Optical fiber manufacturing apparatus and manufacturing method

Abstract

To provide an optical fiber manufacturing device that can improve gas recovery efficiency with an inexpensive method.SOLUTION: An optical fiber manufacturing device includes: a heating furnace 10 for heating and drawing an optical fiber preform; a gas suction port 14 for sucking a gas from the heating furnace; a gas purification device 33 for purifying the gas sucked from the gas suction port; a filter part 21 disposed between the gas suction port and the gas purification device; a mass flow controller 30 disposed between the filter part and the gas purification device; and a vacuum pump 32 disposed between the mass flow controller and the gas purification device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical fiber manufacturing apparatus and a manufacturing method.

Background Art

[0002] In the optical fiber manufacturing apparatus described in Patent Document 1, an example of recovering and reusing the helium gas used in the drawing furnace is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a conventional optical fiber manufacturing apparatus, the gas to be recovered is recovered through a filter, and it is conceivable that the flow rate changes when the filter becomes clogged. Therefore, an object of the present invention is to improve the gas recovery efficiency by an inexpensive method when recovering a gas such as helium used in a drawing furnace in an optical fiber manufacturing apparatus.

[0005] The present disclosure aims to improve the gas recovery efficiency by an inexpensive method.

Means for Solving the Problems

[0006] An optical fiber manufacturing apparatus according to one aspect of the present disclosure includes a heating furnace that heats and draws an optical fiber preform, a gas suction port that sucks gas from the heating furnace, a gas purification device for purifying the gas sucked from the gas suction port, a filter section disposed between the gas suction port and the gas purification device, A mass flow controller is positioned between the filter unit and the gas purification apparatus. A vacuum pump is placed between the mass flow controller and the gas purification apparatus. It is equipped with.

[0007] Furthermore, the optical fiber manufacturing method according to one aspect of this disclosure is: A heating furnace for heating the optical fiber preform and drawing the fiber, A gas suction port for drawing gas from the aforementioned heating furnace, A gas purification apparatus for purifying the gas drawn in from the gas intake port, A filter section is positioned between the gas suction port and the gas purification device. A mass flow controller is positioned between the filter unit and the gas purification apparatus. A vacuum pump is placed between the mass flow controller and the gas purification apparatus. A method for drawing optical fibers, comprising heating an optical fiber preform and drawing the fiber in an optical fiber manufacturing apparatus equipped with, The line drawing is performed while controlling the amount of gas drawn by the vacuum pump using the mass flow controller. [Effects of the Invention]

[0008] According to the above, gas recovery efficiency can be improved using inexpensive methods. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows an example of a manufacturing apparatus for optical fibers according to this disclosure. [Figure 2] Figure 2 is a flowchart showing the operating state of the optical fiber manufacturing apparatus shown in Figure 1. [Figure 3] Figure 3 shows another example of a manufacturing apparatus for optical fibers according to this disclosure. [Modes for carrying out the invention]

[0010] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. An optical fiber manufacturing apparatus according to one aspect of the present disclosure includes: (1) A heating furnace that heats and draws a preform of an optical fiber; A gas suction port that sucks gas from the heating furnace; A gas purification device for purifying the gas sucked from the gas suction port; A filter unit disposed between the gas suction port and the gas purification device; A mass flow controller disposed between the filter unit and the gas purification device; A vacuum pump disposed between the mass flow controller and the gas purification device; and The mass flow controller has a solenoid actuator valve. . According to this configuration, since the mass flow controller controls the flow rate, the amount of gas sucked by the vacuum pump can be kept constant, and the gas recovery efficiency can be improved by an inexpensive method. Furthermore, this configuration employs a mass flow controller with a solenoid actuator, reducing the delay in valve opening and closing, which allows the amount of gas drawn in by the vacuum pump to be kept constant, thus improving gas recovery efficiency.

[0012] ( 2 ) In the above (1) to The filter unit has a configuration in which two or more filters are arranged in parallel, and valves may be arranged on the upstream side and the downstream side of each of the filter units. According to this configuration, when the filter becomes clogged due to long-term use of the manufacturing apparatus, a new filter can be used by switching the flow path, so that the cost of maintaining the manufacturing apparatus can be reduced.

[0013] ( 3 ) In the above (1) or (2) to There may be a plurality of heating furnaces, and one vacuum pump and one gas purification device may be connected to the plurality of heating furnaces.​​​

[0014] ( 4 ) A heating furnace for heating the optical fiber preform and drawing the wire, A gas suction port for drawing gas from the aforementioned heating furnace, A gas purification apparatus for purifying the gas drawn in from the gas intake port, A filter section is positioned between the gas suction port and the gas purification device. A mass flow controller is positioned between the filter unit and the gas purification apparatus. A vacuum pump is placed between the mass flow controller and the gas purification apparatus. Equipped with 、 The mass flow controller has a solenoid actuator valve. A method for drawing optical fibers in an optical fiber manufacturing apparatus, which involves heating an optical fiber preform to draw the fiber, A method for manufacturing an optical fiber, comprising drawing a fiber while controlling the amount of gas drawn by the vacuum pump using the mass flow controller. With this configuration, the flow rate is controlled by a mass flow controller, allowing the amount of gas drawn in by the vacuum pump to be kept constant, thus improving gas recovery efficiency in an inexpensive way.

[0015] ( 5 )the above( 4 In this case, the line may be drawn while keeping the difference between the pressure upstream of the mass flow controller and the pressure downstream of the mass flow controller to 0.1 MPa or less. With this configuration, the gas flow rate can be controlled even if the pressure difference between the upstream and downstream sides of the mass flow controller is 0.1 MPa or less. This allows the amount of gas drawn in by the vacuum pump to be kept constant, improving the gas recovery efficiency.

[0016] ( 6 )the above( 4 )or( 5 In this case, the amount of gas drawn in may be controlled so that the internal pressure of the heating furnace is within a predetermined pressure range. This configuration prevents the internal pressure from becoming too negative, thus preventing air from entering the furnace and thus preventing a decrease in the strength of the manufactured optical fibers.

[0017] ( 7 )the above( 4 )from( 6 In any of the above, the oxygen concentration in the gas between the gas intake port and the gas purification device may be measured, and the amount of gas drawn in may be controlled based on the measurement result. With this configuration, the specific heat setting of the mass flow controller can be changed according to the oxygen concentration in the gas, so the amount of gas drawn in by the vacuum pump can be kept constant, improving the gas recovery efficiency.

[0018] [Details of the embodiments of this disclosure] Specific examples of optical fiber manufacturing apparatus according to the embodiments of this disclosure will be described below with reference to the drawings. However, the present invention is not limited to these examples, and is intended to include all modifications within the meaning and scope of the claims, as defined by the claims.

[0019] Figure 1 is a schematic diagram showing an example of an optical fiber manufacturing apparatus 1 according to the present disclosure. The optical fiber manufacturing apparatus 1 according to this embodiment is an optical fiber drawing apparatus that sequentially heats and melts a glass base material while supplying helium gas around it to draw optical fibers, and is equipped with a helium gas recovery mechanism at the bottom of the heating furnace 10 for recovering helium gas.

[0020] Furthermore, the optical fiber drawing method according to the embodiment of this disclosure is an optical fiber drawing method that sequentially heats and melts a glass base material while supplying helium gas around it to draw an optical fiber, characterized in that helium gas is recovered by a gas recovery mechanism located at the bottom of the heating furnace, and the recovered helium gas is purified and reused.

[0021] As shown in Figure 1, the optical fiber manufacturing apparatus 1 includes a heating furnace 10, a gas supply device 34, and a gas recovery mechanism 100.

[0022] The heating furnace 10 comprises a furnace core tube 12 positioned in the center of the furnace body 11 and heaters 13 positioned around the furnace core tube 12. A glass preform 2 for optical fibers is suspended and supported inside the furnace core tube 12. The heaters 13 heat the furnace core tube 12, and the heat from the heated furnace core tube heats the glass preform 2. By sequentially heating and melting the lower part of the glass preform 2, the optical fiber 3 is drawn continuously by the weight and tensile force of the molten glass. The drawn optical fiber 3 is then wound onto a drum or the like after undergoing cooling processes, coating processes, etc. (not shown).

[0023] The gas supply device 34 supplies gas such as helium into the reactor core tube 12. The helium gas is introduced to uniformly fill the space between the reactor core tube 12 and the glass base material 2, thereby equalizing the temperature distribution in the space within the reactor core tube 12. In particular, it suppresses turbulence caused by temperature differences in the neck-down section of the glass base material 2 where the space is larger, and prevents fluctuations in the diameter of the drawn optical fiber.

[0024] The gases that have passed through gas pipes 15a and 15b merge at their downstream ends and are then passed through the MFC 30.

[0025] In this disclosure, a gas intake port 14 is installed at the lower part of the core tube 12 (sometimes referred to as the lower chimney), and a gas recovery mechanism 100 is provided beyond the gas intake port 14. This configuration allows for the recovery of helium gas supplied to the heating furnace 10. The recovered helium gas is then supplied back to the heating furnace 10 through the gas recovery mechanism 100.

[0026] As shown in Figure 1, the gas recovery mechanism 100 includes a gas pipe 15, a valve 20, a filter 21, a mass flow controller 30 (an example of a flow regulator; hereinafter referred to as MFC), an oxygen concentration meter 31, a vacuum pump 32, a gas purification device 33, and a gas mixer 35. The gas recovery mechanism 100 uses the vacuum pump 32 to draw gas from inside the heating furnace 10 through the gas suction port 14.

[0027] The filter 21 is made of a heat-resistant material such as ceramics or metal, and can remove solid matter and other particles contained in the aspirated gas. In this embodiment, the downstream end of the gas pipe 15 is branched into two parallel pipes, and two or more filters 21 are provided in each of the branched gas pipes 15a and 15b. For example, a coarse filter may be provided on the upstream side and a fine filter on the downstream side. The gas only needs to pass through either of the branched gas pipes 15a or 15b.

[0028] Valves 20 are provided on both the upstream and downstream sides of the filter 21, so that if either filter 21 becomes clogged, gas will not flow into the gas pipe 15 to which the filter is located. Furthermore, the valve 20 allows adjustment of which of the branched gas pipes 15a and 15b the gas flows through. Therefore, even if one of the filters 21 becomes clogged, the flow path can be changed using the valve 20, eliminating the need to stop the gas recovery mechanism 100 when replacing the filter 21.

[0029] In this embodiment, the MFC30 is a solenoid actuator type MFC having a flow sensor 30a, a pressure sensor 30b, a control unit 30c, and a solenoid actuator valve 30d. The MFC30 is installed between the filter 21 and the gas purification device 33 and can adjust the flow rate of the gas drawn in by the vacuum pump 32.

[0030] The control unit 30c has a memory unit (not shown) which combines, for example, RAM and ROM, to store various data (information) necessary for calculation processing. This memory unit stores the valve characteristics of the solenoid actuator valve 30d that have been measured in advance. Valve characteristics refer to the relationship between the valve operating voltage and the gas flow rate, and the relationship between the gas pressure and the flow rate. When the valve operating voltage increases, the gas flow rate decreases. Also, as the gas pressure increases, the density of the gas increases, and therefore the gas flow rate also increases.

[0031] In this embodiment, an oxygen concentration meter 31 is connected to the MFC 30. The oxygen concentration meter 31 is configured to measure the oxygen concentration in the gas flowing through the gas pipe and transmit the measured oxygen concentration data to the MFC 30. The control unit 30c controls the solenoid actuator valve 30d by referring to the oxygen concentration data received from the oxygen concentration meter 31. The control unit 30c may also modify the valve characteristics of the solenoid actuator valve 30d stored in the memory unit by referring to the oxygen concentration data received from the oxygen concentration meter 31. The flow rate of the MFC 30 may be adjusted so that the oxygen concentration measured by the oxygen concentration meter 31 falls within a predetermined range.

[0032] A vacuum pump 32, a gas purification device 33, and a gas mixer 35 are connected downstream of the MFC 30. The vacuum pump 32 can provide suction force to draw gas from the heating furnace 10. The gas purification device 33 is a device that can separate the gas drawn from the heating furnace 10 into helium and non-helium gases. The gas purification device 33 may be configured to separate non-helium gases on its own. The gas mixer 35 can adjust the temperature, pressure, etc. of the gas so that the helium recovered and purified from the heating furnace 10 and the helium supplied from the gas supply device 34 can be supplied to the heating furnace 10.

[0033] Next, the operation of the gas recovery mechanism 100 will be described. Gas suction is performed by a vacuum pump 32. The vacuum pump 32 draws gas from inside the heating furnace 10 through the gas suction port 14. The amount of suction by the vacuum pump 32 is controlled by the MFC 30 so that the internal pressure of the heating furnace 10 is between 0 Pa and 20 Pa in terms of the pressure difference with atmospheric pressure. This prevents the internal pressure of the heating furnace 10 from becoming negative and prevents air from entering the heating furnace 10, thereby keeping the atmosphere inside the heating furnace 10 clean and preventing a decrease in the strength of the optical fibers 3 being manufactured.

[0034] The gas in the heating furnace 10, which is sucked in through the gas suction port 14 by the vacuum pump 32, is first passed through the gas pipe 15 to the filter 21.

[0035] The MFC30 adjusts the gas flowing in from the gas pipe 15 to a predetermined flow rate. The MFC30 detects the flow rate and pressure of the gas being drawn in using a flow sensor 30a and a pressure sensor 30b, and controls the opening and closing of the solenoid actuator valve 30d. This allows the flow rate of the gas flowing from the gas pipe 15 to be adjusted. Furthermore, in this embodiment, it is desirable that the MFC30 operates even if the difference between the pressure upstream of the MFC30 and the pressure downstream of the MFC30 is 0.1 MPa or less.

[0036] The gas that has passed through the vacuum pump 32 is sent to the gas purification unit 33. In the gas purification unit 33, helium gas is separated and purified from other gases. The purified helium gas is supplied to the gas mixer 35 for reuse, and is supplied again to the heating furnace 10 after being replenished with helium gas from the gas supply unit 34. This makes it possible to recycle expensive helium gas, and is particularly effective when the consumption of helium gas increases due to the enlargement of the glass base material 2.

[0037] The operation mode of the gas recovery mechanism 100 in the optical fiber manufacturing process will be explained using Figure 2. At the beginning of the fiber drawing process, there is no need to inject helium gas because no optical fibers to be produced are available. In other words, the heating furnace 10 does not need to be filled with helium gas at the start of fiber drawing. Helium gas injection begins between the start of fiber drawing and the start of drawing the optical fibers to be produced (STEP 1 and STEP 2). Once the heating furnace 10 is filled with helium gas, the gas recovery mechanism 100 is activated (STEP 3) to begin helium gas recovery. When the line drawing is complete, first the line drawing is finished, and then the supply of helium gas to the heating furnace 10 is stopped (STEP 4 and STEP 5). After that, the operation of the gas recovery mechanism 100 is stopped, and the recovery of helium gas from the heating furnace 10 is finished (STEP 6). By completing the line drawing process using the above procedure, helium can be recovered from the furnace even after the line drawing is finished. Note that while helium gas is not being supplied to the heating furnace 10, nitrogen gas or argon gas may be supplied to maintain the furnace pressure of the heating furnace 10.

[0038] The optical fiber manufacturing apparatus 1a in this embodiment may have multiple heating furnaces 10, as shown in Figure 3. In this case, only one vacuum pump 32 and one gas purification device 33 are needed for each of the multiple heating furnaces 10. This eliminates the need to provide a vacuum pump 32 and a gas purification device 33 for each heating furnace 10, thus reducing equipment costs.

[0039] While embodiments of this disclosure have been described above, it goes without saying that the technical scope of this disclosure should not be interpreted restrictively by the description of these embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications to the embodiments are possible within the scope of the invention described in the claims. The technical scope of this disclosure should be determined based on the scope of the invention described in the claims and the scope of its equivalents. [Explanation of Symbols]

[0040] 1: Optical fiber manufacturing equipment 2: Glass base material 3: Fiber optic 10:Heating furnace 11: Furnace body 12: Core tube 13: Heater 14: Gas intake port 15, 15a, 15b: Gas pipes 20: Valve 21: Filter 30: Mass Flow Controller (MFC) 30a: Flow sensor 30b: Pressure sensor 30c: Control Unit 30d: Solenoid actuator valve 31: Oxygen concentration meter 32: Vacuum pump 33: Gas purification equipment 34: Gas supply equipment 35: Gas mixer 100: Gas recovery mechanism

Claims

1. A heating furnace for heating the optical fiber preform and drawing the fiber, A gas suction port for drawing gas from the aforementioned heating furnace, A gas purification apparatus for purifying the gas drawn in from the gas intake port, A filter section is positioned between the gas suction port and the gas purification device. A mass flow controller is positioned between the filter unit and the gas purification apparatus. A vacuum pump is placed between the mass flow controller and the gas purification apparatus. Equipped with, The mass flow controller is a manufacturing apparatus for optical fibers, having a solenoid actuator valve.

2. The aforementioned filter unit has a configuration in which two or more filters are arranged in parallel. Valves are arranged on the upstream and downstream sides of each of the aforementioned filter sections. The apparatus for manufacturing optical fibers according to claim 1.

3. There are multiple heating furnaces, and one vacuum pump and one gas purification device are connected to the multiple heating furnaces. An apparatus for manufacturing optical fibers according to claim 1 or claim 2.

4. A heating furnace for heating the optical fiber preform and drawing the fiber, A gas suction port for drawing gas from the aforementioned heating furnace, A gas purification apparatus for purifying the gas drawn in from the gas intake port, A filter section is positioned between the gas suction port and the gas purification device. A mass flow controller is positioned between the filter unit and the gas purification apparatus. A vacuum pump is placed between the mass flow controller and the gas purification apparatus. Equipped with, The mass flow controller is a method for drawing optical fibers in an optical fiber manufacturing apparatus, which involves heating an optical fiber preform to draw the fiber, and the mass flow controller has a solenoid actuator valve. A method for manufacturing an optical fiber, comprising drawing a fiber while controlling the amount of gas drawn by the vacuum pump using the mass flow controller.

5. The line is drawn while keeping the difference between the pressure upstream of the mass flow controller and the pressure downstream of the mass flow controller to 0.1 MPa or less. The method for manufacturing an optical fiber according to claim 4.

6. The amount of gas drawn in is controlled so that the internal pressure of the heating furnace is within a predetermined pressure range. A method for manufacturing an optical fiber according to claim 4 or claim 5.

7. The oxygen concentration in the gas between the gas intake port and the gas purification device is measured, and the amount of gas drawn in is controlled based on the measurement result. A method for manufacturing an optical fiber according to claim 4 or claim 5.

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