Abstract: A process is described for making silica powder by a sol-gel process whereby an aqueous suspension is made of a silica-based raw material which includes particles containing chlorine, the pH of the suspension is adjusted to a value from 3 to 4.5 if necessary, the suspension is gelled, the gel obtained is dried and the dried gel is fractionated into silica granules. The silica-based raw material preferably includes particles containing chlorine having a specific surface area less than 80 m2/g and less than 5 wt. % relative to the total quantity of particles containing chlorine of silica particles having a specific surface area from 150 m2/g to 300 m2/g. The use of such powder to manufacture an optical fiber preform is also described.

Abstract: There is disclosed a method of constructing photosensitive waveguides on silicon wafers through the utilization of a Plasma Enhanced Vapor Deposition (PECVD) system. The deposition is utilized to vary the refractive index of resulting structures when they have been subject to Ultra Violet (UV) post processing.

Abstract: A method for shaping an end of an optical fiber having a core to provide a novel optical fiber (or waveguide) includes the steps of contacting the fiber against a mold having a predetermined shape, The fiber and/or mold is heated. The fibers can be made of silica. The method is well suited for making wedge-shaped (i.e., standard screwdriver-like shaped) fiber tips. In addition, an apparatus for molding a shaped tip precisely located with respect to a core of an optical fiber includes a mold having one or more surfaces of the mold being configured and dimensioned to impart a predetermined shape to an end of an optical fiber contacted therewith, the predetermined shape being precisely located with respect to the core of the optical fiber.

Abstract: An improved process for fabricating a refractory dielectric article, in particular silica optical fiber, is provided. The fabrication process involves joining of two elongated bodies—typically silica preforms—end-to-end by use of an isothermal plasma torch technique. A long preform made in this manner allows drawing of optical fiber with less down-time and waste than current processes. The plasma torch technique also produces low perturbations within the resultant preform, thereby increasing the amount of usable fiber.

Abstract: The present invention relates to a rod-shaped preform for manufacturing an optical fibre therefrom, as well as to a method for manufacturing such a rod-shaped preform. The present invention furthermore relates to a method for manufacturing an optical fibre, wherein one end of a rod-shaped preform is subjected to a heat treatment, after which the thus softened end of the rod-shaped preform is subjected to a pulling force for the purpose of drawing an optical fibre therefrom.

Abstract: The invention relates to a method of manufacturing a cylindrical preform for use in making an optical fiber of substantially smaller diameter. The method consists in increasing the diameter of a primary preform by injecting grains onto the surface of the primary preform and in fixing the grains on the surface by means of a heat flow obtained by a plasma torch comprising a tube made of refractory material, and an inductor surrounding the tube. The distance between the inductor and the end of the tube is reduced when the diameter of the preform increases. The temperature of the outside surface is thus increased, thereby enabling preforms to be obtained of larger diameter or with improved efficiency.

Abstract: The deposit of natural or synthetic silica comprises a preform (1) set into rotation (7) in front of a plasma torch (3) which moves back and forth substantially parallel to a longitudinal direction (L) of the preform (1), a feed duct (9) for feeding the plasma with grains of natural or synthetic silica (11), characterized in that the same feed duct (9) feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas (15). Sodium or lithium contained in the grains of natural or synthetic silica reacts with the fluorine or chlorine of the fluorine or chlorine compound, making it possible to improve the optical quality of fibers built up with the natural or synthetic silica at reduced cost.

Abstract: An apparatus and method for producing a tubular member, which is suitable for use as a starter tube or an optical fiber preform, on a rotating cylindrical target mounted on a lathe. The tubular member is made by means of plasma outside vapor deposition. In this process, a source gas comprising SiCl4 and, optionally, a fluorine-laden chemical, is introduced into an air plasma. Both the air and the source gas are dry gases and have low hydroxyl content. The air plasma is created by a high-frequency induction plasma torch which travels along the length of the target on a carriage. The torch is provided with a short U-shaped gutter on either side of its rim directly beneath the target and the growing tubular member. This gutter helps channel reaction products of the source gas and the plasma so as to enhance deposition on the growing tubular member.

Abstract: Natural or synthetic silica is deposited on a preform set into rotation in front of a plasma torch which moves back and forth substantially parallel to a longitudinal direction of the preform, a first feed duct feeds the plasma with grains of natural or synthetic silica while a second feed duct feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas Any sodium or lithium contained in the grains of natural or synthetic silica react with the fluorine or chlorine of the fluorine or chlorine compound, thereby making it possible to improve the optical quality of fibers drawn from a preform built up with natural or synthetic silica, and to do so at reduced cost.

Abstract: A method and associated apparatus for increasing the over cladding rate in perform production while maintaining the integrity of the glass quality of the cladding. The method and apparatus are designed to utilize the full capacity of the generator to thereby improve the overall deposition speed without sacrificing the glass quality. In particular, it is estimated that the process of the present invention will increase the deposition speed by approximately 50% and still obtain suitable glass quality. This object is achieved by utilizing two plasma torches, instead of just one, that are driven by the same power generator.

Abstract: The invention relates to manufacturing glass fiber preforms. It relates to a method comprising rotating preform about its own axis, and displacing a plasma torch in translation relative to the preform in a direction parallel to the axis of the preform, the axes of the flame and of the preform and being offset by a certain distance, and then inserting glass powder into the plasma flame under gravity. According to the invention, the glass powder is accelerated before penetrating into the plasma flame by means of an accelerator gas, and the offset distance between the axes is reduced with increasing acceleration of the powder. The invention is applicable to manufacturing glass fibers, and in particular optical fibers.

Abstract: Disclosed is an optical waveguide fiber having a compressive outer layer that includes TiO2 in the SiO2 matrix glass. The compressive outer layer includes crystalline structures containing TiO2 that are predominately rutile. Also disclosed is a method for making an optical waveguide fiber having a compressive outer layer. The compressive outer layer can contain an additional metal oxide that is preferentially lost from the outer layer, instead of the TiO2, during the drying and consolidation step.

Abstract: The invention relates to a method of assembling two optical fiber preforms together end-to-end, the method comprising the following operations: the two cylindrical preforms are placed in alignment along a common longitudinal axis; the preforms are rotated about the common longitudinal axis; the facing ends of said preforms are heated by a heater; and the preforms are moved towards each other parallel to the common axis to press them against each other so as to form intimate contact between the ends after cooling. According to the invention, the heating is performed by causing the preforms or heater to move in a radial direction orthogonal to the common longitudinal axis in such a manner as to heat the peripheries and then the cores of said preforms.

Abstract: The present invention relates to a method of fabricating optical devices and in particular to a method of fabricating integrated opto-electronic devices, and to an opto-electronic device. A plasma enhanced chemical vapor deposition process (PECVD) is used to deposit an optical device integrated in silicon onto an electronic device fabricated in silicon. Relatively low temperatures are utilized and, in order to reduce losses of a waveguide in the optical device in the wavelength range 1.50 to 1.53 .mu.m, the deposition process is carried out in the absence of nitrogen. An optical device is disclosed which comprises an integrated construction incorporating an optical waveguide in silica and a photonic transducer in silicon.

Abstract: The present invention is directed at a method and device for manufacturing a preform. The method involves arranging a starting body within a channel as defined by a vessel. Then, the channel is supplied with a reactive gas containing a coating material precursor. A resonator then generates a plasma zone within the channel. The starting body is aligned in the channel such that the plasma zone concentrically surrounds the starting body. The axial movement of the resonator relative to the starting body is controlled such that a desired layer of coating material precursor reactively deposits on the starting body to form the preform. The method suppresses deposition on the inside of the vessel via suppressing means, which may involve inducing nodes in the E-field at the vessel walls, or using an suppressing gas on the inner surface of the vessel, or a combination of the two. The present invention is also directed at a device to facilitate the aforementioned method.

Abstract: A singlemode optical fiber 700 having very low loss at 1385 nm, and a practical method for making same are disclosed. A core rod 20 is fabricated using vapor axial deposition to have a deposited cladding/core ratio (D/d) that is less than 7.5. The core rod is dehydrated in a chlorine- or fluorine-containing atmosphere at about 1200.degree. C. to reduce the amount of OH present to less than 0.8 parts per billion by weight, and then consolidated in a helium atmosphere at about 1500.degree. C. to convert the porous soot body into a glass. The consolidated core rod is elongated using an oxygen-hydrogen torch that creates a layer of OH ions on the surface of the rod that are largely removed by plasma etching. Finally, the core rod is installed in a glass tube 40 having a suitably low OH content. Thereafter, the tube is collapsed onto the rod to create a preform 60. Conventional methods are employed for drawing an optical fiber from the preform and applying one or more protective coatings 75, 76.

Abstract: A method of manufacturing a silica powder using a sol-gel technique, wherein a suspension consisting of synthetic silica soot, having a specific surface area of less than 80 m.sup.2 /g, is made in water to form a concentration of 50% to 75% by weight of silica; the suspension is gelled; the resulting gel is dried without forming a crust and with microwaves and broken up into silica grains having an apparent density of 0.5 g/cm.sup.3 to 0.6 g/cm.sup.3 ; and screening of the dry gel is performed to provide grains having a desired size.

Abstract: A planar waveguide structure has, supported on a lower refractive index buffer layer (5), a pair of optical cores (1, 2) that, over at least a portion of their length, are closely spaced. These cores are covered with a layer (6) of cladding material comprising boron and phosphorus doped silica glass deposited by PECVD as a succession of individually annealed layers in order to minimize the incidence of voids in the deposit between the cores.

Abstract: The smoothness of refractory dielectric bodies, particularly silica sol-gel bodies, is substantially improved by a relatively straightforward treatment. In particular, the surface of the body is treated with a plasma fireball, such as induced by a plasma torch. The treatment is able to reduce the roughness, as measured by RA, in overcladding tubes formed by a sol-gel process by at least a factor of 2, typically at least a factor of 5. It is also possible to improve the smoothness of silica tubes that are drawn from a billet. Typically, the process reduces the roughness of silica bodies to an RA of about 1 microinch or less.

Abstract: An apparatus for producing an optical fiber porous glass preform using the VAD method which can stably produce a high quality optical fiber porous glass preform, wherein a target bar is only rotatably supported by a chuck and is not pulled upward, a lower tip of a soot body is detected by a laser and a photodetector, and a core burner and a cladding burner is lowered in response to the result detected. A tip position detecting drive and burners are synchronizingly lowered while the deposit of porous glass grows at the lower portion of the target bar.

Abstract: The invention concerns a process for preparing glass, more specifically glass powder or glass films, together with a process for conditioning the raw materials intended for preparing glass characterized in that raw materials are converted to freely flowing powder suitable for feeding to a plasma torch in which the powder is converted to glass.

Abstract: A refractory dielectric body is heated with a plasma fireball at conditions which do not result in substantial removal of a surface portion of the body, yet which are sufficient to reduce both surface and bulk impurities. Typically, the body is treated with the plasma in the absence of simultaneous deposition of material onto the body. Advantageously, an isothermal, oxygen or oxygen-containing plasma is utilized. The invention is useful for reducing chlorine impurities by at least about 30% to a depth of at least about 10 .mu.m, with accompanying reduction of hydroxyl impurities. The invention thus provides a useful method for reducing the concentration of impurities that contribute to imperfections during the process of drawing fiber from an optical fiber preform, without requiring substantial removal of the surface of the preform.

Abstract: Annealing a planar wave guide layer is critical because small structural imperfections lead to optical problems. Chemical vapor deposition of the layer tends to leave gaseous substances bonded to the deposit, which on being driven off by initial annealing warm-ups leave cavities requiring densification. Traditional annealing methods take several hours. This invention proposes a rapid heating of the layer to a temperature below the flow temperature, maintaining this temperature for about 30 to 300 seconds, then rapidly heating up further to a temperature close to or above the flow temperature, maintaining this temperature for about 30 to 300 seconds, then allowing the substrate and layer to cool rapidly to room temperature.

Abstract: The method of manufacturing a preform having a supporting core by effecting successive passes with a plasma torch while material is being supplied, and by effecting at least one glazing step with the plasma torch and without material being supplied includes:a) a first glazing step effected at slow speed from a first end of the preform to the second end thereof;b) pre-separation of the preform adjacent to the first end, thereby reducing its diameter to substantially that of the supporting core;c) a second glazing step effected from the first end to the second end of the preform; andd) complete separation of the preform at the place of pre-separation.

Abstract: The invention relates to a method of performing surface treatment on a preform manufactured in an installation for manufacturing or building up preforms having supporting cores, the installation including at least rotation means having a horizontal axis of rotation and two mounting points between which the supporting core of the preform to be manufactured or built up is mounted, plasma-torch and material-supply means disposed radially relative to the supporting core and mounted to move in axial translation relative to and parallel to the supporting core so as to make the preform around the supporting core, the preform being manufactured or built up by effecting successive passes with the plasma torch while material is being supplied.

Abstract: In a drawing method and drawing apparatus according to the present invention, a forward end portion of an optical fiber glass preform is heated and melted while the glass preform is fed into a drawing furnace 3 so that an optical fiber is drawn, and the optical fiber glass preform is heated in a position just above the drawing furnace to make the surface of the glass preform clean.

Abstract: A refractory dielectric body is heated with a plasma torch at conditions which do not result in substantial removal of a surface portion of the body, yet which are sufficient to reduce both surface and bulk impurities. Typically, the body is solid, e.g., a rod as opposed to a tube, and is treated with the plasma in the absence of simultaneous deposition of material onto the body. Advantageously, an isothermal plasma torch is utilized, and the torch advantageously produces an oxygen or oxygen-containing plasma. The invention is useful for reducing chlorine impurities by at least about 30% to a depth of at least about 10 .mu.m, with accompanying reduction of hydroxyl impurities. The invention thus provides a useful method for reducing the concentration of impurities that contribute to imperfections during the process of drawing fiber from an optical fiber preform, without requiring substantial removal of the surface of the preform.

Abstract: An optical fiber formed from a glass preform substantially free of OH impurities is disclosed. The optical fiber is made to be free of OH impurities by a method having the steps of introducing a moving stream of vapor mixture including at least one compound glass-forming precursor together with an oxidizing medium into a tube, while generating a hydrogen-fee isothermal plasma on an outer surface of the tube to react the mixture and produce a glassy deposit on an inner surface of the tube. The glass preform is drawn to produce the optical fiber.

Abstract: In accordance with the invention, an optical fiber is made by the steps of providing an optical fiber preform having a longitudinal axis, rotating the preform about the axis, directing onto the preform a plasma torch which is reciprocated over a limited region parallel to the axis to define a heated region, and drawing a fiber from the heated region. Apparatus for making optical fiber comprises a rotatable mount for securing one end of a preform and rotating it about a vertical axis, a plasma torch for heating a drawing region on the preform, a positioning stage for moving the torch parallel to the vertical axis in a reciprocating manner, and a fiber drawing apparatus for drawing a fiber from the heated region of the preform.

Abstract: To enable surface tension forces to confer upon an optical fiber end (P1), a shape procuring good optical coupling the end is partially melted in an electric arc (ZC). To improve the reproducibility of this shape movement into the arc is achieved by a unidirectional sideways displacement (MC) of the fiber at an angle to the optical fiber axis. The invention applies to coupling a flat array of optical fibers to a strip of components such as semiconductor lasers. To this end the fibers (F1, . . . , F6) are fixed into grooves on a fiber support (2). The latter is displaced to dip the fiber ends simultaneously into a chemical etching bath which gives them a pointed shape and then to move them successively into the electric arc.

Abstract: In accordance with the invention, a plurality of elongated refractory bodies are laminated together by placing the bodies in close adjacency, exposing the adjacent bodies to a plasma torch heat source, and moving the bodies longitudinal past the torch at a nonzero average rate which includes a reciprocating (e.g., oscillatory) component to longitudinally spread the zone of heating. Where the bodies are a rod to be laminated within a hollow tube, it is advantageous to reduce the air pressure between the rod and tube, thereby eliminating potential contaminants and, at the same time, biasing the tube to collapse against the rod. This method is particularly useful in laminating overcladding tubes to core rods to form optical fiber preforms.

Abstract: A process for forming film structure using Flame Hydrolysis Deposition (FHD) in which (1) glass soot is deposited on a substrate via FHD to form a first porous vitreous layer having a first bulk density, (2) a second porous vitreous layer having a second bulk density that is larger than the first bulk density is formed from a portion of the first porous vitreous layer, and (3) a third porous vitreous layer having a third bulk density is formed by depositing glass soot containing a refractive index increasing dopant on the second porous vitreous layer by FHD. The first, second and third porous vitreous layers are then heated to form an undercladding layer and a core layer, the undercladding layer being formed from the first and second porous vitreous layers and the core layer being formed from the third porous vitreous layer.

Abstract: A method of using a plasma to build up an optical fiber preform consists in injecting hydroxyl ions in a controlled manner into the build-up silica that is deposited on the preform. The invention is applicable to the manufacture of optical fibers, in particular monomode fibers.

Abstract: A method for making a glass preform substantially free of OH impurities is disclosed. The method comprises the steps of introducing a moving stream of a vapor mixture including at least one compound glass-forming precursor together with an oxidizing medium into a tube, while generating a hydrogen-free isothermal plasma on an outer surface of the tube to react the mixture and produce a glassy deposit on an inner surface of the tube. The method uses a plasma torch or a radio frequency furnace.

Abstract: A method for producing an optical fibre which has been treated with titanium dioxide to improve its corrosion resistance includes stretching an assembly consisting of an outer sleeve having engaged therein a bar which is partially or entirely made of synthetic silica. When treating said fibre, the outside of the coupling sleeve is coated, prior to assembling the components, with a deposit of vitrified synthetic silica containing titanium dioxide.