JP7701804B2 - Glass member heating device, glass member heating method, and method for manufacturing optical fiber preform using same - Google Patents

Description

The present invention relates to a heating device for a glass member, a heating method for a glass member, and a manufacturing method for an optical fiber preform using the same.

A known method for producing optical fiber base material for use in the manufacture of optical fiber is to deposit glass particles using the OVD method (outside vapor deposition method) or the VAD method (vapor phase axial deposition method) to form a porous glass body, and then heat and sinter the porous glass body.

Patent Document 1 below discloses a heating device for heating a porous glass body. This heating device includes a core tube having a storage space for storing the porous glass body, a heater disposed outside the core tube, a furnace body surrounding a part of the core tube and the heater, and a gas detector. This gas detector detects leaking gas that leaks from the core tube into the space surrounded by the core tube and the furnace body and is discharged from an exhaust port provided in the furnace body. Therefore, it is said that this heating device can detect damage such as cracks in the core tube using the gas detector.

JP 2015-48262 A

The furnace body of the heating device described above is sometimes cooled by cooling water, and if the furnace body is damaged, the cooling water may enter the space enclosed by the core tube and the furnace body. Inert gas may also be supplied to this space to suppress the combustion of the components placed in the space, and water may enter this space along with the inert gas due to a malfunction of the gas supply device. The core tube is generally made of quartz or carbon, and in such an abnormal state where water has entered the above-mentioned space, water may penetrate from the space into the storage space of the core tube even if the core tube is not damaged. If water enters the storage space when the porous glass body is heated and sintered by the heater, the transmission loss, which is a characteristic of the optical fiber finally manufactured, may deteriorate.

The present invention aims to provide a heating device for glass members that can detect abnormal conditions caused by water, a heating method for glass members, and a manufacturing method for optical fiber preforms using the same.

To achieve the above object, the heating device for glass members of the present invention comprises a furnace tube having a storage space capable of storing at least a portion of a glass member, a furnace body surrounding at least a portion of the furnace tube, a heater disposed in the space surrounded by the furnace tube and the furnace body, and a gas measuring unit, wherein at least one of the members disposed in the space contains carbon, and the gas measuring unit is capable of measuring the concentration in the space of gas generated due to a reaction between water and carbon.

In order to achieve the above object, the present invention provides a method for heating a glass member, which comprises accommodating at least a portion of a glass member in an accommodation space in a furnace tube, at least a portion of which is surrounded by a furnace body, and heating the glass member with a heater disposed in the space surrounded by the furnace tube and the furnace body, wherein at least one of the members disposed in the space contains carbon, and the concentration of gas generated due to a reaction between water and carbon in the space is measured while the glass member is heated by the heater.

When dehydrating, sintering, melting, etc., glass members, the heater is generally heated to 700°C or higher. If water enters the above-mentioned space in such a high-temperature state, the water reacts with the carbon contained in the member placed in this space to generate gas. This glass member heating device and glass member heating method can measure the concentration of the gas thus generated, making it possible to detect an abnormal state in which water has entered the above-mentioned space.

The gas may be at least one of carbon monoxide, carbon dioxide, methane, and hydrogen.

The furnace body may have a flow path through which cooling water flows.

This configuration can prevent damage to the furnace body caused by heat. In addition, since the gas measurement unit can measure the concentration of gas generated in the above-mentioned space due to the reaction between water and carbon, damage to the furnace body such as cooling water entering the above-mentioned space can be detected.

The above-mentioned glass member heating device may further include a gas supply unit that supplies an inert gas to the space through an air supply port formed in the furnace body and communicating with the space.

This configuration makes it possible to suppress combustion of components placed in the above-mentioned space. In addition, since the gas measurement unit can measure the concentration in the above-mentioned space of gas generated due to the reaction between water and carbon, it is possible to detect malfunctions in the gas supply unit, piping, etc. that may cause water to enter the above-mentioned space together with the inert gas.

In the above-mentioned glass member heating device, the gas measuring unit may measure the concentration of the gas from exhaust gas exhausted from an exhaust port formed in the furnace body and communicating with the space.

By configuring in this way, it is possible to suppress the effect on the concentration of the gas due to the location where the gas is generated in the space, compared to when the concentration of the gas is measured at a certain point in the space. Therefore, compared to the above case, it is possible to accurately detect an abnormal state in which water has entered the space.

The above-mentioned glass member heating device further includes an abnormality determination unit that determines whether or not an abnormal state exists based on the change over time in the concentration of the gas measured by the gas measurement unit, and the abnormality determination unit may determine that an abnormal state exists when the difference between the concentration of the gas measured by the gas measurement unit and the average value of the concentration of the gas measured by the gas measurement unit before the timing at which the concentration of the gas is measured is equal to or greater than a predetermined value.

Even for furnaces of the same configuration, the concentrations of the above gases measured in a steady state tend to change depending on the installation state of the furnace. Therefore, by using the above configuration, it is possible to appropriately determine whether or not an abnormal state exists, compared to when an abnormal state is determined to exist when the gas concentration is equal to or greater than a predetermined value.

The above-mentioned glass member heating device may further include a fiber defect determination unit, the glass member being a porous glass body that becomes part of an optical fiber, and the fiber defect determination unit may determine whether the optical fiber is defective based on the change over time in the concentration of the gas measured by the gas measurement unit.

As described above, if water infiltrates into the storage space during sintering of the porous glass body, the characteristics of the optical fiber finally manufactured, such as transmission loss, may deteriorate, and the characteristics tend to deteriorate as the amount of water that infiltrates into the storage space increases. Such infiltration of water into the storage space may not affect the appearance of the transparent glass member formed by sintering the porous glass body. For this reason, it may be difficult to determine whether the characteristics of the optical fiber finally manufactured will deteriorate and the optical fiber will become defective based on the appearance of the transparent glass member. However, the more water that infiltrates into the storage space, the greater the amount of gas generated due to the reaction between water and carbon, and the higher the concentration of this gas. For this reason, by adopting the above-mentioned configuration, it is possible to determine whether the optical fiber finally manufactured will be defective at the stage of manufacturing the transparent glass member, thereby reducing the defective rate of the optical fiber and improving the productivity of the optical fiber.

In this case, the gas is carbon monoxide, the glass member is a porous glass body that serves as the core of the optical fiber, and the fiber defect determination unit may determine that the optical fiber is defective when the difference between the gas concentration measured by the gas measurement unit and the gas concentration in the initial state before the glass member is heated for the first time after the furnace body is installed exceeds 550 ppm.

The inventors have found that when the difference between the carbon monoxide concentration when the core porous glass body is heated and the carbon monoxide concentration in the initial state described above exceeds 550 ppm, the optical fiber manufactured from the optical fiber preform including the core glass body made of the porous glass body becomes defective. Therefore, by adopting such a configuration, it is possible to appropriately predict whether the optical fiber finally manufactured will be defective.

The method for manufacturing an optical fiber preform of the present invention is characterized by including a heating step in which a porous glass body as the glass member is heated by the above-mentioned glass member heating method.

As described above, the present invention provides a glass member heating device capable of detecting abnormal conditions caused by water, a glass member heating method, and a method for manufacturing an optical fiber preform using the same.

1 is a diagram illustrating a cross section perpendicular to the longitudinal direction of an optical fiber according to an embodiment of the present invention. 2 is a diagram illustrating a cross section perpendicular to the longitudinal direction of an optical fiber preform for manufacturing the optical fiber shown in FIG. 1. 1 is a flowchart showing steps of a method for manufacturing an optical fiber preform and a method for manufacturing an optical fiber according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a schematic diagram of a dehydration and sintering apparatus used in the first heating step. FIG. 1 is a diagram showing the relationship between each core glass rod in an experimental example, the respective concentrations of carbon monoxide and carbon dioxide measured during sintering, and the transmission loss of the manufactured optical fiber.

Below, the glass member heating device, glass member heating method, and optical fiber preform manufacturing method using the same according to the present invention are illustrated with the accompanying drawings. The embodiments illustrated below are intended to facilitate understanding of the present invention and are not intended to limit the interpretation of the present invention. The present invention can be modified and improved without departing from the spirit of the invention. Note that in the drawings referred to below, the dimensions of each component may be changed to facilitate understanding.

Figure 1 is a schematic diagram showing a cross section perpendicular to the longitudinal direction of an optical fiber according to an embodiment of the present invention. As shown in Figure 1, the optical fiber 1 of this embodiment mainly comprises a core 10, a cladding 11 surrounding the outer peripheral surface of the core 10, and a coating layer 12 that covers the outer peripheral surface of the cladding 11. The outer shape of the core 10 in the cross section is circular, and the core 10 is disposed at the center of the cladding 11. Note that the outer shape of the cladding 11 in the cross section may be non-circular, such as elliptical or polygonal. Figure 1 shows an optical fiber 1 in which the outer shape of the cladding 11 is circular.

The refractive index of the core 10 is made higher than that of the cladding 11. In this embodiment, the core 10 is made of silica glass doped with a dopant such as germanium (Ge) that increases the refractive index, and the cladding 11 is made of silica glass without any additives. The core 10 may be made of silica glass without any additives, and the cladding 11 may be made of silica glass doped with a dopant such as fluorine (F) that decreases the refractive index. The core 10 may be made of silica glass doped with a dopant that increases the refractive index, and the cladding 11 may be made of silica glass doped with a dopant that decreases the refractive index. The dopant that increases the refractive index and the dopant that decreases the refractive index are not particularly limited.

The coating layer 12 is made of a resin. Examples of resins that make up the coating layer 12 include thermosetting resins and ultraviolet-curing resins. The coating layer 12 may have a single-layer structure made of one resin layer that surrounds the cladding 11, or a multilayer structure made of multiple resin layers.

Figure 2 is a schematic diagram showing a cross section perpendicular to the longitudinal direction of the optical fiber preform for manufacturing the optical fiber 1 shown in Figure 1. As shown in Figure 2, the optical fiber preform 1P is composed of a rod-shaped core glass body 10P that becomes the core 10, and a cladding glass body 11P that surrounds the outer peripheral surface of the core glass body 10P and becomes the cladding 11. In this embodiment, the outer shape of the cladding glass body 11P in the cross section is circular, and the core glass body 10P is disposed at the center of the cladding glass body 11P. The outer shape of the core glass body 10P in the cross section is also circular.

Next, we will explain the manufacturing method for the optical fiber base material according to this embodiment.

Figure 3 is a flow chart showing the steps of the method for manufacturing the optical fiber preform 1P according to this embodiment. As shown in Figure 3, the method for manufacturing the optical fiber preform 1P according to this embodiment includes a first deposition process P1, a first heating process P2, a second deposition process P3, and a second heating process P4.

<First deposition step P1>
This step is a step of depositing glass particles to form a core porous glass body that will become the core glass body 10P shown in Fig. 2. The porous glass body can be formed by a soot method such as the OVD method or the VAD method. In this embodiment, the core porous glass body is formed by depositing glass particles from one end of a prepared glass rod along the axial direction of the glass rod by the VAD method.

<First heating step P2>
This process is a process for heating the core porous glass body as the glass member formed by the first depositing process P1, and includes a first dehydrating process P2a and a first sintering process P2b as shown in Fig. 3. First, a dehydrating and sintering device as a heating device for the glass member used in this process will be described.

Figure 4 is a schematic diagram of the dehydration-sintering apparatus used in the first heating step P2. As shown in Figure 4, the dehydration-sintering apparatus 100 of this embodiment mainly comprises a heating furnace 30, a lifting section 40, a first gas supply section 41, a second gas supply section 42, a gas measurement section 48, a judgment section 50, a memory 55, a notification section 56, and a control section 60.

The control unit 60 is composed of, for example, an integrated circuit such as a microcontroller, an integrated circuit (IC), a large-scale integrated circuit (LSI), or an application specific integrated circuit (ASIC), or an NC (Numerical Control) device. In addition, when an NC device is used, the control unit 60 may or may not use a machine learning device. As described below, some components of the dehydration and sintering apparatus 100 are controlled by the control unit 60.

In this embodiment, the heating furnace 30 mainly comprises a furnace core tube 31, a furnace body 35, a heater 37, and a heat insulating material 38.

The furnace core tube 31 of this embodiment is a cylindrical member extending in the vertical direction, and can accommodate the core porous glass body 20 in the accommodation space 31S. In this embodiment, the openings at both ends of the furnace core tube 31 are closed, and the part that closes the upper opening is removable from the other parts. A through hole is formed in the part that closes the upper opening of the furnace core tube 31, into which a support rod 22 for suspending the core porous glass body 20 is inserted. A connection part 23 is provided at the lower end of the support rod 22, and a glass rod 24 on which the core porous glass body 20 is deposited is connected to this connection part 23. The furnace core tube 31 is formed with an exhaust port E1 and an air supply port S1 that each communicate with the accommodation space 31S. Examples of materials that constitute the furnace core tube 31 include quartz and carbon.

The furnace body 35 of this embodiment is formed in a hollow box shape, and has a flow path 36 in the outer wall of the furnace body 35 through which cooling water supplied from a cooling water supply unit (not shown) flows. The flow of cooling water through the flow path 36 cools the furnace body 35, suppressing damage to the furnace body 35 due to heat. In addition, a through hole penetrating in the vertical direction is formed in the center of the furnace body 35, and the furnace core tube 31 is inserted into the through hole. The upper and lower ends of the furnace core tube 31 protrude from the furnace body 35, and the furnace body 35 surrounds the center of the furnace core tube 31 in the vertical direction, forming a space 35S surrounded by the furnace core tube 31 and the furnace body 35. In addition, the furnace body 35 is formed with an air inlet S2 and an exhaust port E2 that communicate with this space 35S. The air inlet S2 is located on one side in the horizontal direction based on the furnace core tube 31, and the exhaust port E2 is located on the other side. Examples of materials that constitute the furnace body 35 include metal.

The heater 37 is arranged in the space 35S so that it can heat the core porous glass body 20 housed in the accommodation space 31S of the furnace core tube 31 by generating heat. The heater 37 in this embodiment is made of carbon and is formed in a ring shape surrounding the furnace core tube 31, but the heater 37 may be divided into multiple heating parts and these multiple heating parts may be discontinuously arranged to surround the furnace core tube 31. The heater 37 adjusts the heat generation temperature by a control signal from the control unit 60. In order to effectively utilize the heat generated by the heater 37, a heat insulating material 38 is arranged between the heater 37 and the furnace body 35 in the space 35S. The number of heat insulating materials 38 is not particularly limited, and the heat insulating material 38 may be divided into multiple parts. The heat insulating material 38 in this embodiment is made of carbon. For this reason, in this embodiment, the heater 37 and the heat insulating material 38, which are members arranged in the space 35S, contain carbon. Note that at least one of the components placed in the space 35S needs to contain carbon; for example, one of the heater 37 and the heat insulating material 38 may be made of silicon carbide, and the heating furnace 30 does not need to be equipped with the heat insulating material 38.

The lifting unit 40 raises and lowers the support rod 22 that it holds. The lifting unit 40 raises and lowers the support rod 22 in response to a control signal from the control unit 60, thereby moving the core porous glass body 20 attached to the support rod 22 up and down. The configuration of the lifting unit 40 is not particularly limited.

The first gas supply unit 41 supplies a first gas, including a dehydration gas, to the accommodation space 31S through a pipe 43 connected to the gas inlet S1 of the furnace core tube 31. The first gas supply unit 41 adjusts the supply amount of the first gas according to a control signal from the control unit 60. The first gas supplied to the accommodation space 31S is exhausted from the exhaust port E1 of the furnace core tube 31 to the exhaust pipe 44. In this embodiment, the first gas is a mixed gas of a dehydration gas and an inert gas, and examples of the dehydration gas include chlorine-based gases such as chlorine, SiCl ₄ , thionyl chloride (SOCl ₂ ), and carbon tetrachloride (CCl ₄ ), and carbon monoxide, and examples of the inert gas include He, Ar, and N ₂ .

The second gas supply unit 42 supplies a second gas, which is an inert gas, to the space 35S via a pipe 45 connected to the gas inlet S2 of the furnace body 35. The second gas supply unit 42 adjusts the supply amount of the second gas according to a control signal from the control unit 60. The second gas supplied to the space 35S is exhausted from the exhaust port E2 of the furnace body 35 to the exhaust pipe 46. Examples of the second gas include He, Ar, and _N2 .

In this embodiment, the gas measuring unit 48 is attached to the exhaust pipe 46, measures the concentration of a predetermined gas in the exhaust gas exhausted from the exhaust port E2, and outputs a signal indicating the measured concentration of the predetermined gas to the judgment unit 50. The gas measuring unit 48 repeats this measurement and output intermittently or continuously. The predetermined gas is a gas generated due to a reaction between water and carbon. As described above, at least one of the members arranged in the space 35S contains carbon. Therefore, when water enters the space 35S at a temperature at which water and carbon react, for example, at a temperature of 700°C or higher, the water reacts with the carbon contained in the member arranged in the space 35S to generate a predetermined gas. Note that in a high-temperature state at which water and carbon react, water is decomposed into hydrogen atoms and oxygen atoms, and the hydrogen atoms and oxygen atoms react with carbon. Examples of the predetermined gas include carbon monoxide, carbon dioxide, methane, oxygen, and hydrogen, and the gas measuring unit 48 is configured to be able to measure the concentration of at least one of these. For example, a constant potential electrolysis sensor is used to measure the concentration of carbon monoxide, a non-dispersive infrared sensor is used to measure the concentration of carbon dioxide, a semiconductor laser absorption spectroscopy sensor is used to measure the concentration of methane or hydrogen, and a zirconia concentration cell sensor is used to measure the concentration of oxygen. The gas measurement unit 48 of this embodiment is capable of measuring the concentration of carbon monoxide. Note that the gas measurement unit 48 may be attached to the furnace body 35, for example, as long as it is capable of measuring the concentration of the above-mentioned specified gas in the space 35S.

The determination unit 50 of this embodiment stores the concentration of the specified gas measured by the gas measurement unit 48 in the memory 55, and determines whether the dehydration and sintering device 100 is in an abnormal state and whether the optical fiber to be manufactured will be defective based on the change over time in the concentration of the specified gas. The determination unit 50 may have a configuration similar to that of the control unit 60, for example.

The memory 55 is, for example, a non-transitory recording medium, and is preferably a semiconductor recording medium such as a random access memory (RAM) or a read only memory (ROM), but may include any type of recording medium such as an optical recording medium or a magnetic recording medium. In this embodiment, the memory 55 stores programs and information for executing these determination processes. The determination unit 50 reads the programs and information from the memory 55, and in this state, the determination unit 50, which is equipped with an abnormality determination unit 51 and a fiber failure determination unit 52, executes the above-mentioned determination processes.

The abnormality determination unit 51 determines whether the dehydration and sintering apparatus 100 is in an abnormal state based on the change over time in the concentration of the specified gas measured by the gas measurement unit 48. The inventor has found that, as described below, when the difference between the concentration of the specified gas measured by the gas measurement unit 48 and the average concentration of the specified gas measured by the gas measurement unit 48 before the timing at which the concentration of the specified gas is measured is equal to or greater than a first predetermined value, an abnormal state in which water has entered the space 35S is present. This is thought to be because the water enters the space 35S, and the reaction between the water and carbon generates a specified gas, causing the concentration of the specified gas to increase. For this reason, the abnormality determination unit 51 of this embodiment outputs a signal indicating an abnormal state to the notification unit 56 via the control unit 60 when the difference between the concentration of the specified gas measured by the gas measurement unit 48 and the average concentration of the specified gas measured by the gas measurement unit 48 before the timing at which the concentration of the specified gas is measured is equal to or greater than a first predetermined value. On the other hand, when the difference is less than the first predetermined value, the abnormality judgment unit 51 does not output a signal to the control unit 60, but may output a signal indicating that there is no abnormal state to the notification unit 56 via the control unit 60. Therefore, the judgment of the abnormality judgment unit 51 means changing the signal to be output according to the signal from the gas measurement unit 48. The first predetermined value can be set in advance by experiment, etc., and for example, the first predetermined value is set to 500 ppm when the specified gas is carbon monoxide, and the first predetermined value is set to 450 ppm when the specified gas is carbon dioxide. The abnormality judgment unit 51 may also output a signal directly to the notification unit 56.

The fiber defect judgment unit 52 judges whether an optical fiber manufactured from an optical fiber preform including a member made of the porous glass body will be defective based on the change over time in the concentration of a predetermined gas measured by the gas measurement unit 48 while the porous glass body that will become a part of the optical fiber is being heated. As described below, the inventor has found that an optical fiber manufactured from an optical fiber preform including a glass member made of the porous glass body will be defective when the difference between the concentration of the predetermined gas when the porous glass body is being heated and the concentration of the predetermined gas in the initial state exceeds a second predetermined value. If the amount of water that invades the space 35S increases, the amount of water that penetrates the furnace core tube 31 and enters the storage space 31S also increases, and the characteristics of the manufactured optical fiber, such as transmission loss, deteriorate. And, it has been found that if the difference exceeds the second predetermined value, the optical fiber will no longer satisfy the characteristics generally required for long-distance transmission. The initial state is the state before the core porous glass body 20 is heated for the first time after the furnace body 35 is installed. The second predetermined value can be set in advance by experiment or the like. For example, when the predetermined gas is carbon monoxide and the porous glass body is the core porous glass body 20 that becomes the core 10 of the optical fiber 1, the second predetermined value is 550 ppm. In this embodiment, the fiber defect determination unit 52 outputs a signal indicating that the optical fiber 1 will be defective to the control unit 60 when the difference between the carbon monoxide concentration and the carbon monoxide concentration in the initial state exceeds 550 ppm. On the other hand, when this difference is less than 550 ppm, the fiber defect determination unit 52 does not output a signal to the control unit 60, but may output a signal indicating that the optical fiber 1 will not be defective to the control unit 60. Therefore, the determination of the fiber defect determination unit 52 is to change the signal to be output in response to the signal from the gas measurement unit 48. Also, the fiber defect determination unit 52 may output a signal directly to the notification unit 56.

The notification unit 56 in this embodiment issues a notification based on a signal from the abnormality determination unit 51 and a signal from the fiber defect determination unit 52. The notification unit 56 may, for example, be configured to have at least one of a display and a speaker.

Next, we will explain the first dehydration process P2a and the first sintering process P2b of the first heating process P2.

<First dehydration step P2a>
This step is a step of heating the core porous glass body 20 using the dehydration sintering apparatus 100 to dehydrate the core porous glass body 20. In this step, first, as shown in FIG. 4, the core porous glass body 20 suspended from the support rod 22 is accommodated in the accommodation space 31S of the furnace core tube 31. The first gas supply unit 41 supplies the first gas to the accommodation space 31S in response to a control signal from the control unit 60, fills the accommodation space 31S with the first gas, and exhausts the gas in the accommodation space 31S from the exhaust pipe 44. The second gas supply unit 42 supplies the second gas to the space 35S in response to a control signal from the control unit 60, fills the space 35S with the second gas, and exhausts the gas in the space 35S from the exhaust pipe 46. This makes it possible to suppress the heater 37, the heat insulating material 38, and the like in the space 35S from burning.

The heater 37 generates heat in response to a control signal from the control unit 60 while the first gas supply unit 41 and the second gas supply unit 42 are supplying gas in this manner. While the heater 37 is generating heat, the lifting unit 40 moves the core porous glass body 20 at a predetermined speed in response to a control signal from the control unit 60 so that the entire core porous glass body 20 crosses the heater 37. Therefore, the core porous glass body 20 is heated to a predetermined temperature by the heater 37. This heating removes the OH groups and attached moisture of the core porous glass body 20 by the dehydration gas contained in the first gas. The heating temperature may be lower than the sintering temperature of the core porous glass body 20 and may be a temperature at which moisture can be removed from the core porous glass body 20, and is preferably, for example, 1100°C to 1400°C. A heating temperature of 1100°C or higher promotes the diffusion of gas into the core porous glass body 20, and a heating temperature of 1400°C or lower sufficiently prevents the core porous glass body 20 from softening.

When the core porous glass body 20 is being heated by the heater 37 in this manner, the gas measuring unit 48 measures the carbon monoxide concentration at a predetermined time interval, for example, at one-minute intervals, and outputs a signal indicating the measured carbon monoxide concentration to the judgment unit 50. In other words, in this process, the core porous glass body 20 is heated by the heater 37 while the gas measuring unit 48 measures the carbon monoxide concentration, and the core porous glass body 20 is heated by this heating method.

When the difference between the concentration of carbon monoxide as a predetermined gas measured by the gas measuring unit 48 and the average value of the concentration of carbon monoxide measured by the gas measuring unit 48 before the timing of measuring the concentration of carbon monoxide is equal to or greater than a first predetermined value, the abnormality determination unit 51 outputs a signal indicating an abnormal state to the notification unit 56, and the notification unit 56 issues a notification based on the signal from the abnormality determination unit 51. Therefore, the operator can recognize the abnormal state by the notification from the notification unit 56. Furthermore, when the difference between the concentration of carbon monoxide measured by the gas measuring unit 48 and the concentration of carbon monoxide previously measured by the gas measuring unit 48 in the above-mentioned initial state exceeds 550 ppm, the fiber defect determination unit 52 outputs a signal indicating that the optical fiber will be defective to the control unit 60, and the notification unit 56 issues a notification based on the signal from the fiber defect determination unit 52. Therefore, the operator can determine that the optical fiber to be manufactured will be defective by the notification from the notification unit 56.

<First sintering process P2b>
This step is a step of heating the core porous glass body 20 using the dehydration and sintering apparatus 100 used in the first dehydration step P2a after the first dehydration step P2a to sinter the core porous glass body 20. As in the first dehydration step P2a, the first gas supply unit 41 supplies the first gas to the accommodation space 31S, and the second gas supply unit 42 supplies the second gas to the space 35S. The heater 37 generates heat while the first gas supply unit 41 and the second gas supply unit 42 are supplying gases. While the heater 37 is generating heat, the lifting unit 40 moves the core porous glass body 20 at a predetermined speed so that the entire core porous glass body 20 crosses the heater 37. Therefore, the core porous glass body 20 is heated to a predetermined temperature by the heater 37, and the core porous glass body 20 is sintered by the heating. The heating temperature may be any temperature at which the core porous glass body 20 is sintered to become transparent glass, and is preferably, for example, 1300° C. or higher and 1650° C. or lower.

The gas measuring unit 48 measures the carbon monoxide concentration, for example, at one-minute intervals, as in the first dehydration process P2a, and outputs a signal indicating the measured carbon monoxide concentration to the judgment unit 50. Therefore, in this process, as in the first dehydration process P2a, the core porous glass body 20 is heated by the heater 37 while the gas measuring unit 48 measures the carbon monoxide concentration, and the core porous glass body 20 is heated by such a heating method. Then, as in the first dehydration process P2a, the notification unit 56 issues a notification based on the signals from the abnormality judgment unit 51 and the fiber defect judgment unit 52. In this process, the core porous glass body 20 is transparently vitrified to become a core glass rod that becomes the core glass body 10P shown in FIG. 2, and the core glass rod is obtained from the glass rod 24 by cutting or the like.

<Second deposition step P3>
This step is a step of depositing glass particles on the outer surface of the core glass rod formed in the first sintering step P2b to form a cladding porous glass body which will become the cladding glass body 11P shown in Fig. 2. In this embodiment, the cladding porous glass body is formed by depositing glass particles on the outer peripheral surface of the core glass rod by the OVD method, but the method of forming the cladding porous glass body is not particularly limited.

<Second heating step P4>
This step is a step of heating the cladding porous glass body formed by the second deposition step P3, and includes a second dehydration step P4a and a second sintering step P4b as shown in Fig. 3. In this embodiment, these steps are performed using another dehydration and sintering device 100 having the same configuration as the dehydration and sintering device 100 used in the first heating step P2, but the dehydration and sintering device 100 used in the first heating step P2 may also be used.

<Second dehydration step P4a>
This step is a step of heating the cladding porous glass body using the dehydration and sintering apparatus 100 to dehydrate the cladding porous glass body. This step differs from the first dehydration step P2a mainly in that the core glass rod on which the cladding porous glass body is formed is accommodated in the accommodation space 31S of the furnace core tube 31. For this reason, a detailed description of this step is omitted, but in this step, the cladding porous glass body is heated by the heater 37 to dehydrate the cladding porous glass body, while the gas measurement unit 48 measures the concentration of carbon monoxide. In this step, the fiber defect determination unit 52 does not determine whether the optical fiber becomes defective, and the notification unit 56 issues a notification based on a signal from the abnormality determination unit 51.

<Second sintering process P4b>
This step is a step of heating the cladding porous glass body using the dehydration and sintering apparatus 100 used in the second dehydration step P4a after the second dehydration step P4a to sinter the cladding porous glass body. This step differs from the first dehydration step P2a mainly in that the core glass rod formed with the cladding porous glass body dehydrated by the second dehydration step P4a is accommodated in the accommodation space 31S of the furnace core tube 31. For this reason, a detailed description of this step is omitted, but in this step, the cladding porous glass body is heated by the heater 37 to sinter the cladding porous glass body, while the gas measuring unit 48 measures the concentration of carbon monoxide. In this step, the fiber defect determining unit 52 does not determine whether the optical fiber becomes defective, and the notifying unit 56 notifies based on a signal from the abnormality determining unit 51.

In this process, the core glass rod remains almost unchanged and becomes the core glass body 10P shown in Figure 2. The cladding porous glass body is vitrified into a transparent glass to become the cladding glass body 11P. In this way, the optical fiber preform 1P shown in Figure 2 is obtained.

The optical fiber preform 1P thus obtained is heated in a spinning furnace and drawn, so that the core glass body 10P becomes the core 10 and the clad glass body 11P becomes the clad 11, resulting in a bare optical fiber composed of the core 10 and the clad 11. The bare optical fiber is then coated with a resin that becomes the coating layer 12, forming the coating layer 12, and the optical fiber 1 shown in FIG. 1 is manufactured.

As described above, the dehydration and sintering apparatus 100 as a heating device for glass members in this embodiment includes the core tube 31, the furnace body 35, the heater 37, and the gas measuring unit 48. The core tube 31 has a storage space 31S capable of storing the entire core porous glass body 20 as a glass member. The furnace body 35 surrounds at least a portion of the core tube 31, and the heater 37 is disposed in the space 35S surrounded by the core tube 31 and the furnace body 35. At least one of the members disposed in this space 35S contains carbon. The gas measuring unit 48 can measure the concentration in the space 35S of a specific gas generated due to the reaction between water and carbon.

The method of heating the core porous glass body 20 and the cladding porous glass body as glass members in this embodiment involves heating these glass members with a heater 37 placed in a space 35S surrounded by the furnace tube 31 and the furnace body 35. At least one of the members placed in this space 35S contains carbon. Then, while heating these glass members with the heater 37, the concentration of a specific gas generated due to the reaction between water and carbon in the space 35S is measured.

When dehydrating, sintering, melting, etc., glass members, the heater is generally heated to 700°C or higher. In such a high-temperature state, if water enters the space 35S enclosed by the furnace tube 31 and the furnace body 35, the water reacts with the carbon contained in the members placed in this space to generate gas. The dehydration and sintering apparatus 100 and the glass member heating method of this embodiment can measure the concentration of the gas thus generated, making it possible to detect an abnormal state in which water has entered the space 35S.

In addition, in the dehydration and sintering apparatus 100 and the method for heating a glass member of this embodiment, the furnace body 35 has a flow path 36 through which cooling water flows, so damage to the furnace body 35 due to heat can be suppressed. In addition, the gas measurement unit 48 can measure the concentration of gas generated due to the reaction between water and carbon in the above-mentioned space 35S, so damage to the furnace body 35 such as cooling water entering the above-mentioned space 35S can be detected.

The dehydration and sintering apparatus 100 of this embodiment further includes a second gas supply unit 42 that supplies inert gas to the space 35S from an air supply port S2 formed in the furnace body 35 and communicating with the space 35S. This makes it possible to suppress combustion of the heater 37, the heat insulating material 38, and other components disposed in the space 35S. In addition, since the gas measuring unit 48 can measure the concentration of gas generated due to the reaction between water and carbon in the space 35S, it is possible to detect malfunctions of the second gas supply unit 42 or the piping 45 connected to the second gas supply unit 42 that may cause water to enter the space 35S together with the inert gas.

In addition, in the dehydration and sintering apparatus 100 and the method for heating a glass member of this embodiment, the concentration of a specific gas is measured from the exhaust gas exhausted from the exhaust port E2 formed in the furnace body 35 and communicating with the space 35S. Therefore, compared to measuring the concentration of a specific gas at a certain point in the space 35S, it is possible to suppress the influence on the concentration of the specific gas due to the location where the specific gas is generated in the space 35S. Therefore, compared to the above case, it is possible to accurately detect an abnormal state in which water has entered the space 35S.

The dehydration and sintering apparatus 100 of this embodiment further includes an abnormality determination unit 51 that determines whether or not an abnormal state exists based on the change over time in the concentration of a specific gas measured by the gas measurement unit 48. The abnormality determination unit 51 determines whether or not an abnormal state exists when the difference between the concentration of the specific gas measured by the gas measurement unit 48 and the average concentration of the specific gas measured by the gas measurement unit 48 before the timing at which the concentration of the specific gas is measured is equal to or greater than a first predetermined value. Even for furnace bodies 35 with the same configuration, the concentration of the specific gas measured in a steady state tends to change depending on the installation state of the furnace body 35. Therefore, by using the above configuration, it is possible to appropriately determine whether or not an abnormal state exists, compared to when an abnormal state is determined to exist when the gas concentration is equal to or greater than a predetermined value.

The dehydration and sintering apparatus 100 of this embodiment further includes a fiber defect determination unit 52, which heats the core porous glass body 20, which is a porous glass body that becomes part of the optical fiber 1. This fiber defect determination unit 52 determines whether the optical fiber 1 will become defective based on the change over time in the concentration of a specific gas measured by the gas measurement unit 48 while the core porous glass body 20 is being heated.

If water infiltrates into the storage space 31S during sintering of the core porous glass body 20, the transmission loss and other characteristics of the optical fiber 1 that is finally manufactured may deteriorate, and the more water that infiltrates into the storage space 31S, the more the characteristics tend to deteriorate. Such infiltration of water into the storage space 31S may not affect the appearance of the transparent glass member formed by sintering the core porous glass body 20. For this reason, it may be difficult to determine whether the characteristics of the optical fiber 1 that is finally manufactured will deteriorate and the optical fiber 1 will become defective based on the appearance of the transparent glass member. However, the more water that infiltrates into the storage space 31S, the more gas will be generated due to the reaction between water and carbon, and the higher the concentration of the gas. For this reason, by adopting the above-mentioned configuration, it is possible to determine whether the optical fiber 1 that is finally manufactured will be defective at the stage of manufacturing the transparent glass member, thereby reducing the defective rate of the optical fiber 1 and improving the productivity of the optical fiber 1.

In this embodiment, the specified gas is carbon monoxide, and the fiber defect determination unit 52 determines that the optical fiber 1 is defective when the difference between the carbon monoxide concentration measured by the gas measurement unit 48 while the core porous glass body 20 that becomes the core 10 of the optical fiber 1 is being heated and the carbon monoxide concentration in the initial state exceeds 550 ppm. As described above, the inventor has found that when this difference exceeds 550 ppm, the optical fiber 1 manufactured from the optical fiber preform 1P including the core glass body 10P made of the core porous glass body 20 will be defective. Therefore, by adopting such a configuration, it is possible to appropriately determine whether the optical fiber 1 finally manufactured will be defective.

Although the present invention has been described above using the above embodiments as examples, the present invention is not limited to these.

For example, in the above embodiment, the dehydration and sintering device 100 is described as having an abnormality determination unit 51 and a fiber defect determination unit 52. However, the dehydration and sintering device 100 does not have to have at least one of the abnormality determination unit 51 and the fiber defect determination unit 52. In this case, for example, an operator may determine whether or not there is an abnormal state or whether or not the optical fiber 1 will become defective based on the change over time in the concentration of a specified gas measured by the gas measurement unit 48.

In the above embodiment, the abnormality determination unit 51 is described as determining that an abnormal state exists when the difference between the concentration of the specified gas measured by the gas measurement unit 48 and the average value of the concentration of the specified gas measured by the gas measurement unit 48 before the timing of measuring the concentration of the specified gas is equal to or greater than a first predetermined value. However, the abnormality determination unit 51 may determine whether or not an abnormal state exists based on the change over time in the concentration of the specified gas measured by the gas measurement unit 48. For example, the abnormality determination unit 51 may output a signal indicating that an abnormal state exists when the concentration of the specified gas becomes equal to or greater than a predetermined threshold. This predetermined threshold is, for example, 700 ppm when the specified gas is carbon monoxide, and 800 ppm when the specified gas is carbon dioxide. However, from the viewpoint of appropriately determining whether or not an abnormal state exists, it is preferable that the abnormality determination unit 51 determines whether or not an abnormal state exists as in this embodiment. The abnormality determination unit 51 may also determine that an abnormal state exists based on the difference between the concentration of the predetermined gas and the median concentration of the predetermined gas before the timing at which the concentration of the predetermined gas is measured, the difference between the concentration of the predetermined gas and the average value of the concentration of the predetermined gas before the timing at which the concentration of the predetermined gas is measured minus the standard deviation, or the difference between the concentration of the predetermined gas and the minimum value of the concentration of the predetermined gas before the timing at which the concentration of the predetermined gas is measured. In this case, the abnormality determination unit 51 determines that an abnormal state exists when these differences are equal to or greater than a predetermined value, and this predetermined value is set for each difference based on experiments or the like. Also, a state in which the optical fiber 1 becomes defective is an abnormal state. For this reason, the abnormality determination unit 51 may determine that an abnormal state exists when the difference between the concentration of carbon monoxide measured by the gas measurement unit 48 while the glass member is being heated and the concentration of carbon monoxide in the initial state exceeds 550 ppm, for example, similar to the fiber defect determination unit 52 in the above embodiment.

In the above embodiment, the fiber defect judgment unit 52 judges that the optical fiber 1 will be defective when the difference between the concentration of carbon monoxide measured by the gas measurement unit 48 while the core porous glass body 20 is being heated and the concentration of carbon monoxide in the initial state exceeds 400 ppm. However, the fiber defect judgment unit 52 may judge whether or not an abnormal state exists based on the change over time in the concentration of a predetermined gas measured by the gas measurement unit 48. For example, the fiber defect judgment unit 52 may output a signal indicating that the optical fiber 1 will be defective when the concentration of the predetermined gas is equal to or greater than a predetermined threshold. This predetermined threshold is, for example, 700 ppm when the predetermined gas is carbon monoxide, and 800 ppm when the predetermined gas is carbon dioxide. In the above embodiment, the fiber defect judgment unit 52 judges whether or not the optical fiber 1 will be defective based on the change over time in the concentration of the predetermined gas measured in the first heating step P2. Here, if water infiltrates into the storage space 31S during sintering of the porous glass body for cladding that will become the cladding 11 of the optical fiber 1, the transmission loss, which is a characteristic of the optical fiber 1 that is finally manufactured, may deteriorate, and the greater the amount of water that infiltrates into the storage space 31S, the greater the tendency for the transmission loss to deteriorate. For this reason, the fiber defect determination unit 52 may determine whether the optical fiber 1 will become defective based on the change over time in the concentration of the specified gas measured in the second heating step P4. In this case, a threshold value for the concentration of the specified gas for determining whether the optical fiber 1 will become defective is set based on experimental values, etc.

In the above embodiment, the furnace body 35 is described as surrounding a portion of the furnace core tube 31. However, the furnace body 35 only needs to surround at least a portion of the furnace core tube 31, and may, for example, surround the entire furnace core tube 31.

In the above embodiment, the dehydration and sintering apparatus 100 including the second gas supply unit 42 has been described as an example. However, the dehydration and sintering apparatus 100 does not need to include the second gas supply unit 42. For example, instead of the second gas supply unit 42, the dehydration and sintering apparatus 100 may include an exhaust unit that exhausts the air in the space 35S from the exhaust pipe 46 to create a vacuum state in the space 35S. By creating a vacuum state in the space 35S in this way, it is possible to suppress the heater 37, the insulation material 38, etc. in the space 35S from burning.

In the above embodiment, the first deposition process P1 is used as an example to form the core porous glass body 20 that will become the core glass body 10P. However, the porous glass body formed in the first deposition process P1 is not particularly limited, and may be, for example, a porous glass body that will become part of the core glass body 10P and the clad glass body 11P. In this case, in the second deposition process P3, glass particles are deposited on the outer surface of the glass rod formed in the first sintering process P2b to form a porous glass body that will become the other part of the clad glass body 11P.

In the above embodiment, the manufacturing method of the optical fiber preform 1P including the first deposition step P1, the first heating step P2, the second deposition step P3, and the second heating step P4 has been described as an example. However, the manufacturing method of the optical fiber preform 1P only needs to include a heating step of heating the porous glass body as the glass member by the above-mentioned glass member heating method. For example, the manufacturing method of the optical fiber preform 1P does not need to include the first deposition step P1 and the first heating step P2. In this case, for example, in the second deposition step P3, first, a core glass rod is prepared by purchase or the like, and glass particles are deposited on the outer peripheral surface of the core glass rod to form a porous glass body for cladding.

In the above embodiment, the first sintering process P2b and the second sintering process P4b are described as an example in which the first gas is a mixed gas of a dehydration gas and an inert gas, and the porous glass body is heated while the first gas is supplied from the first gas supply unit 41 to the storage space 31S. However, in the first sintering process P2b and the second sintering process P4b, the porous glass body may be heated while only an inert gas is supplied to the storage space 31S. In this case, for example, the configuration of the first gas supply unit 41 is configured so that the first gas to be supplied can be changed between a gas containing a dehydration gas and an inert gas and only an inert gas. The control unit 60 controls the first gas supply unit 41 so that the first gas supplied from the first gas supply unit 41 is switched depending on the process.

In the above embodiment, the core porous glass body 20 is heated by the same dehydration and sintering device 100 in the first dehydration step P2a and the first sintering step P2b, and the cladding porous glass body is heated by the same dehydration and sintering device 100 in the second dehydration step P4a and the second sintering step P4b. However, for example, the porous glass body may be heated by a different dehydration and sintering device 100 in each step. The manufacturing method for the optical fiber preform 1P may further include a drawing step of drawing the glass body in which the core porous glass body 20 is sintered by the first heating step P2 to obtain a core glass rod. The furnace tube 31 may have a storage space 31S that stores at least a part of the glass member, and openings may be formed at both ends of the furnace tube 31. For example, the above-mentioned device for drawing the glass body, the spinning furnace for heating the optical fiber preform 1P, and the tip processing furnace are also included in the heating device for the glass member of the present invention.

The present invention will be described in more detail below with reference to experimental examples, but the present invention is not limited to these.

Using the dehydration and sintering apparatus 100 shown in FIG. 4, the first deposition step P1 and the first heating step P2 shown in FIG. 3 were repeated 32 times to produce 32 core glass rods. In this dehydration and sintering apparatus 100, the heater 37 was not heated from the installation of the furnace body 35 to the production of the first core glass rod. In addition, the concentrations of carbon monoxide and carbon dioxide in each space 35S in the initial state before the first heating step P2 for producing the first core glass rod after the installation of the furnace body 35 were measured by the gas measurement unit 48. The carbon monoxide concentration in the initial state was 150 ppm, and the carbon dioxide concentration was 260 ppm. In addition, the concentrations of carbon monoxide and carbon dioxide in each space 35S during the first heating step P2 when producing each core glass rod were measured by the gas measurement unit 48. The measurement results are shown in FIG. 5. Note that FIG. 5 also shows the transmission loss, which will be described later.

Furthermore, by performing the second deposition process P3 and the second heating process P4 shown in FIG. 3 using another dehydration and sintering apparatus 100, optical fiber preforms 1P similar to the optical fiber preform 1P shown in FIG. 2 were manufactured from each of these core glass rods. During the second heating process P4 when manufacturing each optical fiber preform 1P, the concentrations of carbon monoxide and carbon dioxide in each space 35S were measured by the gas measuring unit 48. The carbon monoxide concentration was 150 ppm or more and 250 ppm or less, and the carbon dioxide concentration was 250 ppm or more and 400 ppm or less. Furthermore, when the space 35S was checked after the manufacturing of the optical fiber preform 1P, no water had entered the space 35S.

Each of the 32 optical fiber preforms 1P thus produced was heated in a spinning furnace and drawn to produce an optical fiber 1 similar to the optical fiber 1 shown in FIG. 1 from each of the optical fiber preforms 1P. The diameter of the core 10 in each optical fiber 1 was approximately 10 μm, and the diameter of the cladding 11 was approximately 125 μm. The transmission loss of light with a wavelength of 1383 nm was measured for each optical fiber 1 using an OTDR (Optical Time Domain Reflectometer). The measurement results are shown in FIG. 5 as described above. Note that FIG. 5 also shows a dashed line indicating 0.31 dB/km, which is the transmission loss value generally required for optical fibers for long-distance transmission.

As shown in FIG. 5, the optical fiber 1 manufactured from the first to the 27th core glass rods had a transmission loss of approximately 0.28 dB/km, and the optical fiber 1 manufactured from the 28th core glass rod had a transmission loss of 0.309 dB/km. The optical fiber 1 manufactured from the 29th and subsequent core glass rods had a transmission loss of more than 0.31 dB/km, and the transmission loss tended to increase as the number of rods increased from the 29th to the subsequent core glass rods. In addition, the carbon monoxide concentration was maximum in the 28th rod when manufacturing the first to the 28th core glass rods, and the carbon monoxide concentration in the 28th rod was 397 ppm. In addition, the carbon dioxide concentration was maximum in the 28th rod among the first to the 28th core glass rods, and the carbon dioxide concentration in the 28th rod was 448 ppm. The carbon monoxide concentration in the 29th fiber was 703 ppm, and the carbon dioxide concentration in the 29th fiber was 813 ppm, and the concentrations of carbon monoxide and carbon dioxide increased as the number of fibers increased after the 29th fiber. Therefore, it is considered that water started to infiltrate into the space 35S when the 28th fiber was manufactured, and the amount of water infiltrating into the space 35S increased as the number of fibers increased after the 28th fiber. As described above, the carbon monoxide concentration in the initial state was 150 ppm, and the carbon dioxide concentration was 260 ppm. Therefore, it was found that the optical fiber 1 becomes defective when the difference between the carbon monoxide concentration when the core porous glass body 20 as the glass member is heated and the carbon monoxide concentration in the initial state before the core porous glass body 20 is heated for the first time after the furnace body 35 is installed exceeds 550 ppm. It was also found that the optical fiber 1 becomes defective when the difference between the carbon dioxide concentration when the core porous glass body 20 is heated and the carbon dioxide concentration in the initial state exceeds 550 ppm. It was also found that the optical fiber 1 becomes defective when the carbon monoxide concentration is 700 ppm or more, or when the carbon dioxide concentration is 800 ppm or more. When water and carbon react with each other, methane, oxygen, and hydrogen are generated in addition to carbon monoxide and carbon dioxide. The amounts of methane, oxygen, and hydrogen generated tend to be stoichiometrically proportional to the amounts of carbon monoxide and carbon dioxide generated. For this reason, it is possible to set reference values for the concentrations of methane, oxygen, and hydrogen based on experimental values, etc., for determining whether the optical fiber 1 becomes defective.

In addition, in the first to 28th samples, the difference between the carbon monoxide concentration and the average carbon monoxide concentration measured before the carbon monoxide concentration was measured was 500 ppm or less. In the 29th sample, the difference was 506 ppm. Therefore, it was found that the dehydration sintering apparatus 100 was in an abnormal state when the difference was 500 or more. In the first to 28th samples, the difference between the carbon dioxide concentration and the average carbon dioxide concentration measured before the carbon dioxide concentration was measured was 550 ppm or less. In the 29th sample, the difference was 553 ppm. Therefore, it was found that the dehydration sintering apparatus 100 was in an abnormal state when the difference was 550 or more. Furthermore, it was found that the dehydration sintering apparatus 100 was in an abnormal state when the carbon monoxide concentration was 700 ppm or more and the carbon dioxide concentration was 800 ppm or more. As described above, the amounts of methane, oxygen, and hydrogen generated tend to be proportional to the amounts of carbon monoxide and carbon dioxide generated, so reference values can be set for the concentrations of methane, oxygen, and hydrogen based on experimental values, etc., to determine whether the dehydration and sintering apparatus 100 is in an abnormal state.

As described above, a glass member heating device capable of detecting abnormal conditions caused by water, a glass member heating method, and a method for manufacturing optical fiber preforms using the same have been provided, and are expected to be used in fields such as optical fiber communications.

1: Optical fiber 1P: Optical fiber preform 20: Porous glass body for core (porous glass body)
31: Furnace tube 31S: Storage space 35: Furnace body 35S: Space 36: Flow path 37: Heater 41: First gas supply unit 42: Second gas supply unit 48: Gas measurement unit 51: Abnormality determination unit 52: Fiber defect determination unit 60: Control unit 100: Dehydration and sintering device (heating device)
S1, S2...Air supply ports E1, E2...Exhaust port P1...First deposition process P2...First heating process P3...Second deposition process P4...Second heating process

Claims (10)

a furnace tube having an accommodation space capable of accommodating at least a portion of the glass member;
a furnace body surrounding at least a portion of the furnace core tube;
a heater disposed in a space surrounded by the furnace core tube and the furnace body;
A gas measuring unit;
Equipped with
At least one of the members disposed in the space includes carbon;
the gas measurement unit is capable of measuring a concentration of a gas generated due to a reaction between water and carbon in the space,
The furnace body is located within an outer wall of the furnace body and has a flow path through which cooling water flows.
1. A heating device for a glass member. a furnace tube having an accommodation space capable of accommodating at least a portion of the glass member;
a furnace body surrounding at least a portion of the furnace core tube;
a heater disposed in a space surrounded by the furnace core tube and the furnace body;
A gas measuring unit;
Equipped with
At least one of the members disposed in the space includes carbon;
the gas measurement unit is capable of measuring a concentration of a gas generated due to a reaction between water and carbon in the space,
An abnormality determination unit that determines whether or not an abnormal state exists based on a change over time in the concentration of the gas measured by the gas measurement unit,
The abnormality determination unit determines that an abnormal state exists when a difference between the concentration of the gas measured by the gas measurement unit and an average value of the concentration of the gas measured by the gas measurement unit before the timing at which the concentration of the gas is measured is equal to or greater than a predetermined value.
1. A heating device for a glass member. 3. The heating apparatus for a glass member according to claim 2 , wherein the furnace body has a flow path through which cooling water flows. An abnormality determination unit that determines whether or not an abnormal state exists based on a change over time in the concentration of the gas measured by the gas measurement unit,
2. The heating device for a glass member according to claim 1, wherein the abnormality determination unit determines that an abnormal state has occurred when a difference between the concentration of the gas measured by the gas measuring unit and an average value of the concentration of the gas measured by the gas measuring unit prior to the timing at which the concentration of the gas is measured is equal to or greater than a predetermined value. 5. The heating apparatus for a glass member according to claim 1 , wherein the gas is at least one of carbon monoxide, carbon dioxide, methane, and hydrogen. 6. The heating device for a glass member according to claim 1 , further comprising a gas supply unit for supplying an inert gas to the space through an air supply port formed in the furnace body and communicating with the space. 7. The heating device for a glass member according to claim 1, wherein the gas measuring unit measures a concentration of the gas from an exhaust gas exhausted from an exhaust port formed in the furnace body and communicating with the space. A fiber defect determination unit is further provided,
the glass member is a porous glass body that becomes a part of an optical fiber;
8. The glass member heating device according to claim 1, wherein the fiber defect determination unit determines whether the optical fiber will become defective based on a change over time in the concentration of the gas measured by the gas measurement unit. the gas is carbon monoxide;
the glass member is a porous glass body that serves as a core of the optical fiber,
9. The heating device for a glass member according to claim 8, wherein the fiber defect determination unit determines that the optical fiber is defective when a difference between a concentration of the gas measured by the gas measurement unit and a concentration of the gas in an initial state before the glass member is heated for the first time after the furnace body is installed exceeds 550 ppm. a furnace tube having an accommodation space capable of accommodating at least a portion of the glass member;
a furnace body surrounding at least a portion of the furnace core tube;
a heater disposed in a space surrounded by the furnace core tube and the furnace body;
A gas measuring unit;
Fiber defect judgment unit and
Equipped with
At least one of the members disposed in the space includes carbon;
the gas measurement unit is capable of measuring a concentration of a gas generated due to a reaction between water and carbon in the space,
the glass member is a porous glass body that serves as a core of an optical fiber;
the gas is carbon monoxide;
The fiber defect determination unit determines that the optical fiber is defective when a difference between the gas concentration measured by the gas measurement unit and the gas concentration in an initial state before the glass member is heated for the first time after the furnace body is installed exceeds 550 ppm.
1. A heating device for a glass member.

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