Abstract: An optical fiber screening test method in which while continuously travelling, an optical fiber passes a tension applying section which applies tension and the optical fiber which has passed the tension applying section is continuously wound by a winding bobbin is provided. The method includes running the optical fiber to which the tension has been applied along a first pulley and a second pulley sequentially, winding the optical fiber by the winding bobbin, and stopping rotation of the winding bobbin when the optical fiber is broken by applying the tension, and performing an adjustment so that an already-wound outer circumferential surface of the winding bobbin on which the optical fiber is already wound is not positioned on an extension line of a linear optical fiber travelling path from the first pulley to the second pulley at a time when the rotation of the winding bobbin is stopped.

Abstract: Provided is a method for manufacturing an optical fiber preform using a combustion burner. The method includes at least one of: a step ? of, when a mode is changed from a deposition mode to a non-deposition mode, changing a gas discharged from a combustion gas port of the burner from a combustion gas to a purge gas, while maintaining a pilot light and a flow rate of a supporting gas from supporting gas discharge nozzles of the burner so that the nozzle tip does not glow; and a step ? of, when the mode is changed from the non-deposition mode to the deposition mode, changing a gas discharged from the combustion gas port from a purge gas to a combustion gas, while maintaining a pilot light and the flow rate of the supporting gas so that the nozzle tip does not glow.

Abstract: An optical fiber preform manufacturing apparatus includes a booth, a reaction chamber disposed inside the booth, a target member disposed within the reaction chamber, a burner that deposits glass particles on the target member, a partition plate that partitions the internal space of the booth into a first space where the reaction chamber and the burner are disposed and a second space, and that has a plurality of through holes that allows the first space and the second space to communicate with each other, an air supply unit that supplies clean air into the first space; and an exhaust unit that discharges air within the second space.

Abstract: A method of producing optical fiber preform includes: forming a deposited layer by depositing glass particles on a periphery of a target element in a deposition mode while burning a mixed gas containing a glass source material gas, a flaming gas, and a supporting gas by use of a flaming burner; maintaining a state where the supporting gas flows at a flow velocity greater than or equal to a flow velocity at which a nozzle end of the supporting gas discharge nozzles does not glow while maintaining a pilot burner by allowing the flaming gas to flow to the seal gas discharge nozzle after a seal gas is replaced with the flaming gas in a case where a mode is changed from the deposition mode to a non-deposition mode; and replacing the flaming gas flowing to the flaming gas port with a purge gas.

Abstract: An optical fiber screening test method in which while continuously travelling, an optical fiber passes a tension applying section which applies tension and the optical fiber which has passed the tension applying section is continuously wound by a winding bobbin is provided. The method includes running the optical fiber to which the tension has been applied along a first pulley and a second pulley sequentially, winding the optical fiber by the winding bobbin, and stopping rotation of the winding bobbin when the optical fiber is broken by applying the tension, and performing an adjustment so that an already-wound outer circumferential surface of the winding bobbin on which the optical fiber is already wound is not positioned on an extension line of a linear optical fiber travelling path from the first pulley to the second pulley at a time when the rotation of the winding bobbin is stopped.

Abstract: A method for manufacturing an optical fiber preform includes a process A of applying flame polishing to a center glass rod, a process B of determining a ratio ra/rb, which is a ratio of a radius ra of the center glass rod expressed in millimeters with respect to a radius rb of a target optical fiber preform expressed in millimeters, based on a refractive index profile of a target optical fiber preform, and a process C of determining an amount of fine glass particles to be deposited on the center glass rod so that a ratio ra/rb/c falls within a range from 0.002 to 0.01, where “c” is a maximum value of hydroxyl group concentration expressed in ppm in the vicinity of a boundary between the center glass rod and an outer layer, which is formed by depositing fine glass particles on the center rod and by being vitrified.

Abstract: A method for fabricating a porous silica preform includes the steps of supplying fuel gas for generating an oxyhydrogen flame to a glass synthesizing burner; supplying Gas A containing silicon and Gas B containing fluorine to the burner; synthesizing glass particles; and depositing the glass particles around a starting rod, in which when glass particles are deposited directly on the starting rod, a supply of Gas A and a supply of Gas B supplied to the burner are adjusted so that a ratio of the number of fluorine atoms to the number of silicon atoms in the gas supplied to the burner satisfies the following Formula (1): {(number of F atoms)/(number of Si atoms)}?0.1??(1).

Abstract: A rare earth-doped core optical fiber of the present invention includes a core comprising a silica glass containing at least aluminum and ytterbium, and a clad provided around the core and comprising a silica glass having a lower refraction index than that of the core, wherein the core has an aluminum concentration of 2% by mass or more, and ytterbium is doped into the core at such a concentration that the absorption band which appears around a wavelength of 976 nm in the absorption band by ytterbium contained in the core shows a peak absorption coefficient of 800 dB/m or less.

Abstract: A method of producing optical fiber preform includes: forming a deposited layer by depositing glass particles on a periphery of a target element in a deposition mode while burning a mixed gas containing a glass source material gas, a flaming gas, and a supporting gas by use of a flaming burner; maintaining a state where the supporting gas flows at a flow velocity greater than or equal to a flow velocity at which a nozzle end of the supporting gas discharge nozzles does not glow while maintaining a pilot burner by allowing the flaming gas to flow to the seal gas discharge nozzle after a seal gas is replaced with the flaming gas in a case where a mode is changed from the deposition mode to a non-deposition mode; and replacing the flaming gas flowing to the flaming gas port with a purge gas.

Abstract: A plastic glass optical fiber includes a glass core (diameter a1, relative refractive index difference ?1, and refractive index n1), a polymer core (diameter a2, relative refractive index difference ?2, and refractive index n2), and a polymer cladding (refractive index n3), in which the diameter a1 of the glass core is within a range of 110 ?m to 200 ?m, a parameter X (X is a22/a12) is within a range of 1.15?X?2.9, a parameter Y (Y is ?2/?1) is within a range of 0.25?Y?0.84X?0.68 (when 1.15?X?2) or 0.48X?0.71?Y??(2/9)X+13/9 (when 2?X?2.9), a parameter ZR (ZR is Z2core/Z1core; Z2core=a22?/4×?(n12?n32) and Z1core=a12?/4×?(n12?n22)) is within a range of 1.25?ZR?4.

Abstract: An optical fiber preform manufacturing apparatus includes a booth, a reaction chamber disposed inside the booth, a target member disposed within the reaction chamber, a burner that deposits glass particles on the target member, a partition plate that partitions the internal space of the booth into a first space where the reaction chamber and the burner are disposed and a second space, and that has a plurality of through holes that allows the first space and the second space to communicate with each other, an air supply unit that supplies clean air into the first space; and an exhaust unit that discharges air within the second space.

Abstract: Method for manufacturing an optical fiber perform, which forms a glass fine particle deposition portion composed of glass fine particles on a glass rod, and suspends the glass fine particle deposition vertically into a heating furnace to heat, and transparentize, the glass fine particle deposition. The method comprises the following steps: forming a hazy portion before heating, by causing a surface portion of the glass rod to sublime and adhere to at least a portion of a region closer to one end of the glass rod than a region of the glass rod where the deposition portion is formed; forming the deposition portion by depositing the glass fine particles on the glass rod; and transparentizing the deposition portion by heating the glass fine particle deposition in a state where the proximal end of the glass rod where the hazy portion is formed is suspended vertically into the heating furnace.

Abstract: A dehydration-sintering furnace for dehydrating and/or sintering an optical fiber preform for use in production of an optical fiber includes a muffle for accommodating the optical fiber preform, a heater for heating the muffle, and a pressure fluctuation absorbing apparatus connected to the muffle. Since the pressure fluctuation absorbing apparatus is thermally insulated from a room temperature atmosphere or heated, vapor produced in a dehydration-sintering process is prevented from condensing (liquefying) in a pressure fluctuation absorbing apparatus, thereby preventing reduced dehydration effectiveness in the muffle and reduced quality of the optical fiber preform.

Abstract: A dehydration-sintering furnace includes a core tube configured to dehydrate and sinter a porous base material in fabrication of an optical fiber and having an outlet configured to discharge a vapor. The furnace includes a pressure-variation damper connected to the outlet of the core tube. The furnace includes a trap between the core tube and the pressure-variation damper for collecting the vapor.

Abstract: A dehydration-sintering furnace includes a core tube configured to dehydrate and sinter a porous base material in fabrication of an optical fiber and having an outlet configured to discharge a vapor. The furnace includes a pressure-variation damper connected to the outlet of the core tube. The furnace includes a trap between the core tube and the pressure-variation damper for collecting the vapor.

Abstract: A rare earth-doped core optical fiber of the present invention includes a core comprising a silica glass containing at least aluminum and ytterbium, and a clad provided around the core and comprising a silica glass having a lower refraction index than that of the core, wherein the core has an aluminum concentration of 2% by mass or more, and ytterbium is doped into the core at such a concentration that the absorption band which appears around a wavelength of 976 nm in the absorption band by ytterbium contained in the core shows a peak absorption coefficient of 800 dB/m or less.

Abstract: A plastic glass optical fiber includes a glass core (diameter a1, relative refractive index difference ?1, and refractive index n1), a polymer core (diameter a2, relative refractive index difference ?2, and refractive index n2), and a polymer cladding (refractive index n3), in which the diameter a1 of the glass core is within a range of 110 ?m to 200 ?m, a parameter X (X is a22/a12) is within a range of 1.15?X?2.9, a parameter Y (Y is ?2/?1) is within a range of 0.25?Y?0.84X?0.68 (when 1.15?X?2) or 0.48X?0.71?Y??(2/9)X+13/9 (when 2?X?2.9), a parameter ZR (ZR is Z2core/Z1core; Z2core=a22?/4×?(n12?n32) and Z1core=a12?/4×?(n12n?n22)) is within a range of 1.25?ZR?4.

Abstract: A method for fabricating a porous silica preform includes the steps of supplying fuel gas for generating an oxyhydrogen flame to a glass synthesizing burner; supplying Gas A containing silicon and Gas B containing fluorine to the burner; synthesizing glass particles; and depositing the glass particles around a starting rod, in which when glass particles are deposited directly on the starting rod, a supply of Gas A and a supply of Gas B supplied to the burner are adjusted so that a ratio of the number of fluorine atoms to the number of silicon atoms in the gas supplied to the burner satisfies the following Formula (1): {(number of F atoms)/(number of Si atoms)}?0.

Abstract: A rare earth-doped core optical fiber includes a core comprising a silica glass containing at least aluminum and ytterbium, a clad provided around the core and comprising a silica glass having a lower refraction index than that of the core, and a polymer layer provided on the outer circumference of the clad and having a lower refractive index than that of the clad, wherein aluminum and ytterbium are doped into the core such that a loss increase by photodarkening, TPD, satisfies the following inequality (A). By this rare earth-doped core optical fiber, it is possible to manufacture an optical fiber laser capable of maintaining a sufficient laser oscillation output even when used for a long period of time. TPD?10{?0.655*(DAl)?4.304*exp{?0.00343*(AYb)}+1.

Abstract: A method for manufacturing an optical fiber preform of the invention is a method for manufacturing an optical fiber preform, which forms a deposition portion composed of glass fine particles on a glass rod so as to form a glass fine particle deposition, and suspends the glass fine particle deposition vertically into a heating furnace to heat the glass fine particle deposition to transparentize the deposition portion, the method comprising: a step of forming a hazy portion, by causing a surface portion of the glass rod to sublime and adhere to at least a portion of a region closer to one end of the glass rod than a region of the glass rod where the deposition portion is formed, before said heating; a step of forming the deposition portion by depositing the glass fine particles on the glass rod; and a step of transparentizing the deposition portion by heating the glass fine particle deposition in a state where the proximal end of the glass rod where the hazy portion is formed is held and the glass fine particle