Device, system, and method for forming a core-rod for optical fibers

A device for forming a core-rod for optical fibers, the device being arranged for collapsing a tube comprising deposited layers of silica to form the core-rod, the device comprising:

• an elongate cavity extending in an axial direction of the device, arranged for allowing the tube to extend through the cavity in use;
• an elongate cylindrical liner made of carbon, extending in the axial direction and bounding the cavity with a cylindrical wall thereof, the liner connecting to a frame of the device at opposing end portions of the liner, wherein the liner has a length-to-diameter ratio in the range of 3 to 10;
• a heating element for heating the tube in use, the heating element being provided in an annular heating element space, said heating element surrounding at least a part of the liner, the cylindrical wall of the liner separating the heating element space from the cavity, wherein the liner comprises several through holes in the cylindrical wall, via which holes gas may be forced from the heating element space to the cavity;
• and
• a ring made of a refractory material, fixated to a frame of the device, the ring surrounding a part of a length of the cavity, wherein the liner is provided such that a cylindrical inner surface portion of the liner at a first end portion of the opposing end portions 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;
• and
• a further ring made of a refractory material, fixated to the frame of the device, the further ring surrounding a part of a length of the cavity, wherein the liner is provided such that an inner cylindrical surface portion at a second end portion of the opposing end portions mates with an outer cylindrical surface portion of the further ring such that the liner can axially move with the second end portion thereof along the outer surface portion of the further ring.

A system for forming a core-rod for optical fibers, the system being arranged for collapsing a tube comprising deposited layers of silica to form the core-rod in use, wherein the system comprises (i) a device for forming a core-rod for optical fibers, the device being arranged for collapsing a tube comprising deposited layers of silica to form the core-rod, and (ii) a moving device configured for moving the device with respect to the tube in a reciprocating manner in the axial direction, wherein the device comprises:

• an elongate cavity extending in an axial direction of the device, arranged for allowing the tube to extend through the cavity in use;
• an elongate cylindrical liner made of carbon, extending in the axial direction and bounding the cavity with a cylindrical wall thereof, the liner connecting to a frame of the device at opposing end portions of the liner;
• a heating element for heating the tube in use, the heating element being provided in an annular heating element space, said heating element surrounding at least a part of the liner, the cylindrical wall of the liner separating the heating element space from the cavity;
• and
• a ring made of a refractory material, fixated to a frame of the device, the ring surrounding a part of a length of the cavity;
• wherein the liner is provided such that a cylindrical inner surface portion of the liner at a first end portion of the opposing end portions 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.