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.

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.

An optical fiber with low fictive temperature along with a system and method for making the optical fiber are provided. The system includes a reheating stage that heats the fiber along the process pathway to a temperature sufficient to lower the fictive temperature of the fiber by relaxing the glass structure and/or driving the glass toward a more nearly equilibrium state. The fiber is drawn from a preform, conveyed along a process pathway, cooled and subsequently reheated to increase the time of exposure of the fiber to temperatures conducive to lowering the fictive temperature of the fiber. The process pathway may include multiple reheating stages as well as one or more fiber-turning devices.

A method for manufacturing an optical fiber is disclosed. The method for manufacturing an optical fiber includes: drawing an optical fiber by heating an optical fiber preform inside a drawing furnace into which a first gas is introduced; and annealing the optical fiber by causing the optical fiber to pass through an annealing furnace disposed downstream of the drawing furnace and adjusted to a temperature lower than a temperature at which the optical fiber preform is heated. In the annealing, a second gas having a lower heat conductivity than the first gas is introduced into the annealing furnace through one or more gas introduction ports such that a total flow rate becomes 3 slm or higher, and a flow rate of the second gas per gas introduction port is adjusted to 30 slm or lower.

A method of controlling the temperature of an optical fiber is provided that includes the steps of: providing an energy transfer member configured to accept or provide thermal energy, the energy transfer member defines an energy transfer surface; passing an optical fiber proximate the energy transfer member such that a gap is defined between the optical fiber and the energy transfer surface; and transferring thermal energy between the optical fiber and the energy transfer member via conduction across the gap.

An optical fiber comprises, from a center to a periphery, a fiber core of undoped silica; a cladding layer; and a coating of polyacrylate, wherein the fiber core has a radius of 5 to 7 m and an ellipticity of less than 1.5%, the cladding layer with an ellipticity of less than 0.4% comprises inner, intermediate, and outer cladding layers, the inner cladding layer being doped with fluorine of 5 to 12 m thickness, and refractive index difference to fiber core of 0.4 to 0.2%, the outer cladding layer being undoped quartz of 25 to 45 m thickness, and the coating comprises an inner coating of 25 to 40 m thickness, and an outer coating of 25 to 35 m thickness and an ellipticity of less than 2%. The optical fiber has high durability and large effective transmission area, a method and system for preparing such optical fiber are also disclosed.

An optical fiber manufacturing method includes: drawing an optical fiber preform to form a bare optical fiber; cooling the bare optical fiber by a non-contact direction changer; adjusting a temperature of the bare optical fiber in a temperature adjusting unit disposed downstream of the non-contact direction changer and upstream of a coating unit; disposing, in the coating unit, an uncured coating layer that comprises a resin precursor on an outer periphery of the bare optical fiber; and curing the uncured coating layer in a curing unit.

A method of making optical fibers that includes controlled cooling to produce fibers having a low concentration of non-bridging oxygen defects and low sensitivity to hydrogen. The method may include heating a fiber preform above its softening point, drawing a fiber from the heated preform and passing the fiber through two treatment stages. The fiber may enter the first treatment stage at a temperature between 1500 C. and 1700 C., may exit the first treatment stage at a temperature between 1200 C. and 1400 C., and may experience a cooling rate less than 5000 C./s in the first treatment stage. The fiber may enter the second treatment stage downstream from the first treatment stage at a temperature between 1200 C. and 1400 C., may exit the second treatment stage at a temperature between 1000 C. and 1150 C., and may experience a cooling rate between 5000 C./s and 12,000 C./s in the second treatment stage. The method may also include redirecting the fiber with a fluid bearing device or an air-turn device.

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.

An optical fiber manufacturing method includes: melting and drawing an optical fiber preform to form a glass fiber; cooling the glass fiber while inserting the glass fiber into a tubular slow-cooling device from an inlet end toward an outlet end thereof; and lowering an inner wall temperature of the slow-cooling device below a temperature of the glass fiber and providing a pressure gradient in which a pressure increases in a direction from the inlet end toward the outlet end inside the slow-cooling device when cooling the glass fiber, wherein the average pressure change dP/dL in a moving direction of the glass fiber inside the slow-cooling device satisfies the following Formula (1) when the tube inner diameter of the slow-cooling device is defined as D [m] and the length of an internal space of the slow-cooling device in the moving direction of the glass fiber is defined as L [m].
(D.sup.2/4)dP/dL0.03(1)