JP2024078941A - Optical fiber manufacturing apparatus and method - Google Patents

Abstract

[Problem] To provide an optical fiber manufacturing apparatus capable of improving gas recovery efficiency by an inexpensive method. [Solution] The optical fiber manufacturing apparatus includes a heating furnace 10 for heating and drawing an optical fiber preform, a gas suction port 14 for drawing gas from the heating furnace, a gas purification device 33 for purifying the gas drawn from the gas suction port, a filter unit 21 arranged between the gas suction port and the gas purification device, a mass flow controller 30 arranged between the filter unit and the gas purification device, and a vacuum pump 32 arranged between the mass flow controller and the gas purification device. [Selected Figure] Figure 1

Description

This disclosure relates to an optical fiber manufacturing apparatus and manufacturing method.

In the optical fiber manufacturing device described in Patent Document 1, an example is disclosed in which helium gas used in a drawing furnace is recovered and reused.

International Publication No. WO 2004/250286

However, in conventional optical fiber manufacturing equipment, the gas is collected through a filter, and if the filter becomes clogged, the flow rate may change. Therefore, the present invention aims to improve the gas collection efficiency by using an inexpensive method when collecting gases such as helium used in the drawing furnace of an optical fiber manufacturing equipment.

The present disclosure aims to improve gas recovery efficiency through an inexpensive method.

An optical fiber manufacturing apparatus according to one aspect of the present disclosure includes:
a heating furnace for heating and drawing an optical fiber preform;
a gas suction port for suctioning gas from the heating furnace;
a gas purification device for purifying the gas sucked through 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;
Equipped with.

In addition, a method for producing an optical fiber according to an aspect of the present disclosure includes the steps of:
a heating furnace for heating and drawing an optical fiber preform;
a gas suction port for suctioning gas from the heating furnace;
a gas purification device for purifying the gas sucked through 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;
An optical fiber drawing method for heating and drawing an optical fiber preform in an optical fiber manufacturing apparatus comprising:
The amount of the gas sucked by the vacuum pump is controlled by the mass flow controller while drawing the line.

As a result of the above, gas recovery efficiency can be improved using an inexpensive method.

FIG. 1 is a diagram illustrating an example of an optical fiber manufacturing apparatus according to the present disclosure. FIG. 2 is a flow chart showing the operation of the optical fiber manufacturing apparatus of FIG. FIG. 3 is a diagram illustrating another example of an optical fiber manufacturing apparatus according to the present disclosure.

[Description of the 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 for heating and drawing an optical fiber preform;
a gas suction port for suctioning gas from the heating furnace;
a gas purification device for purifying the gas sucked through 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;
Equipped with.
According to this configuration, since the flow rate is controlled by the mass flow controller, the amount of gas sucked by the vacuum pump can be kept constant, and the gas recovery efficiency is improved using an inexpensive method.

(2) In the above (1), the mass flow controller may have a solenoid actuator valve.
According to this configuration, by adopting a mass flow controller having a solenoid actuator and reducing the delay in opening and closing the valve, the amount of gas suctioned by the vacuum pump can be kept constant, thereby improving the gas recovery efficiency.

(3) In the above (1) or (2), the filter section may be configured by arranging two or more filters in parallel, and valves may be arranged upstream and downstream of each of the filter sections.
According to this configuration, if the filter becomes clogged due to long-term use of the manufacturing equipment, a new filter can be used by switching the flow path, thereby reducing the cost of maintaining the manufacturing equipment.

(4) In any one of the above (1) to (3), the heating furnace may be provided in a plurality of furnaces, and one of the vacuum pumps and one of the gas purification devices may be connected to the plurality of heating furnaces.
According to this configuration, only one vacuum pump and one gas purification device are required to be connected to a plurality of heating furnaces, which reduces equipment costs.

(5) a heating furnace for heating and drawing the optical fiber preform;
a gas suction port for suctioning gas from the heating furnace;
a gas purification device for purifying the gas sucked through 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;
An optical fiber drawing method for heating and drawing an optical fiber preform in an optical fiber manufacturing apparatus comprising:
The optical fiber is drawn while controlling the amount of the gas suctioned by the vacuum pump with the mass flow controller.
According to this configuration, since the flow rate is controlled by the mass flow controller, the amount of gas sucked by the vacuum pump can be kept constant, and the gas recovery efficiency is improved using an inexpensive method.

(6) In the above (5), the line drawing may be performed while keeping the difference between the pressure on the upstream side of the mass flow controller and the pressure on the downstream side of the mass flow controller at 0.1 MPa or less.
According to this configuration, the gas flow rate can be controlled even if the difference in pressure between the upstream and downstream sides of the mass flow controller is 0.1 MPa or less, so that the amount of gas suctioned by the vacuum pump can be maintained constant, improving the gas recovery efficiency.

(7) In the above (5) or (6), the amount of gas suction may be controlled so that the internal pressure of the heating furnace is within a predetermined pressure range.
According to this configuration, the internal pressure can be prevented from becoming too negative, so that the air can be prevented from entering the furnace, and a decrease in the strength of the optical fiber being manufactured can be prevented.

(8) In any one of the above (5) to (7), the oxygen concentration in the gas between the gas suction port and the gas purification device may be measured, and the amount of the gas suctioned may be controlled based on the measurement result.
According to this configuration, the specific heat setting of the mass flow controller can be changed according to the oxygen concentration in the gas, so that the amount of gas sucked by the vacuum pump can be kept constant, improving the efficiency of gas recovery.

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

Figure 1 is a schematic diagram showing an example of an optical fiber manufacturing apparatus 1 according to an embodiment of the present disclosure. The optical fiber manufacturing apparatus 1 according to this embodiment is an optical fiber drawing apparatus that draws an optical fiber by sequentially heating and melting a glass preform while supplying helium gas around it, and is equipped with a helium gas recovery mechanism at the bottom of the heating furnace 10 to recover the helium gas.

In addition, the optical fiber drawing method according to an embodiment of the present disclosure is an optical fiber drawing method in which helium gas is supplied around a glass preform while it is successively heated and melted to draw an optical fiber, and is characterized in that the helium gas is recovered by a gas recovery mechanism disposed at the bottom of the heating furnace, and the recovered helium gas is purified and reused.

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

The heating furnace 10 includes a furnace core tube 12 arranged in the center of the furnace body 11, and a heater 13 arranged around the furnace core tube 12. A glass base material 2 for optical fiber is suspended and supported within the furnace core tube 12. The heater 13 heats the furnace core tube 12, and the glass base material 2 is heated by the heat of the heated furnace core tube. The lower part of the glass base material 2 is heated and melted in sequence, and the glass base material 2 is drawn so that optical fiber 3 is continuously obtained by the weight and tensile force of the molten glass. The drawn optical fiber 3 then undergoes a cooling process, a coating process, etc. (not shown), and is wound up on a drum or the like.

The gas supply device 34 supplies gas such as helium into the furnace core tube 12. The helium gas is introduced so as to uniformly fill the space between the furnace core tube 12 and the glass base material 2, and uniforms the temperature distribution in the space inside the furnace core tube 12. In particular, it suppresses the generation of turbulence due to temperature differences in the neck-down portion of the glass base material 2 where the space becomes larger, and prevents fluctuations in the diameter of the drawn optical fiber.

The gas that passes through gas pipes 15a and 15b merges at the downstream end and is then passed through MFC 30.

In the present disclosure, a gas suction port 14 is provided at the bottom of the furnace tube 12 (sometimes referred to as the lower chimney), and a gas recovery mechanism 100 is provided beyond the gas suction port 14. With this configuration, the helium gas supplied to the heating furnace 10 is recovered. The recovered helium gas is finally supplied again to the heating furnace 10 through the gas recovery mechanism 100.

As shown in FIG. 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 measuring device 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 suck gas from the heating furnace 10 through the gas suction port 14.

The filter 21 is made of a heat-resistant material such as ceramics or metal, and can remove solid matter contained in the sucked gas. In this embodiment, the downstream end of the gas pipe 15 is bifurcated in parallel, and two or more filters 21 are provided in each of the branched gas pipes 15a, 15b. For example, a coarse-mesh filter may be provided on the upstream side, and a fine-mesh filter on the downstream side. It is sufficient for the gas to pass through either the branched gas pipe 15a or the gas pipe 15b.

Valves 20 are provided on the upstream and downstream sides of the filters 21, so that when any of the filters 21 becomes clogged, gas can be prevented from flowing into the gas pipe 15 in which that filter is provided.
In addition, the valve 20 can be used to adjust whether the gas flows through the branched gas pipes 15a and 15b. 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.

In this embodiment, the MFC 30 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 MFC 30 is provided between the filter 21 and the gas purification device 33, and can adjust the flow rate of the gas sucked in by the vacuum pump 32.

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

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 refers to the oxygen concentration data received from the oxygen concentration meter 31 and controls the solenoid actuator valve 30d. In addition, the control unit 30c may refer to the oxygen concentration data received from the oxygen concentration meter 31 and modify the valve characteristics of the solenoid actuator valve 30d stored in the memory unit. 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.

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 suck gas from the heating furnace 10. The gas purification device 33 is a device that can separate the gas sucked from the heating furnace 10 into helium and gases other than helium. The gas purification device 33 may be configured to be able to separate gases other than helium 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.

Next, the operation of the gas recovery mechanism 100 will be described.
The gas is sucked by a vacuum pump 32. The vacuum pump 32 sucks the gas in 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 a pressure difference from the atmospheric pressure of 0 Pa or more and 20 Pa or less. This makes it possible to prevent the internal pressure of the heating furnace 10 from becoming negative and to prevent air from mixing into the heating furnace 10, thereby keeping the atmosphere in the heating furnace 10 clean and preventing a decrease in the strength of the optical fiber 3 being manufactured.

The gas in the heating furnace 10 is sucked in through the gas suction port 14 by the vacuum pump 32 and first passes through the filter 21 via the gas pipe 15.

The MFC 30 adjusts the gas flowing in from the gas pipe 15 to a predetermined flow rate. The MFC 30 detects the flow rate and pressure of the gas being sucked in using a flow sensor 30a and a pressure sensor 30b, and controls the opening and closing of the solenoid actuator valve 30d. This makes it possible to adjust the flow rate of the gas flowing in from the gas pipe 15. Furthermore, in this embodiment, it is desirable for the MFC 30 to operate even if the difference in pressure between the upstream side of the MFC 30 and the downstream side of the MFC 30 is 0.1 MPa or less.

The gas that has passed through the vacuum pump 32 is sent to the gas purification device 33. In the gas purification device 33, the helium gas is separated and purified from other gases. The purified helium gas is supplied to the gas mixer 35 for reuse, and is replenished with helium gas from the gas supply device 34 and supplied again to the heating furnace 10. This makes it possible to recycle expensive helium gas, which is particularly effective in cases where the consumption of helium gas increases due to the increase in size of the glass base material 2.

The operation of the gas recovery mechanism 100 in the optical fiber manufacturing process will be described with reference to FIG.
At the beginning of drawing, since no optical fiber to be a product is obtained, there is no need to inject helium gas. In other words, there is no need for the heating furnace 10 to be filled with helium gas at the start of drawing. Injection of helium gas is started after drawing starts and before drawing of the optical fiber to be a product begins (STEP 1 and STEP 2). When the heating furnace 10 is filled with helium gas, the gas recovery mechanism 100 is operated (STEP 3) to start recovering the helium gas.
When the fiber drawing is to be completed, first the fiber drawing is completed, and then the supply of helium gas to the heating furnace 10 is terminated (STEP 4 and STEP 5). After that, the operation of the gas recovery mechanism 100 is terminated, and the recovery of helium gas from the heating furnace 10 is terminated (STEP 6).
By completing the drawing process according to the above procedure, the helium in the furnace can be recovered even after the drawing process is completed. While helium gas is not being supplied to the heating furnace 10, nitrogen gas or argon gas may be supplied to maintain the pressure inside the heating furnace 10.

The optical fiber manufacturing apparatus 1a in this embodiment may have multiple heating furnaces 10 as shown in FIG. 3. In this case, one vacuum pump 32 and one gas purification device 33 may be provided for 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, thereby reducing equipment costs.

Although the embodiment of the present disclosure has been described above, it goes without saying that the technical scope of the present disclosure should not be interpreted as being limited by the description of the present embodiment. The present embodiment is merely an example, and it will be understood by those skilled in the art that various modifications of the embodiment are possible within the scope of the invention described in the claims. The technical scope of the present disclosure should be determined based on the scope of the invention described in the claims and its equivalents.

1: Optical fiber manufacturing device 2: Glass base material 3: Optical fiber 10: Heating furnace 11: Furnace body 12: Furnace tube 13: Heater 14: Gas suction port 15, 15a, 15b: Gas pipe 20: Valve 21: Filter 30: Mass flow controller (MFC)
30a: Flow rate sensor 30b: Pressure sensor 30c: Control unit 30d: Solenoid actuator valve 31: Oxygen concentration measuring device 32: Vacuum pump 33: Gas purification device 34: Gas supply device 35: Gas mixer 100: Gas recovery mechanism

Claims (8)

a heating furnace for heating and drawing an optical fiber preform;
a gas suction port for suctioning gas from the heating furnace;
a gas purification device for purifying the gas sucked through 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;
An optical fiber manufacturing apparatus comprising: The mass flow controller has a solenoid actuator valve.
2. An apparatus for producing an optical fiber according to claim 1. The 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 filter sections.
3. The optical fiber manufacturing apparatus according to claim 1 or 2. There are a plurality of the heating furnaces, and one of the vacuum pumps and one of the gas purification devices are connected to the plurality of the heating furnaces.
3. The optical fiber manufacturing apparatus according to claim 1 or 2. a heating furnace for heating and drawing an optical fiber preform;
a gas suction port for suctioning gas from the heating furnace;
a gas purification device for purifying the gas sucked through 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;
An optical fiber drawing method for heating and drawing an optical fiber preform in an optical fiber manufacturing apparatus comprising:
The optical fiber is drawn while controlling the amount of the gas suctioned by the vacuum pump with the mass flow controller. The line is drawn while keeping the difference between the pressure on the upstream side of the mass flow controller and the pressure on the downstream side of the mass flow controller at 0.1 MPa or less.
The method for producing an optical fiber according to claim 5 . controlling the amount of gas suction so that the internal pressure of the heating furnace is within a predetermined pressure range;
The method for producing an optical fiber according to claim 5 or 6. measuring an oxygen concentration in the gas between the gas suction port and the gas purification device, and controlling an amount of the gas suction based on the measurement result;
The method for producing an optical fiber according to claim 5 or 6.

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