JP3675583B2 - Optical fiber preform manufacturing apparatus and manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical fiber preform manufacturing apparatus. In particular, in order to prevent the burner for synthesizing the optical fiber porous base material from being bent due to the weight of the tube for supplying the gas or the glass raw material gas, and making the production of the optical fiber porous base material unstable. Equipment.
[0002]
[Prior art]
According to the conventional optical fiber preform manufacturing method, a burner for synthesizing glass particles is fixed, and a gas for forming a flame in the burner and a glass raw material are supplied to the burner. The tube was connected to the burner supply port. Therefore, since the weight of the connected tube is applied to the burner supply port, the burner is distorted and deflected, the raw material flow ejected from the burner and the direction of the flame become unstable, resulting in production. The quality of the porous base material becomes unstable. In order to improve the positioning accuracy of the burner, it has been proposed to fix the burner to the burner base with a mold (Japanese Utility Model Publication No. 3-22256). However, this method is good for fixing the burner and the burner base, but it cannot prevent the deflection of the connecting tube due to its own weight.
[0003]
In such a conventional method, the weight of the tube connected to the burner acts on the burner and the burner is bent. Especially in the case of a multi-tube burner, the center port has a small outer diameter, so There is a drawback of being easily affected. Therefore, when glass material is allowed to flow through the center port, the direction of the material flow changes in an unstable manner, and the growth rate in the axial direction of the porous base material fluctuates, or a germanium compound is added as an additive for increasing the refractive index. When flowing simultaneously through the burner, the quality becomes unstable, for example, the refractive index of the optical fiber preform manufactured varies in the axial direction.
[0004]
[Problems to be solved by the invention]
In the present invention, the burner in the optical fiber porous base material synthesizing apparatus changes the direction of the flow of the flexible raw material in an unstable manner due to the weight of the tube for supplying the gas or the glass raw material gas. An object of the present invention is to overcome instability factors in which the growth rate in the axial direction varies and the refractive index of the optical fiber preform varies in the axial direction.
[0005]
[Means for Solving the Problems]
The above-described object can be achieved by the following porous fiber base material synthesizing apparatus.
(1) tube that connects the burner of the optical fiber preform synthesis, the burner fixing base for fixing the burner body, a supply device for supplying glass raw material gas to the burner, the burner and the feeding device The burner includes at least a central port through which a glass raw material flows, a combustible gas ejection port or a supplementary gas ejection port, and the combustible gas ejection port or the auxiliary combustion gas ejection port. A multi-tube burner arranged concentrically so as to surround the center port, wherein the end of the center port on the side connected to the glass material supply tube is fixed. Base material manufacturing equipment.
(2) apparatus for manufacturing an optical fiber preform according to (1), characterized in that at least one position more than the fixed connection vicinity of the burner of the tube.
[0006]
(3) The light according to (1) or (2), wherein an end of the central port on the side connected to the glass material supply tube or the tube is fixed to the burner fixing base. Fiber base material manufacturing equipment.
(4) A glass raw material is supplied to a burner, oxidized or hydrolyzed in a flame formed by the burner to generate glass particles, and the glass particles are deposited on the tip or outer periphery of a rotating starting material, In the method for manufacturing a fiber preform, the burner includes at least a central port through which a glass raw material flows and a combustible gas ejection port or an auxiliary combustion gas injection port, and the combustible gas injection port or the auxiliary combustion gas ejection port. A multi-tube burner arranged concentrically so as to surround the center port, a burner fixing base for fixing the burner body, a supply device for supplying glass raw material and gas to the burner, and a burner; and a tube for connecting the supply device, while fixing the ends of said central port side to be connected to the supply tube of a glass material Hikarifu Method of manufacturing an optical fiber preform, which comprises synthesizing the driver preform.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Specific examples of the present invention will be described below with reference to the accompanying drawings. An optical fiber preform synthesizing apparatus as shown in FIG. 1 includes a gas, a raw material supply device 1, a core burner 2, a cladding burner 3, a rotation motor 4, a ball screw 5, a pulling motor 6, a laser projector 7, a light receiving unit 8, It is comprised from the tube 12 which connects the control apparatus 9, each burner 2 and 3, and gas and the raw material supply apparatus 1. FIG. The growth rate of the growth edge of the core part is measured using the laser projector 7 and the light receiving part 8 and input to the control device to control the lifting mechanism of the base material.
[0008]
The tube 12 is supported and fixed by the core tube fixing part 10 and the clad tube fixing part 11 according to the present invention. In general, it is necessary that the position of the burner for synthesizing the optical fiber base material is not changed after being fixed to the equipment. However, even if the burner part is fixed, the burner will bend if its own weight is applied to the tube. It is inevitable that it will occur. Generally, a burner having a structure shown in FIG. 6A is used. FIG. 6A shows a combination of pipes concentrically, and an eight-fold burner is shown as an example. In this burner, glass raw material, fuel gas (H ₂ ), seal gas (Ar), auxiliary gas (O ₂ ), seal gas (Ar), fuel gas (H ₂ ), seal gas (from the center to the outer periphery) Ar) and auxiliary gas (O ₂ ) are flowed. It is preferable to use a gas such as H ₂ or CH ₄ as the fuel gas, O ₂ as the auxiliary combustion gas, and Ar or N ₂ as the seal gas. As the glass raw material, SiCl ₄ , SiHCl ₃ or the like is used, and GeCl ₄ is generally used as the dopant for changing the refractive index.
[0009]
As the burner, in addition to such a multi-tube burner, those having the structures shown in FIGS. 6B and 6C can be used. Of course, the effect of the present invention can be obtained in the same manner regardless of which burner is used. In FIG. 6 (b), since a plurality of auxiliary combustion gas (O ₂ ) outlets are arranged concentrically in the fuel gas (H ₂ ), the heating efficiency is excellent, and FIG. 6 (c) is a square type. This is particularly advantageous in terms of adjusting the refractive index distribution of the core portion.
In the present invention, since the tube connecting the burner, the gas, and the raw material supply device is fixed, the weight of the tube does not act on the burner, and the burner does not bend. Therefore, the flame formed by the burner and the direction of the raw material flow are stabilized, and a stable optical fiber preform can be manufactured.
[0010]
FIG. 2 shows a structure in which a burner is fixed on a movable stage. The raw material and gas supply device 1 and a burner ( multi-tube burner ) 2 are connected by a tube 12 , and the burner 2 and the tube 12 are respectively burners. It is fixed by a burner fixing base 13 that can be moved by a fixing part 14 and a tube fixing part 15 . In a structure where the burner is fixed on a movable stage, when the stage is moved and the burner is moved, the relative position between the burner connection port and the tube fixing point changes, so the shape of the tube changes. Unreasonable force may act on the burner connection port. To prevent this, the tube fixing point is placed on the stage to which the burner is fixed so that the tube fixing point moves in accordance with the movement of the burner position. In other words, by fixing the tube to the stage, even if the burner position is moved by moving the stage, the tube also moves at the same time, so the relative positional relationship between the burner and the tube does not change, and the tube is deformed to the burner. Unreasonable force does not act. In addition, as a stage for making the burner movable, a stage provided with a translational movement of XYZ three axes and a rotation axis capable of changing the angle of the burner is used.
[0011]
In general, when a multi-tube burner is used, the center port of the multi-tube burner has a small outer diameter, so if a tube for supplying gas or raw material is attached, the tube will be bent by its own weight. In order to prevent this, the device ( 1 ) fixes the center port of the burner so that no deflection occurs even when the tube is subjected to its own weight. In this case, fixing the burner center port as shown at 16 in FIG. 3 to burners solid Jodai 13. In FIG. 3, reference numerals of the respective devices correspond to those in FIG. 2 , and 16 denotes a center port connection end fixing portion. By fixing the center port of the multi-tube burner, it is possible to prevent the position of the center port from being deformed by the weight of the tube connected to the burner. Therefore, a porous base material can be manufactured stably. In the case of a multi-tube burner, the pipe that forms the center port is the thinnest, so that the influence of deflection due to the tube is particularly likely to occur. Further, the tube may be fixed so that the weight of the tube is not applied to the burner .
[0012]
In the method (4), the optical fiber preform is manufactured using the apparatus (1) in particular. During operation, the weight of the tube does not act on the burner, and the deflection of the burner is prevented. Therefore, the optical fiber preform can be manufactured while keeping the flame formed by the burner stable.
[0013]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and reference examples .
( Reference Example 1) As shown in FIG. 1, a glass-made core burner 2 and a clad burner 3 are arranged. As shown in FIG. 6, the core burner 2 has a concentric multiple tube whose outer diameter of the center port is 7 mm. Using a burner, source gas consisting of silicon tetrachloride, hydrogen and germanium tetrachloride at the center port, hydrogen gas at the second port, argon gas at the third port, oxygen gas at the fourth port, and oxygen gas at the fifth port Argon gas, hydrogen gas was supplied to the sixth port, argon gas was supplied to the seventh port, and oxygen gas was supplied to the eighth port. The clad burner 3 was supplied with silicon tetrachloride and hydrogen gas at the center port, and with the same gas as the core burner after the second port. The clad burner and core burner were fixed to the synthesis facility, and after fixing the burner, a Teflon tube was attached to the gas supply port of the burner. Next, the other end of the Teflon tube was connected to a gas and raw material supply device. Eight tubes were connected to each of the core burner and the clad burner, and the tube was fixed to an optical fiber preform synthesizing apparatus as shown in FIG. 1 so that the weight of the tube did not act on the burner. Then, the optical fiber preform was synthesized. As a result, the axial growth rate of the porous preform is stable at 60 mm / hour ± 2 mm / hour, and the relative refractive index difference variation of the obtained optical fiber preform is stable at 0.35 ± 0.005%. Was. The results are shown in the time-growth rate graph of FIG.
[0014]
Reference Example 2 The same burner as in Reference Example 1 was fixed to a burner fixing base 13 having a function of fixing a tube for supplying raw materials and gas to the burner as shown in FIG. The burner fixing stand 13 has a tube fixing portion 15 for fixing the burner fixing portion 14 and the tubing for fixing the burner body portion. Further, the burner fixing base 13 is fixed to the floor via a stage for adjusting the position of the burner, and the stage is translated in three directions of X, Y, Z, soot body rotation axis and burner base central axis. A rotation axis for adjusting the angle of the rotation. In this configuration, the base material was synthesized without using the fixing portion of the tube, and the optical fiber base material was manufactured. In order to adjust the conditions, XYZ and the burner angle were adjusted. At this time, even if the burner position was returned to the original position, there was a problem that the conditions were not reproduced. Observation of the flame condition of the burner or the flow of glass particles synthesized in the flame revealed that the direction of flow changed when the burner was moved. Moreover, the state of this flow did not return to the original state even if the burner was restored. Further, it was found that the direction of the flow of the glass fine particles easily changes when the position of the glass source gas tube is moved. From this, it was confirmed that when the burner was moved, the pipe constituting the multi-tube burner was moving while being pulled by the connected tube. Next, the connecting portion of the tube was fixed as shown in FIG. 2, and the optical fiber preform was manufactured. At this time, the reproducibility of the burner position is good, and with 10 base materials manufactured under certain conditions, the growth rate is stable at 60 mm / hour ± 2 mm / hour, and the core and cladding evaluated after being made transparent It was confirmed that the relative refractive index difference was stable at 0.35% ± 0.005% over the entire length.
[0015]
The same burner (Example 1) above Reference Example 1, such as shown in FIG. 3, and fixed to the burner fixing base 13 having a function of fixing the connecting end of the central port of the burner. The burner fixing base 13 has a function of fixing the connection end of the center port of the burner to the center port fixing portion 16 in addition to the burner fixing portion 14 for fixing the burner main body. Further, the burner fixing base 13 was fixed to the floor through a stage for adjusting the position of the burner as in the second embodiment. With the above configuration, an optical fiber preform was manufactured. With 10 base materials manufactured under certain conditions, the growth rate is stable at 60 mm / hour ± 2.5 mm / hour, and the relative refractive index difference between the core and the clad evaluated after being transparent is over the entire length. Thus, it was confirmed to be stable at 0.35% ± 0.006%. Although the variation slightly increased compared to the case where the tube was completely fixed, it was found that the stability was greatly improved compared to the case where the tube was not fixed.
[0016]
(Comparative example)
In the same burner arrangement configuration as in Example 1, the tube connecting the burner gas raw material introduction port and the raw material supply unit is not fixed except for the connection ports at both ends. Then, the optical fiber preform was synthesized. As a result, the growth rate in the axial direction of the porous preform is not stable at 60 mm / hour ± 10 mm / hour, and the relative refractive index difference variation of the obtained optical fiber preform is 0.35 ± 0.02%. It was unstable. The results are shown in the time-growth rate graph of FIG.
[0017]
【The invention's effect】
According to the present invention, since the tube connecting the burner, the gas, and the raw material supply device is fixed, the weight of the tube does not act on the burner, and the burner is prevented from being bent. Therefore, the direction of the flame and the raw material flow formed by the burner is stabilized, and a stable optical fiber preform can be manufactured.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a state in which a tube for connecting a cladding burner and a core burner to a gas and raw material supply device is fixed.
FIG. 2 is a conceptual diagram showing a state in which a tube connecting a clad burner and a core burner and a gas and raw material supply device is fixed to a movable burner base having a U-shaped cross section.
FIG. 3 is a conceptual diagram showing a state in which a tube connecting a clad burner and a core burner and a gas and raw material supply device is fixed to a movable burner base.
FIG. 4 is a graph showing the stability of the growth rate in the axial direction of a porous base material in an example of the present invention.
FIG. 5 is a graph showing an axial growth rate of a porous base material in a comparative example.
FIGS. 6A, 6B, and 6C are schematic cross-sectional views showing specific examples of burners that can be used in the present invention.
[Explanation of symbols]
1: Gas and raw material supply device 2: Core burner 3: Clad burner 4: Rotating motor 5: Ball screw 6: Pulling motor 7: Laser projector 8: Light receiver 9: Control device 10: Core burner tube fixing part 11: Clad tube Fixed part 12: tube
13: Burner fixing base
14: Burner fixing part
15: Tube fixing part
16: Center port fixing part

Claims (4)

Comprising a burner preform synthesis optical fiber, the burner fixing base for fixing the burner body, a supply device for supplying glass raw material gas to the burner, and a tube that connects the burner and the feeding device in the optical fiber manufacturing apparatus, the burner comprises a central port for flowing at least a glass raw material, and the combustible gas discharge port or supporting gas injection ports, the combustible gas discharge port or supporting gas injection port to the center port A multi-tube burner arranged concentrically so as to surround the optical fiber preform , wherein the end of the central port on the side connected to the glass raw material supply tube is fixed. manufacturing device. Apparatus for manufacturing an optical fiber preform according to claim 1, characterized in that at least one position more than the fixed connection vicinity of the burner of the tube. 3. The optical fiber preform according to claim 1, wherein a connection end portion of the center port on the side connected to the glass raw material supply tube or the tube is fixed to the burner fixing base. apparatus. A glass raw material is supplied to a burner, oxidized or hydrolyzed in a flame formed by the burner to generate glass fine particles, and the glass fine particles are deposited on the leading edge or outer periphery of a rotating starting material. In the method for producing a material, the burner includes at least a central port through which a glass raw material flows, and a combustible gas ejection port or an auxiliary combustible gas ejection port, wherein the combustible gas ejection port or the auxiliary combustion gas ejection port is the central port. A multi-tube burner arranged concentrically so as to surround the burner, a burner fixing base for fixing the burner body, a supply device for supplying glass raw material and gas to the burner, a burner and the supply device and a tube connecting the fixed and while the optical fiber ends of said central port side to be connected to the supply tube of a glass material Method of manufacturing an optical fiber preform, which comprises combining a base material.

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