Abstract: A method of manufacturing an optical fiber includes a first step of drawing an optical fiber preform into a glass fiber and disposing a fiber coating on the outer circumference of the glass fiber to form a parent optical fiber; a second step of cutting the parent optical fiber into a plurality of individual optical fibers; a third step of determining, at, at least, one spot of the parent optical fiber, a failure strength F1 and a failure time T; a fourth step of determining a failure strength F2 of each of the individual optical fibers; and a fifth step of selecting an optical fiber having a failure strength F2 of 5.5 kgf or more from the individual optical fibers cut from the parent optical fiber whose failure strength F1 and failure time T satisfy the inequality T>2.6×10?11×exp(4.736×F1).

Abstract: An optical fiber having excellent strength that can be manufactured at low cost, as well as a method for making such optical fiber, is provided. An optical fiber 1 is a silica-based optical fiber comprising a core 11, an optical cladding 12 surrounding the core & 11, and a jacketing region 13 surrounding the optical cladding 12 and having a uniform composition throughout from the internal circumference to the outer circumference. A compressive strained layer having a residual compressive stress is provided at the outermost circumference of the jacketing region 13.

Abstract: A trench optical fiber that stably realizes a small transmission loss includes (1) a core extending in an axial direction while containing an axial center of the fiber, the core having a diameter d1 of 7.0 ?m to 7.4 ?m; (2) a first optical cladding layer surrounding the core and having an outside diameter d2 of 1.67d1 to 2.5d1; (3) a second optical cladding layer surrounding the first optical cladding layer; and (4) a jacket layer surrounding the second optical cladding layer and containing fluorine having a concentration of 0.06 wt % or higher. A relative refractive index difference ?1 of the core with respect to the jacket layer is 0.31% to 0.37%. A relative refractive index difference ?2 of the first optical cladding layer with respect to the jacket layer is +0.02% or larger and smaller than ?1. A relative refractive index difference ?3 of the second optical cladding layer with respect to the jacket layer is ?0.2% or smaller.

Abstract: Provided is an inexpensive low-loss optical fiber suitably used in an optical transmission network. An optical fiber includes a core, an optical cladding, and a jacket. The core has a relative refractive index difference between 0.2% and 0.32% and has a refractive index volume between 9%·?m2 and 18%·?m2. The jacket has a relative refractive index difference between 0.03% and 0.20%. Glass constituting the core has a fictive temperature between 1400° C. and 1560° C. Stress remaining in the core is compressive stress. A cutoff wavelength measured on a fiber having a length of 2 m is 1300 nm or more and a cutoff wavelength measured on a fiber having a length of 100 m is 1500 nm or less. An effective area at a wavelength of 1550 nm is 110 ?m2 or more. A attenuation at a wavelength of 1550 nm is 0.19 dB/km or less.

Abstract: An optical fiber having excellent strength that can be manufactured at low cost, as well as a method for making such optical fiber, is provided. An optical fiber 1 is a silica-based optical fiber comprising a core 11, an optical cladding 12 surrounding the core 11, and a jacketing region 13 surrounding the optical cladding 12 and having a uniform composition throughout from the internal circumference to the outer circumference. A compressive strained layer having a residual compressive stress is provided at the outermost circumference of the jacketing region 13.

Abstract: An inexpensive low-attenuation optical fiber 1 suitable for use as an optical transmission line in an optical access network is a silica based glass optical fiber and includes a core 11 including the center axis, an optical cladding 12 surrounding the core, and a jacket 13 surrounding the optical cladding. The core contains GeO2 and has a relative refractive index difference ?core, based on the optical cladding, greater than or equal to 0.35% and less than or equal to 0.50% and has a refractive index volume v greater than or equal to 0.045 ?m2 and less than or equal to 0.095 ?m2. The jacket has a relative refractive index difference ?J greater than or equal to 0.03% and less than or equal to 0.20%. Glass constituting the core has a fictive temperature higher than or equal to 1400° C. and lower than or equal to 1590° C. Residual stress in the core is compressive stress that has an absolute value greater than or equal to 5 MPa.

Abstract: A multi-core optical fiber 1A in which a plurality of cores can easily be identified even in the case where they are symmetrically arranged in its section has seven cores 10 to 16, a visual recognition marker 20, and a shared cladding 30 enclosing the seven cores 10 to 16 and the visual recognition marker 20. The cores 10 to 16, the visual recognition marker 20, and the cladding 30 are respectively made of silica glass as their main element. The cores 10 to 16 and the visual recognition marker 20 extend along the fiber-axis direction. The respective refractive index of the cores 10 to 16 is higher than the refractive index of the cladding 30. The refractive index of the visual recognition marker 20 differs from that of the cladding 30. In the cross-section perpendicular to the fiber-axis, the cores 10 to 16 are arranged such that they have 6-fold rotational symmetry and line symmetry. The visual recognition marker 20 is arranged at a position which breaks such symmetry.

Abstract: The present invention is to provide a method for producing duplex stainless steel seamless pipe in which a duplex stainless steel billet can be inhibited from generating an oxide scale on the surface thereof during heating and the generation of outer surface flaw can also be prevented. The billet is heated in the a heating furnace for 1.5 hours or more and 4.0 hours or less at a heating temperature of 1250° C. or more and 1320° C. or less while regulating the average concentration of sulfur dioxide (SO2) gas in the atmosphere within the furnace to 0.01 volume % or less.

Abstract: To provide phosphorus-containing epoxy resins and phosphorus-containing epoxy resin compositions having high levels of appearance, yield and economic efficiency and cured products thereof that are used for various applications. A phosphorus-containing phenol compound represented by Formula (3) obtained by reacting a compound represented by Formula (2) with a compound represented by Formula (1), wherein in the peak area (A) of the component represented by Formula (1) on a chromatogram measured under specific conditions by gel permeation chromatography, peak area (B) on the high-molecular-weight side of the component of Formula (1), and total area (C) of peak area (A) and peak area (B), the value obtained by dividing peak area (B) by total area (C) is 8 area % or less, and epoxy resin compositions and cured products comprising the phosphorus-containing phenol compound as an essential ingredient.

Abstract: A method for accurately measuring the cutoff wavelength of a high order mode of an optical fiber includes a first step of measuring power spectrum P1(?) of light output from a light source; a second step of measuring power spectrum P2(?) of light emitted from one end of a test fiber when light output from the light source is made incident on the other end of the test fiber placed in a form (preferably spiral) allowing the curvature to vary in the longitudinal direction thereof; a third step of obtaining difference spectrum P(?) representing the difference between the power spectrum P2(?) and the power spectrum P1(?); and a fourth step of obtaining the cutoff wavelength of a high order mode of the test fiber on the basis of the difference spectrum P(?).

Abstract: A method of coating uses an anti-seizure agent for hot steel working that exhibits excellent wettability and surface film-adherability. The agent comprises: an inorganic component (first component); sodium hydroxide (second component); water-soluble resins and/or water-soluble surfactants (third component); and water. With the sum of the first component, the second component, and the third component as 100 mass %, the anti-seizure agent contains: 96.5 mass % or more and 99.98 mass % or less of the first component; 0.01 mass % or more and 2.0 mass % or less of the second component; and 0.01 mass % or more and 1.5 mass % or less of the third component, and the inorganic component is one or more selected from a group consisting of Al2O3, SiO2, CaO, B2O3, K2O, and Na2O. A coating layer formed solidly adheres to the steel and does not come off in both cold and hot working.

Abstract: There is provided an optical transmission line that includes a bend insensitive fiber (BIF) defined by ITU-T Recommendation G.657 and that reduces the influence of MPI. An optical transmission line 1 includes a first optical fiber 11, a second optical fiber 12 joined to an incident end of the first optical fiber 11, and a third optical fiber 13 joined to an exit end of the first optical fiber 11. The first optical fiber 11 is a bend insensitive fiber (BIF), and each of the second optical fiber 12 and the third optical fiber 13 is a general single mode optical fiber. An attenuation coefficient of an LP11 mode in the first optical fiber 11 at a wavelength of 1310 nm, a splice loss between the first optical fiber and the second optical fiber, a splice loss between the first optical fiber and the third optical fiber, and a length of the first optical fiber satisfy a predetermined relational equation.

Abstract: A trench optical fiber that stably realizes a small transmission loss includes (1) a core extending in an axial direction while containing an axial center of the fiber, the core having a diameter d1 of 7.0 ?m to 7.4 ?m; (2) a first optical cladding layer surrounding the core and having an outside diameter d2 of 1.67 dl to 2.5 dl; (3) a second optical cladding layer surrounding the first optical cladding layer; and (4) a jacket layer surrounding the second optical cladding layer and containing fluorine having a concentration of 0.06 wt % or higher. A relative refractive index difference ?1 of the core with respect to the jacket layer is 0.31% to 0.37%. A relative refractive index difference ?2 of the first optical cladding layer with respect to the jacket layer is +0.02% or larger and smaller than ?1. A relative refractive index difference ?3 of the second optical cladding layer with respect to the jacket layer is ?0.2% or smaller.

Abstract: A method of manufacturing an optical fiber includes a first step of drawing an optical fiber preform into a glass fiber and disposing a fiber coating on the outer circumference of the glass fiber to form a parent optical fiber; a second step of cutting the parent optical fiber into a plurality of individual optical fibers; a third step of determining, at, at least, one spot of the parent optical fiber, a failure strength F1 and a failure time T; a fourth step of determining a failure strength F2 of each of the individual optical fibers; and a fifth step of selecting an optical fiber having a failure strength F2 of 5.5 kgf or more from the individual optical fibers cut from the parent optical fiber whose failure strength F1 and failure time T satisfy the inequality T>2.6×10?11×exp(4.736×F1).

Abstract: The present invention relates to an optical fiber preform fabricating method that makes it possible to implement a reduction in iron impurities at a low cost. The optical fiber preform fabricating method comprises a glass synthesis step for forming a glass region constituting at least a part of the core area of the optical fiber. The glass synthesis step includes a deposition step of depositing glass particles containing the Al-element inside the glass pipe by means of chemical vapor deposition, and a consolidation step of obtaining a transparent glass body from the glass soot body thus obtained. In other words, the deposition step synthesizes glass particles on the inside wall of a glass pipe by feeding raw material gas, in which the content ratio (O/Al) of the O-element and Al-element is 20 or less, into the glass pipe. Furthermore, the consolidation step obtains a transparent glass body from the glass soot body by heating the glass soot body.

Abstract: Apparatus and methods for making an optical fiber preform at low cost avoiding the apparatus from being damaged are provided. Apparatus for making an optical fiber preform by depositing glass particles on the circumferential surface of a glass rod comprises: a chamber, a plasma torch, a glass particle supplying part, a composition modification gas supplying part, and an exhaust part. The chamber surrounds the heating portion of the glass rod heated by the plasma torch. The plasma torch heats the glass particles by a plasma flame. The glass particle supplying part introduces glass particles towards the heating portion of the glass rod in the chamber. The composition modification gas supplying part introduces composition modification gas into the chamber in order to modify the composition of the glass particles to be deposited on the heating portion of the glass rod in the chamber.

Abstract: A method of coating uses an anti-seizure agent for hot steel working that exhibits excellent wettability and surface film-adherability. The agent comprises: an inorganic component (first component); sodium hydroxide (second component); water-soluble resins and/or water-soluble surfactants (third component); and water. With the sum of the first component, the second component, and the third component as 100 mass %, the anti-seizure agent contains: 96.5 mass % or more and 99.98 mass % or less of the first component; 0.01 mass % or more and 2.0 mass % or less of the second component; and 0.01 mass % or more and 1.5 mass % or less of the third component, and the inorganic component is one or more selected from a group consisting of Al2O3, SiO2, CaO, B2O3, K2O, and Na2O. A coating layer formed solidly adheres to the steel and does not come off in both cold and hot working.

Abstract: A method for accurately measuring the cutoff wavelength of a high order mode of an optical fiber includes a first step of measuring power spectrum P1(?) of light output from a light source; a second step of measuring power spectrum P2(?) of light emitted from one end of a test fiber when light output from the light source is made incident on the other end of the test fiber placed in a form (preferably spiral) allowing the curvature to vary in the longitudinal direction thereof; a third step of obtaining difference spectrum P(?) representing the difference between the power spectrum P2(?) and the power spectrum P1(?); and a fourth step of obtaining the cutoff wavelength of a high order mode of the test fiber on the basis of the difference spectrum P(?).

Abstract: An optical fiber that has a small bending loss can be securely prevented from being fractured due to accidental bending during installation or other operations. The optical fiber includes a core, a first cladding, a second cladding, and a third cladding. The relative refractive index difference ?1 of the core is in the range of 0.3% to 0.38%, the relative refractive index difference ?2 of the first cladding is equal to or smaller than 0%, and the relative refractive index difference ?3 of the second cladding is in the range of ?1.8% to ?0.5%. The inner radius r2 and the outer radius r3 of the second cladding satisfy the expression “0.4r2+10.5<r3<0.2r2+16”, and the inner radius r2 of the second cladding is equal to or greater than 8 ?m.

Abstract: An optical fiber that has a small bending loss can be securely prevented from being fractured due to accidental bending during installation or other operations. The optical fiber includes a core, a first cladding, a second cladding, and a third cladding. The relative refractive index difference ?1 of the core is in the range of 0.3% to 0.38%, the relative refractive index difference ?2 of the first cladding is equal to or smaller than 0%, and the relative refractive index difference ?3 of the second cladding is in the range of ?1.8% to ?0.5%. The inner radius r2 and the outer radius r3 of the second cladding satisfy the expression “0.4r2+10.5<r3<0.2r2+16”, and the inner radius r2 of the second cladding is equal to or greater than 8 ?m.