Abstract: The present invention relates to a method of removing a substrate tube from the deposited layer inside of said substrate tube.

Abstract: Disclosed are methods for manufacturing a precursor for a primary preform for optical fibers via an internal plasma deposition process. An exemplary method includes creating a first plasma reaction zone having first reaction conditions in the interior of a hollow substrate tube to deposit non-vitrified silica layers on the inner surface of the hollow substrate tube, and subsequently creating a second plasma reaction zone having second reaction conditions in the interior of the hollow substrate tube to deposit vitrified silica layers on the deposited, non-vitrified silica layers. Thereafter, the hollow substrate tube is removed from the deposited, vitrified silica layers to yield a deposited tube.

Abstract: A method for manufacturing an optical preform including the steps of providing a substrate tube having deposited layers of glass on an inside surface thereof, increasing an outer diameter of the substrate tube by means of applying a traversing heat source to heat the substrate tube to above a softening temperature thereof and by providing an internal pressure in the substrate tube higher than an ambient pressure, and collapsing the substrate tube of increased outer diameter by means of applying the traversing heat source to heat the substrate tube to above the softening temperature thereof such that an optical preform is manufactured.

Abstract: A method for manufacturing a precursor for a primary preform for optical fibers by an internal plasma deposition process including the steps of providing a hollow substrate tube, creating a first plasma reaction zone having first reaction conditions and depositing non-vitrified silica layers along at least a portion of the inner surface of the substrate tube, subsequently creating a second plasma reaction zone having second reaction conditions different from the first reaction conditions and depositing vitrified silica layers along at least a portion of the substrate tube, and cooling the substrate tube to produce the precursor for a primary preform.

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 method for carrying out a plasma deposition process including the steps of providing a substrate tube, supplying dopant-containing glass-forming gases to the substrate including a main gas flow and one or more secondary gas flows, inducing a plasma in the substrate tube, moving a reaction zone back and forth in strokes between a reversal point near the supply side and a reversal point near the discharge side, and interrupting the secondary gas flow during a portion of each stroke, each interruption having a start point and an end point within the same stroke.

Abstract: The invention relates to an apparatus for performing a plasma chemical vapor deposition process. The apparatus comprises a mainly cylindrical resonator being provided with an outer cylindrical wall enclosing a resonant cavity extending in a circumferential direction around a cylindrical axis. The resonator is further provided with side wall portions bounding the resonant cavity in the cylindrical direction, and with a slit configuration extending in a circumferential direction around the cylindrical axis providing access from the resonant cavity radially inwardly. Further, the slit configuration includes slit sections that are mutually offset in the cylindrical direction.

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 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.

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 for manufacturing a primary preform for optical fibers including surrounding at least part of a hollow substrate tube with a furnace set at a temperature T0, supplying doped or undoped gases to the inside of the tube, creating a reaction zone to promote deposition, and moving the zone back and forth along the length of the tube between to form at least one preform layer, wherein the temperature of the furnace is varied linearly as a function of the thickness of the at least one preform layer to compensate for temperature increases of the tube during deposition.

Abstract: A device for manufacturing an optical preform by means of an internal vapor 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: Disclosed are methods for manufacturing a precursor for a primary preform for optical fibers via an internal plasma deposition process. An exemplary method includes creating a first plasma reaction zone having first reaction conditions in the interior of a hollow substrate tube to deposit non-vitrified silica layers on the inner surface of the hollow substrate tube, and subsequently creating a second plasma reaction zone having second reaction conditions in the interior of the hollow substrate tube to deposit vitrified silica layers on the deposited, non-vitrified silica layers. Thereafter, the hollow substrate tube is removed from the deposited, vitrified silica layers to yield a deposited tube.

Abstract: The invention relates to an apparatus for performing a plasma chemical vapor deposition process. The apparatus comprises a mainly cylindrical resonator being provided with an outer cylindrical wall enclosing a resonant cavity having a substantially rotational symmetric shape with respect to a cylindrical axis. The resonator further includes side wall portions bounding the resonant cavity in opposite cylindrical axis directions. In addition, the apparatus comprises a microwave guide extending through the outer cylindrical wall into the resonant cavity. The length of the resonant cavity in the cylindrical direction varies as a function of the radial distance to the cylindrical axis.

Abstract: The present invention relates to a method of removing a substrate tube from the deposited layer inside of said substrate tube.

Abstract: A method for manufacturing a primary preform including providing a hollow substrate tube, supplying to the interior of the tube a main gas flow containing at least one glass-forming gas and at least one secondary gas flow containing at least one precursor for a dopant, creating a plasma reaction zone in the interior of the tube to effect deposition, and interrupting the supply of the at least one secondary gas flow near the reversal points of the supply and discharge sides of the substrate tube.

Abstract: A method for manufacturing an optical preform including the steps of providing a substrate tube having deposited layers of glass on an inside surface thereof, increasing an outer diameter of the substrate tube by means of applying a traversing heat source to heat the substrate tube to above a softening temperature thereof and by providing an internal pressure in the substrate tube higher than an ambient pressure, and collapsing the substrate tube of increased outer diameter by means of applying the traversing heat source to heat the substrate tube to above the softening temperature thereof such that an optical preform is manufactured.

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 for carrying out a plasma deposition process including the steps of providing a substrate tube, supplying dopant-containing glass-forming gases to the substrate including a main gas flow and one or more secondary gas flows, inducing a plasma in the substrate tube, moving a reaction zone back and forth in strokes between a reversal point near the supply side and a reversal point near the discharge side, and interrupting the secondary gas flow during a portion of each stroke, each interruption having a start point and an end point within the same stroke.

Abstract: A method for manufacturing a precursor for a primary preform for optical fibres by an internal plasma deposition process including the steps of providing a hollow substrate tube, creating a first plasma reaction zone having first reaction conditions and depositing non-vitrified silica layers along at least a portion of the inner surface of the substrate tube, subsequently creating a second plasma reaction zone having second reaction conditions different from the first reaction conditions and depositing vitrified silica layers along at least a portion of the substrate tube, and cooling the substrate tube to produce the precursor for a primary preform.