JPH02145452A - Drawing of optical fiber - Google Patents

Abstract

PURPOSE:To draw preform of optical fiber from the top part by drawing the preform of optical fiber covered with a hollow glass cap having the same outer diameter as the preform of optical fiber. CONSTITUTION:Preform 2 of optical fiber is covered with a hollow glass cap 8 having approximately the same outer diameter as the preform of optical fiber. Then the top of the preform 2 is fed to a heating furnace 3, heated by a heater 4, melted and optical fiber 5 is drawn while sending an inert gas from the bottom of the heating furnace 3 toward the top.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of drawing an optical fiber.

[Prior art] Conventionally, optical fibers are drawn using an optical fiber preform supported at the lower end of a support rod 1, as shown in FIG.
The tip of the optical fiber preform 2 is inserted into the heating furnace 3, and while the tip of the optical fiber preform 2 is heated and melted by the heater 4 in the heating furnace 3,
In addition, the optical fiber 5 was spun from the tip of the optical fiber preform 2 while flowing an inert gas such as Ar gas into the heating furnace 3 from the lower part to the upper part. In this case, the optical fiber preform 2 is lowered at a speed proportional to the drawing speed, and the optical fibers 5 are continuously spun. 5
The situation will be as shown in the figure.

4 and 5, the gap 6 for gas rise at the inlet of the heating furnace 3 (diameter difference between the optical fiber base material 2 and the support rod 1) has changed significantly, that is, the gap 6 has become larger and the inert The gas flow (upward flow) changes significantly, that is, the flow velocity of the inert gas increases, which causes a variation in the diameter of the optical fiber 5. For this reason, it is necessary to finish drawing while leaving the upper part of the expensive optical fiber preform 2 and to discard the remaining optical fiber preform 2.

In order to avoid this, conventionally, as shown in FIG. 6, a dummy glass 7 was welded to the optical fiber base material 2 by glass processing and then drawn.

[Problems to be Solved by the Invention] However, the method of drawing an optical fiber in which such a dummy glass 7 is provided has a problem in that an extra and troublesome step of glass processing is required.

An object of the present invention is to provide an optical fiber drawing method that allows drawing from the upper end of an optical fiber preform without requiring glass processing.

[Means for Solving the Problems] To explain in detail the present invention for achieving the above object, the present invention provides a method in which the tip of an optical fiber preform is placed in a heating furnace to be heated and melted, and the heating In an optical fiber drawing method in which an optical fiber is drawn from the tip of the optical fiber preform while flowing an inert gas from the lower part to the upper part of the furnace, a hollow glass having approximately the same outer diameter as the optical fiber preform is used. The method is characterized in that the optical fiber is drawn by placing a cap on the optical fiber preform.

[Function] When the glass cap is placed on the optical fiber mother H in advance in this manner, the glass cap acts in the same way as a dummy glass, and prevents fluctuations in the outer diameter of the optical fiber while also covering the optical fiber mother H. You can now draw lines from the top of the material.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. As shown in FIGS. 1 to 3, in the present invention, the optical fiber base material 2 is covered with a hollow glass plate 11 having an outer diameter approximately the same as the optical fiber matrix 2, and in this state, the The tip of the optical fiber preform 2 is placed in the heating furnace 3 as described above, and the optical fiber is heated while being heated by the heater 4 and an inert gas such as Ar gas is flowed from the bottom to the top of the heating furnace 3. Underline 5. Several types of glass caps 8 with different outer diameter sizes are prepared in advance, and used according to the outer diameter size of the optical fiber preform 2 to be used at that time.

The length of the glass cap 8 is, for example, 150 to 20 Ga.
Make it around +.

When the wire is drawn in this way, even if the upper end of the optical fiber preform 2 enters the heating furnace 3, the glass cap 8 remains at the entrance of the heating furnace 3, as shown in FIG. The gas rising gap 1116 at the inlet does not change (therefore, there is no change in the rising flow, and fluctuations in the outer diameter of the optical fiber 5 can be prevented).

[Effects of the Invention] As explained above, in the optical fiber drawing method according to the present invention, drawing is performed by covering an optical fiber preform with a glass cap having approximately the same diameter as the outer diameter of the optical fiber preform. Therefore, the same effect as when using dummy glass is obtained, and it is possible to draw the optical fiber from the upper end of the optical fiber preform while preventing variations in the outer diameter of the optical fiber. In particular, when a glass cap is used as in the present invention, there is no need for extra and troublesome glass processing as in the case of the method of providing a dummy glass, and there is an advantage that the wire drawing work can be carried out efficiently.

[Brief explanation of the drawing]

Fig. 1 is a side view showing the relationship between the optical fiber preform and the glass cap in the optical fiber drawing method according to the present invention, in which the optical fiber preform is covered with a glass cap, and Fig. 2 is a side view showing the relationship between the optical fiber preform and the glass cap. FIG. 3 is a vertical cross-sectional view showing an example of the implementation state of the optical fiber drawing method according to the present invention, and FIGS. 4 and 5 are drawings of an optical fiber according to the prior art. FIG. 6 is a side view showing a conventional structure in which a dummy glass is provided on the top of an optical fiber preform. DESCRIPTION OF SYMBOLS 1... Support rod, 2... Optical fiber base material, 3... Heating furnace, 4... Heater, 5... Optical fiber, 6...
Gap for gas rise, 7...Dummy glass, 8...Glass cap. Figure Figure Figure Figure Figure

Claims (1)

[Claims] The optical fiber is drawn from the tip of the optical fiber preform by placing the tip of the optical fiber preform in a heating furnace and heating and melting it, while flowing an inert gas from the bottom to the top of the heating furnace. An optical fiber drawing method comprising: placing a hollow glass cap having approximately the same outer diameter as the optical fiber preform over the optical fiber preform, and drawing the optical fiber. Method.