Abstract: The invention relates to a plasma chemical vapor deposition (PCVD) apparatus for deposition of one or more layers of silica onto an interior wall of an elongated hollow glass substrate tube. The apparatus comprises a microwave generator, a plasma generator receiving microwaves from said generator in use, a cylindrical cavity extending through said generator, and a cylindrical liner positioned in the cavity. The substrate tube passes through the liner in use. The cylindrical liner has at least one section having a reduced inner diameter over a part of the length of the liner, the at least one section providing a contact zone for the substrate tube. The microwave generator is configured to generate microwaves having a wavelength Lw in the range of 40 to 400 millimeters, wherein a length of said at least one section having the reduced inner diameter is at most 0.1×Lw.

Abstract: The present invention relates to a method for manufacturing a primary preform for optical fibers by means of an internal plasma chemical vapor deposition (PCVD) process in a hollow silica substrate tube, the hollow substrate tube having a supply side and a discharge side. An exemplary method comprises depositing doped or non-doped silica layers on the inner surface of the hollow substrate tube by supplying glass-forming gasses to the interior of the hollow substrate tube via the supply side thereof, and by creating a plasma reaction zone in the interior of the hollow substrate tube by means of microwave radiation having a microwave power, wherein the microwave power is decreased during the depositing. The present invention further relates to a method for forming an optical fiber and to the primary preform and optical fiber directly obtainable by such methods.

Abstract: The invention relates to a plasma chemical vapor deposition (PCVD) apparatus for deposition of one or more layers of silica onto an interior wall of an elongated hollow glass substrate tube. The apparatus comprises a microwave generator, a plasma generator receiving microwaves from said generator in use, a cylindrical cavity extending through said generator, and a cylindrical liner positioned in the cavity. The substrate tube passes through the liner in use. The cylindrical liner has at least one section having a reduced inner diameter over a part of the length of the liner, the at least one section providing a contact zone for the substrate tube. The microwave generator is configured to generate microwaves having a wavelength Lw in the range of 40 to 400 millimeters, wherein a length of said at least one section having the reduced inner diameter is at most 0.1×Lw.

Abstract: An optical fibre for propagating a signal in different modes, including a longitudinal length “a” of a change in the tension buildup in the optical fibre and a longitudinal distance “L” between two such changes are in accordance with the equation, a<=0.5 L, for at least part of the optical fibre.

Abstract: A method of manufacturing an optical fibre, which method comprises the steps of: i) providing an optical preform, ii) heating one end of said optical preform, iii) drawing an optical fibre from the heated end of the optical preform, iv) cooling the optical fibre thus drawn in step iii), v) winding the cooled optical fibre onto a reel, with a change in the tension buildup being introduced into the optical fibre in step iv), resulting in variations in the refractive index of the optical fibre as a function of the longitudinal position.

Abstract: A method of manufacturing an optical fiber and related devices using an apparatus having an elongated microwave guide coupled to a resonant cavity formed of an outer cylindrical wall and inner cylindrical wall having a slit with a width W and configured to deliver microwave energy having a vacuum wavelength ? to a resonant cavity thereof to satisfy the relationship: W??/10 where a substrate tube is located within the resonant cavity and plasma chemical vapor deposition deposits layers of doped silica thereon followed by thermal collapsing the substrate and drawing an optical fiber therefrom.

Abstract: A method of manufacturing an optical fiber and related devices using an apparatus having an elongated microwave guide coupled to a resonant cavity formed of an outer cylindrical wall and inner cylindrical wall having a slit with a width W and configured to deliver microwave energy having a vacuum wavelength &lgr; to a resonant cavity thereof to satisfy the relationship: W≦&lgr;/10 where a substrate tube is located within the resonant cavity and plasma chemical vapor deposition deposits layers of doped silica thereon followed by thermal collapsing the substrate and drawing an optical fiber therefrom.

Abstract: The present invention relates to a method for the manufacture of a single mode optical fibre comprising a light-conductive core portion, an internal cladding portion surrounding said core portion and a jacketing portion surrounding said internal cladding portion, in which the refractive index of the core portion is larger than those of the cladding and jacketing portion areas, and in which the refractive indices of the cladding and jacketing portion areas are practically equal.

Abstract: The invention relates to a method of applying a protective organic coating to an optical glass fiber, said glass fiber is drawn from a preform and passed through a liquid which contains the material for forming said organic coating, once the amount of liquid coating material to be applied to the fiber has been adjusted, said coating matrial is hardened, while a gas is passed along the liquid wherein nitrous oxide (an N2O-containing gas) is used as said gas. The invention also relates to the coated optical glass fiber, produced by that method.

Abstract: The present invention relates to a method for producing a preform, which is substantially free of OH impurities, for an optical fiber, wherein one or more quartz layers, which may or may not be doped, are deposited on the internal surface of a quartz glass support tube, in which method a furnace is moved axially with respect to the support tube, and after the quartz layers have been deposited the support tube is contracted into a bar-shaped preform while being heated, wherein the furnace comprises an electrical resistance furnace, in which furnace the support tube is rotated, with the space between the rotating support tube and the furnace being washed with an inert gas.

Abstract: The invention relates to an apparatus for performing Plasma Chemical Vapor Deposition (PCVD), whereby one or more layers of silica can be deposited on an elongated vitreous substrate. The apparatus includes an elongated microwave guide which emerges into a resonant cavity which is substantially cylindrically symmetric about a cylindrical axis, along which axis the substrate can be positioned. Aspects of the apparatus include the cavity being substantially annular in form, with an inner cylindrical wall and an outer cylindrical wall and the inner cylindrical wall having a slit which extends in a full circle around the cylindrical axis: Additional aspects include the guide having a longitudinal axis which is substantially perpendicular to the cylindrical axis and which does not intercept the slit. The invention also relates to a method of manufacturing an optical fiber, a preform rod and a jacket tube as well as to the thus obtained optical fiber.

Abstract: The present invention relates to a method for producing a perform, which is substantially free of PH impurities, for an optical fibre, wherein one or more quartz layers, which may or may not be doped, are deposited on the internal surface of a quartz glass support tube, in which method a furnace is move axially with respect to the support tube, and after the quartz layers have been deposited the support tube is contracted into a bar-shaped perform while being heated, wherein the furnace comprises an electrical resistance furnace, in which furnace the support tube is rotated, with the space between the rotating support tube and the furnace being washed with an inert gas.

Abstract: The present invention relates to a method of applying glass layers, which may or may not be doped, to the interior of a substrate tube by means of a chemical vapor deposition (CVD) technique, using a reactive gas mixture, in order to obtain a preform that exhibits a precisely defined refractive index profile, which method comprises a number of steps.

Abstract: The invention relates to an apparatus for performing Plasma Chemical Vapor Deposition (PCVD), whereby one or more layers of silica can be deposited on an elongated vitreous substrate. The apparatus includes an elongated microwave guide which emerges into a resonant cavity which is substantially cylindrically symmetric about a cylindrical axis, along which axis the substrate can be positioned. Aspects of the apparatus include the cavity being substantially annular in form, with an inner cylindrical wall and an outer cylindrical wall and the inner cylindrical wall having a slit which extends in a full circle around the cylindrical axis: Additional aspects include the guide having a longitudinal axis which is substantially perpendicular to the cylindrical axis and which does not intercept the slit. The invention also relates to a method of manufacturing an optical fiber, a preform rod and a jacket tube as well as to the thus obtained optical fiber.

Abstract: The invention relates to a device for drawing optical fibers from a preform, comprising: a furnace comprising a tube for heating one end of said preform to the drawing temperature thereof, which tube comprises: i) a central tube, ii) an upper extension tube connected to the lower part of said central tube so as to obtain a gas tight seal against an ambient atmosphere exterior said furnace, wherein the upper extension tube comprises an inlet for an inert gas in the top region of the upper extension tube, as a result of which the preform and the fiber to be drawn therefrom are surrounded by an inert gas, iii) a lower extension tube connected to said upper extension tube in such a manner that a gas tight seal against an ambient atmosphere exterior said furnace is obtained, iv) a tube outlet connected to said lower extension tube, means for drawing the fiber, means for supporting the preform in the furnace.

Abstract: The present invention relates to a method of applying glass layers, which may or may not be doped, to the interior of a substrate tube by means of a chemical vapour deposition (CVD) technique, using a reactive gas mixture, in order to obtain a preform that exhibits a precisely defined refractive index profile, which method comprises a number of steps.

Abstract: The invention relates to an apparatus for performing Plasma Chemical Vapor Deposition (PCVD), whereby one or more layers of silica can be deposited on an elongated vitreous substrate, the apparatus comprising an elongated microwave guide which emerges into a resonant cavity which is substantially cylindrically symmetric about a cylindrical axis, along which axis the substrate can be positioned, in which apparatus: the cavity is substantially annular in form, with an inner cylindrical wall and an outer cylindrical wall; the inner cylindrical wall comprises a slit which extends in a full circle around the cylindrical axis; the guide has a longitudinal axis which is substantially perpendicular to the cylindrical axis and which does not intercept the slit. The invention also relates to a method of manufacturing an optical fiber, a preform rod and a jacket tube using said apparatus as well as to the thus obtained optical fiber.

Abstract: The present invention relates to a method for the manufacture of a single mode optical fibre comprising a light-conductive core portion, an internal cladding portion surrounding said core portion and a jacketing portion surrounding said internal cladding portion, in which the refractive index of the core portion is larger than those of the cladding and jacketing portion areas, and in which the refractive indices of the cladding and jacketing portion areas are practically equal.

Abstract: The invention relates to an apparatus for performing Plasma Chemical Vapor Deposition (PCVD), whereby one or more layers of silica can be deposited on an elongated vitreous substrate, the apparatus comprising an elongated microwave guide which emerges into a resonant cavity which is substantially cylindrically symmetric about a cylindrical axis, along which axis the substrate can be positioned, in which apparatus:

Abstract: The invention relates to an apparatus for performing Plasma Chemical Vapor Deposition (PCVD), whereby one or more layers of silica can be deposited on an elongated vitreous substrate, the apparatus comprising an elongated microwave guide which emerges into a resonant cavity which is substantially cylindrically symmetric about a cylindrical axis, along which axis the substrate can be positioned, in which apparatus: the cavity is substantially annular in form, with an inner cylindrical wall and an outer cylindrical wall; the inner cylindrical wall comprises a slit which extends in a full circle around the cylindrical axis; the guide has a longitudinal axis which is substantially perpendicular to the cylindrical axis and which does not intercept the slit. The invention also relates to a method of manufacturing an optical fiber, a preform rod and a jacket tube using said apparatus as well as to the thus obtained optical fiber.