JP2876256B2 - Manufacturing method of optical fiber preform - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method for manufacturing an optical fiber preform in which precutting of an optical fiber preform is performed at an optimum timing in a pretreatment performed before the optical fiber preform is sent to a drawing step.

2. Description of the Related Art Conventionally, in the production of an optical fiber, first, an optical fiber preform is first produced, and this preform is drawn and thinned (formed into a fiber). When drawing, one end of the optical fiber preform obtained by the VAD method, the external method, etc.
It is necessary to perform separation, tapping, flame polishing and the like, and conventionally, for example, it is performed by an apparatus as shown in FIG. For example, the upper and lower frames 2 and 3 of the vertical glass lathe 1
An oxyhydrogen burner that is vertically moved by the traverse mechanism 8 on the lathe 1 while holding the optical fiber preform (quartz rod) 6 through the chucks 4 and 5 therebetween and rotating the optical fiber preform 6. From 7, a flame is sprayed to heat the vicinity of the lower end of the optical fiber preform 6, cut off the tip, and perform the tapping process. In practice, when the lower end of the optical fiber preform 6 is softened by heating, for example, the lower frame 3 of the lathe 1 is cut down by pushing it down in the direction of arrow A, and is processed into a thin tip so that it can be set in the drawing device at the same time. ing. The optimal timing for separating this optical fiber preform is
As described above, it is optimal to heat the cut-off portion of the base material for a certain period of time and reach a temperature at which the central portion of the base material is fluidized (fluidization temperature). Was visually judged by the operator by looking at the color and shape of the surface of the base material.

[Problems to be solved by the invention]

For this reason, the worker needs meticulous attention and delicate skill based on his or her experience, and furthermore, there is a variety of problems due to the individual differences in the judgment of each worker. For example, if the timing of separation is too fast due to insufficient heating, the lower frame 3 is not easily separated even if it is pushed down in the direction of arrow A, and the force is applied to the upper part of the optical fiber preform. There is a possibility that the dummy glass supporting the base material is broken and the base material itself falls or falls off from the upper chuck 2. However, if you increase the heating time, the separation will go smoothly,
There has been a problem that the cutting time becomes longer and the working efficiency is reduced. Further, as the environment for determining the timing of the separation is difficult because the environment for determination is in the vicinity of the oxyhydrogen burner 7 and at a high temperature and with high brightness, the surface color and shape of the optical fiber preform are not considered. The environment is not suitable for making the delicate judgment of the operator visually. Obviously, visual observation also causes problems such as visual impairment of workers. The present invention has been made in view of such a conventional situation.

[Means for Solving the Problems]

The feature of the present invention is that the both ends of the optical fiber preform before the drawing step are gripped, the vicinity of the lower end of the optical fiber preform is heated by a burner flame, the tip is cut off, and the tapping process is performed. In the performing step, the temperature of the surface of the optical fiber preform is detected by a temperature sensor, and when the temperature of the optical fiber preform is at an optimum temperature, the optical fiber preform is cut off.

[Action]

In this method, the temperature sensor detects the optimal temperature at which the optical fiber preform is separated, and the detected information enables separation at an optimal timing, and the separation can be automated.

【Example】

FIG. 1 shows an embodiment of a method for manufacturing an optical fiber preform according to the present invention. The device system shown in FIG. 2 is substantially the same as the device system shown in FIG. 2, but in this device system, a temperature sensor 11 for detecting the surface temperature of the optical fiber preform (quartz rod) 6 is provided. As the temperature sensor 11, for example, a small TV camera with a built-in temperature sensor or the like can be used. This camera measures and detects the surface temperature of the optical fiber preform 6 as well as the surface image of the optical fiber preform 6 to be cut off. . Image information and temperature information from the camera are transmitted to, for example, an external controller (a control unit including a computer or the like) 12
And compares the measured temperature with the optimal cutting temperature set in the controller 12 in advance. When the measured temperatures match, for example, the lower frame 3 is moved down by a moving mechanism (not shown) to lower the optical fiber preform. The lower end of the optical fiber preform 6 is cut out by the flame from the oxyhydrogen burner 7, and after the separation, the oxyhydrogen burner 7 is retracted to a predetermined position by the traverse mechanism 8. It is good to let. Further, if a monitor 13 such as a CRT or a liquid crystal display is connected to the controller 12, the operator can also directly observe the heating state of the surface of the fiber preform 6. In each of the above embodiments, the vertical type glass lathe 1 was used, but the present invention is not limited to this.
That it can be applied when using a horizontal glass lathe,
Of course.

【The invention's effect】

As apparent from the above description, according to the method for manufacturing an optical fiber preform according to the present invention, the following excellent effects can be obtained. (1). In the pre-treatment before the drawing step, a temperature sensor for detecting an optimum cutting temperature of the optical fiber preform is installed, so that an optimum cutting timing is automatically obtained. Therefore, the burden on the operator is greatly reduced, and there is no occurrence of an erroneous determination of the optimal timing, and problems such as adverse effects on vision and visual impairment are fundamentally solved. (2). Also, according to the detected temperature information from the temperature sensor,
Automatic lowering of the lower frame and control of the traverse mechanism and the oxyhydrogen burner via an external controller make it easy to perform automatic cutting and automatic tapping simultaneously with the automatic cutting, thereby achieving significant labor savings. (3). Of course, these automations can also improve the working environment.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an example of an apparatus system for implementing a method for manufacturing an optical fiber preform according to the present invention, and FIG. 2 is an apparatus for implementing a conventional method for manufacturing an optical fiber preform. It is the schematic explanatory drawing which showed the system. In the figure, 1 ... lathe, 6 ... optical fiber preform, 7 ... oxyhydrogen burner, 8 ... traverse mechanism, 11 ... temperature sensor, 12 ... controller, 13 ... monitor,

Claims (1)

(57) [Claims] In the step of gripping both ends of an optical fiber preform before a drawing step, heating the vicinity of the lower end of the optical fiber preform with a flame of a burner, cutting off the tip, and performing a tapping process, A method for producing an optical fiber preform, comprising detecting a temperature of a preform surface with a temperature sensor, and separating the optical fiber preform when the temperature reaches an optimum temperature.