JPS6110039A - Preparation of parent material for optical fiber - Google Patents

Abstract

PURPOSE:When a parent material for optical fiber is produced through the chemically lining deposition in gas phases, an earpick-shaped rod is used to scrape out the undesired oxide deposition in the support tube on the exhaustion side to enable easy production of a parent material with good optical fiber properties. CONSTITUTION:When a quartz tube 1 is used to produce a parent material for optical fiber through the lining deposition in gas phases, a rod 21 with an earpick-shaped end 21A is set in the support tube 3 on the exhaustion side and the undesired oxides depositing in the support tube are scraped off from the wall, for example, the rod is reciprocated, as it is supported with a bar 30 and the quartz tube is rotated. Then, the earpick end is turned down by 180 deg. and the oxides 12 are scraped out of the tube 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a quartz-based optical fiber preform by an internal chemical vapor deposition method, and particularly to a method for removing unnecessary oxides.

Modified chemical vapor deposition method (modified chemical *
apor DeposHion Method)
Today, it is the most widely used.

This internal chemical vapor deposition method is based on 5i, which is the raw material for glass.
CL4. GeCl4. POCl2. BBr3
This is a method in which raw material gases such as the above are fed together with oxygen into a heated quartz glass tube, and a glass layer serving as a core having a higher refractive index than the outer wall is deposited and synthesized on the inner wall surface of the quartz glass tube.

The optical fiber preform thus obtained can be heated to 2000° C. or higher and drawn to form an optical fiber with a desired diameter.

At this time, care must be taken to prevent impurities from entering the core of the optical fiber preform.

[Conventional technology]

The conventional method of manufacturing an optical fiber preform using the internal chemical vapor deposition method is shown in FIG. 3, a cross-sectional view showing the core layer forming process, and
This will be explained with reference to a cross-sectional view of a main part showing the unnecessary oxide removal process shown in the figure.

In Fig. 3, 1 forms the fiber nod of the optical fiber, for example, an outer diameter of 20mm, an inner diameter of 17B, and a length of 1000mm.
It is a slender hollow quartz tube of m length.

At both ends of the quartz tube I, the quartz tube 1 is attached to a glass lathe 4.
A support tube (for example, an outer diameter of 3
An elongated hollow quartz tube with an inner diameter of 3Q+u and a length of 400+n is fused. Of these two support tubes, the one supported by the driving side chuck 5 mounted on the bevel 7 of the glass lathe 4 is called the exhaust side support tube (indicated by reference numeral 3), and the driven side chuck 6 The other supported by is called the input side support pipe (indicated by reference numeral 2).

The end of the input-side support pipe 2 is constricted and connected to the gas supply device IQ via a rotating shaft 9.

The gas supply device 10 uses 5iCL4, which is a raw material for glass,
Ge1l:L4. POCl2. This is a device that stores raw material gas such as BBr3 and oxygen and supplies it to the quartz tube 1.

The oxyhydrogen burner 8, which reciprocates on the bed 7 parallel to the axis of the quartz tube 1, heats the outer peripheral surface of the quartz tube 1 to 1300°C to 1600°C, and heats the raw material gas inside the quartz tube 1. It causes an oxidation reaction.

The forward speed of this oxyhydrogen burner 8 (referring to the movement from the input side support pipe 2 side to the exhaust side support pipe 3 side, code Xi) speed is relatively slow, for example, 180 mm per minute, and the backward speed (code X2) is relatively slow, for example. For example, it returns quickly at 1500 ml per minute.

Using the device described above, drive the glass lathe 4 and rotate the quartz tube 1 (the input side support tube 2 and the exhaust side support tube 3 also rotate), and open the gas supply bag ff1l.
The raw material gas is blown into the quartz tube 1 from O, and the oxyhydrogen burner 8 is given reciprocating motion to uniformly heat the quartz tube 1.

As a result, a 5i02 glass layer containing oxides such as Ge, P, and Br as dopants is deposited on the inner wall of the quartz tube 1 due to a thermal oxidation reaction of the raw material gas in the quartz tube 1, and the core layer 11 is deposited on the inner wall of the quartz tube 1. form.

In addition, by advancing the oxyhydrogen burner 801 times, the thickness
Since a core film of about 110l1 is deposited, the deposited layer reaches a thickness matching the outer diameter to core diameter ratio of the optical fiber.
Repeat this operation. After that, the supply of raw material gas is stopped,
Increase the firepower of oxyhydrogen burner 8 to 170 quartz tubes.
It is heated to around 0°C to soften it, and the hollow quartz tube l is made solid by the action of surface tension.

On the other hand, in this series of core layer forming steps, a part of the heated raw material gas flows out to the exhaust side support pipe 3 and is deposited as unnecessary oxides 12 in the exhaust side support pipe 3.

Since the exhaust side support pipe 3 is not heated, this unnecessary oxide 12 has weak adhesion to the pipe wall and can be easily peeled off.

However, when the amount of unnecessary oxide material 2 increases, the connection hole between the quartz tube 1 and the exhaust side support tube 3 becomes nearly clogged, the flow of raw material gas is disturbed, and the optical fiber characteristics deteriorate.

In addition, if a particularly large amount of particles is deposited in the exhaust side support tube 3, it will flow back into the quartz tube 1 and mix into the core layer 11.

In order to prevent this and obtain a high-quality optical fiber preform, it is necessary to insert an unnecessary oxide removal step at a desired time during the core layer forming step.

The conventional method for removing unnecessary oxides is carried out by inserting the suction pipe 14A of the suction fan 14 into the exhaust side support pipe 3, as shown in FIG.

That is, when the oxyhydrogen burner 8 reaches the vicinity of the exhaust side support pipe 3, the suction pipe 14A is inserted and driven to suck out the unnecessary oxides 12 that have been deposited in the exhaust side support pipe 3 with a weak adhesive force. It is being discharged.

[Problem that the invention seeks to solve]

However, since the above-mentioned conventional method for removing unnecessary oxides is a method of suctioning and discharging the unnecessary oxides in the exhaust-side support tube, the pressure inside the quartz tube decreases.

Therefore, the amount of raw material gas or oxide fine powder deposited in the quartz tube partially fluctuates, causing disturbance in the core layer.
There is a problem that the optical fiber characteristics deteriorate.

[Means for solving problems]

The above-mentioned problems with the conventional technology include a means for inserting and removing a scratching rod whose tip is shaped like an ear scraper along the pipe wall of the exhaust side support pipe from the opening side, and a means for inserting and removing the scratching rod from the opening side along the pipe wall of the exhaust side support pipe, and a method for inserting and removing the scratching rod at a predetermined pressure into the exhaust side support pipe. and a means for rotating the scratching bar 180 degrees within the exhaust side support pipe, and in the process of forming a core layer on the quartz tube, the scratching bar is rotated while the quartz tube is being rotated. Insert the tip along the upper wall of the exhaust side support pipe connected to the quartz tube, move the scratching rod 180 degrees concavely at the joint with the quartz tube, and then This problem is solved by the means of the present invention, which removes unnecessary oxides deposited in the exhaust side support pipe by pulling it out along the exhaust side support pipe.

[Effect]

According to the above means of the present invention, by inserting a scratching rod along the upper pipe wall while rotating the exhaust side support pipe,
Unnecessary oxides adhering to the entire surface of the pipe wall of the exhaust side support pipe are scraped off onto the upper pipe wall surface, and in the drawing process, a discharge work is performed outside the pipe, which also serves as the scraping work.

In addition, since it has a means to press the scratching rod against the wall of the exhaust side support pipe with a predetermined pressure, unnecessary oxides can be scraped off reliably, and if a stronger resistance than necessary is applied, the scratching rod can be There is no risk of escape and damage to the exhaust side support pipe and quartz pipe.

〔Example〕

The gist of the present invention will be specifically explained below with reference to illustrated examples. Note that the same reference numerals indicate the same objects throughout the figures.

Fig. 1 is a block diagram of one embodiment of the present invention, and (a) and (b) respectively show the order of the steps, and Fig. 2 (a), (b), and (C) each show the main parts of the rotating mechanism section. It is a perspective view, and (d) is a cross-sectional view of the reference numeral M section shown in (C).

In FIG. 1, a removal device W20 is installed on the opening side of the exhaust side support pipe 3.

The removal device 20 includes a mounting base 23 that reciprocates on two guide rails 24 installed parallel to the axis of the exhaust side support pipe 3, and a scratcher mounted so that it can be inserted into the exhaust side support pipe 3. A rotation mechanism section 22 installed on the mounting base 23 that imparts a desired rotation to the rod 21, a drive section that drives the mounting base 23 as desired, and an exhaust side support pipe 3 that moves the scratching rod 21 at a predetermined pressure. means including a support bar 30 for pressing against the tube wall of the tube.

One end of a tension coil spring 29 is mounted on the exhaust side support pipe 3 side of the mounting base 23, and a tension coil spring 28 is mounted on the opposite side.
One end of the is tightly attached.

The other end of each of the tension coil spring 28 and the tension coil spring 29 is the end of a traction rope 27 stretched between a pair of driving pulley 25 and driven pulley 26, which are installed opposite to each other with the guide rail 24 in between. It is tightly attached to the section via a connecting piece 31 (see Fig. 2).

Therefore, when the driving pulley 25 is driven to rotate in the forward direction by a power source (not shown), the mounting base 23 moves forward toward the exhaust side support pipe 3 (indicated by symbol X3, and its speed is, for example, 2 m/mi).
n) and the scratching rod 21 is inserted into the exhaust side support pipe 3.

Further, when the drive pulley 25 is rotated in the reverse direction, the mounting base 23 moves backward (indicated by the symbol x4, and the speed is, for example, 2 m/ll1i
n) The scratching rod 21 is pulled out from the exhaust side support pipe 3.

When the scratching rod 21 moves forward or backward, if abnormal resistance is applied to the tip 21A of the scratching rod 21, the tension coil spring 28. Tension coil spring 29 (tension is, for example, both 2
00g) acts as a damper, and the movement of the scratching bar 21 is stopped regardless of whether the mounting base 23 moves forward or backward.

That is, no impact or abnormally large force is applied to the exhaust side support pipe 3, and the exhaust side support pipe 3 and the quartz tube 1
prevent damage. This is particularly effective in the portion where the inner diameter of the pipe is reduced at the connection portion between the exhaust side support pipe 3 and the quartz tube 1.

As a means for pressing the scratching rod 21 against the wall of the exhaust side support pipe 3 with a predetermined pressure, when the ear-scraping tip 21A of the scratching rod 21 is in contact with the upper wall of the exhaust side support pipe 3, A support bar 30 is attached to support the rod 21 from below.

The support bar 30 is attached to an air cylinder that is driven vertically via a compression coil spring (both not shown) having a predetermined elasticity, and the scratch bar 21 is reversed and the exhaust side support pipe 3
When it comes into contact with the upper pipe wall, it is configured to descend and move away from the scratching rod 21.

As shown in FIG. 2(d), the end of this scratching rod 21 is inserted into the tube of a pipe-shaped pinion shaft 35, and is pivotally supported by a support pin 37 passing through the pinion shaft 35 in the diametrical direction. . A weight 36 is fixed to the farthest end of the scratching rod 21 at the back of the support bin 37. This weight 36 is used to adjust the gravity on the distal end portion 21A side as desired.

In this way, the scratching bar 21 is pivotally supported at its end within the tube of the pinion shaft 35.

Therefore, the tip 21A of the scratching rod 21 is pressed against the upper pipe wall of the exhaust side support pipe 3 by the support bar 30 with a predetermined contact pressure (for example, 70 g), and , is pressed with a predetermined pressure (for example, 70 g) by its own weight.

As shown in FIG. 2, the details of the rotation mechanism section 22 are as shown in FIG. This rack 33 is the mounting base 2
It is driven by a motor (not shown) mounted at the bottom of 3.

At the top of the rack 33, parallel to the guide rail 24,
A pipe-shaped pinion shaft 35 is pivotally supported, and the pinion shaft 35
A pinion 32 that meshes with a rack 33 is fixed to the pinion 32 .

The meshing relationship between the rack 33 and the pinion 32 is such that the scratching bar 21 is always facing upward, and the rack 33
3 is stopped. Then, the mounting base 23 moves forward, and the dead center of the forward movement (the tip 21A is located between the exhaust side support pipe 3 and the quartz tube 1)
When the rack 33 reaches the point where it connects with the rack 33, the motor is driven and the rack 33 starts sliding movement. Therefore, the pinion 32 rotates and the tip 21A faces downward.

When the scratching bar 21 has rotated 180 degrees and the tip 21A is completely facing downward, a switch 34 mounted near the rack 33 is activated to turn off the motor and remove the rack 3.
3 stops.

Next, when the mounting base 23 moves backward and the tip 21A is pulled out from the exhaust side support pipe 3, the motor reverses and the rack 33 returns, the scratching bar 21 rotates 180 degrees in the opposite direction, and the tip 21A points upward. becomes.

The removal device 20 is configured as described above.

Therefore, while rotating the exhaust side support pipe 3, the scratching rod 2
1, the tip 21A of the exhaust side support pipe 3 is directed toward the upper wall of the exhaust side support pipe 3, supported by the support bar 30, and inserted while being pressed with a predetermined pressure. The oxide 12 is scraped off onto the upper tube wall surface.

Further, when the scratching bar 21 is rotated 180 degrees at the forward dead center and the tip 21A is pulled out along the upper pipe wall of the exhaust side support pipe 3, unnecessary oxides 12 deposited on the pipe wall are scraped off.
The unnecessary oxides 12 dropped in the forward movement are also discharged out of the tube.

In addition, the scratching rod 21 is applied to the exhaust side support pipe 3 with a predetermined pressure.
Since the scraping rod 21 has a means for pressing against the pipe wall of the exhaust side support pipe 3, the unnecessary oxide 12 can be scraped off reliably, and if a stronger resistance than necessary is applied, the scraping rod 21 escapes and the exhaust side support pipe 3
And there is no risk of damaging the quartz tube 1.

〔Effect of the invention〕

As explained above, the present invention mechanically uses a scratching stick to
By carrying out the removal work, unnecessary oxides can be reliably removed without damaging the exhaust side support tube and the quartz tube, and the optical fiber has an excellent practical effect of improving the optical fiber characteristics. This is a method for manufacturing a fiber base material.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, in which (a) and (b) each show the order of the steps, and (a), (b), and (c) in FIG. A perspective view, (d) is a sectional view of the part M shown in (c), FIG. 3 is a sectional view showing the core layer forming process, and FIG. 4 is a sectional view of the main part of the conventional unnecessary oxide removal process. . In the figure, 1 is a quartz tube, 2 is a support tube on the input side, 3 is a support tube on the exhaust side, 4 is a glass lathe, 5 is a chuck on the driving side, 6 is a chuck on the driven side, 8 is an oxyhydrogen burner, and 9 is a rotating joint. , 10 is a gas supply device, 11 is a core layer, 12 is an unnecessary oxide, 14 is a suction fan, 20 is a removal device, 21 is a scratching rod, 22 is a rotating mechanism section, 23 is a mounting table, 24 is a guide rail, 25 26 is a driving pulley, 26 is a driven pulley, 27 is a traction lobe, 28, 29 is a tension coil spring, 30 is a support bar, 32 is a pinion, 33 is a rack, 35 is a pinion shaft, and 36 is a weight. Fist f flash (0,) ¥-2 song (II) Y-3 song'#4 drunkenness

Claims (1)

[Claims] In manufacturing an optical fiber preform by an internal chemical vapor deposition method, a means for inserting and extracting a scratching rod having a tip shaped like an ear scraper along the wall of an exhaust side support tube from an opening side, and the scratching rod and means for rotating the scratching rod by 180 degrees within the exhaust side support pipe, and in the process of forming a core layer on the quartz tube. While rotating the tube, insert the tip of the scratching rod along the upper tube wall of the exhaust side support tube connected to the quartz tube, and insert the scratching rod at the connection part with the quartz tube.
1. A method for manufacturing an optical fiber preform, which comprises rotating by 0 degrees and pulling out along the lower wall of the exhaust-side support tube to remove unnecessary oxides deposited in the exhaust-side support tube.