JP2022179164A - Apparatus and method for heating glass member, and method for manufacturing optical fiber preform using the same - Google Patents

Abstract

To provide an apparatus and method for heating a glass member, capable of detecting an abnormal state due to water, and a method for manufacturing an optical fiber preform using the same.SOLUTION: A dehydration sintering apparatus 100 used as an apparatus for heating a glass member includes: a furnace core tube 31 having a storage space 31S capable of storing a core porous glass body 20 used as the glass member; a furnace body 35 surrounding a part of the furnace core tube 31; a heater 37 arranged in a space 35S surrounded by the furnace core tube 31 and the furnace body 35; and a gas measurement part 48. Carbon is included in at least one of members arranged in the space 35S; and the gas measurement part 48 can measure the concentration of gas generated due to a reaction of water with carbon in the space.SELECTED DRAWING: Figure 4

Description

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

As a method for manufacturing an optical fiber preform used for manufacturing an optical fiber, the OVD method (Outside Vapor Deposition method), the VAD method (Vapor Phase Axial Deposition method), etc. are used to deposit glass particles to form a porous glass body. It is known to form and heat the porous glass body to sinter it.

Patent Literature 1 listed below discloses a heating device for heating a porous glass body. This heating device includes a furnace core tube having a housing space for housing a porous glass body, a heater arranged outside the furnace core tube, a furnace body surrounding a part of the furnace core tube and the heater, and a gas detector. Prepare. This gas detector detects leakage gas that leaks from a furnace core tube into a space surrounded by the furnace core tube and the furnace body and is discharged from an exhaust port provided in the furnace body. Therefore, according to this heating apparatus, it is said that damage such as cracking of the core tube can be detected by the gas detector.

JP 2015-48262 A

Incidentally, the furnace body of the heating apparatus as described above is sometimes cooled by cooling water, and if the furnace body is damaged, the cooling water may enter the space surrounded by the core tube and the furnace body. In addition, inert gas may be supplied to this space to suppress combustion of the members arranged in the space, and water may enter this space together with the inert gas due to a malfunction of the gas supply device, etc. . The furnace core tube is generally made of quartz, carbon, or the like, and in such an abnormal state that water enters the above-mentioned space, water permeates from the space into the housing space of the furnace core tube even if the furnace core tube is not damaged. Sometimes. If water enters the housing space while the porous glass body is being heated and sintered by the heater, the transmission loss and the like, which are the characteristics of the finally manufactured optical fiber, may deteriorate.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a glass member heating apparatus, a glass member heating method, and an optical fiber preform manufacturing method using the same, which are capable of detecting an abnormal state caused by water.

To achieve the above object, the present invention provides a heating apparatus for a glass member comprising: a furnace core tube having a housing space capable of housing at least a portion of a glass member; a furnace body surrounding at least a portion of the furnace core tube; a heater arranged in a space surrounded by the pipe and the furnace body; and a gas measurement unit, at least one of the members arranged in the space contains carbon, and the gas measurement unit It is characterized in that it is possible to measure the concentration in the space of the gas generated due to the reaction between the carbon and the carbon.

Further, in order to achieve the above object, the present invention provides a storage space in a furnace core tube at least partially surrounded by a furnace body, in which at least part of a glass member is housed in the space surrounded by the furnace core tube and the furnace body. wherein at least one of the members arranged in the space contains carbon, and while the heater heats the glass member, It is characterized by measuring the concentration in the space of the gas generated due to the reaction between water and carbon.

When the glass member is dehydrated, sintered, melted, etc., the heater is generally heated to 700° C. or higher. When water enters the space in such a high temperature state, the water reacts with the carbon contained in the member placed in the space to generate gas. With this glass member heating apparatus and glass member heating method, the concentration of the gas generated in this manner can be measured, so that an abnormal state in which water has entered the above space can be detected.

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.

With such a configuration, damage to the furnace body due to heat can be suppressed. In addition, since the gas measurement unit can measure the concentration of the gas generated by the reaction between water and carbon in the space, damage to the furnace body such as cooling water entering the space can be detected. can.

The apparatus for heating a glass member may further include a gas supply unit configured to supply an inert gas to the space from an air supply port formed in the furnace body and communicating with the space.

With such a configuration, it is possible to suppress combustion of the members arranged in the space. In addition, since the gas measurement unit can measure the concentration of the gas generated due to the reaction between water and carbon in the space, the gas supply unit allows water to enter the space together with the inert gas. It can detect defects such as pipes and pipes.

In the above-described glass member heating apparatus, the gas measurement unit may measure the concentration of the gas from exhaust gas discharged from an exhaust port formed in the furnace body and communicating with the space.

By adopting such a configuration, compared with the case of measuring the concentration of the gas at a certain point in the space, it is possible to suppress the influence of the location where the gas is generated in the space on the concentration of the gas. Therefore, an abnormal state in which water has entered the space can be detected more accurately than in the above case.

The apparatus for heating a glass member 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, the abnormality determination unit comprising: and a difference between the concentration of the gas measured by the gas measuring unit and an average value of the concentrations of the gas measured by the gas measuring unit before the timing at which the concentration of the gas is measured is equal to or greater than a predetermined value. case, it may be determined to be in an abnormal state.

Even if the furnace body has the same configuration, the concentration of the gas measured in the steady state tends to vary depending on the installation state of the furnace body. Therefore, by adopting the configuration as described above, it is possible to appropriately determine whether or not an abnormal state exists, compared to the case where it is determined that an abnormal state has occurred when the gas concentration is equal to or higher than a predetermined value.

The above glass member heating apparatus further includes a fiber defect determination section, the glass member is a porous glass body that becomes a part of the optical fiber, and the fiber defect determination section is measured by the gas measurement section. Whether or not the optical fiber becomes defective may be determined based on the change in concentration of the gas with time.

As described above, if water enters the housing space while the porous glass body is being sintered, the transmission loss, which is the characteristic of the finally manufactured optical fiber, may deteriorate. The characteristics tend to deteriorate as the amount of intruding water increases. Such intrusion of water into the housing 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 or not the properties of the finally manufactured optical fiber are deteriorated and the optical fiber becomes defective based on the appearance of the transparent glass member. However, as the amount of water entering the housing space increases, the amount of gas generated due to the reaction between water and carbon increases, and the concentration of this gas increases. Therefore, by adopting the above configuration, it is possible to determine whether or not the optical fiber finally manufactured will be defective at the stage of manufacturing the transparent glass member, and the defect rate of the optical fiber can be determined. can be reduced and the productivity of the optical fiber can be improved.

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 section is configured to measure the gas measured by the gas measurement section. If the difference between the concentration and the concentration of the gas in the initial state before the glass member is heated for the first time after the furnace body is installed exceeds 550 ppm, it may be determined that the optical fiber is defective. good.

The present inventor found that when the difference between the concentration of carbon monoxide during heating of the porous glass body serving as the core and the concentration of carbon monoxide in the initial state exceeds 550 ppm, the porous glass body It has been found that an optical fiber manufactured from an optical fiber preform containing a core glass body composed of is defective. Therefore, by adopting such a configuration, it is possible to appropriately predict whether or not the finally manufactured optical fiber will be defective.

A method of manufacturing an optical fiber preform according to the present invention is characterized by comprising a heating step of heating the porous glass body as the glass member by the method for heating the glass member described above.

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

It is a figure which shows roughly the appearance of the cross section perpendicular|vertical to the longitudinal direction of the optical fiber which concerns on embodiment of this invention. FIG. 2 is a diagram schematically showing 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 flow chart showing steps of an optical fiber preform manufacturing method and an optical fiber manufacturing method according to an embodiment of the present invention. It is a figure which shows roughly the dehydration-sintering apparatus used by a 1st heating process. FIG. 5 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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus for heating a glass member, a method for heating a glass member, and a method for manufacturing an optical fiber preform using the same according to the present invention will be exemplified with accompanying drawings. The embodiments illustrated below are intended to facilitate understanding of the present invention, and are not intended to limit and interpret the present invention. The present invention can be modified and improved without departing from its spirit. Note that in the drawings referred to below, the dimensions of each member may be changed to facilitate understanding.

FIG. 1 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. As shown in FIG. 1, the optical fiber 1 of this embodiment mainly includes a core 10, a clad 11 surrounding the outer peripheral surface of the core 10, and a coating layer 12 covering the outer peripheral surface of the clad 11. The outer shape of the core 10 in the cross section is circular, and the core 10 is arranged at the center of the clad 11 . In addition, the outer shape of the clad 11 in the cross section may be non-circular such as elliptical or polygonal. FIG. 1 shows an optical fiber 1 in which the outer shape of the cladding 11 is circular.

The core 10 has a higher refractive index than the clad 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 clad 11 is made of silica glass without any additives. The core 10 may be made of silica glass without any additives, and the clad 11 may be made of silica glass doped with a dopant such as fluorine (F) that lowers the refractive index. Alternatively, the core 10 may be made of silica glass doped with a dopant that increases the refractive index, and the clad 11 may be made of silica glass doped with a dopant that lowers the refractive index. Moreover, the dopant for increasing the refractive index and the dopant for decreasing the refractive index are not particularly limited.

The covering layer 12 is made of resin. Examples of the resin forming the coating layer 12 include thermosetting resins and ultraviolet curable resins. The coating layer 12 may have a single-layer structure consisting of one resin layer surrounding the clad 11, or may have a multi-layer structure consisting of a plurality of resin layers.

FIG. 2 is a diagram schematically showing a cross section perpendicular to the longitudinal direction of the optical fiber preform for manufacturing the optical fiber 1 shown in FIG. As shown in FIG. 2, the optical fiber preform 1P is composed of a rod-shaped core glass body 10P that serves as the core 10, and a clad glass body 11P that surrounds the outer peripheral surface of the core glass body 10P and serves as the clad 11. . In this embodiment, the outer shape of the clad glass body 11P in the cross section is circular, and the core glass body 10P is arranged at the center of the clad glass body 11P. Moreover, the outer shape of the core glass body 10P in the cross section is circular.

Next, a method for manufacturing an optical fiber preform according to this embodiment will be described.

FIG. 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 FIG. 3, the method of manufacturing the optical fiber preform 1P of the present embodiment includes a first deposition step P1, a first heating step P2, a second deposition step P3, a second heating step P4, Prepare.

<First Deposition Process P1>
This step is a step of depositing glass fine particles to form a porous glass body for the core, which will be the core glass body 10P shown in FIG. A porous glass body can be formed by a soot method such as an OVD method or a VAD method. In this embodiment, the porous glass body for the core is formed by depositing the glass particles along the axial direction of the glass rod from one end of the prepared glass rod by the VAD method.

<First heating step P2>
This step is a step of heating the core porous glass body as the glass member formed in the first deposition step P1, and as shown in FIG. including. First, a dehydration sintering apparatus as a heating apparatus for a glass member used in this step will be described.

FIG. 4 is a diagram schematically showing a dehydration sintering apparatus used in the first heating step P2. As shown in FIG. 4, the dehydration sintering apparatus 100 of the present embodiment includes a heating furnace 30, an elevating unit 40, a first gas supply unit 41, a second gas supply unit 42, a gas measurement unit 48, A determination unit 50, a memory 55, a notification unit 56, and a control unit 60 are provided as main components.

The control unit 60 includes, for example, a microcontroller, an integrated circuit such as an IC (Integrated Circuit), an LSI (Large-scale Integrated Circuit), an ASIC (Application Specific Integrated Circuit), and an NC (Numerical Control) device. Further, when the NC device is used, the control unit 60 may use a machine learning device or may not use a machine learning device. Several configurations of the dehydration-sintering apparatus 100 are controlled by the controller 60 as described below.

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

The furnace core tube 31 of the present embodiment is a cylindrical member that extends vertically, and can accommodate the core porous glass body 20 in the accommodation space 31S. In this embodiment, the openings at both ends of the core tube 31 are closed, and the part closing the upper opening is removable from other parts. A through hole for inserting a support rod 22 for suspending the core porous glass body 20 is formed in a portion of the furnace core tube 31 that closes the upper opening. A connection portion 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 portion 23 . The furnace core tube 31 is formed with an exhaust port E1 and an air supply port S1 respectively communicating with the housing space 31S. Examples of the material forming the core tube 31 include quartz and carbon.

The furnace body 35 of this embodiment is formed in the shape of a hollow box, 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 in the flow path 36 cools the furnace body 35 and suppresses damage to the furnace body 35 due to heat. Further, a through hole is formed in the central portion of the furnace body 35 so as to penetrate vertically, and the furnace core tube 31 is inserted into the through hole. The upper end and the lower end of the furnace core tube 31 each protrude from the furnace body 35, and the furnace body 35 surrounds the central part of the furnace core tube 31 in the vertical direction. is formed. Further, the furnace body 35 is formed with an air supply port S2 and an exhaust port E2 communicating with the space 35S. The air supply port S2 is positioned on one side in the horizontal direction with respect to the core tube 31, and the exhaust port E2 is positioned on the other side. Examples of the material that constitutes the furnace body 35 include metal.

The heater 37 is arranged in the space 35S so as to heat the core porous glass body 20 housed in the housing 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 . may be arranged discontinuously so as to surround the The heater 37 adjusts the heat generation temperature according to the control signal from the controller 60 . In order to effectively use 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 insulators 38 is not particularly limited, and the heat insulators 38 may be divided into a plurality of pieces. The heat insulating material 38 of this embodiment is made of carbon. Therefore, in this embodiment, the heater 37 and the heat insulating material 38, which are members arranged in the space 35S, contain carbon. At least one of the members arranged in the space 35S may contain carbon. The material 38 may not be provided.

The elevating unit 40 elevates the supporting rod 22 to be gripped. The elevating unit 40 elevates the supporting rods 22 in accordance with a control signal from the control unit 60 to vertically move the core porous glass bodies 20 attached to the supporting rods 22 . In addition, the structure of the raising/lowering part 40 is not specifically restricted.

The first gas supply unit 41 supplies a first gas containing a dehydration gas to the accommodation space 31S through a pipe 43 connected to the air supply port S1 of the core tube 31 . The first gas supply unit 41 adjusts the supply amount of the first gas according to the control signal from the control unit 60 . The first gas supplied to the housing space 31S is exhausted from the exhaust port E1 of the core tube 31 to the exhaust pipe 44. As shown in FIG. In this embodiment _, the first gas _is a mixed gas of a dehydration gas and an _inert gas. Chlorine-based gases and carbon monoxide can be used, and inert gases such as He, Ar, and N ₂ can be used.

The second gas supply unit 42 supplies the second gas, which is an inert gas, to the space 35S through the pipe 45 connected to the air supply port S2 of the furnace body 35. As shown in FIG. The second gas supply unit 42 adjusts the supply amount of the second gas according to the 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 . Examples of the second gas include He, Ar, _N2 , and the like.

In this embodiment, the gas measurement unit 48 is attached to the exhaust pipe 46, measures the concentration of a predetermined gas in the exhaust gas discharged from the exhaust port E2, and outputs a signal indicating the measured concentration of the predetermined gas. Output to the determination unit 50 . The gas measurement unit 48 intermittently or continuously repeats this measurement and output. The predetermined gas is gas generated due to the reaction between water and carbon. As described above, at least one of the members arranged in the space 35S contains carbon. For this reason, when water enters the space 35S when the temperature of the space 35S is a temperature at which water and carbon react, for example, 700° C. or higher, carbon contained in the members arranged in the water and the space 35S can react to generate a predetermined gas. In addition, it is considered that in a high-temperature state where water and carbon react, water decomposes into hydrogen atoms and oxygen atoms, and the hydrogen atoms and oxygen atoms react with carbon. Predetermined gases include, for example, carbon monoxide, carbon dioxide, methane, oxygen, and hydrogen, and the gas measurement unit 48 is configured to be able to measure the concentration of at least one of these gases. Examples of sensors that measure the concentration of carbon monoxide include a constant potential electrolysis sensor, and examples of sensors that measure the concentration of carbon dioxide include a non-dispersive infrared sensor that measures the concentrations of methane and hydrogen. For example, a semiconductor laser absorption spectroscopic sensor can be used for measurement, and a zirconia concentration cell type sensor can be used for oxygen concentration measurement. The gas measuring unit 48 of the present embodiment can measure the concentration of carbon monoxide. The gas measurement unit 48 may be installed on the furnace body 35 as long as it can measure the concentration of the predetermined gas in the space 35S.

The determination unit 50 of the present embodiment stores the concentration of the predetermined gas measured by the gas measurement unit 48 in the memory 55, and determines whether the dehydration sintering apparatus 100 is in an abnormal state based on the temporal change in the concentration of the predetermined gas. It is determined whether or not there is, and whether or not the manufactured optical fiber will be defective. As a configuration of the determination unit 50, for example, a configuration similar to that of the control unit 60 can be given.

The memory 55 is, for example, a non-transitory recording medium, and is preferably a semiconductor recording medium such as a RAM (Random Access Memory) or a ROM (Read Only Memory). Any form of recording medium, such as a recording medium, may be included. In this embodiment, the memory 55 stores programs and information for executing these determination processes. The judging section 50 reads a program and information from the memory 55, has an abnormality judging section 51 and a fiber failure judging section 52 in this state, and executes the judgment processing described above.

The abnormality determination unit 51 determines whether or not the dehydration-sintering apparatus 100 is in an abnormal state based on the change over time in the concentration of the predetermined gas measured by the gas measurement unit 48 . As will be described later, the present inventor has determined the concentration of a predetermined gas measured by the gas measurement unit 48 and the average value of the concentration of the predetermined gas measured by the gas measurement unit 48 before the timing at which the concentration of the gas is measured. is equal to or greater than a first predetermined value, it is an abnormal state in which water is entering the space 35S. This is thought to be due to the fact that when water enters the space 35S, the water reacts with carbon to generate a predetermined gas, and the concentration of the predetermined gas increases. For this reason, the abnormality determination unit 51 of the present embodiment can determine the concentration of the predetermined gas measured by the gas measurement unit 48 and the concentration of the predetermined gas measured by the gas measurement unit 48 before the timing at which the concentration of the gas is measured. is equal to or greater than the first predetermined value, a signal indicating an abnormal state is output to the notification unit 56 via the control unit 60 . On the other hand, when the difference is less than the first predetermined value, the abnormality determination unit 51 does not output a signal to the control unit 60, but transmits a signal to the notification unit 56 via the control unit 60 indicating that there is no abnormality. may be output. Therefore, the judgment of the abnormality judgment section 51 is to change the output signal according to the signal from the gas measurement section 48 . The above first predetermined value can be set in advance by experiment or the like. For example, the first predetermined value is 500 ppm when the predetermined gas is carbon monoxide, and the first predetermined value is 450 ppm when it is carbon dioxide. be done. Moreover, the abnormality determination unit 51 may directly output a signal to the notification unit 56 .

The fiber defect determination unit 52 determines the amount of gas from the porous glass body, which is a part of the optical fiber, based on the change over time in the concentration of the predetermined gas measured by the gas measurement unit 48 while the porous glass body that is a part of the optical fiber is being heated. It is determined whether or not the optical fiber manufactured from the optical fiber preform including the member comprising the component will be defective. As will be described later, the present inventors found that when the difference between the concentration of the predetermined gas when the porous glass body is heated and the concentration of the predetermined gas in the initial state exceeds a second predetermined value, the porous glass It has been found that optical fibers manufactured from optical fiber preforms containing solid glass members are defective. As the amount of water entering the space 35S increases, the amount of water penetrating the furnace core tube 31 and entering the housing space 31S also increases, degrading the characteristics of the manufactured optical fiber, such as transmission loss. It has been found that when the above difference exceeds the second predetermined value, the properties generally required for optical fibers for long-distance transmission are not satisfied. The above 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. Further, the second predetermined value can be set in advance by experiment or the like. at 550 ppm. The fiber defect determination unit 52 of the present embodiment outputs a signal indicating that the optical fiber 1 is defective when the difference between the concentration of carbon monoxide and the concentration of carbon monoxide in the initial state exceeds 550 ppm. 60. On the other hand, when the difference is less than 550 ppm, the fiber defect determination unit 52 does not output a signal to the control unit 60, but outputs a signal to the control unit 60 indicating that the optical fiber 1 is not defective. good. Therefore, the determination by the fiber failure determination section 52 is to change the signal to be output according to the signal from the gas measurement section 48 . Alternatively, the fiber defect determination unit 52 may directly output a signal to the notification unit 56 .

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

Next, the first dehydration process P2a and the first sintering process P2b of the first heating process P2 will be described.

<First dehydration step P2a>
This step is a step of dehydrating the core porous glass body 20 by heating the core porous glass body 20 using the dehydration sintering apparatus 100 . 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 according to the control signal from the control unit 60, fills the accommodation space 31S with the first gas, and discharges the gas in the accommodation space 31S to the exhaust pipe. 44 is vented. Further, the second gas supply unit 42 supplies the second gas to the space 35S according to the control signal from the control unit 60, fills the space 35S with the second gas, and discharges the gas in the space 35S to the exhaust pipe 46. exhaust from Therefore, it is possible to prevent 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 section 60 while the first gas supply section 41 and the second gas supply section 42 are supplying gas. In a state where the heater 37 is generating heat, the elevating section 40 moves the porous core glass body 20 in a predetermined manner so that the entire core porous glass body 20 crosses the heater 37 in response to a control signal from the control section 60 . move at a speed of Therefore, the core porous glass body 20 is heated to a predetermined temperature by the heater 37 . By this heating, the OH groups of the core porous glass body 20 and attached moisture are removed by the dehydrating gas contained in the first gas. The heating temperature may be any temperature that is lower than the sintering temperature of the core porous glass body 20 and that can remove moisture from the core porous glass body 20, and is, for example, 1100° C. or higher and 1400° C. or lower. is preferred. A heating temperature of 1100° C. or higher promotes diffusion of gas into the core porous glass body 20 , and a heating temperature of 1400° C. or lower prevents the core porous glass body 20 from softening. can be suppressed sufficiently.

While the core porous glass body 20 is being heated by the heater 37 in this manner, the gas measurement unit 48 measures the concentration of carbon monoxide at predetermined time intervals, for example, at intervals of one minute, and measures the concentration of carbon monoxide. A signal indicating the concentration of carbon oxide is output to the determination unit 50 . That is, in this step, the concentration of carbon monoxide is measured by the gas measuring unit 48 while the core porous glass body 20 is heated by the heater 37. By such a heating method, the core porous glass body 20 is measured. to heat.

The abnormality determination unit 51 determines the concentration of carbon monoxide as a predetermined gas measured by the gas measurement unit 48, and the concentration of carbon monoxide measured by the gas measurement unit 48 before the timing at which the concentration of carbon monoxide is measured. When the difference from the average density value is greater than or equal to the first predetermined value, a signal indicating an abnormal state is output to the notification unit 56 , and the notification unit 56 performs notification based on the signal from the abnormality determination unit 51 . Therefore, the operator can recognize the abnormal state from the notification from the notification unit 56 . Further, the fiber defect determination unit 52 determines that the difference between the concentration of carbon monoxide measured by the gas measurement unit 48 and the concentration of carbon monoxide previously measured by the gas measurement unit 48 in the initial state exceeds 550 ppm. In this case, a signal indicating that the optical fiber becomes defective is output to the control unit 60 , and the notification unit 56 makes a notification based on the signal from the fiber defect determination unit 52 . Therefore, the operator can determine that the manufactured optical fiber will be defective from the notification from the notification unit 56 .

<First sintering step P2b>
In this step, after the first dehydration step P2a, the core porous glass body 20 is heated using the dehydration-sintering apparatus 100 used in the first dehydration step P2a to sinter the core porous glass body 20. is. 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. Further, the heater 37 generates heat while the first gas supply section 41 and the second gas supply section 42 are supplying gas. In addition, while the heater 37 is generating heat, the elevating section 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 and vitrified, and is preferably 1300° C. or higher and 1650° C. or lower, for example.

As in the first dehydration step P2a, the gas measurement unit 48 measures the concentration of carbon monoxide at intervals of, for example, one minute, and outputs a signal indicating the measured concentration of carbon monoxide to the determination unit 50 . Therefore, in this step, similarly to the first dehydration step P2a, the concentration of carbon monoxide is measured by the gas measuring unit 48 while the core porous glass body 20 is heated by the heater 37. The core porous glass body 20 is heated by a heating method. Then, similarly to the first dehydration step P2a, the notification unit 56 makes a notification based on the signals from the abnormality determination unit 51 and the fiber defect determination unit 52. FIG. Through this step, the core porous glass body 20 is vitrified into a transparent core to form 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 clad porous glass body that will become the clad glass body 11P shown in FIG. In the present 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 for forming the cladding porous glass body is not particularly limited. .

<Second heating step P4>
This step is a step of heating the clad 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. 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. 100 may be used.

<Second dehydration step P4a>
This step is a step of heating the clad porous glass body using the dehydration sintering apparatus 100 to dehydrate the clad porous glass body. This step differs from the first dewatering step P2a mainly in that the core glass rod on which the cladding porous glass body is formed is housed in the housing space 31S of the core tube 31 . For this reason, although detailed description of this step is omitted, in this step, the heater 37 heats the cladding porous glass body to dehydrate the cladding porous glass body, and the gas measurement unit 48 detects carbon monoxide. Measure the concentration of In this process, the fiber failure judgment unit 52 does not judge whether the optical fiber is defective, and the notification unit 56 makes a notification based on the signal from the abnormality judgment unit 51 .

<Second sintering step P4b>
In this step, after the second dehydration step P4a, the cladding porous glass body is heated using the dehydration sintering apparatus 100 used in 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 on which the porous glass body for cladding is dehydrated in the second dehydration step P4a is accommodated in the accommodation space 31S of the core tube 31. . For this reason, although detailed description of this step is omitted, in this step, the heater 37 heats the cladding porous glass body to sinter the cladding porous glass body, while the gas measurement unit 48 measures monoxide gas. Measure the concentration of carbon. In this process, the fiber failure judgment unit 52 does not judge whether the optical fiber is defective, and the notification unit 56 makes a notification based on the signal from the abnormality judgment unit 51 .

In this step, the core glass rod becomes the core glass body 10P shown in FIG. 2 with almost no change. Also, the clad porous glass body is converted into transparent glass to become the clad glass body 11P. Thus, the optical fiber preform 1P shown in FIG. 2 is obtained.

By heating and drawing the optical fiber preform 1P obtained in this manner in a spinning furnace, the core glass body 10P becomes the core 10, and the clad glass body 11P becomes the clad 11. The core 10 and the clad 11 are formed. An optical fiber bare wire is obtained. Then, the coating layer 12 is formed by coating the bare optical fiber with a resin that forms the coating layer 12, and the optical fiber 1 shown in FIG. 1 is manufactured.

As described above, the dehydration sintering apparatus 100 as a heating apparatus for a glass member according to the present embodiment includes the furnace core tube 31, the furnace body 35, the heater 37, and the gas measuring section . The furnace core tube 31 has an accommodation space 31S capable of accommodating the entire core porous glass body 20 as a glass member. The furnace body 35 surrounds at least a portion of the furnace core tube 31 , and the heater 37 is arranged in a space 35</b>S surrounded by the furnace core tube 31 and the furnace body 35 . At least one of the members arranged in this space 35S contains carbon. The gas measurement unit 48 can measure the concentration in the space 35S of a predetermined gas generated due to the reaction between water and carbon.

In the heating method of the core porous glass body 20 and the clad porous glass body as the glass members of the present embodiment, the heater 37 arranged in the space 35S surrounded by the furnace core tube 31 and the furnace body 35 heats these bodies. Heat the glass member. At least one of the members arranged in this space 35S contains carbon. Then, while heating these glass members by the heater 37, the concentration in the space 35S of a predetermined gas generated due to the reaction between water and carbon is measured.

When the glass member is dehydrated, sintered, melted, etc., the heater is generally heated to 700° C. or higher. In such a high-temperature state, when water enters the space 35S surrounded by the core tube 31 and the furnace body 35, the water reacts with the carbon contained in the members arranged in this space to generate gas. . The dehydration sintering apparatus 100 and the method for heating the glass member of the present embodiment can measure the concentration of the gas generated in this way, so that an abnormal state in which water has entered the space 35S can be detected.

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

The dehydration-sintering apparatus 100 of the present embodiment further includes a second gas supply unit 42 that supplies inert gas to the space 35S from an air supply port S2 that is formed in the furnace body 35 and communicates with the space 35S. Therefore, combustion of the heater 37, the heat insulating material 38, and the like, which are members arranged in the space 35S, can be suppressed. In addition, since the gas measurement unit 48 can measure the concentration of the gas generated due to the reaction between water and carbon in the space 35S, the second gas supply unit allows water to enter the space 35S together with the inert gas. 42 or the pipe 45 connected to the second gas supply unit 42, etc., can be detected.

Further, in the dehydration sintering apparatus 100 and the method for heating the glass member of the present embodiment, the concentration of the predetermined gas is measured from the exhaust gas discharged from the exhaust port E2 formed in the furnace body 35 and communicating with the space 35S. Therefore, compared to the case where the concentration of the predetermined gas is measured at a certain point in the space 35S, it is possible to suppress the influence of the location where the predetermined gas is generated in the space 35S on the concentration of the predetermined gas. Therefore, an abnormal state in which water has entered the space 35S can be detected more accurately than in the above case.

Moreover, the dehydration-sintering apparatus 100 of the present embodiment further includes an abnormality determination section 51 that determines whether or not there is an abnormality based on the change over time in the concentration of the predetermined gas measured by the gas measurement section 48 . The abnormality determination unit 51 determines the difference between the concentration of the predetermined gas measured by the gas measurement unit 48 and the average value of the concentration of the predetermined gas measured by the gas measurement unit 48 before the timing at which the concentration of the predetermined gas is measured. is greater than or equal to a first predetermined value, it is determined that an abnormal condition exists. Even if the furnace body 35 has the same configuration, the concentration of the predetermined gas measured in the steady state tends to vary depending on the installation state of the furnace body 35 . Therefore, by adopting the configuration as described above, it is possible to appropriately determine whether or not an abnormal state exists, compared to the case where it is determined that an abnormal state has occurred when the gas concentration is equal to or higher than a predetermined value.

The dehydration and sintering apparatus 100 of the present embodiment further includes a fiber defect determination unit 52 and heats the core porous glass body 20 which is a porous glass body that forms a part of the optical fiber 1 . The fiber defect determining unit 52 determines whether the optical fiber 1 is defective based on the change over time in the concentration of the predetermined gas measured by the gas measuring unit 48 while the core porous glass body 20 is being heated. to judge whether

If water enters the housing space 31S while the core porous glass body 20 is being sintered, the transmission loss and the like, which are the characteristics of the optical fiber 1 finally manufactured, may deteriorate. The characteristics tend to deteriorate as the amount of water that enters the Such intrusion of water into the accommodation space 31S may not affect the appearance of the transparent glass member formed by sintering the porous glass body 20 for core. For this reason, it may be difficult to judge whether or not the characteristics of the finally manufactured optical fiber 1 are deteriorated and the optical fiber 1 becomes defective based on the appearance of the transparent glass member. However, as the amount of water entering the housing space 31S increases, the amount of gas generated due to the reaction between water and carbon increases, and the concentration of the gas increases. Therefore, with the above configuration, it is possible to determine whether or not the optical fiber 1 finally manufactured will be defective at the stage of manufacturing the transparent glass member, and the defect of the optical fiber 1 can be determined. rate can be reduced and the productivity of the optical fiber 1 can be improved.

In the present embodiment, the predetermined gas is carbon monoxide, and the fiber failure determination unit 52 measures the gas measurement unit 48 while heating the core porous glass body 20 that becomes the core 10 of the optical fiber 1. If the difference between the concentration of carbon monoxide in the initial state and the concentration of carbon monoxide in the initial state exceeds 550 ppm, the optical fiber 1 is determined to be defective. As described above, the inventor believes that the optical fiber 1 produced from the optical fiber preform 1P including the core glass body 10P composed of the core porous glass body 20 is defective when the difference exceeds 550 ppm. I found out that it will be. Therefore, by adopting such a configuration, it is possible to appropriately determine whether or not the finally manufactured optical fiber 1 will be defective.

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

For example, in the above embodiment, the dehydration sintering apparatus 100 including the abnormality determination unit 51 and the fiber failure determination unit 52 has been described as an example. However, the dehydration sintering apparatus 100 does not have to include at least one of the abnormality determining section 51 and the fiber defect determining section 52 . In this case, for example, the operator can determine whether or not there is an abnormality or whether or not the optical fiber 1 is defective, based on the change over time in the concentration of the predetermined gas measured by the gas measuring unit 48. You may

In the above embodiment, the difference between the concentration of the predetermined gas measured by the gas measurement unit 48 and the average value of the concentration of the predetermined gas measured by the gas measurement unit 48 before the timing at which the concentration of the predetermined gas is measured is The abnormality determination unit 51 has been described as an example that determines that an abnormality is present when the value is equal to or greater than the first predetermined value. However, the abnormality determination unit 51 may determine whether or not there is an abnormality based on the change over time in the concentration of the predetermined 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 a predetermined gas is equal to or higher 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. However, from the viewpoint of appropriately judging whether or not there is an abnormal state, it is preferable that the abnormality judging section 51 judges whether or not there is an abnormal state as in the present embodiment. In addition, the abnormality determination unit 51 determines the difference between the concentration of the predetermined gas and the median value of the concentration of the predetermined gas before the timing when the concentration of the predetermined gas is measured, the concentration of the predetermined gas and the timing when the concentration of the predetermined gas is measured. Based on the difference between the previous average value of the concentration of the specified gas and the value obtained by subtracting the standard deviation, the difference between the concentration of the specified gas and the minimum value of the concentration of the specified gas before the timing when the concentration of the specified gas is measured, etc. Therefore, it may be determined that the state is abnormal. In this case, the abnormality determining unit 51 determines that an abnormal state exists when the difference between them is equal to or greater than a predetermined value, and this predetermined value is set based on experiments and the like for each difference. A state in which the optical fiber 1 becomes defective is an abnormal state. For this reason, for example, similar to the fiber defect determination unit 52 of the above-described embodiment, the abnormality determination unit 51 uses the concentration of carbon monoxide measured by the gas measurement unit 48 when the glass member is heated and the initial state If the difference from the concentration of carbon monoxide at 1 exceeds 550 ppm, it may be determined that an abnormal condition exists.

In the above embodiment, when the difference between the carbon monoxide concentration measured by the gas measuring unit 48 while the core porous glass body 20 is being heated and the carbon monoxide concentration in the initial state exceeds 400 ppm. In the above, the fiber defect determination unit 52 that determines that the optical fiber 1 is defective has been described as an example. However, the fiber defect determination unit 52 may determine whether or not there is an abnormality based on the change over time in the concentration of the predetermined gas measured by the gas measurement unit 48 . For example, the fiber defect determination unit 52 may output a signal indicating that the optical fiber 1 is defective when the concentration of a predetermined gas is equal to or higher 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. Further, in the above embodiment, the fiber defect determining section 52 determines whether or not the optical fiber 1 becomes defective based on the temporal change in the concentration of the predetermined gas measured in the first heating step P2. Here, if water enters the housing space 31S during sintering of the cladding porous glass body that will become the cladding 11 of the optical fiber 1, the transmission loss, which is the characteristic of the finally manufactured optical fiber 1, will increase. The transmission loss tends to worsen as the amount of water entering the accommodation space 31S increases. Therefore, the fiber defect determining section 52 may determine whether or not the optical fiber 1 becomes defective based on the change over time in the concentration of the predetermined gas measured in the second heating step P4. In this case, the threshold value of the concentration of the predetermined gas or the like for determining whether or not the optical fiber 1 becomes defective is set based on experimental values and the like.

Further, in the above-described embodiment, the furnace body 35 surrounding a part of the core tube 31 has been described as an example. However, the furnace body 35 only needs to surround at least a portion of the core tube 31 , and may surround the entire core tube 31 , for example.

Further, in the above embodiment, the dehydration sintering apparatus 100 including the second gas supply unit 42 has been described as an example. However, the dehydration sintering apparatus 100 does not have to include the second gas supply unit 42. For example, instead of the second gas supply unit 42, the air in the space 35S is exhausted from the exhaust pipe 46 to evacuate the space 35S. It may also be provided with an exhaust for condition. By evacuating the space 35S in this way, it is possible to suppress the combustion of the heater 37, the heat insulating material 38, and the like in the space 35S.

Further, in the above embodiment, the first deposition step P1 for forming the core porous glass body 20 that becomes the core glass body 10P has been described as an example. However, the porous glass body formed in the first deposition step P1 is not particularly limited, and may be, for example, a porous glass body that forms part of the core glass body 10P and the clad glass body 11P. In this case, in the second depositing 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 that will be another part of the clad glass body 11P.

Further, in the above embodiment, the method for manufacturing the optical fiber preform 1P including the first deposition process P1, the first heating process P2, the second deposition process P3, and the second heating process P4 has been described as an example. However, the method of manufacturing the optical fiber preform 1P may include a heating step of heating the porous glass body as the glass member by the method of heating the glass member described above. For example, the method of manufacturing the optical fiber preform 1P may not 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 fine particles are deposited on the outer peripheral surface of the core glass rod to form a porous glass body for clad.

Further, in the above-described embodiment, the first gas is the mixed gas of the dehydration gas and the inert gas, and the porous glass body is discharged while the first gas is supplied from the first gas supply unit 41 to the accommodation space 31S. The first sintering step P2b and the second sintering step P4b of heating are described as examples. However, in the first sintering process P2b and the second sintering process P4b, the porous glass body may be heated while only the inert gas is supplied to the housing space 31S. In this case, for example, the configuration of the first gas supply unit 41 is configured such that the first gas to be supplied can be changed between a gas containing the dehydration gas and the inert gas and only the inert gas. Then, 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 according to the process.

Further, in the above-described embodiment, in the first dehydration step P2a and the first sintering step P2b, the core porous glass body 20 is heated by the same dehydration and sintering apparatus 100, and the second dehydration step P4a and the second sintering step are performed. In P4b, the same dehydration and sintering apparatus 100 was used to heat the clad porous glass body. However, for example, in each step, the porous glass body may be heated by different dehydration and sintering apparatuses 100 . Further, the method for manufacturing the optical fiber preform 1P may further include a drawing step of obtaining a core glass rod by drawing the glass body obtained by sintering the core porous glass body 20 in the first heating step P2. good. The furnace core tube 31 only needs to have an accommodation space 31S that accommodates at least a portion of the glass member, and the furnace core tube 31 may have openings at both ends. For example, the device for drawing the glass body, the spinning furnace for heating the optical fiber preform 1P, and the front end processing furnace are also included in the heating device for the glass member of the present invention.

EXAMPLES 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 sintering apparatus 100 shown in FIG. 4, 32 core glass rods were manufactured by repeating the first deposition step P1 and the first heating step P2 shown in FIG. 3 32 times. In this dehydration sintering apparatus 100, the heater 37 was not heated after the furnace body 35 was installed until the first core glass rod was manufactured. In addition, the concentration of carbon monoxide and carbon dioxide in the space 35S in the initial state before the first heating step P2 for manufacturing the first core glass rod after the furnace body 35 is installed is measured by the gas measuring unit. 48. The initial carbon monoxide concentration was 150 ppm and the carbon dioxide concentration was 260 ppm. Further, the concentrations of carbon monoxide and carbon dioxide in the space 35S were measured by the gas measurement unit 48 during the first heating step P2 when manufacturing each core glass rod. This measurement result is shown in FIG. Note that FIG. 5 also shows a transmission loss, which will be described later.

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

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

As shown in FIG. 5, the transmission loss of the optical fiber 1 manufactured from the 1st to 27th core glass rods is approximately 0.28 dB/km, and the optical fiber 1 manufactured from the 28th core glass rod was 0.309 dB/km. The transmission loss of the optical fibers 1 manufactured from the 29th and subsequent core glass rods exceeded 0.31 dB/km, and the transmission loss tended to increase as the number of the 29th and subsequent core glass rods increased. In addition, when the 1st to 28th core glass rods were produced, the maximum carbon monoxide concentration was found in the 28th core glass rod, and the carbon monoxide concentration in the 28th core glass rod was 397 ppm. Among the 1st to 28th core glass rods, the 28th core glass rod had the highest carbon dioxide concentration, and the 28th core glass rod had a carbon dioxide concentration of 448 ppm. The concentration of carbon monoxide in the 29th line was 703 ppm, the concentration of carbon dioxide in the 29th line was 813 ppm, and the concentrations of carbon monoxide and carbon dioxide in the 29th line and beyond increased as the number increased. Therefore, it is conceivable that water began to enter the space 35S when the 28th wire was manufactured, and that the amount of water entering the space 35S increased as the number of wires increased after the 28th wire. Further, as described above, the concentration of carbon monoxide in the initial state was 150 ppm, and the concentration of carbon dioxide was 260 ppm. For this reason, the concentration of carbon monoxide when heating the core porous glass body 20 as the glass member and the initial state before heating the core porous glass body 20 for the first time after the furnace body 35 is installed It has been found that the optical fiber 1 fails when the difference from the concentration of carbon monoxide at 1 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 concentration of carbon monoxide is 700 ppm or more and when the concentration of carbon dioxide is 800 ppm or more. Note that when water and carbon react, methane, oxygen, and hydrogen are generated along with carbon monoxide and carbon dioxide. The amounts of methane, oxygen, and hydrogen produced tend to be stoichiometrically proportional to the amounts of carbon monoxide and carbon dioxide produced. For this reason, it is possible to set reference values for determining whether the optical fiber 1 is defective based on experimental values and the like for each concentration of methane, oxygen, and hydrogen.

Moreover, in the first to twenty-eighth lines, the difference between the carbon monoxide concentration and the average value of the carbon monoxide concentration measured before the timing at which the oxygen monoxide was measured was 500 ppm or less. In the 29th line, the difference was 506 ppm. Therefore, it was found that the dehydration sintering apparatus 100 is in an abnormal state when the difference is 500 or more. In addition, in the first to 28th runs, the difference between the carbon dioxide concentration and the average value of the carbon dioxide concentration measured before the timing at which the carbon dioxide was measured was 550 ppm or less. Moreover, in the 29th line, the difference was 553 ppm. Therefore, it was found that the dehydration sintering apparatus 100 is in an abnormal state when the difference is 550 or more. Further, it was found that the dehydration sintering apparatus 100 is in an abnormal state when the concentration of carbon monoxide is 700 ppm or more and when the concentration of carbon dioxide is 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. A reference value for determining whether or not the dehydration-sintering apparatus 100 is in an abnormal state can be set based on, for example.

As described above, a glass member heating apparatus 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 are provided. It is expected to be used in the field.

Reference Signs List 1 Optical fiber 1P Optical fiber preform 20 Porous glass body for core (porous glass body)
31...Furnace core tube 31S...Accommodating space 35...Furnace body 35S...Space 36...Flow path 37...Heater 41...First gas supply part 42...Second gas Supply unit 48 Gas measurement unit 51 Abnormality determination unit 52 Fiber defect determination unit 60 Control unit 100 Dehydration 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 core 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 core tube;
a heater arranged in a space surrounded by the furnace core tube and the furnace body;
a gas measurement unit;
with
At least one of the members arranged in the space contains carbon,
The heating apparatus for a glass member, wherein the gas measuring unit is capable of measuring the concentration in the space of the gas generated due to the reaction between water and carbon. 2. The apparatus for heating a glass member according to claim 1, wherein the gas is at least one of carbon monoxide, carbon dioxide, methane, and hydrogen. 3. The apparatus for heating a glass member according to claim 1, wherein the furnace body has a flow path through which cooling water flows. 4. The glass member according to any one of claims 1 to 3, further comprising a gas supply unit that supplies an inert gas to the space from an air supply port that is formed in the furnace body and communicates with the space. heating device. 5. The gas measurement unit according to any one of claims 1 to 4, wherein the gas measurement unit measures the concentration of the gas from exhaust gas discharged from an exhaust port formed in the furnace body and communicating with the space. The heating device for the glass member of. Further comprising an abnormality determination unit that determines whether an abnormal state exists based on changes in the concentration of the gas measured by the gas measurement unit over time,
The abnormality determination unit detects a difference between the concentration of the gas measured by the gas measurement unit and an average value of the concentrations of the gas measured by the gas measurement unit before the timing at which the concentration of the gas is measured. 6. The apparatus for heating a glass member according to any one of claims 1 to 5, wherein an abnormal state is determined when the temperature is equal to or greater than a predetermined value. further comprising a fiber defect determination unit,
The glass member is a porous glass body that forms part of an optical fiber,
7. The method according to any one of claims 1 to 6, wherein the fiber defect determination unit determines whether the optical fiber becomes defective based on a change in concentration of the gas measured by the gas measurement unit over time. The heating device for a glass member according to any one of the items. the gas is carbon monoxide;
The glass member is a porous glass body that serves as the core of the optical fiber,
The fiber defect determination unit determines that the difference between the concentration of the gas measured by the gas measurement unit and the concentration of the gas in an initial state before the glass member is heated for the first time after the furnace body is installed is determined. 8. The apparatus for heating a glass member according to claim 7, wherein the optical fiber is determined to be defective when the concentration exceeds 550 ppm. At least a part of a glass member is accommodated in an accommodation space in a furnace core tube at least partially surrounded by a furnace body, and the glass member is heated by a heater arranged in a space surrounded by the furnace core tube and the furnace body. A method for heating a member,
At least one of the members arranged in the space contains carbon,
A method of heating a glass member, wherein the concentration of a gas generated by a reaction between water and carbon in the space is measured while the glass member is heated by the heater. A method for manufacturing an optical fiber preform, comprising a heating step of heating a porous glass body as the glass member by the method for heating a glass member according to claim 9 .

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