Abstract:
An optical fiber with large effective area, low bending loss and low attenuation. The optical fiber includes a core, an inner cladding region, and an outer cladding region. The core region includes a spatially uniform updopant to minimize low Rayleigh scattering and a relative refractive index and radius configured to provide large effective area. The inner cladding region features a large trench volume to minimize bending loss. The core may be doped with Cl and the inner cladding region may be doped with F.
Abstract:
This invention relates to a device for removing a powdery substance accumulating in a tubular back portion (2) of an optical fiber preform (1) during the manufacture thereof, comprising a screw structure (3) following the inner surface of said tubular back portion (2). In order to provide an efficient removal structure which does not affect the preform mechanically or in any other way, the screw structure (3) according to the invention comprises a gas conduit (4) provided with orifices (5) opening towards the open end of the tubular back portion (2). Preferably the structure is a pipe (3) wound in the form of a spiral.
Abstract:
Methods for recycling a low permeability gas such as krypton in the consolidation process of optical fiber manufacturing. The low permeability gas is sent to a purification unit or plant before being reutilized in the consolidation process. The low permeability gas can be used to produce holes or voids in a cladding region of an optical fiber preform. Upon drawing the optical preform into an optical fiber, the voids become elongated in the direction of draw.
Abstract:
A method is disclosed for recovering germanium from a gaseous mixture which includes a germanium-containing compound in vapor or particulate form, acid in vapor form, and water vapor. The gaseous mixture is contacted with a liquid containing water under conditions effective to dissolve the germanium-containing compound in the liquid. The acidity of the resulting liquid mixture is increased under conditions effective to vaporize the germanium-containing compound. The vaporized germanium-containing compound is contacted with one or more aqueous solutions under conditions effective to dissolve and precipitate the germanium-containing compound in at least one of the one or more aqueous solutions, and the resulting precipitate is separated from the at least one of the one or more aqueous solutions. The methods described herein are particularly well suited for recovering germanium from the waste gases produced during optical waveguide manufacturing processes. Germanium recovered by this method can thereafter be used in the production of semiconductors, optical waveguide fibers and optical components.
Abstract:
The invention relates to a method for treating gaseous discharges which stem from a unit manufacturing an optical-fibre preform and contain germanium. Said method consists of the following steps: preparation of a liquid effluent from the gaseous discharges, followed by precipitation of the germanium in the liquid effluent. According to the invention precipitation is carried out by the addition of magnesium oxide MgO to the liquid effluent.
Abstract:
Process of recovering a constituent of a process effluent, such as an effluent of a process for making a preform from which an optical fiber is drawn. The effluent is directed into a scrubber (40) of a loop (20) where it is treated with an aqueous solution to provide a solvent mixture which comprises particulates and a solvent solution including the constituent, e.g., germanium. Subsequently, the solvent mixture is moved into a first filter system (55) which provides a filtrate free of particulates above a first size that is returned to the scrubber for reuse and a residue. Then the residue from the first filter system is moved into a second filter system (80) which provides a filtrate free of particulates larger than a second size that is smaller than the first size and a residue. The filtrate from the second filter system also is returned to the scrubber for reuse while the residue from the second filter system is recirculated therethrough. When the constituent, e.g., germanium, concentration reaches a predetermined level, portions of the residue from the second filter system are withdrawn and subsequently treated with a precipitating agent to recover the constituent, e.g., germanium.