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 form 1000° C. to 1400° C., wherein the bare optical fiber passes through the slow cooling device at least two times.

A system for processing optical fiber includes a draw furnace, a fiber conveyance pathway extending between an upstream end positioned at the draw furnace and a downstream end positioned opposite the upstream end, where optical fiber is conveyed along the fiber conveyance pathway from the upstream end to the downstream end in a fiber conveyance direction, a muffle in communication with the draw furnace and positioned downstream of the draw furnace, a second cooling device annularly surrounding the fiber conveyance pathway downstream from the draw furnace, the second cooling device including one or more second cooling device heating elements and a first cooling device positioned between the draw furnace and the second cooling device, wherein the first cooling device directs a fluid to contact the optical fiber.

A system for processing an optical fiber includes: a draw furnace, said draw furnace containing an optical fiber preform; a bare optical fiber drawn from said optical fiber preform, said bare optical fiber extending from said draw furnace along a process pathway; and a slow cooling device operatively coupled to and downstream from said draw furnace, said slow cooling device exposing said 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.

An optical fiber manufacturing method includes a first process of passing a glass fiber through a fiber path. The fiber path is formed through a cooling tube that is housed in a first casing. The method also includes a second process of leading the glass fiber into a second casing before leading into the first casing. The first process includes supplying a first dry gas, having a dew point lower than the temperature of the cooling tube, into a first dry space formed between the first casing and the cooling tube. The second process includes supplying a second dry gas into a second dry space formed inside the second casing so as to cause air pressure in the second dry space to be higher than air pressure in an external space. The dew point of the second dry gas is lower than the dew point in the external space.

Apparatuses and methods for processing an optical fiber preform are disclosed. According to one aspect, an apparatus may generally include a muffle defining an interior volume enclosed by at least one sidewall and a handle assembly for supporting the optical fiber preform in the muffle. The handle assembly may be removably coupled to the muffle and extend into the interior volume. At least one baffle may be positioned in the interior volume and define an upper portion of the interior volume and a lower portion of the interior volume. The at least one baffle may define at least one flow channel between the upper portion of the interior volume and the lower portion of the interior volume.

A method of processing an optical fiber that includes drawing an optical fiber along a fiber pathway through a hollow light pipe, wherein the hollow light pipe comprises a first end having an opening with a radius R.sub.p, a second end and a pipe body comprising a chamber extending from the first to the second end, the fiber pathway extending through the pipe body, and a reflective coating is disposed on the pipe body, and directing a light from a directed light source into the hollow light pipe through the opening such that the light is reflected by the reflective coating while propagating in the hollow light pipe, the optical fiber absorbing the light reflected by the reflective coating, wherein the light enters the opening of the hollow light pipe at an input angle in a range of from 10° to 70° with respect to the fiber pathway.

An optical fiber forming apparatus comprises: a draw furnace; a tube that extends into the passageway of the draw furnace; and a cooling device at an outlet of the tube, the cooling device comprising: one or more bodies having a top surface and an opposing bottom surface, an opening within the body extending from the top surface through the body to the bottom surface, wherein the opening is configured to pass an optical fiber through the body, and one or more gas outlets within the body configured to direct gas to contact the optical fiber as it passes through the opening.

A method of processing an optical fiber includes drawing the optical fiber from a heated glass source, reheating the optical fiber, and cooling the optical fiber under vacuum at a cooling rate less than the cooling rate of the optical fiber in air at 25° C. and 1 atm. Cooling the optical fiber under vacuum is conducted after reheating the optical fiber. Cooling the optical fiber under vacuum reduces the rate of heat transfer from the optical fiber, which may enable further relaxation of the glass and reduction in the fictive temperature of the optical fiber. A system for processing an optical fiber includes a furnace containing a fiber preform, a first positioner, a reheating device, and a treatment device downstream of the reheating device, the treatment device operable to cool the optical fiber under vacuum to reduce the rate of heat transfer from the optical fiber.

A drawing furnace for drawing a glass element includes: a furnace body having an upper end and a lower end. The furnace body includes a top annular plate, an A/C induction coil capable of accepting electrical current and producing an oscillating electronic signal, a cylindrical susceptor capable of producing heat output, a cylindrical quartz beaker, an insulating material disposed between the susceptor and the beaker, and a bottom annular plate housing and supporting at least one of the susceptor, the beaker, and the insulating material. wherein the furnace body comprises a central longitudinal axis; A rotational drive system operably connected to the bottom annular plate by an annular rotation gear system rotates the bottom annular plate along with the susceptor, beaker, and/or insulating material at a frequency between 0.01 to 10 Hz. The electrical current and oscillation frequency determine the heat output of the susceptor.