JPH0687624A - Production of base material for optical fiber - Google Patents

Abstract

PURPOSE:To provide a method for producing base material for optical fiber having. stable quality that causes no ruggedness on the surface of soot. CONSTITUTION:In a method in which glass fine particles 15 formed by feeding glass raw material and combustion gas from a burner 14 are deposited on the periphery of a rotating target 11 to produce a base material for porous glass, when the traverse direction of the burner is reversed, the reversal position is adjusted so that the glass fine particles may not be deposited on the target tracing the same spiral while reversing the directon of rotation of the target.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical fiber preform, and more particularly to a method for producing an optical fiber preform by depositing glass particles produced in a flame on the glass preform.

[0002]

2. Description of the Related Art As one of methods for producing a porous glass preform as a raw material for an optical fiber preform, a glass raw material is flame-hydrated in a flame formed by ejecting a glass raw material and a combustion gas from a burner. There is known a method of decomposing, synthesizing glass fine particles, and depositing them on the outer periphery of a target to form a glass fine particle deposit. In this way,
Glass particles are deposited on the surface of the target by rotating the target or the target in a fixed direction and reciprocating either the burner or the target in the axial direction of the target. The optical fiber preform is manufactured by subjecting the obtained porous preform to heat treatment for dehydration and transparent vitrification.

[0003]

However, when the porous glass preform is manufactured by the conventional method of rotating the target in a certain direction, there is a problem that the soot surface has irregularities.

That is, the fine glass particles ejected from the burner 14 are deposited on the target 11 in the outward path in a spiral shape as shown in FIG. 3A, for example.
On the other hand, when returning, the spiral is drawn in the opposite direction as shown in FIG. Since the two spirals having different directions intersect with each other in this manner, the soot surface has irregularities as shown in FIG.

When such a porous glass preform for an optical fiber is heated and then drawn to produce a fiber, surface irregularities affect the production of a fiber of stable quality.

[0006] Therefore, an object of the present invention is to provide a method for producing a porous glass preform for optical fibers in which the soot surface does not have irregularities.

[0007]

In order to solve the above-mentioned problems, the present invention provides a rotating target from one end to the other end, and then by reversing from the other end to the one end, An optical fiber mother comprising a step of continuously depositing glass fine particles generated by supplying a glass raw material and a combustion gas from a burner by reciprocating the target and the burner relatively to each other, on the outer periphery of the target. In the method for manufacturing a material, when the target and the burner are relatively reciprocally moved, the rotation direction of the target is reversed, and this reversal is the phase of the spiral drawn by the glass particles deposited on the target, and the forward path. Provided is a method for manufacturing an optical fiber preform, which is performed so as not to coincide with the return path.

As the combustion gas supplied to the burner,
H ₂ and O ₂ can be used, and SiCL ₄ or GeCl ₄ is used as the soot raw material.

The manufacturing method of the present invention can be carried out in either a device in which the target rotates in-situ and the burner makes a traverse motion, or a device in which the burner is fixed and the target traverses while rotating. it can.

FIG. 1 shows an example of a manufacturing apparatus of a type in which both ends of a target are supported and a burner is traversed. The target 11 has supports 16 and 17 at both ends thereof.
The target rotating mechanism 18 and 19 rotates in a predetermined direction at a predetermined speed. A burner 14 is installed below the target, and a glass raw material and a combustion gas are injected from the burner 14 to deposit glass particles 15 produced in the flame on the outer periphery of the target.

The burner 14 is mounted on the burner base 20 and can be moved at a predetermined speed in the length direction of the target by the burner moving mechanism 21.

The manufacturing method for manufacturing the optical fiber porous preform using the above-described manufacturing apparatus will be described below.

First, for example, the target 11 is rotated at a predetermined speed in the direction of arrow A in FIG. 1, and the burner 14 installed below one end 12 of the target is moved at a predetermined speed in the direction of arrow C. Let When the burner 14 reaches the vicinity of the other end 13 of the target 11, the rotation direction of the target is reversed (the direction of arrow B in FIG. 1) and the burner is moved in the direction of arrow D.

When the burner is inverted at a position where the phases of the spirals drawn by the glass particles deposited on the surface of the target exactly match each other in a reciprocating manner, as shown in FIG. 4 (b),
Since it is deposited in the same spiral shape and unevenness is generated, it is not preferable,
It is necessary to set the inversion position so that the phases do not match.

[0015]

In the manufacturing method of the present invention, when the burner and the target are moved relative to each other, the rotation direction of the target is changed according to the movement direction. For this reason, the spiral drawn by the glass particles deposited on the soot surface has the same direction during reciprocation, and thus the unevenness caused by the intersection of two spirals having different directions does not occur on the soot surface. .

Further, when the direction of movement is changed, the phases of the spirals drawn by the glass particles deposited on the surface of the target do not match at the time of reciprocation, that is, the spiral phases drawn by the forward traverse are not changed. In order to prevent the spiral due to the reverse traverse from being drawn in the same phase,
The reversal position is adjusted so that the half pitch phase is shifted. Therefore, the glass particles are uniformly deposited on the surface of the target. Therefore, it is possible to obtain a porous glass preform for optical fibers in which the soot surface does not have irregularities.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

Using a glass rod for core having a diameter of 20 mmφ and a length of 1000 mm as a target, soot synthesis was carried out by ejecting a glass raw material and a combustion gas from a burner. The amount of soot raw material charged to the burner is
It was set to 30 g / min in terms of SiO ₂ .

First, the target was rotated at 100 rpm and the burner was traversed at a speed of 1000 mm / min. When the burner was traversed by about 1000 mm, the target rotated about 100 times, and the pitch of the spiral drawn by the glass particles deposited on the soot surface was about 1 at this time.
It was 0 mm. FIG. 2A shows a schematic diagram of the deposition state of the glass particles on the target in this step.
The fine glass particles 15 ejected from the burner 14 were deposited on the target 11 in a spiral shape in such a direction.

Next, the burner was traversed by about 100 mm under the same conditions except that the direction of rotation of the target was reversed and the direction of movement of the burner was reversed. In addition,
The surface phase is shifted by a half pitch between forward and backward.
FIG. 2B shows a schematic view of the deposition state of the glass particles on the target in this step. In this way, the glass particles 15 were deposited on the target 11 in a spiral shape in the same direction as the spiral obtained by the forward traverse. The obtained soot surface was very smooth as shown in FIG.

As a comparative example, soot synthesis was performed using the same target and burner as in the example, while rotating the target under the same conditions and traversing the burner at about 1000 mm / min. At this time, the target rotated about 100 times and the pitch of the spiral obtained on the surface was about 10 mm.

Then, the burner is reversed without changing the direction of rotation of the target, and under the same conditions, about 1000 mm / min.
Was traversed at and soot synthesis was performed. The obtained soot surface had irregularities as shown in FIG.

[0023]

As described in detail above, according to the method of the present invention, a porous preform for optical fibers having a smooth soot surface without irregularities can be obtained. From this porous preform for optical fibers, An optical fiber preform of stable quality can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an apparatus used in the method of the present invention.

FIG. 2 (a) is a schematic view showing a deposition state of soot on a target in the forward traverse of the manufacturing method of the present invention. (B) The schematic diagram which shows the deposition state of the soot on the target in the reverse traverse of the manufacturing method of this invention.

FIG. 3 (a) is a schematic view showing a deposition state of soot on a target in the conventional traverse of the manufacturing method. (B) The schematic diagram which shows the deposition state of the soot on the target in the reverse traverse of the conventional manufacturing method.

FIG. 4 (a) is a schematic view showing the surface of a porous preform for optical fibers manufactured by the method of the present invention. (B) The schematic diagram which shows the surface of the porous preform for optical fibers when the rotation direction of the target is changed and the phases match during reciprocation.

FIG. 5 is a schematic view showing the surface of a porous preform for optical fibers manufactured by a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Porous base material manufacturing apparatus for optical fibers, 11 ... Target 12 ... One end of target, 13 ... The other end of target, 1
4 ... Burner 15 ... Glass fine particles, 16 ... Target support, 17 ...
Target support 18 ... Target rotating mechanism, 19 ... Target rotating mechanism, 20 ... Burner stand 21 ... Burner moving mechanism.

Claims (1)

[Claims] 1. A glass by rotating the target and the burner relative to each other from one end of the rotating target to the other end, and then by reversing the target to the other end from the other end. In a method for producing an optical fiber preform, which comprises a step of continuously depositing glass fine particles produced by supplying a raw material and a combustion gas from a burner, a relative reciprocation of the target and the burner. An optical fiber characterized by reversing the direction of rotation of the target during movement, and this reversing is performed so that the phase of the spiral drawn by the glass particles deposited on the target does not match in the forward and return paths. Base material manufacturing method.