Abstract: The invention relates to a multimode optical fiber having a refractive index profile, comprising a light-guiding core surrounded by one or more cladding layers. The present invention furthermore relates to an optical communication system comprising a transmitter, a receiver and a multimode optical fiber.

Abstract: Methods for producing a semifinished part for the manufacture of an optical fiber are disclosed. The methods are optimized in terms of bending. The methods include the steps of providing a shell tube with a shell refractive index which is lower in relation to the light-conducting core. Then, at least one protective, intermediate and/or barrier layer is applied to a radially outermost and/or innermost tube surface of the respective shell tube, wherein a build-up of light-conducting layers is realized on the inner side and/or the outer side of the shell tube. Finally, the shell tubes are joined by collapsing so as to form the semifinished part.

Abstract: Methods for producing a semifinished part for the manufacture of an optical fiber are disclosed. The methods are optimized in terms of bending. The methods include the steps of providing a shell tube with a shell refractive index which is lower in relation to the light-conducting core. Then, at least one protective, intermediate and/or barrier layer is applied to a radially outermost and/or innermost tube surface of the respective shell tube, wherein a build-up of light-conducting layers is realized on the inner side and/or the outer side of the shell tube. Finally, the shell tubes are joined by collapsing so as to form the semifinished part.

Abstract: A method for manufacturing a primary preform for an optical fiber wherein conditions are created in the reaction zone such that one or more glass layer packages made up of at least two separate glass layers are deposited on the interior of the substrate tube.

Abstract: A method for manufacturing a primary preform for optical fibers using an internal vapor deposition process including the steps of providing a substrate tube having supply and discharge sides, surrounding at least part of the tube by a furnace, supplying glass-forming gases to the interior of the tube via the supply side, creating a reaction zone with conditions such that deposition of glass will take place on the inner surface of the tube, and moving the reaction zone back and forth along the length of the tube between reversal points near the supply and discharge sides to form one or more preform layers on the inner surface of the tube, wherein both reversal points are surrounded by the furnace.

Abstract: A method for manufacturing a primary preform for optical fibers using an internal vapor deposition process including the steps of providing a substrate tube having supply and discharge sides, surrounding at least part of the tube by a furnace set at a temperature T0, supplying doped or undoped gases via the supply side, creating a reaction zone to promote deposition, and moving the zone back and forth along the length of the tube between reversal points near the supply and discharge sides to form at least one preform layer, which at least one layer comprises several glass layers.

Abstract: The present invention relates to a method for manufacturing a preform for optical fibers, wherein deposition of glass-forming compounds on the substrate takes place. The present invention furthermore relates to a method for manufacturing optical fibers, wherein one end of a solid preform is heated, after which an optical fiber is drawn from said heated end.

Abstract: In a technique for fabricating a birefringent optical fiber, a preform rod is fabricated having a longitudinal axis, an outer peripheral surface, and a selected refractive index variation. At least one longitudinal groove is cut into the preform rod through its outer peripheral surface, wherein the at least one longitudinal groove has a cross sectional area equal to that of a respective birefringence-inducing stress element to be loaded into the groove, such that when the stress element is loaded into the groove, a portion of the stress element protrudes outside of the circumference of the preform. A respective birefringence-inducing stress element is loaded into the at least one longitudinal groove. A preform assembly is created by positioning the loaded preform rod within an overcladding tube. The preform assembly is drawn into optical fiber.

Abstract: Provided is a method of manufacturing an optical fiber base material using a MCVD method, including: a step of heating a glass tube while rotating the glass tube and supplying a gas into a through-hole of the glass tube, wherein in at least a part of the step, the inside of the through-hole is pressurized so that an outer diameter of the glass tube increases.

Abstract: A deterministic methodology is provided for designing optical fibers that support field-flattened, ring-like higher order modes. The effective and group indices of its modes can be tuned by adjusting the widths of the guide's field-flattened layers or the average index of certain groups of layers. The approach outlined here provides a path to designing fibers that simultaneously have large mode areas and large separations between the propagation constants of its modes.

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 for manufacturing an optical fiber preform includes the steps of depositing an inner cladding and a central core inside a fluorine doped silica tube and thereafter collapsing the silica tube to form a primary preform. The fluorine doped silica tube has a cross section area that is no more than about 15 percent smaller than the cross section area of the resulting primary preform. The present method facilitates reduced-cost manufacturing of a high-capacity optical fiber preform, which may be drawn to produce an optical fiber having reduced transmission losses.

Abstract: An optical fiber preform includes a core portion, in which the core portion includes an alkali-metal-doped core glass portion doped with an alkali metal, the maximum concentration of oxygen molecules in the core portion is 30 mol ppb or more, and the average concentration of the alkali metal in the core portion is 5 atomic ppm or more. A method of manufacturing an optical fiber preform includes an alkali-metal-doping step of doping a pipe composed of silica-based glass with an alkali metal, an oxygen-molecule-doping step of doping the glass pipe with oxygen molecules, and a collapsing step of collapsing the glass pipe by heating the glass pipe, in which the optical fiber preform is manufactured.

Abstract: The present invention relates to an apparatus and related method for manufacturing an optical preform. The present invention embraces a novel insert tube that is strategically positioned within a quartz substrate tube during the internal vapor deposition process.

Abstract: The present invention relates to a method for manufacturing a preform for optical fibres, wherein deposition of glass-forming compounds on the substrate takes place. The present invention furthermore relates to a method for manufacturing optical fibres, wherein one end of a solid preform is heated, after which an optical fibre is drawn from said heated end.

Abstract: A hydrogen-resistant optical fiber particularly well-suitable for downhole applications comprises a relatively thick pure silica core and a depressed-index cladding layer. Interposed between the depressed-index cladding layer and the core is a relatively thin germanium-doped interface. By maintaining a proper relationship between the pure silica core diameter and the thickness of the germanium-doped interface, a majority (preferably, more than 65%) of the propagating signal can be confined within the pure silica core and, therefore, be protected from hydrogen-induced attenuation problems associated with the presence of germanium (as is common in downhole fiber applications). The hydrogen-resistant fiber of the present invention can be formed to include one or more Bragg gratings within the germanium-doped interface, useful for sensing applications.

Abstract: The present invention relates to a method for manufacturing a preform for optical fibers, wherein deposition of glass-forming compounds on the substrate takes place. The present invention furthermore relates to a method for manufacturing optical fibers, wherein one end of a solid preform is heated, after which an optical fibre is drawn from said heated end.

Abstract: The specification describes methods for the manufacture of very large optical fiber preforms wherein the core material is produced by MCVD. Previous limitations on preform size inherent in having the MCVD starting tube as part of the preform process are eliminated by removing the MCVD starting tube material from the collapsed MCVD rod by etching or mechanical grinding. Doped overcladding tubes are used to provide the outer segments of the refractive index profile thus making most effective use of the MCVD produced glass and allowing the production of significantly larger MCVD preforms than previously possible.

Abstract: Disclosed is a method of heat treating quartz glass deposition tubes at between 900° C. and 1200° C. for at least 115 hours. The resulting deposition tubes are useful in forming optical preforms that can yield optical fibers having reduced added loss.

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.

Abstract: A method of forming an optical fiber preform using, for example, an MCVD process, is modified to reduce the presence of hydrogen-induced transmission losses in an optical fiber drawn from the preform. A relatively porous, unsintered soot layer is first formed (similar to the initial soot layer commonly associated with the solution-doped process of the prior art) and then subjected to a flow of a metal halide (such as SiCl4) to reduce the presence of excess oxygen. It is imperative that the metal halide treatment occur in the absence of oxygen. Sintering of the treated layer, followed by a conventional collapsing process is then used to form the inventive preform. In accordance with the present invention, both the sintering and collapsing steps are performed in a non-oxygen based ambient. When the drawn fiber is then later exposed to hydrogen, the lack of oxygen thus eliminates the formation of Si—OH and the associated attenuation problems.

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 core rod is inserted into a cladding pipe, moisture in a space between the core rod and the cladding pipe is removed, and an optical fiber is drawn while the space is connected to a dry-gas atmosphere and/or being decompressed and while the core rod and the cladding pipe are being unified with each other. Alternatively, the core rod is inserted into the cladding pipe, and an optical fiber is drawn from one end while moisture on the surface of the core rod and the internal surface of the cladding pipe is being removed. Accordingly, a high quality optical fiber is manufactured with good productivity.

Abstract: The invention relates to a multimode optical fibre having a refractive index profile, comprising a light-guiding core surrounded by one or more cladding layers. The present invention furthermore relates to an optical communication system comprising a transmitter, a receiver and a multimode optical fibre.

Abstract: A graded-index multimode fiber includes a core made of silica glass, the core having a central region and an outer peripheral region, and a cladding which is provided at an outer periphery of the core. The central region contains one of germanium and phosphorus, and the outer peripheral region contains fluorine.

Abstract: The present invention relates to a method of manufacturing an optical fibre suitable for high transmission rates, which method comprises: i) supplying one or more glass forming precursors, and possibly a dopant, to a quartz substrate tube, ii) forming a plasma in the quartz substrate tube for the purpose of bringing about a reaction mixture so as to form glass layers, which may or may not be doped, on the interior of the substrate tube, iii) collapsing the substrate tube obtained in step ii) into a perform while heating, and iv) drawing an optical fibre from the perform while heating. The present invention furthermore relates to an optical fibre suitable for high transmission rates.

Abstract: The present invention relates to a method for manufacturing a bar-shaped preform. The present invention further relates to a method for manufacturing optical fibers using the manufactured bar-shaped preform.

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

Abstract: A hybrid method of and apparatus for producing a structure capable of being drawn into an optical fiber. The method includes the steps of conducting vapor-phase reactants into an interior region of a glass tube, conducting aerosol form reactants into the interior of the glass tube. The tube is exposed to a heat, thereby causing a reaction among the vapor-phase and aerosol reactants. The reaction yields a product, in a solid form, within the tube. The apparatus includes a reaction tube, a vapor-phase reactant conduit, an aerosol-form conduit, and a heat source. The vapor-phase and aerosol-form reactant conduits facilitate introduction of vapor-phase and aerosol-form reactants into the reaction tube. The aerosol-form reactants are introduced proximate to a reaction zone created by the heat source. The aerosol-form reactants conduit and heat source travel the axial length of the reaction tube.

Abstract: The invention provides a low cost method of manufacturing high capacity preforms by chemical vapor deposition. More particularly, there is described a method of manufacturing an optical fiber preform, which method comprises the steps of providing a substrate tube of silica doped with sufficient chlorine to obtain an OH concentration of less than 100 ppb and doped with sufficient fluorine proportional to the chlorine doping to obtain a refractive index that is lower than that of a natural silica, depositing inner cladding and an optical core inside the substrate tube, collapsing the substrate tube to form a primary preform, and depositing outer cladding of said natural silica on the resulting primary preform. The invention is applicable to manufacturing optical fibers.

Abstract: The invention relates to a method for manufacture of a quartz glass preform for an optical fibre consisting of the following steps: preparation of a hollow cylinder made of porous quartz glass which exhibits an inner layer with a doping substance which increases the refractive index of quartz glass and an outer layer surrounding the inner layer, with a lower refractive index, and collapse of the hollow cylinder characterised by collapse of the porous hollow cylinder onto a quartz glass rod containing the doping substance.

Abstract: An optical fiber preform manufacturing method whereby a clad layer and core layer are deposited on the inner surface of a preform tube for forming a deposited tube. One end of the deposited tube is shrunk and closed. The deposited tube which has a closed end is arranged extending vertically through a circular heater. A heat is applied to the deposited tube at a temperature lower than the softening point of a deposited tube, exhausting contaminants existing in the interior of the deposited tube while moving the circular heater. The heating temperature of the circular heater is then set to a temperature not lower than the softening point of the deposited tube-to shrink and close the deposited tube.

Abstract: Method for fabricating an optical fiber preform substantially without hydroxyl group in core includes forming clad layer having relatively low refractive index by depositing soot (SiO2, GeO2) to inner surface of quartz tube; and forming core layer having relatively high refractive index on clad layer, which includes (a) a base core layer forming step composed of generating soot by heating inside of quartz tube to 1000° C.-1400° C. with introducing reaction gases (SiCl4GeCl4) into quartz tube, accumulating soot on clad layer removing hydroxyl-groups (OH) and moisture from soot and tube by heating inside of quartz tube to 600° C.-1200° C. with introducing dehydration gases (He, Cl2; O2) into quartz tube, and sintering and vitrifying soot by heating quartz tube inside over 1700° C. with introducing dehydration gas (He, Cl2, O2); and (b) a step of forming at least one additional core layer on base core layer by repeating the accumulating/dehydrating/sintering of the step (a) at least one time.

Abstract: The present invention relates to a method of manufacturing an optical fibre by carrying out one or more a chemical vapour deposition reactions in a substrate tube, which method comprises the following steps:

Abstract: The specification describes methods for the manufacture of very large optical fiber preforms wherein the core material is produced by MCVD. Previous limitations on preform size inherent in having the MCVD starting tube as part of the preform process are eliminated by removing the MCVD starting tube material from the collapsed MCVD rod by etching or mechanical grinding. Doped overcladding tubes are used to provide the outer segments of the refractive index profile thus making most effective use of the MCVD produced glass and allowing the production of significantly larger MCVD preforms than previously possible.

Abstract: The specification describes an improved optical fiber design in which the criteria for high performance in a Raman amplified optical system, such as moderate effective area, moderate dispersion, low dispersion slope, and selected zero dispersion wavelength, are simultaneously optimized. In preferred embodiments of the invention, the dispersion characteristics are deliberately made selectively dependent on the core radius. This allows manufacturing variability in the dispersion properties, introduced in the core-making process, to be mitigated during subsequent processing steps.

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: The present invention provides an improved process for making rare earth doped preforms and fibers by a combination of MCVD technique and solution doping method, said method comprising developing matched or depressed clad structure inside a silica glass substrate tube followed by deposition of unsintered particulate layer containing GeO2 and P2O5 for formation of the core and solution doping by soaking the porous soot layer into an alcoholic/aqueous solution of RE-salts containing co-dopants like AlCl3/Al(NO3)3 in definite proportion, controlling the porosity of the soot, dipping period, strength of the solution and the proportion of the codopants to achieve the desired RE ion concentration in the core and minimize the core clad boundary defects and followed by drying, oxidation, dehydration and sintering of the RE containing porous deposit and collapsing at a high temperature to produce the preform and overcladding with silica tubes of suitable dimensions and fiber drawing to produce fibers.

Abstract: Fluorine doping of trench layers in MCVD preforms is enhanced by exposing a silica soot layer, produced by MCVD, to a fluorine-containing gas at high pressure. The high pressure exposure is integrated into the MCVD process.

Abstract: An apparatus and method for fabricating an optical fiber, an optical fiber preform, and an optical fiber core rod are disclosed herein. In particular, the process of fabricating an optical fiber preform involves, during a modified chemical vapor deposition process, collapsing the substrate tube into an optical fiber preform, and compressing the optical fiber preform in the longitudinal direction. An optical fiber preform that is shorter, but larger in diameter is thus formed. The optical fiber preforms therefore can be stacked during the optical fiber fabrication process, which is useful in drawing longer optical fibers with comparable outer diameter and core diameter to that used as the industry standard.

Abstract: The present invention relates to a method for producing a preform, which is substantially free of OH impurities, for an optical fiber, wherein one or more quartz layers, which may or may not be doped, are deposited on the internal surface of a quartz glass support tube, in which method a furnace is moved axially with respect to the support tube, and after the quartz layers have been deposited the support tube is contracted into a bar-shaped preform while being heated, wherein the furnace comprises an electrical resistance furnace, in which furnace the support tube is rotated, with the space between the rotating support tube and the furnace being washed with an inert gas.

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

Abstract: The present invention includes a method of making a preform for an enhanced photosensitive fiber comprising depositing successive layers of optical material the inside a tube using modified chemical vapor deposition, and collapsing the layers of optical material in a reducing atmosphere with a positive pressure. The present invention also includes a method of making an enhanced photosensitive fiber comprising making a preform using modified chemical vapor deposition wherein the preform is collapsed in a reducing atmosphere with a positive pressure and drawing the preform into a fiber.

Abstract: A method for producing an optical fiber preform is disclosed. The fiber core is solution-doped with a high dopant concentration of an index modifier, preferably aluminum. High aluminum concentrations can be achieved without incorporating phosphorus in the core.

Abstract: The present invention relates to a method for producing a perform, which is substantially free of PH impurities, for an optical fibre, wherein one or more quartz layers, which may or may not be doped, are deposited on the internal surface of a quartz glass support tube, in which method a furnace is move axially with respect to the support tube, and after the quartz layers have been deposited the support tube is contracted into a bar-shaped perform while being heated, wherein the furnace comprises an electrical resistance furnace, in which furnace the support tube is rotated, with the space between the rotating support tube and the furnace being washed with an inert gas.

Abstract: A method for manufacturing an optical fiber, the method including the steps of providing a substrate tube; depositing a boron-free cladding layer; depositing a core comprising a glass including silica, and oxides of Al, Ge, Er, and Tm; collapsing the substrate tube to form a preform; and drawing the preform to yield optical fiber.

Abstract: A method for manufacturing an optical fiber, the method including the steps of: providing a substrate tube; depositing high purity silica-based cladding layers on the inside of the tube; depositing a germanium-free core comprising a glass including silica, and oxides of Al, La, Er, and Tm; collapsing the substrate tube to form a preform; and drawing the preform to yield an optical fiber.

Abstract: A method and apparatus for making optical fiber preforms using modified chemical vapor deposition (MCVD) A starting tubular member is installed on a chemical vapor deposition apparatus and, using MCVD, a predetermined amount of selectively doped silica is deposited and consolidated on the inner surface to form an intermediate uncollapsed preform tube. At least a portion of the intermediate uncollapsed preform tube is removed from the chemical vapor deposition apparatus, installed in a collapsing apparatus and collapsed. The collapsing uses an oxy-hydrogen burner or a plasma torch. Optionally, additional deposition is performed during the collapsing operation. A stretching may be performed concurrent with the collapsing.

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 of manufacturing a glass article, such as an optical fiber. The method comprises the steps of providing a glass tube with an annular passage, forming a preform from the glass tube while maintaining the annular passage, and drawing the preform into the glass article such that the annular passage closes during drawing. The preform is formed by the steps of providing glass on an inner surface of the glass tube while maintaining the annular passage and providing glass on an outer surface of the glass tube. The preform has a predetermined value &agr; that is an inner diameter of the preform after providing glass on the inner surface divided by an outer diameter of the glass tube. The preform has a predetermined value &bgr; that is the inner diameter of the preform after providing glass on the inner surface divided by the outer diameter of the preform.