JPH107429A - Production of preform for optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an efficient production process for a preform of an optical fiber of good quality and an apparatus therefor. SOLUTION: A glass-making feedstock gas, a fuel gas and a combustionaiding gas are jetted from the burner for synthesizing fine particles of glass together with fire flame to form fine particles of glass through the flame hydrolysis car oxidation reaction and blowing the fine particles to the cuter periphery of the rotating bar of the starting material 3. At this time, the angle between the starting material 3 and the jetting direction of the burner 4 is set to 50 deg.-85 deg. whereby the glass soot body for optical fiber preform can be shortened at its tapered bottom end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an optical fiber preform and an apparatus for manufacturing the same.

[0002]

2. Description of the Related Art Generally, an external method (OVD method) is used as a method for producing a glass fine particle deposit (porous glass preform), which is one form of an optical fiber preform. According to this external method, a rod-shaped starting material having a refractive index distribution serving as a core and a clad is rotatably arranged, a burner for synthesizing glass particles is arranged toward the starting material, and reciprocally movable along the starting material. The glass raw material gas, the fuel gas and the auxiliary gas are supplied to the burner and ejected toward the starting material. By spraying the starting material and the burner relatively back and forth along the starting material while spraying the outer periphery of the material, the glass fine particles adhere and accumulate around the starting material to become the optical fiber preform. It is for producing a deposit. A specific manufacturing method using this external method is disclosed in
Japanese Patent Application Laid-Open No. 243530 and Japanese Patent Application Laid-Open No. 2-243531 are known. That is, according to the manufacturing method described in Japanese Patent Application Laid-Open No. 2-243530, a target member as a starting material is attached to a frame so as to be rotatable, and a single burner is reciprocally movable along the target member. From SiCl ₄ , GeC
The glass raw materials such as l ₄ and is ejected from the burner with the combustion supporting gas such as fuel gas and O _2, such as H _2, oxidation in the flame, and the glass particles by hydrolysis reaction or the like, the target member that rotates the glass particles To form a glass fine particle deposit, and when forming the glass fine particle deposit, measure the surface temperature of the glass fine particle deposit with a radiation thermometer and set the surface temperature to a set value. Is to be controlled so that

[0003] Further, the manufacturing method described in Japanese Patent Application Laid-Open No. Hei 2-243531 discloses a method in which a starting member as a starting material is rotatable, a plurality of burners are reciprocally movable along the starting member, and a glass is removed from the burner. It is ejected from each burner together with the raw material, fuel gas, and auxiliary gas, and is oxidized and hydrolyzed in a flame to produce glass fine particles. The glass fine particles are sprayed toward a rotating base member to form a glass fine particle deposit. Prior to the formation of the glass fine particle deposit, the original member is heated to increase the adhesion between the original member and the glass fine particle deposit.

[0004]

However, according to the conventional optical fiber preform manufacturing technology, the proportion of the portion of the manufactured optical fiber preform that can be effectively used as an optical fiber is small, There is a problem that the base material cannot be efficiently manufactured. That is, as shown in FIG. 10, in the glass fine particle deposit A manufactured by the conventional method, the portions B at both ends become tapered. The tapered end portion B is formed by sintering and stretching the glass fine particle deposit A to form a preform. The central portion C of the glass fine particle deposit A (a portion having a constant diameter that is not tapered).
Basic characteristics such as the cutoff wavelength and the mode field diameter are different from those of the optical fiber, and, as a result, the characteristics of the optical fiber are different from those of the central portion C.

In the production of the glass fine particle deposit A as the optical fiber preform, the total length of the glass fine particle deposit A produced as shown in FIG. Are l ₁ and l ₂ , respectively, the ratio η of the glass fine particle deposit A that can be effectively used as an optical fiber is calculated by the following equation (1).

Η = ((l− (l ₁ + l ₂ )) / l) · 100 [%] ‥‥‥ (1) The larger the effective ratio η is, the better, but it is 6 in normal production.
It is about 0 to 65%, and 70% is set as a target value for manufacturing. Since an increase in the effective ratio η directly leads to an improvement in the productivity of the optical fiber, development of a technique useful for improving the effective ratio η in the glass fine particle deposit A as the optical fiber preform is keenly desired. .

The present invention has been made in order to solve the above problems, and provides a method and apparatus for manufacturing an optical fiber preform capable of efficiently producing a high-quality optical fiber preform. The purpose is to do.

[0008]

That is, the present invention provides a method in which a glass raw material gas, a fuel gas and an auxiliary gas are ejected from a burner for synthesizing glass fine particles together with a flame to generate glass fine particles by a flame hydrolysis reaction or an oxidation reaction. In a method of manufacturing an optical fiber preform, the starting material and the burner are relatively reciprocated while spraying the outer periphery of a rotating rod-shaped starting material, and glass particles are attached and deposited around the starting material. A method of manufacturing an optical fiber preform, comprising: spraying glass fine particles onto a starting material by setting the angle between the starting material and the spraying direction of the burner to 50 ° to 85 °.

According to this invention, the burner sprays the glass particles from the oblique direction to the starting material.
The glass particles are sprayed at an angle close to a right angle on the surface of the tapered end of the glass particle stack (optical fiber preform) formed on the outer periphery of the starting material. For this reason,
It is suppressed that the tapered end is deposited and grown along the axial direction of the starting material, and the tapered end of the glass fine particle deposit is formed short. Further, the angle between the starting material and the direction in which the burner is sprayed does not become too small, and the deposition yield of the glass particles does not decrease.

Further, the present invention is a method for manufacturing an optical fiber preform, characterized in that the direction of the burner is changed in accordance with the relative movement of the starting material and the burner.

According to the invention, the burner is oriented so that the glass fine particles are sprayed at an angle close to a right angle to each tapered end of the glass fine particle deposit formed on the outer periphery of the reciprocating starting material. By changing the above, it is possible to suppress the glass particles from being deposited and grown along the axial direction of the starting material at both ends of the glass particle stack. For this reason, both ends of the tapered shape of the glass fine particle deposit are formed short.

Further, the present invention is a method of manufacturing an optical fiber preform, wherein a plurality of burners are used to spray glass fine particles with the same angle between the spraying directions of the respective burners.

According to the invention, it is possible to uniformly and efficiently produce a glass fine particle deposit as an optical fiber preform.

According to the present invention, there is also provided a rod-shaped starting material which rotates by generating a glass fine particle by a flame hydrolysis reaction or an oxidation reaction by ejecting a glass raw material gas, a fuel gas and an auxiliary combustion gas from a burner for synthesizing glass fine particles. In the method for producing an optical fiber preform, the starting material and the burner are relatively reciprocated and the glass fine particles are adhered and deposited around the starting material. A method for producing an optical fiber preform, characterized in that glass particles are sprayed substantially at right angles to the surface of a glass particle deposit body deposited on a starting material while controlling the direction.

According to such an invention, the glass fine particles are always sprayed at an angle close to a right angle on the surface of the glass fine particle deposit formed on the outer periphery of the starting material. Therefore, the deposition and growth of the glass fine particles along the axial direction of the starting material at both ends of the glass fine particle deposit are reliably suppressed, and the tapered ends of the glass fine particle deposit are formed short.

The present invention is also a method for manufacturing an optical fiber preform, wherein the starting material is disposed in a vertical direction.

According to the invention, since the axial direction of the starting material and the direction in which the gravity of the glass fine particle deposit is applied coincide with each other, the glass fine particle deposit is stably supported by the starting material.

Further, the present invention provides a rotating mechanism for rotating a rod-shaped starting material, a glass raw material gas, a fuel gas, and an auxiliary combustion gas, which are jetted to generate glass fine particles by a flame hydrolysis reaction or an oxidation reaction, and to form an outer periphery of the starting material. Burner for synthesizing glass particles by spraying and depositing umbilical glass particles, moving mechanism for relatively reciprocating the starting material and the burner along the axial direction of the starting material, and adjusting the direction in which the burner is sprayed on the starting material An optical fiber preform manufacturing apparatus comprising an adjustment mechanism for performing the above.

According to such an invention, it is possible for the burner to spray fine glass particles from an oblique direction to the starting material. For this reason, the glass fine particles are sprayed on the surface of the tapered end portion of the glass fine particle deposit formed on the outer periphery of the starting material at an angle close to a right angle, so that the tapered end portion extends in the axial direction of the starting material. It is prevented from accumulating and growing along.

The present invention is also an apparatus for manufacturing an optical fiber preform, characterized in that the adjusting mechanism adjusts the angle between the spraying direction of the burner and the starting material in accordance with the relative position between the starting material and the burner.

According to the invention, it is possible to prevent the tapered ends from being deposited and grown along the axial direction of the starting material at both ends of the glass fine particle deposit.

Further, the present invention is characterized in that the adjusting mechanism adjusts the angle between the spraying direction of the burner and the glass fine particles so as to be sprayed at right angles to the surface of the glass fine particle deposit on the starting material. This is a fiber preform manufacturing apparatus.

According to the invention, the tapered ends at both ends of the glass fine particle deposit are reliably prevented from being deposited and grown along the axial direction of the starting material.

The present invention is also an apparatus for manufacturing an optical fiber preform, characterized in that the rotation mechanism can be arranged with the starting material oriented vertically.

According to the invention, since the axial direction of the starting material and the direction in which the gravity of the glass fine particle deposit is applied coincide, the glass fine particle deposit is stably supported by the starting material.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same elements are denoted by the same reference numerals, and the description is omitted.

(Embodiment 1) FIG. 1 is a schematic view of an apparatus for manufacturing an optical fiber preform. As shown in FIG. 1, a manufacturing apparatus 1 for manufacturing an optical fiber preform includes a burner 4 that ejects glass fine particles as a source of a glass fine particle deposit 2 toward a starting material 3, and a starting material 3. It is provided with a rotation moving mechanism 5 for relatively moving the burner 4 and rotating the starting material 3, and an adjusting mechanism 6 for adjusting an angle between the starting material 3 and the spraying direction of the burner 4. Hereinafter, manufacturing apparatus 1
Each part will be described in detail.

In FIG. 1, a rotary moving mechanism 5 is mounted on an upper portion of a reaction vessel 7, and a rod-shaped starting material 3 can be installed in the reaction vessel 7. The reaction vessel 7 has a structure in which the inside and outside are sealed, so that the inside air can be discharged to the outside only from the exhaust port. The rotation moving mechanism 5 includes, for example,
The drive unit 51 includes a drive shaft 51, a rotation shaft 52, and a connection unit 53. The drive unit 51 is installed above the reaction vessel 7 and has a rotation function of rotating a rotation shaft 52 extending from the lower surface thereof (rotation about the axial direction) and a movement function of moving the rotation shaft 52 in the axial direction. As the driving unit 51, a known driving unit such as a motor is used. The rotating shaft 52 extends downward from the driving unit 51 and is provided to pass through the upper surface of the reaction vessel 7. Further, the connecting portion 53 is provided at the lower end of the rotating shaft 52 so as to be able to connect the starting material 3 arranged vertically in the reaction vessel 7. As the connecting portion 53, a known chuck type or the like is used. With this rotation moving mechanism 5, the starting material 3 can be installed vertically in the reaction vessel 7, rotated at an arbitrary speed, and raised and lowered at an arbitrary speed. By raising and lowering the starting material 3,
The burner 4 and the starting material 3 attached to the reaction vessel 7 can be relatively moved. Further, according to the rotation moving mechanism 5, the starting material 3 is installed in the vertical direction.
The direction in which the weight of the glass fine particle deposit 2 deposited on the outer periphery of the substrate 3 is added can coincide with the axial direction of the starting material 3, and the starting fine material 3 can stably support the glass fine particle deposit 2. . Therefore, a large-sized glass particle deposit 2 can be manufactured. Note that the rotation moving mechanism 5 may be configured such that a rotating mechanism for rotating the starting material 3 and a moving mechanism for relatively moving the starting material 3 and the burner 4 are separately provided.

On the other hand, on the side surface of the reaction vessel 7, two burners 4 (burners 4a and 4b) are vertically arranged side by side. The burners 4a and 4b are for spraying fine glass particles, and are connected to the raw material supply device 41, respectively. The raw material supply device 41 sends SiCl ₄ ,
It receives glass raw material gas such as GeCl ₄ , fuel gas such as H _2, and auxiliary gas such as O _2, and gushes them from the opening at the tip to oxidize and hydrolyze in the flame. Glass particles are generated by a reaction or the like. In addition, the gas ejected from the burner 4 by the supply from the raw material supply device 41 is not limited to the glass raw material gas, the fuel gas, and the auxiliary gas, but also includes an inert gas for assisting the generation of the glass particles. .

The burners 4a and 4b are arranged so as to face the starting material 3, so that the fine glass particles can be sprayed toward the starting material 3, and the adjusting mechanism 6 can adjust the spraying direction. ing. For example, the burners 4a and 4b are rotatably mounted on the adjustment driving units 61a and 61b, respectively, so that they can be raised and lowered in the vertical direction.
The elevation control can be arbitrarily controlled by an angle control device 62 connected to 1a and 61b. The burner 4 may be composed of a single burner as long as the direction of spraying the glass fine particles can be adjusted.
It may be composed of three or more burners.

Although the manufacturing apparatus 1 installs the starting material 3 in the vertical direction, the installation direction may be horizontal or oblique (not vertical but non-horizontal). In the manufacturing apparatus 1, the relative movement between the starting material 3 and the burner 4 is performed by moving the starting material 3 with respect to the burner 4. The movement may be performed. Furthermore, in the manufacturing apparatus 1, both the starting material 3 and the burner 4 may be moved and their relative movement may be performed.

Next, a method for manufacturing an optical fiber preform will be described. In FIG. 1, first, a rod-shaped starting material 3 made of two or more types of glass materials having different refractive indexes, that is, a starting material 4 having a core and a clad is prepared, and is connected to the connecting portion 53 of the rotation moving mechanism 5 of the manufacturing apparatus 1. Attach. The starting material 3 is made of two or more types of glass materials having different refractive indexes. The starting material 4 may be made of one kind of glass material. Then, the spraying directions of the burners 4a and 4b are set by the adjusting mechanism 6. That is, the direction of the burners 4a and 4b is set by the adjusting mechanism 6 so that the angle θ formed by the spray direction of the burners 4a and 4b and the axial direction of the installed starting material 3 is 50 ° to 85 °. When setting it,
It is desirable that the burners 4a and 4b arranged side by side have the same orientation. That is, by keeping the directions of the burners 4a and 4b the same, the deposition state of the glass fine particles is made uniform.

Then, in such a state, by driving the drive unit 51 of the rotary moving mechanism 5 to rotate and raise and lower the rotary shaft 52, the starting material 3 is rotated in the reaction vessel 7 in the vertical direction. Move back and forth. At the same time, the burners 4a and 4b are
Glass source gas such as Cl ₄ and GeCl ₄ , fuel gas such as H _2, and auxiliary combustion gas such as O ₂ are respectively supplied and ejected from the tips of the burners 4a and 4b. Then
Flames are blown out from the burners 4a and 4b by the fuel gas and the auxiliary gas, and the glass raw material gas is oxidized in the flames.
The starting material 3 which is turned into a glass particle by a hydrolysis reaction or the like and rotates and reciprocates is sprayed onto the outer peripheral surface. When spraying the glass particles, the burners 4a, 4a
The direction of b is fixed.

By spraying glass particles, the starting material 3
Glass fine particles are gradually deposited on the outer periphery of the glass so that the glass fine particle deposit 2 (soot preform) grows. At that time, as shown in FIG. 1, the end of the glass fine particle deposit 2 has a tapered shape. This is because the glass fine particles sprayed on the glass fine particle deposit body 2 flow along the surface thereof and accumulate, and the end of the glass fine particle deposit body 2 is directed toward the outermost end having a small diameter as shown in FIG. As a result, glass particles flow and grow in a tapered shape.

The angle θ between the spraying direction of the burners 4 (burners 4a and 4b) and the starting material 3 is set to 85 ° or less, so that the length of the tapered end portion of the glass fine particle deposit 2 is shortened. It is possible to do. For example, as shown in FIG. 1, for a starting material 3 arranged in a vertical direction,
When the burner 4 (burners 4a, 4b) is inclined upward from the horizontal (at an angle θ <85 °) and the glass fine particle deposition step is performed, the lower end of the glass fine particle stack 2 is As shown in FIG. 3, the glass fine particles ejected from the burner 4 are ejected substantially at right angles to the end surface. Therefore, the glass particles hardly flow from the end of the glass particle stack 2 to the starting material 3 side, and the length of the tapered end of the glass particle stack 2 is short. On the other hand, at the upper end of the glass particle deposit body 2, as shown in FIG. 2, glass particles ejected from the burner 4 are sprayed at an angle close to parallel to the end surface. However, even when the glass fine particles are sprayed in this way, the length of the tapered end portion is the same as when the starting material 3 and the burner 4 are perpendicular to each other as shown in FIG. 4 (prior art). Therefore,
As the length of the lower end portion of the glass fine particle deposit 2 becomes shorter, the ratio of the tapered end portion to the entire length of the glass fine particle deposit 2 becomes smaller.

Further, by setting the angle θ between the spraying direction of the burners 4 (burners 4a and 4b) and the starting material 3 at 50 ° or more, it is possible to avoid a decrease in the yield of glass fine particles. That is, if the angle θ between the spraying direction of the burner 4 and the spraying direction of the burner 4 is too small, the deposition rate of the glass fine particles ejected from the burner becomes small, and the growth rate of the glass fine particle deposit 2 is affected. Therefore, by setting the angle θ between the spraying direction of the burner 4 and 50 ° or more, a reduction in the yield of glass fine particles can be suppressed. Then, the spraying of the glass fine particles onto the glass fine particle deposit body 2 is continued, and when the glass fine particle deposit body 2 reaches a predetermined diameter, the raw material supply device 41 and the rotation moving mechanism 5 are stopped to stop the glass as the optical fiber preform. The manufacture of the fine particle deposit body 2 ends.

According to the manufacturing method described above, the burner 4
When the angle θ between the spraying direction of the (burners 4a and 4b) and the starting material 3 is set to 50 ° to 85 ° to manufacture the glass fine particle deposit 2, the tapered end of the glass fine particle deposit 2 is produced. , And a high-quality glass particle deposit 2 containing many effective portions can be efficiently produced.

Next, a specific example of the production of an optical fiber preform by a production method using the optical fiber preform production apparatus 1 will be described. As a starting material 3, a material having a core made of SiO ₂ to which GeO ₂ was added and a clad made of SiO ₂ was used, and as shown in FIG.
a, 4b) are directed horizontally or upward from the horizontal, and the angle θ between the starting material 3 and the direction in which the burner 4 is sprayed is 40 °, 50 °.
°, 60 °, 70 °, 80 °, 85 °, 90 °,
In each case, the glass particle deposit 2 was manufactured. As described above, the production of the glass particle deposit 2 is as follows.
The rotation moving mechanism 5 is driven to reciprocate up and down while rotating the starting material 3, and at the same time, the raw material supply device 41 supplies glass raw material gas, fuel gas and auxiliary gas to the burners 4 a and 4 b to supply each burner 4 a 4b, glass fine particles were ejected from the tip, and the glass fine particles were gradually deposited on the outer periphery of the starting material 3. At that time, the distance of the reciprocating movement of the starting material 3 was set to about 1000 mm, and the glass fine particles were sprayed until the outer diameter of the glass fine particle deposit 2 became 150 mmφ.

As described above, the glass fine particle deposits 2 in the spraying direction of the burners 4 were obtained, and as a result, the glass fine particle deposits 2 in the respective spraying directions of the burners 4 were obtained. Both ends of each glass particle deposit 2 were tapered. Then, these glass fine particle deposits 2 were made transparent and formed into preforms, and then drawn to obtain optical fibers. As a result, optical fibers having stable characteristics were obtained except for the tapered ends.

Here, the relationship between the angle θ between the starting material 3 and the spraying direction of the burner 4 at the time of manufacture and the taper length (length of the tapered end) of the glass fine particle deposit 2 after manufacture will be described. As shown in FIG. 5, the ratio η of the glass fine particle deposit 2 after the production, which can be effectively used as an optical fiber, to the angle θ between the spraying direction of the starting material 3 and the burner 4 during the production, and the yield of the glass fine particles during the production Is shown in FIG.
Referring to FIG. 5, the angle θ between the starting material 3 and the spraying direction of the burner 4 is 9
It has been found that as the angle becomes smaller from 0 °, the length of the tapered end portion (taper length) becomes shorter, the angle θ becomes the shortest peak at 50 °, and becomes longer as the angle θ becomes smaller. On the other hand, at the upper end, there is no particular change even if the angle θ between the starting material 3 and the spraying direction of the burner 4 is changed from 40 ° to 90 °. Then, the data of the taper length shown in FIG. 5 are substituted into the above-mentioned equation (1) as l ₁ and l ₂ , respectively, and the ratio η that can be effectively used as an optical fiber for each glass particle deposit 2 is calculated. 6 is the effective ratio η. Referring to FIG. 6, the effective ratio η increases as the angle θ between the spraying directions of the burners 4 decreases from 90 °, and reaches a maximum value at an angle θ of 50 °. This indicates that the smaller the angle θ between the spraying direction of the burner 4 and the manufacturing, the more effective the optical fiber can be obtained from the manufactured glass particle deposit body 2. The effective ratio of 70%, which is the conventional target value, is achieved by setting the angle θ between the spraying directions of the burners 4 to an angle smaller than 85 °.

On the other hand, in FIG. 6, when the angle θ formed by the spraying direction of the burner 4 is set to be smaller than 90 °, the deposition yield of the glass fine particles increases up to 70 °, and the 70 ° becomes a peak. A decreasing trend is shown. If the angle θ is less than 50 °, the yield is less than 50%, which is not suitable in view of the production cost or production efficiency.

In consideration of the effective ratio η and the deposition yield in the glass fine particle deposit 2 as described above, by setting the angle θ between the starting material 3 and the spraying direction of the burner 4 to 50 ° to 85 °, It can be seen that it is possible to efficiently produce a high-quality glass particle deposit 2.

(Embodiment 2) In the manufacture of the optical fiber preform of the first embodiment, the burner 4 is fixed in the direction of manufacture of the optical fiber preform.
The optical fiber preform may be manufactured while changing the direction of the burner 4 according to the reciprocating movement of the optical fiber. That is, the optical fiber preform manufacturing method and the manufacturing apparatus 1a according to the present embodiment change the direction of the burner 4 according to the reciprocating movement of the starting material 3. FIG. 7 is an explanatory diagram of the manufacturing process in this embodiment. The optical fiber preform manufacturing apparatus 1a according to the present embodiment includes a burner 4 (burners 4a and 4b) and a rotation moving mechanism 5 similar to those in the first embodiment. As the adjusting mechanism, an adjusting mechanism 6a having an angle changing function of changing the angle of the burner 4 in accordance with the movement of the starting material 3 during manufacturing is used.

For example, as the adjustment mechanism 6a, the same adjustment drive units 61a and 61b as the adjustment mechanism 6 of the first embodiment are used.
And an angle control device 62a for controlling the driving of the adjustment driving units 61a and 61b in accordance with the movement of the starting material 3. The angle control device 62a drives the adjustment driving units 61a and 61b so that the glass fine particles are sprayed at right angles on the end surface of the glass fine particle stack 2, and adjusts the angle of the burner 4 according to the movement of the starting material 3. It has the function to change. According to the manufacturing apparatus 1a, by having such an adjusting mechanism 6a, the glass particle deposit 2
During the manufacture of the glass fine particles, the glass fine particles can be sprayed substantially at right angles on the surfaces of both end portions of the glass fine particle stack 2. For this reason, the glass particles are prevented from flowing along the surface and being deposited at the end of the glass particle stack 2, and the end of the glass particle stack 2 can be prevented from being tapered.

In the manufacturing apparatus 1a, the burner 4 may be composed of one burner.
It may be composed of three or more burners. Also,
In the manufacturing apparatus 1a, the installation direction of the starting material 3 may be a vertical direction, or the installation direction may be a horizontal direction or an oblique direction (a direction that is not vertical but not horizontal). In addition, in the manufacturing apparatus 1a, if the relative movement between the starting material 3 and the burner 4 is performed, the starting material 3 moves with respect to the burner 4 and the burning device 4 moves with respect to the starting material 3. Alternatively, both the starting material 3 and the burner 4 may be moved and their relative movement may be made.

Next, a method for manufacturing the optical fiber preform according to this embodiment will be described. In FIG. 1, first, the starting material 3 is attached to the connecting portion 53 of the rotation moving mechanism 5. In this state, the driving unit 51 of the rotary moving mechanism 5 is driven to rotate and rotate the rotary shaft 52 so that the starting material 3 is reciprocated in the vertical direction while rotating in the reaction vessel 7. Along with this, glass raw material gas, fuel gas, and auxiliary gas are ejected from the burners 4a and 4b, and glass particles are generated by oxidation, hydrolysis and the like in the flame. Then, the generated glass particles are sprayed on the starting material 3 and gradually deposited on the outer periphery thereof.

When the fine glass particles are sprayed, the direction of spraying of the burners 4a and 4b is changed by the adjusting mechanism 6a to the starting material 3.
It changes according to the movement of. For example, as shown in FIG. 7A, when the burners 4a and 4b are spraying the glass particles on the lower side of the glass particle stack 2 (when the glass particle stack 2 is located above). Burner 4a,
4b with the burners 4a, 4a and 4b as shown in FIG.
When b is spraying glass fine particles on the upper side of the glass fine particle deposit body 2 (when the glass fine particle deposit body 2 is located below), the burners 4a and 4b face downward. For this reason, the glass particles are sprayed at both ends of the glass particle stack 2 at an angle close to a right angle with respect to the surface thereof. Therefore, the glass fine particles are prevented from flowing along the surface of the end portion to the narrowest end portion and being deposited, and the formation of the tapered end portion is suppressed.

The angles of the burners 4a and 4b at the time of spraying the glass particles are set so that the angle between the axial direction of the starting material 3 and the spraying direction is 50 ° to 85 ° as described above. The timing at which the burners 4a and 4b change from upward to downward and from downward to upward may be any time other than when the burners 4a and 4b are spraying both ends of the glass fine particle deposit body 2. That is,
At the lower end of the glass particle deposit 2, burners 4a, 4b
b faces upward, and burners 4a, 4a
What is necessary is just to change the direction of the burners 4a and 4b so that b may face downward. The timing of changing the direction of the burners 4a and 4b is as follows.
Is desirably a time when approaching a steady portion (a portion where the outer diameter is substantially constant) from the end of.

In this manner, the spraying of the glass fine particles is continued, and the production is terminated when the glass fine particle deposit 2 reaches a predetermined diameter.

According to the manufacturing method as described above, the glass fine particles are sprayed at both ends of the glass fine particle deposit body 2 at almost right angles to the surface of each end, so that each tapered end is formed. The portion is prevented from accumulating and growing in the axial direction of the starting material 3. Therefore, the length of the tapered end portion at both end portions of the glass particle deposit body 2 can be reduced.

Next, an example of a specific manufacturing method using a manufacturing method using the optical fiber preform manufacturing apparatus 1a will be described. A starting material 3 having a core made of SiO ₂ to which GeO ₂ is added and a cladding made of SiO ₂ is used, and the angle θ between the starting material 3 and the spraying direction of the burner 4 is ± 6.
The direction of the burners 4 (burners 4a and 4b) was set so as to be 0 °, and the glass fine particle deposit 2 was manufactured.
The manufacturing procedure of the glass particle deposit 2 was performed as described above. At that time, the distance of the reciprocating movement of the starting material 3 is about 1000 m
m, and the glass fine particles were sprayed until the outer diameter of the glass fine particle deposit 2 became 150 mmφ.

In this manner, while changing the spraying direction of the burner 4 downward or upward, the glass fine particle deposit 2
As a result, a glass particulate deposit body 2 having a taper length at both ends (length of a tapered end portion) of 115 mm was obtained. Then, the effective ratio η according to the above equation (1) is 7
7%, and the deposition yield of glass fine particles is 63%.
Thus, a high-quality glass particle deposit 2 was efficiently manufactured. Then, when the glass particle deposit body 2 was made transparent in a sintering furnace and drawn after flame polishing, a large number of optical fibers having stable characteristics were obtained.

(Embodiment 3) In the manufacture of the optical fiber preform according to the second embodiment, the angle (spraying direction) of the burner 4 is constant when the optical fiber preform is manufactured. It may be changed according to the position where the material 3 moves. That is, the optical fiber preform manufacturing method and the manufacturing apparatus 1b according to the present embodiment change the spray angle of the burner 4 according to the relative position with respect to the starting material 3. FIG. 8 is an explanatory diagram of the manufacturing process in the present embodiment. FIG. 9 is an explanatory diagram of the burner angle control in the present embodiment. The optical fiber preform manufacturing apparatus 1b according to the present embodiment includes the same burners 4 (burners 4a and 4b) and the rotary moving mechanism 5 as the manufacturing apparatus 1 according to the first embodiment shown in FIG. As the adjusting mechanism, an adjusting mechanism 6a having an angle changing function of individually changing the angles of the burners 4a and 4b in accordance with the relative position to the starting material 3 at the time of manufacturing is used. For example, as the adjustment mechanism 6b, the same adjustment drive units 61a and 61b as the adjustment mechanism 6 of the first embodiment are used.
And an angle control device 62b that controls the driving of these adjustment driving units 61a and 61b according to the position of the starting material 3. The angle control device 62b drives the adjustment driving units 61a and 61b so that the glass fine particles are sprayed at right angles to the respective surfaces of the constant-diameter central portion and the tapered end portion of the glass fine particle deposit body 2. Has a function. According to the manufacturing apparatus 1b, such an adjusting mechanism 6
By having b, it becomes possible to spray the glass particles at almost right angles on the respective surfaces of the glass particle stack 2 during the production of the glass particle stack 2. For this reason, the glass particles are prevented from flowing along the surface and being deposited at the end portion of the glass particle deposit body 2, and the end portion of the glass particle deposit body 2 is prevented from being tapered.

In this manufacturing apparatus 1b, the burner 4 may be composed of one burner.
It may be composed of three or more burners. Also,
In the manufacturing apparatus 1b, the installation direction of the starting material 3 may be a vertical direction, or the installation direction may be a horizontal direction or an oblique direction (a direction that is not vertical but not horizontal). In addition, the manufacturing apparatus 1b is configured so that the starting material 3 moves with respect to the burner 4 and the burner 4 moves with respect to the starting material 3 if the relative movement between the starting material 3 and the burner 4 is performed. Alternatively, both the starting material 3 and the burner 4 may be moved and their relative movement may be made.

Next, a method for manufacturing the optical fiber preform according to the present embodiment will be described. In FIG. 1, first, the starting material 3 is attached to the connecting portion 53 of the rotation moving mechanism 5. In this state, the driving unit 51 of the rotary moving mechanism 5 is driven to rotate and rotate the rotary shaft 52 so that the starting material 3 is reciprocated in the vertical direction while rotating in the reaction vessel 7. Along with this, glass raw material gas, fuel gas, and auxiliary gas are ejected from the burners 4a and 4b, and glass particles are generated by oxidation, hydrolysis and the like in the flame. Then, the glass particles are sprayed on the starting material 3 and gradually accumulate on the outer periphery thereof.

When the fine glass particles are sprayed, the direction of spraying of the burners 4a, 4b is changed by the adjusting mechanism 6b to the starting material 3.
It changes according to the position of. For example, as shown in FIG. 8A, when the burners 4a and 4b are spraying the glass particles on the center portion of the glass particle deposit body 2 having a constant diameter, the burners 4a and 4b are set in the horizontal direction. When the burner 4a is spraying the glass fine particles on the tapered end of the glass fine particle deposit body 2 as described above, only the burner 4a is directed upward so that the glass fine particles can be sprayed at right angles on the end surface. Although not shown,
When the glass fine particle deposit 2 moves downward and the burner 4b is spraying the glass fine particles on the tapered end of the glass fine particle deposit 2, only the burner 4b faces downward, and the glass fine particles are perpendicular to the end surface. So that it can be sprayed. Such angle control of the burners 4a, 4b may be performed, for example, as shown in FIG. By performing such angle control of the burners 4a and 4b, the glass particles are constantly sprayed at both ends of the glass particle stack 2 at an angle close to a right angle to the surface thereof. Therefore, the glass fine particles are prevented from flowing along the surface of the end portion to the narrowest end portion and being deposited, and the formation of the tapered end portion is suppressed. In this way, the spraying of the glass fine particles is continued, and when the glass fine particle deposit 2 reaches a predetermined diameter, the production is terminated.

According to the manufacturing method described above, the glass fine particles are always sprayed on the surface of the glass fine particle stack 2 at an angle close to a right angle.
The glass particles are prevented from accumulating and growing in the axial direction of the starting material 3 at the tapered ends. Therefore, the length of the tapered end portion at both ends of the glass particle deposit body 2 can be reduced.

Next, an example of a specific manufacturing method using a manufacturing method using the optical fiber preform manufacturing apparatus 1b will be described. As the starting material 3, a material having a core made of SiO ₂ to which GeO ₂ is added and a clad made of SiO ₂ is used, and the angles of the burners 4a and 4b (the starting material 3 and the burners 4a, 4a,
The control of the angle θ with respect to the spraying direction of 4b was performed as shown in FIG. The manufacturing procedure of the glass particle deposit 2 is as described above. At that time, the distance of the reciprocating movement of the starting material 3 was set to about 1000 mm, and the glass fine particles were sprayed until the outer diameter of the glass fine particle deposit 2 became 150 mmφ.

As described above, the glass fine particle stack 2 was manufactured while the spraying direction of the burners 4a and 4b was alternately changed according to the position of the starting material 3, ie, the position of the glass fine particle stack 2, and as a result, the taper at both ends was obtained. The glass fine-particle deposit 2 having a length (length of a tapered end) of 120 mm was obtained. The effective ratio η according to the above equation (1) is 76%
In addition, the deposition yield of the glass fine particles was 65%, and a high-quality glass fine particle deposit 2 could be efficiently produced. Then, when the glass particle deposit body 2 was made transparent in a sintering furnace and drawn after flame polishing, a large number of optical fibers having stable characteristics were obtained.

[0060]

As described above, according to the present invention, the following effects can be obtained.

In other words, by spraying the glass fine particles on the starting material with the angle between the starting material and the direction of spraying the burner being 50 ° to 85 °, the glass fine particle deposit formed on the outer periphery of the starting material is formed. Glass particles are sprayed on the surface of the tapered end of the (optical fiber preform) at an angle close to a right angle, and the tapered end deposits and grows along the axial direction of the starting material. Is suppressed. Therefore, the tapered end of the manufactured optical fiber preform becomes short. In addition, a reduction in the deposition yield of the glass particles can be suppressed. Accordingly, a high-quality optical fiber preform from which a large amount of optical fibers having stable characteristics can be obtained can be efficiently manufactured.

Further, by changing the direction of the burner so that the glass fine particles are sprayed at right angles to each tapered end of the glass fine particle deposit according to the relative movement between the starting material and the burner, the optical fiber preform is changed. In this case, the tapered ends at both ends of the glass fine particle deposit can be shortened, and the quality of the optical fiber preform is improved.

Further, by spraying glass fine particles by using a plurality of burners at the same angle between the spraying directions of the respective burners, a glass fine particle stack as an optical fiber preform can be uniformly and efficiently produced. it can.

Further, by controlling the direction in which the burner is sprayed on the starting material and spraying the glass fine particles substantially at right angles to the surface of the glass fine particle depositing body deposited on the starting material, it is formed on the outer periphery of the starting material. The glass fine particles are always sprayed on the surface of the glass fine particle deposit at an angle close to a right angle, so that both ends of the glass fine particle deposit are reliably suppressed from growing in a tapered shape. For this reason, both ends of the tapered shape of the glass fine particle deposit, which is the optical fiber preform, are short, and a high-quality optical fiber preform can be reliably manufactured.

Further, by disposing the starting material in the vertical direction, it is possible to stably support the glass fine particle deposit as the optical fiber preform, so that a large-sized glass fine particle deposit can be manufactured.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an apparatus for manufacturing an optical fiber preform.

FIG. 2 is an explanatory view of a step of spraying glass fine particles during production of an optical fiber preform.

FIG. 3 is an explanatory view of a step of spraying glass fine particles at the time of manufacturing an optical fiber preform.

FIG. 4 is an explanatory view of manufacturing a conventional optical fiber preform.

FIG. 5 is a diagram showing data of a taper length in a manufactured optical fiber preform.

FIG. 6 is a diagram showing data of an effective ratio and a yield in a manufactured optical fiber preform.

FIG. 7 is an explanatory diagram for manufacturing an optical fiber preform according to the second embodiment.

FIG. 8 is an explanatory diagram for manufacturing an optical fiber preform according to the third embodiment.

FIG. 9 is a diagram illustrating angle control of a burner in manufacturing the optical fiber preform according to the third embodiment.

FIG. 10 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Manufacturing apparatus, 2 ... Glass fine particle deposit (optical fiber preform), 3 ... Starting material, 4 ... Burner, 5 ... Rotational movement mechanism, 6
… Adjustment mechanism

Claims (9)

[Claims] 1. A glass raw material gas, a fuel gas, and an auxiliary combustion gas are ejected from a burner for synthesizing glass fine particles together with a flame to generate glass fine particles by a flame hydrolysis reaction or an oxidation reaction and to the outer periphery of a rotating rod-shaped starting material. A method of manufacturing an optical fiber preform by spraying and relatively reciprocating the starting material and the burner to adhere and deposit glass fine particles around the starting material, wherein the starting material and the burner are 50 ° angle with the spray direction
A method for producing an optical fiber preform, wherein the glass fine particles are sprayed onto the starting material at an angle of about 85 °. 2. The method according to claim 1, wherein the direction of the burner is changed according to the relative movement between the starting material and the burner. 3. The optical fiber preform according to claim 1, wherein a plurality of said burners are used, and said glass fine particles are sprayed by making the angles of said spraying directions of said burners the same. Manufacturing method. 4. A glass raw material gas, a fuel gas and an auxiliary gas are ejected from a burner for synthesizing glass fine particles together with a flame to generate glass fine particles by a flame hydrolysis reaction or an oxidation reaction, and to the outer periphery of a rotating rod-shaped starting material. A method of manufacturing an optical fiber preform by spraying and relatively reciprocating the starting material and the burner to adhere and deposit glass fine particles around the starting material; A method for manufacturing an optical fiber preform, characterized in that the glass fine particles are sprayed substantially at right angles to the surface of the glass fine particle deposit to be deposited on the starting material while controlling the direction. 5. The method of manufacturing an optical fiber preform according to claim 1, wherein said starting material is vertically disposed. 6. A rotation mechanism for rotating a rod-shaped starting material, and a glass raw material gas, a fuel gas, and a combustible gas are ejected to generate glass fine particles by a flame hydrolysis reaction or an oxidation reaction, and the glass fine particles are spread around the starting material. A burner for synthesizing glass fine particles for spraying and depositing glass fine particles, a moving mechanism for relatively reciprocating the starting material and the burner along an axial direction of the starting material, and spraying the burner on the starting material. An optical fiber preform manufacturing apparatus comprising: an adjustment mechanism for adjusting a direction. 7. The apparatus according to claim 6, wherein the adjusting mechanism has a function of adjusting an angle formed by a spraying direction of the burner according to a relative position between the starting material and the burner. Optical fiber preform manufacturing equipment. 8. The adjusting mechanism has a function of adjusting an angle between the spraying direction of the burner and the glass fine particles to be sprayed at right angles to the surface of the glass fine particle depositing body deposited on the starting material. The apparatus for manufacturing an optical fiber preform according to claim 6 or 7, wherein: 9. The apparatus according to claim 6, wherein said rotating mechanism is capable of arranging said starting material vertically.
An apparatus for manufacturing an optical fiber preform according to any one of the above.