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: Disclosed is a vapor axial deposition apparatus. The vapor axial deposition apparatus includes a first torch, a growth size detecting unit and a controlling unit. The first torch deposits soot on a distal end of a soot preform aligned with a first axis, and is aligned with a second axis. The growth size detecting unit detects an image including a growing point of the soot preform and an end of the first torch. The controlling unit calculates a distance between the soot preform and the first torch along the second axis from the detected image, and moves the soot preform upward based on the calculated distance.

Abstract: An automatic quartz-tube leveling device for automatically measuring the leveling state of an optical-fiber preform on an on-line basis using a modified-chemical-vapor deposition (MCVD) technique is disclosed. A quartz tube is disposed in a horizontal supporting element such as a lathe. A measuring device is provided with a light-emitting device and a light-receiving device, interposing the quartz tube, for measuring an upper eccentric value and a lower eccentric value along a length of the quartz tube. A controller receives the measured upper and lower eccentric values from the measuring device, compares the measured values with predetermined reference values, and specifies a necessary leveling span of the quartz tube. A transfer device then moves to a necessary leveling span of the quartz tube to carry out leveling of the quartz tube, under control of the controller.

Abstract: An automatic quartz-tube leveling device for automatically measuring the leveling state of an optical-fiber preform on an on-line basis using a modified-chemical-vapor deposition (MCVD) technique is disclosed. A quartz tube is disposed in a horizontal supporting element such as a lathe. A measuring device is provided with a light-emitting device and a light-receiving device, interposing the quartz tube, for measuring an upper eccentric value and a lower eccentric value along a length of the quartz tube. A controller receives the measured upper and lower eccentric values from the measuring device, compares the measured values with predetermined reference values, and specifies a necessary leveling span of the quartz tube. A transfer device then moves to a necessary leveling span of the quartz tube to carry out leveling of the quartz tube, under control of the controller.