A method for producing a depressed-cladding core rod of an ultra-low water peak optical fiber, the method including 1) producing a core rod component; 2) producing an inner cladding casing component; 3) disposing the core rod hollow shaft and the casing hollow shaft respectively in the glass lathe; 4) cutting off connections among a pressure controlling pipe, a scrubber, and a vacuum pump; 5) connecting the inner cladding casing to the core rod hollow shaft hermetically; 6) turning on the glass lathe; 7) transporting a first mixture gas to the core rod hollow shaft; 8) moving a high temperature heat source; 9) transporting a second mixture gas to the core rod hollow shaft; 10) transporting the first mixture gas to the core rod hollow shaft; 11) transporting the first mixture gas under certain conditions; and 12) controlling relevant parameters to fuse the inner cladding casing with the core layer rod.

Methods are known for producing an anti-resonant hollow-core fiber which has a hollow core extending along a fiber longitudinal axis and an inner jacket region that surrounds the hollow core, said jacket region comprising multiple anti-resonant elements. The known methods have the steps of: providing a cladding tube that has a cladding tube inner bore and a cladding tube longitudinal axis along which a cladding tube wall extends that is delimited by an interior and an exterior; providing a number of tubular anti-resonant element preforms; arranging the anti-resonant element preforms at target positions of the interior of the cladding tube wall, thereby forming a primary preform which has a hollow core region and an inner jacket region; and elongating the primary preform in order to form the hollow-core fiber or further processing the primary preform in order to form a secondary preform. The aim of the invention is to achieve a high degree of precision and an exact positioning of the anti-resonant elements in a sufficiently stable and reproducible manner on the basis of the aforementioned methods. This is achieved in that a secondary preform is formed which has an outer diameter ranging from 30 to 90 mm, and at least one of the end faces of the anti-resonant element preforms is closed prior to drawing the fiber.

An optical fiber manufacturing apparatus includes: a drawing furnace configured to heat and fuse an optical fiber preform and draw the optical fiber preform to obtain a glass fiber; a cooling device configured to cool the glass fiber; and at least one preliminary chamber provided at an upper end of the cooling device. The optical fiber manufacturing apparatus further includes: a hydrogen gas supply device configured to supply hydrogen gas into the cooling device; and an inert gas supply device configured to supply inert gas into the at least one preliminary chamber.

A method of producing an optical fiber preform includes: an alkali-metal-doped silica glass body forming step of forming an alkali-metal-doped silica glass body doped with an alkali metal; a silica glass body forming step of forming a silica glass body to be at least a portion of a core portion around the alkali-metal-doped silica glass body such that the silica glass body contacts the alkali-metal-doped silica glass body; and a diffusing step of diffusing the alkali metal from the alkali-metal-doped silica glass body to the silica glass body by a heat treatment.

A method for producing a depressed-cladding core rod of an ultra-low water peak optical fiber, the method including 1) producing a core rod component; 2) producing an inner cladding casing component; 3) disposing the core rod hollow shaft and the casing hollow shaft respectively in the glass lathe; 4) cutting off connections among a pressure controlling pipe, a scrubber, and a vacuum pump; 5) connecting the inner cladding casing to the core rod hollow shaft hermetically; 6) turning on the glass lathe; 7) transporting a first mixture gas to the core rod hollow shaft; 8) moving a high temperature heat source; 9) transporting a second mixture gas to the core rod hollow shaft; 10) transporting the first mixture gas to the core rod hollow shaft; 11) transporting the first mixture gas under certain conditions; and 12) controlling relevant parameters to fuse the inner cladding casing with the core layer rod.

The present invention intends to reduce unevenness on a surface of an optical fiber preform. The apparatus for manufacturing an optical fiber preform including a support portion rotating a core rod at a rotation speed r around a rotation axis of the core rod extending in a longitudinal direction of the core rod and at least one burner array including N sets (N is an integer of 2 or more) of burners provided at intervals of a distance d and a material ejection port, and moving around the core rod at a speed v in the longitudinal direction to form a porous glass portion on an outer periphery of the core rod. A rotation number (L+x) of the core rod when the burner array moves the distance d in the longitudinal direction is represented by rd/v=L+x where the L is an arbitrary natural number and the offset x is greater than 0.5 and less than or equal to 0.5, an absolute value of the offset x is greater than 2/(2N+1) and less than 3/(3N1).

A system and methods are described herein for preheating a preform in a preheater furnace and then transferring the preheated preform to a consolidation furnace for chemical treatment and sintering the preform into a clear glass which can be drawn into optical fiber. In addition, the preheater furnace is described herein which is configured to heat the preform per a predetermined heat-profile until the preform is uniformly heated to a temperature above 1000 C.

An optical fiber manufacturing method includes supplying power to a drawing furnace to cause T/V to decrease to T.sub.target/V.sub.target along a quadratic function having a value of the T.sub.target/V.sub.target at an apex with lapse of time, where T is a tension applied to an optical fiber when an optical fiber preform is heated by the drawing furnace and the optical fiber is drawn, V is speed of withdrawing the optical fiber when the optical fiber is heated by the drawing furnace and the optical fiber is drawn, T.sub.target is a target value of the tension, and V.sub.target is a target value of the speed.