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 welding one end of a primary preform and one end of a silica bar having different properties. The method includes the steps of projecting and fusing silica grain under a plasma torch onto an end of the primary preform and an end of the silica bar, and bringing into contact these respective ends to form an excellent weld between the primary preform and the silica bar. The invention provides a cost-effective way to secure a primary preform to a glass-working lathe support while reducing the risk of costly preform breakage.

Abstract: Method for overcladding an optical fiber preform with a given target diameter (D0) of the final preform includes providing a primary preform to be overcladded, and successively depositing first overcladding layers by projecting and vitrifying silica particles on the primary preform moving in relative translation with a plasma torch. Each first overcladding layer has a given uniform thickness (d) and is deposited at a given, constant silica particle flow rate and at a given, constant translation speed. The method also includes the detection of a preform diameter (D1) greater than a given threshold (S) and the deposition of a final overcladding layer having the remaining required thickness (D0?D1) at a constant silica particle flow rate and at a reduced translation speed. The inventive method enables a preform to be overcladded efficiently with improved yield and high quality.

Abstract: Disclosed is an optical transmission fiber having reduced bending and microbending losses that is commercially usable in FTTH or FTTC transmission systems.

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 an optical transmission fiber having reduced bending and microbending losses that is commercially usable in FTTH or FTTC transmission systems.

Abstract: Disclosed is an optical transmission fiber having reduced bending and microbending losses that is commercially usable in FTTH or FTTC transmission systems.

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: Disclosed is an optical transmission fiber having reduced bending and microbending losses that is commercially usable in FTTH or FTTC transmission systems.

Abstract: Disclosed is an optical transmission fiber having reduced bending and microbending losses that is commercially usable in FTTH or FTTC transmission systems.

Abstract: The invention relates to a method for welding one end of a primary preform and one end of a silica bar having different properties. The method includes the steps of projecting and fusing silica grain under a plasma torch onto an end of the primary preform and an end of the silica bar, and bringing into contact these respective ends to form an excellent weld between the primary preform and the silica bar. The invention provides a cost-effective way to secure a primary preform to a glass-working lathe support while reducing the risk of costly preform breakage.

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: Method for overcladding an optical fiber preform with a given target diameter (D0) of the final preform includes providing a primary preform to be overcladded, and successively depositing first overcladding layers by projecting and vitrifying silica particles on the primary preform moving in relative translation with a plasma torch. Each first overcladding layer has a given uniform thickness (d) and is deposited at a given, constant silica particle flow rate and at a given, constant translation speed. The method also includes the detection of a preform diameter (D1) greater than a given threshold (S) and the deposition of a final overcladding layer having the remaining required thickness (D0?D1) at a constant silica particle flow rate and at a reduced translation speed. The inventive method enables a preform to be overcladded efficiently with improved yield and high quality.

Abstract: Disclosed is an optical transmission fiber having reduced bending and microbending losses that is commercially usable in FTTH or FTTC transmission systems.

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 for producing an optical fiber preform (100) consists in producing a primary preform (110); drawing out an end portion (115) of the primary preform (110) to produce a tail portion (115); thickening (120) the primary preform; and forming a cone (130) on the drawn out tail portion at the end of the primary preform. As a result of drawing out an end portion of the primary preform, the amount of primary preform required for cone formation is reduced while simultaneously optimizing cone length and angle appropriate to good initiation of fiber drawing.

Abstract: A method of manufacturing a preform, the method comprising rotating a primary preform about an axis X, establishing relative displacement in translation between the preform and a plasma torch, and introducing a glass powder into the plasma flame, the glass powder being accelerated prior to penetrating into the plasma flame by an accelerator gas introduced into the flow of glass powder, said process being performed in an enclosure and said introduction being performed into an atmosphere at a regulated pressure lower than the pressure outside the enclosure. Apparatus for manufacturing the preform comprises an enclosure connected to a unit for regulating the pressure inside the enclosure.

Abstract: A method of manufacturing a preform, the method comprising rotating a primary preform about an axis X, establishing relative displacement in translation between the preform and a plasma torch, and introducing a glass powder into the plasma flame, the glass powder being accelerated prior to penetrating into the plasma flame by an accelerator gas introduced into the flow of glass powder, said process being performed in an enclosure and said introduction being performed into an atmosphere at a regulated pressure lower than the pressure outside the enclosure. Apparatus for manufacturing the preform comprises an enclosure connected to a unit for regulating the pressure inside the enclosure.