A system for precoating a preform for drawing optical fiber including a diameter sensor to determine a diameter of pulled optical fiber, a cooling system to cool the optical fiber once it is pulled from a furnace, a coating system to apply a coating to the optical fiber once it has cooled and an ultra-violet lamp to cure the coating.

To prevent a lowering of gripping force due to temperature changes, provided is a gripping mechanism including a plurality of chuck claws that, when having come close to each other, generate a gripping force on a gripped body; a chuck body that holds the plurality of chuck claws on a common planar surface, and moves them on the planar surface; and a plurality of chuck plates that, when each of the plurality of chuck claws grips the gripped body, are interposed between each of the plurality of chuck claws and the gripped body. A thermal expansion coefficient .sub.1 of the plurality of chuck claws, a thermal expansion coefficient .sub.2 of the plurality of chuck plates and a thermal expansion coefficient .sub.W of the gripped body have a relationship indicated by
.sub.W<.sub.1<.sub.2(Equation 1).

The present disclosure relates to a method and apparatus for constraining an optical fiber (104) in the draw tower (100, 101). The method (700) includes steps of trapping (714) the optical fiber (104) in a central position along a vertical axis (Y-Y) by one or more acoustic waves generated by an acoustic centering apparatus (112). In particular, the vertical axis (Y-Y) is parallel to a draw tower axis (Y-Y) and/or coincides with the draw tower axis (Y-Y). The movement of the optical fiber (104) is constrained within 1 milli-meter from the vertical axis (Y-Y) with a coating ovality of a coated optical fiber (105) is less than 4%.

There is provided a method for producing a multicore optical fiber while reducing the mass of a glass block to be connected to a common cladding tube. A production method for a multicore optical fiber includes in order, a preform forming step of forming a common cladding tube having a plurality of holes extending between a first end and a second end, an insertion step of inserting core rods in the holes in a state in which end portions of the core rods are recessed from the first end, a heat shrinkage step of reducing a diameter of the first end by heating, a sealing step of sealing the holes by connecting a glass block to the first end, and a drawing step of depressurizing insides of the holes from the second end and performing spinning from the first end while combining the common cladding tube and the core rods.

There is provided a method for producing a multicore optical fiber while depressurizing holes in a common cladding tube. A production method for a multicore optical fiber includes a preform forming step of forming a common cladding tube having a plurality of holes extending between a first end and a second end, an end-face working step of digging the common cladding tube from the second end to a predetermined depth to forming a third end, a connection step of connecting a glass tube to the second end, an insertion step of inserting core rods into the holes to the third end, a sealing step of sealing the first end, and a drawing step of spinning the multicore optical fiber while depressurizing the holes through the glass tube and combining the common cladding tube and the core rods from the first end.

A method for fabricating a multicore fiber comprised of an elongate base body containing a glass cladding material and having at least two through-holes, inserting a core rod into the through-holes so as to form a component ensemble, drawing the component ensemble to form the multicore fiber, wherein the component ensemble is held from above by a holder made of glass, which is connected to the base body so as to form a welding contact surface. The fitting of the base body with core rods is not limited by the layout of the holder, and which in particular allows placement of all core rods from above even after the holder has been welded on, a holder with an elongate hollow part is used, having a hollow channel with an inner contour that is larger than a hole area circumference within which the through-holes lie at least 90% of their diameter.

A sealing arrangement for a drawing furnace including a vertical center hole with surrounding heating elements for receiving a glass preform including a tapered portion connected to an extension rod. A sealing with an opening is arranged on top of the furnace. The arrangement includes an outer annular bushing arranged on top of the furnace and an inner annular bushing with a first and an opposing second vertical end. The inner bushing is positionable to surround at least part of the tapered portion with the first end positioned to the region of the beginning of the tapered portion and the second end includes protrusions on the outer surface. As the inner bushing is inserted in the outer bushing it is arranged to be movable within the outer bushing and the protrusions form supports for holding the second end of the inner bushing above the center hole.

A system for positioning an optical preform in a furnace is provided that includes an upper muffle and a downfeed handle assembly with a tube defining a first end and a second end, the second end extending into the upper muffle. A handle is disposed within the tube. A second end of the handle extends into the upper muffle and a seal assembly is positioned around both the tube and the handle. The first end of the handle extends through the seal assembly and a drive assembly is coupled with the downfeed handle.

A system for processing an optical fiber includes: a draw furnace, the draw furnace containing an optical fiber preform; a bare optical fiber drawn from the optical fiber preform, the bare optical fiber extending from the draw furnace along a process pathway; and a slow cooling device operatively coupled to and downstream from the draw furnace, the slow cooling device exposing the bare optical fiber to a slow cooling device process temperature in the range from 1000 C. to 1400 C., wherein the bare optical fiber passes through the slow cooling device at least two times.

An optical fiber has a central axis. The optical fiber includes a core made of silica glass and extending along the central axis, a cladding made of silica glass and surrounding the core, the cladding extending along the central axis, and a coating layer made of resin and surrounding the cladding, the coating layer extending along the central axis. An outer diameter of the cladding varies along the central axis. A residual stress in a direction along the central axis varies along the central axis, the residual stress being averaged over the core and the cladding in a cross section perpendicular to the central axis. A deviation from an average value of the outer diameter and a deviation from an average value of the residual stress have signs opposite to each other.