JPS62216933A - Production of base material for optical fiber - Google Patents

Abstract

PURPOSE:To make eccentricity of the core of a base material for optical fiber extremely small by using a material formed with a conical circle as a dummy quartz rod supporting the base material for optical fiber. CONSTITUTION:A base material for optical fiber having large diameter is produced by concentrically arranging a quartz pipe 12 for a jacket opposite to the base material 11 for optical fiber which is arranged in a center, and welding the quartz pipe 12 to the base material 11 by means of an oxyhydrogen burner 17. In this case, a dummy quartz rod 13A for a join which is formed in a conical shape is connected to one end of the base material 11, and the positioning of the quartz pipe 12 is performed by butting one end of the quartz 12 on the tapered face of the quartz rod 13.

Description

[Detailed Description of the Invention] [Field of Industrial Application]. I7) The invention relates to a method for manufacturing an optical fiber preform, and particularly to a method for manufacturing a large diameter optical fiber preform by a rod-in-tube method.

[Conventional technology]

One method for manufacturing large-sized optical fiber preforms is a method called the rod-in-tube method.

FIG. 4 is a schematic diagram showing the manufacturing principle of the rod-in-tube method, in which 1 is an optical fiber preform, and 2 is a quartz tube for a shaker for enlarging the optical fiber preform 1.

A joint quartz rod 3 and a joint quartz tube 4 of the same size are fixed to both ends of the optical fiber base material 1 and the jacket quartz tube 2, respectively, and these are connected in concentric circles with a gap of a predetermined distance via an annular spacer 5. It is arranged in a shape. Each of the quartz tubes 4 for joints and the quartz rods 3 for joints are held by chucks 6A and 6B of a glass lathe and rotated at a constant speed.

Reference numeral 7 denotes an oxyhydrogen burner, which welds (collapses) the jacket quartz tube 2 to the surface of the optical fiber base material 1.

A conventional method for manufacturing an optical fiber preform uses the above-described apparatus to rotate the optical fiber preform 1 and the quartz tube 2 for the jacket at a constant speed while using the flame of the oxyhydrogen burner 7 to produce the quartz rod 4 for the joint, and the quartz rod 4 for the joint. When the outer wall of the jacket quartz tube 2 is heated and moved, for example, from the left end in the direction of arrow A, the portion not supported by the spacer 5 is successively attached to the outer peripheral wall of the optical fiber base material 1, as shown in FIG. It will start to weld.

Therefore, the diameter of the optical fiber preform 1 increases, and a large optical fiber preform can be obtained.

[Problem that the invention seeks to solve]

Although this manufacturing method can easily increase the size of the optical fiber base material by collapsing, the oxyhydrogen burner 7
If the initial heating temperature and moving speed of the optical fiber are not sufficiently controlled, for example, as shown in FIG.
The joint quartz rod 3 holding the joint softens first due to heating, and then the joint quartz tube 4 softens and may bend as shown by the dashed-dotted line before it attaches to the center joint quartz rod 3. .

As a result, the jacket quartz tube 2, which is subsequently welded to the optical fiber base material 1, sticks eccentrically to the optical fiber base material 1, and as shown in FIG. There is a problem in that the area of the portion 20 of the quartz tube 2 is not concentric.

Also, quartz tube for joint4. and quartz rod for joint 3
Each jacket for quartz tube 2. In order to maintain the concentric circular shape, it is necessary to accurately connect the optical fiber base material 1 to the optical fiber base material 1, and it takes time and effort to connect these, and at the same time, the spacer 5 is required, which reduces work efficiency. There is a problem.

This invention was made to solve these problems, and by making slight improvements to the manufacturing method, it is possible to reduce the eccentricity of the core of a large-sized optical fiber base material, and to improve the workability of the welding process. This is done so that

[Means for solving problems]

In the method for manufacturing an optical fiber preform of the present invention, a quartz rod for a joint that supports an optical fiber preform is formed into a conical shape, and a quartz tube for a jacket can be abutted against the tapered surface of the quartz rod. It is.

[Effect]

The quartz rod for the joint connected to the optical fiber base material is formed into a conical shape, so by abutting one end of the quartz tube for the jacket against the tapered surface of this conical quartz rod for the joint, the optical fiber base material is connected to the optical fiber base material. When the collapsing is started at the same time as the positioning with respect to the material is performed and the spacer becomes unnecessary, the jacket quartz tube first softens along the tapered surface of the conical joint quartz rod.

As a result, the collapse of the jacket quartz tube occurs concentrically with respect to the optical fiber base material, and the core eccentricity of the produced large-diameter optical fiber base material can be made extremely small.

〔Example〕

FIG. 1 is a schematic diagram showing the method for manufacturing an optical fiber preform according to the present invention, and similarly to FIG. 4, 11 is an optical fiber preform, 12 is a quartz tube for jacket, and 13A is a chuck 15 of a glass lathe.
The optical fiber base material 11 is connected to one end of a conical joint quartz rod (hereinafter referred to as a dummy quartz rod) having an outer diameter supported by the dummy quartz rod. Further, 13B is a dummy quartz rod connected to the other end of the optical fiber tJ material 11, and is fixed to the other chuck 16B of the glass lathe.

A dummy quartz tube 14 is connected to support the other jacket quartz tube 12, and this dummy quartz tube is also fixed to the chuck 16A.

As described above, the method for manufacturing an optical fiber preform of the present invention involves precisely setting the alignment between the dummy quartz rod 13A, which is formed to have a conical tapered surface P, and the optical fiber preform 11. The other end of the optical fiber preform 11 is fixed to the chuck 16B via a dummy quartz rod 13B as in the conventional case. Then, as in the past, the jacket quartz tube 12 with the dummy quartz tube 14 connected to the other end is inserted and pressed against the tapered surface P of the dummy quartz rod 13A, and the other end is held in the chuck of a glass lathe. 16A.

Then, one end of the optical fiber preform can be arranged concentrically by the tapered surface P even without a spacer.

Next, in this arrangement state, heating is started by the oxyhydrogen burners 17 placed at three points, for example, and as the jacket gradually moves in the direction of the arrow, the quartz tube 12 for the jacket is softened by the heating.
is deformed along the tapered surface P as shown in FIG. 2, and comes to be welded to the optical fiber/heke material 11. Therefore, the collapse progresses to the right without changing the rotation center of the optical fiber base material 11, and the jacket quartz tube 12 is concentrically welded to the optical fiber base material 11, resulting in a large diameter optical fiber base material. can be generated.

Then, when the dummy quartz rod (tube) is cut and removed when the collapse is completed over the entire length of the jacket quartz tube 12, a large diameter optical fiber m material is obtained.

As described above, the optical fiber preform of the present invention is configured such that a concentric state is ensured at the starting point of the collapse by the dummy quartz rod 13A having a tapered surface, so that the jacket quartz tube 12 is softened and deformed. In this case, the concentric circles are not distorted at the collapse starting point because they are reduced along this tapered surface. As a result, if the optical fiber preform 11 and the dummy quartz rod 13A are accurately aligned, a concentric, large-diameter optical fiber preform without eccentricity can be easily produced.

The tapered surface of the conical dummy quartz rod 13A is shown in FIG. 3(a).
Alternatively, it may be slightly curved as shown in FIG. 3(b).

Furthermore, as shown by the dotted line in FIG.
It may be fixed to

〔Effect of the invention〕

As explained above, in the method for manufacturing an optical fiber preform of the present invention, a dummy quartz rod having a conical surface is used as a dummy quartz rod to support the optical fiber preform. The jacket quartz tube can be easily positioned, and when the jacket quartz tube is deformed at the collapse starting point, it can easily maintain a concentric circular shape, and eccentricity is maintained even with the subsequent collapse progress. This has the effect of being able to induce less

In addition, only one dummy quartz tube is required to connect to the jacket quartz tube, and at least one annular spacer can be omitted, making welding work easier than in conventional manufacturing methods.
This has the advantage of improving workability.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an embodiment of the method for manufacturing an optical fiber preform of the present invention, Fig. 2 is an explanatory diagram showing the progress of collapse, and Figs. 3 (a) and (b) are illustrations of dummy quartz rods. A side view showing another embodiment, FIG. 4 is a sectional view of the layout of a conventional optical fiber preform manufacturing method, FIG. 5 is an explanatory diagram showing the progress of conventional collapse, and FIG. FIG. 3 is a sectional view showing the situation. In the figure, 11 is the optical fiber base material, 12 is the quartz tube for the jacket, 13A is the quartz rod for the joint (dummy quartz rod), 1
5, 16A, and 16B are chucks of a glass lathe, and 17 is an oxyhydrogen burner.

Claims (2)

[Claims] (1) A quartz tube for jacketing is arranged concentrically with respect to the optical fiber base material placed in the center, and the quartz tube for jacketing is welded to the optical fiber base material using an oxyhydrogen burner to create a large diameter In the method for manufacturing an optical fiber preform, a quartz rod for a joint formed in a conical shape is connected to one end of the optical fiber preform, and the quartz tube for a jacket is connected to a tapered surface of the conical quartz rod for a joint. A method for manufacturing an optical fiber preform, characterized in that the jacket quartz tube is positioned by abutting one end of the jacket quartz tube. (2) Claim (1) characterized in that the heating by the oxyhydrogen burner starts near the end of the quartz tube for the jacket that is abutted against the tapered surface of the quartz rod for the joint. A method for manufacturing an optical fiber preform as described in Section 1.