Abstract: Embodiments of the present invention are sulfur rich glass compositions comprising germanium, gallium and sulfur, which glass compositions have a low energy phonon spectrum and which glass compositions serve as a host for active materials in fabricating light sources such as fiber laser oscillators, light amplifiers, and superluminescent sources. In particular, such a laser oscillator, light amplifier or superluminescent source is comprised of an inventive glass composition which is doped with rare earth ions such as Pr.sup.3+ or Dy.sup.3+ for producing light output at wavelengths, among others, substantially at 1.3 um. Further embodiments of the present invention are light sources such as laser oscillators, light amplifiers and superluminescent sources which have emissions substantially at 1.3 um and which are comprised of an inventive glass composition which is doped with Dy.sup.3+ and Yb3+ ions, wherein Dy.sup.3+ ions are pumped by energy transfer from Yb3+ ions.

Abstract: Optical fiber composed of a glass doped with at least laser-active ions of an element from the rare earths. An optical fiber of glass, preferably a HMF glass, doped with Tm.sup.3+ is operated at 1.48 .mu.m as a fiber laser or amplifier on the laser transition .sup.3 F.sub.4 -.sup.3 H.sub.4. Since this thereby involves a self-saturating transition, the terminal level is emptied in accelerated fashion for a continuous wave mode by co-doping with de-activators, preferably Ho.sup.3+, Tb.sup.3+, Eu.sup.3+ and/or Pr.sup.3+ ions. The pump light wavelength can be selected from the wavelength range from 700 through 890 nm of GaAlAs emission. The optical fiber can be used in optical amplifiers or fiber amplifiers.

Abstract: The present invention relates to a process for the synthesis of fluoride glass by the sol-gel method.The object of the invention is to synthesize an impurity-free fluoride glass.This object is achieved with the aid of a process having stages consisting of preparing a wet oxygenated gel from precursors containing all the cations constituting said fluoride glass, hydrolyzing said gel, drying said gel and in which the process is characterized in that it also comprises the stage consisting of treating said oxygenated gel by a fluorinating agent in the vapour phase, at a temperature below the glass crystallization point.This process more particularly makes it possible to produce fluoride glass for optical fibres.

Abstract: An optically active device comprising an optical fiber, a light source and a coupler is disclosed. The optical fiber has a core made of a silicate glass containing Rb and/or Cs oxide. The core is doped with Nd.sup.3+ as an active ion and transmits light at 1.3 .mu.m band. The light source generates excitation light at 0.8 .mu.m. The coupler directs the excitation light from the light source into the core of the optical fiber. A signal light or a spontaneous light at 1.3 .mu.m band which is transmitted in the core stimulates Nd.sup.3+ to emit light at 1.3 .mu.m band. As a result an optical function such as optical amplification can be effected at 1.3 .mu.m band.

Abstract: A silica glass optical fiber superior in resistance to ultraviolet rays, which fiber comprises a doped silica glass cladding layer formed on a silica glass core, said silica glass core having an OH content of 10-1000 ppm, a fluorine content of 50-5000 ppm, and being substantially free of chlorine.

Abstract: An optical fiber having a core with a composition consisting essentially of 48 to 60 mole percent ZrF.sub.4, 15 to 25 mole percent BaF.sub.2, 1 to 5 mole percent LaF.sub.3, 1 to 5 mole percent AlF.sub.3, 15 to 22 mole percent NaF, and 1 to 8 mole percent ThF.sub.4 ; and a cladding having an index of refraction lower than that of the core. The glass of the core can be doped, for example, with rare earths. Built-in casting, rotational casting, casting around a rod, and rod-in-tube methods can be used to produce optical fibers having a composition in accordance with the present invention and having improved resistance to crystallization, as compared to ZBLAN glasses, even in the presence of rare earth dopants.

Abstract: An improved optical fiber for transmitting mid-infrared wavelength laser light in surgical instruments, includes, a heavy-metal oxide component, preferably GeO.sub.2 doped with heavier cations and anions, is capable of delivering of at least three watts of laser power continuously for more than ten minutes, without failure. This glass fiber has an .alpha.(dB/m) at 2.94.mu.m of 10, preferably less, and can transmit at least 27% of the IR through a thickness of one foot.

Abstract: Rare earth element doped silica glass according to the invention is prepared by doping silica-based glass co-doped with a rare earth element and aluminum additionally with fluorine and has excellent physical properties including remarkable light emission characteristics and an excellent capability of being fused with other silica-based glass. Such doped silica glass provides high amplification gains and a wide wavelength bandwidth and therefore can be used as a material for manufacturing miniaturized optical devices. Particularly, since the manufacturing process adapted to produce rare earth element doped silica glass according to the invention does not involve crystallization that normally characterizes the type of doped silica glass under consideration, the obtained doped silica glass is transparent and totally free from air bubbles.

Abstract: A sol-gel process for forming a germania-doped silica glass rod that is suitable for use as a preform in the manufacture of high numerical aperture optical fibers. The sol is produced by mixing together prescribed quantities of alkoxides including tetraethyl orthosilicate and tetraethyl orthogermanate, deionized water, ethanol and a precipitation catalyst such as hydrofluoric acid. Premature precipitation of germania is avoided by adding ethanol and deionized water to an alkoxide solution at a controlled, drop-wise rate and by then similarly adding the catalyst at a controlled, drop-wise rate. After drying the resulting gel, sintering is performed by chlorinating the dry gel to remove residual hydroxyl groups, then oxygenating the chlorinated gel to remove the chlorine, and finally heating the oxygenated gel in helium to a temperature of about 1300.degree. C. Chlorinating and oxygenating the gel for extended time durations, and maintaining the gel above 1200.degree. C.

Abstract: The present invention relates to an optical functioning glass containing Nd.sup.+3 as an active ion which amplifies an input light, and at least one other optical active ion different from Nd.sup.+3 which absorbs light at and near 1 .mu.m. The present invention also relates to an optical functioning glass containing Nd.sup.+3 as an active ion which amplifies the input light, and at least one other optical active ion different from Nd.sup.+3 functioning as a promoter. An efficiency of the stimulated emission of Nd.sup.3+ caused by signal light propagated through the optical functioning glass is enhanced and a gain of the light amplification at 1.3 .mu.m is increased.

Abstract: Disclosed is a method of forming a doped glass body. The glass body is formed by adding a dopant to a glass preform, at least part of which has interconnective pores. The porous preform is immersed in a solution of a salt of the dopant dissolved in an organic solvent having no OH groups. The solvent is removed, and the porous glass preform is heat treated to consolidate it into a non-porous glassy body containing the dopant dispersed throughout at least a portion of the body. An OH-free solvent is selected because of its beneficial effect on the preform during the drying step. Whereas OH-containing solvents such as water and alcohol caused cracking and/or flaking of the outer surface of the porous preform following the drying step, an undamaged surface is formed by the present invention.

Abstract: This invention is drawn to heavy metal oxide glasses exhibiting high nonlinear susceptibility and infrared transmission consisting essentially, in weight percent, of 42-48% PbO, 33-44% Bi.sub.2 O.sub.3, 10-15% Ga.sub.2 O.sub.3, and up to 15% total of at least one member of the group consisting of up to 5% SiO.sub.2 and/or GeO.sub.2 and up to 15% Tl.sub.2 O. This invention also comprehends the fabrication of light guiding fibers from those glasses.

Abstract: A method of production of mono- or multimodal lightwave guides from special substrate glasses of the glass system SiO.sub.2 -B.sub.2 O.sub.3 -Al.sub.2 O.sub.3 - K.sub.2 O-F.sup.-, with partial exchange of the Li.sup.+, Na.sup.+, and/or K.sup.+ ions present in the glass against Cs.sup.+ ions, the substrate glasses having the following compositions (in mol.-%): SiO.sub.2 45-72, B.sub.2 O.sub.3 8-25, Al.sub.2 O.sub.3 1-25, Li.sub.2 O 0-1, Na.sub.2 O 0-2, K.sub.2 O 6-18, MO 0-1 (MO= MgO, CaO, SrO, BaO, ZnO, PbO), in which a portion of the O.sup.- ions present in the glass are replaced by 1-15 mol % F.sup.- ions.

Abstract: Crystallization-resistant, low liquidus, fluoride glasses are disclosed which consist essentially of ZrF.sub.4, optionally HfF.sub.4, BaF.sub.2, at least one of CsF or NaF, preferably AlF.sub.3 and LaF.sub.3, and at least one of InF.sub.3, YF.sub.3 and GaF.sub.3. The glasses are of utility as optical components because of their high IR transmission.

Abstract: A crystal of a composition of silver, thallium, and sulfur is useful in non-linear optical devices, acousto-optical devices, piezo electric devices and other types of optical and acoustic devices. The chalcogenide glass composition of the invention displays superior transmission beyond 12 .mu.m.

Abstract: A low- or no-silica phosphate glass useful as a high average power laser medium and having a high thermal conductivity, K.sub.90.degree. C. >0.8 W/mK, and a low coefficient of thermal expansion, .alpha..sub.20.degree.-300.degree. C. <90.times.10.sup.-7 /.degree.C., consisting essentially of (on a batch composition basis):______________________________________ Mole % ______________________________________ P.sub.2 O.sub.5 45-70 Li.sub.2 O 0-14 Na.sub.2 O 0-12 K.sub.2 O 0-6 Al.sub.2 O.sub.3 9-15 Nd.sub.2 O.sub.3 0.01-6 La.sub.2 O.sub.3 0-6 SiO.sub.2 0-8 B.sub.2 O.sub.3 0-8 MgO 6-30 CaO 0-15 SrO 0-9 BaO 0-9 ZnO 0-15 .SIGMA. MgO + Li.sub.2 O 20-30 ______________________________________whereby said glass has K.sub.90.degree. C. >0.8 W/mK and .alpha..sub.20.degree.-300.degree. C. <90.times.10.sup.-7 /.degree.C. The Nd.sub.2 O.sub.3 can be replaced by other lasing species.

Abstract: A glass composition consisting essentially of the following components present in the glass in the following mole percent ranges is shown:CHART I ______________________________________ CHEMICAL COMPOSITION RANGES mole percent ______________________________________ SiO.sub.2 58-68 Al.sub.2 O.sub.3 0-2 K.sub.2 O + Rb.sub.2 O + Cs.sub.2 O 0-3 PbO 10-15 Bi.sub.2 O.sub.3 0.3-2.1 MgO + CaO + BaO 10-20.4 B.sub.2 O.sub.3 0-4 As.sub.2 O.sub.3 + Sb.sub.2 O 0.1-1.1 ______________________________________A glass composition for manufacturing a high performance microchannel plate is also shown. A microchannel plate made from a glass composition consisting essentially of components in the glass range as defined above is also shown. A method for making a non-porous glass tubing comprising a hollowed out central area and having a transformation temperature in range of about 570.degree. C. to about 610.degree. C., a liquidus temperature below 1000.degree. C.

Abstract: Production of mono- or multimodal lightwave guides from special substrate glasses of the glass system SiO.sub.2 --B.sub.2 O.sub.3 --Al.sub.2 O.sub.3 -- K.sub.2 O--F.sup.-, with partial exchange of the Li.sup.+, Na.sup.+, and/or K.sup.+ ions present in the glass against Cs.sup.+ ions, the substrate glasses having the following compositions (in mol.-%): SiO.sub.2 45-72, B.sub.2 O.sub.3 8-25, Al.sub.2 O.sub.3 1-25, Li.sub.2 O 0-1, Na.sub.2 O 0-2, K.sub.2 O 6-18, MO 0-1 (MO=MgO, CaO, SrO, BaO, ZnO, PbO), in which a portion of the O.sup.- ions present in the glass are replaced by 1-15 mol % F.sup.- ions.

Abstract: Glass compositions for high efficiency erbium.sup.3+ -doped optical fiber lasers, amplifiers and superluminescent sources are optimized for pumping by high power solid state lasers in the vicinity of 800 nm to provide amplified signals in wavelengths between 1.5 and 1.7 microns, a principal telecommunications window. A number of suitable host glasses for doping with erbium 3+ are identified wherein the excited state absorption/ground state absorption intensity ratio calculated at 800 nm is 1.00 or less.

Abstract: The invention is directed to thick film glass ceramic dielectric compositions in which the dielectric is a mixture of amorphous aluminoborosilicate glass, which upon firing forms a single phase of ceramic crystals in a matrix of amorphous remainder glass, and a ceramic additive to minimize substrate bowing.

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: Glass fibre suitable for use as the core in fibre lasers and/or amplifiers has a core which consists of a continuous glass phase and a dispersed phase of crystallites. The preferred crystallites are the oxides and phosphates of rare earth metals, e.g. Nd.sub.2 O.sub.3 and NdP.sub.5 O.sub.14. The small size concentration and distribution of the crystallites keeps the attenuation down to acceptable levels.

Abstract: Glass fiber cores having a glass composition:______________________________________ Compositional Oxide Range in wt % ______________________________________ SiO.sub.2 25-35 BaO 6-15 K.sub.2 O 1-6 Na.sub.2 O 0-4 La.sub.2 O.sub.3 0-10 Nb.sub.2 O.sub.5 4-12 PbO 10-50 TiO.sub.2 0-4.

Abstract: An inorganic, polycrystalline, ferroelectric fiber with a diameter of from about 1 micron to 1 millimeter, a porosity of less than about 40 percent, a density of at least about 60 percent of theoretical density, and a carbonaceous material content of from about 0 to about 5 percent. The fiber consists essentially of grains of which substantially 100 percent are from about 0.01 to about 5.0 microns in size; the ratio of the size of the largest grain in the fiber to the smallest grain in the fiber is no greater than about 10.

Abstract: There are disclosed fluoroborosilicate glasses that are particularly adapted to being drawn with lead silicate core glasses to produce clad glass fibers useful in forming fiber optic bundles to be incorporated in night vision equipment. The cladding glass has a refractive index not over about 1.45 and a coefficient of thermal expansion not over about 120.times.10.sup.-7 /.degree.C. The clad fiber has a numerical aperture approximating or equal to one.

Abstract: A new method for fabricating devices which include multicomponent metal halide glasses, e.g., multicomponent metal halide glass optical fibers, is disclosed. In accordance with the inventive method, a multicomponent metal halide glass body, essentially free of crystallites, is produced by cooling essentially every portion of a melt incorporated into the glass body at a quench rate which is necessarily greater than or equal to about 10 Kelvins per second (K/sec). This necessary quench rate is achieved by successively quenching relatively small portions of the melt, e.g., thin layers or droplets of melt material, having relatively small cross-sectional dimensions.

Abstract: An improved method of rapidly forming halide glass wherein the heating and cooling schedule has two phases of heating and cooling. This improved method substantially limits the loss of volatile components because of the significantly shortened interval of time at the elevated melting temperatures. The average time under heating is about 80 minutes. Cooling is as rapid as possible. The homogenization occurs above 800.degree. C. for about 20 minutes.

Abstract: There are disclosed fluoroborosilicate glasses that are particularly adapted to being drawn with lead silicate core glasses to produce clad glass fibers useful in forming fiber optic bundles to be incorporated in night vision equipment. The cladding glass has a refractive index not over about 1.45 and a coefficient of thermal expansion not over about 120.times.10.sup.-7 /.degree.C. The clad fiber has a numerical aperture approximating or equal to one.

Abstract: Ion exchangeable glass compositions containing from 50 to 90 mole percent GeO.sub.2, from 5 to 30 mole percent Al.sub.2 O.sub.3, from 3 to 30 mole percent Li.sub.2 O, up to 30 mole percent Na.sub.2 O and up to 30 mole percent K.sub.2 O are provided. In another aspect, minor amounts of anhydrous fluorides and chlorides corresponding to these oxides are added to the glass compositions to aid in water removal. Glass articles formed of the germanate glass compositions of the present invention are readily ion exchangeable when contacted with certain salts. Strengthened germanate glass articles are also provided having an inner tension region and an outer compressive surface layer which provide good mechanical strength for the formed glass article. The strengthened germanate glass articles are made using the ion exchangeable germanate glass compositions of the present invention.

Abstract: A process for treating a halide, e.g. fluoride, glass composition, characterized by contacting a melt of the composition (3) with dry oxygen (6). Oxygen, simply on contact with a fluoride glass melt, converts transition metals, e.g. from Fe(II) to Fe(III), from one stable state to another and thereby reduces loss at transmission wavelengths in optical fibre, e.g. the loss at 2.6 .mu.m attributabel to Fe(II).

Abstract: The fluoride glass of the present invention, which contains, as anions, a small amount of chlorine in addition to fluorine, has advantages such as (1) it is less liable to crystallize as compared with a fluoride glass containing no chlorine and yet shows substantially no deterioration in chemical durability and mechanical strength due to chlorine inclusion and (2) its refractive index can easily be changed by changing the addition amount of chlorine.

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 one embodiment this invention provides novel microporous inorganic oxide glass monolith structures, which have improved mechanical strength and optical transparency. An invention glass monolith is produced by a novel sol-gel process, which utilizes trioxane as an essential additive during the gellation phase, to provide a glass monolith with micropores having uniformity of size and shape.

Abstract: Reduced boron containing glass fibers are provided which have a refractive index similar to that of higher boron-containing glass fiber compositions. The glass fibers with a refractive index in the range of greater than 1.5495 to around 1.57 have in weight percent SiO.sub.2 - 55-56.5, CaO - 20-23, Al.sub.2 O.sub.3 14.5-15.5, B.sub.2 O.sub.3 - 5 to 5.8, R.sub.2 O - 1-1.5, wherein R is an alkali metal and F.sub.2 - 0.4 to 0.6. In addition, the glass fiber composition can have minor constituents such as TiO.sub.2 of up to around 0.6 weight percent and an MgO of up to around 0.3 weight percent and ferric oxide of up to around 0.3 weight percent. Basically, the glass fibers have a reduced content of both B.sub.2 O.sub.3 and CaO over standard glass fiber compositions such as E-glass and 621-glass and also has elevated amounts of alkali and of refractory constituents such as SiO.sub.2 and Al.sub.2 O.sub.3. The glass fibers are formed with an elevated temperature of 40.degree. to 50.degree. F. (22.degree.-28.degree.

Abstract: A fluoride glass comprising AlF.sub.3, ZrF.sub.4 and/or HfF.sub.4, and at least one compound selected from CaF.sub.2, SrF.sub.2 and BaF.sub.2, and a fluoride glass comprising these components and at least one additional component selected from MgF.sub.2, YF.sub.3, NaF and other like compounds have the advantages that there hardly occurs crystallization in the production thereof, and that they are excellent in chemical durability, high in surface hardness, so that they can ideally serve as glass to be used for low loss optical fiber, infrared optical fiber for thermometer, infrared laser window, etc.

Abstract: A process for treating a halide, e.g. fluoride, glass composition, characterized by contacting a melt of the composition with dry oxygen. Oxygen, simply on contact with a fluoride glass melt, converts transition metals, e.g. from Fe(II) to Fe(III), from one stable state to another and thereby reduces loss at transmission wavelengths in optical fiber, e.g. the loss at 2.7 .mu.m attributable to Fe(II).

Abstract: Optical glasses based on silica and alumina, rich in modifying metals such as silver, thallium and cesium. The exchange by cathodic migration in a melted salt bath of said modifying metals by metals such as K, Na and Li, exchange which leads to a corresponding variation of the refraction index of the glass according to a certain predetermined profile, is performed very efficiently and rapidly. Such an exchange is performed either on the finished glass or on a microporous form thereof.

Abstract: A member capable of transmitting infrared rays of 2 .mu.m or longer in wavelength, particularly of 10.6 .mu.m in wavelength, with a slight loss is provided. The member comprises a Ge-Se-Te ternary chalcogenide glass having a composition which, in a compositional diagram of the ternary chalcogenide glass falls within the region bounded by the respective straight lines connecting points A, B, C, D, and E and A in this order, which points A, B, C, D, and E indicate Ge:Se:Te molar proportions of 32:25:43, 20:6:74, 15:5:80, 15:10:75, and 22:31:47, respectively.

Abstract: Fluoroglasses, their preparation and intermediate products obtained. These glasses are characterized by containing as the forming element at least about 10% by moles of a metal fluoride or mixture of metal fluorides of the formula MF.sub.n, n being a number equal to 3 or 4, M representing a 5f transition metal when n=4 (fluoride MF.sub.4) and a 4f transition metal or yttrium when n=3 (fluoride MF.sub.3), it being understood that said glasses are free of hydrofluoric acid as the forming element.

Abstract: Pressure and temperature insensitive optical fibers are produced using a Ta.sub.2 O.sub.5 based glass composition which has a high bulk modulus and a low thermal expansion coefficient. The glass composition can function as the cladding in the optical fiber or as a protective coating which surrounds the cladding thereby protecting the fiber from fluctuations in temperature and pressure.

Abstract: Disclosed is BeF.sub.2 -based optical fiber. Such fiber can have, in addition to low loss, other advantageous properties. For instance, BeF.sub.2 -based dispersion shifted single mode fiber can have lower core-cladding index difference and larger core diameter than the corresponding SiO.sub.2 -based fiber, and BeF.sub.2 -based graded index multimode fiber can have larger bandwidth than the corresponding SiO.sub.2 -based fiber. The inventive fibers have a core and a cladding containing at least 30 mol % BeF.sub.2, and may contain up to 40 mol % of AlF.sub.3, and one or more members of the group consisting of NaF, KF, MgF.sub.2, CaF.sub.2, PbF.sub.2, PF.sub.5, and SiF.sub.4. An exemplary and currently preferred glass has nominal composition (in mol percent) 30KF-(15-x)CaF.sub.2 -xPbF.sub.2 -10AlF.sub.3 -45BeF.sub.2, with x.ltoreq.15. Single mode fibers according to the invention have minimum total dispersion in the range 1.5-2.0 .mu.m, and typically have 0.25%.ltoreq..DELTA..sub.esi .ltoreq.0.6%, and 2.5 .mu.m.

Abstract: A lead phosphate glass to which has been added indium oxide or scandium oe to improve chemical durability and provide a lead phosphate glass with good optical properties.

Abstract: An inexpensive method and composition for the manufacture of large sized, high gradient index glass using a sol-gel diffusion process in which the ions that form the metal oxides are of unequal valence.

Abstract: ThF.sub.4 --BeF.sub.2 glasses of specified composition exhibit sufficiently low high-temperature viscosity and melt stability to be useful for the fabrication of optical devices for ultraviolet or infrared light transmission. The low melt viscosity renders the glasses suitable as host materials for rare earth and transition metal dopants so that they can be used for optical devices such as lasers and optical filters.

Abstract: Optical fibers comprising core and/or cladding elements composed of MgO--Al.sub.2 O.sub.3 --SiO.sub.2 glasses are described wherein control of thermal expansion mismatch among the core and cladding elements is possible. Low-stress, high numerical aperture fibers as well as prestressed polarization-relating and high strength fibers are described.

Abstract: Process for treating molten mixtures of fluorozirconate glass to form high purity infrared transparent glass which is essentially free of zirconium fluoride disassociation impurities and anion impurities. The molten mixture or melt is treated with a moisture-free oxygen reactive atmosphere to prevent formation of disassociation impurities or to remove any of these impurities already present in the melt. The melt is also contacted simultaneously or subsequently with a fluorine species reactive gas to remove any oxygen anion impurities formed during the oxygen reactive atmosphere treatment of the melt to thereby provide a glass having complete fluorine stoichiometry and which is free of disassociation and anion impurities.

Abstract: A selenium-base chalcogenide glass for use as optical fibers suitable for transmitting with low loss infrared rays, particularly that of 10.6 .mu.m in wavelength, is provided. The infrared optical fibers with low transmission loss, which is suitable for practical use, are obtained by incorporating 2 to 100 ppm of at least one of Al Ga, and In into a selenium-base chalcogenide glass, thereby to reduce the absorption due to the vibration of Ge--O bond formed by the contamination with oxygen. The infrared optical fibers made of such a glass material show a transmission loss of 3-4 dB/m which is less than 1/2.5 of the loss (10 dB/m) of a reference glass.

Abstract: A glass suitable for use in optical fibre cores has a refractive index of 1.540-1.610, Na.sub.2 O and B.sub.2 O.sub.3 in a molar ratio of 1.05-2:1, 2-12 mole percent BaO, 40-63 mole percent SiO.sub.2, and 1.5-15 mole percent ZrO.sub.2, the proportion of SiO.sub.2 and ZrO.sub.2 together not exceeding 65 mole percent. The glass can be prepared in a highly reduced state by the use of CO and a redox buffering agent. The glass is especially suitable for the production of high numerical aperture wide cored fibres.

Abstract: Novel halide glass-forming compositions in the CdF.sub.2 -AlF.sub.3 -PbF.sub.2 and CdF.sub.2 -AlF.sub.3 -PbF.sub.2 -LiF composition fields are disclosed which exhibit unusual glass stability. The constituents of these glasses are potentially vapor transportable, so that very pure glass articles exhibiting excellent infrared transparency can be envisioned.

Abstract: A temperature-insensitive fiber comprises a lightpropagating core having ##EQU1## not in excess of 5.5.times.10.sup.-6 K.sup.-1, wherein n represents the ractive index, T represents the temperature, and .rho. represents the density of the core material, a cladding layer on the core with a Poisson ratio about equal to that of the core; a substrate layer on the cladding layer having a Young's modulus greater than that of the core, a Poisson ratio about equal to that of the core, thermal expansion co-efficient not more than one fourth of that of the core, and a thickness of at least five times greater than the radius of the core; and an elastomeric protective layer on the substrate layer.