JP2004035376A - Method and apparatus for manufacturing preform for optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lead a gas flow of a gas supplying unit upward of a chamber from below of a starting member such as a core material so that the gas flow is not directly blown onto a soot deposited body. <P>SOLUTION: When an optical fiber preform is formed by forming an outer layer part 3 such as a clad part by subjecting silicon tetrachloride to flame hydrolysis to form glass fine particles by using an oxyhydrogen flame burner 6 installed below the starting member 4 and depositing the formed glass fine particles on the starting member 4 in a chamber 2, the gas supplying units 7 are each installed at the both ends of the oxyhydrogen flame burner 6 so that the gas flow is blown obliquely upward to the wall surface 2b of the chamber 2 from below of the starting member 4 and led to the upper part of the chamber 2 in order to blow the gas flow upward of the chamber 2 from below of the starting member 4 by each gas supplying unit and to deposit the glass fine particles. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a preform for an optical fiber and an apparatus for producing an optical fiber preform for synthesizing and sintering an oxide as glass particles from a gas phase state by a flame hydrolysis reaction, and particularly to a gas supply apparatus for flame hydrolysis. The present invention relates to a method and apparatus for manufacturing an optical fiber preform for depositing glass fine particles by spraying a gas flow from below a starting member such as a core material to above a chamber.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known a method for manufacturing an optical fiber preform in which a flame hydrolysis reaction is performed to synthesize an oxide as glass fine particles from a gas phase state and sinter to produce the optical fiber preform.
[0003]
As shown in FIGS. 3 (a) and 3 (b), this manufacturing method deposits a porous glass around the core glass rod 101 by an external method. The outlets 103 are provided independently of each other, and at the same time as the formation of the porous glass preform, the glass fine particles are deposited while blowing a clean gas flow over the entire length of the core glass rod 101 to form a soot deposit 104 for an optical fiber. A base material can be formed (see Japanese Patent Application Laid-Open No. 5-116979). By providing the air curtain gas ejection port 103 separately from the deposition burner ejection port 102, (1) a lump of undeposited soot, which is a source of foreign matter and bubbles, can be blown off from the soot deposit. (2) Since the flow of the generated glass fine particles can be suppressed so as not to spread greatly, the glass fine particles can be guided to the soot deposit body 104 neatly. The deposition efficiency can be increased by enlarging the temperature difference with the flame.
[0004]
[Problems to be solved by the invention]
However, in such a method of manufacturing a preform for an optical fiber, (1) the soot deposit body 104 is rapidly cooled by the gas flow 110 blown from the air curtain gas jet port 103, so that the soot deposit body 104 is cooled during or after deposition. (2) The deposition soot is blown off by the gas flow 110 blown from the air curtain gas ejection port 103 to reduce the deposition efficiency. (3) The thermal power of the flame from the deposition burner ejection port 102 When the diameter of the soot deposit body 104 is increased as shown in FIG. 3B, or the intensity of the gas flow 110 from the air curtain gas jet port 103 increases, the flame flow from the deposition burner jet port 102 increases. Since the strength of 111 is stronger, there is a problem that the flame flow 111 cannot be completely suppressed by the gas flow 110.
[0005]
In the case of (3), if the gas flow 110 is further strengthened, the difficulty of (3) can be solved, but the effects of (1) and (2) are more pronounced.
[0006]
The present invention has been made in order to solve such conventional difficulties, and is intended to prevent the gas flow of the gas supply device from directly blowing onto the soot deposit from below a starting member such as a core material to above the chamber. It is an object of the present invention to provide a method of manufacturing a preform for an optical fiber and an apparatus for manufacturing the same, which can guide the method.
[0007]
[Means for Solving the Problems]
The method for producing an optical fiber preform of the present invention, which achieves the above object, comprises depositing glass fine particles produced by flame hydrolysis of silicon tetrachloride with an oxyhydrogen flame burner on a starting member in a chamber. A method for producing an optical fiber preform in which a gas flow is blown from below a starting member toward above a chamber by a gas supply device to deposit glass fine particles in forming an optical fiber preform by forming a portion. In the above, the gas flow of the gas supply device can be blown from below the starting member toward the wall surface of the chamber obliquely upward to guide the gas flow upward of the chamber.
[0008]
Further, the apparatus for manufacturing a preform for optical fibers of the present invention that achieves the above object is characterized in that silicon tetrachloride is flame-hydrolyzed on a starting member in a chamber by an oxyhydrogen flame burner installed below the starting member. In forming the outer layer portion by depositing the glass fine particles generated by forming the base material for the optical fiber, the gas supply device blows a gas flow from below the starting member toward the upper part of the chamber to blow the glass fine particles. In the apparatus for manufacturing an optical fiber preform for depositing a gas, the gas supply device blows the gas flow from below the starting member toward the wall surface of the chamber obliquely upward to guide the gas flow to above the chamber. These are installed at both ends of the oxyhydrogen flame burner.
[0009]
According to the method and the apparatus for manufacturing the optical fiber preform, the gas flow of the gas supply device is blown from below the starting member toward the wall surface of the chamber obliquely above, and the gas flow is blown upward of the chamber. So that the gas stream does not hit the soot deposits directly.
[0010]
Further, in the apparatus for manufacturing a preform for an optical fiber of the present invention, the gas supply device blows the gas flow from below the starting member toward the wall surface of the chamber obliquely upward to guide the gas flow upward of the chamber. The louver is preferably provided. This makes it possible to rectify the gas flow.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of a method for manufacturing a preform for an optical fiber and an apparatus for manufacturing the same according to the present invention will be described with reference to the drawings.
[0012]
A manufacturing apparatus as a preferred embodiment to which the method for manufacturing a preform for optical fiber of the present invention is applied, for example, as shown in FIGS. A chamber 2 serving as a reaction furnace for producing an optical fiber preform, and a rotating mechanism 5 for holding and rotating the starting member 4 in the chamber 2 horizontally. An oxyhydrogen flame burner 6 for depositing an outer layer portion 3 made of glass fine particles produced by flame hydrolysis of silicon tetrachloride on a starting member 4 being rotated by a rotating mechanism 5; A gas supply device 7 provided with a gas turbine, an exhaust hood 8 disposed to face the oxyhydrogen flame burner 6 and exhausting exhaust gas generated by a flame hydrolysis reaction by the oxyhydrogen flame burner 6, and connected to the exhaust hood 8. It includes a gas moving duct 9, and an exhaust fixed duct 10 exhaust moving duct 9 is connected to the outer surface 2a of the inserted chamber 2.
[0013]
The rotation mechanism 5 can rotate the starting member 4 by a rotation drive unit 50 such as a motor provided outside the chamber 2, so that the size of the chamber 2 can be reduced.
[0014]
The oxyhydrogen flame burner 6 generates silicon fine particles by flame-hydrolyzing silicon tetrachloride in an oxyhydrogen flame by igniting by supplying silicon tetrachloride, oxygen gas and hydrogen gas in a predetermined distribution amount. Thus, it is arranged in the chamber 2 located below the starting member 4 of the rotation mechanism 5 so that the starting member 4 can reciprocate linearly in the axial direction.
[0015]
The gas supply device 7 is provided with a gas supply so that an air curtain 70 of the gas flow can be substantially formed over the maximum length of the outer layer 3 for the optical fiber preform that can be manufactured with this device. The device itself may be formed in a horizontal rectangular shape and a plurality of gas supply units may be arranged in a line, but the shape and structure are not limited to these. As shown in FIG. 1B, the gas supply device 7 blows the gas flow from below the starting member 4 attached to the rotating mechanism 5 toward the wall surface 2b of the chamber 2 obliquely above. In order to guide the flow to the upper part of the chamber 2, they are provided at both ends of the oxyhydrogen flame burner 6 in the chamber 2 when viewed from the axial direction of the starting member 4 of the rotating mechanism 5. Thereby, when blowing the gas flow of the gas supply device 7 from below the starting member 4 toward above the chamber 2, the curtain by the gas flow, that is, the air curtain 70 is prevented from directly hitting the soot deposit. Can be.
[0016]
Further, the gas supply device 7 includes a louver 71 for blowing the gas flow from below the starting member 4 toward the wall surface 2b of the chamber 2 obliquely above and starting the gas flow above the chamber 2. . This makes it possible to rectify the gas flow. The gas discharged from the gas supply device 7 may be any gas such as an inert gas such as a nitrogen gas, a helium gas, or an argon gas, as long as it is a clean gas filtered by a filter or the like. .
[0017]
The exhaust hood 8 reciprocates linearly in synchronization with the movement of the oxyhydrogen flame burner 6, and is connected to the outer surface 2 a of the chamber 2 so as to be arranged substantially parallel to the reciprocating linear movement direction of the exhaust hood 8. A reciprocating linear motion is performed by the exhaust moving duct 9 inserted into the exhaust fixed duct 10. The portion of the exhaust moving duct 9 that moves linearly in the reciprocating linear motion direction of the exhaust hood 8 in the exhaust fixed duct 10 is formed of a straight pipe. Thereby, it is possible to smoothly linearly move in the exhaust fixed duct 10.
[0018]
Such a moving mechanism (not shown) for linearly moving the exhaust moving duct 9 in the exhaust fixed duct 10 includes, for example, installing a rail near the exhaust moving duct 9 in parallel with the reciprocating linear movement direction of the exhaust hood 8. In order to synchronize the reciprocating movement of the exhaust moving duct 9 and the oxyhydrogen flame burner 6, a method of moving the exhaust moving duct 9 along a rail via wheels attached to the exhaust moving duct 9 is considered. , Respectively, are connected to a control device (not shown). Note that this synchronization method is not limited to this, and mechanical synchronization may be performed.
[0019]
Further, between the exhaust fixed duct 10 and the exhaust moving duct 9 inserted into the exhaust fixed duct 10, the exhaust gas exhausted from the exhaust moving duct 9 enters the chamber 2 via the exhaust fixed duct 10. An exhaust airtight means 11 is provided so as not to return. This prevents undeposited soot (generated glass fine particles) and unreacted glass raw material from floating in the chamber 2. As such an exhaust airtight means 11, for example, a Teflon (registered trademark) cylindrical sealing member may be fitted between the exhaust moving duct 9 and the exhaust fixed duct 10.
[0020]
The rotation drive unit 50 of the rotation mechanism 5 rotates the starting member 4 from outside the chamber 2. At this time, each of the chambers 2 is controlled so that dust does not enter the chamber 2 from outside the chamber 2. The through portions are each air-sealed.
[0021]
The operation of the thus-configured optical fiber preform manufacturing apparatus 1 will be described below.
[0022]
First, the starting member 4 is set on the rotating mechanism 5. The starting member 4 includes not only a core material and a core material having a thin clad portion but also a core material. Next, the starting member 4 is rotated by the rotation drive unit 50 of the rotation mechanism 5 and the silicon tetrachloride is flame-hydrolyzed by the oxyhydrogen flame burner 6 to generate the outer layer part 3 made of glass fine particles such as clad. The glass fine particles generated by the flame hydrolysis are attached to and deposited on the rotating starting member 4, and the oxyhydrogen flame burner 6 is reciprocated linearly in parallel with the axial direction of the starting member 4 to remove the glass fine particles. The outer layer 3 serving as a clad is formed by being deposited evenly in the axial direction of 4. Thereby, an optical fiber preform made of a soot laminate having a clad portion can be obtained.
[0023]
Further, each gas supply device 7 installed at both ends of the oxyhydrogen flame burner 6 blows a gas flow from below the starting member 4 attached to the rotating mechanism 5 toward the wall surface 2b of the chamber 2 obliquely above. In addition, since the gas flow can be guided above the chamber 2, the air curtain 70 can be prevented from directly hitting the soot deposit. Thereby, {circle around (1)} the air curtain 70 due to the gas flow of each gas supply device 7 does not directly hit the soot deposit, and it is possible to eliminate a rapid decrease in the flame temperature of the oxyhydrogen flame burner 6. (2) The glass particles from the oxyhydrogen flame burner 6 hit the soot deposit without being blown off, so that the deposition efficiency is improved. (3) The gas flow of the gas supply device 7 is applied to the wall surface of the chamber 2. Because of the spraying, soot adhesion to the wall surface is reduced, so that it is possible to obtain a specific effect such that soot that causes bubbles is reduced, and cleaning is facilitated.
[0024]
【Example】
Further, an experiment for depositing glass fine particles was performed under the following conditions, and Examples and Comparative Examples were compared. In each of the examples and comparative examples, the supply amounts of silicon tetrachloride, oxygen gas, and hydrogen gas fed into the oxyhydrogen flame burner, and the ejection amount of the gas flow ejected from the gas supply device are the same, and thus the description is omitted. .
[0025]
Example In this example, a deposition experiment was performed using the manufacturing apparatus 1 shown in FIG.
[0026]
Comparative Example 1
In Comparative Example 1, the gas flow (air) of the gas supply device 202 was directly blown against the outer layer 3 together with the flame of the oxyhydrogen flame burner 201 in the production apparatus 200A shown in FIG.
[0027]
Comparative Example 2
Comparative Example 2 is a manufacturing apparatus 200B shown in FIG. 2B, in which the gas flow (air) of the gas supply device 202 is directly blown to the outer layer portion 3 together with the flame of the oxyhydrogen flame burner 201. An air supply port 204 was provided on each of the wall surfaces 203a and 203b, and clean air passed through the filter was supplied.
[0028]
Comparative Example 3
Comparative Example 3 is a production apparatus 300 shown in FIG. 2C, in which gas supply devices 302 are provided at both ends of an oxyhydrogen flame burner 301, and each gas supply device 302 directly blows a gas flow (air) to the outer layer 3. I put it on.
[0029]
As a result of the experiment, in the example, no crack was generated in the soot deposit, the deposition rate was 5.5 g / min, and the contamination in the chamber was small. On the other hand, in Comparative Example 1, cracks were generated during the soot deposition, the deposition rate was 3.4 g / min, and there was much dirt in the chamber. In Comparative Example 2, cracks were formed after the soot deposition was completed. However, the deposition rate was 5.0 g / min, the amount of dirt in the chamber was large, and in Comparative Example 3, no crack was generated in the soot deposit, and the deposition rate was 5.5 g / min. It was confirmed that dirt in the chamber increased.
[0030]
【The invention's effect】
As is apparent from the above description, according to the method for manufacturing the optical fiber preform of the present invention and the apparatus for manufacturing the same, the gas flow of the gas supply device is blown from below the starting member toward the wall surface of the chamber obliquely above. The soot gas flow can be directed to the upper part of the chamber so that the gas flow does not directly hit the soot deposit, so that the deposit does not crack during or after soot deposition, and the deposition efficiency is improved. Better, and less dirt in the chamber.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a preferred embodiment of a method for manufacturing an optical fiber preform and an apparatus for manufacturing the same according to the present invention, wherein FIG. 1 (a) is an explanatory view and FIG. .
FIG. 2 is an explanatory view showing a comparative example by a deposition experiment.
3A and 3B are explanatory diagrams showing a conventional method for manufacturing a preform for optical fiber, wherein FIG. 3A is a diagram when the diameter of the soot laminate is small, and FIG. 3B is a diagram when the diameter of the soot laminate is large.
[Explanation of symbols]
1 ··· Optical fiber base material manufacturing apparatus 2 ···· Chamber 3 ····· Outer layer part 4 ····· Starting member 6 ····· Oxy-hydrogen flame burner 7 ··· ... Gas supply device 71 ... Louver

Claims (3)

In order to form an outer layer by depositing glass fine particles generated by flame hydrolysis of silicon tetrachloride with an oxyhydrogen flame burner on a starting member in a chamber, a gas is supplied to form an optical fiber base material. In a method for producing a preform for an optical fiber, in which a gas flow is blown from below the starting member toward above the chamber by an apparatus to deposit the glass fine particles,
The optical fiber preform, wherein the gas flow of the gas supply device is blown from below the starting member toward a wall surface of the chamber obliquely above to guide the gas flow upward of the chamber. Production method. An outer layer portion is formed on the starting member in the chamber by depositing glass fine particles generated by flame hydrolysis of silicon tetrachloride with an oxyhydrogen flame burner installed below the starting member, and forming an outer layer portion for an optical fiber. In forming the base material, in a manufacturing apparatus of a base material for an optical fiber that deposits the glass fine particles by blowing a gas flow from below the starting member toward above the chamber with a gas supply device,
The gas supply device blows the gas stream from below the starting member toward a wall surface of the chamber obliquely above and at both ends of the oxyhydrogen flame burner so as to guide the gas stream to above the chamber. An apparatus for manufacturing a preform for an optical fiber, the apparatus being provided for each. The gas supply device includes a louver for blowing the gas flow from below the starting member toward a wall surface of the chamber obliquely upward to guide the gas flow upward of the chamber. The apparatus for manufacturing a preform for an optical fiber according to claim 2.

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