JP2003040624A - Method and apparatus for producing glass base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a glass base material able to reduce weight fluctuation of heaped fine glass particle to a longitudinal direction of a sooting layer and able to produce a clear glass base material having a uniform outside diameter to the longitudinal direction or a constant diameter ratio of a core to a clad and its producing apparatus. SOLUTION: The glass base material is produced by forming a sooting layer 3 heaped with fine glass particles produced by a burner 6 on the periphery of a starting glass rod 1 traversing the stating glass rod 1 to a longitudinal direction while rotating. The temperature distribution and the outside diameter distribution of a face heaped with fine glass particles are measured and the weight distribution of a newly heaped sooting layer is calculated at each traverse or each specific traverse. The heaped fine glass particle weight is adjusted at the following traverse that the weight fluctuation is to be less calculated by the above weight distribution or the weight distribution calculated in the past.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a glass base material in which glass particles are deposited on a glass rod as a starting base material.

[0002]

2. Description of the Related Art In the production of a cylindrical glass base material, a glass rod is used as a starting base material and glass fine particles are deposited on the outer periphery of the glass rod while rotating to form a soot preform (external vapor deposition). Method: OVD method) is known. This method, for example, on a glass rod of the starting base material, a glass raw material gas such as SiCl ₄ in a reaction vessel, blown from the burner with auxiliary natural gas such as fuel gas and O _2, such as H _2, the flame-hydrolysis Glass particles are generated by the decomposition reaction and deposited to form a soot layer of porous glass. The soot preform manufactured as described above is then dehydrated and sintered to obtain transparent glass having a predetermined outer diameter.

In order to obtain a transparent glass having a predetermined outer diameter, it is necessary to form a soot preform in which a predetermined amount of glass fine particles are deposited. Usually, in order to obtain a soot preform with a predetermined outer diameter, a method in which the glass rod of the starting base material is traversed in the longitudinal direction relative to the burner many times while rotating in the reaction vessel, and the deposition of the glass fine particle layer is repeated. It has been known. Then, the detection and control of the deposition amount of the glass fine particles are performed by monitoring the outer diameter or the weight of the soot layer.

For example, a method is known in which the weight increase of the soot layer is measured for each traverse and the final traverse speed is controlled to obtain a desired deposition amount (see Japanese Patent Application Laid-Open No. 4-260633). This method can adjust the final weight of the soot layer to a predetermined value, but it is not known whether the weight is uniformly deposited in the effective area in the longitudinal direction. For example,
When glass particles are deposited using a burner, it is unknown at what position in the longitudinal direction how many grams of glass particles were deposited, and the amount of glass particles deposited on the ineffective parts at both ends changes. Then, the amount of glass particles deposited on the effective portion cannot be accurately specified.
This is because it is not possible to obtain information on the variation in the length direction during the deposition of the glass particles.

In the manufacture of glass preforms for optical fibers,
The core / clad ratio in the longitudinal direction of the starting glass rod is measured in advance, the traverse speed and the glass raw material gas supply amount are controlled in accordance with the change in the core / clad ratio in the longitudinal direction, and the deposition amount of the glass particles in the longitudinal direction is controlled. A method of adjusting is known (see Japanese Patent Laid-Open No. 4-292434).
This method is based on a pre-measured core of the starting glass rod /
It is premised that the burner speed and the glass source gas supply are controlled based on the clad ratio distribution. Therefore, it is possible to manufacture an optical fiber preform having a constant core / cladding ratio if the control of the burner speed and the glass raw material gas supply does not fluctuate and is performed exactly as a predetermined value. However, in general, the exhaust pressure of the reaction vessel, the flow rate of oxyhydrogen gas from the burner, the flow rate of the glass raw material gas, and the like change with time, and in addition, there are changes due to the structural difference of the burner.
Therefore, the deposition amount of the glass particles constantly fluctuates in the longitudinal direction of the glass rod and cannot be dealt with by preset control and adjustment.

Further, during the deposition of the glass particles, the temperature of the deposition surface of the glass particles in the longitudinal direction and the outer diameter of the soot layer are measured with time, the supply amount of oxyhydrogen gas is adjusted, and the soot density (bulk density) is made uniform. There is known a method of making the soot diameter uniform or making the soot outer diameter uniform (see JP-A-2000-256034). However, this method controls only the supply amount of oxyhydrogen gas and adjusts the deposition surface temperature of the glass particles or the soot outer diameter, but the glass source gas supply amount and the traverse speed are taken into consideration. Absent. Therefore, it is difficult to uniformly deposit the glass particles in the longitudinal direction and obtain a predetermined deposition weight.

If the deposition weight of the glass particles is not uniform in the longitudinal direction of the soot layer, the outer diameter in the longitudinal direction of the transparent glass preform becomes nonuniform when it is made into transparent vitrification by dehydration / sintering. Alternatively, the ratio between the diameter of the starting glass rod and the outer diameter of the glass base material becomes non-uniform. In the case of melting and drawing this into a glass optical fiber, the ratio of the core and the clad diameter fluctuates, which impairs the optical transmission characteristics. Further, when a transparent glass base material is sliced into a plate shape as a photomask or glass for liquid crystal, the outer diameter dimension becomes nonuniform.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and reduces fluctuations in the deposition weight of glass fine particles in the longitudinal direction of the soot layer to provide a uniform outer diameter or core in the longitudinal direction. An object of the present invention is to provide a glass base material manufacturing method and a manufacturing apparatus therefor capable of obtaining a transparent glass base material having a constant ratio of the clad diameter and the clad diameter.

[0009]

The method for producing a glass preform according to the present invention comprises traversing the starting glass rod in the longitudinal direction while rotating the glass rod, and depositing glass fine particles generated by a burner on the outer periphery of the starting glass rod. A method of manufacturing a glass base material to form a layer, measuring the temperature variation distribution and outer diameter variation distribution of the glass particles, for each traverse or for each predetermined traverse, the weight distribution of the newly deposited soot layer It is characterized in that the deposition amount of glass fine particles is adjusted after the next traverse so that the fluctuation of the weight distribution calculated and the weight distribution obtained by adding the previously calculated weight distribution is reduced.

Further, the glass base material manufacturing apparatus of the present invention comprises:
A reaction vessel, a drive device for traversing the starting glass rod in a longitudinal direction while rotating, a manufacturing device of a glass base material provided with a burner for generating glass particles to be deposited on the outer periphery of the starting glass rod, and a longitudinal direction of a soot layer. It is equipped with a soot position measuring device for measuring the position, a radiation thermometer for measuring the temperature of the deposition surface of glass particles, and a laser distance measuring device for measuring the outer diameter of the soot layer. It is characterized by being provided with an arithmetic unit for calculating the weight distribution of the soot layer deposited from the diameter.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is to make the deposition weight of glass fine particles deposited on the glass rod of the starting base material uniform in the longitudinal direction with high accuracy. That is, if the deposition weight of the glass particles is uniform in the longitudinal direction, the outer diameter in the longitudinal direction of the soot layer formed by the deposition of the glass particles may vary, and the soot density (bulk density) also varies. It can be said that there is. If the soot preform, in which the deposited weight of glass particles is formed uniformly in the longitudinal direction, is made into transparent glass by dehydration / sintering treatment, if the starting glass rod has a uniform outer diameter, the outer diameter fluctuates in the longitudinal direction. And a glass base material having a uniform ratio to the diameter of the starting glass rod is obtained.

The deposition weight of the glass particles in the longitudinal direction can be calculated from the outer diameter of the soot layer and the bulk density at the longitudinal position of the soot layer. The outer diameter of the soot layer can be calculated by measuring the distance to the surface of the soot layer with a distance measuring device, and the bulk density has a certain relationship with the temperature of the glass particle deposition surface. The temperature can be measured using a radiation thermometer or the like, and can be calculated from the deposition surface temperature of the glass particles. The deposition weight of the glass particles can be easily calculated by the product of the increased volume and the bulk density obtained from the outer diameter of the soot layer. By performing these measurements at each position in the longitudinal direction of the soot layer, the weight distribution in the longitudinal direction of the soot layer due to the deposition of glass particles can be calculated.

The weight distribution in the longitudinal direction of the soot layer is calculated for each traverse or at a predetermined traverse. Based on the calculated weight distribution, it is fed back to the next traverse to adjust the supply amount of glass raw material gas or the traverse speed to adjust the deposition amount of the glass fine particles to reduce the fluctuation of the weight distribution. By repeating this measurement and adjustment, finally, the deposition weight of the glass fine particles at the longitudinal position of the soot layer becomes uniform or has a predetermined distribution in the longitudinal direction. It is possible to obtain a cylindrical glass preform having a constant ratio of diameter to starting glass rod diameter.

An embodiment of the present invention will be described with reference to the schematic view of FIG. In the figure, 1 is a starting glass rod, 2 is a dummy rod, 3 is a soot layer, 4 is a reaction vessel, 5 is a driving device,
6 is a burner, 7 is a vertically long observation window, 8 is a temperature measuring device, 9 is a small observation window, 10 is a distance measuring device, 11 is a soot position measuring device, 12 is a gas supply device, 13 is a computing device, and 14 is a control device. Indicates.

In the case of an optical fiber, the starting glass rod 1 is a core glass having a refractive index increased by adding a dopant, or a columnar glass rod having a clad glass outside the core glass. Further, in the production of the glass base material other than the optical fiber, glass formed of the same material as the deposited glass particles is used. Starting glass rod 1
The starting glass rod 1 is supported by the supporting portion of the reaction container 4 at the end where the soot layer 3 is not formed, and
The dummy rod 2 for the processing after forming the soot layer is attached by fusion. The starting glass rod 1 may be a long one without using the dummy rod 2.

The reaction container 4 has, for example, a vertical structure, and a driving device 5 for suspending and supporting the starting glass rod 1 and vertically moving the starting glass rod 1 is arranged in the upper part. One or more burners 6 are arranged in the reaction vessel 4, and the soot layer 3 is generated by depositing glass fine particles on the outer circumference of the starting glass rod 1 by the flame gas and the glass raw material gas supplied from the burner 6. . A predetermined flame gas and a glass material gas are adjustably supplied to the burner 6 by the gas supply device 12. If the reaction vessel is of horizontal type,
The starting glass rod 1 is supported on both sides to traverse in the horizontal direction.

A vertically long observation window 7 is provided on the vessel wall of the reaction vessel 4 to observe the surface of the soot layer on which the glass particles are deposited,
Further, the temperature measuring device 8 is used to
It is configured so that the distance to the outer surface of the soot layer can be measured by the distance measuring device 10 or the like. In addition, for the distance measuring device 10,
Instead of the vertically long observation window 7, circular or rectangular observation small windows 9 may be provided below and above the burner 6. Information on the driving device 5 that rotates and traverses the starting glass rod 1 can be input to the soot position measuring device 11 to measure the position of the soot layer 3 in the longitudinal direction.

The information on the deposition surface temperature of the glass particles measured by the temperature measuring device 8, the distance information to the outer surface of the soot layer measured by the distance measuring device 10, and the position information by the soot position measuring device 11 are stored in the computing device 13. Is entered.
The arithmetic unit 13 performs arithmetic processing based on various input information to calculate the weight distribution in the longitudinal direction of the soot layer 3. The control device 14 adjusts the supply amount of glass raw material gas, the traverse speed, or the like based on the weight distribution calculated by the calculation device 13 to perform feedback control to the next traverse to adjust the deposition amount of the glass particles. To reduce the variation in weight distribution.

As the temperature measuring device 8 for measuring the temperature of the glass particle deposition surface, it is preferable to use a radiation thermometer for measuring the radiation intensity emitted from the glass particle deposition surface through the vertically long observation window 7. For this radiation thermometer, since a radiation thermometer that measures with a spot has a large measurement error, it is preferable to use a thermoviewer capable of measuring a wide range. Further, the temperature measuring device 8 preferably measures the surface temperature of the soot layer 3 at the highest temperature, for example, the temperature of the position where the burner 6 is applied. The deposition surface temperature of the rotating glass particles is continuously measured when passing through the temperature measuring device 8, and the average value of the surface temperature at each position is obtained to calculate the temperature distribution in the soot longitudinal direction. From this temperature distribution, the bulk density ρ (g / c at each position in the soot longitudinal direction)
m ³ ) is calculated by a relational expression based on the accumulated data.

As the distance measuring device 10 for measuring the distance to the surface of the soot layer 3, it is preferable to use a laser type distance measuring device which can measure from a long distance without contact. Since the temperature around the reaction container 4 becomes relatively high, it is preferable to use a long-distance measurement type (measurement distance 1 to 2 m) and install it as far as possible from the reaction container in order to avoid failure due to high temperature. . Further, when the observation small window 9 is provided for distance measurement, it is preferable that the observation light window 9 is installed so that the laser beam is positioned at least 5 cm below the burner 6. If the laser light is too close to the burner 6, it may be disturbed by the glass particles floating in the reaction vessel without being deposited, and accurate measurement may not be possible. The distance measuring device 10 may be installed on the upper side of the burner 6 or on both the lower side and the upper side of the burner 6.

FIG. 2 is a diagram for explaining a method of calculating the outer diameter of the soot layer. The outer diameter (R) in the longitudinal direction of the starting glass rod 1 and the distribution of changes in the outer diameter are measured in advance. Further, a part of the starting glass rod 1 is made of frosted glass so that the laser light does not pass therethrough, and the outer diameter of this part is measured in advance. When the dummy rods 2 are welded to both ends of the starting glass rod 1, the dummy rods may be ground glass. The starting glass rod 1 is suspended in the reaction container 4, and laser light is applied to the frosted glass portion to measure the distance (L ₀ ) from the distance measuring device 10 to the surface of the starting glass rod 1. At this time, it is necessary that the laser light is applied perpendicularly to the starting glass rod 1 and toward the center.

Next, the starting glass rod 1 is traversed from the upper side to the lower side while rotating, and flame gas and glass raw material gas are blown from the burner 6 to the surface thereof. Glass particles of the first layer are deposited by this first traverse (first traverse), and the distance (L ₁ ) from the distance measuring device 10 to the surface of the deposition layer of the glass particles (soot layer 3) is set in each of the longitudinal directions. Measure at position. From this measured value, the outer diameter (D ₁ ) of the soot layer after the first traverse is determined at each position in the longitudinal direction, and the outer diameter distribution in the longitudinal direction is calculated. From the outer diameter (D ₁ ) of the soot layer and the outer diameter (R) of the starting glass rod, the radial cross section of the soot layer 3 can be calculated, and the unit length (c
m) can be multiplied to calculate the increasing volume (V ₁ ) distribution in the longitudinal direction per unit length.

The next second traverse is a movement from the lower side to the upper side in the opposite direction to the first traverse. Therefore,
When the distance measuring device 10 is installed only below the burner 6, there is no change in the outer diameter of the soot layer in the second traverse, and therefore the distance measurement need not be performed. However, in order to avoid a measurement error, the distance may be measured in both the first traverse and the second traverse, and the average value thereof may be taken. When the distance measuring device 10 is installed on both the lower side and the upper side of the burner 6, the distance to the deposition layer of the second layer of glass particles by the second traverse is measured on the upper side. It can be measured by the instrument.
The glass particle deposition surface temperature measurement and the bulk density distribution calculation are performed for each traverse regardless of whether or not the outer diameter is measured.

In the third traverse, by moving from the upper side to the lower side in the same direction as the first traverse, the glass particles of the third layer are deposited as in the first traverse. The distance (L ₃ ) from the distance measuring device 10 to the surface of the soot layer 3 during the third traverse is measured at each position in the longitudinal direction. Distance (L ₁ ) measured during the first or second traverse
And the distance (L ₃ ) measured during the third traverse, the third
Calculating soot layer outer diameter after traversing the (D ₃₎ at each position in the longitudinal direction. From this soot layer outer diameter (D ₃ ) and the soot layer outer diameter (D ₁ ) after the first traverse, the radial increasing cross-sectional area of the soot layer 3 at the time of the third traverse can be calculated and multiplied by the unit length (cm). By doing so, the increased volume per unit length (V ₃ ) can be calculated. Similarly, from the fifth traverse to the final traverse, the distance (Ln) from the distance measuring device 10 to the surface of the deposited layer of glass particles is measured, and the soot layer outer diameter (Dn) and the increased volume per unit length are measured. Calculate (Vn).

As described above, the distance (Ln) to the outer surface of the soot layer is measured to calculate the increased volume (Vn) in the longitudinal direction of the glass fine particles deposited on the starting glass rod 1. The product of the increased volume (Vn) and the bulk density ρn (g / cm ³ ) at each position in the soot longitudinal direction, which is obtained from the deposition surface temperature of the glass particles measured at each traverse, is used to determine the length of the glass particles. The weight distribution in the direction can be measured. The weight distribution is measured and calculated over the entire length of the effective range of the soot layer 3. That is, the first
The weight distribution in the longitudinal direction of the layer is obtained and used as the data for depositing the glass particles of the second layer. Then, in the second traverse in which the second layer is deposited, the controller 14 adjusts and controls the supply amount of glass raw material gas or the traverse speed so as to reduce the variation in the weight distribution of the first layer.

Thereafter, until the predetermined soot layer weight is obtained, the above-mentioned measurement, calculation and adjustment control are carried out every traverse or at a predetermined predetermined traverse, so that the soot layer 3 is deposited in an effective range. It can be made uniform over the entire length. By dehydrating and sintering the soot preform thus formed, it is possible to obtain a uniform transparent glass preform with a small outer diameter variation in the longitudinal direction.

In addition, the outer diameter of the starting glass rod may fluctuate in the longitudinal direction. For example, the starting glass rod is a core glass rod for optical fiber, the outer diameter of which varies in the longitudinal direction, or the glass rod is composed of a core portion and a clad portion, and the ratio of “core diameter / clad diameter” is long. It may fluctuate in the direction. In such a case, the starting glass rod outer diameter fluctuation distribution, "core diameter / clad diameter" is calculated in advance.
The distribution of fluctuations in the ratio is previously measured, and the soot layer is deposited according to these fluctuations. Therefore, the deposition weight distribution of the glass particles in the longitudinal direction of the soot layer is adjusted to a deposition weight distribution such that the ratio of “core diameter / glass diameter” becomes uniform, and the deposition weight distribution itself in the longitudinal direction is not always uniform. You don't have to. When this glass particle deposit is made into a transparent glass, it is possible to obtain a glass base material having a ratio of “core diameter / glass diameter” uniform in the longitudinal direction.

The amount of glass particles deposited is adjusted by adjusting the traverse speed at a constant rate and increasing or decreasing the supply amount of the glass raw material gas supplied from the burner 6 at a position in the longitudinal direction. There is a way to change. In the former case, the amount of glass raw material gas is set to MFC.
Adjustment is relatively easy because it is only adjusted with the (mass flow controller). The latter changes the amount of glass particles deposited depending on whether the traverse speed is increased or decreased, so that a fine variable adjustment mechanism of the traverse speed is necessary. It is also possible to control both of them at the same time, but the control becomes complicated. Incidentally, it is desirable to increase or decrease the oxyhydrogen gas in accordance with the adjustment of the traverse speed or the supply amount of the glass raw material.

Next, a specific example of the above-described embodiment will be described. The starting glass rod 1 has a core part and a clad part for an optical fiber, and has a ratio of “core diameter / clad diameter” and an outer diameter of 30 m in which the glass outer diameter is uniform in the longitudinal direction.
A cylindrical glass having a length of m and a length of 500 mm was used. Dummy rods 2 of quartz glass having an outer diameter of 30 mm, the surface of which was ground glass, were welded to both ends of this cylindrical glass. One of the dummy rods 2 is supported by the driving device 5 and is suspended in the reaction container 4. The distance measuring device 10 is of a laser type, and is installed 100 mm below the burner 6 so that the laser light strikes the center of the starting glass rod 1 at a right angle. As the temperature measuring device 8, a thermoviewer capable of measuring a wide range was used and installed so as to be movable in the longitudinal direction.

As the burner 6, one having a diameter of 60 mm was installed. From the burner 6, SiCl ₄ which is a glass raw material
12 SLM (standard liter / minute), H ₂ for flame formation of 240 SLM, O ₂ of 120 SLM, and Ar gas 6 SLM for shielding H ₂ and O ₂ near the burner outlet as standard values. I decided to do it. In this specific example, one burner 6 is installed, but a plurality of burners may be used.

Prior to the start of deposition of glass particles, first, laser light is applied from the distance measuring device 10 to the ground glass surface of the dummy rod 2 to measure the distance (L ₀ ) between the surface of the starting glass rod and the distance measuring device 10. . After that, the first glass traverse 1 is started from the upper side to the lower side while rotating the starting glass rod 1 at a rotation speed of 40 rpm, for example, and the first traverse is started at a speed of 200 mm / min. The traverse range of the starting glass rod 1 was 1100 mm.

The temperature of the deposition surface of the glass particles is measured by the temperature measuring device 8, the average value of the deposition surface temperature at each position is calculated, and the bulk density ρ ₁ (g / cm ³ ) is specified from this surface temperature. , Calculate the bulk density distribution in the longitudinal direction. Further, when traversing from the upper side to the lower side, laser light is applied to the surface of the deposition surface from the distance measuring device 10 to measure the distance (L ₁ ) between the deposition surface and the distance measuring device 10 at each position. With this, the variation distribution in the longitudinal direction of the soot layer outer diameter (D ₁ ) increased due to the deposition of glass particles is calculated. From these bulk density distribution and outer diameter variation distribution, the weight distribution due to the deposition of glass particles in the longitudinal direction of the starting glass rod 1 was calculated.

FIG. 3 is a diagram showing a weight distribution on the starting glass rod 1 after the first traverse. In the figure, the horizontal axis shows the position of the starting glass rod 1 in the longitudinal direction, and the vertical axis shows the weight increase rate at each position, where the average weight increase amount is 1. In this figure, 100 mm from one end and 4
The weight increase is large at the position of 00 mm, and the weight increase is small at the position of 250 mm. The computing device 13 computes each piece of information and the data of the weight distribution obtained in the first traverse, and the computation result is given by the control device 14 to
It is used to adjust the deposition amount of glass particles in the second traverse.

The second traverse moves in the opposite direction to the first traverse, and moves the starting glass rod 1 from the lower side to the upper side. In this case, there was no change in the outer diameter of the soot layer 3 measured below the burner 6, so the measurement was stopped. However, by installing another distance measuring device on the upper side of the burner 6, it is possible to measure the outer diameter change even in this second traverse, and to measure the soot layer outer diameter change for every traverse. You can Since the traverse is performed at least 100 times or more until the outer diameter of the predetermined soot layer is reached, only when the traverse is performed from the upper side to the lower side or from the lower side to the upper side,
The outer diameter may be measured. Furthermore, when the variation in weight increase is small, the number of measurements may be further reduced. It should be noted that it is desirable to measure the deposition surface temperature of the glass particles for each traverse.

FIG. 4 is a diagram showing the distribution of the glass raw material supply amount at each position in the longitudinal direction during the second traverse, which is set based on the weight distribution during the first traverse. In the figure, the horizontal axis shows the longitudinal position of the starting glass rod 1, and the vertical axis shows the ratio of the glass raw material supply amount at each position, where the average glass raw material supply amount is 1. This FIG. 3 is a distribution in which the peaks and valleys of the weight distribution of FIG. 2 are reversed. That is,
The position of 100mm and 400 where the weight increase was large in Fig. 2
At the position of mm, the supply amount of the glass raw material is reduced, and at the position of 250 mm where the weight increase is small in FIG. 2, the supply amount of the glass raw material is increased. In the third traverse, when the new weight distribution is not measured in the second traverse, the glass raw material supply amount is returned to the reference value,
The glass fine particles may be uniformly deposited, but the same adjustment may be performed by dividing the increase / decrease in the supply amount of the glass raw material by 1/2 in the second traverse. The temperature of the glass particulate deposition surface was also measured in the second traverse and used as data for calculating the weight distribution during the third traverse.

FIG. 5 is a diagram showing the weight distribution measured and calculated during the third traverse. Similar to FIG. 3, the horizontal axis represents the longitudinal position of the starting glass rod 1, and the vertical axis represents the weight increase rate at each position, where the average of the weight increase amounts is 1. In FIG. 5, the weight increase amount of the glass particles newly deposited in the second and third traverses is added to the weight increase amount (FIG. 3) measured and calculated previously, and is shown as a ratio of the total weight increase amount. Show. It is possible to calculate the distribution of only the weight increase of newly deposited glass particles and make it uniform in the next traverse, but by calculating the distribution with the ratio of the total weight increase, there will be less error in integration. The accuracy can be increased. As is clear from FIG. 5, the variation in weight increase at each position is smaller than that in FIG.

In order to obtain a final target glass thickness of 30 mm for laminating in the case of transparent vitrification (outer diameter of glass base material is 90 mm), traverse is performed 155 times, and final 15
The traverse speed is 400m in the 6th final traverse.
Adjustment was carried out by raising to m / min. The soot preform formed as described above was dehydrated and sintered into a transparent glass. FIG. 6 shows the glass outer diameter distribution in the longitudinal direction of the transparent glass base material manufactured as described above. The glass outer diameter was about 90 mm over the entire length of the effective range, and a glass base material having a uniform outer diameter with a total weight of 6217 g could be obtained. The ratio of "core diameter / clad diameter" was also substantially uniform over the entire length of the effective range.

As a comparative example of the present invention, using the same starting glass rod 1, reaction vessel 4 and burner 6 as in the specific example of the present invention, to obtain a glass base material having the same diameter of 90 mm and a total weight of 6217 g as in the specific example, The soot layer 3 was formed.
However, do not install a thermoviewer and laser distance measuring device,
The soot layer outer diameter and surface temperature for adjustment control were not measured. From the burner 6, SiC as a glass raw material
l ₄ of 12 SLM are constantly supplied, H ₂ for flame formation is 240 SLM, O _{2 is} for 120 SLM, and Ar gas 6 SL for shielding H ₂ and O ₂ near the burner outlet.
M was constantly supplied. The number of traverses is the same as in the specific example, 1
The soot preform thus prepared was dehydrated and sintered 56 times to form a transparent glass.

FIG. 7 shows the glass outer diameter distribution in the longitudinal direction of the transparent glass base material manufactured in the above comparative example. The glass outer diameter fluctuated greatly in the longitudinal direction, and the center value also greatly exceeded the target of 90 mm, and as a result, the total weight also exceeded the target value.

[0040]

As is apparent from the above description, according to the present invention, it is possible to deposit glass particles in a predetermined amount in the longitudinal direction of the starting glass rod with high accuracy and to obtain an outer diameter in the longitudinal direction. It is possible to easily obtain a uniform transparent glass base material or a transparent glass base material having a uniform ratio of the glass rod diameter and the glass base material diameter according to the outer diameter of the starting glass rod. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating a method of calculating a soot layer outer diameter.

FIG. 3 is a diagram showing a weight distribution after the first traverse.

FIG. 4 is a diagram showing a supply amount distribution of a glass raw material during a second traverse.

FIG. 5 is a diagram showing a weight distribution after a third traverse.

FIG. 6 is a view showing an outer diameter distribution of a transparent glass base material manufactured according to the present invention.

FIG. 7 is a diagram showing an outer diameter distribution of a transparent glass base material of a comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Starting glass rod, 2 ... Dummy rod, 3 ... Soot layer, 4 ... Reaction container, 5 ... Driving device, 6 ... Burner, 7 ... Vertical observation window, 8 ... Temperature measuring device, 9 ... Observation small window, 10 ... Distance measuring device, 11 ... Soot position measuring device, 12 ... Gas supply device, 13 ... Arithmetic device, 14 ... Control device.

Claims (14)

[Claims] 1. A method for producing a glass base material, wherein a starting glass rod is traversed in a longitudinal direction while rotating, and glass fine particles generated by a burner are deposited on an outer periphery of the starting glass rod to form a soot layer. The glass surface fine particle deposition surface temperature fluctuation distribution and outer diameter fluctuation distribution is measured, for each traverse or for each predetermined traverse,
The weight distribution of the newly deposited soot layer is calculated, and the variation of the weight distribution obtained by adding the weight distribution calculated in the past or the weight distribution calculated in the past is reduced so that the deposition amount of the glass fine particles after the next traverse is reduced. A method for producing a glass base material, which comprises adjusting. 2. The method for producing a glass preform according to claim 1, wherein the starting glass rod is a core glass for an optical fiber or a glass including a core and a clad. 3. When the outer diameter of the core glass fluctuates in the longitudinal direction or the ratio of the core diameter to the clad diameter of the glass consisting of the core and the clad fluctuates in the longitudinal direction, the outer circumference of the starting glass rod is Adjusting the deposition amount of the glass fine particles by setting the weight distribution of the soot layer such that the ratio of the core diameter and the glass diameter of the glass body obtained after vitrifying the deposited glass fine particles becomes transparent. The method for manufacturing a glass base material according to claim 2, wherein 4. The bulk density of the soot layer is specified from the measured deposition surface temperature of the glass fine particles, and the weight of the soot layer is calculated from the bulk density and the outer diameter of the soot layer. Item 2. A method for producing a glass base material according to Item 1. 5. The method for producing a glass base material according to claim 1, wherein the soot layer outer diameter is calculated based on the result of measuring the distance to the surface of the soot layer. 6. The method for producing a glass base material according to claim 1, wherein the deposition amount of the glass fine particles is adjusted by increasing or decreasing the glass raw material gas from the burner while keeping the traverse speed constant. 7. The production of a glass base material according to claim 1, wherein the deposition amount of the glass fine particles is adjusted by keeping the amount of the glass raw material gas from the burner constant and changing the traverse speed. Method. 8. The method for producing a glass base material according to claim 6, wherein the adjustment of the deposition amount of the glass fine particles is performed by simultaneously increasing and decreasing the oxyhydrogen gas. 9. The method for producing a glass base material according to claim 1, wherein a radiation thermometer is used for measuring the temperature of the deposition surface of the glass particles. 10. The method for producing a glass preform according to claim 5, wherein a laser distance measuring device is used for measuring the distance to the surface of the soot layer. 11. The laser distance measuring device is arranged on one side or both sides of the burner in a longitudinal direction of the soot layer, and a laser beam is applied at a distance of 5 cm or more from the burner. 10. The method for producing a glass preform according to item 10. 12. The frosted glass is used as a part of the starting glass rod, and a laser beam is applied to the frosted glass to measure the distance to the surface of the starting glass rod prior to the formation of the soot layer. The method for producing a glass base material according to claim 10. 13. An apparatus for producing a glass base material, which comprises a reaction vessel, a drive device for traversing a starting glass rod in a longitudinal direction while rotating the starting glass rod, and a burner for producing glass fine particles to be deposited on the outer circumference of the starting glass rod. A soot position measuring device for measuring the longitudinal position of the soot layer, a radiation thermometer for measuring the deposition surface temperature of the glass particles, and a laser distance measuring device for measuring the outer diameter of the soot layer. apparatus for manufacturing a glass preform, characterized in that it comprises an arithmetic unit to calculate the weight distribution of the soot layer deposited from the deposition surface temperature and the outside diameter of the glass particles. 14. Based on the weight distribution of the soot layer,
The glass base material manufacturing apparatus according to claim 13, further comprising a control device that adjusts the deposition amount of the glass fine particles.