Abstract: A process of manufacturing a silica glass article comprising the steps of: (1) irradiating a silica glass article with electromagnetic waves to generate defects therein; and (2) immersing the thus irradiated silica glass article in an atmosphere comprising a hydrogen gas, thereby providing the resulting silica glass article with a characteristic that is effective for preventing it substantially from increasing its absorption within an ultraviolet region due to ultraviolet ray irradiation. Also disclosed are a silica glass article or a glass fiber produced according to the manufacturing process.

Abstract: In an optical fiber of this invention, the MFD is increased to effectively suppress the influence of nonlinear optical effects. A method of manufacturing the optical fiber effectively prevents bubble occurrence in a transparent preform, deformation of the preform, and flaws on the preform surface during the manufacture. The optical fiber has, from its center to the peripheral portion, a first core having a first refractive index n1, a second core having a second refractive index n2 (<n1), a first cladding having a third refractive index n3 (<n2), and a second cladding having a fourth refractive index n4 (>n3, <n2). The outer diameter of the second core is set to be 25 to 40 &mgr;m. Specifically, the refractive indices of the first and second claddings of the optical fiber preferably increase in the radial direction from the inner side thereof to the peripheral side thereof.

Abstract: A process of manufacturing a silica glass article comprising the steps of: (1) irradiating a silica glass article with electromagnetic waves to generate defects therein; and (2) immersing the thus irradiated silica glass article in an atmosphere comprising a hydrogen gas, thereby providing the resulting silica glass article with a characteristic that is effective for preventing it substantially from increasing its absorption within an ultraviolet region due to ultraviolet ray irradiation. Also disclosed are a silica glass article or a glass fiber produced according to the manufacturing process.

Abstract: The present invention relates to a method of making a preform which can restrain each member from deforming at the time of making, and a method of making an optical fiber with a smaller polarization mode dispersion by utilizing this preform. In the method of making a preform, the collapsing step carried out when making the preform is divided into at least two stages composed of a first step of forming a first collapsed body by collapsing a core rod member and a first cladding tube member, and a second step of forming a new collapsed body by collapsing the first collapsed body and a second cladding tube member. Also, in at least the first step, the collapsed body obtained is elongated, whereas such a plurality of stages of collapsing step and elongation of the resulting collapsed body reduce the outer diameter ratio of the outer member to the inner member to be collapsed, whereby the deformation resulting from the heating at the time of a single collapsing operation and the like is hard to occur.

Abstract: A process of manufacturing a silica glass article comprising the steps of: (1) irradiating a silica glass article with electromagnetic waves to generate defects therein; and (2) immersing the thus irradiated silica glass article in an atmosphere comprising a hydrogen gas, thereby providing the resulting silica glass article with a characteristic that is effective for preventing it substantially from increasing its absorption within an ultraviolet region due to ultraviolet ray irradiation. Also disclosed are a silica glass article or a glass fiber produced according to the manufacturing process.

Abstract: In a process for producing an optical fiber preform, a starting member and a glass synthesizing burner are reciprocated relative to each other so that fine glass particles synthesized with the burner are deposited layer by layer on the starting member, and a heating power of the glass synthesizing burner in a nonsteady outside diameter portion at either end of the soot preform is adjusted to control the temperature of the nonsteady outside diameter portion at either end against local elevation. The starting member is formed of a transparent glass rod that is held within a vessel and rotatable about its own axis, the burner is fitted on a lateral side of the vessel at right angles to the rotating axis of the starting member and is movable towards or away from the starting member.

Abstract: In an optical fiber of this invention, the MFD is increased to effectively suppress the influence of nonlinear optical effects. A method of manufacturing the optical fiber effectively prevents bubble occurrence in a transparent preform, deformation of the preform, and flaws on the preform surface during the manufacture. The optical fiber has, from its center to the peripheral portion, a first core having a first refractive index n1, a second core having a second refractive index n2 (<n1), a first cladding having a third refractive index n3 (<n2), and a second cladding having a fourth refractive index n4 (>n3, <n2). The outer diameter of the second cladding is set to be 25 to 40 &mgr;m. Specifically, the refractive indices of the first and second claddings of the optical fiber preferably increase in the radial direction from the inner side thereof to the peripheral side thereof.

Abstract: A process of manufacturing a silica glass article comprising the steps of: (1) irradiating a silica glass article with electromagnetic waves to generate defects therein; and (2) immersing the thus irradiated silica glass article in an atmosphere comprising a hydrogen gas, thereby providing the resulting silica glass article with a characteristic that is effective for preventing it substantially from increasing its absorption within an ultraviolet region due to ultraviolet ray irradiation. Also disclosed are a silica glass article or a glass fiber produced according to the manufacturing process.

Abstract: A glass preform for an optical fiber is effectively drawn by connecting dummy rods to both ends of the glass preform and connecting the dummy rods to fitting members.

Abstract: The present invention relates to a method for precisely elongating a glass preform of an optical fiber body having a desired outer diameter. In this method, a predetermined part of the glass preform is elongated as tensile stress is applied to one end of the glass preform while a predetermined part of the glass preform is heated and softened successively from one end toward the other end of the glass preform. In this elongating operation, while the outer diameter of the softening portion of the glass preform is measured, the tensile stress is adjusted such that the outer diameter of the softening portion coincides with a preset value of the control outer diameter. In particular, this method is characterized in that the preset value of the control outer diameter is changed at least during a predetermined period until termination of elongation or during a predetermined period from the start of elongation.

Abstract: In order to provide an improved process for the production of a glass preform for an optical fiber which includes substantially no bubble formation therein and also has a substantially uniform shape, the present invention provides a process for the production of a glass preform which is at least partially formed from silica. In particular, a body is formed on a rod by depositing fine glass particles thereon, preferably by the vapor phase reactions, and heating the body to vitrify under a reduced atmosphere or a vacuumed atmosphere so that the glass preform is produced.

Abstract: An optical fiber glass preform is preheated so that it is uniformly preheated therethrough, then a surface of the preform is abraded by an oxyhydrogen flame to obtain a smooth optical fiber glass preform. This method is advantageous when relatively larger diameter preforms are treated in this manner because the step of uniformly preheating the preform reduces or eliminates a temperature differential therein. The temperature differential could otherwise cause the preform to crack during cooling.

Abstract: A method of manufacturing an optical fiber in which the deviation of a cutoff wavelength from a design value can be minimized. It is found that, upon diameter reduction of a porous core glass body by heat treatment, when the diameter reduction ratio is set to a value larger than 0.90, a "spike" in the refractive index distribution curve of a core can be prevented, and the deviation of the cutoff wavelength from the design value can be minimized. Therefore, there is provided a method comprising the first step of depositing fine SiO.sub.2 particles and fine GeO.sub.2 particles, which are produced by a core formation burner, to grow a porous core glass body from a distal end of a rotating starting rod in an axial direction, the second step of performing diameter reduction by heating the grown porous core glass body by heating means while growing the porous core glass body, and the third step of depositing fine SiO.sub.

Abstract: A glass preform for an optical fiber is effectively drawn by connecting dummy rods to both ends of the glass preform and connecting the dummy rods to fitting members.

Abstract: An optical fiber preform manufacturing apparatus which continuously monitors the weight of a preform during manufacturing by a load cell without increasing the offset amount of the preform. The preform manufacturing apparatus includes a rotary chuck unit vertically moved by an elevating unit and a rod gripped by the rotary chuck unit and vertically extending downward. At the time of manufacturing a preform, the elevating unit and the rotary chuck unit are driven to rotate and move a starting rod suspended from the lower end of the rod upward. A support plate is fixed to the rotary chuck unit. Three or more load cells are arranged between the support plate and an elevating plate of the elevating unit. The rotary chuck unit is firmly supported by these load cells, so that the rotating shaft is not inclined. A hole is formed in the elevating plate, and the rotary chuck unit extends through the hole with a gap therebetween.

Abstract: An apparatus includes a first waveguide having a first surface having a first hole through which a fiber passes, and a second surface having a second hole through which an object passes and opposing the first surface, a magic tee connected to the first waveguide, and an adjustable short plunger connected to the magic tee.

Abstract: An apparatus for vitrifying a soot preform from which an optical fiber is produced by drawing, is composed of a main vacuum chamber 20 in which a muffle tube 70 for vitrifying the soot preform PF is located, and an auxiliary vacuum chamber 30 mounted on the main vacuum chamber 20 and communicated therewith through a passage, and a gate valve 60 for opening and closing the passage. The muffle tube 70 has a inner surface covered with silicon carbide layer 70a.

Abstract: There is provided a process for the consolidation of a porous glass preform for an optical fiber by heating the preform under an increasing pattern of a heating temperature in a vacuum furnace comprising a muffle tube therein characterized in that the increasing pattern is divided into two steps consisting of a first step and a second step with regard to time, and the first step has a pattern in which the heating temperature is increased under a reduced pressure atmosphere and a gas comprising at least an inert gas is supplied to the vacuum furnace under the reduced pressure atmosphere and the second step has a pattern in which the heating temperature is increased under a reduced pressure atmosphere in which a gas comprising a smaller amount of an inert gas than that of the first step is supplied to the vacuum furnace or under a vacuum pressure atmosphere in which no gas is supplied to the vacuum furnace.

Abstract: There is provided an apparatus for the production of a hermetically coated optical fiber in which a glass preform for an optical fiber is melt drawn in a melt drawing furnace to produce a bare optical fiber which is passed to a reactor where a feed gas is supplied and the bare optical fiber is coated with a thin carbon coating made from the feed gas by the Chemical Vapor Deposition method characterized in that the reactor comprises an upper portion to which the feed gas is supplied, a middle portion in which the CVD method is substantially carried out and a lower portion from which an exhausted gas is withdrawn, and a cross sectional area of the middle portion perpendicular to a longitudinal direction of the optical fiber is larger than that of the upper portion.

Abstract: A glass preform for an optical fiber is flame abrased with an oxyhydrogen flame while vertically suspending and rotating the glass preform and relatively moving one or both of the glass preform and the oxyhydrogen flame, whereby a surface of the glass preform is smoothened.