Abstract: A ceramic waveguide includes: a doped metal oxide ceramic core layer; and at least one cladding layer comprising the metal oxide surrounding the core layer, such that the core layer includes an erbium dopant and at least one rare earth metal dopant being: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, thulium, ytterbium, lutetium, scandium, or oxides thereof, or at least one non-rare earth metal dopant comprising zirconium or oxides thereof. Also included is a quantum memory including: at least one doped polycrystalline ceramic optical device with the ceramic waveguide and a method of fabricating the ceramic waveguide.

Abstract: A manufacturing apparatus for an optical fiber porous preform includes a reaction chamber configured to accommodate a starting material; at least one main burner provided in the reaction chamber, the at least one main burner being configured to be supplied with a gas containing at least a source gas and a flammable gas, such that particulates are to be generated from reaction of the source gas and the flammable gas and deposited on the starting material; at least one auxiliary burner configured to be directed toward an end portion of the starting material on which the particulates are to be deposited; and an airflow guide provided such that at least part of the airflow guide is located across the at least one auxiliary burner from the starting material.

Abstract: A system and methods are described herein for preheating a preform in a preheater furnace and then transferring the preheated preform to a consolidation furnace for chemical treatment and sintering the preform into a clear glass which can be drawn into optical fiber. In addition, the preheater furnace is described herein which is configured to heat the preform per a predetermined heat-profile until the preform is uniformly heated to a temperature above 1000° C.

Abstract: A disclosed multimode optical fiber comprises a core and a cladding surrounding the core. The core has an outer radius r1 in between 20 ?m and 30 ?m. The cladding includes a first outer cladding region having an outer radius r4a and a second outer cladding region having an outer radius r4b less than or equal to 45 ?m. The second outer cladding region comprises silica-based glass doped with titania. The optical fiber further includes a primary coating with an outer radius r5 less than or equal to 80 ?m, and a thickness (r5?r4) less than or equal to 30 ?m. The optical fiber further includes a secondary coating with an outer radius r6 less than or equal to 100 ?m. The secondary coating has a thickness (r6?r5) less than or equal to 30 ?m, and a normalized puncture load greater than 3.6×10?3 g/micron2.

Abstract: Methods and apparatuses for forming optical preforms from silica glass soot are disclosed. According to one embodiment, a method for forming an optical preform may include loading silica glass soot in a mold cavity of a mold body. The mold body may be rotated at a rotational speed sufficient to force the silica glass soot towards an inner wall of the mold body. Thereafter the silica glass soot is compressed in an inward radial direction as the mold body is rotated to form a soot compact layer.

Abstract: Methods and apparatuses for forming optical preforms from silica glass soot are disclosed. According to one embodiment, a method for forming an optical preform may include loading silica glass soot in a mold cavity of a mold body. The mold body may be rotated at a rotational speed sufficient to force the silica glass soot towards an inner wall of the mold body. Thereafter the silica glass soot is compressed in an inward radial direction as the mold body is rotated to form a soot compact layer.

Abstract: A muffle tube inspection method inspects a muffle tube used for dehydrating and sintering a silica glass-based optical fiber preform, the muffle tube includes a sintering furnace provided with a furnace body covering a heater disposed around a periphery of the muffle tube. The method detects a crack generated at the muffle tube by measuring a pressure inside the furnace body while varying a pressure inside the muffle tube.

Abstract: Optical preforms and methods for forming optical preforms are disclosed. According to one embodiment, a method for producing an optical preform includes compressing silica-based glass soot to form a porous optical preform comprising a soot compact. The porous optical preform is heated to a dwell temperature greater than or equal to 100° C. Thereafter, the porous optical preform is humidified at the dwell temperature in a water-containing atmosphere having a dew point greater than or equal to 30° C. to form a humidified porous optical preform. The soot compact portion of the humidified porous optical preform generally comprises greater than or equal to 0.5 wt. % water.

Abstract: A method of forming a cladding portion of an optical fiber preform assembly includes positioning a glass core cane in a mold cavity and loading the mold cavity with silica glass soot. The silica glass soot is compressed in an axial direction as the vibratory energy is applied to the mold body to form a soot compact around the glass core cane, wherein the soot compact is the cladding portion of an optical fiber preform assembly and the glass core cane is a core portion of the optical fiber preform assembly.

Abstract: The present invention provides an apparatus for sintering a glass preform for an optical fiber, wherein the glass preform for the optical fiber is received in a muffle tube and is heated in an atmospheric gas while being suspended on a shaft and supported thereon, the apparatus comprising: a first gas seal that is provided at an upper end of the muffle tube, the shaft being inserted therethrough; a buffering chamber that is provided above the first gas seal and that covers the shaft; a second gas seal that is provided at an upper end of the buffering chamber, the shaft being inserted therethrough; and a unit that introduces the atmospheric gas exhausted from the muffle tube into the buffering chamber.

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

Abstract: A porous layer is formed by depositing a silica glass particle around a core rod. The porous layer is dehydrated. The dehydrated porous layer is sintered under a decreased pressure until the dehydrated porous layer becomes a translucent glass layer containing a closed pore. The translucent glass layer is vitrified under an ambient atmosphere including an inert gas other than a helium gas.

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

Abstract: Provided is a method of manufacturing an optical fiber preform, comprising obtaining a base material ingot by sintering a porous glass base material at a high temperature to change the porous glass base material into glass while retaining an unsintered portion at one end thereof that is not completely changed to glass; and while relatively moving a heating means in a longitudinal direction of the base material ingot, applying a tensile force to a heated portion and beginning to extend the unsintered portion from one side to decrease a diameter of and extend the base material ingot.

Abstract: The invention relates to a known method for the production of a cylinder from quartz glass, comprising a step, wherein an SiO2 body which comprises a porous SiO2 soot layer and has a lower end, an upper end, and an outer casing, is sintered to form said quartz glass cylinder in a vitrification furnace, and is being held in a vertical orientation by means of a retaining device, which comprises an upper retaining element connected at the upper end of the SiO2 body, and a lower retaining element disposed on the lower end. In order to provide a method based thereon, by means of which even heavy bodies made of porous SiO2 can be safely retained during vitrification, the invention provides that the retaining device has a dimensionally stable connecting part, which extends inside the vitrification furnace along the outer casing of the SiO2 body and which connects the upper and the lower retaining elements to each other.

Abstract: A method of manufacturing an optical fiber base material having very little impurity which deteriorates the transmission characteristic of an optical fiber is provided. The method of manufacturing an optical fiber base material including: producing a core member for the optical fiber base material by dehydrating and transparently vitrifying a base material formed by depositing glass particles; and drawing the core member and then adding a cladding thereto at a desired core to cladding ratio, wherein the dehydrating includes suspending the base material in a furnace tube having a heating region in a first atmosphere at a first temperature, the base material passing through the heating region as upwardly moving, and the transparently vitrifying includes situating the base material below once and then allowing the base material to pass through the heating region in a second atmosphere at a second temperature as upwardly moving again.

Abstract: ESD safe ceramic component is provided which includes a sintered composition which is formed of a base material and a resistivity modifier. The base material includes a primary component and a secondary component, the primary component including Al2O3 and the secondary component including tetragonal-ZrO2.

Abstract: Described is a method of fabricating an optical fiber preform that includes a deep index trench comprising a shallower outer trench portion formed on a substrate tube and a deeper inner trench portion formed on the shallower outer trench portion. Each of the shallower outer trench and deeper inner trench portions comprises multiple silica layers. The method comprises the steps of: (1) forming each layer of the shallower outer trench portion in a single-pass deposition of a F-containing silica layer; and (2) forming each layer of the deeper inner portion in a double-pass deposition in which, in a first pass, a layer of silica soot is deposited and then, in a second pass, the soot is sintered in the presence of SiF4.

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

Abstract: In order to prevent thermal deformation of a thermal insulating board and scattering of radiant heat when sintering porous glass base material, provided is a thermal insulating member is arranged on a dummy rod above a porous glass base material, which is formed by depositing glass fine particles on the outside of a starting member formed by connecting the dummy rod to at least one end of a core rod, when heating the porous glass base material to achieve sintering. The thermal insulating member comprises a cylindrical insulating cylinder; an insulating upper board connected to a top end of the insulating cylinder; an insulating lower board connected to a bottom end of the insulating cylinder; and a thermal deformation preventing member that prevents thermal deformation of at least one of the insulating cylinder, the insulating upper board, and the insulating lower board.

Abstract: A known method for producing a cylinder of quartz glass comprises a method step in which a porous SiO2 body comprising a central inner bore, a lower end and an upper end is sintered in a sintering furnace zone by zone, starting from the upper end, to obtain the quartz glass cylinder, a holding device being used by means of which the SiO2 body is held standing in vertical orientation during a first sintering phase and suspended in a second sintering phase.

Abstract: Method of making a microstructured optical fiber. Silica glass based soot is deposited on a substrate to form at least a portion of an optical fiber preform by traversing a soot deposition burner with respect to said substrate at a burner traverse rate greater than 3 cm/sec, thereby depositing a layer of soot having a thickness less than 20 microns for each of a plurality of burner passes. At least a portion of the soot preform is then consolidated inside a furnace to remove greater than 50 percent of the air trapped in said soot preform, said consolidating taking place in a gaseous atmosphere containing krypton, nitrogen, or mixtures thereof under conditions which are effective to trap a portion of said gaseous atmosphere in said preform during said consolidation step, thereby forming a consolidated preform which when viewed in cross section will exhibit at least 50 voids therein.

Abstract: Method for producing a semifinished product from synthetic quartz glass Methods for producing a semifinished product from synthetic quartz glass by plastic deformation of a softened SiO2 mass in a melt mold are known. Starting from this, to avoid fusion defects as much as possible and to obtain semifinished products of quartz glass in a reproducibly high quality, a method is suggested that comprises the following steps: (a) providing a porous SiO2 soot body, (b) zonewise sintering of the SiO2 soot body in the melt mold at a sintering temperature and during a sintering period with formation of a completely sintered transparent quartz glass body, and directly thereafter (c) shaping the sintered quartz glass body by softening in the melt mold with formation of a viscous quartz glass mass which fills the volume of the melt mold entirely or partly, and (d) cooling the quartz glass mass and removing the mass from the melt mold with formation of the semifinished product.

Abstract: A method of producing an optical fiber preform by heating a glass preform that has a glass rod and a silica glass porous body and includes a valid portion and invalid portions, comprising: heating the glass preform while moving the glass preform along its axial direction relative to a heater; stopping the relative movement or decreasing a speed of the relative movement when an invalid portion positioned at a tail end reaches a vicinity of the heater; heating the invalid portion for a predetermined time while maintaining a temperature at which the silica glass porous body can be vitrified; decreasing the heating temperature to a temperature determined by adding 200° C. to an annealing point of a silica glass; and removing the glass preform to the outside of the heating furnace without increasing the heating temperature to the temperature at which the silica glass porous body is vitrified.

Abstract: A known method for producing a hollow cylinder of synthetic quartz glass comprises the steps of: (a) providing an inner tube of synthetic quartz glass having an inner bore defined by an inner wall, (b) cladding the inner tube (3?) with an SiO2 soot layer (4?), and (c) sintering the SiO2 soot layer with formation of the hollow cylinder. Starting therefrom, to indicate a method in which on the one hand the sintering process is completed before the hollow cylinder is further processed together with the core rod, and in which on the other hand a complicated machining of the inner bore of the hollow cylinder of quartz glass is not required, the invention suggests that during sintering the surface temperature of the inner wall of the inner tube should be kept below the softening temperature.

Abstract: A known method for producing a cylinder of quartz glass comprises a soot depositing process, in which SiO2 particles are deposited on an elongate carrier rotating about an axis of rotation with formation of a porous, hollow-cylindrical soot body, and a sintering process in which the soot body comprising an inner bore with inner wall, a longitudinal axis, an upper end and a lower end is held suspended in vertical orientation in a furnace, a holding element being provided for holding purposes, which projects from the upper end into the inner bore of the soot body and acts on a bearing provided in the inner bore.

Abstract: A known method for producing synthetic quartz glass comprises the method steps: (a) forming a cylindrical SiO2 soot body having an inner portion and at least one free cylinder jacket surface surrounding the inner portion; (b) thermally drying the porous soot body; and (c) vitrifying the dried soot body with formation of the cylinder from synthetic quartz glass.

Abstract: A method of manufacturing a cylindrical glass optical waveguide preform having a low water content centerline region, for use in the manufacture of optical waveguide fiber, is disclosed. The centerline region of the glass optical waveguide preform has a water content sufficiently low such that an optical waveguide fiber producible from the glass optical waveguide preform of the present invention exhibits an optical attenuation of less than about 0.35 dB/km, and preferably less than about 0.31 dB/km, at a measured wavelength of 1380 nm. Method of manufacture of a porous core mandrel used in the manufacture of such a glass optical waveguide preform is also disclosed.

Abstract: A method of incorporating within a glass optical waveguide a material of interest having a property of interest that would be neutralized by exposure to molten glass includes combining pieces of a light-transmissive first glass with the material of interest. The combined first glass and material of interest are shaped within a container and heated to a temperature sufficiently high to cause the glass pieces and material of interest to mutually coalesce and form a light-transmissive core rod, but not high enough that the first glass melts and neutralizes the property of interest. A cladding tube is heated and fused about the core rod to define a mono rod. An optical waveguide through which light propagates by internal reflection, and which incorporates the material of interest, is defined when the cladding tube comprises a glass that renders the cladding of lower refractive index than the core rod.

Abstract: Provided are a manufacturing method of an optical fiber base material and an optical fiber base material manufactured in the manufacturing method, the manufacturing method including: a process of combining at least two core base materials 70 by fusion-bonding to produce a single core base material; a process of fusion-bonding a pair of dummy glass rods 61 and 62 at both ends of the core base material 70 to produce a starting glass rod; a process of depositing, at an outer surface of the starting glass rod, glass particles generated by flame hydrolysis, to produce a porous base material 80; and a process of sintering and vitrifying, into transparent glass, the porous base material 80, to produce an optical fiber base material 310 that includes a core portion and a clad portion.

Abstract: A glass preform manufacturing method includes: generating glass fine particles by hydrolyzing a source gas in an oxyhydrogen flame; depositing the generated glass fine particles to form a torous glass preform; immersing the porous glass preform in an additive solution including an additive solvent in which a compound containing a desired additive is dissolved to impregnate the additive solution into the porous glass preform; first replacing of replacing the additive solvent remaining in the porous glass preform with the replacement solvent by immersing the porous glass preform in which the additive solution remains in a replacement solvent in which a solubility of the additive is lower than that in the additive solvent and having miscibility with the additive solvent; drying the porous glass preform after the first replacing; and sintering the dried porous glass preform to transparently vitrify the dried porous glass preform.

Abstract: Provided is a method of manufacturing an optical fiber preform, comprising obtaining a base material ingot by sintering a porous glass base material at a high temperature to change the porous glass base material into glass while retaining an unsintered portion at one end thereof that is not completely changed to glass; and while relatively moving a heating means in a longitudinal direction of the base material ingot, applying a tensile force to a heated portion and beginning to extend the unsintered portion from one side to decrease a diameter of and extend the base material ingot.

Abstract: The method for producing and processing a preform comprises a preliminary process phase, in which silica grain is supplied into the interior space of a silica tube having an open upper end and a closed lower end, in order to obtain an unprocessed preform, and includes a final process phase, in which the interior space of the silica tube is closed, a condition of reduced pressure is generated, the unprocessed preform is heated with a final process temperature in order to fuse the silica tube and the silica grain. According to the invention the silica grain entering the interior space is thermally treated during the preliminary process phase with an intermediate process temperature that lies under the melting point of the silica grain.

Abstract: A method for producing a fused silica glass containing titania includes synthesizing particles of silica and titania by delivering a mixture of a silica precursor and a titania precursor to a burner, growing a porous preform by successively depositing the particles on a deposition surface while rotating and translating the deposition surface relative to the burner, and consolidating the porous preform into a dense glass.

Abstract: Method for manufacturing an optical fiber perform, which forms a glass fine particle deposition portion composed of glass fine particles on a glass rod, and suspends the glass fine particle deposition vertically into a heating furnace to heat, and transparentize, the glass fine particle deposition. The method comprises the following steps: forming a hazy portion before heating, by causing a surface portion of the glass rod to sublime and adhere to at least a portion of a region closer to one end of the glass rod than a region of the glass rod where the deposition portion is formed; forming the deposition portion by depositing the glass fine particles on the glass rod; and transparentizing the deposition portion by heating the glass fine particle deposition in a state where the proximal end of the glass rod where the hazy portion is formed is suspended vertically into the heating furnace.

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

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

Abstract: 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 of manufacturing a cylindrical glass optical waveguide preform having a low water content centerline region, for use in the manufacture of optical waveguide fiber, is disclosed. The centerline region of the glass optical waveguide preform has a water content sufficiently low such that an optical waveguide fiber producible from the glass optical waveguide preform of the present invention exhibits an optical attenuation of less than about 0.35 dB/km, and preferably less than about 0.31 dB/km, at a measured wavelength of 1380 nm. Method of manufacture of a porous core mandrel used in the manufacture of such a glass optical waveguide preform is also disclosed.

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

Abstract: An optical fiber preform comprising a plurality of longitudinal air holes is subjected to a thermal treatment (i.e., heating), coupled with the application of a compressive force on either end of the heated preform to compress the entire preform structure a predetermined amount. The thermal compression treatment has been found to smooth any roughened glass surfaces and heal microcracks that may have formed during the preform fabrication process, essentially “knitting” the glass material back together and forming a preform of improved quality over the prior art microstructured preforms.

Abstract: An optical fiber comprising: (i) a core; (ii) a cladding surrounding the core; wherein the cladding comprises a cladding ring that: (a) has a width W equal to or less than 10 microns; (b) includes at least 50 airlines, each airline having a maximum diameter or a maximum width of not more than 2 microns and more than 50% of said airlines have a length of more than 20 m; (c) has an air fill fraction of 0.1% to 10%, and (d) has an inner radius Rin and an outer radius Rout, wherein 6 ?m?Rin?14 ?m, and 8 ?m?Rout?14 ?m; and (iii) an outer cladding surrounding said cladding ring.

Abstract: A method and apparatus for consolidating an optical fiber preform, wherein the optical fiber preform is located in a furnace comprising a muffle tube, said muffle tube comprising an inner section and an outer section surrounding the inner section. The inner and outer sections are comprised of different materials, and the preform is exposed to a pressure less than 0.8 atm while simultaneously exposing said preform to a temperature of at least 1000 C.

Abstract: A known method for producing synthetic quartz glass with a predetermined hydroxyl group content comprises the following steps: a porous SiO2 soot body is produced by flame hydrolysis or oxidation of a silicon-containing start compound and by layerwise deposition of SiO2 particles on a rotating support; the soot body is subjected to a dehydration treatment in a reaction gas-containing drying atmosphere at a drying temperature for removing hydroxyl groups; and the SiO2 soot body is vitrified into a body consisting of the synthetic quartz glass. Starting from this, and in order to permit a reproducible and reliable manufacture of synthetic, UV-radiation resistant quartz glass with predetermined hydroxyl group content and low chlorine content, it is suggested according to the invention that the dehydration treatment according to method step (b) comprises a drying phase during which ozone is used as the reaction gas, whereby the ozone content of the drying atmosphere is between 0.5% by vol. and 10% by vol.

Abstract: A method and apparatus for making an optical fiber preform. The apparatus has an outer wall and an inner wall. The outer wall surrounds the inner wall and the inner wall surrounds an inner cavity of the apparatus. A consolidated glass rod is deposited in the inner cavity after which particulate glass material, such as glass soot, is deposited in the inner cavity around the glass rod. A radially inward pressure is applied against the particulate glass material to pressurize the particulate glass material against the glass rod.

Abstract: A fiber-optic apparatus for receiving emitted radiation from a diode laser having at least one diode laser bar with a multiplicity of emitters which are arranged in at least one row alongside one another in the direction of their longitudinal axis. The fiber-optic apparatus has at least one optical fiber bundle that is associated with the diode laser bar and into which the laser beam is injected. Each emitter has a multiplicity of associated optical fibers. The optical fibers are hot-fused to one another under pressure and without regulation on the input side in order to form at least one fiber wedge with an inlet surface. The emitters of the diode laser bar are directly associated with at least one inlet surface in order to completely receive the laser light emitted from the diode laser bar.

Abstract: A method of forming an alkali metal oxide-doped optical fiber by diffusing an alkali metal into a surface of a glass article is disclosed. The silica glass article may be in the form of a tube or a rod, or a collection of tubes or rods. The silica glass article containing the alkali metal, and impurities that may have been unintentionally diffused into the glass article, is etched to a depth sufficient to remove the impurities. The silica glass article may be further processed to form a complete optical fiber preform. The preform, when drawn into an optical fiber, exhibits a low attenuation.

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 deposition glass soot for making an optical fiber preform. A fuel and a glass precursor are flowed to a burner flame forming glass soot which is deposited onto a glass target. By first depositing an insulating layer of glass soot with a low velocity burner flame, the amount of water which may be adsorbed into the surface of the glass target can be reduced. Thereafter, the flame velocity may be increased to increase the deposition rate of the glass soot without significantly increasing the concentration of water incorporated into the glass target.

Abstract: A process and an apparatus for drying and consolidating an optical fibre preform in a furnace tube comprising a heating chamber, wherein an extension tube having an extension chamber configured to house at least a length portion of the preform is removably joined to the furnace tube and the drying process starts with the preform not completely inserted into the furnace tube, an upper length portion of the preform being surrounded by the extension tube joint to the furnace tube.