A method for elongating a glass preform for an optical fiber is provided for producing a glass rod having a smaller diameter by elongating the glass preform having a large diameter, the method including: when the glass preform having a tapered transparent glass portion at one end of a straight body of the glass preform and a tapered portion including an opaque glass portion at another end is elongated, prior to the elongating, cutting a part of the tapered portion including the opaque glass portion, wherein a cut surface of the part is a lower end of the glass preform; and welding the cut surface of the tapered portion to a pulling dummy connected to a pulling mechanism in a elongating apparatus, wherein the cut surface is circular and has an outer diameter ranging from 135 mm to 160 mm.

A method of manufacturing an optical fiber of the invention includes: preparing a direction changer; drawing a bare optical fiber from an optical fiber preform, thereby forming the bare optical fiber; providing a coated layer made of a resin on a periphery of the bare optical fiber; obtaining an optical fiber by curing the coated layer; changing a direction of the bare optical fiber by use of the direction changer; measuring a drawing velocity of the optical fiber; and adjusting a length of the bare optical fiber from a drawing unit to a coating unit by controlling a position of the direction changer based on a measurement value of the drawing velocity, the drawing unit forming the bare optical fiber, the coating unit providing the coated layer on the periphery of the bare optical fiber.

A method of manufacturing an optical fiber of the invention includes: preparing a direction changer; drawing a bare optical fiber from an optical fiber preform, thereby forming the bare optical fiber; providing a coated layer made of a resin on a periphery of the bare optical fiber; obtaining an optical fiber by curing the coated layer; changing a direction of the bare optical fiber by use of the direction changer; measuring a drawing velocity of the optical fiber; and adjusting a length of the bare optical fiber from a drawing unit to a coating unit by controlling a position of the direction changer based on a measurement value of the drawing velocity, the drawing unit forming the bare optical fiber, the coating unit providing the coated layer on the periphery of the bare optical fiber.

An optical fiber production method includes: drawing an optical fiber from an optical fiber preform in a drawing furnace; cooling the optical fiber in an annealing furnace; and delivering the optical fiber into the annealing furnace, and controlling a temperature difference between a temperature of the optical fiber and a fictive temperature of glass forming a core included in the optical fiber to be higher than 20 C. and lower than 100 C.

A control device which is used in a manufacturing apparatus of an optical fiber, the manufacturing apparatus including a drawing unit and a coating unit. The control device includes: one or a plurality of non-contact holding portions which hold the bare optical fiber at any position between the drawing unit and the coating unit; a position detection unit; and a control unit which controls a flow rate of a fluid introduced into the non-contact holding portion on the basis of the floating position detected by the position detection unit. The non-contact holding portion comprises a guide groove. The control unit detects the floating position of the bare optical fiber at at least one of the non-contact holding portions, compares the detected floating position with a predetermined reference floating position, and controls a flow rate of the fluid introduced into the non-contact holding portions.

A control device which is used in a manufacturing apparatus of an optical fiber, the manufacturing apparatus including: a drawing unit; a coating unit; and a curing unit which cures the coating layer. The control device includes: one or a plurality of direction changing devices which change a direction of the bare optical fiber at any position between the drawing unit and the coating unit; a position detection unit which detects a position of the bare optical fiber in the direction changing device; an outer diameter measurement unit which measures an outer diameter of the bare optical fiber; and a control unit which controls a flow rate of a fluid introduced into the direction changing device on the basis of the position of the bare optical fiber measured by the position detection unit and the outer diameter of the bare optical fiber measured by the outer diameter measurement unit.

Aspects of the embodiments include an optical fiber formed in a low gravity environment. The optical fiber can be used in airframe applications for missile defense, oil-field applications for down-well laser applications, optical communications, and other applications. The optical fiber can include a fluoride composition, such ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN), and can be characterized by an insertion loss in a range from 13 dB/1000 km to 120 dB/1000 km. The optical fiber can deliver optical energy with low insertion loss at the desired power and wavelength for the various applications.

Provided are an optical fiber and a manufacturing method of the optical fiber that can reduce transmission loss even when drawing is performed at a high tension and a high rate. An optical fiber has a core to which chlorine is added and a clad to which fluorine is added, chlorine of 9000 to 13000 ppm is added to the core, a relative refractive index difference 1 of the core to a pure silica glass is 0.09 to 0.13%, a relative refractive index difference 2 of the clad to a pure silica glass is 0.36 to 0.17%, a difference (12) between the relative refractive index difference 1 of the core and the relative refractive index difference 2 of the clad is larger than or equal to 0.30%, a mode field diameter at wavelength 1.31 m is 8.8 to 9.6 m, and a stress difference occurring at an interface between the core and the clad is lower than or equal to 60 MPa.

Provided are an optical fiber and a manufacturing method of the optical fiber that can reduce transmission loss even when drawing is performed at a high tension and a high rate. An optical fiber has a core to which chlorine is added and a clad to which fluorine is added, chlorine of 9000 to 13000 ppm is added to the core, a relative refractive index difference 1 of the core to a pure silica glass is 0.09 to 0.13%, a relative refractive index difference 2 of the clad to a pure silica glass is 0.36 to 0.17%, a difference (12) between the relative refractive index difference 1 of the core and the relative refractive index difference 2 of the clad is larger than or equal to 0.30%, a mode field diameter at wavelength 1.31 m is 8.8 to 9.6 m, and a stress difference occurring at an interface between the core and the clad is lower than or equal to 60 MPa.

There is provided a system and method for manufacturing continuous strand fiberglass of progressive density with varying skins. Glass media is melted into molten glass within a temperature controlled melter, the molten glass exits the melter through orifices of a bushing plate, which is oriented 6 degrees relative to the axis of a rotating drum. A rotating drum receives the molten glass exiting the bushing plate, and resin and water are applied. The fiberglass media is fed through rollers before it enters a curing oven.