JPH08325029A - Method for manufacturing porous glass preform for optical fiber - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] Porous glass matrix for optical fiber that efficiently deposits glass particles generated by flame hydrolysis of raw material gas on the starting core member by an external attachment method at high speed. A method for manufacturing a material is provided. According to the method for producing a porous glass preform for optical fibers according to the present invention, a raw material gas is introduced into an oxyhydrogen flame burner around the outer periphery of a starting core member made of a glass rod, and glass particles are generated by flame hydrolysis. In the method for producing a porous glass preform for optical fibers to be deposited, a plurality of burners equipped with a mechanism that reciprocates in the longitudinal direction of the starting core member are moved in the radial direction as the diameter of the deposited object increases. It is characterized in that it is made to be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous glass preform for an optical fiber, and more particularly to a porous glass for an optical fiber which is efficiently and rapidly deposited by a method of externally attaching glass particles to a starting core member. The present invention relates to a method for manufacturing a base material.

[0002]

2. Description of the Related Art As shown in FIG. 8, a porous glass preform for optical fibers is conventionally provided with a plurality of oxyhydrogen flame burners 22, 23, 24 on the outer periphery of a starting core member 21 such as a quartz glass rod. The core members are arranged in a row parallel to the longitudinal direction, and a raw material gas such as silicon tetrachloride is supplied to this burner, and glass fine particles generated by flame hydrolysis of the raw material gases are used as the starting core member.
The porous glass base material 26 is manufactured by depositing it on 21 as shown in FIG. 9, but in this case, the amount of raw material gas supplied to the burner is small at the initial stage when the diameter of the starting core member 21 is small. Therefore, the amount is small, and since it increases with an increase in the diameter of the porous glass base material 26 deposited here,
The range 25 of the flame of this burner also gradually increases as shown in FIGS. 8 to 9, but these burners 22, 23, 24
Is performed by moving the porous glass base material 26 to an appropriate position as the diameter of the porous glass base material 26 increases, as shown in FIG.

[0003]

However, in this case, if the number of oxyhydrogen flame burners is increased to increase the number of burners in order to increase the production amount of the porous glass preform, the maximum gas amount is reached. When this happens, the efficiency will decrease due to the interference of flames.Therefore, it is necessary to set the burner interval to an appropriate range so that silica fine powder can be generated efficiently. There is a possibility that defective portions on both ends of the porous glass base material that are generated may increase.

It is also considered to use a large-diameter burner in which the diameter of these oxyhydrogen flame burners is increased, but this one uses the source gas such as oxygen and hydrogen supplied to this burner. This burner requires a large amount, and the efficiency at the initial stage of deposition is extremely low. When the gas flow rate is low, the linear velocity of the flame becomes small and the flame is disturbed, and the efficiency of adhering fine glass particles deteriorates. With respect to, it has been proposed that the burner has a special structure (JP-A-4-
However, there is a problem in that the structure is complicated and it is difficult to produce the same performance, and it is difficult to adjust the gas amount of each injection nozzle.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a porous glass preform for an optical fiber which solves the above disadvantages and problems, and it relates to the outer periphery of a starting core member made of a glass rod. In a method for producing a porous glass preform for optical fibers in which a raw material is introduced into an oxyhydrogen flame burner and glass particles are generated and deposited by flame hydrolysis, a plurality of mechanisms that reciprocate in the longitudinal direction of the starting core member are attached. The burner is moved in the radial direction as the diameter of the deposited body increases.

That is, the inventors of the present invention have conducted various studies on methods for solving the disadvantages and drawbacks of the conventional method for producing a porous glass preform for optical fibers, and as a result, deposit glass fine particles generated by this oxyhydrogen flame burner. At this time, since the diameter of the starting core member is small and the amount of the raw material gas is small at the initial stage of the deposition, flame interference between the gas burners is unlikely to occur, and therefore, even if the burner interval is small, no problem occurs. However, the deposition of glass particles increases the diameter of the porous glass base material, and when the raw material gas increases, the flame efficiency of multiple burners interferes with the deposition efficiency of the glass particles, resulting in increased defects at both ends of the porous glass base material. However, when the diameter of the porous glass base material increases, if the burner position is moved in the radial direction of the porous glass base material as the diameter increases, the raw material gas increases. Also found that the flame interference between the burners is less likely to occur, so that the deposition efficiency of the glass fine particles will not deteriorate, and in this case, the burner used here is the same as that conventionally used. The present invention was confirmed by confirming that the raw material gas can be easily controlled because it can be used, and that the defective portions at both ends of the porous glass base material will not increase. It was made. This will be described in more detail below.

[0007]

The present invention relates to a method for producing a porous glass preform for optical fibers, which is glass fine particles generated from an oxyhydrogen flame burner in which a raw material gas is introduced into a starting core member made of a glass rod as described above. And the burner is moved in the radial direction when the diameter of the porous glass preform produced by the deposition of the glass fine particles increases.

For example, the arrangement state of the oxyhydrogen flame burner at the initial stage of deposition for depositing glass fine particles on the starting core member is as shown in FIG. Oxyhydrogen flame burner 2,
The burners 2, 3, 4, 5, 6 are arranged in a line parallel to the longitudinal direction of the starting core member 1.
As shown in FIG. 2, the flame is directed to the starting core member 1, and the glass particles generated there are deposited on the starting core member 1. At this time, the burners 2, 3 are used. The amount of gas supplied to 4, 5, 6 is small,
Since the diameter of the starting core member 1 is small, the adhesion efficiency of the glass particles to the starting core member 1 is good, the spread 8 of the flame is small, and therefore the interference of the flames between the burners 2, 3, 4, 5, 6 is small.

When the diameter of the porous glass base material 11 obtained by this deposition increases as the deposition of the glass fine particles progresses, the burners 2, 3, 4, 5, 6 are, for example, as shown in FIGS. The burners 2, 4 and 6 and the burners 3 and 5 are moved in the radial direction of the starting core member 1 and arranged in two rows, whereby the flame between the burners is prevented from interfering with each other, and the deposition efficiency of the glass particles is improved. Is less likely to decrease.

The method of moving the burners 2, 4, 6 and the burners 3, 5 in the present invention in the radial direction of the porous glass preform may be performed, for example, by the method shown in FIG. That is, this is an apparatus equipped with burners 2, 4, 6 and burners 3, 5 and an exhaust hood 13 as shown in FIG. 5, and is arranged in a row in this apparatus as shown in FIGS. Porous glass base material 11 produced by depositing glass particles generated in burners 2, 4, 6 and burners 3, 5.
The weight of the load cell 15 and the arithmetic unit (CPU) 16
The diameter of the porous glass preform 11 is calculated by the following equation, and when the diameter reaches a predetermined value, the burner drive unit 14 gives the optimum burner interval for the diameter of the porous glass preform 11 as shown in FIGS. The burners 2, 4, 6 and the burners 3, 5 are moved in the radial direction of the porous glass preform 11 in the arrangement shown, and the raw material gas amount at this time is controlled to the optimum amount calculated by the arithmetic unit 16. Good.

According to this, the gas supply device 19 supplies the optimum amount of gas in which the flame interference is small and the adhesion efficiency of the glass particles is high, and these operations are automatically performed until the deposition of the glass particles is completed. Since the process is continued, it is possible to obtain the desired porous glass preform for optical fibers easily and with high deposition efficiency, and there is an advantage that the effective component ratio of the porous glass preform is also improved.

[0012]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Example As shown in FIGS. 5 and 6, the outer diameter was set in a closed reactor 20.
A driving unit 18 for rotating a quartz glass rod as a starting core member 1 having a length of 23 mm and a length of 1,050 mm and an oxyhydrogen flame burner 2, 3, 4, 5, 6 reciprocating by the driving unit 17 are provided.
A porous glass preform for optical fibers was manufactured using an apparatus for manufacturing a porous glass preform for optical fibers, which was provided with an exhaust hood 13 for exhausting exhaust gas generated from an oxyhydrogen flame burner.

In this case, the burners 2, 4, 6 and 3, 5 are simultaneously fixed so as to move in the radial direction of the starting core member, and each burner has an outer diameter of a quintuple pipe structure of 45 mm.
φ, but these are arranged in a line in the same direction as the starting core member 1 as shown in FIGS. 1 and 2, and the burner center axis intervals of the burners 2, 4, 6 and the burners 3, 5 are arranged. Is 15
It was set to 0 mm. This starting core member 1 is driven by the drive unit 40 to 40 rp.
While rotating at m, this oxyhydrogen flame burner 2,
Nos. 4, 6 and burners 3, 5 are 50 liters / min of oxygen gas, 100 liters / min of hydrogen gas, 6 liters / min of oxygen gas as a carry gas and 25 g / min of silicon tetrachloride from the raw material supply device shown in FIG. The burner was reciprocated by the driving unit 17 at a speed of 150 mm / min in the range of 1,600 mm, and the glass fine particles generated by the burner were deposited on the starting core member 1.

Due to the deposition of glass particles on the starting core member 1, a porous glass preform is formed on the starting core member 1.
11 is made, and when the diameter of this porous glass member is increased, its weight is measured by the weight detector 15 shown in FIG. 5, the outer diameter is calculated by the arithmetic unit 16, and the burner drive unit is based on this. The oxyhydrogen flame burners 2, 4 and 6 and the burners 3 and 5 are respectively moved by 14 in the radial direction of the porous glass base material, and the amount of this gas is also increased while controlling it so that the flame does not interfere with the porous glass. Continued production of base metal.

The amount of raw material gas supplied from the raw material supply device 19 immediately before the end of the deposition is 125 liters of oxygen gas /
Min., Hydrogen gas 250 liters / min, oxygen gas 12 liters / min as carrier gas, and silicon tetrachloride 60 g / min. Porous glass of oxyhydrogen flame burners 2, 4, 6 and burners 3, 5. The movement from the origin in the radial direction to the base metal was 40 mm vertically, and the vertical interval of the burner center axis was 80 cm.However, after continuing this reaction for 36 hours, the outer diameter of 200 mmφ Quality glass base material is obtained,
The effective component of this product was 79%, and the results shown in FIG. 7 were obtained for the deposition time and the deposition weight.

Comparative Example 1 The same apparatus for producing a porous glass preform for an optical fiber as in Example 1 was used, but in this case, the oxyhydrogen flame burners were arranged as shown in FIG. Are arranged in a line parallel to the longitudinal direction of the starting core member 21 with a center axis interval of the burners of 150 mm, and 60 liters of oxygen gas /
Of hydrogen gas, 120 liters / minute of hydrogen gas, 8 liters / minute of oxygen gas as a carrier gas, and 30 g / minute of silicon tetrachloride are introduced, and glass fine particles generated by flame hydrolysis of these gases are introduced onto the starting core member 21. Deposited.

The position of the burners 22, 23, 24 immediately before the end of the deposition and the range 25 of the flame hitting the surface of the porous glass base material 26 are shown in FIG.
However, in this case, when the amount of raw material gas was increased in order to increase the deposition rate of the glass particles, flame interference occurred, and as a result, the flame was disturbed and the deposition rate decreased. Since the amount of gas was controlled so that flame interference did not occur, a porous glass base material with an outer diameter of 200 mmφ was obtained after 52 hours, but the deposition time and weight of this product are shown in Fig. 7. The result was as shown.

Comparative Example 2 The same apparatus for producing a porous glass preform for optical fibers as in Example was used, and the oxyhydrogen flame burners used here were arranged in a line parallel to the longitudinal direction of the starting core member 21 and the burner was used. The distance between the central axes was 150 mm, which was the same as in Comparative Example 1, but this number was set to 5, and glass particles were deposited under the same conditions as in Comparative Example 1, and the amount of raw material gas was controlled to prevent flame interference. As a result, the deposition rate was slightly improved, and after 47 hours, a porous glass base material with an outer diameter of 200 mm was obtained. Regarding the deposition time and the deposition weight of this, the results shown in Fig. 7 were obtained. 5, the defective deposition parts 12 at both ends of the porous glass base material shown in FIG. 5 increased, and the effective component of the obtained porous glass base material decreased to 68%.

[0019]

The present invention relates to a method for producing a porous glass preform for optical fibers, according to which the diameter of the porous glass preform increases due to the deposition of glass particles.
Even if the amount of raw material gas increases, flame interference is less likely to occur, so
The deposition efficiency of fine glass particles does not deteriorate,
In this case, the burner used here can be the same as that used conventionally, so that the control of the raw material gas is easy, and the defective deposition parts at both ends of the porous glass base material are reduced, and The advantage that the porous glass preform for fibers can be manufactured easily and efficiently is provided.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an arrangement state of oxyhydrogen flame burners at the initial stage of glass particle deposition in an apparatus for producing a porous glass preform for optical fibers used in the present invention.

FIG. 2 is a side view of the oxyhydrogen flame burner arrangement shown in FIG. 1 taken in the direction A.

FIG. 3 is a vertical cross-sectional view showing an arrangement state of oxyhydrogen flame burners during deposition of glass particles in the apparatus for producing a porous glass preform for optical fibers used in the present invention.

FIG. 4 is a side view of the oxyhydrogen flame burner arrangement state shown in FIG. 3 as seen from the direction B.

FIG. 5 is a side sectional view of an optical fiber porous glass preform manufacturing apparatus used in the present invention.

FIG. 6 is a layout view of equipment in the optical glass porous glass preform manufacturing apparatus shown in FIG.

FIG. 7 is a diagram showing the relationship between the deposition time and the deposition weight of the porous glass preforms for optical fibers obtained in Examples of the present invention and Comparative Examples 1 and 2.

FIG. 8 is a vertical cross-sectional view of an arrangement state of oxyhydrogen flame burners at the early stage of glass particle deposition in a conventional apparatus for producing a porous glass preform for optical fibers.

FIG. 9 is a vertical cross-sectional view showing an array state of oxyhydrogen flame burners during deposition of glass particles in a conventional apparatus for producing a porous glass preform for optical fibers.

FIG. 10 is a side view of the oxyhydrogen flame burner arrangement shown in FIG. 9 taken in the direction C.

[Explanation of symbols]

 1,21 ... Starting core member 2,3,4,5,6,22,23,24 ... oxyhydrogen flame burner 8,9,25 ... flame range 11,26 ... porous glass base material 12 ... poor glass particles Accumulation part 13 ... Exhaust hood 14 ... Burner drive part 15 ... Weight detector 16 ... Calculation unit (CPU) 17 ... Burner stand reciprocating drive part 18 ... Starting core member rotation drive part 19 ... Raw material supply device 20 ... Closed reactor

Claims (1)

[Claims] 1. A method for producing a porous glass preform for optical fibers, in which a raw material gas is introduced into an oxyhydrogen flame burner around the outer periphery of a starting core member made of a glass rod, and the glass particles are generated and deposited by flame hydrolysis. In the above method, a plurality of burners having a mechanism for reciprocating in the longitudinal direction of the starting core member are moved in the radial direction as the diameter of the deposition object increases, Of manufacturing high quality glass base material.