Abstract: A glass substrate for a magnetic disk satisfies Ra1?0.8 [nm], 0 [nm]?Ra1?Ra2?0.2 [nm], Wa1?0.6 [nm], and 0 [nm]?Wa2?Wa1?0.2 [nm]. Ra1 is an average surface roughness of a first annular area between 1 mm and 3 mm outward from an inner periphery of a main surface of the glass substrate, Ra2 is an average surface roughness of a second annular area between 1 mm and 3 mm inward from an outer periphery of the main surface, Wa1 is an average waviness of the first area in a circumferential direction of the glass substrate having a cycle of 300 ?m to 5 mm, and Wa2 is an average waviness of the second area in the circumferential direction having a cycle of 300 ?m to 5 mm.

Abstract: A main surface of a glass substrate for a magnetic disk is disk-shaped and has a ski jump on an outer peripheral end portion of the main surface opposing a magnetic head slider to be loaded. A rate of change of angles of tangents to a slope of the ski jump in a radial direction in a range between an inner circumferential side and a transition point on the slope is equal to or less than 10/W ?rad/mm where W is a width of the magnetic head slider.

Abstract: The linear semiconductor substrate 1 or 2 of the present invention comprises at least one desired thin film 4 formed on a linear substrate 3 having a length ten or more times greater than a width, thickness, or diameter of the linear substrate itself. Adopting semiconductor as the thin film 4 forms a linear semiconductor thin film. The linear semiconductor substrate 1 or 2 of the present invention is produced by utilizing a fiber-drawing technique which is a fabricating technique of optical fibers.

Abstract: An optical fiber preform (1) serving as a material of an optical fiber has a shoulder portion (12) thrusting beyond a middle portion (M) in a base end region (K) which is on the upper side when the optical fiber preform is suspended for a drawing process. The optical fiber preform (1) of this configuration can be easily produced by appropriately setting the heating condition, etc. for the sintering step in the production process. Thus, it is possible to omit the elongating step after the sintering step, thereby simplifying the production process. Further, in the prior-art technique, turbulence is generated in the gas flow in the furnace of the drawing apparatus toward the end of the drawing step, making it impossible to draw in a stable manner.

Abstract: A porous layer is formed by depositing a silica glass particle around a core rod. The porous layer is dehydrated. The dehydrated porous layer is sintered under a decreased pressure until the dehydrated porous layer becomes a translucent glass layer containing a closed pore. The translucent glass layer is vitrified under an ambient atmosphere including an inert gas other than a helium gas.

Abstract: An optical fiber preform (1) serving as a material of an optical fiber has a shoulder portion (12) thrusting beyond a middle portion (M) in a base end region (K) which is on the upper side when the optical fiber preform is suspended for a drawing process. The optical fiber preform (1) of this configuration can be easily produced by appropriately setting the heating condition, etc. for the sintering step in the production process. Thus, it is possible to omit the elongating step after the sintering step, thereby simplifying the production process. Further, in the prior-art technique, turbulence is generated in the gas flow in the furnace of the drawing apparatus toward the end of the drawing step, making it impossible to draw in a stable manner.

Abstract: An optical fiber preform (1) serving as a material of an optical fiber has a shoulder portion (12) thrusting beyond a middle portion (M) in a base end region (K) which is on the upper side when the optical fiber preform is suspended for a drawing process. The optical fiber preform (1) of this configuration can be easily produced by appropriately setting the heating condition, etc. for the sintering step in the production process. Thus, it is possible to omit the elongating step after the sintering step, thereby simplifying the production process. Further, in the prior-art technique, turbulence is generated in the gas flow in the furnace of the drawing apparatus toward the end of the drawing step, making it impossible to draw in a stable manner.

Abstract: A device for continuously twisting an optical fiber, which can add a sufficient twist to an optical fiber, is provided. Reciprocating rollers reciprocate so that the moving direction would be opposite each other along a center axis of rotation. The optical fiber passes through a gap between the reciprocating rollers and runs in contact with the outer circumferential surface of respective reciprocating rollers in order. Reciprocation of the reciprocating rollers adds a twist to the optical fiber. When &phgr; is a contacting angle between the optical fiber and the reciprocating rollers, F is maximum static friction of the optical fiber against the outer circumferential surface of the reciprocating rollers, and T is tension of the optical fiber, the coefficient of friction &mgr; between the optical fiber and the outer circumferential surface of the reciprocating rollers is lead from an operational formula of &mgr;=(1/&phgr;)·ln(F/T).

Abstract: A method for fiber drawing of an optical fiber, which method comprises:

Abstract: A porous optical fiber preform dehydration and sintering apparatus capable of improving the sealing performance between an upper lid and an elevating shaft and between the upper lid and a furnace tube or a furnace body, wherein an upper opening of a furnace tube for accommodating a porous optical fiber preform is shut by the upper lid, a preform holder is provided at the bottom end of an elevating shaft passing through the upper lid to be freely elevated therethrough, the porous optical fiber preform in the furnace tube is heated by a heater provided around the outer circumference of the furnace tube, the upper lid is formed by a metal, the preform holder is formed by a quartz glass or a ceramic, a corrosion-resistant layer is provided on an inner surface of the upper lid, a seal member made of rubber or resin is provided in an elevating shaft passage of the upper lid.

Abstract: An optical fiber preform (1) serving as a material of an optical fiber has a shoulder portion (12) thrusting beyond a middle portion (M) in a base end region (K) which is on the upper side when the optical fiber preform is suspended for a drawing process. The optical fiber preform (1) of this configuration can be easily produced by appropriately setting the heating condition, etc. for the sintering step in the production process. Thus, it is possible to omit the elongating step after the sintering step, thereby simplifying the production process. Further, in the prior-art technique, turbulence is generated in the gas flow in the furnace of the drawing apparatus toward the end of the drawing step, making it impossible to draw in a stable manner.

Abstract: There is provided an optical-fiber resin coating device which can uniformly coat resin on an optical fiber at a high fiber-pulling velocity while preventing thickness deviation, outer-diameter variation and breaking of the optical fiber. The optical-fiber resin coating device includes a coating die (2N) with a coating die hole (6N) having at least a taper hole portion (6Na) and a land hole portion (6Nb), a nipple (1) having a nipple hole (5), and at least one intermediate die (2A) disposed between the coating die (2N) and the nipple (1) and having an intermediate die hole (6A). The inner diameter of the intermediate die hole (6A) of the intermediate die (2A) is smaller than the inner diameter of the inlet of the taper hole portion (6Na) of the coating die (2N) and equal to 1.

Abstract: An optical fiber drawing furnace, comprising a furnace core tube where an optical fiber preform is inserted, fused with heat by a cylindrical heating element that is provided around the furnace core tube, and drawn to an optical fiber, wherein a protective tube is provided being contacted with an upper end edge of the furnace core tube.

Abstract: A device for continuously twisting an optical fiber, which can add a sufficient twist to an optical fiber, is provided. Reciprocating rollers reciprocate so that the moving direction would be opposite each other along a center axis of rotation. The optical fiber passes through a gap between the reciprocating rollers and runs in contact with the outer circumferential surface of respective reciprocating rollers in order. Reciprocation of the reciprocating rollers adds a twist to the optical fiber. When &phgr; is a contacting angle between the optical fiber and the reciprocating rollers, F is maximum static friction of the optical fiber against the outer circumferential surface of the reciprocating rollers, and T is tension of the optical fiber, the coefficient of friction &mgr; between the optical fiber and the outer circumferential surface of the reciprocating rollers is lead from an operational formula of &mgr;=(1/+)·In(F/T).

Abstract: An optical fiber resin coating apparatus including: a nipple including a nipple hole, and a resin reserving chamber for reserving resin, a meniscus-shaped portion being positioned at an end of the nipple hole; a resin coating die including a tapered-hole and a land portion continued to the tapered-hole and defining a hole of a diameter which defines a diameter of a resin coated optical fiber; and an intermediate die provided between the nipple and the resin coating die, including a hole communicating the meniscus-shaped portion and the second tapered-hole, a hole communicating to the resin reserving chamber. A first resin flow path is defined at a boundary portion of the nipple and the intermediate die. A second resin flow path is defined at a boundary portion of the intermediate die and the resin coating die.

Abstract: An optical fiber drawing furnace capable of the prevention of entry of an ambient gas into an inner space thereof both effectively and economically, provided with a lower gas introduction portion through which inert gas is introduced into the inner space of the optical fiber drawing furnace, a chamber separated by a lower partition, and a bottom cover. The lower partition is arranged immediately below the lower gas introduction portion and has a first hole through which the chamber and the inner space are communicated. The bottom cover has a second hole through which the chamber and the atmosphere are communicated. An optical fiber is passed through the first and second holes. A controller detects a differential pressure between a pressure P1 in the inner space and a pressure P2 in the chamber and controls the suction flow by a pump for evacuating the gas in the chamber to maintain P1>P2.

Abstract: An optical fiber coating apparatus which has a left holder unit 13a and a right holder unit 13b, in the left holding space 12a and right holding space 12b defined in those units are housed a second layer die 16a, 16b, a first layer die 17a, 17b, and a nipple 18a, 18b in a superposed state. The second layer die 16a, 16b and the first layer die 17a, 17b and the nipple 18a, 18b have block shaped planar outer contour shapes and the holding space 12a, 12b housing these also has a block shaped planar outer contour shape. Since the outer shapes of the dies 16a, 16b and 17a, 17b and the nipple 18a, 18b and the holding space 12a, 12b are all block shaped, it is easy to perform the axial alignment of the holes 30, 31, and 32 through which the optical fiber passes by pressing the die 16a, 16b, the die 17a, 17b, and the nipple 18a, 18b against the reference surfaces 19, 21 of the left holding space 12a.