Abstract: A glass preform for use in the fabrication of a single mode optical fiber having improved dispersion property is produced by a method comprising steps of forming a porous glass cladding body around a porous glass core body to form a porous glass preform while heating the core body to partially shrink the core body with adjusting a ratio of the shrunk part of the core body to that of the unshrunk core body at a value of 0.65 to 0.9 and then heating the porous glass preform to consolidate it to obtain a transparent glass preform. Preferably, the core body is partially heated and shrunk by a cladding forming burner.

Abstract: It realizes the chemical vapour phase deposition method using a plasma maintained by surface waves in a tube (2) for obtaining a preform and comprises photodetection means (50) sensitive to the light emitted by the deposition area (54) of the vitreous coating resulting from the reaction between appropriate gaseous compounds and able to supply information relative to the emission area of said light, and means (52) for controlling the displacement of the deposition area, displacement being such that the thickness of the coating is uniform in the tube, and control means controlling the power of the microwave generator (30) of the apparatus as a function of the information. Application to the field of telecommunications.

Abstract: An optical preform is prepared first by depositing soot about a glass subate rod (22) to form a boule. Then the soot boule is sintered to consolidate the material and provide a preform from which optical fiber is drawn. The boule is relatively large so that the resulting preform is capable of providing more optical fiber than those used in the past. In order to be able to sinter successfully the enlarged boule, microwave energy from a furnace (60) is coupled to the glass rod so that the sintering proceeds from the rod radially outwardly thereby allowing gases readily to escape and rendering the process highly efficient.

Abstract: A raw material supplying device having a gas tight tank for receiving a material to be gasified by heating; a heater for heating the raw material within the tank and a plurality of pipes for conveying a plurality of streams of gas in parallel to each other to a plurality of ports of a reaction apparatus, and a process for using the raw material supplying device. The raw material supplying device can be used in a system for manufacturing glass fibers in which the ends of the plurality of pipes are connected to the gas feed ports of at least one multi-layer burner.

Abstract: In apparatus for carrying out a method of manufacturing optical fibre preforms by causing a chemical reaction to take place in a gaseous reaction mixture so as to form a coating on a glass substrate wherein the reaction is promoted by the production of a plasma, a non-volatile component of the reaction mixture is held within a dispenser tube so that when it is evaporated by applying heat, it travels through perforations in the dispenser tube and reacts with the other components of the gaseous mixture.

Abstract: Disclosed is a method of manufacturing a preform for an asymmetric optical fiber which comprises the steps of (a) fixing plural transparent glass rods involving at least one core-mother rod functioning as the core in said optical fiber in parallel relationship, (b) depositing glass soot around an assembly of said plural parallel fixed glass rods, thereby providing a single porous cladding bearing the predetermined shape, and (c) vitrifying the porous cladding by thermal fusion, thereby providing the entirely integral transparent preform. The above method does not involve any process of perforating a drilled-pore which is needed inevitably in conventional method. Therefore, it is possible to obtain a long preform with high dimensional precision, and to fabricate the optical fiber with low transmission loss.

Abstract: An improved multimode optical fiber having substantially higher bandwidth and lower loss is made by controlling process parameters such as the volume of the silica which is deposited in each pass of a torch assembly (41) along a substrate tube (31) to form a preform tube which is collapsed to provide a preform (80) from which the optical fiber is drawn. As a result, the amplitude variation of the refractive index across each layer is controlled to be within desired limits. Should the volume of the silica deposited in each pass be controlled to control the amplitude variation, the thicknesses of the outermost deposited glassy layers in the preform tube are greater and those of the innermost layers are less than those of layers in a preform tube made by prior art MCVD processes.

Abstract: In producing a preform for an optical fiber by MCVD technology, involving the buildup of a core matrix of doped silica layers inside a glass tube with subsequent thermal collapse of the structure, a layer of dopant is deposited on the inner surface of the finished core matrix before the collapse. The thickness of this dopant layer, which advantageously is in a colloidal state, progressively diminishes along the tube axis in a direction away from an end of the tube at which the collapse begins. The law of thickness variation is chosen to maintain an internal gas pressure of vaporized dopant equal to the vapor pressure of the dopant in the core material at the collapsing temperature, in order to prevent the appearance of a paraxial dip in the refractive-index profile of an optical fiber subsequently drawn from the collapsed preform.

Abstract: A method of making a thick walled glass tube by depositing glass particles on the surface of a glass tube, sintering the particles, and drawing the resultant structure to form a capillary tube having a predetermined desired inside diameter.

Abstract: A glass soot deposition torch (30; FIG. 2) having gas passages arranged to provide an inner (34) and outer (36) flame front is disclosed in which the temperature of the inner front is higher than the outer front. A passage is located within the outer front (36) through which glass soot (32) is directed onto the surface of a growing soot-form core (38).

Abstract: An improved method for fabricating an optical fiber preform by the vapor phase axial deposition (VAD) method, comprises forming core and cladding soots at the same time by the use of core and cladding burners. The improvement is that the cladding burner is designed so that at least one of the outlets for a feed material gas, a fuel gas, an auxiliary fuel gas, and an inert gas is composed of a plurality of openings. In this improved method, the temperature distribution from the boundary of the core soot to the periphery of the cladding soot is made smooth, and thus the cladding soot is prevented from cracking.

Abstract: In order to eliminate the effect of water attack on silica optical fibres, the fibres are provided with a surface layer of silicon nitride or silicon oxynitride. The method proposed comprises direct nitridation. This may be achieved by adding a nitriding atmosphere to the drawing furnace gases, or to the reactive gases (TiCl.sub.4 and SiCl.sub.4) incorporated in the flame of an oxyhydrogen torch for the formation of a compressive silica/titania layer on an optical fibre by a glass soot deposition and sintering process.

Abstract: A preform for fabrication of a glass fiber optical transmission line is prepared by chemical reaction of vapor ingredients within a glass tube. Reaction, which may be between chlorides or hydrides of, for example, silicon and germanium with oxygen, occurs preferentially within a constantly traversing hot zone. Flow rates and temperature are sufficient to result in glass formation in the form of particulate matter on the inner surface of the tube. The particulate matter deposits on the tube and is fused with each passage of the hot zone. Continuous rotation of the tube during processing permits attainment of higher temperatures within the heated zone without distortion of the tube.

Abstract: A method for producing a glass preform for an optical fiber comprising forming a fine glass particle mass by flame hydrolysis of a glass raw material, dehydrating the fine glass particle mass in an oxygen atmosphere containing chlorine or a chlorine-containing compound at such temperature that the soot preform is not considerably shrunk and heating the soot preform at a temperature at which the soot preform is sintered and made transparent, the glass preform produced by which method contains less hydroxyl groups, structural defects and an optical fiber fabricated from said glass preform has stable light transmission characteristics for a long time.

Abstract: A method of heating a quartz glass tube with microwaves, which method comprises supplying a gas for plasma generation in the quartz glass tube, applying microwaves to the quartz glass tube so as to generate a hot plasma in the quartz glass tube and to preheat the quartz glass tube, and then discontinuing the supply of the gas for plasma generation while applying the microwaves, whereby the quartz glass tube absorbs the microwaves to heat the quartz glass tube to a sufficient temperature in a very quick and clear manner.

Abstract: In a method for supplying a glass forming raw material in a reactor which comprises bubbling a carrier gas into a liquid glass forming raw material contained in a container and supplying a mixture of the glass forming raw material and the carrier gas in the reactor, pressure of an atmosphere surrounding said container and said reactor is kept constant to supply a desired amount of the glass forming raw material to the reactor.

Abstract: Method of and arrangement for manufacturing rotationally symmetrical porous solid bodies.A method of manufacturing rotationally symmetrical porous solid bodies, in which the starting material for the solid body in the form of a suspension consisting of the material for the solid body in solid form and a liquid dispersing agent, is introduced into a hollow mould whose geometry corresponds to that of the solid body to be formed, such that during the introduction of the suspension the hollow mould is rotated about its longitudinal axis, a certain quantity of solid of the suspension being deposited on the inner wall of the hollow mould, and excess residual suspension being removed, after which the green body thus formed is subjected to further process steps to manufacture the solid body, in which process suspension is introduced into the hollow mould in such doses that each time only thin solid layers having a thickness in the range from 10.sup.

Abstract: An attenuating device 10 for use with signal carrying optical fibres 14 comprises a length 18 of optical fibre coiled within a casing 16. The optical fibre length 18 is of higher attenuation per unit length than the optical fibres 14 and the device comprises means, for example optical fibre tails 22,24 fusion spliced at 20,22 to the opposite ends of the length 18 for optically connecting those ends to the fibres 14.

Abstract: A method for producing a glass preform for an optical fiber comprising a core and a cladding containing fluorine is fisclosed. The method comprises forming a porous glass layer of substantially pure quartz on an outer surface of a fused glass rod consisting of a central portion of substantially pure quartz and a peripheral portion of quartz glass containing fluorine, and heating a composite of the fused glass rod and the porous glass layer in an atmosphere containing fluorine to add fluorine to the porous glass layer and to make it transparent, by which contamination of glass with hydroxyl groups can be prevented and light transmission characteristics of an optical fiber fabricated from the glass preform are improved.

Abstract: A method of manufacturing a glass fiber preform in which a quartz glass rod having an outer coating containing chlorine and a core doped for higher refractive index has blown thereon a soot formed by a burner fed with quartz glass raw material and a chlorine group gas undergoing flame hydrolysis. The resulting composite is the heated and fused to collapse.

Abstract: In place of the conventional rod-in-tube method, a novel method is proposed for the preparation of a high-quality base material of quartz glass for optical fibers according to which a glassy rod composed of the core portion of a larger refractive index and the first cladding layer of a smaller refractive index is first prepared by silica soot deposition by the flame hydrolysis of a gaseous silicon compound followed by dehydration and vitrification, and then the glassy rod is covered with a layer of further silica soot deposition which is subsequently converted to the second cladding layer by vitrification. The inventive base material for optical fibers is excellent in the geometry relative to the diameter of the core portion and thickness of the cladding layer as well as concentricity of the core and the cladding.

Abstract: Polarization-retaining optical fibres are manufactured according to the PCVD method, in which on the inside of a glass tube (1) and, simultaneously on at least two glass rods (2, 3) which are arranged inside the glass tube such that their longitudinal axes run parallel to the longitudinal axis of the glass tube, glass is deposited in layers and the glass rods are removed from the glass tube upon completion of the glass deposition process. Alternatively, a single glass rod, the radial dimensions of which in two mutually perpendicular directions are in a ratio unequal to one, is arranged in a glass tube such that its longitudinal axis coincides with the longitudinal axis of the glass tube.

Abstract: In order to manufacture a fiber by drawing a preform, said preform is made by collapsing a thick-walled silica tube having a reduced pressure established therein and heated in successive passes. The tube is prevented from ovalizing by beginning each pass with a portion bearing against a coaxial internal conical guide. The invention is applicable to low cost fiber manufacture.

Abstract: Two opposite portions of the surface of a core rod whose section is circular are removed by machining in the longitudinal direction thereof, so that the section of the core rod is transformed into a non-circular shape. On the surface of the thusly shaped non-circular core rod, glass particulates are accumulated, and then the glass particulates accumulated on the core rod are sintered to create a preform. Then, the preform is heated and drawn, so that a polarization-maintaining optical fiber of non-circular section is obtained.

Abstract: A method for the manufacture of a light wave guide providing a cladding and a light conducting core, from a glass tube, showing a material on or below its inner surface which forms the core of the finished light wave guide comprising at least one substance which is diffused out selectively of this material, forming the core subsequently, into the interior space of the glass tube, whereby during the diffusing-out process the partial pressure of the diffusing-out substance in the interior space of the glass tube is maintained as small as possible, whereby a premature collapsing of the glass tube during the diffusion process is prevented by adjusting an overpressure in the glass tube, that the glass tube after the diffusing out process is largely collapsed by rinsing with a rinsing gas and in a last collapsing step is completely collapsed to a rod (perform) without rinsing with a rinsing gas and that the rod is subsequently drawn out to a fiber.

Abstract: Optical fibres whose refractive index profiles show specific peripheral and/or radial and/or axial optical modulation structures are manufactured according to the PCVD method, in which such method parameters are varied which influence:(a) the uniformity of the material transport to the inner wall of the tube and/or the deposition yields of the glass over the tube circumference and/or(b) the axial position of the local deposition zone with respect to the reactor producing the plasma.

Abstract: Planar single-mode optical waveguides which can conduct light with defined polarisation have so far been embedded in, for example, a cladding made from crystalline LiNbO.sub.3. The crystalline structure of the cladding produces disadvantageous properties such as the fact that the birefringence depends on the geometric profile of the guide, relatively high optical loss, poor fibre coupling, birefringence rigidly fixed by material constants, and a costly manufacturing process. The new process results in an optical waveguide in which both the cladding and the actual guide itself are made of glass with a certain composition, thereby avoiding the disadvantages stated. With the help of a non-isothermal plasma CVD process a light-guiding core region (1) is surrounded on a substrate (4) by cladding layers (2, 2') and a cladding region (3, 3'), the thermal coefficient of longitudinal expansion of the cladding region (3, 3') differing markedly from that of the two homogeneous cladding layers (2, 2').

Abstract: A method for producing a glass preform for use in the fabrication of an optical fiber which comprises inserting a core rod made of quartz glass in a cladding tube made of quartz glass added with fluorine, heating them from the outside of the cladding tube to fuse them together to form a primary glass preform comprising a core rod and a first cladding layer around the core rod, depositing SiO.sub.2 soot particles around the primary glass preform and thermally treating the soot deposited glass preform in the presence of a fluorine-containing compound to form a final glass preform from which an optical fiber is fabricated. From the glass preform produced by this method, an optical fiber having low attenuation of light transmission in a wide range of wave-length is fabricated.

Abstract: A method of vitrifying a porous cylindrical article made out of glass soot, especially for manufacturing a preliminary blank for optical fibers. The article is heat-treated in a furnace in a vacuum or in an atmosphere that contains helium. The porous article is placed in a horizontal graphite tube in the furnace, is sintered therein for 20 to 40 minutes in a vacuum or in a helium atmosphere with reduced pressure at 1250.degree. to 1400.degree. C., and is subsequently vitrified by heat-treating the sintered article at first in the sintering atmosphere, while slowly rotating it in the hot graphite tube for 20 to 40 minutes at approximately 1450.degree. to 1600.degree. C. and then while rotating it in the graphite tube more rapidly than in the first stage for 10 to 30 minutes at approximately 1650.degree. to 1750.degree. C.

Abstract: Incorporation of fluorine into a porous silica body, such as an unsintered body produced by a sol-gel method, by VAD or OVPO, reduces or eliminates bubble or pore formation upon re-heating of the glass formed by sintering of the porous material. Effective fluorine concentrations are between 0.01 and 5% by weight. The invention can be used advantageously in producing preforms and optical fiber.

Abstract: Disclosed is a method of manufacturing a preform for an asymmetric optical fiber which comprises the steps of (a) fixing plural transparent glass rods involving at least one core-mother rod functioning as the core in said optical fiber in parallel relationship, (b) depositing glass soot around an assembly of said plural parallel fixed glass rods, thereby providing a single porous cladding bearing the predetermined shape, and (c) vitrifying the porous cladding by thermal fusion, thereby providing the entirely integral transparent preform. The above method does not involve any process of perforating a drilled-pore which is needed inevitably in conventional method. Therefore, it is possible to obtain a long preform with high dimensional precision, and to fabricate the optical fiber with low transmission loss.

Abstract: A method of fabricating an optical fiber base material which comprises the steps of sequentially accumulating glass made of doped quartz on the inner peripheral surface of a quartz tube to form glass layers, and then forming by heating means the interior of the tube in a solid state, temporarily thermally shrinking the tube when the accumulating step of the glass layers approaches the final period, then again accumulating glass on the inner periphery of the resultant glass layer and then forming the interior of the tube in a solid state. Thus, this method can reduce the center-dip without loss of the controllability of a refractive index distribution.

Abstract: It has been discovered that fused silica doped with approximately equimolar amounts of Al and P, has advantageous properties that make such co-doped glass useful in a variety of applications, including optical fiber, especially polarization-maintaining optical fiber, and planar waveguides in optical and optoelectronic devices. In particular, such co-doped fused silica can have a refractive index that is lower than, or at least not significantly greater than, that of pure fused silica, even though both Al and P individually are known up-dopants for silica. The co-doped fused silica also can have a relatively low working temperature, while otherwise maintaining many of the desirable properties of fused silica, e.g., chemical inertness and relatively low coefficient of thermal expansion.

Abstract: An optical fiber having an intense polarization plane maintenability is constructed of an optical waveguide having a circular core and a circular cladding, a jacket formed on the outer circumference of the optical waveguide and having an elliptical outer circumference, and a supporting portion formed on the jacket.In order to fabricate the above-specified optical fiber, a preformed rod therefor is prepared by forming the inner wall of an silica glass tube with the jacket and the optical waveguide made of such materials as satisfy a relationship of c.sub.2 /a.gtoreq.200/(100-.gamma.)-1, wherein: letter .gamma. stands for the ellipticity of the outer circumference of the aforementioned jacket; letter c.sub.2 stands for the minor axis of an ellipse; and letter a stands for the radius of the circular optical waveguide, and by subsequently collapsing the aforementioned silica glass tube while having its internal pressure made lower than the atmospheric pressure by 1 to 20 mmH.sub.2 O.

Abstract: A chemical vapor deposition method which utilizes a rare earth chelate vapor as a source of rare earth ions for producing an optical fiber having a core with a high rare earth content.

Abstract: A burner for producing glass fine particles provided with an intermediate passage between a central passage and an outer passage for surrounding the periphery of the central passage characterized by that the end of the intermediate passage is disposed inner side from the end of the outer passage and the end of the central passage is disposed between the end of the intermediate passage and the end of the outer passage. Thus, the burner can stably fabricate porous glass base material having GI type or triangular refractive index distribution and yet can suppress the production of bubbles.

Abstract: A glass preform for use in the fabrication of a dispersion shifted single mode optical fiber is produced by a method for comprising steps of inserting a core member consisting of an inner core part made of a germanium-added quartz glass which optionally contains fluorine and an outer core part made of a quartz glass having a refractive index smaller than that of the inner core part in a glass tube made of a fluorine-added quartz glass having a refractive index smaller than that of the outer core part, heating the core member and the glass tube to collapse the glass tube and fuse them together to produce a glass perform. The glass preform comprises a core member consisting of an inner core part made of GeO.sub.2 -SiO.sub.2 glass or GeO.sub.2 -F-SiO.sub.2 glass and an outer core part made of F-SiO.sub.2 glass and a cladding made of F-SiO.sub.2 glass and provides a dispersion shifted single mode optical fiber having reduced attenuation of light transmission in the 1.5 .mu.m wavelength band.

Abstract: The method consists of diffusing a doping compound in the region of a fluorozirconate glass support, wherein the optical guide is to be fabricated. The remaining regions are suitably masked to avoid any possible ionic exchange.

Abstract: In order to prevent an uncontrolled collapse of a quartz tube whose inner surface is being coated with a vitrifiable substance in making a preform or parison of an optical fiber, one or more streams of carrier gas entraining the ingredients of the coating substance through the quartz tube are supplemented by a stream of supplemental carrier gas whose flow is being continuously controlled to keep the overall mass-flow rate substantially constant. The outer tube diameter is photoelectrically monitored and incipient changes thereof are compensated by controlling a flow of additional carrier or inert gas which does not pass through the tube but joins the traversing gas flow at the tube outlet, inside a solids separator with a restricted exit aperture, to modify the pressure differential across the tube wall.

Abstract: An apparatus for fabricating an optical fiber preform having a support for rotatably holding a reaction tube, a raw material supply unit for supplying a glass raw material from one end of the reaction tube to the interior of the reaction tube and a heater for heating the reaction tube by reciprocating in the axial direction of the reaction tube which comprises a pressure measuring unit at the other end of the reaction tube, a gas pressure control chamber having a gas inlet and an exhaust port, and a blower capable of controlling the introduced gas pressure according to the measured value of the pressure memasuring unit in the gas inlet. Thus, the apparatus can accurately control the internal pressure of a reaction tube in good responsiveness.

Abstract: A glass body having a graded (substantially Gaussian) index profile is produced by a process that comprises providing a doped porous body (e.g., having a uniform dopant distribution), heat treating the porous body in a halogen-containing atmosphere, and consolidating the porous body into the glass body. The heat treatment removes a predetermined portion of the dopant from the porous body, such that the radial dopant profile in the glass body differs from the initial profile in the porous body, and such that the Gaussian index profile results. Exemplarily, the porous body is a uniformly germania-doped, VAD-produced, high-silica rod having radially decreasing density, and the heat treatment comprises an 8-hour densification soak at 1300.degree. C. in 20% Cl, 80% He. In a preferred embodiment, silica overcladding is deposited on a graded index core rod produced according to the invention, and fiber drawn from the resulting composite glass body.

Abstract: A method for producing a glass preform for optical fibers in which fluorine is efficiently incorporated into the preform without incorporation of Fe or Cu. A fine glass particle mass, made primarily of quartz, is converted into transparent glass by heating it in a gas atmosphere containing at least a fluorine-based compound gas and a chlorine-based compound gas. The preferred heating range is 1,100.degree. to 1,400.degree. C.

Abstract: A method is disclosed for making a step-index optical fiber having a steep refractive index gradient between core and cladding. Core glass particles comprising a base glass and a refractive index-increasing dopant are deposited on a mandrel. The mandrel is removed and the resultant soot preform is consolidated to form a core preform having a dopant-poor surface region. The core glass preform is stretched and the hole therein is closed to form a core bait rod. Cladding glass soot is deposited on the core bait rod at a density which is at least 0.5 g/cc. This is accomplished by directing the flame from an auxiliary burner onto the core bait rod immediately prior to the deposition of cladding soot thereon. The resultant preform is consolidated and drawn into an optical fiber. In another embodiment, the etched core preform is overclad with a layer of cladding glass, and the composite preform is stretched prior to applying a second overclad layer.

Abstract: A quartz optical fiber comprising a core having a higher refractive index and made of pure quartz containing fluorine and phosphorus pentoxide and a cladding having a lower refractive index, a weight ratio of fluorine and phosphorus pentoxide in the core being larger than 1 (one), which is substantially free from unstability of the glass structure.

Abstract: A method for producing an optical fiber preform comprising jetting a glass raw material mixture containing at least one phosphorous compound and a fuel gas through a burner, hydrolyzing the raw materials in the flame to form fine glass particles, depositing the fine glass particles to form a porous glass preform, and then sintering the porous glass preform in a stream of an inert gas with removing phosphorus liberated from the preform to produce a transparent optical fiber preform, from which transparent optical fiber preform, an optical fiber having low attenuation at a wavelength of about 1.52 micrometer is produced.

Abstract: A low loss fiber optic coupler is fabricated by forming a coupler preform having a plurality of spaced glass cores extending longitudinally through a matrix of glass having a refractive index lower than that of the cores. The preform is heated and stretched to form a glass rod which is then severed into a plurality of units. Heat is applied to the central region of each unit while the ends of the unit are pulled apart to elongate and taper inwardly the heated central region, whereby the cores of the unit are more closely spaced and are of smaller diameter at the central region than they are at the ends of the unit. The unit is then provided with a plurality of optical fibers, one of which extends from each of the cores at the endfaces of the unit. A preferred method of providing the optical fibers involves forming the coupler preform of a matrix glass that is easily dissolved in a solvent.

Abstract: Rare earth elements, e.g. Nd, are introduced into optical glass fibre for telecommunications by evaporating a suitable salt, e.g. NdCl.sub.3, from a glass sponge into the gas stream used to deposit core material. Preferred sponges are in the form of tubes having an outer impervious layer and an inner porous layer. These sponges are conveniently made by MCVD and the impregnation is preferably carried out using an alcoholic solution of the impregnant.

Abstract: An improved process for the production of optical fiber porous preforms of predetermined refractive index distribution by the vapor-phase deposition method is disclosed wherein a glass material and a dopant material are subjected to flame oxidation by the use of an oxyhydrogen burner to form fine glass particles which are deposited on one end of a supporting rod adapted to move apart from the oxyhydrogen burner while rotating to allow a rod-like porous preform to grow thereon. The improved process is characterized in that the correlation between the shape of the deposition face and the refractive index distribution is previously determined mathematically, and on a basis of the correlation therebetween, a process variable such as the distance between the porous preform and the burner is adjusted to produce the desired shape of the deposition face whereby there can be obtained an optimum refractive index distribution.

Abstract: While collapsing the central duct in hollow glass optical fiber preforms, an etchant consisting of a mixture of oxygen and a fluorocarbon compound from the group C.sub.2 F.sub.6, C.sub.3 F.sub.8 and N-C.sub.4 F.sub.10 is passed through the duct. In particular, the etchant is passed through the duct only when the duct's diameter is 1 mm or smaller. The resulting solid preforms and optical fibers drawn therefrom do not have a central dip in the refractive index profile.

Abstract: A method for producing ultra-high purity, optical quality, glass articles is disclosed which involves: (1) forming a gel from a silicon-containing organic compound, such as, TEOS; (2) drying the gel to produce granules having a mean particle size of less than about 1 millimeter; (3) fully sintering the granules to produce high purity, artificial sand; (4) casting the artificial sand by conventional techniques, such as, slip casting, to form a high density, porous, green body; (5) drying and partially sintering the green body; (6) fully sintering the green body under vacuum; and (7) hot isostatic pressing ("hipping") the green body. The glass articles produced by the process have higher purity, greater homogeneity, and less IR absorption than existing, commercially available, premium quality, fused silica, glass articles.