Abstract: Preparation of halogen-doped silica is described. The preparation includes doping silica with high halogen concentration and sintering halogen-doped silica to a closed-pore state. The sintering includes a high pressure sintering treatment and a low pressure sintering treatment. The high pressure sintering treatment is conducted in the presence of a high partial pressure of a gas-phase halogen doping precursor and densifies a silica soot body to a partially consolidated state. The low pressure sintering treatment is conducted in the presence of a low partial pressure of gas-phase halogen doping precursor and transforms a partially consolidated silica body to a closed-pore state. The product halogen-doped silica glass exhibits little foaming when heated to form fibers in a draw process or core canes in a redraw process.

Abstract: One embodiment of the disclosure relates to a method of making an optical fiber comprising the steps of: (i) exposing a silica based preform with at least one porous glass region having soot density of ? to a gas mixture comprising SiCl4 having SiCl4 mole fraction ySiCl4 at a doping temperature Tdop such that parameter X is larger than 0.03 to form the chlorine treated preform, wherein X = 1 1 + [ ( ? ? s - ? ) ? 0.209748 ? ? T dop ? Exp ? [ - 5435.33 / T dop ] y SiCl ? ? 4 3 / 4 ] and ?s is the density of the fully densified soot layer; and (ii) exposing the chlorine treated preform to temperatures above 1400° C. to completely sinter the preform to produce sintered optical fiber preform with a chlorine doped region; and (iii) drawing an optical fiber from the sintered optical preform.

Abstract: A method of producing a Fresnel zone plate (15) comprising: making available a substrate (1, 4, 7) which is rotationally symmetrical with respect to its center axis (1a, 4a, 7a); applying layers (2a-d; 5a-d; 8a-d; 11) following in succession by means of an atomic layer deposition (ALD) method to faces (1b-c; 4b-c; 7b-c) of the substrate (1, 4, 7) without rotation of the substrate (1, 4, 7) in order to form a coated substrate, and severing (3a, b; 6a, b; 9a, b) at least one slice (13) from the coated substrate (1, 4, 7), by the coated substrate (1, 4, 7) being divided at least once at a right angle to the center axis (1a, 4a, 7a).

Abstract: One embodiment of the disclosure relates to a method of making an optical fiber comprising the steps of: (i) exposing a silica based preform with at least one porous glass region having soot density of ? to a gas mixture comprising SiCl4 having SiCl4 mole fraction ySiCl4 at a doping temperature Tdop such that parameter X is larger than 0.03 to form the chlorine treated preform, wherein X = 1 1 + [ ( ? ? s - ? ) ? 0.209748 ? T dop ? Exp ? [ - 5435.33 / T dop ] y SiCl ? ? 4 3 / 4 ] and ?s is the density of the fully densified soot layer; and (ii) exposing the chlorine treated preform to temperatures above 1400° C. to completely sinter the preform to produce sintered optical fiber preform with a chlorine doped region; and (iii) drawing an optical fiber from the sintered optical preform.

Abstract: A preparation method of rare earth ions doped alkaline earth metal silicate luminescent glass is provided. The steps involve: step 1, mixing the source compounds of cerium, terbium and alkaline earth metals and putting the mixture into solvent to get a mixed solution; step 2, impregnating the nanometer pores glass with the mixed solution obtained in step 1; step 3: calcining the impregnated nanometer pores glass obtained in step 2 in a reducing atmosphere, cooling to room temperature, then obtaining the cerium and terbium co-doped alkaline earth metal silicate luminescent glass. Besides, the rare earth ions doped alkaline earth metal silicate luminescent glass prepared with aforesaid method is also provided. In the prepared luminescent glass, cerium ions can transmit absorbed energy to terbium ions under the excitation of UV light due to the co-doping of cerium ions. As a result, the said luminescent glass has higher luminous intensity than the glass only doped with terbium.

Abstract: A method for forming an optical glass preform from a soot preform is provided. The method includes forming a soot preform, placing the soot preform in a furnace, and applying a vacuum through a centerline hole of the soot preform.

Abstract: An apparatus for manufacturing a glass perform, includes: a dummy tube section, a reservoir portion, and a cooling portion; and a glass tube section in which particles of an alkali metal compound or an alkaline earth metal compound which have flowed into the glass tube section from the dummy tube section are heated by a second heat source which performs traverse, and oxides of the particles being deposited on an inner wall and dispersed in the glass tube section. In the cooling portion of the dummy tube section, vapor of the alkali metal compound or the alkaline earth metal compound generated by heating of a first heat source is cooled and condensed by a dry gas flowing into the dummy tube section, and thereby the particles are generated.

Abstract: A multimode optical fiber, and a method of making the fiber, are provided according to the following steps and elements: forming a core preform with a graded refractive index that includes silica and an up-dopant; drawing the core preform into a core cane; forming an inner annular segment preform that includes silica soot and an up-dopant surrounding the core cane; and forming a depressed-index annular segment preform that includes silica soot surrounding the inner annular segment preform. The method also includes the steps: forming an outer annular segment preform that includes silica soot and an up-dopant surrounding the depressed-index annular segment preform; doping the inner, depressed-index and outer annular segment preforms simultaneously or nearly simultaneously with a down-dopant; and consolidating the segment preforms simultaneously or nearly simultaneously into inner, depressed-index and outer annular segments.

Abstract: A glass preform manufacturing method, includes: preparing a glass element having a rough surface; turning a raw material of an alkali metal compound or a raw material of an alkaline earth metal compound into particles; depositing particles of the alkali metal compound or the alkaline earth metal compound on the rough surface of the glass element; oxidizing the particles of the alkali metal compound or the alkaline earth metal compound while diffusing alkali metal oxide or alkaline earth metal oxide in the glass element; and manufacturing a glass preform into which the alkali metal oxide or the alkaline earth metal oxide is doped.

Abstract: Methods for forming optical fiber preforms are disclosed. According to one embodiment, a method for forming an optical fiber preform includes forming a preform core portion from silica-based glass soot. The silica-based glass soot may include at least one dopant species for altering an index of refraction of the preform core portion. A selective diffusion layer of silica-based glass soot may be formed around the preform core portion to form a soot preform. The selective diffusion layer may have an as-formed density greater than the density of the preform core portion. A diffusing species may be diffused through the selective diffusion layer into the preform core portion. The soot preform may be sintered such that the selective diffusion layer has a barrier density which is greater than the as-formed density and the selective diffusion layer prevents diffusion of the at least one dopant species through the selective diffusion layer.

Abstract: The present disclosure is directed to a doped silica-titania glass, DST glass, consisting essentially of 0.1 wt. % to 5 wt. % halogen, 50 ppm-wt. to 6 wt. % one or more oxides of Al, Ta and Nb, 3 wt. % to 10 wt. % TiO2 and the remainder SiO2. In an embodiment the halogen content can be in the range of 0.2 wt. % to 3 wt. % along with 50 ppm-wt. to 6 wt. % one or more oxides of Al, Ta and Nb, 3 wt. % to 10 wt. % TiO2 and the remainder SiO2. In an embodiment the DST glass has an OH concentration of less than 100 ppm. In another embodiment the OH concentration is less than 50 ppm. The DST glass has a fictive temperature Tf of less than 875° C. In an embodiment Tf is less than 825° C. In another embodiment Tf is less than 775° C.

Abstract: The present invention relates to a method and an apparatus for fabricating a preform (1,10,100) that can be used for drawing an active optical fiber (8). The present invention further relates to an active optical fiber (8), designed for amplification or attenuation purposes, drawn from said preform (1,10,100) and to an optical amplifier (600, 601) using a laser active optical fiber.

Abstract: Manufacturing an optical fiber by using an outside vapor deposition technique for making a substrate, applying one or more layers to the substrate using a radial pressing technique to form a soot blank, sintering the soot blank in the presence of a gaseous refractive index-modifying dopant, and drawing the sintered soot blank, provides a more efficient and cost effective process for generating complex refractive index profiles.

Abstract: The present invention relates to an optical fiber for an SPR sensor, characterized in that the optical fiber is comprised of a core layer and a cladding layer surrounding the core layer, and the cladding layer is doped with metal nanoparticles.

Abstract: A method of manufacturing a glass preform is provided. The method including, vaporizing an alkali metal compound or an alkali earth metal compound and being brought the alkali metal compound or the alkali earth metal compound into contact with a hydroxyl group on a surface of porous silica glass and dehydrating the porous silica glass, and sintering the dehydrated porous silica glass and forming a transparent glass body.

Abstract: A method for manufacturing a glass composition including a host glass, a 3p component having a concentration of about 5 mole percent to about 10 mole percent, and at least one of a 6p component having a concentration of about 1 mole percent to about 5 mole percent and a 5p component having a concentration of about 1 mole percent to about 5 mole percent, is provided. The method includes heating the host glass to a first predetermined temperature for a first period of time; mixing a powder including the 3p component and the at least one of the 5p component and the 6p component with the heated host glass into a glass/powder mixture; heating the glass/powder mixture to a second predetermined temperature for a second period of time; and cooling, after heating, the glass/powder mixture.

Abstract: Disclosed is an optical fiber that includes a central core that is suitable for transmitting and amplifying an optical signal and an inner optical cladding that is suitable for confining the optical signal transmitted within the central core. The central core is formed from a core matrix that contains silica-based nanoparticles doped with at least one rare earth element. The disclosed optical fiber can be used with limited optical losses even in an environment with strong ionizing radiation.

Abstract: Disclosed is a method of fabricating an optical fiber or an optical device doped with reduced metal ion and/or rare earth ion, comprising steps of: forming a partially-sintered fine structure in a base material for fabricating the optical fiber or the optical device; soaking the fine structure into a doping solution containing a reducing agent together with metal ion and rare earth ion during a selected time; drying the fine structure in which the metal ion and/or rare ion are/is soaked; and heating the fine structure such that the fine structure is sintered.

Abstract: In part, the invention relates to an optical probe including a torque wire; an optical fiber positioned within the torque wire; a beam director positioned coaxial with and adjacent to one end of the optical fiber; and an overcladding, positioned adjacent to and over the optical fiber and the beam director, the overcladding defining an air gap adjacent the beam director so as to cause total internal reflection alight passing from the optical fiber through the beam director. In one embodiment, the optical probe includes a beam expander and a beam shaper coaxial with and located between the optical fiber and the beam director. In another embodiment, the optical probe further includes a marker band positioned over a portion of the overcladding. In yet another embodiment, the overcladding is made of flurosilica glass.

Abstract: The present invention relates to a process for production of a synthetic quartz glass having a fluorine concentration of 1,000 mass ppm or more, the process comprising: (a) a step of depositing and growing quartz glass fine particles obtained by flame hydrolysis of a glass forming raw material onto a substrate, to thereby form a porous glass body; (b) a step of keeping the porous glass body in a reaction vessel that is filled with elemental fluorine (F2) or a mixed gas comprising elemental fluorine (F2) diluted with an inert gas and contains a solid metal fluoride, to thereby obtain a fluorine-containing porous glass body; and (c) a step of heating the fluorine-containing porous glass body to a transparent vitrification temperature, to thereby obtain a fluorine-containing transparent glass body.

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: A glass preform manufacturing method, includes: preparing a glass element having a rough surface; turning a raw material of an alkali metal compound or a raw material of an alkaline earth metal compound into particles; depositing particles of the alkali metal compound or the alkaline earth metal compound on the rough surface of the glass element; oxidizing the particles of the alkali metal compound or the alkaline earth metal compound while diffusing alkali metal oxide or alkaline earth metal oxide in the glass element; and manufacturing a glass preform into which the alkali metal oxide or the alkaline earth metal oxide is doped.

Abstract: A method of manufacturing an optical fiber preform includes preparing from a first deposition tube a first rod that includes a central core and preparing from a second deposition tube a second rod that includes a buried trench. The method further includes fitting the second rod as a sleeve over the first rod. This disclosed method facilitates the manufacture of large-capacity fiber preforms using deposition benches having small and/or medium deposition capacity.

Abstract: The present invention relates to a method for manufacturing a primary preform for optical fibres, using an internal vapour deposition process, wherein a gas flow of doped undoped glass-forming gases is supplied to the interior of a hollow substrate tube having a supply side and a discharge side via the supply side thereof, wherein deposition of glass layers on the interior of the substrate tube is effected as a result of the presence of a reaction zone.

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: A method of manufacturing an optical waveguide preform includes providing a first process gas atmosphere to a soot preform contained in a vessel. The first atmosphere is held in the vessel for a first reacting time sufficient to at least partially dope or dry the soot preform. The vessel is then at least partially refilled with a second doping or drying atmosphere. The second doping or drying atmosphere is held in the vessel for a second reacting time sufficient to further dope or dry the soot preform.

Abstract: The invention relates to an optical fiber comprising a gain medium which is equipped with: a core (22) which is formed from a transparent material and nanoparticles (24) comprising a doping element and at least one element for enhancing the use of said doping element; and an outer cladding (26) which surrounds the core. The invention is characterized in that the doping element is erbium (Er) and in that the enhancing element is selected from among antimony (Sb), bismuth (Bi) and a combination of antimony (Sb) and bismuth (Bi). According to the invention, one such fiber is characterized in that the size of the nanoparticles is variable and is between 1 and 500 nanometers inclusive, and preferably greater than 20 nm.

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: The invention relates to an optical fiber comprising a gain medium which is equipped with: a core (22) which is formed from a transparent material and nanoparticles (24) comprising a doping element and at least one element for enhancing the use of said doping element; and an outer cladding (26) which surrounds the core. The invention is characterised in that the doping element is erbium (Er) and in that the enhancing element is selected from among antimony (Sb), bismuth (Bi) and a combination of antimony (Sb) and bismuth (Bi). According to the invention, one such fiber is characterised in that the size of the nanoparticles is variable and is between 1 and 500 nanometers inclusive, and preferably greater than 20 nm.

Abstract: An optical fiber comprising: a core formed in a center axis area; an inner clad layer, disposed around the core, having a refractive index smaller than that of the core; a pore layer, disposed around the inner clad layer, having a plurality of elongated pores; and an outer clad layer, disposed around the pore layer, having a refractive index equal to or smaller than the refractive index of the core, wherein a length of the elongated pores is not larger than 200 m.

Abstract: The present invention relates to a method and an apparatus for fabricating a preform (1,10,100) that can be used for drawing an active optical fiber (8). The present invention further relates to an active optical fiber (8), designed for amplification or attenuation purposes, drawn from said preform (1,10,100) and to an optical amplifier (600, 601) using a laser active optical fiber.

Abstract: The present invention relates to a method for manufacturing an optical fiber preform using an MCVD process comprising (A) forming a predetermined thickness of a cladding layer in a preform tube by repeating a unit process of heating an outer peripheral surface of the preform tube at 1,700 to 2,5000 C using a heat source moving in a process direction, and simultaneously injecting cladding layer forming gas and chlorine (Cl) gas into the preform tube; and (B) forming a predetermined thickness of a core layer in the preform tube by repeating a unit process of heating the outer peripheral surface of the preform tube at 1,700 to 2,5000 C using the heat source moving in a process direction, and simultaneously injecting core layer forming gas and chlorine (Cl) gas into the preform tube having the cladding layer.

Abstract: The invention relates to an optical fibre comprising a gain medium which is equipped with: a core (22) which is formed from a transparent material and nanoparticles (24) comprising a doping element and at least one element for enhancing the use of said doping element; and an outer cladding (26) which surrounds the core. The invention is characterised in that the doping element is erbium (Er) and in that the enhancing element is selected from among antimony (Sb), bismuth (Bi) and a combination of antimony (Sb) and bismuth (Bi). According to the invention, one such fibre is characterised in that the size of the nanoparticles is variable and is between 1 and 500 nanometres inclusive, and preferably greater than 20 nm.

Abstract: A random array of holes is created in an optical fiber by gas generated during fiber drawing. The gas forms bubbles which are drawn into long, microscopic holes. The gas is created by a gas generating material such as silicon nitride. Silicon nitride oxidizes to produce nitrogen oxides when heated. The gas generating material can alternatively be silicon carbide or other nitrides or carbides. The random holes can provide cladding for optical confinement when located around a fiber core. The random holes can also be present in the fiber core. The fibers can be made of silica. The present random hole fibers are particularly useful as pressure sensors since they experience a large wavelength dependant increase in optical loss when pressure or force is applied.

Abstract: A method of manufacturing a glassy optical preform is disclosed that includes providing a preform having a silica soot layer and then sintering the soot layer into a glassy layer, and water is selectively added to the preform by exposing the soot layer to a gaseous water-containing atmosphere during the sintering step. The preform is controllably doped with water.

Abstract: The invention relates to the loading of quartz glass objects with hydrogen in an annealing process in a furnace for improving the homogeneity of the refractive index and the laser resistance while, at the same time, maintaining a specified stress birefringence of each of the glass objects. Initially, the distribution of the refractive index, the stress birefringence, the distribution of the hydrogen and the differences in refractive index, which are to the equalized, are determined in the respective glass object, after which the hydrogen change, which is necessary for equalizing the refractive index, is determined. Furthermore, the annealing temperature and its holding time, as well as the hydrogen concentration and the hydrogen pressure in the furnace are adjusted to achieve a sufficiently equalized distribution of refractive index.

Abstract: A method produces a glass body that contains a reduced amount of OH groups in the metallic-oxide-containing glass layer and that has a reduced amount of transmission loss due to OH groups when the glass body is transformed into an optical fiber. The production method produces an optical glass body. An optical fiber contains the optical glass body in at least one part of its region for guiding a lightwave. The production method includes the following steps: (a) introducing into a glass pipe a gas containing an organometallic compound and a glass-forming material; (b) decomposing the organometallic compound into an organic constituent and a metallic constituent; (c) heating and oxidizing the metallic constituent so that produced glass particles containing a metallic oxide are deposited on the inner surface of the glass pipe to form a glass-particle-deposited layer; and (d) consolidating the deposited layer to form a metallic-oxide-containing glass layer.

Abstract: The present invention concerns a preform for an optical fiber, an optical fiber so obtained and methods for making the same. The fiber is characterized in that porous glass doped with at least one dopant is used. Resulting fibers can be used to make high attenuation fibers.

Abstract: A large-diameter core optical fiber and a small-diameter core high optical fiber are fusion-spliced, and the spliced portion is heated to expand the core diameter of a core of the high optical fiber and form a spot size transition portion, whereby spot sizes of the optical fibers are matched and relative refractive index differences thereof are made substantially identical. Subsequently, the optical fiber is cut at an arbitrary position and the spliced portion and the spot size transition portion are placed inside a ferule with the large diameter core optical fiber arranged on a light incident and outgoing end face side of the ferrule to form an optical fiber component. The core diameter is expanded while monitoring transition loss of the splined portion to obtain an optical fiber component having an optimal spot size transition portion without an advanced technique and without increase in transition loss.

Abstract: A synthetic quartz glass for optical use, to be used by irradiation with light within a range of from the ultraviolet region to the vacuum ultraviolet region, which contains fluorine, which has a ratio of the scattering peak intensity of 2250 cm?1 (I2250) to the scattering peak intensity of 800 cm?1 (I800), i.e. I2250/I800, of at most 1×10?4 in the laser Raman spectrum, and which has an absorption coefficient of light of 245 nm of at most 2×10?3 cm?1.

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: The present invention discloses a process for making rare earth (RE) doped optical fiber by using RE oxide coated silica nanoparticles as the precursor material, more particularly the method of the present invention involves preparation of stable dispersions (sol) of RE oxide coated silica nanoparticles at ambient temperature and applying a thin coating on the inner surface of silica glass tube following dip coating technique or any other conventional methods, of the said silica sol containing suitable dopants selected from Ge, Al, P, etc.

Abstract: A method and apparatus for forming a glass article such as an optical fiber having a substantially matching viscosity across an interface associated with a first section and a second section of the optical fiber is disclosed herein. The first section has a first halogen concentration and the second section has a second halogen concentration. At least one of a partial pressure of the second halogen provided to a substrate tube and a temperature of the substrate tube is configured to affect the concentration of the second halogen in the second section. Optical fiber embodiments are also included.

Abstract: The present invention provides a method of fabricating rare earth doped preforms and optical fibers by a combination of modified chemical vapor deposition (MCVD) process and solution doping technique said MCVD process is used to develop matched or depressed clad structure inside a silica glass substrate tube followed by deposition of porous silica soot layer containing GeO2, P2O5 or such refractive index modifiers by the backward deposition method for formation of the core and presintering the deposited particulate layer by backward pass with flow of GeCl4 and/or corresponding dopant halides, soaking the porous soot layer into an alcoholic/aqueous solution of RE-salts containing codopants such as AlCl3 in definite proportion, drying, oxidation, dehydration and sintering of the RE containing porous deposit and by collapsing at a high temperature to produce the preform followed by drawing the fibers by known technique to produce fibers with suitable core-clad dimensions and geometry.

Abstract: The invention includes a method of incorporating fluorine into a preform that may be used to produce an optical article. A method that may be used to practice the invention includes a method of making an optical fiber preform. The method includes reacting a fluorine containing precursor in a flame of a combustion burner without forming a soot, thereby forming a fluorine doping atmosphere. A further method that may be practiced to practice the invention includes the step reacting at least a fluorine containing precursor in a flame of a combustion burner, wherein the precursors reacted in the flame are substantially devoid of the element of silicon, thereby forming a fluorine containing atmosphere for the doping of a soot preform.

Abstract: The invention includes inventive methods of treating a soot preform. One method includes heating a soot preform to a temperature of less than about 1000° C. and exposing the preform to a substantially halide free reducing agent. Preferred reducing agents include carbon monoxide and sulfur dioxide. Another inventive method of treating the preform includes exposing the preform, in a furnace, to a substantially non-chlorine containing atmosphere comprising carbon monoxide. The preform is heated to a temperature of at least about 1000° C. Preferably this method is incorporated into the process for making an optical fiber. An additional method of treating the preform includes doping the preform with fluorine and exposing the fluorine doped preform to a substantially chlorine free atmosphere comprising at least carbon monoxide at a temperature of at least 1100° C., thereby reacting excess oxygen present in the furnace.

Abstract: The doped silica core region of a core rod for an optical fiber preform is protected against unwanted fluorine doping during fluorine doping of the outer silica layer by selectively consolidating the core region prior to fluorine doping. Due to dopants in the core region, the soot in the core region consolidates before the soot in the outer undoped region. This inherent property allows the entire core rod to be heated prior to fluorine doping resulting in selective partial consolidation and preventing fluorine doping of the doped center core region. The process time required may be reduced by using incremental fluorine doping. In the incremental doping process the doping step is separated into a deposit step, where “excess” fluorine is deposited on the silica particles, and a drive-in step where atomic fluorine is distributed into the silica particles. The drive-in step is conveniently combined with the sintering or consolidation step to further enhance the efficiency of the doping process.

Abstract: The present invention discloses a process for making rare earth (RE) doped optical fibre by using RE oxide coated silica nanoparticles as the precursor materia, more particularly the method of the present invention involves preparation of stable dispersions (sol) of RE oxide coated silica nanoparticles at ambient temperature and applying a thin coating on the inner surface of silica glass tube following dip coating technique or any other conventional methods, of the said silica sol containing suitable dopants selected from Ge, Al, P, etc.

Abstract: The doped silica core region of a core rod for an optical fiber preform is protected against unwanted fluorine doping during fluorine doping of the outer silica layer by selectively consolidating the core region prior to fluorine doping. Due to dopants in the core region, the soot in the core region consolidates before the soot in the outer undoped region. This inherent property allows the entire core rod to be heated prior to fluorine doping resulting in selective partial consolidation and preventing fluorine doping of the doped center core region. The process time required may be reduced by using incremental fluorine doping. In the incremental doping process the doping step is separated into a deposit step, where “excess” fluorine is deposited on the silica particles, and a drive-in step where atomic fluorine is distributed into the silica particles. The drive-in step is conveniently combined with the sintering or consolidation step to further enhance the efficiency of the doping process.

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.