JP4349148B2 - Glass processing method and glass processing apparatus - Google Patents

Description

  The present invention relates to a glass processing method such as an optical fiber preform and a glass processing apparatus.

  In the manufacturing process of a glass body such as an optical fiber base material, for example, deposition of a glass layer by an MCVD (Modified Chemical Vapor Deposition) method, integration of a glass rod and a glass pipe by a rod-in collapse method, a glass rod and a dummy as a product There are many processes for heating and processing a glass body, such as connecting rods and stretching glass rods and glass pipes.

Conventionally, as a heat source for heating such a glass body, a burner using a mixed gas of hydrogen (H ₂ ) and oxygen (O ₂ ) or a mixed gas of propane (C ₃ H ₈ ) and oxygen has been used. It was. However, when these heat sources are used, hydrogen and hydroxyl groups (OH groups) enter the glass body from the surface of the glass body to be processed and diffuse, and the optical fiber obtained from the glass body is transmitted. Loss may be deteriorated.

  By the way, in recent optical fibers that require large-capacity transmission, the refractive index distribution of the core is complicated, and the region in which signal light propagates is widened. In order to form such a light propagation region, it is necessary to deposit glass fine particles in the starting glass pipe over a long period of time by the MCVD method.

  In this case, in the burner using oxyhydrogen or the like, hydrogen and hydroxyl groups easily enter and diffuse into the starting glass pipe by heating for a long time, which is a factor of deteriorating transmission loss. Therefore, methods such as shortening the deposition time of glass particles as much as possible, or increasing the thickness of the starting glass pipe to be used so that hydrogen and hydroxyl groups are not diffused to the light propagation region have been taken. . When such a method is used, the former method limits the increase in size of the optical fiber preform. In the latter method, heat conduction to the inside of the starting glass pipe is hindered, so that the speed of generation and deposition of glass fine particles is reduced.

  Under such circumstances, it has been proposed to heat a glass body with a thermal plasma torch which is a heat source that does not use hydrogen. In a thermal plasma torch, a tubular torch body made of, for example, quartz glass is inserted into the center of a coil through which a high-frequency current is passed, and argon (Ar) or air is introduced into the torch body to A plasma flame according to the size can be generated. An optical fiber preform manufacturing method that uses an thermal plasma torch in the MCVD method to obtain an optical fiber product with less impurities such as hydrogen and hydroxyl groups is disclosed (for example, see Patent Document 1).

  By using such a thermal plasma torch that does not use hydrogen, intrusion of impurities such as hydrogen and hydroxyl groups into the glass body is significantly suppressed as compared with the case of using a conventional burner that uses oxyhydrogen.

Japanese Patent No. 2818735

  By the way, the factors that affect the speed at which the glass fine particles are deposited in the MCVD method are the production efficiency of the glass fine particles and the deposition efficiency on the glass pipe determined by the thermophoresis effect. In order to increase the deposition speed, it is important to form an optimal heating region in order to increase the generation efficiency and deposition efficiency of the glass fine particles. In addition, in the integration of the glass rod and the glass pipe, the connection of the glass rod and the dummy rod, and the stretching of the glass rod and the glass pipe, an optimal heating region is formed while preventing the penetration of hydrogen and hydroxyl groups, and good thermal processing is performed. Is required to do. However, in the above-described thermal plasma torch, the intensity of the generated plasma flame is only controlled by adjusting the overall gas flow rate and the high-frequency power applied from the coil.

  An object of this invention is to provide the glass processing method and glass processing apparatus which adjust the magnitude | size of a heating area | region according to a to-be-processed object and processing conditions.

The glass processing method according to the present invention capable of achieving the above object includes a plurality of ports for ejecting gas, and introduces a first gas to be plasmatized into an inner port among the plurality of ports, A torch body for introducing a second gas acting as a seal gas into an outer port of the ports and ejecting the second gas in a spiral shape, and means for applying a high frequency to the gases introduced into the plurality of ports; A glass processing method for heating a glass body by generating a plasma flame using a thermal plasma torch having a center of the torch body by controlling the flow rates of the first gas and the second gas An adjusting step of adjusting the spread of the plasma flame in a direction orthogonal to the axis, and a heating step of heating the glass body with the plasma flame adjusted by the adjusting step. It is a symptom.

In the glass processing method according to the present invention, it is preferable that the gas introduced into the plurality of ports includes at least one of helium, argon, oxygen, nitrogen, and air.

Further, in the glass processing method according to the present invention, the gas to be introduced into said plurality of ports are preferably all the same composition.

Further, in the glass processing method according to the present invention, the gas to be introduced into said plurality of ports consists gas plurality composition, it is preferred to introduce the gas one composition to one of the ports.

In the glass processing method according to the present invention, the gas introduced into the plurality of ports preferably has a dew point of 0 ° C. or lower.

Moreover, in the glass processing method which concerns on this invention, it is preferable that the gas introduce | transduced into these ports has a dew point of -50 degrees C or less.

Also, in the glass processing method according to the present invention, said adjusting step, the temperature distribution of the glass body was measured, introduced to the plurality of ports including a gas to be introduced into the outer port on the basis of the measured temperature distribution It is preferable to control the flow rate of the gas.

Further, in the glass processing method according to the present invention, the glass body is preferably an optical fiber preform.

Further, in the glass processing method according to the present invention, the glass body is a glass pipe, the heating step includes introducing a source gas for producing glass particles into the glass pipe, the said thermal plasma torch while relatively traversing the longitudinal direction of the glass pipe, and heating the glass pipe is preferably a step of depositing the glass particles on the inside of the glass pipe.

Moreover, in the glass processing method which concerns on this invention, it is preferable after the said heating process to have the process of adjusting the spreading of the said plasma flame again, and the process of heating and solidifying the said glass pipe.

Further, the glass processing apparatus according to the present invention capable of achieving the above object comprises a plurality of ports for ejecting a gas, introduces a first gas to be plasmatized into an inner port among the plurality of ports, A torch body for introducing a second gas acting as a seal gas to an outer port of the plurality of ports and ejecting the second gas in a spiral shape, and a high frequency applying means for applying a high frequency to the gas introduced to the port And a flow rate adjusting means for adjusting the flow rates of the first gas and the second gas.

  In the glass pipe manufacturing apparatus according to the present invention, it is preferable that moving means for moving the thermal plasma torch relative to and away from the glass body is provided.

  Further, in the glass pipe manufacturing apparatus according to the present invention, the temperature distribution measuring means for measuring the temperature distribution of the glass body, and the high frequency applying means, the flow rate adjusting means or the movement based on the temperature distribution measured by the temperature distribution measuring means. Preferably, there is provided control means for controlling the temperature distribution by controlling at least one of the means.

  According to the glass processing method and the glass processing apparatus according to the present invention, the heating area of the generated plasma flame can be adjusted by adjusting the amount of gas introduced into each port. Accordingly, the size of the heating region is adjusted to form an optimum heating region, and good glass processing can be performed.

Hereinafter, an example of an embodiment of a glass processing method and a glass processing device concerning the present invention is explained with reference to drawings.
FIG. 1 is a conceptual diagram showing an embodiment of a thermal plasma torch used in the glass processing method and glass processing apparatus of the present embodiment, and FIG. 2 is a front view of the torch main body shown in FIG.
The thermal plasma torch 10 includes a torch body 5 having a plurality of ports P1, P2, P3, and P4 for ejecting gas, and high-frequency applying means 8 that applies a high frequency to the gas introduced into the torch body 5.

  The torch body 5 has a multiple tube structure in which a plurality of cylindrical pipes 1, 2, 3, 4 having different diameters are concentrically arranged. A gap between the central pipe 1 and the pipes 1, 2, 3, 4 forms ports P1, P2, P3, P4. A coil 7 is provided on the outer periphery of the torch body 5, and a high frequency power source 6 is connected to the coil 7. The coil 7 and the power source 6 constitute high frequency application means 8 for applying a high frequency to the gas in the torch body 5. The frequency of the high frequency current passed by the power supply 6 is, for example, 13.56 MHz.

A gas supply pipe (not shown) communicating with the ports P1, P2, P3, and P4 is connected to one end of the torch body 5, and these gas supply pipes are connected to the ports P1, P2, P3, and P4. A gas having a composition containing at least one of helium, argon, oxygen, nitrogen (N ₂ ), and air is introduced. An arbitrary gas of helium, argon, oxygen, nitrogen, or air may be selectively mixed and used for one port. Moreover, you may introduce | transduce the gas of the same composition to all the ports.

  By applying a high frequency current from the power source 6 to the coil 7, a high frequency is applied to the gas introduced into each port P1, P2, P3, P4. Then, the gas is turned into plasma and ejected from the ports P1, P2, P3, P4, and a plasma flame F is generated.

  Here, since the thermal plasma torch 10 includes a plurality of ports P1, P2, P3, and P4, the presence / absence and amount of gas introduced into each port P1, P2, P3, and P4 are adjusted. The spread of the plasma flame F in the direction orthogonal to the central axis of the torch body 5 can be adjusted. For example, when generating the smallest plasma flame, the gas is introduced only into the central port P1, and the plasma flame is generated only from the port P1.

  As described above, the thermal plasma torch 10 can easily adjust the spread of the generated plasma flame F, and can form a heating region having an appropriate spread according to the heating object and heating conditions. And when heating the elongate glass body G as shown in FIG. 1, according to the magnitude | size of the diameter of the glass body G, and the heating length of the longitudinal direction requested | required, each port P1, P2, P3 The presence or absence of gas introduction into P4 is adjusted to generate an optimally spread plasma flame F to form a desired heating region, and good glass processing can be performed.

  Further, in the example of the embodiment shown in FIG. 1, the high-frequency applying unit 8 that applies a high frequency to the gas introduced into the torch body 5 is configured to flow a high-frequency current from the power source 6 to the coil 7. Is also applicable.

  FIG. 3 is a conceptual diagram showing another embodiment of the thermal plasma torch used in the glass processing method and glass processing apparatus of the present invention. The thermal plasma torch 10a shown in FIG. 3 includes high frequency applying means in which an annular resonator 7a (only the half of the annular shape is shown) is provided on the outer periphery of the torch body 5. A power source 6a capable of generating a high frequency (microwave) is connected to the resonator 7a, and microwaves are emitted from the resonator 7a toward the torch body 5 by resonating the microwave with the resonator 7a. can do. A microwave frequency of 2.4 GHz, for example, is preferable because a generally versatile microwave power source can be used as the power source 6a.

  Also in the case of this thermal plasma torch 10a, when the microwave is irradiated from the resonator 7a in a state where gas is appropriately introduced to each port P1, P2, P3, P4, the introduced gas is ionized and each port P1, P2, P3 is ionized. , P4 generates a plasma flame F. Since the spread of the generated plasma flame F can be adjusted by adjusting the presence / absence and amount of gas introduced into each port P1, P2, P3, P4, the glass body G can be formed by a desired heating region. Can be heated for good processing. The thermal plasma torches 10, 10a can also adjust the temperature of the plasma flame by adjusting the frequency and energy of the applied high frequency.

The structure of the torch body 5 is not limited to the thermal plasma torches 10 and 10a.
4 and 5 are front views of other embodiments of the torch body constituting the thermal plasma torch.
The torch main body 5a shown in FIG. 4 has a plurality of rectangular pipes 1a, 2a, 3a, 4a arranged in a nested manner, and a gap between the central pipe 1a and the pipes 1a, 2a, 3a, 4a is formed. , Ports P1, P2, P3 and P4 are formed, respectively.

  In the torch body 5b shown in FIG. 5, ports P1, P2, P3, P4, P5 and P6 having the same shape are arranged in a line. When a long glass body is heated using the torch body 5b, the torch body 5 is preferably arranged so that the ports P1, P2, P3, P4, P5, and P6 are aligned in the longitudinal direction of the glass body.

  Even when these torch main bodies 5a and 5b are used, the spread of the generated plasma flame can be adjusted by adjusting the presence / absence of gas introduction to each port and the amount of introduction, and the heating object and processing conditions can be adjusted. A combined and appropriately expanded heating region can be formed.

  It is desirable that the number of ports formed in the torch main body is in the range of 2 to 6, and the plasma flame spreads, that is, the heating region is adjusted in the range of 2 to 6 stages. When the number of ports is more than 6, the applied high frequency is not easily transmitted to the central port, and there is a difference in the intensity of the plasma flame generated between the outer and inner ports. It is expected to become easy to do.

FIG. 14 is a cross-sectional view of another embodiment of the torch body. The torch body 55 includes a torch upper portion 57 and a torch lower portion 58.
The torch lower part 58 has a multi-pipe structure having pipes 51, 52, 53 having different diameters, and the gap between the central pipe 51 and the pipes 51, 52, 53 forms ports P1, P2, P3. Yes. A gas supply pipe communicating with each of the ports P1, P2, P3 is connected to each of the ports P1, P2, P3, and at least one of helium, argon, oxygen, nitrogen, or air. A gas having a composition including types is introduced. In this embodiment, if the gas introduced into the port P1 is the first gas, the gas introduced into the ports P2 and P3 may be a second gas having a composition different from that of the first gas. A partition 56 having honeycomb-like pores is provided at the tip of the port P1, and gas is jetted in parallel to the central axis of the torch body 55. A partition 59 having pores arranged spirally with respect to the central axis of the torch body 55 is provided at the distal ends of the ports P2 and P3, and gas is ejected spirally with respect to the central axis of the torch body 55. It is like that.

The pipe 53 extends to the tip of the torch main body 55 and constitutes a torch upper portion 57, thereby forming a space 60 for converting gas into plasma. In the space 60, the first gas mainly ejected from the port P1 is turned into plasma. Second the gas ejected from the port P2, P3 acts as seal gas to protect the pipe 53 from the plasma. As the second gas, a polyatomic gas having a large specific heat is preferably used, and nitrogen (N 2) can be used.

  Since the torch body 55 includes a plurality of ports, the spread of the plasma flame can be adjusted by adjusting the presence / absence and amount of gas introduced into each port. For example, if the amount of gas ejected from the port P1 is constant and the amount of gas ejected from the ports P2 and P3 is increased, the plasma flame is throttled and the plasma density is increased. Further, if the amount of gas ejected from the ports P2 and P3 is made constant and the flow rate of the gas ejected from the port P1 is increased, the plasma flame expands and the plasma density increases. Further, the total amount can be adjusted with the ratio of the gas ejected from each port P1, P2, P3 being constant.

Thus, the torch body 55 can easily adjust the spread of the generated plasma flame, and can form a heating region with an appropriate spread according to the heating object and processing conditions.
The torch main body 55 has one port for jetting gas in parallel and two ports for jetting gas in a spiral shape, but the number of ports is not limited to this.

Next, the example of embodiment of the glass processing apparatus which concerns on this invention is demonstrated.
In addition to the thermal plasma torch having a torch body having a plurality of ports for ejecting gas and a high-frequency applying means for applying a high frequency to the gas introduced into the ports, the glass processing apparatus of the present embodiment includes each of the plurality of ports. There is provided a flow rate adjusting means for adjusting the flow rate of the gas to be introduced.
FIG. 7 is a conceptual diagram showing the glass processing apparatus of the present embodiment, and FIG. 6 is a side view of a glass lathe having the glass processing apparatus of FIG.

A glass lathe 21 shown in FIG. 6 is an apparatus mainly used when performing the MCVD method.
The glass lathe 21 has a base 12 on which support portions 11 are erected in the vicinity of both ends. Each of the support portions 11 has a rotatable chuck 13, and these chucks 13 respectively hold the end portions of the glass pipe G that is a glass body and horizontally support the glass pipe G. Below the glass pipe G supported by the chuck 13, the thermal plasma torch 10 for heating the glass pipe G is provided.

  The thermal plasma torch 10 is supported on a moving table 18 mounted on the support rail 17, and the moving table 18 can move along the longitudinal direction of the support rail 17 by a rack and pinion mechanism. The support rail 17 and the glass pipe G are disposed so that their longitudinal directions are parallel to each other. In addition, a stage (moving means) 19 for moving the thermal plasma torch 10 relatively close to and away from the glass pipe G is provided on the upper part of the moving table 18, and the thermal plasma torch 10 is placed on the stage 19. It is fixed. Instead of the uniaxial (lifting / lowering) stage that moves the thermal plasma torch relatively to and away from the glass body, a triaxial stage whose position can be adjusted in the horizontal plane may be used. . Further, the support portion 11 is connected to a source gas supply pipe 22 on one side and an exhaust pipe 23 on the other side.

The glass processing apparatus 20 shown in FIG. 7 is mounted and used, for example, on the glass lathe 21 of FIG.
As shown in FIG. 7, the thermal plasma torch 10 is connected to an MFC (Mass Flow Controller) 31 which is a flow rate adjusting means for adjusting the flow rate of the gas introduced into each port P1, P2, P3, P4.

  Further, the glass processing device 20 includes a temperature distribution measuring device (temperature distribution measuring means) 34 for measuring the temperature distribution of the glass body, and the high frequency applying means described above based on the temperature distribution measured by the temperature distribution measuring device 34. The apparatus further includes a control device (control means) that controls at least one of the MFC 31 and the stage 19 to adjust the temperature distribution.

  The temperature distribution measuring device 34 measures the temperature distribution of the glass pipe G based on the detection signal from the radiation thermometer 33 that detects the temperature of the glass pipe G, and transmits the measured temperature distribution data to the control device 32. To do. The temperature distribution may be measured along the longitudinal direction of the surface temperature of the glass pipe G with respect to the heating region heated by the thermal plasma torch 10. Therefore, the radiation thermometer 33 is configured to be able to move along the longitudinal direction of the glass pipe G, and measures the temperature of the glass pipe G in the constantly heated region in accordance with the movement of the thermal plasma torch 10. Can do.

  The control device 32 can control the power supply 6, the stage 19, and the MFC 31 based on the temperature distribution data transmitted from the temperature distribution measurement device 34. When the power source 6 is controlled, the temperature of the plasma flame F can be adjusted by controlling the frequency and the magnitude of energy. When controlling the stage 19, the relative position between the glass pipe G and the thermal plasma torch 10 can be adjusted to form a heating region at a desired position. In particular, by adjusting the distance between the thermal plasma torch 10 and the glass pipe G, the heating temperature to the glass pipe G can be adjusted without changing the temperature of the plasma flame F. When the MFC 31 is controlled, the gas flame can be flowed to a desired port to adjust the spread of the plasma flame F, and the temperature of the plasma flame can be adjusted by adjusting the flow rate.

Next, an example of an embodiment of the glass processing method according to the present invention will be described.
The glass processing method of the present embodiment uses a thermal plasma torch having a torch main body having a plurality of ports for ejecting gas and means for applying a high frequency to the gas introduced into the ports, to generate a plasma flame to generate glass. A glass processing method that includes heating the body, controlling the flow rate of gas introduced into each of the plurality of ports, and adjusting the spread of the plasma flame in the direction perpendicular to the central axis of the torch body, A heating step of heating the glass body with the plasma flame adjusted by the adjusting step. The gas introduced into the port is preferably at least one of helium, argon, oxygen, nitrogen, and air.

  Next, glass layer deposition (MCVD method) which is an embodiment of the glass processing method of the present invention will be described. In the MCVD method, the glass body is a glass pipe, and the heating step introduces a raw material gas for generating glass fine particles into the glass pipe and traverses the thermal plasma torch in the longitudinal direction of the glass pipe, This is a step of heating to deposit glass particles inside the glass pipe.

FIG. 8 is a conceptual diagram illustrating the MCVD method. The glass pipe G supported on the chuck 13 (see FIG. 6) is rotated, and oxygen is transferred from the source gas supply pipe 22 into the glass material such as silicon tetrachloride (SiCl ₄ ) or germanium tetrachloride (GeCl ₄ ) into the glass pipe G. A raw material gas consisting of a mixed gas to which is added is fed. In this state, a plasma flame F having a desired spread is generated from the thermal plasma torch 10 and traversed a plurality of times in the longitudinal direction.

The glass pipe G is heated by the plasma flame F, and silica glass fine particles (SiO ₂ ) are generated inside the glass pipe G in the heating region. The fine glass particles adhere to and accumulate on the inner peripheral surface of the glass pipe G on the downstream side of the flow of the source gas due to the thermophoretic effect. Thereafter, the deposited glass particles are heated and densified by the moving thermal plasma torch 10 to sequentially form a glass film G1.

  In the MCVD method, the glass pipe G is sufficiently heated to improve the generation efficiency of the glass fine particles, and the inner surface of the glass pipe G on the downstream side of the flow of the raw material gas is kept at a relatively low temperature so that the glass is produced by the thermophoresis effect. It is desired to improve the deposition efficiency of fine particles. Therefore, in the MCVD method, it is preferable to increase the temperature of the plasma flame F and narrow the heating region.

  In the present embodiment, the adjusting step for adjusting the spread of the plasma flame F measures the temperature distribution of the glass pipe G and controls each MFC based on the measured temperature distribution. In particular, in the present embodiment, the control device 32 controls each MFC 31 based on the temperature distribution data from the temperature distribution measuring device 34, adjusts the presence and amount of gas flowing to each port, and spreads the plasma flame F. Adjust. Thus, the glass pipe G is heated with a temperature distribution having a steep temperature gradient, and the glass film G1 is efficiently formed. When the heating area by the plasma flame F is narrowed, it is possible to suppress a minute amount of moisture, metal impurities and the like contained in the atmosphere from being ionized and entering and diffusing into the glass pipe G.

  After the glass film G1 is deposited over a plurality of layers in the glass pipe G, the glass pipe G is again heated by the plasma flame F of the thermal plasma torch 10 and is reduced in diameter to be solidified. Alternatively, the glass rod G is inserted into the center of the glass pipe G, and then the glass pipe G is heated by the plasma flame F to reduce the diameter, and the glass pipe G is integrated with the glass rod.

  At this time, it is desirable to have a step of adjusting the spread of the plasma flame F again after the step of depositing the glass film G1. At this time, the control device 32 controls the MFC 31 again based on the temperature distribution data from the temperature distribution measuring device 34, adjusts the presence / absence and amount of gas flowing to each port P1, P2, P3, P4, and plasma flame. The temperature and heating area of F are adjusted to values suitable for solidification. In the solidification step, it is preferable to lower the temperature of the plasma flame F and widen the heating region. Thereby, the diameter reduction of the glass pipe G occurs at a uniform rate in the longitudinal direction, and uniformization can be achieved.

  In the example of the above embodiment, the presence / absence and amount of gas introduced into each port P1, P2, P3, P4 of the thermal plasma torch 10 are adjusted, but the composition differs for each port P1, P2, P3, P4. Depending on the size of the glass body to be processed and the processing conditions, select the composition of the gas to be introduced and adjust the heating area and temperature of the plasma flame so that the desired temperature distribution is obtained. May be.

  Further, the information to be fed back when adjusting the presence / absence and amount of gas flowing through each port P1, P2, P3, P4 is not limited to the temperature distribution of the glass pipe G, but changes for each traverse of the thermal plasma torch 10. Possible outer diameter or inner diameter of the glass pipe G and the film thickness of the glass film G1 can be used. In addition to the MFC 31, the control device 32 controls the frequency and energy of the high frequency applied by the high frequency applying means 8 or the distance between the thermal plasma torch 10 and the glass pipe G by the stage 19, thereby controlling the temperature of the plasma flame F. The position of the thermal plasma torch 10 relative to the glass pipe G may be adjusted so that the glass pipe G has a predetermined temperature distribution.

  Further, in order to obtain good controllability of the temperature distribution by adjusting the gas flow rate of the MFC 31, the gas at each port P1, P2, P3, P4 of the thermal plasma torch 10 is a laminar flow or a flow close thereto. It is preferable. In this case, the Reynolds number of the gas flow is preferably in the range of 2000 to 3000.

  FIG. 9 and FIG. 10 show the concept of a glass processing apparatus for reliably preventing the entry of a small amount of moisture, metal impurities, etc. contained in the atmosphere into the glass pipe G in the step of depositing the glass film G1. FIG. 9 includes a cover 41 that covers only the heating region of the thermal plasma torch 10 and the glass pipe G, and FIG. 10 includes a cover 42 that covers the plasma flame F of the thermal plasma torch 10 and the entire glass pipe G. It is provided. These covers 41, 42 do not necessarily need to cover the entire thermal plasma torch 10, as long as they cover at least the plasma flame F as in the example shown in FIG. 10.

  The covers 41 and 42 are provided with a gas introduction port 43 and a gas discharge port 44. During the heat processing, a dry gas is introduced, and the vicinity of the heating region of the glass pipe G has a low moisture and a clean atmosphere. Retained. The dry gas is preferably a clean inert gas such as nitrogen, argon or helium having a metal impurity concentration of 1 ppm or less. The dry gas preferably has a dew point of 0 ° C. or lower, but more preferably has a dew point of −50 ° C. or lower.

  According to the glass processing apparatus having such a structure, moisture and impurities can be removed from the atmosphere around the plasma flame F, and impurity ions enter the glass pipe G during the deposition process of the glass film G1. Can be reliably prevented. In addition, it is desirable that the gas introduced into the thermal plasma torch 10 is a dry gas having a low dew point (0 ° C. or lower, preferably −50 ° C. or lower) as described above when the optical fiber preform is manufactured by the glass processing apparatus. In this way, it is possible to more reliably prevent moisture from entering the glass pipe G.

  The glass processing method and the glass processing apparatus according to the present invention are also applied to various glass processing such as glass rod and glass pipe connection, glass body stretching process such as optical fiber preform, flame polishing, and distortion removal. it can. FIG. 11 is a conceptual diagram illustrating connection of glass rods, which is another embodiment of the glass processing method of the present invention. When the glass rods G2 and G2a are connected to each other, the connecting end surfaces of the glass rod G2 are heated and softened by the plasma flame F of the thermal plasma torch 10, and abut each other.

  FIG. 12 is a conceptual diagram illustrating stretching of a glass rod, which is another embodiment of the glass processing method of the present invention. When the glass rod G3 is stretched, the glass rod G3 is heated by the plasma flame F of the thermal plasma torch 10 and pulled by a predetermined pulling force while rotating the glass rod G3 around the axis.

  FIG. 13 is a conceptual diagram illustrating flame polishing of a glass rod, which is another embodiment of the glass processing method of the present invention. When the glass rod G4 is subjected to flame polishing, the glass rod G4 is heated along the longitudinal direction by the plasma flame F of the thermal plasma torch 10 while rotating around the axis. As a result, the glass layer on the surface of the glass rod G4 can be vaporized to remove minute scratches and distortions and attached foreign matter.

  And according to said thermal plasma torch 10, also when connecting, extending | stretching, or flame polishing as mentioned above, the heating area | region of a plasma flame according to the heating length required in the outer diameter of a glass body or a longitudinal direction By adjusting the above, these processes can be performed satisfactorily while suppressing the intrusion of impurity ions. In particular, in the case of connection, the intrusion of impurity ions into the glass rod can be significantly suppressed by heating and connecting only the connection portion efficiently and accurately.

  A quartz glass pipe having an outer diameter of 34 mm and an inner diameter of 26 mm was heated using the glass lathe 20 described above. The torch body provided on the glass lathe 20 is the torch body 55 shown in FIG. 14, and the outer diameter of the torch upper part 57 is 80 mm. The rotation speed of the quartz glass pipe during heating is 90 rpm, the traverse speed of the torch body is 100 mm / min, the gas supplied to the torch body is dry air, the high frequency power is 30 kW, and the frequency is 3 MHz. The surface temperature of the quartz glass pipe in each case was measured with a radiation thermometer while changing the flow rates V1, V2, and V3 (SLM: Standard Litter per minute) of the gas flowing through the ports P1, P2, and P3. As the measurement results, the maximum temperature and the length of the portion heated to 1700 ° C. or higher (the length of the heating region) are shown in Table 1. In addition, the length of a heating area | region is the length of the longitudinal direction of a quartz glass pipe. As shown in Table 1, it is understood that the maximum temperature and the size of the heating region can be adjusted by adjusting the spread and temperature of the plasma flame by changing the flow rate of each gas.

  The relationship between the heat source of the MCVD method, the amount of moisture diffusing into the glass, and the transmission loss when using an optical fiber was investigated. On the inner side of 11 quartz glass pipes having an outer diameter of 34 mm, an inner diameter of 28 mm and containing 0.3 wt% of chlorine (Cl), a glass having a relative refractive index 0.4% larger than that of the quartz glass pipe was deposited by the MCVD method. Among them, a thermal plasma torch was used as a heat source for 10 quartz glass pipes, and the dew point of the gas introduced into the torch body was changed for each quartz glass pipe. For the remaining one quartz glass pipe, an oxyhydrogen burner was used as a heat source for comparison. In any case, after depositing 40 layers of glass films at a deposition rate of 1 g / min per minute, the quartz glass pipe was heated using a thermal plasma torch and reduced in diameter to be solidified. Thus, a glass rod having a core / cladding structure was obtained. A portion of this glass rod was cut into pieces and the hydroxyl group concentration (wtppm) on the surface of the glass rod was measured by the microscopic FT-IR method.

Further, this glass rod was inserted into another glass pipe, and the glass pipe was integrated by heating to reduce the diameter to obtain an optical fiber preform. The glass pipe used here has a wall thickness of 1.7 times the diameter of the glass rod. The optical fiber preform was drawn, and the resulting single mode optical fiber was measured for transmission loss α _{1.38 at a} wavelength of 1.38 μm and absorption intensity Δα _OH due to hydroxyl groups. The results are shown in Table 2. The characteristics of the optical fiber at a wavelength of 1.55 μm are as follows: dispersion is 17 ps / nm / km, dispersion slope is 0.06 ps / nm ² / km, transmission loss is 0.185 dB / km, and effective area A _eff is 75 μm ^2. Met.

  When an optical fiber of a different type from that of Example 2 was manufactured, the relationship between the heat source in the MCVD method and the transmission loss when the optical fiber was used was examined. The same process as in Example 2 was performed until the glass layer was deposited by the MCVD method. In Example 2, the quartz glass pipe on which the glass layer was deposited by the MCVD method was directly reduced in diameter to obtain a glass rod. In Example 3, the relative refractive index difference at the center of the quartz glass pipe was 0.5%, A glass rod having a relative refractive index difference of −0.4% at the peripheral portion was inserted into the quartz glass pipe, and the quartz glass pipe was heated by a thermal plasma torch and reduced in diameter to be integrated. Thus, a glass rod having a core depressed ridge clad structure was obtained.

Further, this glass rod was inserted into another glass pipe, and the glass pipe was integrated by heating to reduce the diameter to obtain an optical fiber preform. The glass pipe used here has a wall thickness 2.3 times the diameter of the glass rod. The optical fiber preform was drawn, and the resulting dispersion-shifted optical fiber was measured for transmission loss α _{1.38 at a} wavelength of 1.38 μm and absorption intensity Δα _OH due to hydroxyl groups. The results are shown in Table 3. The characteristics of the optical fiber at a wavelength of 1.55 μm are as follows: dispersion is 6 ps / nm / km, dispersion slope is 0.03 ps / nm ² / km, transmission loss is 0.190 dB / km, and effective area A _eff is 50 μm ^2. Met.

As shown in Tables 2 and 3, the concentration of hydroxyl groups in the case of using a thermal plasma torch as compared with the case where the heat source is an oxyhydrogen burner is significantly reduced, and the transmission characteristics of the optical fiber are also good. When the gas dew point was 0 ° C. or less, the transmission loss α _1.38 was 0.4 dB / km or less, and when the gas dew point was −50 ° C. or less, the transmission loss α _1.38 was 0.3 dB / km or less. .

It is a conceptual diagram which shows one Embodiment of the thermal plasma torch used with the glass processing method which concerns on this invention. It is a front view of the torch main body which comprises the thermal plasma torch shown in FIG. It is a conceptual diagram which shows other embodiment of the thermal plasma torch used with the glass processing method which concerns on this invention. It is a front view of other embodiment of the torch main body which comprises a thermal plasma torch. It is a front view of other embodiment of the torch main body which comprises a thermal plasma torch. It is a side view of the glass lathe which has the glass processing apparatus of FIG. It is a conceptual diagram which shows one Embodiment of the glass processing apparatus which concerns on this invention. It is a conceptual diagram which shows an example of the glass layer deposition which is one Embodiment of the glass processing method which concerns on this invention. It is a conceptual diagram which shows the other example of the glass layer deposition which is one Embodiment of the glass processing method which concerns on this invention. It is a conceptual diagram which shows the other example of the glass layer deposition which is one Embodiment of the glass processing method which concerns on this invention. It is a conceptual diagram which shows the connection of the glass rod which is other embodiment which concerns on the glass processing method of this invention. It is a conceptual diagram which shows extending | stretching of the glass rod which is other embodiment which concerns on the glass processing method of this invention. It is a conceptual diagram which shows flame polishing of the glass rod which is other embodiment which concerns on the glass processing method of this invention. It is a front view of other embodiment of the torch main body which comprises a thermal plasma torch.

Explanation of symbols

1, 2, 3, 4 Pipes 5, 5a, 5b, 55 Torch main body 6, 6a Power source 7 Coil 7a Resonator 8 High frequency applying means 10 Thermal plasma torch 19 Stage (moving means)
20 Glass processing equipment 21 Glass lathe 31 MFC (flow rate adjusting means)
32 Control device (control means)
34 Temperature distribution measuring device (temperature distribution measuring means)
F Plasma flame G Glass pipe (glass body)
P1 to P6 ports

Claims (13)

A plurality of ports for ejecting gas; introducing a first gas to be converted into plasma into an inner port of the plurality of ports; and supplying a second gas serving as a seal gas to an outer port among the plurality of ports A glass body is generated by generating a plasma flame using a thermal plasma torch having a torch body that spirally injects the second gas and means for applying a high frequency to the gas introduced into the plurality of ports. A glass processing method for heating
An adjustment step of controlling the flow of the first gas and the second gas to adjust the spread of the plasma flame in a direction perpendicular to the central axis of the torch body;
The glass processing method characterized by having the heating process which heats the said glass body with the said plasma flame adjusted by the said adjustment process. In the glass processing method of Claim 1,
The glass processing method, wherein the gas introduced into the plurality of ports includes at least one of helium, argon, oxygen, nitrogen, and air. In the glass processing method of Claim 1 or 2,
The glass processing method characterized in that all the gases introduced into the plurality of ports have the same composition. In the glass processing method of Claim 1 or 2,
The gas introduced into the plurality of ports comprises a gas having a plurality of compositions,
A glass processing method comprising introducing a gas having one composition into one of the ports. In the glass processing method of any one of Claim 1 to 4,
The glass introduced into the plurality of ports has a dew point of 0 ° C. or less. In the glass processing method of Claim 5,
The glass introduced into the plurality of ports has a dew point of −50 ° C. or less. In the glass processing method of any one of Claim 1 to 6,
The adjusting step measures the temperature distribution of the glass body and controls the flow rate of the gas introduced into the plurality of ports including the gas introduced into the outer port based on the measured temperature distribution. Glass processing method. In the glass processing method of any one of Claim 1 to 7,
The glass body is an optical fiber preform, The glass processing method characterized by the above-mentioned . In the glass processing method of any one of Claim 1 to 8,
The glass body is a glass pipe,
The heating step introduces a raw material gas for generating glass fine particles in the glass pipe, heats the glass pipe while relatively traversing the thermal plasma torch in the longitudinal direction of the glass pipe, A glass processing method characterized by being a step of depositing the glass fine particles inside the glass pipe . The glass processing method according to claim 9 ,
After the heating step,
Re-adjusting the spread of the plasma flame;
A glass processing method comprising a step of heating and solidifying the glass pipe . A plurality of ports for jetting gas are provided, a first gas that is converted into plasma is introduced into an inner port of the plurality of ports, and a second gas that acts as a seal gas is introduced into an outer port of the plurality of ports. And a thermal plasma torch having a torch body for ejecting the second gas in a spiral shape and a high frequency applying means for applying a high frequency to the gas introduced into the port;
A glass processing apparatus, characterized in that a flow rate adjusting means for adjusting the flow rates of the first gas and the second gas is provided. In the glass processing apparatus of Claim 11,
A glass processing apparatus, characterized in that a moving means for moving the thermal plasma torch relative to and away from the glass body is provided . In the glass processing apparatus of Claim 12,
Temperature distribution measuring means for measuring the temperature distribution of the glass body ;
Control means for adjusting the temperature distribution by controlling at least one of the high frequency applying means, the flow rate adjusting means or the moving means based on the temperature distribution measured by the temperature distribution measuring means is provided. The glass processing apparatus characterized by the above-mentioned .