Abstract: This invention provides a method for manufacturing an optical glass in order to prevent the deterioration of the burner used in the synthesis of glass particles that form the optical glass, and to obtain a stable quality optical glass. In this invention, the number of residual bubbles with a diameter of 0.3 mm and more is 0.005/cm3 or less per unit volume of the optical glass. Such optical glass is obtained by controlling the temperature of an end face of the burner for glass synthesis during the deposition of the glass particles by regulating the relationship of the flow velocity or the flow volume between an inflammable gas and a combustion-supporting gas.

Abstract: A multi-tube burner is provided which includes a cylindrical outermost nozzle and at least one cylindrical inner nozzle provided coaxially with the outermost nozzle to form annular jet openings for gases used to manufacture a glass preform. The angle between a center axis of an outer circumference of the outermost nozzle and a distal end portion of each of the inner nozzles is 90°± not more than 3°. Furthermore, the distance between the center axis of the outer circumference of the outermost nozzle and each of center axes of inner circumferences and outer circumferences of the inner nozzles is not more than 0.20 mm.

Abstract: The present invention provides an optical fiber preform manufacturing method and a burner apparatus employed for this method. In this manufacturing method, when glass particles are synthesized in an oxy-hydrogen flame emitted from a burner to form a porous optical fiber preform by depositing glass particles in the radial direction of a starting member, the relationship between the flow rate vm (m/sec) of a source material gas or a mixed gas of the source material gas and an additive gas discharged from the burner, and the flow rate vs (m/sec) of an inert gas is such that ?0.06 vm+1.4?vs??0.02 vm+1.8, and vs?0.40, while the relationship between the flow volume Vm (l/min) of the source material gas discharged from the burner and the flow volume Vs (l/min) of the inert gas is such that Vs/Vm?0.2.

Abstract: The present invention provides an optical fiber preform manufacturing method and a burner apparatus employed for this method. In this manufacturing method, when glass particles are synthesized in an oxy-hydrogen flame emitted from a burner to form a porous optical fiber preform by depositing glass particles in the radial direction of a starting member, the relationship between the flow rate vm (m/sec) of a source material gas or a mixed gas of the source material gas and an additive gas discharged from the burner, and the flow rate vs (m/sec) of an inert gas is such that ?0.06 vm+1.4?vs??0.02 vm+1.8, and vs?0.40, while the relationship between the flow volume Vm (1/min) of the source material gas discharged from the burner and the flow volume Vs (1/min) of the inert gas is such that Vs/Vm?0.2.

Abstract: An optical fiber and an optical fiber preform having optical characteristics, such as the wavelength dispersion, close to design values by controlling the amount of change in the refractive index in the core, thereby realizing high-quality and high-speed transmission, and manufacturing methods therefor. The optical fiber or the optical fiber preform is manufactured in a manner such that at each position in the area in which the relative refractive index of the core with respect to the cladding is 80% or higher of the maximum value of the relative refractive index, the absolute value of the rate of change of the relative refractive index with respect to the position along the diameter of the cladding is 0.5 or less, where the position along the diameter of the cladding is defined by percentage with respect to the diameter.

Abstract: The present invention provides an optical fiber preform manufacturing method and a burner apparatus employed for this method. In this manufacturing method, when glass particles are synthesized in an oxy-hydrogen flame emitted from a burner to form a porous optical fiber preform by depositing glass particles in the radial direction of a starting member, the relationship between the flow rate vm (m/sec) of a source material gas or a mixed gas of the source material gas and an additive gas discharged from the burner, and the flow rate vs (m/sec) of an inert gas is such that ?0.06 vm+1.4?vs??0.02 vm+1.8, and vs?0.40, while the relationship between the flow volume Vm (1/min) of the source material gas discharged from the burner and the flow volume Vs (1/min) of the inert gas is such that Vs/Vm?0.2.

Abstract: This invention provides a method for manufacturing an optical glass in order to prevent the deterioration of the burner used in the synthesis of glass particles that form the optical glass, and to obtain a stable quality optical glass. In this invention, the number of residual bubbles with a diameter of 0.3 mm and more is 0.005/cm3 or less per unit volume of the optical glass. Such optical glass is obtained by controlling the temperature of an end face of the burner for glass synthesis during the deposition of the glass particles by regulating the relationship of the flow velocity or the flow volume between an inflammable gas and a combustion-supporting gas.

Abstract: A multi-tube burner is provided which includes a cylindrical outermost nozzle and at least one cylindrical inner nozzle provided coaxially with the outermost nozzle to form annular jet openings for gases used to manufacture a glass preform. The angle between a center axis of an outer circumference of the outermost nozzle and a distal end portion of each of the inner nozzles is 90°± not more than 3°. Furthermore, the distance between the center axis of the outer circumference of the outermost nozzle and each of center axes of inner circumferences and outer circumferences of the inner nozzles is not more than 0.20 mm.

Abstract: A method for producing a porous preform comprising measuring the surface temperature distribution at the end of the core soot preform, and (1) maintaining the surface temperature Tc at the center point on the end of the core soot preform in the range of 500 to 1000° C., and preferably in the range of 600 to 950° C.; and maintaining the difference Tm−Tc between the maximum surface temperature Tm at the end of the core soot preform and the surface temperature Tc at the center point on the end of the core soot preform in the range of 5 to 45° C.; and/or (2) maintaining the ratio R of the area in which the surface temperature at the end of the core soot preform is higher than the surface temperature Tc at the center point on the end of the core soot preform in the range of 5 to 30%.

Abstract: An object of this manufacturing method for an optical fiber preform is to provide an optical fiber preform which has no defects such as shearing and stripping between the core and the cladding region. The above object can be achieved by providing the manufacturing method for optical fiber preform, involving depositing glass particles in the radial direction on an outer peripheral portion of a cylindrical starting material provided with glass material which forms a core, thereby forming a porous layer to form an optical fiber precursor porous material, and sintering the porous material to manufacture an optical fiber preform, wherein a heating step for heating the surface of the starting material is provided adjacently before a step for forming the porous layer.

Abstract: An optical fiber and an optical fiber preform having optical characteristics, such as the wavelength dispersion, close to design values by controlling the amount of change in the refractive index in the core, thereby realizing high-quality and high-speed transmission, and manufacturing methods therefor. The optical fiber or the optical fiber preform is manufactured in a manner such that at each position in the area in which the relative refractive index of the core with respect to the cladding is 80% or higher of the maximum value of the relative refractive index, the absolute value of the rate of change of the relative refractive index with respect to the position along the diameter of the cladding is 0.5 or less, where the position along the diameter of the cladding is defined by percentage with respect to the diameter.

Abstract: A dispersion-shifted optical fiber (DS-fiber) is structured so that it has nearly zero chromatic dispersion in the 1.55 .mu.m wavelength band and, at the same time, achieves both reduced non linear effects and low dispersion slope. In particular, dispersion slope is reduced to a level sufficient for the fiber to be used for wavelength division multiplexing (WDM) applications. The properties of the fiber are developed such that chromatic dispersion in the 1.55 .mu.m band is nearly zero but not zero, effective cross section area is 45.about.70 .mu.m.sup.2, bending loss is 0.1.about.100 dB/m, dispersion slope is 0.05.about.0.08 ps/km/nm.sup.2, and the cutoff wavelength is such that transmission is always single-mode transmission within the 1.55 .mu.m band. Such a DS-fiber has sufficiently large effective cross section area Aeff, low bending loss and small dispersion slope to make the fiber suitable for use in WDM transmission systems.