JPS6221735B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing optical transmission glass. Conventional, square type (graded type or focused type)
In a method for manufacturing a cylindrical transparent glass rod for manufacturing an optical fiber having a refractive index distribution, a source gas serving as a glass soot is reacted,
By depositing soot, which is fine glass particles, in the axial direction,
Various methods are known for forming soot rods and sintering the soot rods to obtain transparent glass. These methods include, for example, (i) preparing multiple raw material supply ports, ejecting source gases with different dopant concentrations from each supply port, and producing soot rods with different compositions in the radial direction by high-temperature oxidation or flame hydrolysis; (Refer to JP-A-51-71316 and JP-A-52-143037); (ii) The deposition surface of the soot rod is heated to have a temperature gradient in the radial direction, and the deposition efficiency of the dopant soot is increased. A method based on changing the composition in the radial direction to produce soot rods with different compositions in the radial direction (see Japanese Patent Application Laid-Open No. 53-21936); However, these conventional methods have the disadvantage that it is difficult to set conditions for forming a dopant concentration distribution in the radial direction. For example, method (i) above requires a large number of parameters such as the composition ratio and flow rate of the main glass component and dopant, the amount of hydrogen and oxygen in the oxyhydrogen burner, the arrangement of multiple burners, and the temperature control of the target surface. It is difficult to optimize each independently. In addition, method (ii) has the disadvantage that the dependence of the dopant deposition efficiency on the target temperature is not so pronounced and that it is not possible to increase the amount of change in the dopant concentration in the radial direction. This method has the disadvantage of complicating the equipment configuration, such as requiring the provision of _two lasers or an oxyhydrogen burner. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing optical transmission glass that eliminates the above-mentioned drawbacks. In the present invention, when a mixed source gas of a source gas serving as the main glass component and a source gas serving as a dopant reacts with water vapor and an oxidizing agent other than water vapor, the ratio of the main glass component to the dopant in the produced glass soot is The focus is on the fact that the reaction temperature varies depending on the reaction temperature and water vapor concentration. Therefore, the feature of the method for manufacturing optical transmission glass of the present invention is to prepare a plurality of source gases which become glass soot through hydrolysis or oxidation, and preferably into a glass-based source gas which becomes glass-based through oxidation. A composite jet comprising a dopant source gas that becomes a dopant by hydrolysis, water vapor, and an oxidizing agent other than water vapor, and the jet is substantially cylindrical; The concentration of water vapor in the cylinder is changed in the radial direction of the cylinder, preferably by ejecting the water vapor from a central nozzle in the jet fluid, and the water vapor is heated, and the glass soot produced by the heating is heated. is deposited on a rotating starting member, and the deposited material is grown in the axial direction to produce a glass soot rod, which is then sintered to produce a cylindrical transparent glass having an arbitrary refractive index distribution in the radial direction. It's about being with your body. According to the method of the present invention, glass rods having different compositions in the desired radial direction can be easily manufactured without complicated operations or equipment configurations as in conventional methods. In other words, the water vapor ejected from the central nozzle diffuses in the radial direction, and the water vapor concentration is maximum at the central axis of the composite jet and minimum at the periphery, and the concentration changes depending on the relative amount of water vapor ejected. Therefore, it is possible to easily manufacture a cylindrical transparent glass body having an arbitrary refractive index distribution in the radial direction by fabricating soot rods having arbitrarily different dopant concentrations in the radial direction. be. The method of the present invention will be explained in more detail below with reference to the drawings. As shown in the conceptual diagram of FIG. 1, in the method of the present invention, a composite jet consisting of a glass main component source gas, a dopant source gas, water vapor, and an oxidizing agent other than water vapor is jetted from a composite nozzle 1. It is ejected upward. A central nozzle 2 concentric with the composite nozzle 1 is provided at the center of the composite nozzle 1, and water vapor is ejected from the central nozzle.
Therefore, the water vapor portion 4 in the composite jet 3 having a substantially circular cross section is diffused from the center to the periphery within the jet 3 along with the flow of the jet, with a high concentration in the center. , the concentration is low in the periphery. This jet fluid 3 is heated by an external heating source 5, and a composite jet fluid 3 is generated in soot through a heating reaction. In this case, the amount of dopant soot produced is maximum at the center where the water vapor concentration is maximum, and minimum at the periphery where the water vapor concentration is minimum. Such a concentration distribution of dopant soot is deposited on the target surface 6 to form a soot rod 7 in an approximately square law type distribution in the form of an error function, as will be explained below. The soot rod thus produced can be sintered into a transparent glass rod with a radially varied composition and a refractive index distribution. In the above, the source gas, which is the dopant in the source gas, reacts only with water vapor, and the amount of reaction produced is approximately proportional to the amount of water vapor (amount of H ₂ O), and the source gas, which is the main component of the glass, reacts only with water vapor. Two conditions must be met: it reacts with an oxidizing agent, for example oxygen. Under these conditions, water vapor in the composite fluid ejects from the center and then diffuses in the radial direction.
The concentration distribution is shown in FIG. 2, where the vertical axis is the concentration m and the horizontal axis is the radius r on both sides of the center O. As shown by the curve β, the concentration is maximum at the center and minimum at the periphery. When a composite jet having such a water vapor distribution is heated and reacted to generate dopant soot, the amount of dopant soot generated is determined by the first condition listed above, and in Figure 3, the vertical axis is the product concentration. m', the horizontal axis is centered at O, and both sides are radii r. As shown by the curve δ, the amount of dopant soot is maximum at the center and minimum at the periphery, and the overall shape is an error function. This error function is
Therefore, the dopant in the glass soot rod indicated by numeral 7 in FIG. 1 is deposited in a square-law distribution. On the other hand, the source gas, which is the main component of the glass, reacts with an oxidizing agent other than water vapor, such as oxygen, ejected in the composite jet so as to have a uniform concentration in the radial direction, as shown by the curve α in FIG. As shown by the curve .gamma. in FIG. 3, the amount of the glass-based soot is deposited on the target surface with a constant distribution in the radial direction. Therefore, the soot rods deposited on the target surface have a square dopant concentration distribution in the radial direction, and the refractive index distribution in the transparent glass rod obtained by sintering such soot rods is shown in FIG. If Δn is the refractive index, and the horizontal axis is the center with O and the radius r on both sides, a square-shaped refractive index distribution is obtained as shown by the curve ε. As can be seen from the above explanation, in the method of the present invention, the hydrolysis of the dopant is controlled in the radial direction using an external heating source, so it is different from the conventional method using flame hydrolysis (Japanese Patent Application Laid-Open No. 1983-1995). 71316,
52-143037), it has the advantage that the heating temperature and amount of water vapor can be controlled independently. Therefore, it is easy to arbitrarily change the refractive index distribution, and it is easy to set conditions when manufacturing a glass rod having a square-shaped refractive index distribution. Furthermore, compared to conventional methods using flame hydrolysis, the method according to the invention allows the radial composition of the source gas in the composite jet to be measured in real time without being affected by the adverse effects of flame, and the soot rod Real-time control of radial composition is possible. As described above, the method of the present invention has various advantages, and its advantages can be fully demonstrated, especially when manufacturing a glass rod having a refractive index that changes in the radial direction. The present invention will be explained in more detail below using Examples. Example 1 In this example, SiHCl ₃ gas is used as the source gas for the main component of the glass, GeCl ₄ gas is used as the dopant source gas, and oxidation of SiHCl ₃ and hydrolysis of GeCl ₄ are used. . First, these two source gases meet the two conditions mentioned above, that is, the dopant source gas that becomes the dopant reacts only with water vapor, and the amount of reaction produced is approximately proportional to the amount of water vapor (H ₂ O amount), and The glass-based source gas, which is the main component, reacts with an oxidizing agent other than water vapor, such as oxygen,
It is shown that producing a glass soot satisfies the following. The graph in Figure 5 shows the relationship between the amount of soot produced by the reaction and the reaction temperature, with the vertical axis representing the product weight (mg) and the horizontal axis representing the reaction temperature (℃). shows the reaction of SiHCl ₃ + O ₂ , and curves b, b′, b″ show the reaction of GeCl ₄ + H ₂ O, corresponding to the flow rate ratio of H ₂ O/GeCl ₄ of 11.3, 6.6, and 2.0, respectively. Curve c is for the reaction of GeCl ₄ + O _2. As can be seen from the graph in Figure 5, the reaction temperature is set to about
If the temperature is set between 700°C and about 900°C, the dopant GeCl ₄ reacts only with water vapor, and the source gas, which is the main component of the glass, reacts with oxygen. Figure 6 is a graph showing the amount of soot produced versus the amount of H ₂ O/GeCl ₄ in the reaction GeCl ₄ + H ₂ O. Curves d, d', and d'' indicate the reaction temperatures of 1075°C, 1290°C, and 860°C, respectively. ℃. This graph shows that the amount of dopant soot produced tends to be slightly saturated as the amount of water vapor increases, but it is almost proportional to the amount of glass-based source gas and dopant in this example. It can be seen that the composite source gas consisting of the source gas satisfies the two necessary conditions mentioned above.For the production of a glass rod having a radial squared refractive index distribution using such a source gas, An apparatus as shown in Fig. 7 was used. In Fig. 7, reference numeral 1 indicates a composite nozzle, which includes a central nozzle 2 and concentric annular nozzles 9, 10, 11,
12, H ₂ O and O ₂ flow from the central nozzle 2, and annular nozzles 9, 10, 11, 12
From Ar, SiHCl ₃ and GeCl ₄ , Ar,
_O2 was blown out. In this case, the reason why Ar was flowed out was to prevent soot from adhering to the end of the nozzle. The flow rate of each gas in each nozzle was set to the values shown in Table 1.

[Table] When each gas is ejected at the above-mentioned flow rates, the water vapor flow 4 from the central nozzle 2 in the composite jet 3 diffuses to the periphery as it reaches the upper part. This composite jet fluid 3 is heated by an electric furnace 13 which is an external heating source.
As a result of heating to a temperature of 980℃, soot occurs,
Soot rod 7 was formed. When this soot rod 7 was rotated and simultaneously pulled upward and further heated to a temperature of 1300° C. in the upper part of the electric furnace 12, a transparent glass rod 8 was obtained by sintering. When the refractive index with respect to the radius r of the glass rod thus formed was measured, a substantially square-shaped refractive index distribution as shown by the curve ε' in the graph of FIG. 8 was obtained. The glass rod thus manufactured by the method of the present invention was suitable for optical transmission as shown below. That is, the glass rod obtained as described above was welded into a quartz tube by the rod incubation method and drawn to produce an optical fiber. The transmission band of this optical fiber is 800MHz with 6dB down.
km, and the transmission loss was 3 dB/Km. Therefore, the optical fiber manufactured using the optical transmission glass manufactured by the method of the present invention has excellent transmission band and transmission loss. It can be seen that this is a manufacturing method for glass for industrial use. Example 2 In Example 1, the dopant was GeO ₂ , but in this example, the dopant was P ₂ O ₅ and
This is the case when Al ₂ O ₃ is used. In the case of this example as well, the manufacturing apparatus was as shown in FIG. 7 as in Example 1, except that the gas flow rate and reaction temperature were as shown in Table 2.

[Table] The transmission band of the optical fiber manufactured in the same manner as in Example 1 is as follows for the glass rod manufactured under the same conditions as in Example 1 except for the flow rate and reaction temperature. 400MHz・Km when doped with P ₂ O ₅ , and 400MHz・Km when doped with Al ₂ O ₃ .
At 600MHz/Km, the transmission loss is 2.5dB/
Km, 12dB/Km. The transmission loss when doped with Al ₂ O ₃ is somewhat large, but the reason is that Al ₂ O ₃
This is thought to be due to the crystallization of Example 3 In the glass systems in Examples 1 and 2 above, one type of dopant was added,
Even if two or more types of dopants are added, it is possible to manufacture a glass rod for optical transmission having a square-law type refractive index distribution in the radial direction.In this example, the following two types of dopants were added.
Examples of types of glass are shown below. SiO ₂ ―P ₂ O ₅ ―GeO ₂ SiO ₂ ―B ₂ O ₃ ―GeO ₂ In the above system, both POCl ₃ and GeCl ₄ , which are dopant source gases, do not undergo an oxidation reaction and are only hydrolyzed. Wake up SiHCl ₃
is the temperature at which the oxidation reaction occurs, i.e. from 650℃
Glass rods with a radial squared refractive index profile were obtained by thermally reacting the composite jet at temperatures in the range of 750°C. In addition, in the above system, the temperature at which _BBr3 , which is the source gas _{of B2O3} , undergoes an oxidation reaction and _GeCl4 only undergoes a hydrolysis reaction, that is, 900℃.
Glass rods with a radial squared refractive index profile were obtained by thermally reacting the composite jet at temperatures ranging from 1000°C to 1000°C. As described above, according to the method of the present invention, glass rods having a radial squared refractive index distribution can be obtained very easily in various glass systems, and the effects of the present invention can be said to be extremely large. I can do it. In Examples 4 to 6 below, a plurality of source gases that are hydrolyzed or oxidized to become glass soot, and a composite gas consisting of water vapor or an oxidizing agent are reacted in a reaction zone having a temperature gradient in the radial direction to produce glass soot. The glass soot to be used is deposited on a rotating starting member and subsequently grown in the axial direction to produce a glass soot rod, which is then heated and sintered to create an arbitrary refractive index profile in the radial direction. The present invention relates to a method for producing light transmission glass that obtains a cylindrical transparent glass body having the following properties. In the above, the plurality of source gases are those that become glass-based soot and dopant soot through hydrolysis or oxidation, and the oxidizing agent is oxygen, for example, and a nozzle having a temperature gradient in the radial direction is used. For example, an annular nozzle with a heating element in the center can be used. In order to carry out these methods, an apparatus as shown in the conceptual diagram of FIG. 9 is used. In this device, a center heater 21 having a heat source in a concentric tube is provided at the center of a reaction tube 20, and the outside is heated by an external heating source 22. The temperature is distributed in the radial direction, with the outer wall of the heater 21 having a high temperature and the inner wall of the reaction tube 20 having a low temperature. The state of the temperature distribution is shown by the temperature t on the vertical axis.
℃, and the horizontal axis is the radius r, which is the distance from the center O.
It is as shown by curve e in FIG. 10, which is a graph in which the length of is taken on both sides of the center O.
That is, the maximum temperature is t ₀ °C at the outer wall r ₀ of the central heater 21, and the temperature decreases as it moves away from the outer wall of the central heater 21,
The temperature distribution is such that the lowest temperature is t ₁ °C up to the position of the inner wall r ₁ . When using such a device to feed multiple types of source gas from below the reaction tube 20 and simultaneously feed oxygen gas or water vapor, the state of the oxidation or hydrolysis reaction of the source gas may vary depending on the type of source gas. , the composition of the soot deposited as soot rods varies in the radial direction because of the radial temperature distribution. As a result, the transparent glass rod obtained by sintering the above-mentioned soot rod is
A refractive index distribution is formed in the radial direction, and by optimizing the manufacturing conditions, it is possible to manufacture a glass rod for an optical fiber having a square-shaped refractive index distribution in the radial direction. In this way, according to the methods of Examples 4 to 6, the only parameter necessary to optimize the radial change in glass composition is the temperature distribution of the reaction tube,
Glass rods for optical fibers having a square-law type refractive index distribution can be easily manufactured. The relationship between the reaction temperature and the amount of soot generated from the source gas is shown for _SiCl4 , which is a source gas mainly composed of glass.
The graph of FIG. 11 shows the values measured using oxygen gas as an oxidizing agent and GeCl ₄ as a dopant source gas. In Figure 11,
The horizontal axis is the reaction temperature, and the vertical axis is the relative weight when the amount of soot produced is set to 100, and the curve f
is for SiCl ₄ and curve g is for GeCl ₄ . Example 4 The soot rod in this example requires stable deposition of the soot, which is the main component of the glass, uniformly in the radial direction, and the soot, which is the dopant, is varied in the radial direction. . As can be seen from Figure 11, this condition is such that SiCl ₂ is 100
% reacts uniformly and is satisfied by choosing a temperature range where the reaction amount of GeCl ₄ depends on the temperature.
When the glass main component source gas is SiCl ₄ and the dopant source gas is GeCl ₄ , such a temperature range is a temperature range R ₁ of approximately 1100°C or higher, as seen in Figure 11, and is actually If the temperature distribution is such that the temperature is 1100°C or higher in the center of the reaction tube and about 1100°C in the peripheral area, a soot rod can be obtained in which the dopant concentration is maximum in the center. In fact, the apparatus used to manufacture a glass rod having a square-law type refractive index distribution is as shown in the cross-sectional explanatory diagram of FIG. 12. In FIG. 12, at the center of the reaction tube 20 is a central heater 21 made of a glass rod with a built-in platinum wire.
, oxygen is supplied from the two concentric annular portions 23 and 25, and oxygen is supplied from the concentric annular portion 24 in the middle thereof.
SiCl ₄ and GeCl ₄ were jetted out. These gases were heated by the electric furnace 26 and the heater 21 at the center of the reaction tube to generate soot, which was deposited to form a soot rod 27. In this case, reaction tube 2
The diameter dimension of 0 is that the outer diameter of the central heater 21 is 5 mm,
The annular portions 23, 24, and 25 had outer diameters of 10 mm, 15 mm, and 20 mm, respectively. Further, the flow rate of each gas and the temperature at the center portion and the temperature at the peripheral portion of the reaction tube were as shown in Tables 3 and 4.

【table】

[Table] The radial refractive index distribution of the glass rod manufactured under the above conditions is shown by curve h in FIG. FIG. 13 is a graph in which the horizontal axis represents the radius length and the vertical axis represents the refractive index. It can be seen from FIG. 13 that the radial refractive index distribution of the obtained glass rod is approximately square-shaped. The above-mentioned glass rod thus manufactured was welded into a quartz tube using the rod incubation method and the resulting optical fiber had a transmission band of 600M.
Hz/Km, transmission loss was 4.5 dB/Km. Therefore, the method according to the present invention is extremely effective as a method for manufacturing square-shaped transparent glass rods for manufacturing optical fibers. Example 5 This example is a case where water vapor was used as the oxidizing agent in Example 4. As a source gas,
_SiCl4 and _GeCl4 were used. FIG. 14 is a graph showing the measured relationship between the amount of soot produced and the reaction temperature in the hydrolysis reaction of SiCl ₄ and GeCl ₄ . 14th
In the figure, the horizontal axis is the reaction temperature, the vertical axis is the weight of the produced soot, and the curve k is for SiCl ₄ .
Curve l is for _GeCl4 . Example 4
For the reasons stated in , a soot rod suitable for optical fibers was manufactured by decomposing the source gas in the same manner as in Example 4 in the temperature range _R2 ranging from about 700°C to about 1200°C. I know what I can do. Using the apparatus used in Example 4, soot rods were manufactured under the conditions of the flow rate of each gas and the set temperature shown in Tables 5 and 6, and then heated and sintered to manufacture glass rods.

【table】

[Table] The transmission band of the optical fiber manufactured in the same manner as in Example 4 using the glass rod thus obtained was 400MHz/Km, and the transmission loss was
5 dB/Km, confirming the effectiveness of the method of the present invention. Example 6 Using the same equipment and operation as in Example 4, various reaction systems were prepared using a glass-based source gas, a dopant source gas, and an oxidizing agent or hydrolyzing agent in a reaction zone with a temperature distribution. When the operating temperature range suitable for obtaining a glass rod having a square-law type refractive index distribution was determined, the results shown in Table 7 were obtained.

[Table] In order to actually produce a glass rod with a square-law type refractive index distribution using the reaction system and temperature conditions shown in Table 7, in the reaction systems 1) to 4), the center of the reaction tube must be The temperature of the tube should be set near the upper limit of the operating temperature range, and the surrounding area should be set near the lower limit of the operating temperature range.For reaction systems 5) and 6), conversely, the center section of the reaction tube should be used. It is preferable to set the temperature near the lower limit of the temperature range and the peripheral part near the upper limit of the operating temperature range. Optical fibers manufactured in the same manner as in Example 4 using the glass rods of each of the reaction systems thus manufactured had transmission bands of 300 MHz·Km or more. Therefore, by using the method of the present invention, it is possible to produce a glass rod for optical fiber having a square refractive index in almost all reaction systems. Further, by the method of the present invention, if the radial temperature distribution is made constant, a glass rod with a constant radial refractive index distribution can be obtained. In this way, the method of the invention has the advantage of making it possible to produce optical fibers with almost any refractive index profile. Example 7 This example relates to the production of a transparent glass rod with a radially varying index of refraction, suitable for use as a graded optical fiber. Conventionally, the manufacturing method of graded optical fiber is
Known methods include a vapor-phase shafting method using multiple burners, an external method in which glass layers with different compositions are sequentially deposited in the radial direction, and an internal method. In order to form a composition distribution corresponding to a graded refractive index distribution using these methods, for example, in the axial mounting method, it is necessary to optimize the burner arrangement, and therefore the manufacturing equipment configuration must be optimized. It had the drawback of becoming complicated. In this embodiment, in order to eliminate the drawbacks of the prior art as described above, a soot rod made of multiple compositions is manufactured using a vapor phase axial method, etc., and then a dopant material is added to the outer periphery of the soot rod by heat treatment. evaporates only to form a composition distribution in the radial direction. As shown in Fig. 15, the soot rod manufacturing principle is as shown in Fig. 15.
It is necessary to spatially separate the flame hydrolysis reaction region 33 by the dopant source gas burner 32 from the reaction region 34 of the source gas to be a dopant by the dopant source gas burner 32. At this time, the soot is deposited so that the macroscopic composition is uniform in the radial direction. When the reaction regions are separated as described above, the soot particles produced by the reaction and deposited in the axial direction have a single composition, and therefore the soot rod has uniformly deposited particles of a single composition. 35 is obtained, and by heat-treating it, the dopant material can be easily evaporated. Now, SiCl ₄ is selected as the main component source gas and sent from the burner 31, and at the same time, H ₂ gas and O ₂ gas are sent for flame hydrolysis. At the same time, H ₂ and O ₂ were sent from the burner 32 as a source gas to serve as a dopant at the same time as POCl ₃ to perform flame hydrolysis in the same manner. The soot rod 35 manufactured in this way was left in a large electric furnace for a long time at a temperature that did not allow sufficient sintering.
_P2O5 was evaporated _. As a result, P ₂ O ₅ at the outer periphery
A soot rod with a low concentration of P 2 O 5 and a high concentration of P ₂ O ₅ in the center was obtained. When the soot rod in which the composition distribution was formed in the radial direction was sintered at an even higher temperature, a transparent glass rod in which the refractive index changed in the radial direction was obtained. A graded optical fiber was obtained by welding the thus obtained glass rod to a quartz tube to produce a pre-ohm and drawing it, and the effect of this example was confirmed. Example 8 This example uses high-purity quartz fine powder as a starting material, forms dopant oxides such as GeO ₂ on its surface by oxidation or hydrolysis of raw material gas, and produces doped silica rods. It is about the method. The apparatus used in Examples 8 and 9 is as shown in the cross-sectional explanatory view of FIG. 16. This device consists of a hopper 40, a quadruple tube 41, and a reaction chamber 42, and the quadruple tube has an innermost tube nozzle 4 communicating with the hopper 40.
3. Nozzles 44, 4 sequentially arranged on the outside thereof
5 and 46, and a reaction chamber 42 is provided at the bottom of the quadruple tube 41. A device (not shown) having a rotating and lowering mechanism is provided below the reaction chamber 42, and is adapted to sequentially lower the deposits generated in the reaction chamber 42. In such an apparatus, crystal fine particles 47 having a particle size of about 1 μm are put into the hopper 40,
From the innermost tube nozzle 43 of the quadruple tube into the reaction chamber 42,
It is made to fall at a rate of 1g to 5g per minute. GeCl ₄ gas is supplied from the outer nozzle 44, and GeCl 4 gas is supplied from the nozzle 45.
O ₂ gas and H ₂ gas are ejected from the nozzle 46 and combusted within the reaction chamber 42 .
The flow rates of each gas at this time are as follows. GeCl ₄ : 100-500c.c./min O ₂ : 5-10/min H ₂ : 5-10/min By combustion under the above conditions, GeCl ₄ becomes O ₂ in the reaction chamber 42. A hydrolysis reaction is caused by the high temperature H ₂ O generated by the combustion of GeO 2 and H 2 , resulting in GeO ₂ with a _yield of almost 100%, which is uniformly mixed with the fine powder of SiO ₂ falling from the innermost tube nozzle 43. The resulting SiO ₂ --GeO ₂ fine powder 48 is collected on a target provided below. While rotating the target, it was lowered in synchronization with the growth rate of the SiO ₂ -GeO ₂ fine powder deposited on the target (not shown), and after several hours of deposition, a diameter of approximately 8 to 10 cm was obtained.
A finely powdered rod 49 with a length of about 10-40 cm was obtained. When this fine powder rod was zone melted at 1500°C, a GeO ₂ -doped silica glass rod having a diameter of about 5 to 8 cm and a length of about 8 to 30 cm was obtained. Example 9 In the same manner as in Example 8, instead of GeCl ₄ , BBr ₃ ,
When using POCl ₃ or BF ₂ or a combination of these gases, similar glass rods were obtained in each case, and the composition showed good agreement with the value calculated from the gas phase composition. . Example 10 This example relates to a method for collecting sooty silica glass fine powder. Fine silica glass powder produced by flame hydrolysis of SiCl ₄ , high-temperature hydrolysis using an electric furnace, or high-temperature oxidation reaction using plasma or the like is usually deposited and collected on a target. In this case, the collection efficiency is 30 to 50% in the hydrolysis method and 10 to 20% in the high temperature oxidation method.
Both are low. According to the method of this embodiment, a filter 5 is placed above the collection tube 51 as shown in the cross-sectional explanatory view of FIG.
2 is provided, the soot-like glass (SiO ₂ fine powder) 57 generated from the soot-like glass generator 56 is passed through the exhaust pipe 53, adjusted by the regulating valve 54, and suctioned by the vacuum pump 55, onto the lower surface of the filter 52. The soot-like glass fine powder can be collected extremely efficiently by collecting it in a deposition manner. In FIG. 17, SiCl ₄ is supplied to a soot glass generator 56, which is an Ar, O ₂ plasma torch, at a rate of 50 per minute.
The generated SiO ₂ fine powder 57 is sent at a rate of cc.
It was ejected toward the collection tube 51. At the start of collection, the inside of the collection tube 51 was evacuated through the exhaust pipe 53 by the vacuum pump 55. The degree of vacuum was adjusted using a regulating valve 54, which is a needle valve, and was increased as the collection time elapsed. After about one hour, the amount of glass soot deposited at the bottom of the filter 52 was examined, and it was found that it was about 7 g, and the yield was over 90%. In addition, the surface of the soot deposit 58 and the soot generator 5
6, a semi-sintered soot deposit was obtained. The above example uses a high-temperature oxidation reaction, but when a hydrolysis reaction is used, the
It is preferable to prevent HCl and excess water from condensing in the collection tube and near the filter. If HCl or the like condenses near the filter, the exhaust capacity will decrease, making it difficult for the soot flow to be efficiently collected toward the collection tube. To prevent condensation, the entire collection tube or a portion thereof may be heated using a subheater or the like. Further, the vertical positions of the collection pipe and the soot generator may be reversed, in which case it is convenient to trap condensation such as HCl below. The glass fine powder thus obtained is of high purity and can be used as a raw material for glass for optical fibers. Furthermore, if the collection tube is made longer and the fine powder is collected evenly in the collection tube, approximately 1200
Transparent glass rods can be obtained by heating and vitrifying at ~1300°C. Also, furthermore,
If a glass tube with a lower refractive index than the vitrified rod is used as the collection tube, it is possible to obtain a preform for an optical fiber by heating and welding it directly at a temperature of 1500° C. or higher. Example 11 This example relates to a method for collecting extremely fine sooty glass particles produced in a gas phase reaction. The apparatus used in the method of this embodiment is as shown in the cross-sectional explanatory diagram of FIG. 18. The device shown in FIG. 18 includes a soot-like glass particle generator 61, a side pipe 63,
A collection target 6 which is connected to a granulation tube 62 with a granulation tube 63' and which is rotated and pulled upwards.
4 is provided. The soot-like glass particle generator 61 usually
Flame hydrolysis burner for glass raw materials such as _SiCl4 ,
The soot, which is a high-temperature reaction product that comes out of the generator 61, which is composed of a high-temperature oxidation nozzle, a direct hydrolysis nozzle, etc., is normally in a gas state, but as it leaves the nozzle, its temperature decreases and it becomes soot-like. Glass particles are generated. Conventionally, these fine particles were collected as they were on the target 64. In this embodiment, soot-like glass is generated more efficiently than the conventional method and collected at a high yield. For the above purpose, in this example, the first
As shown in Figure 8, the soot-like glass particle generator 6
1 is supplied to the granulation tube 62, and extremely low temperature gas generated from liquid oxygen or liquid nitrogen is supplied into the granulation tube 62 from the side tubes 63, 63'. Glass particles 66 are made to merge with the flow of soot-like glass particles 65 generated by the generator 61, thereby being efficiently granulated.
The collection target 64 is rotated and pulled up.
The glass porous body 67 is formed by collecting the glass particles. Therefore, the soot-like glass particles generated by the generator 61 can be collected at a higher yield than in the conventional method. In the actual measurement test, SiCl ₄ was applied at 200 c.c./min to the soot-like glass particle generator 61, which is an oxyhydrogen burner.
Ar was introduced as a carrier gas at a rate of . From the side pipes 63 and 63', low-temperature O ₂ gas generated from liquid oxygen was fed at a rate of 2/min, respectively. By doing so, the SiO ₂ fine particles 66 generated and granulated in the granulation tube 62 were collected on the target 64, and the target 64 was pulled up while rotating in correspondence with the deposited SiO ₂ fine particles. After about 1 hour of operation, the weight of the deposited glass particles was measured and was found to be 27 g. This weight is 100% SiCl ₄ fed into the generator 61.
The collection efficiency was approximately 85% based on the weight of product calculated as converted to SiO ₂ . As a comparative example, the collection efficiency was measured when the supply of liquid oxygen was stopped and other conditions were kept the same as above, and it was 50% or less. In the above operation, the collection target 64 is used, but instead of the collection target, a collection bottle or the like may be used for collection. In this case, it is preferable that the temperature of the collection unit is lower than the temperature of the sooty glass flow in order to obtain a high collection rate. Alternatively, the particles may be collected by heating again after granulation. By doing so, HCl generated by the hydrolysis reaction of SiCl ₄ etc. can be dispersed. Also, the relative positions of the soot generator and collection unit may be reversed. Furthermore, we used raw materials such as GeCl ₄ , POCl ₃ , and BBr ₃ in addition to SiCl ₄ and used multiple soot generators with different compositions to control the composition distribution in the radial direction of the deposited glass porous rod. You can also let it stand. In addition, even if soot generators with the same composition are used, the granulation rate of components such as GeO ₂ can be increased compared to SiO ₂ components by changing the flow rate of the cooling gas, and this effect can be used to increase the radius It is also possible to form a composition distribution in the direction.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram for explaining the present invention, Figure 2 is a conceptual diagram for explaining the present invention.
The figure is a graph showing the water vapor concentration distribution in the radial direction of the jet fluid and the concentration distribution of the glass-based source gas in the method of the present invention, and Figure 3 is the amount of dopant soot and glass-based soot produced in the radial direction in the case of Figure 2. FIG. 4 is a graph showing the radial refractive index distribution in the produced glass rod in the cases of FIGS. Figure 5 is a graph showing the relationship between the amount of soot produced by the source gas and the reaction temperature, and Figure 6 is a graph showing the relationship between the amount of soot produced by the source gas and the reaction temperature _.
2 is a graph showing the relationship between the amount of dopant produced and the water vapor ratio. FIG. 7 is a cross-sectional explanatory diagram of the apparatus used in Examples 1, 2, and 3 of the present invention, and FIG. 8 is a graph showing the refractive index distribution with respect to the radius of the glass rod manufactured according to Example 1 of the present invention. be. Fig. 9 is a conceptual diagram of Examples 4 to 6, Fig. 10 is a graph showing the temperature distribution in the radial direction, and Fig. 11 shows the relationship between the amount of soot produced by oxidation of SiCl ₄ and GeCl ₄ and the reaction temperature. It is a graph. FIG. 12 is a cross-sectional explanatory diagram of the reaction device of Example 4, and FIG. 13 is a graph showing the radial refractive index distribution in the glass rod obtained in Example 4.
FIG. 4 is a graph showing the relationship between the soot production amount and temperature when water vapor is used as the oxidizing agent in Example 5. FIG. 15 is an explanatory cross-sectional view of the soot rod manufacturing apparatus used in Example 7. FIG. 16 is an explanatory cross-sectional view of the apparatus for producing fine powder rods used in Examples 8 and 9. Figure 17 shows Example 10
FIG. FIG. 18 is an explanatory cross-sectional view of the soot-like glass particle collection device used in Example 11. DESCRIPTION OF SYMBOLS 1... Composite nozzle, 2... Center nozzle, 3... Compound jet, 4... Water vapor flow, 5, 22... External heating source, 6
...Target surface, 7, 27, 35... Soot rod, 8... Glass rod, 9, 10, 11, 12...
Annular nozzle, 13, 26... electric furnace, 20, 42...
Reaction tube, 21...Central heater, 23, 24, 25
...Annular portion, 31...Main component source gas burner, 3
2... Dopant source gas burner, 40... Hopper, 41... Quadruple tube, 43... Innermost tube nozzle, 44,
45, 46...outer nozzle, 49...fine powder rod,
51... Collection pipe, 52... Filter, 53... Exhaust pipe,
55...Vacuum pump, 56...Soot-like glass generator,
58... Soot deposit, 61... Sooty glass fine particle generator, 62... Granulation tube, 63, 63'... Side tube, 6
7...Glass porous body.

Claims (1)

[Claims] 1. A glass source gas that becomes a glass main component mainly through oxidation, an oxidizing agent other than water vapor that oxidizes the glass source gas, and a dopant source gas that becomes a dopant mainly through hydrolysis.
A substantially cylindrical composite jet is formed of water vapor that hydrolyzes the dopant source gas, and the water vapor that hydrolyzes the dopant source gas is distributed radially from the central axis of the cylindrical composite jet. heating the composite jet to form a glass soot, and depositing the formed glass soot on a rotating starting member to form a glass soot rod. , and then sintering this to form a cylindrical transparent glass body having an arbitrary refractive index distribution in the radial direction.