintering particles generate an inwardly directed force that causes the tube to collapse inwardly onto the tablets which concurrently become fused to each other. The resultant draw blank can be drawn into a low loss optical fiber. This method is particularly useful for making dispersion managed single-mode optical fibers.

Abstract: Embodiments of the invention include a method and apparatus for making optical fiber preforms and optical fiber. The method includes the steps of positioning an overclad tube around a preform core rod, heating the overclad tube along the length thereof in the presence of a pressure gradient to collapse onto the preform core to form the overclad optical fiber preform, and adjusting the radial size of a heated portion of the preform core rod and/or the overclad tube to actively match the radial dimensions of the preform core rod along the length thereof with corresponding portions of the overclad tube. The active matching reduces variations in the physical dimensions of the preform core rod and/or the overclad tube, which improves transmission and other performance characteristics of fiber drawn from the created preform, e.g., by maintaining a relatively constant D/d ratio of the preform.

Abstract: A method for producing an optical fiber preform comprising inserting a core glass rod for use in the optical fiber preform into the quartz glass tube for the optical fiber preform and then welding them in a heating furnace to melt weld them together into a monolithic product, wherein the melting is started in such a state that the lower open edge of said quartz glass tube is placed inside the heating furnace and a gas is supplied from the upper edge of the tube, and after the lower edge portion of the quartz glass tube is drawn out from said heating furnace by melt deformation and stretching by the gravitational force, the gas supply is cut off and the pressure is reduced.

Abstract: Disclosed is a method of making an optical fiber preform having at least one annular region of depressed refractive index. A tube of silica doped with fluorine and/or boron is overclad with silica soot. A core rod is inserted into the overclad tube and the resultant assembly is heated while chlorine flows between the tube and the core rod to clean the adjacent surfaces. When the soot sinters, the tube collapses onto and fuses to the rod. The resultant tubular structure is formed into an optical fiber which exhibits low attenuation as a result of the low seed count at the interface between the inner core and the region that is doped with florine and/or boron.

Abstract: Disclosed are an optical fiber perform manufacturing apparatus and method in which processes for shrinking and closing a deposited tube are conducted using a device suitable for those processes, which device is other than the device used in a deposition process for forming the deposited tube on the inner surface of a perform tube, thereby reducing the processing time while reducing the amount of OH penetrated from the perform tube into a vitreous component of the deposited tube, thereby achieving a reduction in OH loss.

Abstract: Fused silica created by pyrolysis of SiCl4 are introduced in a powder state into a vacuum chamber. Pluralities of jet streams of fused silica are directed towards a plurality of heated substrates. The particles attach on the substrates and form shaped bodies of fused silica called preforms. For uniformity the substrates are rotated. Dopant is be added in order to alter the index of refraction of the fused silica. Prepared soot preforms are vitrified in situ. The material is processed into quartz tubes for fiber optics and other applications, quartz rods for fused silica wafers for semiconductors and various optical applications and quartz plates for wafer processing and optical windows.

Abstract: A method and device for providing an optical fiber secondary preform by collapsing an over-cladding tube on an optical fiber primary preform is disclosed in the present invention. The device for over cladding the optical fiber primary preform includes a hand bar as a first supporter for supporting the optical fiber primary preform, which hand bar has a sealing-up part of the over-cladding tube on an outer diameter part thereof and also includes a supporting handle tube as a second supporter for supporting the over-cladding tube, which the purity of the supporting handle tube is different from that of the over-cladding tube. Also the supporting handle tube includes a ring to make it equal two centers of the optical fiber primary preform and the over-cladding tube.

Abstract: Methods, systems, and apparatus consistent with the present invention use a beam of laser energy to concentrically form an optical preform from two or more concentric glass objects, such as two glass tubes or a hollow glass tube and a solid glass rod. The glass objects are placed in a concentric configuration where the outer object has an inner surface that is placed proximate to an outer surface of the inner object. Once these are assembled, a beam of laser energy is generated, positioned, and applied to a starting point in the gap defined by the inner surface and the outer surface. Once the laser beam is applied and is reflecting down into the gap, the beam of laser energy is moved relative to the starting point as the beam is concurrently applied. This heats the inner surface and outer surface so that the two objects can be joined to form the optical preform. In another aspect of the invention, a coating layer is disposed within the gap and can be heated by the laser as it is applied within the gap.

Abstract: A glass preform (10) is drawn into a fiber. Holes (13), running the length of the preform (10), collapse during the drawing, this causes the core (11) to have an elliptical cross section.

Abstract: Fiber is drawn from a preform comprising a silica body, e.g., a sol-gel derived overcladding or substrate tube. Prior to sintering, the body is treated with a gaseous mixture containing one or more non-oxygenated sulfur halides, to remove and/or reduce the size of refractory oxide particles, and/or dehydroxylate the body. Removal of metal oxide particles or reduction in their size contributes to drawing of optical fiber exhibiting desirable strength, since such particles act as initiation sites for breakage. Advantageously, the halides include sulfur chlorides, which provide desirable improvements compared to treatment by oxygenated sulfur chlorides such as thionyl chloride (SOCl2).

Abstract: The invention provides a monomode preform (2) comprising a mother preform (22) housed in an outer sleeve tube (20). It is characterized in that it also includes an intermediate tube (21) between the mother preform (22) and said outer tube (20), the intermediate tube (21) possessing viscosity at fiber-drawing temperature which is less than the viscosity(ies) at fiber-drawing temperature of said mother preform (22) and of said outer tube (20). The invention also provides a method of manufacturing a monomode optical fiber. The fiber has a core that is better centered and less deformed than in the prior art. An application of the invention lies in making an optical amplifier.