Abstract: Disclosed is an optical fiber, which includes: a core positioned at the center of an optical fiber to have the maximum refractive index within the optical fiber; an inner clad surrounding the core to have the minimum refractive index within the optical fiber; and an outer clad surrounding the inner clad to have a refractive index lower than that of the core and higher than that of the inner clad, wherein a difference ?ncore-inner—clad between the refractive index of the core and the minimum refractive index of the inner clad is within the range of 0.00615 to 0.00645, and a difference ?nouter—clad-inner—clad between the refractive index of the outer clad and the minimum refractive index of the inner clad is 0.0006 or more.

Abstract: Disclosed is a method for fabricating an optical fiber preform. The method includes: (a) growing a first soot preform on a starting member along a lengthwise direction of the starting member by a soot deposition; (b) dehydrating the first soot preform; (c) sintering the dehydrated first soot preform, to obtain a first glassed optical preform; and (d) elongating the first optical fiber preform by heating the first optical fiber with a heat source that excludes hydrogen, wherein the first glassed optical fiber is elongated by means of only a heat source that excludes the use of hydrogen.

Abstract: Vapor Axial Deposition (VAD) apparatus and method is provided. The VAD apparatus includes a first torch, a second torch, a thermometer, a controller, and a moving device. The first torch grows a core by depositing a soot at an end of a soot preform arranged on an axis. The second torch grows a clad by depositing a soot on the face of the core. The thermometer detects the temperature of the end of the soot preform along the axis and the temperature of an other/lower portion of the core. The controller calculates a difference between a temperature (T1) of the end of the soot preform and a temperature (T4) of a lower portion of the core and controls the movement of the soot preform according to the difference. The moving device moves the soot preform along the axis according to the instruction of the controller.

Abstract: Disclosed is a method for fabricating an optical fiber having attenuation loss, in which non-uniformity of the attenuation loss in the lengthwise direction of the optical fiber is equal to or less than 0.05 dB/km in the wavelength band of 1383 nm and an average value of the attenuation loss is equal to or less than 0.35 dB/km. The method comprising the steps of (a) fabricating a soot preform while maintaining an average temperature of a core surface at a level equal to or less than 1000° C. and temperature variation of the core surface according to a growing length of the soot preform in a range of ?10 to 10° C./cm, fabricating an optical fiber preform by dehydrating, consolidating and vitrifying the soot preform and (c) drawing the optical fiber from the optical fiber preform under a temperature range between 1900 to 2300° C.

Abstract: An optical fiber having reduced residual stress discontinuity is disclosed. The optical fiber includes a core which is an optical transmission medium and a clad for surrounding the core. The residual stress discontinuity at an interface between the core and the clad is 20.0 MPa or less, which is represented by an absolute value of a difference between a minimum axial stress at (r/a)=0.8-1.1 and a maximum axial stress at (r/a)=1.0-1.2, wherein a is the radius of the core and r is a radius measured from the center of the core.

Abstract: Disclosed is a vapor axial deposition apparatus. The vapor axial deposition apparatus includes a first torch, a second torch, a temperature measuring unit and a controller unit. The first torch deposits soot on a distal end of a soot preform aligned with a vertical axis to thereby grow a core. The second torch deposits soot on an outer circumferential surface of the core to thereby grow a clad. The temperature measuring unit detects the temperature distribution of an end portion of the soot preform along the vertical axis. The controller unit determines first and second relative maximum temperatures T1 and T3, and relative minimum temperature T2 between T1 and T3 in the detected temperature distribution, and controls T1 to be within a predetermined range and the greater one of the difference (T1?T2) and (T3?T2) to not exceed a predetermined temperature.

Abstract: A plasma apparatus is disclosed. The plasma apparatus includes an internal electrode having a hollow section for receiving precursor gas and oxygen gas therein, an external electrode accommodating the internal electrode therein while forming a gap therebetween in such a manner that inert gas and oxygen gas are introduced into the gap. The plasma apparatus also includes a power source for applying a DC voltage or a radio frequency (RF) AC voltage to the internal and external electrodes in order to generate plasma between the internal and external electrodes.

Abstract: A method for fabricating a multimode optical fiber preform having a longitudinal uniformity is provided. The method of fabricating includes performing a plurality of radial deposition passes using a thermal source while inserting raw materials into a glass tube. A reference chemical core shape index is set to determine a refractive index profile of a preform section. A core shape index distribution of each longitudinal deposition pass varying in a longitudinal direction of the glass tube is set such that an error of a reference chemical core shape index distribution in the longitudinal direction of the preform defined by the reference chemical core shape index is compensated for and such that a uniform chemical core shape index is obtained in the longitudinal direction. Deposition is performed while an amount of raw materials corresponding to a preset chemical core shape index is inserted in each longitudinal deposition pass of each radial deposition pass.

Abstract: An optical fiber having reduced residual stress discontinuity is disclosed. The optical fiber includes a core which is an optical transmission medium and a clad for surrounding the core. The residual stress discontinuity at an interface between the core and the clad is 20.0 MPa or less, which is represented by an absolute value of a difference between a minimum axial stress at (r/a)=0.8-1.1 and a maximum axial stress at (r/a)=1.0-1.2, wherein a is the radius of the core and r is a radius measured from the center of the core.

Abstract: The present invention relates to an optical fiber and a planar waveguide for achieving a uniform optical attenuation, which comprises a core co-doped with a first metal ions having an optical absorption coefficient of a negative slope in a particular wavelength band and a second metal ions having an optical absorption coefficient of a positive slope in a predetermined wavelength band.

Abstract: The present invention relates to an optical fiber and a planar waveguide for achieving a uniform optical attenuation, which comprises a core co-doped with a first metal ions having an optical absorption coefficient of a negative slope in a particular wavelength band and a second metal ions having an optical absorption coefficient of a positive slope in a predetermined wavelength band.