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 preform for optical fibers, which method comprises the sequential steps of: i) deposition of non-vitrified silica layers on the inner surface of a hollow substrate tube; ii) deposition of vitrified silica layers inside the hollow substrate tube on the inner surface of the non-vitrified silica layers deposited in step i); iii) removal of the hollow substrate tube from the vitrified silica layers deposited in step ii) and the non-vitrified silica layers deposited in step i) to obtain a deposited tube; iv) optional collapsing said deposited tube obtained in step iii) to obtain a deposited rod comprising from the periphery to the center at least one inner optical cladding and an optical core; v) preparation of an intermediate layer by the steps of: * deposition of non-vitrified silica layers on the outside surface of the deposited tube obtained in step iii) or deposited rod obtained in step iv) with a flame hydrolysis process in an outer reaction zone

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: The invention relates to a device, system, and method for forming a core-rod for optical fibers by collapsing a tube comprising deposited layers of silica to form the core-rod. The device comprises an elongate cavity, an elongate cylindrical carbon liner bounding the cavity, the liner connecting to a frame of the device at opposing end portions, a heating element in a heating element space, surrounding the liner, the liner separating the heating element space from the cavity, a ring of a refractory material, fixated to the frame, surrounding a part of a length of the cavity, the liner being provided such that an inner surface portion at a first end portion of the liner mates with a cylindrical outer surface portion of the ring such that the liner can axially move with the first end portion thereof along the outer surface portion of the ring.

Abstract: The invention relates to exemplary methods, devices, and systems for heating an elongate silica cylinder to form a core-rod for optical fibers. An exemplary heating device includes an elongate cavity, an elongate liner bounding the cavity, a heating element in a heating element space surrounding the liner, the liner separating the heating element space from the cavity, and a gas flushing device for effecting a flow of gas at least through the heating element space. An exemplary method includes providing the elongate silica cylinder such that it extends through the cavity, heating the cylinder locally beyond its softening temperature, and effecting a flow of argon and nitrogen gas during the heating.

Abstract: A method is described for manufacturing an optical fiber preform, including a tube collapsing phase, and including monitoring the concentration of at least one fluid component of a fluid that is exhausted from the tube, to detect structural integrity of the tube. A system is also described for manufacturing optical fiber preforms. The system comprising a holder configured to hold a tube, a heater configured to heat at least part of the tube to a tube collapsing temperature, a fluid exhaust configured to discharge fluid from the tube, held by the holder. The system also includes a tube integrity monitor configured to monitor structural integrity of the tube, during a collapsing phase, by monitoring fluid that is discharged from the tube.

Abstract: A method for activating an inner surface of a hollow glass substrate tube for manufacturing an optical fiber preform including depositing a plurality of activation glass layers on the inner surface of the hollow substrate tube by a PCVD process, wherein a total thickness of the deposited activation glass layers is between 10 microns and 250 microns, and etching the deposited activation glass layers to remove at least 30% of the deposited activation glass layers.

Abstract: The invention relates to a method and an apparatus for performing a plasma chemical vapour deposition process. The apparatus comprises a mainly cylindrical resonator being provided with an outer cylindrical wall and an inner coaxial cylindrical wall defining therebetween a resonant cavity that is operable at an operating frequency. The resonant cavity extends in a circumferential direction around a cylindrical axis of the inner and outer cylindrical wall. Further, the outer cylindrical wall includes an input port connectable to an input waveguide. In addition, the inner cylindrical wall includes slit sections extending in a circumferential direction around the cylindrical axis. A greatest dimension defining the aperture of the slit sections is smaller than half the wavelength of the operating frequency.

Abstract: A method and apparatus for performing a plasma chemical vapour deposition process including a mainly cylindrical resonator having an outer cylindrical wall and an inner coaxial cylindrical wall defining therebetween a resonant cavity operable at an operating frequency. The resonant cavity extends in a circumferential direction around a cylindrical axis of the inner and outer cylindrical wall. The outer cylindrical wall includes an input port connectable to an input waveguide. The inner cylindrical wall includes slit sections extending in a circumferential direction around the cylindrical axis. A greatest dimension defining the aperture of the slit sections is smaller than half the wavelength of the operating frequency.

Abstract: An exemplary method for preparing a primary preform by etching and collapsing a deposited tube includes mounting a deposited tube on a lathe and introducing the deposited tube into a central aperture of a furnace mounted on the lathe, wherein the furnace and the deposited tube are movable in axial direction with respect to each other, and creating within the furnace a hot zone that moves in translation back and forth over the length of the deposited tube during one or more cycles, wherein (i) during at least one cycle at least part of the outside of the deposited tube is etched by supplying a fluorine-containing etching gas to an annular region between the outer surface of the deposited tube and the central aperture of the furnace, and (ii) during at least one cycle the deposited tube is collapsed.

Abstract: A rotary feed-through for mounting a rotating substrate tube in a lathe and providing a flow of process gas into the tube, said feed-through including a process gas supply line for providing a process gas into said substrate tube, a rotatable holder arranged for receiving and holding said substrate tube for rotating said substrate tube with respect to said process gas supply line, a rotary union provided between said rotatable holder and said process gas supply line for rotatably connecting said rotatable holder to said process gas supply line, a stationary housing connected to said process gas supply line and to said rotatable holder, therewith forming a closed cavity surrounding said rotary union, wherein said stationary housing further includes an auxiliary gas supply line for providing said closed cavity with an auxiliary gas.

Abstract: The invention relates to exemplary methods, devices, and systems for heating an elongate silica cylinder to form a core-rod for optical fibers. An exemplary heating device includes an elongate cavity, an elongate liner bounding the cavity, a heating element in a heating element space surrounding the liner, the liner separating the heating element space from the cavity, and a gas flushing device for effecting a flow of gas at least through the heating element space. An exemplary method includes providing the elongate silica cylinder such that it extends through the cavity, heating the cylinder locally beyond its softening temperature, and effecting a flow of argon and nitrogen gas during the heating.

Abstract: The invention relates to a device, system, and method for forming a core-rod for optical fibers by collapsing a tube comprising deposited layers of silica to form the core-rod. The device comprises an elongate cavity, an elongate cylindrical carbon liner bounding the cavity, the liner connecting to a frame of the device at opposing end portions, a heating element in a heating element space, surrounding the liner, the liner separating the heating element space from the cavity, a ring of a refractory material, fixated to the frame, surrounding a part of a length of the cavity, the liner being provided such that an inner surface portion at a first end portion of the liner mates with a cylindrical outer surface portion of the ring such that the liner can axially move with the first end portion thereof along the outer surface portion of the ring.

Abstract: The present invention relates to a method for manufacturing a preform for optical fibers, which method comprises the sequential steps of: i) deposition of non-vitrified silica layers on the inner surface of a hollow substrate tube; ii) deposition of vitrified silica layers inside the hollow substrate tube on the inner surface of the non-vitrified silica layers deposited in step i); iii) removal of the hollow substrate tube from the vitrified silica layers deposited in step ii) and the non-vitrified silica layers deposited in step i) to obtain a deposited tube; iv) optional collapsing said deposited tube obtained in step iii) to obtain a deposited rod comprising from the periphery to the center at least one inner optical cladding and an optical core; v) preparation of an intermediate layer by the steps of: *deposition of non-vitrified silica layers on the outside surface of the deposited tube obtained in step iii) or deposited rod obtained in step iv) with a flame hydrolysis process in an outer reaction zone u

Abstract: The present invention relates in a first aspect to a method for etching a primary preform or core rod. The present invention moreover relates in a second aspect to the etched primary preform thus obtained and moreover to a final preform and optical fibers obtained therefrom and to a method of preparing optical fibers therefrom.

Abstract: A rotary feed-through for mounting a rotating substrate tube in a lathe and providing a flow of process gas into the tube, said feed-through including a process gas supply line for providing a process gas into said substrate tube, a rotatable holder arranged for receiving and holding said substrate tube for rotating said substrate tube with respect to said process gas supply line, a rotary union provided between said rotatable holder and said process gas supply line for rotatably connecting said rotatable holder to said process gas supply line, a stationary housing connected to said process gas supply line and to said rotatable holder, therewith forming a closed cavity surrounding said rotary union, wherein said stationary housing further includes an auxiliary gas supply line for providing said closed cavity with an auxiliary gas.

Abstract: A method and apparatus for performing a plasma chemical vapour deposition process including a mainly cylindrical resonator having an outer cylindrical wall and an inner coaxial cylindrical wall defining therebetween a resonant cavity operable at an operating frequency. The resonant cavity extends in a circumferential direction around a cylindrical axis of the inner and outer cylindrical wall. The outer cylindrical wall includes an input port connectable to an input waveguide. The inner cylindrical wall includes slit sections extending in a circumferential direction around the cylindrical axis. A greatest dimension defining the aperture of the slit sections is smaller than half the wavelength of the operating frequency.

Abstract: A device for manufacturing an optical preform by means of an internal vapour deposition process including an energy source, a hollow substrate tube having a supply side and a discharge side and the energy source being moveable along a length of the hollow substrate tube, and an elongation tube connected to the hollow substrate tube at the discharge side thereof, wherein the hollow substrate tube extends into an interior of the elongation tube and an internal diameter of the elongation tube is at least 0.5 millimeters larger than an external diameter of the hollow substrate tube.

Abstract: A method activates the inner surface of a substrate tube via plasma etching with a fluorine-containing etching gas. An exemplary method includes the steps of (i) supplying a supply flow of gas to the interior of a substrate tube, wherein the supply flow includes a main gas flow and a fluorine-containing etching gas flow, (ii) inducing a plasma via electromagnetic radiation to create a plasma zone within the substrate tube's interior, and (iii) longitudinally reciprocating the plasma zone over the length of the substrate tube between a reversal point near the supply side and a reversal point near the discharge side of the substrate tube. The flow of the fluorine-containing etching gas is typically provided when the plasma zone is near the supply side reversal point.