A system and method for processing an optical fiber includes a treatment device disposed downstream of a furnace and including a treating zone. The treating zone includes a fiber inlet and fiber outlet and is configured to cool the optical fiber at a reduced pressure below ambient pressure and at a slow cooling rate less than an ambient cooling rate. A nozzle assembly is disposed at one or more of the fiber inlet, the fiber outlet, upstream of the treating zone, and downstream of the treating zone. The nozzle assembly includes multiple baffle plates defining a number of nozzle chambers, each nozzle chamber having a nozzle chamber pressure, wherein each baffle plate includes an orifice having a predetermined effective orifice diameter through which the optical fiber passes. Each nozzle chamber is configured to sequentially change a nozzle chamber pressure between the reduced pressure and ambient pressure.

An optical fiber manufacturing method includes a process of passing a glass fiber through a fiber path before applying a resin. The glass fiber is drawn from a glass preform, the fiber path is formed through a cooling tube, and the cooling tube is housed in a casing and is cooled by a coolant. The process includes supplying a dry gas into a dry space formed between the casing and the cooling tube. The dry gas has a first dew point lower than the temperature of the cooling tube. The process includes measuring, by a dew point meter, a second dew point at one or both of an inlet and an outlet of the fiber path. The process includes controlling the temperature of the coolant in the cooling tube such that the temperature of the cooling tube is higher than the second dew point measured by the dew point meter.

In some embodiments, a method for processing an optical fiber includes: drawing an optical fiber through a draw furnace, conveying the optical fiber through a flame reheating device downstream from the draw furnace, wherein the flame reheating device comprises one or more burners each comprising: a body 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 optical fiber passes through the opening, and one or more gas outlets within the body; and igniting a flammable gas provided by the one or more gas outlets to form a flame encircling the optical fiber passing through the opening, wherein the flame heats the optical fiber by at least 100 degrees Celsius at a heating rate exceeding 10,000 degrees Celsius/second.

A manufacturing method for an optical fiber, includes: drawing, while heating in a heating furnace, a lower end of an optical fiber preform that is to be an optical fiber having a core consisting of silica glass containing a rare earth element compound. The heating furnace has a temperature profile in which a temperature of the heating furnace increases to a maximum temperature T.sub.max and then decreases from an upstream side of the heating furnace toward a downstream side of the heating furnace. The temperature profile has a changing point at which the temperature decreases more steeply on the downstream side from a position where the maximum temperature T.sub.max is reached. At the maximum temperature, a temperature of the silica glass is higher than or equal to a glass transition temperature and the silica glass is in a single phase.

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.

An optical fiber production method includes: drawing an optical fiber preform in a drawing furnace; and cooling the optical fiber. The optical fiber is passed through a plurality of annealing furnaces while the optical fiber is cooled. While the optical fiber is cooled, temperatures of the annealing furnaces are set such that the temperature difference is within a range between and including an upper limit and a lower limit of a temperature difference between a temperature of the optical fiber and a fictive temperature of glass constituting a core of the optical fiber at which an increase of a transmission loss of the optical fiber when the fictive temperature of the glass is decreased is less than 0.001 dB/km.

A method of heating an optical fiber, the method including flowing gas from a common gas channel into one or more gas outlets of a burner, the common gas channel encircling an aperture of the burner. The method further including igniting the gas to form a flame and heating the fiber with the flame as the fiber passes through the aperture. The one or more gas outlets opening into the aperture such that each gas outlet has a gas outlet bore terminating at an inward-facing wall of the burner that defines the aperture. And the gas outlet bore being oriented at an angle .sub.1 defined between the gas outlet bore and the inward-facing wall of the burner, downstream of the gas outlet bore, that is greater than or equal to 10 degrees and less than or equal to 70 degrees.

The present disclosure provides the installation of an apparatus for cooling a manufactured glass rod. The apparatus has at least two cooling chambers arranged along the glass strand for sectional cooling of the glass strand. A gaseous cooling medium is either blown into the cooling chamber or sucked out of the cooling chambers. The glass strand is passed through each cooling chamber, with an orifice provided at each of the pass-through points, whose opening is larger than the cross-section or diameter of the glass strand. As a result, an annular gap forms between the opening and the surface of the glass strand, so that a turbulent flow of the gaseous cooling medium is generated, which enables a high cooling rate.

A system and method for processing an optical fiber includes a treatment device disposed downstream of a furnace and including a treating zone. The treating zone includes a fiber inlet and fiber outlet and is configured to cool the optical fiber at a reduced pressure below ambient pressure and at a slow cooling rate less than an ambient cooling rate. A nozzle assembly is disposed at one or more of the fiber inlet, the fiber outlet, upstream of the treating zone, and downstream of the treating zone. The nozzle assembly includes multiple baffle plates defining a number of nozzle chambers, each nozzle chamber having a nozzle chamber pressure, wherein each baffle plate includes an orifice having a predetermined effective orifice diameter through which the optical fiber passes. Each nozzle chamber is configured to sequentially change a nozzle chamber pressure between the reduced pressure and ambient pressure.

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.