Abstract: A method and apparartus for setting the orientation of an optical fibre (6) having at least one planar section extending along its length comprises a light source (3) for generating a beam of light which impinges on the fibre (6). Light reflected by the fibre is detected by a light detector (5) and the fibre is rotated by means of a tube (1) into which it is inserted while the intensity of the detected light is monitored. When the intensity becomes a maximum then the planar face is facing in a known direction.

Abstract: Disclosed is a method of forming a glass preform from core and cladding glasses having low liquidus viscosities and narrow working ranges. A tube of liquid core glass is vertically situated in a vessel of liquid cladding glass. The tube extends to the bottom of the vessel where there is a stopper for preventing leakage of core glass. While both core and cladding glasses are at a temperature just above the liquidus temperature, the vessel is lowered into a coolant bath, thereby causing core glass to flow into the region vacated by the tube. The rate of withdrawing the tube from the vessel is sufficiently slow to provide laminar flow and yet fast enough to permit the resultant liquid core/clad composite to freeze before mixing occurs.

Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal aperture extending therethrough. Protective coating is removed from a region of a first optical fiber intermediate the ends thereof. Protective coating is removed from an end region of at least one other optical fiber. The coated portion of the first fiber is threaded through the tube until the uncoated region thereof is near the tube end. The size of the aperture is insufficient for simultaneously receiving the coated portions of the first and second fibers in side-by-side relationship at the coated portion of both. The uncoated region of the second fiber is placed adjacent that of the first fiber, and both uncoated regions are simultaneously fed into the tube aperture.

Abstract: A method of producing an optical multi-fibre cable element provided with a secondary sheathing by extruding (1) a loose secondary sheathing (10) around a fibre bundle (9) and providing the fibres with a desired extra length with respect to the secondary sheathing. To avoid variation in fibre length in the production of cable elements the secondary sheathing (10) together with the fibre bundle (9) is twisted (12) around its axis after the extrusion step (1) at least to such an extent that the longitudinal sliding of the fibres with respect to each other is prevented in the twisted fibre bundle and that the stretching of the fibres in the fibre bundle at the step of providing the extra length (3; 18) is kept within the elastic range of the fibres.

Abstract: Disclosed is a method and apparatus for drawing an elongated glass article such as a fiber optic device. The article is drawn upwardly from a source through the surface of a quantity of molten metal having a vertical temperature gradient. The source can be an elongated solid glass preform that is vertically positioned within the molten metal such that the temperature of that portion of the molten metal adjacent the upper end region is sufficiently high to heat that region to drawing temperature. The upper end region is pulled to form a tapered root, continued pulling resulting in the formation of an elongated article from the small diameter root end. The relative position of the root is maintained with respect to the surface of the molten metal during the drawing operation. Alternatively, the glass can be drawn from an orifice located within the molten metal.

Abstract: An optical fiber (1) has an endface (2) which has been coated with a metal oxide coating (5) such that the light guiding core region (4) of the endface (2) is at least partially bounded by the coating (5) while being uncoated itself. The core region (4) has a different reflectivity than that of the boundary region (3). The fiber may be used in a system for aligning a fiber with an optical device (20).

Abstract: A method of producing glass bodies having regions with different optical refraction, including a basic body and a coating layer which is sintered onto the basic body, covers the basic body at least partially and is made of glass, which as it is doped, has an index of refraction differing from that of the glass of the basic body. The starting material for producing the cladding on the basis of pulverulent ceramic material is deformed into a self-supporting, unsintered porous green body, is dried and submitted to a cleaning procedure in a heated gas phase. The coating layer to be bonded onto the basic body is melted into glass in a subsequent combined doping/sintering procedure in a gas phase containing the doping agent at a temperature in the range from 1150.degree. to 1500.degree. C. and is sintered onto the basic body.

Abstract: The invention relates to lenses, prisms or other optical members which are subjected to high-power ultraviolet light having a wavelength of about 360 nm or less, or ionizing radiation, particularly optical members for use in laser exposure apparatus for lithography, and to blanks for such optical members. The homogeneity of the refractive index distribution and the resistance to optical deterioration when the optical members are exposed for a long period of time to short wavelength ultraviolet light from a laser beam are improved. The optical members are made of high-purity synthetic silica glass material containing at least about 50 wt. ppm of OH groups, and are doped with hydrogen.

Abstract: The present invention provides a diffraction limited, high numerical aperture (fast) cylindrical microlens. The method for making the microlens is adaptable to produce a cylindrical lens that has almost any shape on its optical surfaces. The cylindrical lens may have a shape, such as elliptical or hyperbolic, designed to transform some particular given input light distribution into some desired output light distribution. In the method, the desired shape is first formed in a glass preform. Then, the preform is heated to the minimum drawing temperature and a fiber is drawn from it. The cross-sectional shape of the fiber bears a direct relation to the shape of the preform from which it was drawn. During the drawing process, the surfaces become optically smooth due to fire polishing. The present invention has many applications, such as integrated optics, optical detectors and laser diodes.

Abstract: Defect-free fluoride glass materials are made by hot isostatic pressing (HIP) of a fluoride glass. The process may be used to manufacture preforms or bulk fluoride glass. The external pressure applied during HIP squeezes bubbles from the glass and permits the use of a wider range of working temperatures than ordinarily available, thereby reducing crystallization defects.

Abstract: A method disclosure for making an economical fiber coupler including providing a glass tube having first and second end portions and a midregion, and a longitudinal aperture extending through it. Two suitably prepared glass optical fibers, each having a core and cladding, are disposed within the longitudinal aperture, the fibers extending beyond each end of the tube. The fibers are glued to each end portion. The midregion of the tube is evacuated, heated, collapsed about the fibers, and drawn to reduce the diameter of the resulting composite.

Abstract: Methods and apparatus are shown for cladding grown single crystal optical fibers. Neodymium YAG fibers are clad with a high index glass, either melted around the fiber in a trough or extruded over the fiber surface. Lithium niobate fibers are clad through an impregnation process. The lithium niobate fiber is first coated with magnesium oxide and then heated to a temperature and for a time sufficient for the magnesium oxide dopant material to diffuse into the fiber. The dopant lowers the intrinsic refractive indices of the fiber material around its circumference, creating a cladding region around the fiber core. Single crystal fibers clad by these methods and combined with suitable pumping means or with deposited electrodes provide low-loss single mode optical components useful for amplification, electro-optical effects and acousto-optical effects.

Abstract: A method for producing an optical multiple fiber unit wherein a multiplicity of optical fibers are fused together with each other and each optical fiber has a core made of pure silica glass and a cladding layer made of silica glass containing a dopant and disposed on the core, by bundling a multiplicity of preforms corresponding to the optical fibers and drawing the bundle at a high temperture using the optical fiber preforms, preforms having a three-layer construction wherein a support layer made of a silica glass having a drawable temperture of at least 1,800.degree. C. is further disposed on the cladding layer, and drawing the bundle of the preforms to give a multiple fiber wherein the support layer of each optical fiber has a thickness of 0.01 to 1 .mu.m, in order to produce a multiple fiber in which the cladding layer of each optical fiber has a sufficient thickness to fulfill the function as a cladding layer and which has an excellent image-transmitting capacity.

Abstract: An optical fibre of the single-mode type in which light travels in one polarization mode is formed from a single-mode quadruple-clad fibre, in which the dimension of the light-transmitting part of the fibre in a first direction perpendicular to the axis of the fibre differs from the dimension of the light-transmitting part in a second direction perpendicular to the axis of the fibre and the first direction.

Abstract: An optical fiber is provided with a vitreous carbon coating by the pyrolysis of propadiene promoted by the retained heat of the fiber immediately after it has been drawn from preform.

Abstract: Reproducible doped optical fiber preforms having a predetermined dopant concentration level are fabricated by inserting a doped filament into a completed preform prior to consolidation and final collapse so that the filament and dopant materials are centrally located in the core region upon formation of the preform. Doped fiber is drawn from the doped preform using standard fiber drawing techniques.

Abstract: For producing a fiberoptic waveguide preforms by plasma pulse-induced chemical vapor deposition (PICVD), blank glass tubes are prepared having a continuously increasing internal diameter in the direction of gas flow. This type of blank compensates for the otherwise occurring decrease in the density of the layer-forming molecules due to pressure drop, thereby permitting the formation of a uniform masswise deposition of layer-forming molecules along the length of the tube. This permits the production of collapsed preforms having a series of coating layers of substantially uniform thickness.

Abstract: Improved fluoride glass optical fibers are produced by a process introducing several improvements in the production of fluoride glass preforms and the drawing of fibers therefrom. Reduced bubble formation and crystallization are obtained by vertically spinning a fluoride glass melt within a glass cladding tube at a high rotational speed, or alternatively, pouring a flouride glass core melt into a cladding tube while slowly raising the mold from an inclined position to a vertical position, or alternatively, introducing a core tube inside a cladding tube. The production of fibers is enhanced if at least one production phase, i.e., preform formation or fiber drawing, is conducted in an atmosphere containing reactive gases that scavenge molecules that could otherwise react with, hydrolyze and oxidize the fluoride glass. The disclosure also describes several devices uniquely useful in the process of the present invention.

Abstract: A method for producing a glass preform for use in the fabrication of an optical fiber, including the steps of forming a glass soot preform from a glass-forming raw material and heating the soot preform to vitrify it, the soot preform being heated in an atmosphere comprising SiF.sub.4 under pressure higher than 1 atm. for a period of time sufficient to add fluorine, between the formation of the soot preform and the vitrification of it, fluorine being added at a high rate and in a large amount.

Abstract: A granular body, from which an article having a nonuniform refractive index may be formed, has grains of two substances which have different refractive indicies in a geometric distribution in the granular body corresponding to the geometric distribution of the substances required for the nonuniform refractive index of the article and a way of shape-stabilizing the granular body. A method of making the granular body comprises controllably feeding the grains into the geometric distribution in the granular body and shape-stabilizing it. Preferably the granular body is compressed into a porous compact which holds itself together and is treated with a gas to achieve desired optic properties in the article.

Abstract: A liquid cooling method and apparatus for rapid cooling of a hot glass fiber. In FIG. 1, an open ended liquid coolant container (12) is provided at its lower end with an inverted funnel surface (34). A vertically running, hot glass fiber (42) of indefinite length is continuously drawn through the container, as the container continuously receives a coolant liquid at its upper open end (30). The liquid continuously drains from the container lower open end (32) by flowing along flow surface (36) of the inverted funnel (34), downwardly and away from the glass fiber (42). The temperature of the fiber relative to the temperature of the coolant liquid is such that a vapor barrier surrounding the hot fiber is formed due to boiling of the liquid in a zone surrounding the fiber. This vapor zone facilitates diversion of the liquid (change in direction of flow) from the vertical to an angle thereto, along the inverted funnel surface.

Abstract: The present invention relates to a process for producing a glass doped with dispersed microcrystallites, said process comprises:a first step of cooling a glas melt comprising a component to become a glass matrix and a component to become microcrystallites dispersed in said matrix, to a temperature T which is not higher than the flow point of the glass but not lower than the sag point of the glass, anda second step of maintaining the cooled glass at the temperature T to precipitate microcrytallites in the matrix.The glass doped with dispersed microcrystallites produced is used as a material for sharp cut filter, a material for infrared-transmitting filter, a nonlinear optical material, etc.

Abstract: A sintered elongated core made of a ceramic type superconductive material consisting essentially of (R.sub.x Ba.sub.(1-x)).sub.3 Cu.sub.2 O.sub.z in which R is Sc, Y La, Ho, Dy or Eu; x is in the range of from 0.3 to 0.8; and z is in the range of from 6 yo 7, is encased in glass and then heated, stretched and drawn.

Abstract: A preform for preparation of optical fibers is prepared by inserting a rod of a higher index of refraction fluoride glass into the bore of a hollow cylinder of a lower index of refraction fluoride glass fiber. This preform precursor is processed to collapse the hollow cylinder inwardly to form a composite preform having a high-refractive index core and a low-refractive index casing. The preparing of the glasses and processing to a preform are accomplished in a reactive environment that reacts and removes oxygen and hydrogen containing species from the glass, the reactive environment being, for example, Cl.sub.2, CCl.sub.4, SF.sub.6, BF.sub.3, CF.sub.4, or the decomposition products of a liquefied solid fluorocarbon. The preform is then drawn to an optical fiber.

Abstract: A process for manufacturing an optical fiber includes the steps of heating and drawing material from a hot optical fiber preform; depositing a conductive coating (especially carbon) on the moving optical fiber; putting a heat curable liquid material on the moving optical fiber; and curing the heat curable liquid material by inductively heating the conductive coating on the moving optical fiber in an electromagnetic field. Heat induced into the conductive coating by energy from the field is conducted from the conductive coating to the heat curable material. The optical fiber continuously moves through the steps of the process without any physical contact.

Abstract: A fiber optic coupler is formed by assembling a coupler preform having two concentric glass tubes having a gap between them. The shape and/or size of the inner tube relative to the shape and/or size of the outer tube is such that a plurality of output optical fibers can be equally spaced in the gap. An input optical fiber is disposed in an aperture in the inner tube. The input and output fibers extend through the midregion of the resultant coupler preform. The midregion is heated to collapse it about the fibers, and the central portion of the midregion is stretched to reduce the diameter over a predetermined length.

Abstract: A single-mode optical fiber is doped to achieve a number of desired properties and have a refractive index profile n(r). The doped fiber must at least approximate the formula: ##EQU1## in which n.sub.o means the refractive index of the matrix material and r.sub.i =i.multidot..DELTA.r. A process for the production of the single-mode optical fiber is disclosed using at least 100 layers.

Abstract: A process for manufacturing an optical fiber includes the steps of heating and drawing material from a hot optical fiber preform; exposing the hot optical fiber to a compound containing carbon for depositing a carbon coating on the moving optical fiber; measuring an electrical property of the carbon coating; and in response to the measured electrical property, changing a parameter of the process for controlling a characteristic of the carbon coating on the moving optical fiber. Featured within the manufacturing method is a method for measuring the thickness of the carbon coating on the moving optical fiber. From the measured thickness of the carbon coating, a control signal is generated for changing one or more of the process parameters for depositing the carbon coating on the optical fiber from a precursor gas. The coated optical fiber continuously moves through the process without any physical contact. No interruption of the production process occurs.

Abstract: Apparatus for fabricating a fused biconical taper fibre optic coupler includes a hollow furnace (12) having a longitudinal slot (50). Clamp units (14, 16) are provided to hold at least two suitably prepared optical fibres (8, 9) in intimate side-by-side contact. The clamp units are moveable by motors (18, 20) to relatively laterally move the fibres into and out of the furnace (12) through the slot (50). A power supply (60) heats the furnace (12) to in turn heat segments of the fibres therein while these segments are in intimate side-by-side contact to a temperature sufficient to cause the fibre segments to fuse together. Drawings devices (22, 24) associated with the clamp units (14, 16) longitudinally draw the heated fibres while in the hot furnace to cause each fused fibre to develop a biconical taper and so form a coupler.

Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal aperture. Glass optical fibers, each having a core, cladding and coating are disposed within the longitudinal aperture, the fibers extending beyond each end of the tube. The coating is removed from that portion of the fibers in the midregion of the tube but remains on that portion of the fibers extending into the ends of the apertures. The aperture is formed by a plurality of flattened walls, the dimensions and orientations of which are such that the cross-section of the aperture in the central region of the tube is symmetrical with respect to a plane passing through the longitudinal axis of the tube. At any cross-section of the aperture that is adjacent the coated regions of the fibers, each fiber coating contacts two walls of the aperture. The fibers are held taut to effect a tension, and the midregion of the tube is heated, collapsed about the fibers, and drawn to reduce the diameter thereof over a predetermined length.

Abstract: Method of splicing optical fibres having a glass core and at least one plastics cladding layer comprises: stripping the or each cladding layer from the fibre ends, fusion splicing the bare fibre ends, placing the splice region in an open channel of a flexible mould, the channel being of uniform section, filling the gap between the bare, splice region and the inner wall of the channel with a curable plastics material, closing the flexible mould so that the channel walls close together and assume an internal shape complementary to that of the cladding layer or layers whereby to expel the surplus plastics material, curing the plastics material remaining within the mould, and opening the mould.

Abstract: In the manufacture of coated optical fiber, fiber (21) is drawn from a preform (22) and coated with one or preferably two layers (42,44) of light curable coating materials. Afterwards, the coating materials are cured. Increases in manufacturing line speed may be achieved if the cure speed of the coating materials is increased. This is accomplished by the simultaneous application of a magnetic field during irradiation of the curable coating materials to enhance the crosslinking of the coating materials by a free radical polymerization mechanism. Upon absorption of light, a photoinitiator in each composition cleaves to produce two free radical fragments in the spin paired or singlet state. The magnetic field has the effect of enhancing the production of spin parallel radicals which enhances the polymerization initiation of the coating material, thereby allowing an increase in the manufacturing line speed through drawing and coating apparatus.

Abstract: To attain high strength optical glass fibers, the glass preforms, from which the fibers are drawn, must generally be free of surface imperfections such as bubbles, and air lines. It has been discovered that these imperfections can be removed quickly and cleanly by contacting the preform surface with a substantial portion of the electrically conducting plasma region (the plasma fireball) extending from a plasma torch. Significantly, the surface material is substantially removed by vaporization, due to the extremely high plasma temperature (>9000.degree. C. at the plasma center) of the isothermal plasma torch. Though the temperatures in the tail of the plasma fireball are substantially less than at the plasma center, the temperatures are generally still several thousand degrees centigrade.

Abstract: In a method for the production of cylindrically symmetric bodies with given radial gradient of the material properties, for example of the refractive index, at least two rod-shaped molded bodies consisting of materials with different properties are joined in parallel and, following lowering of the viscosity of both materials, the bodies are twisted many times in a spiral around a longitudinal axis, such that a desired radial gradient of the material properties arises, where metallic, semiconducting, or insulating materials may be used, and the viscosity is varied through changing the temperature or adding or removing a solvent.

Abstract: An overclad fiber optic coupler is formed from a coupler preform including a glass tube having a longitudinal aperture. The aperture is formed of a plurality of similarly shaped side walls, each of which includes a longitudinally extending, inwardly projecting protrusions. The region between each two adjacent protrusions constitutes a corner region. Disposed within the aperture are at least a portion of each of a plurality of glass optical fibers, one fiber being situated in each corner region. The midregion of the tube is collapsed onto the fibers, the protrusions maintaining the fibers in their relative positions. At least a portion of the midregion is stretched to reduce the tube midregion diameter.

Abstract: A fiber optic coupler is formed by providing a glass tube having a longitudinal extending aperture. Protective coating is removed from a region of a first optical fiber intermediate the end. Protective coating is removed from an end region of at least one other optical fiber. The coated portion of the first fiber is threaded through the tube until the uncoated region is near the tube end. The uncoated region of the second fiber is placed adjacent that of the first fiber, and both uncoated regions are simultaneously fed into the tube aperture. The threading operation is continued until the uncoated regions extend through the midregion of the tube, the midregion is heated to collapse it about the fibers, and the central portion of the midregion is drawn to reduce the diameter along a predetermined length.

Abstract: A crystalline metal halide optical fiber having a two or a three layer structure is provided. The core consists of relatively small crystals. A crust surrounds the core and has the same composition but consists of relatively large crystals. Optionally, an optical outer crust surrounds the inner crust and has a different composition from the inner crust but has generally the same sized crystals. The differing crystal sizes can be produced from a preform by extruding a crystal at a low uniform temperature at a relatively high speed.

Abstract: A method of providing a preform for a polarization-maintaining optical fiber, starting from a basic preform (1) having two orthogonal planes of symmetry intersecting along its axis, and mechanically applying two discrete preformed oblong elements (15) of silica doped with boron oxide on the outside face of said basic preform symmetrically about the first plane (20), and two oblong elements of silica doped with titanium oxide on the outside face of said basic preform and symmetrically about the second plane (30). The shapes of the basic preform and the four oblong elements are selected to define a substantially solid cylinder.

Abstract: Optical fibre contains a colloidal semiconductor dispersed in the core or the cladding or both. The fibre may have active regions in which the semiconductor is dispersed and passive regions in which the semiconductor is dissolved. This is obtained by drawing a preform to get fibre in which the semiconductor is dispersed and selected portions (or else the whole fibre) are treated to precipitate the semiconductor in colloidal form.

Abstract: A method for consolidating a green body is disclosed which involves: (1) drying and partially sintering the green body at a temperature above about 1000.degree. C. and in an atmosphere containing chlorine; (2) fully sintering the green body under vacuum at a temperature above about 1720.degree. C.; and (3) hot isostatic pressing ("hipping") the green body at a temperature above about 1150.degree. C. and at a pressure above about 100 psig. The process produces glass articles which have a low water content and are essentially bubble free.This is a continuation of co-pending application Ser. No. 07/271,709 filed Nov. 16, 1988, now abandoned which is a divisional application of application Ser. No. 07/052,619, filed May 20, 1987 now U.S. Pat. No. 4,789,389.

Abstract: In accordance with the invention, the functions of two TV cameras in the prior art for monitoring polymer coating concentricity and/or carbon coating thickness are accomplished by a single TV camera (48). Rather than being projected onto an opaque dispersive screen, the forward-scattered mode pattern of each of the orthogonal beams (57,58) is transmitted through a translucent screen (52,53) and reflected to an image combining device (67) which transmits both patterns to the single TV camera (48). The two beams are slightly vertically displaced to establish displaced images (72,73) of the two patterns. This allows the two patterns to be viewed simultaneously and distinguished by the TV camera. Modified electronics (FIG. 10) provide for alternate TV scanning of the two images so that a computer (22) can monitor and correct concentricity and/or carbon coating thickness in real time during fiber production.

Abstract: A mist is formed by an ultrasonic generator (5) from a liquid solution containing a dopant, and the mist is inserted into the tube blank to be doped (4) by means of a flexible pipe (2) in order to deposit microdrops on the inside surface of said tube blank. The flexible pipe is withdrawn progressively so that deposition takes place along the entire length of the tube blank. The deposit is dried and a new layer of glass is deposited thereon. The dopant from the deposit is heat diffused into the glass of the tube blank and of the new layer of glass. The invention is particularly applicable to fabricaitng rare-earth-doped silica preforms for the purpose of drawing optical fibers that can be used to constitute lasers or sensors.

Abstract: A proton-exchange method of forming optical waveguides within a lithium-based optical substrate is disclosed which utilizes sulfuric acid as the proton source. The substrate is masked to expose the areas desired to be transformed into waveguiding regions and immersed in a heated sulfuric acid bath for a period of time sufficient to provide the exchange between the protons in the acid and the lithium in the substrate. The presence of the protons in the substrate results in increasing the extraordinary refractive index .DELTA.n.sub.e in the unmasked area so that optical guiding may be accomplished. Upon removal of the substrate from the sulfuric acid bath, the substrate must be annealed so as to drive the protons to a depth sufficient to provide effective guiding.

Abstract: The optical fibre to be protected is dipped into a bath of molten metal which solidifies on contact with the fibre and forms the desired sleeve. The fibre passses through dies immersed into the bath and of which the spacing is adjustable so as to vary the distance along which the fibre is in contact with the molten metal and, consequently, the thickness of the sleeve.

Abstract: The guiding layers of optical waveguides are formed of arsenosilicate glass (ASG). By varying the arsenic content from 2 to 13 mole percent it is possible to vary the refractive index in the range 1.45 to 1.53. Pure silica or less heavily doped ASG can be used for the cladding layers. The ASG is preferably formed as the result of a heterogeneous reaction between silane and oxygen in the presence of arsine. Such a reaction can be carried out at temperatures down to 390.degree. C., allowing the ASG to be used on substrates of III-V compounds.

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: 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: Non-oxide or heavy metal fluoride glass optical fiber with or without a cladding and coated with an outer layer of an oxide glass having a glass transition temperature of less than 400.degree. C. and a thermal expansion coefficient of less than about 19.times.10.sup.-6.C.sup.-1. Also, a method of making and providing such coatings on non-oxide or fluoride glass, and fiber optic products prepared by such methods.

Abstract: A method of making a polarization retaining single-mode (PRSM) optical fiber coupler. A section of coating is stripped from the central portion of two PRSM optical fibers. The fibers extend through the bore of a glass tube, the stripped portions being centered in the tube, and the coating portions extending into the ends of the bore. In one embodiment, each fiber is provided with a rectangularly shaped coating, and the two larger flattened sides of the coating are specifically oriented with respect to the major and minor axes of the PRSM fiber therein. The fiber coating can be disposed in only one orientation in the rectangularly-shaped tube bore, thereby properly orienting the two PRSM fibers with respect to each other. In another embodiment, the PRSM fibers are disposed within a single coating, the azimuthal inhomogenity of one fiber being aligned in the coating with respect to that of the remaining fibers.

Abstract: This invention concerns with a process and apparatus for fabricating microlenses on optical fibers. A pulsed laser beam and an end portion of a fiber are arranged relative to each to another so that the laser beam is incident on the end portion of the fiber at an acute angle .theta. to the longitudinal axis of the fiber. The angle is selected to attain a desired curvature of a lens formed by ablation and heating of the end portion of the fiber by the laser beam. A movement of the fiber and the laser relative each to another results in progressive engagement of the end portion of the fiber with the laser for a preselected distance so as to produce a short taper with a lens at the end thereof. In the preferred embodiment, the fiber rotated about its axis within a passage of the holder which moves the end-portion of the fiber into and through the laser beam resulting in the said lens. The precise repeatability of the lens formation may be controlled by a computer.