Glass component heating device, glass component heating method, and optical fiber base material manufacturing method using the same

Abstract

The present invention provides a heating device for a glass component. As a heating device for a glass component, a dehydration sintering device (100) includes: a furnace core tube (31), a furnace body (35), a heater (37), and a gas measuring unit (48). The furnace core tube (31) has a storage space (31S), and the storage space (31S) can store a porous glass body (20) for a core as a glass component. The furnace body (35) surrounds a portion of the furnace core tube (31). The heater (37) is arranged in a space (35S) surrounded by the furnace core tube (31) and the furnace body (35). At least one of the components arranged in the space (35S) contains carbon, and the gas measuring unit (48) can measure the concentration of gas generated by the reaction between water and carbon in the space (35S).

Description

Technical Field

[0001] The present invention relates to a glass component heating device, a glass component heating method, and a method for manufacturing an optical fiber base material using the same. Background Art

[0002] As a method for manufacturing optical fiber base materials used in optical fiber manufacturing, the following methods are known: using the OVD method (Outside Vapor Deposition method), the VAD method (Vapor Phase Axial Deposition method), etc., to accumulate glass particles to form a porous glass body, and then heating and sintering the porous glass body.

[0003] Patent Document 1 below discloses a heating device for heating a porous glass body. This heating device comprises a furnace core tube having a storage space for the porous glass body; a heater disposed outside the furnace core tube; a furnace body surrounding a portion of the furnace core tube and the heater; and a gas detector. The gas detector detects gas that leaks from the furnace core tube into the space enclosed by the furnace core tube and the furnace body and is discharged from an exhaust port provided in the furnace body. Therefore, this heating device can detect damage to the furnace core tube, such as cracks, using the gas detector.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-48262 Summary of the Invention

[0007] (1) Technical issues to be resolved

[0008] However, the furnace body of the above-mentioned heating device has the following problems: it is sometimes cooled by cooling water. If the furnace body is damaged, the cooling water may invade the space surrounded by the furnace core tube and the furnace body. In addition, inert gas is sometimes supplied to this space to suppress the combustion of components arranged in this space. Due to a malfunction of the gas supply device, etc., it is possible that water and the inert gas may invade this space together. In addition to this reason, water may also invade this space due to degradation or aging of the device, and there are many possible paths for water to invade. The furnace core tube is generally composed of quartz, carbon, etc. In such an abnormal state where water enters the above-mentioned space, even if the furnace core tube is not damaged, water may penetrate from this space into the storage space of the furnace core tube. If water invades the storage space when the porous glass body is heated and sintered by the heater, the characteristics of the final optical fiber, such as transmission loss, will deteriorate.

[0009] Therefore, an object of the present invention is to provide a glass member heating device and a glass member heating method capable of detecting an abnormal state caused by water, and a method for manufacturing an optical fiber preform using the same.

[0010] (2) Technical solution

[0011] In order to achieve the above-mentioned object, the present invention provides a heating device for glass components, characterized in that it comprises: a furnace core tube having a storage space capable of storing at least a portion of the glass component; a furnace body surrounding at least a portion of the furnace core tube; a heater arranged in the space surrounded by the furnace core tube and the furnace body; and a gas measuring unit, at least one of the components arranged in the space contains carbon, and the gas measuring unit is capable of measuring the concentration of gas generated by the reaction between water and carbon in the space.

[0012] In addition, in order to achieve the above-mentioned purpose, the present invention provides a method for heating a glass component, wherein at least a portion of the glass component is stored in a storage space in a furnace core tube that is at least partially surrounded by a furnace body, and the glass component is heated using a heater arranged in the space surrounded by the furnace core tube and the furnace body. The method is characterized in that at least one of the components arranged in the space contains carbon, the glass component is heated using the heater, and the concentration of the gas generated by the reaction between water and carbon in the space is measured.

[0013] When dehydrating, sintering, or melting glass components, heaters typically heat to temperatures exceeding 700°C. At such high temperatures, if water enters the aforementioned space, it reacts with carbon contained in components located therein, generating gas. The glass component heating device and method can measure the concentration of this generated gas, thus enabling detection of abnormal conditions such as water entering the aforementioned space.

[0014] The gas may be at least one of carbon monoxide, carbon dioxide, methane, and hydrogen.

[0015] The furnace body may include a flow path for cooling water to flow.

[0016] This structure can suppress heat-induced damage to the furnace body. In addition, since the gas measuring unit can measure the concentration of gas generated by the reaction between water and carbon in the above-mentioned space, damage to the furnace body caused by cooling water entering the above-mentioned space can be detected.

[0017] The above-mentioned heating device for a glass member may further include a gas supply unit configured to supply an inert gas to the space from a gas supply port formed in the furnace body and communicating with the space.

[0018] This structure can suppress combustion of components placed in the aforementioned space. Furthermore, since the gas measurement unit can measure the concentration of gas generated by the reaction between water and carbon within the aforementioned space, it can detect malfunctions in the gas supply unit, piping, etc., caused by water entering the aforementioned space along with inert gas.

[0019] In the above-mentioned glass member heating device, the gas measuring unit may measure the concentration of the gas based on exhaust gas exhausted from an exhaust port formed in the furnace body and communicating with the space.

[0020] By adopting this structure, the influence of the location where the gas is generated in the space on the concentration of the gas can be suppressed compared to when the concentration of the gas is measured at a certain location in the space. Therefore, compared with the above situation, the abnormal state of water entering the space can be detected more accurately.

[0021] The above-mentioned glass member heating device may further include an abnormality determination unit configured to determine whether or not an abnormal state exists based on a temporal change in the concentration of the gas measured by the gas measuring unit.

[0022] At this time, the abnormality judgment unit may judge that it is an abnormal state when the difference between the concentration of the gas measured by the gas measuring unit and the average value of the concentration of the gas measured by the gas measuring unit before the concentration of the gas is measured is greater than a specified value.

[0023] Even with furnaces of the same structure, the concentration of the gas measured in a stable state tends to vary depending on the furnace's installation configuration. Therefore, the above configuration allows for more appropriate determination of an abnormal state, compared to determining an abnormal state only when the gas concentration exceeds a specified value.

[0024] The heating device for the glass component may further include an optical fiber defect judgment unit, wherein the glass component is a porous glass body that becomes a part of the optical fiber, and the optical fiber defect judgment unit judges whether the optical fiber is defective based on the temporal change in the concentration of the gas measured by the gas measuring unit.

[0025] As described above, if water intrudes into the storage space during the sintering of the porous glass body, the characteristics of the resulting optical fiber, such as transmission loss, will deteriorate, and the more water that intrudes into the storage space, the worse the characteristics tend to be. This water intrusion into the storage space may not affect the appearance of the transparent glass component formed by sintering the porous glass body. Therefore, it is difficult to determine whether the characteristics of the resulting optical fiber have deteriorated, resulting in defective optical fibers, based on the appearance of the transparent glass component. However, the more water that intrudes into the storage space, the more gas is generated by the reaction between water and carbon, and the concentration of this gas increases. Therefore, by adopting the above-mentioned structure, it is possible to determine whether the resulting optical fiber is defective during the manufacturing stage of the transparent glass component, thereby reducing the defective rate of the optical fiber and improving the productivity of the optical fiber.

[0026] At this time, the gas may be carbon monoxide, and the glass component may be a porous glass body that becomes the core of the optical fiber. When the difference between the concentration of the gas measured by the gas measuring unit and the concentration of the gas in the initial state from the time the furnace body is set to the time the glass component is heated for the first time exceeds 550 ppm, the optical fiber defect judgment unit judges that the optical fiber is defective.

[0027] The inventors of this invention have discovered that when the carbon monoxide concentration of the porous glass body forming the core differs by more than 550 ppm from the carbon monoxide concentration in the initial state described above when the porous glass body is heated, an optical fiber manufactured using an optical fiber preform including a core glass body composed of the porous glass body is defective. Therefore, by adopting this structure, it is possible to appropriately predict whether the finally manufactured optical fiber is defective.

[0028] The present invention provides a method for producing an optical fiber base material, characterized by comprising a heating step in which a porous glass body serving as the glass member is heated using the above-mentioned method for heating the glass member.

[0029] (3) Beneficial effects

[0030] As described above, according to the present invention, there are provided a glass member heating device capable of detecting an abnormal state caused by water, a glass member heating method, and a method for manufacturing an optical fiber preform using the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a diagram schematically showing a cross section perpendicular to the longitudinal direction of an optical fiber according to an embodiment of the present invention.

[0032] Figure 2 It is a general representation of the Figure 1 The diagram shows a cross section perpendicular to the longitudinal direction of an optical fiber and an optical fiber base material.

[0033] Figure 3 This is a flowchart showing the steps of a method for manufacturing an optical fiber preform and an optical fiber according to an embodiment of the present invention.

[0034] Figure 4 This is a diagram schematically showing a dehydration sintering apparatus used in the first heating step.

[0035] Figure 5 This is a graph showing the relationship between each core glass rod in the experimental example, the concentrations of carbon monoxide and carbon dioxide measured during sintering, and the transmission loss of the manufactured optical fiber. DETAILED DESCRIPTION

[0036] The following illustrates, with reference to the accompanying drawings, a glass component heating device, a glass component heating method, and a method for manufacturing an optical fiber base material using the same. The following exemplary embodiments are intended to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention is susceptible to modification and improvement without departing from its spirit. Furthermore, in the drawings referenced below, the dimensions of various components may be altered for ease of understanding.

[0037] Figure 1 FIG is a diagram schematically showing a cross section perpendicular to the longitudinal direction of an optical fiber according to an embodiment of the present invention. Figure 1 As shown, the optical fiber 1 of this embodiment has as its main structure: a core 10, a cladding 11 surrounding the outer peripheral surface of the core 10, and a cladding 12 covering the outer peripheral surface of the cladding 11. The outer shape of the core 10 in this cross section is circular, and the core 10 is arranged at the center of the cladding 11. In addition, the outer shape of the cladding 11 in this cross section can also be non-circular, such as elliptical or polygonal. Figure 1 , an optical fiber 1 is shown in which the outer shape of the cladding 11 is circular.

[0038] The refractive index of the core 10 is higher than that of the cladding 11. In this embodiment, the core 10 is composed of silica glass doped with a refractive index-raising dopant such as germanium (Ge), while the cladding 11 is composed of silica glass without any additives. Alternatively, the core 10 may be composed of silica glass without any additives, while the cladding 11 may be composed of silica glass doped with a refractive index-lowering dopant such as fluorine (F). Alternatively, the core 10 may be composed of silica glass doped with a refractive index-raising dopant, while the cladding 11 may be composed of silica glass doped with a refractive index-lowering dopant. There are no particular limitations on the refractive index-raising and refractive index-lowering dopants.

[0039] The coating layer 12 is made of a resin. Examples of the resin that constitutes the coating layer 12 include thermosetting resins and ultraviolet curable resins. The coating layer 12 may be a single-layer structure consisting of a single resin layer surrounding the cladding layer 11, or a multilayer structure consisting of a plurality of resin layers.

[0040] Figure 2 It is a general representation of the Figure 1 FIG. 1 is a diagram showing a cross section of an optical fiber base material of an optical fiber 1 perpendicular to the longitudinal direction. Figure 2 As shown, the optical fiber preform 1P is composed of a rod-shaped core glass body 10P, which serves as the core 10, and a cladding glass body 11P, which surrounds the outer circumference of the core glass body 10P and serves as the cladding 11. In this embodiment, the outer shape of the cladding glass body 11P in this cross section is circular, and the core glass body 10P is arranged at the center of the cladding glass body 11P. In addition, the outer shape of the core glass body 10P in this cross section is circular.

[0041] Next, a method for manufacturing the optical fiber preform according to this embodiment will be described.

[0042] Figure 3 1 is a flowchart showing the steps of the method for manufacturing the optical fiber base material 1P according to the present embodiment. Figure 3 As shown, the method for manufacturing the optical fiber preform 1P according to the present embodiment includes a first deposition step P1 , a first heating step P2 , a second deposition step P3 , and a second heating step P4 .

[0043] (First Stacking Step P1)

[0044] This process is to make glass particles accumulate to form Figure 2 The process of forming the core glass body 10P, i.e., the porous glass body for the core, is shown. The porous glass body can be formed by a powder method such as OVD or VAD. In this embodiment, the VAD method is used to deposit glass particles along the axial direction of a prepared glass rod from one end of the rod to form the porous glass body for the core.

[0045] (First Heating Step P2)

[0046] This step is a step of heating the glass member formed in the first deposition step P1, that is, the porous glass body for the core. Figure 3 As shown, the process includes a first dehydration step P2a and a first sintering step P2b. First, the dehydration and sintering device used in this process as a heating device for the glass member will be described.

[0047] Figure 4 : is a diagram schematically showing a dehydration sintering device used in the first heating step P2. Figure 4As shown, the dehydration sintering device 100 of this embodiment includes as main structures: a heating furnace 30, a lifting unit 40, a first gas supply unit 41, a second gas supply unit 42, a gas measuring unit 48, a judgment unit 50, a memory 55, a notification unit 56, and a control unit 60.

[0048] The control unit 60 is comprised of, for example, a microcontroller, an integrated circuit (IC), an LSI (Large-scale Integrated Circuit), an ASIC (Application Specific Integrated Circuit), or an NC (Numerical Control) device. Furthermore, when the NC device is employed, the control unit 60 may or may not utilize a machine learning engine. As described below, several components of the dehydration and sintering apparatus 100 are controlled by the control unit 60.

[0049] In the present embodiment, the heating furnace 30 includes a furnace core tube 31 , a furnace body 35 , a heater 37 , and a heat insulating material 38 as main components.

[0050] The furnace core tube 31 of this embodiment is a cylindrical component extending in the up-down direction, which can accommodate the porous glass body 20 for the core in the storage space 31S. In this embodiment, the openings at both ends of the furnace core tube 31 are closed, and the portion of the opening on the closed upper side can be removed from other portions. A through hole is formed at the portion of the opening on the closed upper side of the furnace core tube 31, and the support rod 22 for suspending the porous glass body 20 for the core is inserted into the through hole. A connecting portion 23 is provided at the lower end of the support rod 22, and a glass rod 24 stacked with the porous glass body 20 for the core is connected to the connecting portion 23. An exhaust port E1 and an air supply port S1 are formed on the furnace core tube 31, which are respectively connected to the storage space 31S. As the material constituting the furnace core tube 31, for example, quartz, carbon, etc. can be cited.

[0051] The furnace body 35 of this embodiment is formed into a hollow box shape. Within its outer wall, the furnace body 35 has a flow path 36 for cooling water supplied from a cooling water supply unit (not shown). Cooling water flowing through the flow path 36 cools the furnace body 35, thereby preventing heat-induced damage to the furnace body 35. Furthermore, a through-hole extending vertically through the center of the furnace body 35 is formed, into which the core tube 31 is inserted. The upper and lower ends of the core tube 31 protrude from the furnace body 35. The furnace body 35 surrounds the center of the core tube 31 vertically, forming a space 35S enclosed by the core tube 31 and the furnace body 35. Furthermore, an air supply port S2 and an exhaust port E2 are formed in the furnace body 35, communicating with this space 35S. The air supply port S2 is located on one side in the horizontal direction relative to the core tube 31, and the exhaust port E2 is located on the other side. Examples of materials for the furnace body 35 include metal.

[0052] The heater 37 is arranged in the space 35S and can heat the porous glass body 20 for the fiber core stored in the storage space 31S of the furnace core tube 31 by generating heat. The heater 37 of this embodiment is made of carbon and is formed in a ring shape surrounding the furnace core tube 31, but the heater 37 can also be divided into a plurality of heating parts, and the plurality of heating parts can be discontinuously arranged in a manner surrounding the furnace core tube 31. The heater 37 adjusts the heating temperature according to the control signal from the control unit 60. In order to effectively utilize the heat generated by the heater 37, an insulating material 38 is arranged between the heater 37 and the furnace body 35 in the space 35S. There is no particular restriction on the number of insulating materials 38, and the insulating material 38 can be divided into a plurality of parts. The insulating material 38 of this embodiment is made of carbon. Therefore, in this embodiment, the components arranged in the space 35S, namely the heater 37 and the insulating material 38, contain carbon. Furthermore, at least one of the components disposed in the space 35S only 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 may not include the heat insulating material 38 .

[0053] The lifting unit 40 lifts and lowers the supported rod 22. The lifting unit 40 lifts and lowers the supported rod 22 in accordance with a control signal from the control unit 60, thereby vertically moving the porous glass body for the core 20 attached to the supported rod 22. The structure of the lifting unit 40 is not particularly limited.

[0054] The first gas supply unit 41 supplies a first gas containing a dehydration gas to the storage space 31S via a pipe 43 connected to a gas supply port 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 storage space 31S is discharged 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. Examples of the dehydration gas include chlorine-based gases such as chlorine, SiCl4, thionyl chloride (SOCl2), and carbon tetrachloride (CCl4), as well as carbon monoxide. Examples of the inert gas include He, Ar, and N2.

[0055] The second gas supply unit 42 supplies an inert gas, or second gas, to the space 35S via a pipe 45 connected to a gas supply port S2 of the furnace body 35. The second gas supply unit 42 adjusts the supply amount of the second gas in accordance with a control signal from the control unit 60. The second gas supplied to the space 35S is discharged 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.

[0056] In this embodiment, a gas measuring unit 48 is attached to the exhaust pipe 46. Based on the exhaust gas discharged from the exhaust port E2, it measures the concentration of a predetermined gas in the exhaust gas and outputs a signal indicating the measured predetermined gas concentration to the determination unit 50. The gas measuring unit 48 repeats this measurement and output intermittently or continuously. The predetermined gas is generated by the reaction between water and carbon. As mentioned above, at least one of the components located in the space 35S contains carbon. Therefore, when water enters the space 35S at a temperature of, for example, 700°C or higher, a temperature at which the water-carbon reaction occurs, the water reacts with the carbon contained in the components located in the space 35S to generate the predetermined gas. Furthermore, it is generally believed that under the high temperature conditions of the water-carbon reaction, the water decomposes into hydrogen atoms and oxygen atoms, which then react with the carbon. Examples of the predetermined gas include carbon monoxide, carbon dioxide, methane, oxygen, and hydrogen, and the gas measuring unit 48 is configured to measure the concentration of at least one of these gases. Examples of devices for measuring carbon monoxide concentration include a constant potential electrolytic sensor, a non-dispersive infrared sensor, a semiconductor laser absorption spectrometer, and a zirconia concentration cell sensor. The gas measuring unit 48 of this embodiment is configured to measure carbon monoxide concentration. Furthermore, the gas measuring unit 48 can be configured to measure the concentration of the predetermined gas within the space 35S, and may be installed in the furnace body 35, for example.

[0057] The determination unit 50 of this embodiment stores the concentration of the predetermined gas measured by the gas measuring unit 48 in the memory 55. Based on the temporal change in the concentration of the predetermined gas, the determination unit 50 determines whether the dehydration and sintering apparatus 100 is in an abnormal state and whether the manufactured optical fiber is defective. The configuration of the determination unit 50 can be, for example, the same as that of the control unit 60.

[0058] Memory 55 is, for example, a non-transitory storage medium, preferably a semiconductor storage medium such as RAM (Random Access Memory) or ROM (Read Only Memory). However, it may also include any other storage medium, such as an optical storage medium or a magnetic storage medium. In this embodiment, memory 55 stores programs and information for executing these determination processes. The determination unit 50 reads the programs and information from memory 55 and, in this state, includes an abnormality determination unit 51 and a fiber failure determination unit 52 to execute the aforementioned determination processes.

[0059] The abnormality determination unit 51 determines whether the dehydration sintering apparatus 100 is in an abnormal state based on the temporal change in the concentration of the specified gas measured by the gas measurement unit 48. As described later, the inventors of this embodiment have discovered that if 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 measurement of the gas concentration is greater than a first predetermined value, it indicates an abnormal state of water intrusion into the space 35S. This is because the intrusion of water into the space 35S generates the specified gas due to the reaction between the water and carbon, increasing the concentration of the specified gas. Therefore, 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 measurement of the gas concentration is greater than a first predetermined value, 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. On the other hand, if the difference is less than the first specified value, the abnormality determination unit 51 does not output a signal to the control unit 60. However, it may output a signal indicating that the abnormal state is not occurring to the notification unit 56 via the control unit 60. Therefore, the determination by the abnormality determination unit 51 means changing the output signal based on the signal from the gas measurement unit 48. Furthermore, the first specified value can be pre-set through experiments, for example, to 500 ppm when the specified gas is carbon monoxide and to 450 ppm when the specified gas is carbon dioxide. Alternatively, the abnormality determination unit 51 may directly output a signal to the notification unit 56.

[0060] The fiber defect determination unit 52 determines whether an optical fiber manufactured using an optical fiber preform including a component formed of a porous glass body is defective based on the temporal changes in the concentration of a predetermined gas measured by the gas measurement unit 48 during heating of the porous glass body, which forms part of the optical fiber. As will be described later, the inventors of this application have discovered that if the difference between the concentration of the predetermined gas during heating of the porous glass body and the concentration of the predetermined gas in the initial state exceeds a second predetermined value, the optical fiber manufactured using the optical fiber preform including a glass component formed of the porous glass body is considered defective. If the amount of water intruding into the space 35S is large, the amount of water that permeates the furnace core tube 31 and enters the storage space 31S will also increase, resulting in deterioration in the characteristics of the manufactured optical fiber, such as transmission loss. Furthermore, it is understood that if the difference exceeds the second predetermined value, the optical fiber will not meet the characteristics typically required for long-distance transmission. The initial state described above refers to the state from the installation of the furnace body 35 to the first heating of the core porous glass body 20. The second predetermined value can be preset through experiments, for example. For example, if the predetermined gas is carbon monoxide and the porous glass body is the core porous glass body 20 that forms the core 10 of the optical fiber 1, the second predetermined value is 550 ppm. When the difference between the carbon monoxide concentration and the initial carbon monoxide concentration exceeds 550 ppm, the optical fiber failure determination unit 52 of this embodiment outputs a signal indicating a defect in the optical fiber 1 to the control unit 60. On the other hand, when the difference is less than 550 ppm, the optical fiber failure determination unit 52 does not output a signal to the control unit 60, but may output a signal to the control unit 60 indicating that the optical fiber 1 is not defective. Therefore, the determination by the optical fiber failure determination unit 52 means changing the output signal based on the signal from the gas measurement unit 48. Alternatively, the optical fiber failure determination unit 52 may directly output a signal to the notification unit 56.

[0061] The notification unit 56 of this embodiment makes a notification based on the signal from the abnormality determination unit 51 and the signal from the optical fiber failure determination unit 52. The notification unit 56 may include, for example, a configuration including at least one of a display and a speaker.

[0062] Next, the first dehydration step P2a and the first sintering step P2b of the first heating step P2 will be described.

[0063] (First Dehydration Step P2a)

[0064] This process is a process of heating the core porous glass body 20 using the dehydration sintering device 100 to dehydrate the core porous glass body 20. In this process, first, Figure 4As shown, the porous glass body 20 for the core, suspended from the support rod 22, is housed in the housing space 31S of the furnace core tube 31. The first gas supply unit 41 supplies a first gas to the housing space 31S in accordance with a control signal from the control unit 60, filling the housing space 31S with the first gas and discharging the gas in the housing space 31S through the discharge pipe 44. Furthermore, the second gas supply unit 42 supplies a second gas to the space 35S in accordance with a control signal from the control unit 60, filling the space 35S with the second gas and discharging the gas in the space 35S through the discharge pipe 46. Consequently, combustion of the heater 37, the insulation material 38, and the like in the space 35S can be suppressed.

[0065] In the state where the first gas supply part 41 and the second gas supply part 42 supply gas in this way, the heater 37 generates heat according to the control signal from the control part 60. In the state where the heater 37 generates heat, the lifting part 40 moves the porous glass body 20 for core at a predetermined speed according to the control signal from the control part 60, so that the porous glass body 20 for core passes through the heater 37 as a whole. Therefore, the porous glass body 20 for core is heated by the heater 37 at a predetermined temperature. Through this heating, the OH group and attached water of the porous glass body 20 for core are removed by the dehydration gas contained in the first gas. In addition, the heating temperature can be any temperature as long as it is lower than the sintering temperature of the porous glass body 20 for core and can remove water from the porous glass body 20 for core, for example, it is preferably not less than 1100°C and not more than 1400°C. Since the heating temperature is 1100° C. or higher, the diffusion of the gas into the porous glass body 20 for the core can be promoted, and since the heating temperature is 1400° C. or lower, the softening of the porous glass body 20 for the core can be sufficiently suppressed.

[0066] While the porous glass body 20 for the core is heated by the heater 37 in this manner, the gas measuring unit 48 measures the concentration of carbon monoxide at predetermined time intervals, for example, every minute, and outputs a signal indicating the measured carbon monoxide concentration to the determining unit 50. Specifically, in this step, the porous glass body 20 for the core is heated by the heater 37 and the concentration of carbon monoxide is measured by the gas measuring unit 48, thereby heating the porous glass body 20 for the core.

[0067] When the difference between the concentration of carbon monoxide (the predetermined gas) measured by gas measurement unit 48 and the average value of carbon monoxide concentrations measured by gas measurement unit 48 immediately before the carbon monoxide concentration was measured is greater than a first predetermined value, abnormality determination unit 51 outputs a signal indicating an abnormal state to notification unit 56, which then issues a notification based on the signal from abnormality determination unit 51. Therefore, the operator can recognize the abnormal state based on the notification from notification unit 56. Furthermore, when the difference between the carbon monoxide concentration measured by gas measurement unit 48 and the carbon monoxide concentration previously measured by gas measurement unit 48 under the aforementioned initial state exceeds 550 ppm, optical fiber failure determination unit 52 outputs a signal indicating an optical fiber failure to control unit 60, which then issues a notification based on the signal from optical fiber failure determination unit 52. Therefore, the operator can determine whether the manufactured optical fiber is defective based on the notification from notification unit 56.

[0068] (First Sintering Step P2b)

[0069] This process is a process in which the porous glass body 20 for the core is heated and sintered using the dehydration and sintering device 100 used in the first dehydration process P2a after the first dehydration process P2a. Similar to the first dehydration process P2a, the first gas supply unit 41 supplies the first gas to the storage space 31S, and the second gas supply unit 42 supplies the second gas to the space 35S. In addition, while the first gas supply unit 41 and the second gas supply unit 42 are supplying gas in this manner, the heater 37 generates heat. In addition, while the heater 37 is generating heat, the lifting unit 40 moves the porous glass body 20 for the core at a predetermined speed so that the entire porous glass body 20 for the core passes through the heater 37. Therefore, the porous glass body 20 for the core is heated by the heater 37 at a predetermined temperature, and the porous glass body 20 for the core is sintered by this heating. The heating temperature may be any temperature at which the porous glass body 20 for a core is sintered and transformed into transparent glass, and is preferably 1300° C. or higher and 1650° C. or lower, for example.

[0070] As in the first dehydration step P2a, the gas measuring unit 48 measures the concentration of carbon monoxide, for example, at intervals of 1 minute, and outputs a signal indicating the measured carbon monoxide concentration to the judgment unit 50. Therefore, in this step, as in the first dehydration step P2a, the porous glass body 20 for the core is heated by the heater 37, and the concentration of carbon monoxide is measured by the gas measuring unit 48, and the porous glass body 20 for the core is heated by such a heating method. Furthermore, as in the first dehydration step P2a, the notification unit 56 is used to make notifications based on the signals from the abnormality judgment unit 51 and the optical fiber defect judgment unit 52. Through this step, the porous glass body 20 for the core is made transparent and vitrified. Figure 2The core glass body 10P shown is a core glass rod, and the core glass rod is obtained from the glass rod 24 by cutting or the like.

[0071] (Second Stacking Step P3)

[0072] This step is to deposit glass particles on the outer surface of the core glass rod formed in the first sintering step P2b, thereby forming Figure 2 In this embodiment, the porous glass body for cladding is formed by depositing glass particles on the outer peripheral surface of the core glass rod by OVD, but there is no particular limitation on the method for forming the porous glass body for cladding.

[0073] (Second Heating Step P4)

[0074] This step is a step of heating the porous glass body for the cladding formed by the second deposition step P3. Figure 3 As shown, the second dehydration step P4a and the second sintering step P4b are included. In this embodiment, these steps are performed using another dehydration and sintering device 100 having the same structure as the dehydration and sintering device 100 used in the first heating step P2. However, the dehydration and sintering device 100 used in the first heating step P2 can also be used.

[0075] (Second Dehydration Step P4a)

[0076] This step involves heating the porous glass body for cladding and dehydrating it using the dehydration and sintering device 100. The main difference between this step and the first dehydration step P2a is that the core glass rod, with the porous glass body formed thereon, is stored in the storage space 31S of the furnace core tube 31. Therefore, a detailed description of this step will be omitted. In this step, the porous glass body for cladding is heated and dehydrated using the heater 37, and the carbon monoxide concentration is measured using the gas measurement unit 48. Furthermore, in this step, the optical fiber failure determination unit 52 does not determine whether the optical fiber is defective; instead, the notification unit 56 performs notification based on a signal from the abnormality determination unit 51.

[0077] (Second Sintering Step P4b)

[0078] This process is a process in which, after the second dehydration process P4a, the cladding porous glass body is heated and sintered using the dehydration and sintering device 100 used in the second dehydration process P4a. The main difference between this process and the first dehydration process P2a is that the core glass rod, which has been formed into the cladding porous glass body dehydrated in the second dehydration process P4a, is stored in the storage space 31S of the furnace core tube 31. Therefore, a detailed description of this process is omitted. In this process, the cladding porous glass body is heated and sintered using the heater 37, and the carbon monoxide concentration is measured using the gas measurement unit 48. In addition, in this process, the optical fiber defect determination unit 52 does not determine whether the optical fiber is defective. The notification unit 56 notifies based on the signal from the abnormality determination unit 51.

[0079] In this process, the core glass rod is basically unchanged and becomes Figure 2 The core glass body 10P shown in FIG. In addition, the cladding is made of a porous glass body and transparently vitrified to form a cladding glass body 11P. Figure 2 The optical fiber base material 1P is shown.

[0080] The optical fiber base material 1P thus obtained is heated in a spinning furnace and drawn, so that the core glass body 10P becomes the core 10 and the cladding glass body 11P becomes the cladding 11, thereby obtaining a bare optical fiber consisting of the core 10 and the cladding 11. The bare optical fiber is then coated with a resin to be the cladding 12, thereby forming the cladding 12. Figure 1 The optical fiber 1 is shown.

[0081] As described above, the dehydration and sintering apparatus 100, as a glass component heating device according to this embodiment, includes a furnace core tube 31, a furnace body 35, a heater 37, and a gas measuring unit 48. The furnace core tube 31 has a storage space 31S capable of storing the entire porous glass body 20 for the core, which serves as a glass component. The furnace body 35 surrounds at least a portion of the furnace core tube 31, and the heater 37 is disposed in the space 35S enclosed by the furnace core tube 31 and the furnace body 35. At least one of the components disposed in this space 35S contains carbon. The gas measuring unit 48 is capable of measuring the concentration of a predetermined gas generated by the reaction between water and carbon within the space 35S.

[0082] In addition, regarding the heating method of the porous glass body 20 for the core and the porous glass body for the cladding, which are glass components of this embodiment, these glass components are heated using a heater 37 disposed in a space 35S surrounded by the furnace core tube 31 and the furnace body 35. At least one of the components disposed in this space 35S contains carbon. Furthermore, while these glass components are heated by the heater 37, the concentration of a predetermined gas generated by the reaction between water and carbon in the space 35S is measured.

[0083] When dehydrating, sintering, or melting glass components, the heater is typically heated to 700°C or higher. Under these high temperatures, if water enters the space 35S enclosed by the furnace core tube 31 and the furnace body 35, it reacts with carbon contained in the components located therein, generating gas. The dehydration and sintering apparatus 100 and the glass component heating method of this embodiment can measure the concentration of this generated gas, thus enabling detection of abnormal conditions such as water entering the space 35S.

[0084] Furthermore, regarding the dehydration and sintering apparatus 100 and the glass member heating method of this embodiment, since the furnace body 35 includes a flow path 36 for circulating cooling water, damage to the furnace body 35 caused by heat can be suppressed. Furthermore, since the gas measuring unit 48 can measure the concentration of gas generated by the reaction between water and carbon within the space 35S, damage to the furnace body 35 caused by the intrusion of cooling water into the space 35S can be detected.

[0085] The dehydration and sintering apparatus 100 of this embodiment further includes a second gas supply unit 42, which supplies inert gas to the space 35S from a gas supply port S2 formed in the furnace body 35 and communicating with the space 35S. This prevents combustion of components located in the space 35S, such as the heater 37 and the insulation material 38. Furthermore, since the gas measurement unit 48 can measure the concentration of gas generated by the reaction between water and carbon within the space 35S, it can detect malfunctions in the second gas supply unit 42, the piping 45 connected thereto, and the like, caused by water entering the space 35S along with the inert gas.

[0086] Furthermore, in the dehydration and sintering apparatus 100 and the glass member heating method of this embodiment, the concentration of the predetermined gas is measured based on the exhaust gas discharged from the exhaust port E2 formed in the furnace body 35 and communicating with the space 35S. Therefore, compared to measuring the concentration of the predetermined gas at a specific location within the space 35S, the influence of the location where the predetermined gas is generated within the space 35S on the concentration of the predetermined gas can be suppressed. Consequently, compared to the above-described situation, abnormal conditions such as water entering the space 35S can be detected more accurately.

[0087] In addition, the dehydration and sintering apparatus 100 of this embodiment further includes an abnormality determination unit 51, which determines whether an abnormal state exists based on the temporal change in the concentration of the specified gas measured by the gas measuring unit 48. When the difference between the concentration of the specified gas measured by the gas measuring unit 48 and the average value of the concentration of the specified gas measured by the gas measuring unit 48 immediately before the concentration of the specified gas is measured is greater than a first specified value, the abnormality determination unit 51 determines that an abnormal state exists. There is a tendency that even for furnace bodies 35 of the same structure, the concentration of the specified gas measured in a stable state may vary depending on the installation state of the furnace body 35. Therefore, by adopting the above-mentioned structure, it is possible to more appropriately determine whether an abnormal state exists, compared to a case where an abnormal state is determined when the gas concentration is greater than a specified value.

[0088] The dehydration and sintering apparatus 100 of this embodiment further includes an optical fiber defect determination unit 52, which heats the porous glass body 20 for the core, which is a part of the optical fiber 1. The optical fiber defect determination unit 52 determines whether the optical fiber 1 is defective based on the time-dependent change in the concentration of a predetermined gas measured by the gas measurement unit 48 while the porous glass body 20 for the core is heated.

[0089] If water intrudes into the storage space 31S during the sintering of the porous glass body 20 for the core, the characteristics of the resulting optical fiber 1, such as transmission loss, will deteriorate. The greater the amount of water that intrudes into the storage space 31S, the worse the characteristics tend to be. This water intrusion into the storage space 31S may not affect the appearance of the transparent glass component formed by sintering the porous glass body 20 for the core. Therefore, it is difficult to determine whether the characteristics of the resulting optical fiber 1 have deteriorated, resulting in a defective optical fiber 1, based on the appearance of the transparent glass component. However, the greater the amount of water that intrudes into the storage space 31S, the greater the amount of gas generated by the reaction between water and carbon, and the higher the concentration of this gas. Therefore, by adopting the above-described structure, it is possible to determine whether the resulting optical fiber 1 is defective during the manufacturing stage of the transparent glass component, thereby reducing the defective rate of optical fiber 1 and improving the productivity of optical fiber 1.

[0090] In this embodiment, the prescribed gas is carbon monoxide, and when the difference between the carbon monoxide concentration measured by the gas measuring unit 48 during heating of the core porous glass body 20 forming the core 10 of the optical fiber 1 and the carbon monoxide concentration in the initial state exceeds 550 ppm, the optical fiber failure determination unit 52 determines that the optical fiber 1 is defective. As described above, the inventors of this application have discovered that when this difference exceeds 550 ppm, the optical fiber 1 manufactured using the optical fiber preform 1P including the core glass body 10P formed of the core porous glass body 20 is defective. Therefore, by adopting this configuration, it is possible to appropriately determine whether the finally manufactured optical fiber 1 is defective.

[0091] The present invention has been described above by taking the above-mentioned embodiment as an example, but the present invention is not limited thereto.

[0092] For example, in the above embodiment, the dehydration and sintering apparatus 100 is described as including the abnormality determination unit 51 and the optical fiber defect determination unit 52. However, the dehydration and sintering apparatus 100 may not include at least one of the abnormality determination unit 51 and the optical fiber defect determination unit 52. In this case, for example, the operator can determine whether an abnormal state exists or whether the optical fiber 1 is defective based on the temporal changes in the concentration of the predetermined gas measured by the gas measurement unit 48.

[0093] In the above embodiment, the abnormality determination unit 51 is described as an example. This abnormality determination unit 51 determines an abnormal state 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 immediately before the concentration of the specified gas is measured is greater than a first specified value. However, the abnormality determination unit 51 may simply determine whether an abnormal state exists based on the temporal changes 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 an abnormal state when the concentration of the specified gas exceeds a specified threshold. For example, when the specified gas is carbon monoxide, the specified threshold is 700 ppm, and when the specified gas is carbon dioxide, the specified threshold is 800 ppm. However, to appropriately determine whether an abnormal state exists, it is preferable that the abnormality determination unit 51 determine whether an abnormal state exists as in the present embodiment. Alternatively, the abnormality determination unit 51 may determine an abnormal state based on, for example, the difference between the concentration of the specified gas and the median value of the concentration of the specified gas immediately before the measurement of the concentration of the specified gas, the difference between the concentration of the specified gas and the value obtained by subtracting the standard deviation from the mean value of the concentration of the specified gas immediately before the measurement of the concentration of the specified gas, or the difference between the concentration of the specified gas and the minimum value of the concentration of the specified gas immediately before the measurement of the concentration of the specified gas. In this case, the abnormality determination unit 51 may determine an abnormal state if these differences are greater than or equal to a predetermined value, which is set based on experiments or other factors for each difference. Alternatively, the abnormality determination unit 51 may determine an abnormal state if the concentration of the specified gas continuously increases by a predetermined amount or more over a predetermined period of time. Furthermore, a state such as a defective optical fiber 1 is considered an abnormal state. Therefore, similar to the optical fiber defect determination unit 52 of the above-described embodiment, the abnormality determination unit 51 may determine an abnormal state if the difference between the carbon monoxide concentration measured by the gas measurement unit 48 during heating of the glass member and the initial carbon monoxide concentration exceeds 550 ppm.

[0094] In the above embodiment, the optical fiber failure determination unit 52 is described as an example. This optical fiber failure 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 during heating of the core porous glass body 20 and the initial carbon monoxide concentration exceeds 400 ppm. However, the optical fiber failure determination unit 52 may simply determine whether an abnormal state is present based on the temporal change in the concentration of a predetermined gas measured by the gas measurement unit 48. For example, the optical fiber failure determination unit 52 may output a signal indicating a defect in the optical fiber 1 when the concentration of the predetermined gas exceeds a predetermined threshold. For example, when the predetermined gas is carbon monoxide, the predetermined threshold is 700 ppm, and when the predetermined gas is carbon dioxide, the predetermined threshold is 800 ppm. Furthermore, in the above embodiment, the optical fiber failure determination unit 52 determines whether the optical fiber 1 is defective based on the temporal change in the concentration of the predetermined gas measured in the first heating step P2. Here, if water intrudes into the storage space 31S during sintering of the porous glass body forming the cladding 11 of the optical fiber 1, the characteristics of the finally manufactured optical fiber 1, namely, the transmission loss, will deteriorate. The greater the amount of water that intrudes into the storage space 31S, the worse the transmission loss tends to be. Therefore, the optical fiber defect determination unit 52 may determine whether the optical fiber 1 is defective based on the temporal change in the concentration of the predetermined gas measured in the second heating step P4. In this case, the threshold value of the predetermined gas concentration used to determine whether the optical fiber 1 is defective is set based on experimental values, etc.

[0095] In the above embodiment, the furnace body 35 is described as an example that surrounds 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 surround the entire furnace core tube 31, for example.

[0096] In addition, in the above embodiment, the dehydration sintering device 100 having the second gas supply part 42 is described as an example. However, the dehydration sintering device 100 may not have the second gas supply part 42. For example, the second gas supply part 42 may be replaced by an exhaust part, which exhausts the air in the space 35S from the exhaust pipe 46 to make the space 35S a vacuum state. By making the space 35S a vacuum state in this way, the combustion of the heater 37, the insulation material 38, etc. in the space 35S can be suppressed. In addition, in the above embodiment, the furnace body 35 having a cooling function using cooling water is described as an example, but there is no particular limitation on the cooling method of the furnace body 35. If the furnace body 35 has sufficient heat resistance, the furnace body 35 may not have a cooling function. In addition, in the above embodiment, the concentration of the specified gas is measured for the space 35S of the furnace body 35, but it is not limited to this.

[0097] In the above embodiment, the first deposition step P1, which forms the core porous glass body 20 serving as the core glass body 10P, is described as an example. However, the porous glass body formed by the first deposition step P1 is not particularly limited; for example, it may be a porous glass body that forms part of the core glass body 10P and the cladding glass body 11P. In this case, in the second deposition step P3, glass particles are deposited on the outer surface of the glass rod formed in the first sintering step P2b to form a porous glass body serving as another part of the cladding glass body 11P.

[0098] In the above embodiment, a method for manufacturing an optical fiber base material 1P including a first stacking step P1, a first heating step P2, a second stacking step P3, and a second heating step P4 is described as an example. However, the method for manufacturing an optical fiber base material 1P only needs to include a heating step for heating a porous glass body serving as a glass component using the above-described heating method for a glass component. For example, the method for manufacturing an optical fiber base material 1P may not include the first stacking step P1 and the first heating step P2. In this case, for example, in the second stacking step P3, a core glass rod is first prepared by procurement, and glass particles are stacked on the outer circumference of the core glass rod to form a porous glass body for the cladding.

[0099] In addition, in the above embodiment, the first sintering step P2b and the second sintering step P4b are described as an example. In the first sintering step P2b and the second sintering step P4b, the first gas is set to a mixed gas of a dehydration gas and an inert gas, and the porous glass body is heated in a state where the first gas is supplied from the first gas supply part 41 to the storage space 31S. However, in the first sintering step P2b and the second sintering step P4b, the porous glass body can also be heated in a state where only an inert gas is supplied to the storage space 31S. In this case, for example, the first gas supply part 41 can be configured so that the supplied first gas can be changed between a gas containing a dehydration gas and an inert gas and an inert gas alone. In addition, the control unit 60 controls the first gas supply part 41 in a manner that switches the first gas supplied from the first gas supply part 41 according to the process.

[0100] In addition, in the above embodiment, the core porous glass body 20 is heated using 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 using 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 using different dehydration and sintering devices 100 in each step. In addition, the method for manufacturing the optical fiber base material 1P may further include an extension step in which the glass body formed by sintering the core porous glass body 20 in the first heating step P2 is extended to obtain a core glass rod. In addition, the furnace core tube 31 only needs to have a storage space 31S for accommodating at least a portion of the glass component, and openings may be formed at both ends of the furnace core tube 31. For example, the device for extending the glass body, the spinning furnace for heating the optical fiber base material 1P, and the front-end processing furnace are also included in the glass component heating device of the present invention.

[0101] The present invention will be described in more detail below with reference to experimental examples, but the present invention is not limited thereto.

[0102] use Figure 4 The dehydration sintering device 100 shown in FIG. Figure 3 The first stacking step P1 and the first heating step P2 shown were repeated 32 times, producing 32 core glass rods. In this dehydration and sintering apparatus 100, the heater 37 was not heated from the time the furnace body 35 was installed until the first core glass rod was produced. Furthermore, the gas measurement unit 48 was used to measure the concentrations of carbon monoxide and carbon dioxide in the space 35S in the initial state from the time the furnace body 35 was installed until the first heating step P2 for producing the first core glass rod. The initial carbon monoxide concentration was 150 ppm, and the carbon dioxide concentration was 260 ppm. Furthermore, the gas measurement unit 48 was used to measure the concentrations of carbon monoxide and carbon dioxide in the space 35S during the first heating step P2 for producing each core glass rod. Figure 5 The measurement results are shown in Figure 2. Figure 5 The transmission loss which will be described later is also shown.

[0103] In addition, another dehydration sintering device 100 is used to carry out Figure 3 The second stacking step P3 and the second heating step P4 are shown, thereby using these core glass rods to manufacture the same Figure 2The optical fiber preform 1P shown in FIG. During the second heating step P4 during the manufacture of each optical fiber preform 1P, the concentrations of carbon monoxide and carbon dioxide in the space 35S were measured using the gas measuring unit 48. The carbon monoxide concentration was between 150 ppm and 250 ppm, and the carbon dioxide concentration was between 250 ppm and 400 ppm. Furthermore, after the manufacture of the optical fiber preform 1P, the space 35S was checked to determine that no water had intruded into the space 35S.

[0104] In addition, the 32 optical fiber base materials 1P produced were heated and drawn using a spinning furnace, thereby producing the same optical fiber base materials as those used in the present invention. Figure 1 The optical fiber 1 shown is the same optical fiber 1. The diameter of the core 10 in each optical fiber 1 is approximately 10 μm, and the diameter of the cladding 11 is approximately 125 μm. In addition, the transmission loss of 1383 nm wavelength light was measured for each optical fiber 1 using an OTDR (Optical Time Domain Reflectometer). The measurement results are as described above. Figure 5 In addition, Figure 5 The dashed line in FIG indicates a transmission loss value of 0.31 dB / km, which is generally required for an optical fiber for long-distance transmission.

[0105] like Figure 5As shown, the transmission loss of optical fiber 1 manufactured using the first to 27 core glass rods is approximately 0.28 dB / km, while the transmission loss of optical fiber 1 manufactured using the 28th core glass rod is 0.309 dB / km. The transmission loss of optical fiber 1 manufactured using the 29th and subsequent core glass rods exceeds 0.31 dB / km, and the transmission loss tends to increase with the number of core glass rods. Furthermore, during the manufacture of the first to 28th core glass rods, the carbon monoxide concentration was highest in the 28th core glass rod, at 397 ppm. Furthermore, the carbon dioxide concentration was highest in the 28th core glass rod, at 448 ppm. The carbon monoxide concentration in the 29th core glass rod was 703 ppm, and the carbon dioxide concentration in the 29th core glass rod was 813 ppm. The carbon monoxide and carbon dioxide concentrations increased with the number of core glass rods. Therefore, it is believed that water begins to intrude into space 35S when the 28th fiber is manufactured, and the amount of water intruding into space 35S increases as the number of fibers increases after the 28th fiber. Furthermore, as mentioned above, the carbon monoxide concentration in the initial state is 150 ppm, and the carbon dioxide concentration is 260 ppm. Therefore, it can be seen that if the difference between the carbon monoxide concentration when the porous glass body 20 for the core, which serves as a glass component, is heated and the carbon monoxide concentration in the initial state from the time the furnace body 35 is installed until the first heating of the porous glass body 20 for the core, exceeds 550 ppm, then optical fiber 1 is defective. Furthermore, it can be seen that if the difference between the carbon dioxide concentration when the porous glass body 20 for the core is heated and the carbon dioxide concentration in the initial state exceeds 550 ppm, then optical fiber 1 is defective. Furthermore, it can be seen that if the carbon monoxide concentration is above 700 ppm and the carbon dioxide concentration is above 800 ppm, then optical fiber 1 is defective. Furthermore, when water reacts with carbon, methane, oxygen, and hydrogen are also produced along with carbon monoxide and carbon dioxide. The production of methane, oxygen, and hydrogen tends to be stoichiometrically proportional to the production of carbon monoxide and carbon dioxide. Therefore, reference values ​​for determining whether the optical fiber 1 is defective can be set based on experimental values ​​or the like for each concentration of methane, oxygen, and hydrogen.

[0106] In addition, for the 1st to 28th roots, the difference between the carbon monoxide concentration and the average value of the carbon monoxide concentration measured before the carbon monoxide was measured was 500 ppm or less. In addition, for the 29th root, the difference was 506 ppm. Therefore, it can be seen that when the difference is 500 ppm or more, the dehydration and sintering device 100 is in an abnormal state. In addition, for the 1st to 28th roots, the difference between the carbon dioxide concentration and the average value of the carbon dioxide concentration measured before the carbon dioxide was measured was 550 ppm or less. In addition, for the 29th root, the difference was 553 ppm. Therefore, it can be seen that when the difference is 550 ppm or more, the dehydration and sintering device 100 is in an abnormal state. In addition, when the carbon monoxide concentration is 700 ppm or more and the carbon dioxide concentration is 800 ppm or more, the dehydration and sintering device 100 is in an abnormal state. In addition, as described above, the production of methane, oxygen, and hydrogen tends to be proportional to the production of carbon monoxide and carbon dioxide. Therefore, for the concentrations of methane, oxygen, and hydrogen, a reference value for determining whether the dehydration sintering device 100 is in an abnormal state can be set based on experimental values, etc.

[0107] As described above, a glass component heating device and a glass component heating method, and an optical fiber base material manufacturing method using the same, which are capable of detecting abnormal conditions caused by water, can be provided, and can be applied to fields such as optical fiber communications.

Claims

1. A heating device for a glass component, characterized in that: have: a furnace core tube, which is a cylindrical member extending in the vertical direction and has a storage space capable of storing at least a portion of the glass member; a furnace body in a hollow box shape, having a through hole extending vertically through the furnace body at its center and surrounding at least a portion of the furnace core tube inserted into the through hole; a heater disposed in a space surrounded by the furnace core tube and the furnace body; Gas Measurement Department; as well as an exhaust pipe connected to an exhaust port formed in the furnace body and communicating with a space surrounded by the furnace core tube and the furnace body, The upper end and the lower end of the furnace core tube protrude from the furnace body respectively, and the furnace body surrounds a portion of the furnace core tube. At least one of the components disposed in the space surrounded by the furnace core tube and the furnace body contains carbon, The gas measuring unit is mounted on the furnace body or the exhaust pipe and is capable of measuring the concentration of gas generated by the reaction between water and carbon in a space surrounded by the furnace core tube and the furnace body.

2. The glass component heating device according to claim 1, characterized in that The gas is at least one of carbon monoxide, carbon dioxide, methane, and hydrogen.

3. The glass component heating device according to claim 1 or 2, characterized in that: The furnace body has a flow path for cooling water to flow.

4. The glass component heating device according to claim 1 or 2, characterized in that: A gas supply unit is further provided for supplying an inert gas to the space surrounded by the furnace core tube and the furnace body from a gas supply port formed in the furnace body and communicating with the space surrounded by the furnace core tube and the furnace body.

5. The glass component heating device according to claim 1 or 2, characterized in that: The gas measuring unit measures the concentration of the gas based on the exhaust gas discharged into the exhaust pipe from an exhaust port formed in the furnace body and communicating with a space surrounded by the furnace core tube and the furnace body.

6. The glass component heating device according to claim 1 or 2, characterized in that: The device further includes an abnormality determination unit configured to determine whether or not an abnormal state exists based on a temporal change in the concentration of the gas measured by the gas measurement unit.

7. The glass component heating device according to claim 6, characterized in that 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 concentration of the gas is measured is equal to or greater than a predetermined value.

8. The glass component heating device according to claim 1 or 2, characterized in that: It also has a fiber optic defect judgment unit. The glass component is a porous glass body that becomes a part of the optical fiber, The optical fiber failure determination unit determines whether the optical fiber is defective based on a temporal change in the concentration of the gas measured by the gas measurement unit.

9. The glass component heating device according to claim 8, characterized in that: The gas is carbon monoxide, The glass member is a porous glass body that becomes the core of the optical fiber. The optical fiber failure determination unit determines 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 from the installation of the furnace body to the first heating of the glass member exceeds 550 ppm.

10. A heating device for a glass component, characterized in that: have: a furnace core tube, which is a cylindrical member extending in the vertical direction and has a storage space capable of storing at least a portion of the glass member; a furnace body in a hollow box shape, having a through hole extending vertically through the furnace body at its center and surrounding at least a portion of the furnace core tube inserted into the through hole; a heater disposed in a space surrounded by the furnace core tube and the furnace body; as well as Gas Measurement Department, The upper end and the lower end of the furnace core tube protrude from the furnace body respectively, and the furnace body surrounds a portion of the furnace core tube. At least one of the components disposed in the space surrounded by the furnace core tube and the furnace body contains carbon, The gas measuring unit is capable of measuring the concentration of gas generated by the reaction between water and carbon in the space surrounded by the furnace core tube and the furnace body, and measuring the concentration of the gas based on exhaust gas discharged from an exhaust port formed in the furnace body and connected to the space surrounded by the furnace core tube and the furnace body.

11. The glass component heating device according to claim 10, characterized in that: The gas is at least one of carbon monoxide, carbon dioxide, methane, and hydrogen.

12. The glass component heating device according to claim 10 or 11, characterized in that: The furnace body has a flow path for cooling water to flow.

13. The glass component heating device according to claim 10 or 11, characterized in that: A gas supply unit is further provided for supplying an inert gas to the space surrounded by the furnace core tube and the furnace body from a gas supply port formed in the furnace body and communicating with the space surrounded by the furnace core tube and the furnace body.

14. The glass component heating device according to claim 10 or 11, characterized in that: The device further includes an abnormality determination unit configured to determine whether or not an abnormal state exists based on a temporal change in the concentration of the gas measured by the gas measurement unit.

15. The glass component heating device according to claim 14, characterized in that: 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 concentration of the gas is measured is equal to or greater than a predetermined value.

16. The glass component heating device according to claim 10 or 11, characterized in that: It also has a fiber optic defect judgment unit. The glass component is a porous glass body that becomes a part of the optical fiber, The optical fiber failure determination unit determines whether the optical fiber is defective based on a temporal change in the concentration of the gas measured by the gas measurement unit.

17. The glass component heating device according to claim 16, characterized in that: The gas is carbon monoxide, The glass member is a porous glass body that becomes the core of the optical fiber. The optical fiber failure determination unit determines 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 from the installation of the furnace body to the first heating of the glass member exceeds 550 ppm.

18. A method for heating a glass component, comprising: housing at least a portion of the glass component in a housing space within a furnace core tube at least partially surrounded by a furnace body; and heating the glass component using a heater disposed in the space surrounded by the furnace core tube and the furnace body, wherein: The furnace body is in the shape of a hollow box and has a through hole formed in the center thereof which passes through in the vertical direction. The furnace core tube is a cylindrical component extending in the vertical direction and is inserted into the furnace body. The furnace core tube is characterized in that: The upper end and the lower end of the furnace core tube protrude from the furnace body respectively, and the furnace body surrounds a portion of the furnace core tube. At least one of the components disposed in the space surrounded by the furnace core tube and the furnace body contains carbon, An exhaust pipe is connected to an exhaust port formed in the furnace body and communicating with a space surrounded by the furnace core tube and the furnace body. The glass member is heated by the heater, and the concentration of gas generated by the reaction between water and carbon in a space surrounded by the furnace core tube and the furnace body is measured by a gas measuring unit installed in the furnace body or the exhaust pipe.

19. The method for heating a glass component according to claim 18, wherein: The gas is at least one of carbon monoxide, carbon dioxide, methane, and hydrogen.

20. The method for heating a glass component according to claim 18 or 19, wherein: The furnace body has a flow path for cooling water to flow.

21. The method for heating a glass component according to claim 18 or 19, wherein: When the glass member is heated, an inert gas is supplied to the space surrounded by the furnace core tube and the furnace body from a gas supply port formed in the furnace body and communicating with the space surrounded by the furnace core tube and the furnace body.

22. The method for heating a glass component according to claim 18 or 19, wherein: The concentration of the gas is measured based on the exhaust gas exhausted to the exhaust pipe from an exhaust port formed in the furnace body and communicating with a space surrounded by the furnace core tube and the furnace body.

23. The method for heating a glass component according to claim 18 or 19, wherein: Whether or not the state is abnormal is determined based on the measured temporal change in the concentration of the gas.

24. The method for heating a glass component according to claim 23, wherein: When the difference between the measured concentration of the gas and the average value of the concentration of the gas measured before the concentration of the gas is measured is equal to or greater than a predetermined value, it is determined that an abnormal state exists.

25. A method for manufacturing an optical fiber base material, characterized in that: The method further comprises a heating step of heating a porous glass body serving as a part of an optical fiber as the glass member by using the glass member heating method according to any one of claims 18 to 24.

26. The method for manufacturing an optical fiber base material according to claim 25, wherein: Whether the optical fiber is defective is determined based on a temporal change in the concentration of the gas measured during the heating step.

27. The method for manufacturing an optical fiber base material according to claim 26, wherein: The gas is carbon monoxide, The porous glass body is a porous glass body that becomes the core of the optical fiber, If the difference between the gas concentration measured in the heating step and the gas concentration in the initial state from the time the furnace is installed to the time the porous glass body is first heated exceeds 550 ppm, the optical fiber is determined to be defective.

28. A method for heating a glass component, comprising: housing at least a portion of the glass component in a housing space within a furnace core tube at least partially surrounded by a furnace body, and heating the glass component using a heater disposed in the space surrounded by the furnace core tube and the furnace body, wherein: The furnace body is in the shape of a hollow box and has a through hole formed in the center thereof which passes through in the vertical direction. The furnace core tube is a cylindrical component extending in the vertical direction and is inserted into the furnace body. The furnace core tube is characterized in that: The upper end and the lower end of the furnace core tube protrude from the furnace body respectively, and the furnace body surrounds a portion of the furnace core tube. At least one of the components disposed in the space surrounded by the furnace core tube and the furnace body contains carbon, The glass member is heated by the heater, and the concentration of gas generated by the reaction between water and carbon in the space surrounded by the furnace core tube and the furnace body is measured based on exhaust gas exhausted from an exhaust port formed in the furnace body and communicating with the space surrounded by the furnace core tube and the furnace body.

29. The method for heating a glass component according to claim 28, wherein: The gas is at least one of carbon monoxide, carbon dioxide, methane, and hydrogen.

30. The method for heating a glass component according to claim 28 or 29, wherein: The furnace body has a flow path for cooling water to flow.

31. The method for heating a glass component according to claim 28 or 29, wherein: When the glass member is heated, an inert gas is supplied to the space surrounded by the furnace core tube and the furnace body from a gas supply port formed in the furnace body and communicating with the space surrounded by the furnace core tube and the furnace body.

32. The method for heating a glass component according to claim 28 or 29, wherein: Whether or not the state is abnormal is determined based on the measured temporal change in the concentration of the gas.

33. The method for heating a glass component according to claim 32, wherein: When the difference between the measured concentration of the gas and the average value of the concentration of the gas measured before the concentration of the gas is measured is equal to or greater than a predetermined value, it is determined that an abnormal state exists.

34. A method for manufacturing an optical fiber base material, characterized in that: A heating step is provided in which a porous glass body serving as a part of an optical fiber as the glass member is heated by the glass member heating method according to any one of claims 28 to 33.

35. The method for manufacturing an optical fiber base material according to claim 34, wherein: Whether the optical fiber is defective is determined based on a temporal change in the concentration of the gas measured during the heating step.

36. The method for manufacturing an optical fiber base material according to claim 35, wherein: The gas is carbon monoxide, The porous glass body is a porous glass body that becomes the core of the optical fiber, If the difference between the gas concentration measured in the heating step and the gas concentration in the initial state from the time the furnace is installed to the time the porous glass body is first heated exceeds 550 ppm, the optical fiber is determined to be defective.

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