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.

The application provides a method for automatically processing a conical tip of an optical fiber preform, including: step 10: suspending an optical fiber preform requiring conical tip processing on a suspension component, where the optical fiber preform moves downward vertically along with the suspension component; step 20: arranging a furnace body below the suspension component, where a preset depth is set inside the furnace body, and after the optical fiber preform moves to the preset depth inside the furnace body, the furnace body is heated; step 30: arranging an automatic cutting component below the furnace body, where a preset temperature is set inside the furnace body, after a temperature inside the furnace body reaches the preset temperature, a bottom of the furnace body is opened to make the optical fiber preform melt to form a conical tip, and the automatic cutting component cuts the molten conical tip.

Provided is an optical fiber glass preform, in a preliminary step of a final drawing step, in which the optical fiber glass preform is undergone one or more drawing steps to be drawn to a final target diameter, wherein as an outer diameter of an effective portion of the glass preform is continuously measured in a longitudinal direction, and from outer diameter measurement results obtained, a regression line of y=ax+b is obtained using the least squares method with y as the outer diameter and x as a length, an absolute value of a slope a is less than or equal to 0.005 mm/mm; and a maximum value of an obtained absolute value of a curvature of the outer diameter at any given point, in the outer diameter measurement results obtained, is 0.003 or less.

An optical fiber preform includes: a columnar portion having an approximately constant radius of r; and a taper portion located adjacent to the columnar portion in a lengthwise direction and having a radius decreasing along the lengthwise direction. The taper portion includes: a first taper portion including a portion having a radius varying between 0.9r and 0.6r; and a second taper portion including a portion having a radius varying between 0.4r and 0.15r. A diameter of the first taper portion in the portion having the radius varying between 0.9r and 0.6r decreases so as to form a maximum angle θ1 between 40 degrees and 60 degrees with respect to the columnar portion, a diameter of the second taper portion in the portion having the radius varying between 0.4r and 0.15r decreases so as to form an average angle θ2 between 5 degrees and 30 degrees with respect to a central axis in the lengthwise direction, and a volume of the taper portion is smaller than or equal to 45% of a volume of a column having a same outer diameter as a maximum outer diameter of the taper portion and having a same length as the taper portion.

Provided is an elongating method for elongating a glass base material by heating the same while moving the same downward within an elongating apparatus, the glass base material including a transparent tapered section, wherein the transparent tapered section is located at an upper end of the glass base material and has an end face to which a suspension dummy formed from a glass pole is welded, the elongating method comprising steps for: starting to elongate the glass base material by heating the same, starting from a lower-end side thereof, by causing the glass base material to pass through a range within the elongating apparatus in which a preset elongating process temperature or higher is maintained; and after the tapered section enters the range, ending the elongating of the glass base material before the end face enters the range.

In a method of forming a conical shape on a glass rod including an effective portion and an ineffective portion adjoining the effective portion to form a conical shape in the effective portion by simultaneously heating a boundary and the vicinity of the boundary between the effective portion and the ineffective portion and pulling an end of the ineffective portion, the temperature of a heater is raised and a heating target on the glass rod is simultaneously moved from the ineffective portion to the boundary.

There is provided a method for producing a multicore optical fiber while reducing the mass of a glass block to be connected to a common cladding tube. A production method for a multicore optical fiber includes in order, a preform forming step of forming a common cladding tube having a plurality of holes extending between a first end and a second end, an insertion step of inserting core rods in the holes in a state in which end portions of the core rods are recessed from the first end, a heat shrinkage step of reducing a diameter of the first end by heating, a sealing step of sealing the holes by connecting a glass block to the first end, and a drawing step of depressurizing insides of the holes from the second end and performing spinning from the first end while combining the common cladding tube and the core rods.

The fabrication of sleeveless canes utilizes a preform with an array of glass canes in the preform. At least one tube-sleeve encircles the array of glass canes and is secured to the array of glass canes. The array of glass canes is moved into a furnace wherein the array of glass canes is heated. The furnace is maintained at a furnace temperature within the range of 2000 C. to 1700 C. and the array of glass canes is drawn from the furnace. The drawing of the array of glass canes both scales down the glass canes and elongates the glass canes. Maintaining the furnace at a furnace temperature within the range of 2000 C. to 1700 C. assures that the array of glass canes and the glass canes maintain their original shape.

Provided is an elongating method for elongating a glass base material by heating the same while moving the same downward within an elongating apparatus, the glass base material including a transparent tapered section, wherein the transparent tapered section is located at an upper end of the glass base material and has an end face to which a suspension dummy formed from a glass pole is welded, the elongating method comprising steps for: starting to elongate the glass base material by heating the same, starting from a lower-end side thereof, by causing the glass base material to pass through a range within the elongating apparatus in which a preset elongating process temperature or higher is maintained; and after the tapered section enters the range, ending the elongating of the glass base material before the end face enters the range.

There is provided a method for producing a multicore optical fiber while reducing the mass of a glass block to be connected to a common cladding tube. A production method for a multicore optical fiber includes in order, a preform forming step of forming a common cladding tube having a plurality of holes extending between a first end and a second end, an insertion step of inserting core rods in the holes in a state in which end portions of the core rods are recessed from the first end, a heat shrinkage step of reducing a diameter of the first end by heating, a sealing step of sealing the holes by connecting a glass block to the first end, and a drawing step of depressurizing insides of the holes from the second end and performing spinning from the first end while combining the common cladding tube and the core rods.