Abstract: A wire-drawing optical fiber base material manufacturing method of heating an optical fiber base material by a heater and forming a drawing shape portion at an end portion. The manufacturing method includes: forming, by a flow-regulating member disposed adjacent to the heater, a gas flow such that formation, along a surface of the optical fiber base material, of a flow of a gas containing a Si compound generated from the optical fiber base material heated by the heater is inhibited; and forming, while maintaining the gas flow, the drawing shape portion by pulling part of the optical fiber base material softened by being heated by the heater.

Abstract: A wire-drawing optical fiber base material manufacturing method of heating an optical fiber base material by a heater and forming a drawing shape portion at an end portion. The manufacturing method includes: forming, by a flow-regulating member disposed adjacent to the heater, a gas flow such that formation, along a surface of the optical fiber base material, of a flow of a gas containing a Si compound generated from the optical fiber base material heated by the heater is inhibited; and forming, while maintaining the gas flow, the drawing shape portion by pulling part of the optical fiber base material softened by being heated by the heater.

Abstract: According to a fabrication method for fabricating a porous glass base material for optical fiber, the orientation of a clad forming burner used to form the outermost layer of a clad-corresponding portion is changed further upward while glass fine particles are deposited during the period between a first timing and a second timing. At the first timing, the outer diameter of the porous glass base material for optical fiber has not reached a target outer diameter. The second timing is later than the first timing, and either a timing at which the outer diameter of the porous glass base material for optical fiber reaches the target outer diameter for the first time, or a timing prior to this timing.

Abstract: To provide a method of sintering an optical fiber porous glass base material, capable of sufficient dehydration and reducing a transmission loss caused by residual moisture by efficiently transferring heat from the heater to the base material during a process in dehydration/sintering for an optical fiber porous glass base material, a porous glass base material having a heat shield plate installed in a vicinity of a lower end is vertically inserted into a furnace core tube provided with a heater along an outer circumference, and heating using the heater is performed. The heat shield plate has an outer diameter which is 70% or larger than a diameter of the porous glass base material and smaller than an inner diameter of the furnace core tube.

Abstract: 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.

Abstract: A heating furnace includes a bolt inserted through an insertion hole in a part of a heater and further inserted into a hole on a tip surface of an electrode rod. A first washer is between a bearing surface of the bolt and one face of the heater. A second washer is between another face of the heater and the tip surface. The relation of: |L0·?0?(TH·?H+TB·?B+TE·?E)|·?T?0.15(TB+TE) is satisfied, where L0 is an interval between the bearing surface and the tip surface, ?0 is a linear expansion coefficient (LEC) of the bolt, TH, TB and TE are thicknesses of the part, first and second washers and ?H, ?B and ?E are their LECs, respectively, and ?T is a temperature increment quantity of a part where the heater and the electrode rod are fastened by the bolt.

Abstract: According to a fabrication method for fabricating a porous glass base material for optical fiber, the orientation of a clad forming burner used to form the outermost layer of a clad-corresponding portion is changed further upward while glass fine particles are deposited during the period between a first timing and a second timing. At the first timing, the outer diameter of the porous glass base material for optical fiber has not reached a target outer diameter. The second timing is later than the first timing, and either a timing at which the outer diameter of the porous glass base material for optical fiber reaches the target outer diameter for the first time, or a timing prior to this timing.

Abstract: In order to improve the yield of an optical fiber base material, provided is a manufacturing apparatus for manufacturing an optical fiber base material by forming a soot deposition body on a surface of a target rod, including a main burner that generates glass microparticles to be deposited on the target rod while moving in a longitudinal direction of the target rod; a pair of side burners that are arranged outside a movement range of the main burner and heat both ends of the soot deposition body formed on the surface of the target rod; and a shielding member that prevents the glass microparticles generated by the main burner from being deposited on the target rod farther outward than a segment of the target rod sandwiched by the pair of side burners.

Abstract: A burner for synthesization to synthesize glass particles that form a porous glass base material is provided, the burner for synthesization including a raw material gas injection portion to inject raw material gas toward a target, a combustion assisting gas injection portion to inject combustion assisting gas in a direction in which the combustion assisting gas is merged with the raw material gas at a first merging point, and a combustible gas injection portion to inject combustible gas in a direction in which the combustible gas is merged with the combustion assisting gas at a second merging point that is positioned closer to the combustion assisting gas injection portion than the first merging point. In the above-described burner for synthesization, the combustion assisting gas injection portion may also include a plurality of injection ports arranged along one straight line.

Abstract: According to a fabrication method for fabricating a porous glass base material for optical fiber, the orientation of a clad forming burner used to form the outermost layer of a clad-corresponding portion is changed further upward while glass fine particles are deposited during the period between a first timing and a second timing. At the first timing, the outer diameter of the porous glass base material for optical fiber has not reached a target outer diameter. The second timing is later than the first timing, and either a timing at which the outer diameter of the porous glass base material for optical fiber reaches the target outer diameter for the first time, or a timing prior to this timing.

Abstract: A porous glass base material sintering method comprising measuring a feeding speed Vf of a porous glass base material and a movement speed Vw of a bottom end of the glass base material; performing a sintering treatment of the porous glass base material presetting, for each feeding distance L of the porous glass base material, a greater-than-1 target value ?S (L) of an elongation rate in a straight body portion of the porous glass base material calculated based on a ratio Vw/Vf, and controlling at least one of a temperature of the heating furnace and a feeding speed of the porous glass base material such that a measured value ? of the elongation rate of the porous glass base material matches with the target value ?S (L).

Abstract: To provide a method of sintering an optical fiber porous glass base material, capable of sufficient dehydration and reducing a transmission loss caused by residual moisture by efficiently transferring heat from the heater to the base material during a process in dehydration/sintering for an optical fiber porous glass base material, a porous glass base material having a heat shield plate installed in a vicinity of a lower end is vertically inserted into a furnace core tube provided with a heater along an outer circumference, and heating using the heater is performed. The heat shield plate has an outer diameter which is 70% or larger than a diameter of the porous glass base material and smaller than an inner diameter of the furnace core tube.

Abstract: A burner for synthesization to synthesize glass particles that form a porous glass base material is provided, the burner for synthesization including a raw material gas injection portion to inject raw material gas toward a target, a combustion assisting gas injection portion to inject combustion assisting gas in a direction in which the combustion assisting gas is merged with the raw material gas at a first merging point, and a combustible gas injection portion to inject combustible gas in a direction in which the combustible gas is merged with the combustion assisting gas at a second merging point that is positioned closer to the combustion assisting gas injection portion than the first merging point. In the above-described burner for synthesization, the combustion assisting gas injection portion may also include a plurality of injection ports arranged along one straight line.

Abstract: A fabrication apparatus for fabricating a porous glass base material for optical fiber includes a core forming burner configured to form a core-corresponding portion corresponding to a core of optical fiber by depositing glass fine particles onto a hanging seed rod, a first clad forming burner configured to form a portion of a clad-corresponding portion corresponding to a clad of the optical fiber by depositing glass fine particles onto the core-corresponding portion, and a second clad forming burner configured to form a different portion of the clad-corresponding portion by depositing glass fine particles to form an outermost surface of the clad-corresponding portion. Here, a central axis of a flame ejected from the second clad forming burner has such a gradient that the central axis of the flame ejected from the second clad forming burner faces upward relative to a horizontal plane.

Abstract: According to a fabrication method for fabricating a porous glass base material for optical fiber, the orientation of a clad forming burner used to form the outermost layer of a clad-corresponding portion is changed further upward while glass fine particles are deposited during the period between a first timing and a second timing. At the first timing, the outer diameter of the porous glass base material for optical fiber has not reached a target outer diameter. The second timing is later than the first timing, and either a timing at which the outer diameter of the porous glass base material for optical fiber reaches the target outer diameter for the first time, or a timing prior to this timing.

Abstract: To prevent constriction machining from reducing usage efficiency of a glass rod, provided is a glass rod machining method including softening of softening a portion of the glass rod by heating the portion of the glass rod, and constricting of forming a constricted shape in the glass rod by moving one end of the glass rod relative to the other end of the glass rod at a constriction speed satisfying a condition that a constriction load acting as a tensile force on the glass rod does not extend beyond a predetermined range. In this method, the constricting includes, when constriction speed increases, making an adjustment to decrease a heating temperature of the glass rod. This method may include determining of determining the heating temperature of the glass rod during the constricting by referencing a heating temperature table in which heating temperatures corresponding to the constriction speed are stored in advance.

Abstract: To prevent a lowering of gripping force due to temperature changes, provided is a gripping mechanism including a plurality of chuck claws that, when having come close to each other, generate a gripping force on a gripped body; a chuck body that holds the plurality of chuck claws on a common planar surface, and moves them on the planar surface; and a plurality of chuck plates that, when each of the plurality of chuck claws grips the gripped body, are interposed between each of the plurality of chuck claws and the gripped body. A thermal expansion coefficient ?1 of the plurality of chuck claws, a thermal expansion coefficient ?2 of the plurality of chuck plates and a thermal expansion coefficient ?W of the gripped body have a relationship indicated by ?W<?1<?2??(Equation 1).

Abstract: A wire-drawing optical fiber base material manufacturing method of heating an optical fiber base material by a heater and forming a drawing shape portion at an end portion. The manufacturing method includes: forming, by a flow-regulating member disposed adjacent to the heater, a gas flow such that formation, along a surface of the optical fiber base material, of a flow of a gas containing a Si compound generated from the optical fiber base material heated by the heater is inhibited; and forming, while maintaining the gas flow, the drawing shape portion by pulling part of the optical fiber base material softened by being heated by the heater.

Abstract: In order to improve the yield of an optical fiber base material, provided is a manufacturing apparatus for manufacturing an optical fiber base material by forming a soot deposition body on a surface of a target rod, including a main burner that generates glass microparticles to be deposited on the target rod while moving in a longitudinal direction of the target rod; a pair of side burners that are arranged outside a movement range of the main burner and heat both ends of the soot deposition body formed on the surface of the target rod; and a shielding member that prevents the glass microparticles generated by the main burner from being deposited on the target rod farther outward than a segment of the target rod sandwiched by the pair of side burners.

Abstract: A heating furnace includes a bolt inserted through an insertion hole in a part of a heater and further inserted into a hole on a tip surface of an electrode rod. A first washer is between a bearing surface of the bolt and one face of the heater. A second washer is between another face of the heater and the tip surface. The relation of: |L0·?0?(TH·?H+TB·?B+TE·?E)|·?T?0.15(TB+TE) is satisfied, where L0 is an interval between the bearing surface and the tip surface, ?0 is a linear expansion coefficient (LEC) of the bolt, TH, TB and TE are thicknesses of the part, first and second washers and ?H, ?B and ?E are their LECs, respectively, and ?T is a temperature increment quantity of a part where the heater and the electrode rod are fastened by the bolt.