Abstract: A method for manufacturing a preform having a core and a multilayer clad, includes covering a circumference of a rod including at least the core and an inner clad layer with a first tube including at least a high viscosity clad layer, and unifying the rod and the first tube by heating and contracting the first tube.

Abstract: Provided is an apparatus and method for manufacturing an optical fiber preform by supplying a high-frequency induction thermal plasma torch with at least glass raw material, dopant raw material, and oxygen, and depositing the glass particles synthesized in the plasma flame onto a surface of a glass rod that moves backward and forward relative to the plasma torch while rotating, wherein deposition of the glass particles is performed while cooling the glass rod. As a result, the concentration of fluorine doped in the cladding increase, thereby improving the relative refractive index of the preform.

Abstract: Provided is an optical fiber preform manufacturing method comprising supplying a high-frequency induction thermal plasma torch with at least glass raw material, dopant raw material, and oxygen, and depositing the glass particles synthesized in the plasma flame onto a surface of a glass rod that moves backward and forward relative to the plasma torch while rotating, wherein the plasma flame is narrowed such that at least a portion of the glass particles continuously formed by the plasma flame are not deposited on the glass rod. As a result, the fluorine concentration in the cladding is increased to improve the relative refractive index difference of the preform.

Abstract: A method for measuring non-circularity of a core part of an optical fiber base material having the core part and a clad part includes immersing the optical fiber base material in liquid having a refractive index substantially equal to that of the clad part of the optical fiber base material; irradiating parallel light from a side face of the optical fiber base material to measure intensity distribution of transmitted light; measuring a width of a dark space caused by light passing the core part on intensity distribution to obtain a relative value for a core diameter; rotating the optical fiber base material to further obtain the relative value for the core diameter at plural points for a circumferential direction; and obtaining non-circularity of the core part based on the obtained plurality of relative values for the core diameter.

Abstract: A method for measuring non-circularity of a core portion of an optical fiber base material includes a distribution measuring step of (i) moving the optical fiber base material in a direction parallel to a central axis of the core portion while light is irradiated, in a direction perpendicular to the central axis, to the optical fiber base material which is immersed in the matching oil, and (ii) recording a variation in a width of a portion of the irradiated light which transmits through the core portion in association with a moved distance of the optical fiber base material, thereby measuring a distribution of relative values of an outer diameter of the core portion in terms of a longitudinal direction of the optical fiber base material, a distribution storing step of performing the distribution measuring step each time the optical fiber base material is rotated about the central axis by a predetermined angle, thereby recording a plurality of distributions of the relative values of the outer diameter of the c

Abstract: In an apparatus for fabricating an optical fiber, the apparatus includes a drawing furnace provided with an insertion opening for receiving an optical fiber perform, a feed mechanism configured to support one end of the optical fiber preform so as to feed into the drawing furnace, a first sealing unit configured to seal a clearance gap between the optical fiber preform and the insertion opening, and a second sealing unit configured to seal a gap between the optical fiber preform and the first sealing unit when a tapered portion formed at the one end side of the optical fiber preform passes through the insertion opening. As a result, the available entirety of the optical fiber preform can be changed to an optical fiber, so that the cost for fabricating the optical fiber can be significantly reduced.

Abstract: In a furnace for heating an optical fiber preform to be inserted from an insertion opening, the furnace includes an annular sealing body for sealing a clearance gap between the optical fiber preform and the insertion opening. The annular sealing body is formed from stacked annular disks respectively having an insertion hole in its center area. The annular disk has slits formed from a inner edge of the annular disk toward its periphery side and flexible portions that are defined by the slits and bend by an interference with the optical fiber preform to be inserted into the insertion hole. When the optical fiber preform is inserted into the insertion hole of the annular sealing body, the flexible portions bend.

Abstract: When manufacturing an optical fiber preform by feeding at least glass raw material, dopant material and oxygen gas to a high frequency induction thermal plasma torch to synthesize glass particles in plasma therein, a glass rod is rotated and reciprocated relative to the plasma torch to deposit the synthesized glass particles onto the glass rod. The fluctuation of the relative refractive-index difference in the longitudinal direction of the optical fiber preform is suppressed and the average value of the relative refractive-index difference in the longitudinal direction is enhanced. The glass raw material is fed to the plasma torch in a forward direction of the reciprocating motion of the glass rod, and a feeding amount of the glass raw material in the backward direction of the reciprocating motion is reduced relative to the feeding amount in the forward direction.

Abstract: There is provided a measurement method of non-circularity of a core part of an optical fiber base material and an apparatus therefor, which can accurately and easily measure non-circularity of the core part, regardless of a refractive index difference between a core and a clad and an interval between a light projector and a photoreceiver.

Abstract: A method for measuring non-circularity of a core portion of an optical fiber base material includes a distribution measuring step of (i) moving the optical fiber base material in a direction parallel to a central axis of the core portion while light is irradiated, in a direction perpendicular to the central axis, to the optical fiber base material which is immersed in the matching oil, and (ii) recording a variation in a width of a portion of the irradiated light which transmits through the core portion in association with a moved distance of the optical fiber base material, thereby measuring a distribution of relative values of an outer diameter of the core portion in terms of a longitudinal direction of the optical fiber base material, a distribution storing step of performing the distribution measuring step each time the optical fiber base material is rotated about the central axis by a predetermined angle, thereby recording a plurality of distributions of the relative values of the outer diameter of the c

Abstract: There is provided a manufacturing apparatus of a porous glass base material which can prevent soot from being formed on an upper surface (ceiling) of the process chamber, and reduce the amount of soot that comes off the upper surface and falls. A manufacturing apparatus of a porous glass base material 4 deposits glass particles produced by subjecting a material gas to flame hydrolysis, onto a starting member 1 placed vertically. Here, a plurality of gas inlets 5 are provided in one or more lateral walls of a process chamber including a burner 2 for the deposition therein, in upper portions of the lateral walls and along a ceiling of the process chamber.

Abstract: In respect of a method for manufacturing a preform of an optical fiber, the method comprises the steps of forming a porous glass preform by accumulating glass particles, preparing a container made of a quartz glass, which is formed by heating the quartz glass with an electric furnace, providing a dehydration gas and an inert gas to the container, heating the container to which dehydration gas and inert gas is provided and dehydrating and sintering the porous glass preform by inserting the porous glass preform into the container, which is heated.

Abstract: There is provide an optical fiber processing apparatus and a process method capable of shortening time required for replacing an atmosphere in a treatment container with inert gas and filling with deuterium and of restraining an amount used of expensive deuterium. An optical fiber processing apparatus includes a plurality of containers 1 for processing optical fiber that are spatially coupled by piping, each treatment container 1 including a treatment chamber that can be sealed and accommodate one or more bobbins 4 on which fiber to be processed is wound, in which the treatment chamber is supplied with treatment gas, and the optical fiber is processed by the gas. The treatment gas is deuterium or gas including the deuterium.

Abstract: An apparatus for fabricating a soot preform for an optical fiber. The soot preform is fabricated by depositing glass particles on a starting rod capable of being rotated and pulled up. The apparatus comprises elements as follows. A reaction chamber is used for depositing the glass particles on the starting rod. An upper room is located above the reaction chamber for receiving the soot preform formed in the upper portion of the reaction chamber. At least one core burner is installed in the reaction chamber. A gas-supplying inlet is located in the top part of the sidewall of the reaction chamber closest to burner(s), and a gas-exhausting outlet is located in the top part of another sidewall opposite to the gas-supplying inlet. In addition, at least one cladding burner is installed in the reaction chamber.

Abstract: Even if an optical fiber obtained by drawing a preform is exposed to hydrogen atmosphere, an OH peak in the optical fiber at wavelength of about 1385 nm hardly rises regardless of the condition of drawing.

Abstract: An apparatus for fabricating a soot preform for an optical fiber. The soot preform is fabricated by depositing glass particles on a starting rod capable of being rotated and pulled up. The apparatus comprises elements as follows. A reaction chamber is used for depositing the glass particles on the starting rod. An upper room is located above the reaction chamber for receiving the soot preform formed in the upper portion of the reaction chamber. At least one core burner is installed in the reaction chamber. A gas-supplying inlet is located in the top part of the sidewall of the reaction chamber closest to burner(s), and a gas-exhausting outlet is located in the top part of another sidewall opposite to the gas-supplying inlet. In addition, at least one cladding burner is installed in the reaction chamber.

Abstract: A method for manufacturing a base material for an optical fiber, includes steps of: holding a bar material by a support member; and adjusting to reduce a difference between an axis of the bar material and a rotational axis of the support member. Furthermore, an optical fiber base material grasping apparatus for holding a bar material having an axis, includes: a support member having a center axis, the support member being rotatable around the center axis; and an adjusting mechanism for reducing a difference between the axis of the bar material and the central axis of the support member.

Abstract: A method for manufacturing a glass base material for an optical fiber by forming a core rod having a core section and a portion of a clad, forming an additional clad by depositing glass particles on circumference of the core rod, and performing a sintering and vitrifying process on an obtained porous base material, includes the step of forming the core rod in order that the relation 3.75≦a/m≦6 is satisfied, where ‘a’ denotes an outer diameter of a section corresponding to the core rod, and ‘m’ denotes a mode field diameter at 1385 nm in wavelength with regard to the optical fiber obtained by drawing the glass base material.

Abstract: Even if an optical fiber obtained by drawing a preform is exposed to hydrogen atmosphere, an OH peak in the optical fiber at wavelength of about 1385 nm hardly rises regardless of the condition of drawing.

Abstract: In respect of a method for manufacturing a preform of an optical fiber, the method comprises the steps of forming a porous glass preform by accumulating glass particles, preparing a container made of a quartz glass, which is formed by heating the quartz glass with an electric furnace, providing a dehydration gas and an inert gas to the container, heating the container to which dehydration gas and inert gas is provided and dehydrating and sintering the porous glass preform by inserting the porous glass preform into the container, which is heated.