Abstract: The invention relates to an optical fiber preform (20) comprising a primary preform (21) and one or more purified silica-based overclad layers (22) surrounding said primary preform (21), the purified silica-based overclad layers (22) comprising lithium and aluminium, and having a ratio between lithium concentration [Li] and aluminium concentration [Al] satisfying the following inequality: 1×10?3?[Li]/[Al]?20×10?3.

Abstract: The invention relates to an optical fiber preform (20) comprising a primary preform (21) and one or more purified silica-based overclad layers (22) surrounding said primary preform (21), the purified silica-based overclad layers (22) comprising lithium and aluminium, and having a ratio between lithium concentration [Li] and aluminium concentration [Al] satisfying the following inequality (Formula (I)). 1.103?[Li]/[Al]?20.

Abstract: The invention relates to a method for manufacturing a final optical fiber preform by overcladding, said method comprising the steps of providing a primary preform; positioning said primary preform within at least one tube, wherein the at least one tube partly covers the primary preform to create a zone to be overcladded, being an overclad zone, which overclad zone is located on the primary preform outside the at least one tube; injecting a gas into the annular space between the primary preform and the at least one tube under overpressure relative to the pressure outside the at least one tube; overcladding the primary preform in the overclad zone with an overcladding material using an overcladding device. The invention also relates to an apparatus for carrying out the method. The invention allows overcladding a primary preform at low cost while maximally limiting the incorporation of impurities into the silica overclad.

Abstract: Disclosed is a plasma torch for overcladding a primary preform of an optical fiber. The plasma torch includes a confinement tube for confining an induced plasma and a torch base. The torch base has a ceramic surface internal to the confinement tube. The plasma torch has extended life even at high input powers.

Abstract: The invention embraces a method for manufacturing an optical fiber preform. The primary preform is overcladded by projecting silica grain under a plasma torch, wherein, during overcladding, at least one region adjacent to the plasma torch is cooled by gas provided by at least one cooling nozzle. The invention facilitates low-cost preform overcladding in a way that limits the incorporation of impurities into the silica overcladding.

Abstract: Disclosed is a plasma torch for overcladding a primary preform of an optical fiber. The plasma torch includes a confinement tube for confining an induced plasma and a torch base. The torch base has a ceramic surface internal to the confinement tube. The plasma torch has extended life even at high input powers.

Abstract: The invention relates to a method for manufacturing a final optical fiber preform by overcladding, said method comprising the steps of providing a primary preform; positioning said primary preform within at least one tube, wherein the at least one tube partly covers the primary preform to create a zone to be overcladded, being an overclad zone, which overclad zone is located on the primary preform outside the at least one tube; injecting a gas into the annular space between the primary preform and the at least one tube under overpressure relative to the pressure outside the at least one tube; overcladding the primary preform in the overclad zone with an overcladding material using an overcladding device. The invention also relates to an apparatus for carrying out the method. The invention allows overcladding a primary preform at low cost while maximally limiting the incorporation of impurities into the silica overclad.

Abstract: A method of treating gaseous waste from an optical fiber preform fabrication unit containing halogenated compounds includes a step of forming a liquid effluent from the gaseous waste by condensing the gaseous waste. The gaseous waste is preferably condensed by cooling it. Plant for implementing the method includes a condenser and a container for collecting condensate. The condenser is preferably a refrigerating device. The plant can further include a soot box.

Abstract: A method of treating gaseous waste from an optical fiber preform fabrication unit containing halogenated compounds includes a step of forming a liquid effluent from the gaseous waste by condensing the gaseous waste. The gaseous waste is preferably condensed by cooling it. Plant for implementing the method includes a condenser and a container for collecting condensate. The condenser is preferably a refrigerating device. The plant can further include a soot box.

Abstract: The invention relates to a method of treating germanium-containing gaseous waste coming from a unit for manufacturing an optical fiber preform, the method comprising the following steps:a liquid effluent is formed from the gaseous waste; andthe germanium is precipitated in the liquid effluent. According to the invention, the precipitation is performed by adding magnesium MgO to the liquid effluent.