Abstract: The method allows surface defect reduction in silica optical-fibers by enriching the external layer by silica bonded carbon atoms within the silica lattice: SiC.SiO.sub.2. Carbon is obtained from chemical reaction directly during the drawing step. Volume defects are reduced by rapidly cooling the fiber structure heated up to vitreous transition temperature.

Abstract: The method of fabricating alumina-doped silica fibers allows the production of silica and dopant with reactions between gaseous chemical compounds. Alumina is obtained from a reaction between oxygen and a low-temperature vaporizable organometallic compound. The optical fibers produced do not present the refraction-index dip and exhibit low attenuation.

Abstract: The process of manufacturing optical fibers of extremely low loss in the medium infrared permits the fabrication of glass preforms having as basic materials metal-fluorides obtained from vapor-phase reactants.

Abstract: The apparatus allows the continuous production of optical fibres (15) starting from liquid-phase reactants. They are injected into a pressurized vertical vessel (3), comprising a second coaxial vessel (4), which can be vertically displaced for the variations of the refractive-index profile. The first vessel supplies material for the cladding, the second for the fibre core.Suitable furnaces (6,9,14) help the reaction and allow preform sintering and drawing.

Abstract: The process allows a uniform layer of glass particles, forming the preform, to be deposited on the internal wall of a supporting tube rotated around its axis. A suitable relationship is provided to determine the temperature distribution in the deposition zone. The apparatus makes use of different types of heat sources for generating inside the tube a temperature with the distribution required by the process.

Abstract: Vapor deposition of doped silica in a reaction chamber on a rotating supporting surface, in the manufacture of a preform for the drawing of an optical fiber, is accompanied by the continuous admixture of deuterium with a flow of carrier gas, specifically oxygen, by which the reactants are transported to the reaction chamber. An isotopic substitution of deuterium for the hydrogen of hydroxyl groups in the reaction products shifts the major absorption peaks to wavelengths outside the minimum-attenuation range of 0.7 to 1.6.mu. used for fiber-optical signaling. The proper ratio of deuterium to carrier gas is maintained with the aid of a mixer having two compartments separated by a perforated diaphragm or a thin metallic foil, one compartment being connected to a deuterium tank while the other communicates with a conduit through which the vapors entrained by the carrier gas pass to the reaction chamber.

Abstract: A nozzle used in the coating of optical fibers with a protective resin layer comprises an aluminum body split into two symmetrical halves with cavities which upon assembly form a frustoconical funnel terminating at its narrower lower end in a coaxially converging outlet port. The cavities are machined in solid aluminum blocks whereupon each block is anodized in sulfuric acid to form thereon an abrasion-resistant oxide layer with few, small pores which may be sealed by an aftertreatment in hot de-ionized water.

Abstract: In order to produce a preform or parison from which an optical fiber can be drawn, a vitrifiable substance such as silicon chloride and a doping agent such as germanium chloride, for example, are fed in liquid form and at room temperature to a spray nozzle together with water or steam for continuous deposition on a relatively rotating and axially reciprocating inner or outer surface of a cylindrical support until that surface is covered with a heavy layer of as yet unvitrified hydrated silica admixed with the doping agent in proportions designed to provide a selected refractive-index profile. The resulting preform, after degassing and separation from the support if necessary, is freed from occluded water molecules by exposure to a flow of hot dehydrating gas which may contain anhydrous compounds and is thereafter collapsed into a solid rod and completely vitrified at high temperatures.

Abstract: In order to improve the transmission characteristics of optical fibers drawn from the preforms manufactured by vapor deposition of silica on an inner wall surface of a supporting tube of glass, the tube is subjected to a two-stage heat treatment with deuterium whereby OH.sup.- groups at least on the inner tube surface are isotopically replaced by OD.sup.- groups. This pretreatment can be carried out in the same apparatus which is subsequently used for producing the preform.