Abstract: An optical fiber producing method and apparatus for producing an optical fiber in which, in a path where an optical fiber is reeled out from a supply bobbin, taken up by take-up means, and wound by a winding bobbin, twists are alternately imparted to the optical fiber by a twist imparting portion. A zone where a high tension load is allowed to be applied to the optical fiber without affecting winding tension of the winding bobbin is disposed, a twist is imparted in the zone, and, when tension immediately before the twist imparting portion is indicated by T (g), a free path length is indicated by L, a twisting amount is indicated by R (turns/m), and a and b are constants, the tension and free path length by which the twisting amount R approximated by “R=a×T×Lb” is made “2” or more are set.

Abstract: Simple and small-sized equipment which continuously afford alternate twists to an optical fiber and a method using the apparatus are provided. The equipment includes: a guide roller for causing the fiber to roll; a roller supporting member for holding the roller in a manner allowing the roller to freely turn about an axial center X; and a driving unit to cause the roller to oscillate by making the supporting member to turn about an axial center Y that is inclined relative to the axial center X. The method includes: arranging a guide roller to intersect the fiber, the roller being held by a roller supporting member to freely turn about an axial center X; oscillating the roller by driving the supporting member to revolve about the axial center Y which is inclined relative to the axis center X; and causing the fiber to roll to afford alternate twists to the fiber.

Abstract: An optical fiber producing method and apparatus are provided in which sufficient pulling tension is applied to an optical fiber to enhance the twisting efficiency without affecting winding tension of a winding bobbin, whereby the PMD of the optical fiber can be reduced.

Abstract: Simple and small-sized equipment which continuously afford alternate twists to an optical fiber and a method using the apparatus are provided. The equipment includes: a guide roller for causing the fiber to roll; a roller supporting member for holding the roller in a manner allowing the roller to freely turn about an axial center X; and a driving unit to cause the roller to oscillate by making the supporting member to turn about an axial center Y that is inclined relative to the axial center X. The method includes: arranging a guide roller to intersect the fiber, the roller being held by a roller supporting member to freely turn about an axial center X; oscillating the roller by driving the supporting member to revolve about the axial center Y which is inclined relative to the axis center X; and causing the fiber to roll to afford alternate twists to the fiber.

Abstract: To provide a method and apparatus for parting a glass rod without causing a crack or rupture at a grasped root portion of the glass rod in parting the glass rod for producing a glass preform. The apparatus for parting the glass rod in a predetermined length by grasping both ends of the glass rod 11 is characterized by comprising a supporting unit 18 of Y-character shape for supporting an intermediate position between both ends of the glass rod 11 from the lower part, the supporting unit 18 having a carbon sleeve composed of a cylindrical body that is rotatable around each of two leg portions making up a forked leg portion as an axis, the carbon sleeve being rotatable along with an axial movement of the glass rod.

Abstract: To provide a method and apparatus for parting a glass rod without causing a crack or rupture at a grasped root portion of the glass rod in parting the glass rod for producing a glass preform.

Abstract: The present invention relates to a process for producing a porous glass preform for an optical fiber and an apparatus for conducting such a process. According to the process, fine glass particles are produced by heating and reacting vaporous starting materials in a reaction vessel. The resulting fine glass particles are thereafter deposited to obtain the porous glass preform. An exhaust gas containing non-deposited fine glass particles is exhausted through an exhaust duct at a velocity above 15 m/sec. Preferably, pressure fluctuation in the reaction vessel is minimized by supplying air from outside of the reaction vessel to the exhaust duct. In accordance with the present invention, the exhaust duct is less likely to become obstructed by non-deposited fine glass particles. As a result, the preform can be produced without interruption over an extended period of time.

Abstract: This invention relates to a sintering furnace for the production of a quartz preform which can be used for carrying out dehydration, fluorine-addition and/or sintering of a porous quartz soot preform prepared by a flame hydrolysis method such as a VAD method or a OVD method, and in particular, to such a furnace in which joints in a long furnace muffle so long that fabricating it as open body is impossible can be maintained fully gas-tight, so that it is possible to prevent H.sub.2 O, O.sub.2 and other impurities in the air from entering the muffle from outside, and corrosive and poisonous gases in the muffle are prevented from leakage to outside the muffle.

Abstract: A device is disclosed for supplying a glass raw material gas in the form of the mixed gas consisting of the glass raw material gas and the carrier gas to a vapor deposition device for producing a preform of an optical fiber, the supply device including a secondary raw material container having a pressurizable interior and provided adjacent to a main raw material container. The bottoms, or areas near the bottoms, of the two containers are interconnected via a pipe including at a mid portion thereof a switching valve and a device for adjusting the flow rate of the raw material liquid between the two containers. Liquid level detectors are provided in one or both containers to maintain the constant volume of the liquid raw material so as to provide a constant state inside the main raw material container. The operation of this device can easily be entirely automated.