An optical fiber manufacturing method includes: a drawing step of heating one end portion of an optical fiber preform to melt and deform the one end portion and drawing an optical fiber, wherein in the drawing step, drawing is performed while applying pressure to a melted-deformed portion that is melted and deformed.

An optical fiber draw system and method of operating thereof. The method includes positioning a downfeed handle for supporting an optical fiber preform within a furnace such that the downfeed handle is movable within the furnace. The method further includes operating one or more heating elements to thermally heat at least a portion of an upper muffle extension disposed within the furnace, the one or more heating elements being moveable with the downfeed handle.

An optical fiber draw system and method of operating thereof. The method includes positioning a downfeed handle for supporting an optical fiber preform within a furnace such that the downfeed handle is movable within the furnace. The method further includes operating one or more heating elements to thermally heat at least a portion of an upper muffle extension disposed within the furnace, the one or more heating elements being moveable with the downfeed handle.

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.

Aspects of the embodiments are directed to systems and methods for forming an optical fiber in a low gravity environment, and an optical fiber formed in a low gravity environment. The system can include a preform holder configured to secure a preform; a heating element secured to a heating element stage and residing adjacent the preform holder; a heating element stage motor configured to move the heating element stage; a tension sensor; a spool; a spool tension motor coupled to the spool and configured to rotate the spool; and a control system communicably coupled to the heating element stage motor and the spool tension motor and configured to control the movement of the heating element stage based on a rotational speed of the spool. 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.

A furnace system includes a muffle defining a furnace cavity. A lower heater is coupled to the muffle and is configured to create a hot zone within the furnace cavity having a temperature of about 1900° C. or greater. An upper muffle extension is positioned above the muffle and defines a handle cavity. A downfeed handle is positioned within the handle cavity such that a gap is defined between an outer surface of the downfeed handle and an inner surface of the upper muffle extension. An upper heater is thermally coupled to the upper muffle extension and configured to heat the gap. A gas screen is positioned in the upper muffle extension and is configured to inject a process gas into the handle cavity.

Provided is a method of fabricating an optical fiber glass base material, the method including a first step for dehydrating an optical fiber porous base material while causing a gas that includes at least a halogen or argon to distribute within a quartz core tube that accommodates the optical fiber porous base material; a second step for, after the first step, at least partially ventilating within the quartz core tube by causing a gas having helium as a main component to distribute within the quartz core tube; and a third step for, after the second step, transparently vitrifying the optical fiber porous base material while causing the gas having helium as a main component to distribute within the quartz core tube.

An optical fiber forming apparatus comprises: a draw furnace comprising: (i) a muffle with an inner surface, (ii) an axial opening below the muffle, the inner surface of the muffle defining a passageway extending through the axial opening, and (iii) an upper inlet into the passageway; and a tube that extends into the passageway of the draw furnace above the axial opening, the tube having (i) an outer surface and the inner surface of the muffle surrounds the outer surface of the tube with a space separating the outer surface of the tube from the inner surface of the muffle, (ii) an inner surface that defines a second passageway extending through the tube, (iii) an inlet into the second passageway of the tube, (iii) an outlet out of the second passageway of the tube.

A method for manufacturing an optical fiber includes: heating an optical fiber preform to draw glass fiber; measuring an outer diameter of the glass fiber to obtain a function of time; transforming the function of time into a function of frequency; identifying a first peak caused by a first drawing condition and a second peak caused by a second drawing condition in the function of frequency; and adjusting the second drawing condition so as to satisfy fn<fm−wm/2 or fn>fm+wm/2, where fm is a frequency of the first peak, wm is a full width at half maximum of the first peak, and fn is a frequency of the second peak.

A furnace system includes a muffle defining a furnace cavity. A lower heater is coupled to the muffle and is configured to create a hot zone within the furnace cavity having a temperature of about 1900° C. or greater. An upper muffle extension is positioned above the muffle and defines a handle cavity. A downfeed handle is positioned within the handle cavity such that a gap is defined between an outer surface of the downfeed handle and an inner surface of the upper muffle extension. An upper heater is thermally coupled to the upper muffle extension and configured to heat the gap. A gas screen is positioned in the upper muffle extension and is configured to inject a process gas into the handle cavity.