Optical fiber preform manufacturing apparatus and method

Abstract

To provide a device and a method for producing an optical fiber preform that can prevent breakage of an optical fiber preform during execution of a glass soot forming process.SOLUTION: A device for producing an optical fiber preform has: a rotation holding mechanism that rotatably holds a starting material for the optical fiber preform; a burner that sprays flame containing glass soot to an outer peripheral surface of the starting material under rotation; a measurement mechanism that measures a load acting on the starting material in a vertical direction relative to its rotation axis; and a controller that stops the rotation of the starting material when an amplitude of the load measured in a predetermined period exceeds a predetermined level.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for manufacturing an optical fiber preform. [Background technology]

[0002] Patent Document 1 discloses an optical fiber preform manufacturing apparatus that predicts the core eccentricity of an optical fiber after drawing by measuring the load on a porous glass preform over time in a glass soot formation process. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-160196 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device illustrated in Patent Document 1, it was not assumed that the operation of the device would be controlled based on the change in load measured during the glass soot formation process. Therefore, even if some defect occurs in the optical fiber preform during the glass soot formation process, the glass soot formation process is continued, and there is a risk that the optical fiber preform will be damaged.

[0005] In view of the above-mentioned problems with the conventional technology, an object of the present invention is to provide an apparatus and method for manufacturing an optical fiber preform that can prevent damage to the optical fiber preform during the glass soot formation process. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a method for manufacturing an optical fiber preform, comprising: a rotational holding mechanism for rotatably holding a starting substrate of an optical fiber preform; a burner for blowing a flame containing glass soot onto an outer peripheral surface of the starting substrate during rotation; a measurement mechanism for measuring a load acting in a direction perpendicular to a rotation axis of the starting substrate; and a control device for stopping the rotation of the starting substrate when an amplitude of the load measured in a predetermined period of time exceeds a predetermined criterion. When the amplitude of the load exceeds the reference value, the control device detects the occurrence of a crack in the glass soot deposited on the outer peripheral surface. The present invention provides an apparatus for manufacturing an optical fiber preform.

[0007] According to another aspect of the present invention, a method for manufacturing an optical fiber preform includes the steps of: rotatably holding a starting substrate for an optical fiber preform; blowing a flame containing glass soot onto an outer peripheral surface of the starting substrate while the starting substrate is rotating; measuring a load acting in a direction perpendicular to a rotation axis of the starting substrate; and stopping the rotation of the starting substrate when an amplitude of the load measured in a predetermined period of time exceeds a predetermined criterion. detecting the occurrence of cracks in the glass soot deposited on the outer peripheral surface when the amplitude of the load exceeds the reference value; The present invention provides a method for manufacturing an optical fiber preform, comprising the steps of: Effect of the Invention

[0008] According to the present invention, there is provided an apparatus and method for manufacturing an optical fiber preform, which can prevent damage to the optical fiber preform during the glass soot formation process. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an overall configuration of a manufacturing apparatus according to an embodiment; [Diagram 2] FIG. 2 is a block diagram showing a schematic configuration of a control system of a manufacturing apparatus according to an embodiment. [Diagram 3] 4 is a flowchart showing an example of a process for forming glass soot in a manufacturing apparatus according to an embodiment. [Figure 4] FIG. 13 is a diagram illustrating changes in measured values ​​of vertical downward load over time. [Diagram 5] FIG. 13 is a diagram illustrating changes in measured values ​​of vertical downward load over time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings described below, parts having the same functions are designated by the same reference numerals, and repeated description thereof will be omitted.

[0011] 1 is a schematic diagram showing the overall configuration of a manufacturing apparatus 100 according to this embodiment. In this embodiment, the manufacturing apparatus 100 manufactures an optical fiber preform 10 by depositing glass soot on the outer peripheral surface of a starting substrate by an OVD method (outside vapor deposition method). In addition, the term "optical fiber preform" in this specification is a general term for a porous glass preform for optical fiber (porous optical fiber preform) and a preform obtained by sintering and vitrifying a porous glass member.

[0012] As shown in FIG. 1, the manufacturing apparatus 100 includes a reaction vessel 101, a spindle mechanism 102, a chuck 103, a target rod 104, a dummy rod 105, a load cell 106, a burner 107, a guide rail 108, and a traverse motor 109.

[0013] The manufacturing apparatus 100 further includes a raw material gas supplying device 110, a raw material gas supplying line 111, a carrier gas supplying device 112, a carrier gas supplying line 113, a combustion gas supplying device 114, a combustion gas supplying line 115, and an exhaust mechanism .

[0014] The spindle mechanism 102 is connected to both ends of a target rod 104 serving as a starting substrate via a pair of chucks 103, and holds the target rod 104 in a rotatable manner.

[0015] In addition, the spindle mechanism 102 drives the target rod 104 horizontally according to instructions from a control unit 200 described later, thereby loading and unloading the optical fiber preform 10 into and from the reaction vessel 101.

[0016] Further, the spindle mechanism 102 rotates the target rod 104 in a rotation direction R around the longitudinal direction L of the target rod 104 as the rotation axis in accordance with an instruction from the control unit 200 .

[0017] The dummy rod 105 is a rod-shaped member that is fused and fixed to both ends of the target rod 104. The spindle mechanism 102 rotates the dummy rod 105 and the target rod 104 that are held by a pair of chucks 103.

[0018] The load cell 106 is installed under the base of the spindle mechanism 102 and is a measuring device that measures the load in a vertical downward direction relative to the rotation axis of the optical fiber preform 10. When glass soot is deposited on the outer circumferential surface of the target rod 104 and the size of the optical fiber preform 10 increases, the load measured by the load cell 106 increases and the amplitude of the load also increases.

[0019] The load measured by the load cell 106 will be described in detail below. When glass soot that will become the cladding is synthesized and deposited on the target rod 104 by the OVD method, the vertically downward load acting on the rotation axis of the optical fiber preform 10 (i.e., the rotation axis of the target rod 104) is composed of a static load and a vertically downward component of the rotation load (hereinafter referred to as the "vertical downward load"). Here, the "static load" is the load of the preform itself, which is a load in a stationary state without rotation. On the other hand, the "rotation load" is generated when the mass distribution of the preform is non-uniform and its center of gravity is deviated from the rotation axis, and corresponds to the centrifugal force acting on the rotation axis.

[0020] When the center of gravity rotates around the axis of rotation, if the center of gravity is vertically below the axis of rotation, the rotational load acts vertically downward. On the other hand, if the center of gravity is vertically above the axis of rotation, the rotational load acts vertically upward. Therefore, when the center of gravity rotates around the axis of rotation, the vertical downward load vibrates according to the rotation period.

[0021] Since the optical fiber preform 10 grows over time, the static load increases. When the center of gravity is vertically downward relative to the rotation axis, the vertical downward load reaches the peak value of the vibration. Conversely, when the center of gravity is vertically upward relative to the rotation axis, the vertical downward load reaches the bottom value of the vibration.

[0022] In addition, in the manufacturing process of the optical fiber preform 10, even if a crack occurs in the preform, the soot may not peel off and the crack may reach near the glass body at the center. Also, the crack may run in the longitudinal direction L of the optical fiber preform 10. In such a case, the rigidity of the soot is lost at the azimuth position of the crack, causing the rotation balance to be disturbed.

[0023] Furthermore, if the target rod 104 continues to rotate while being out of balance, a load exceeding its own weight is periodically applied to the dummy rod 105, which is fused and fixed to the end of the target rod 104, and this may cause the dummy rod 105 to break in a short time. If the dummy rod 105 breaks, the optical fiber preform 10 will fall and be damaged. This not only results in a large production loss, but also causes great damage to the entire facility.

[0024] Therefore, the manufacturing apparatus 100 according to the present embodiment focuses on the fact that the amplitude of the load measured by the load cell 106 varies greatly depending on the presence or absence of the occurrence of a crack, and controls the execution of the glass soot forming process based on the amplitude of the load. The details of the control method will be described later.

[0025] The burner 107 forms a flame using the combustion gas supplied from the combustion gas supply device 114 in accordance with an instruction from the control unit 200 .

[0026] Moreover, the burner 107 hydrolyzes the raw material gas supplied from the raw material gas supply device 110 in the flame described above to form glass soot (glass particles), and blows the flame (gas G1) containing the glass soot onto the target rod 104. As a result, the burner 107 deposits the glass soot on the target rod 104 to form the optical fiber preform 10.

[0027] The optical fiber preform 10 manufactured by the manufacturing apparatus 100 is composed of a target rod 104 and a deposition soot 104a. In the OVD process, the target rod 104 as a starting substrate is a portion that will become the core and part of the cladding of the optical fiber. The deposition soot 104a is formed on the outer periphery of the target rod 104. The deposition soot 104a will become the cladding of the optical fiber.

[0028] The traverse motor 109 is driven to rotate, thereby reciprocating the burner 107 along the guide rail 108. The guide rail 108 is a member installed parallel to the longitudinal direction L of the optical fiber preform 10. The traverse motor 109 and the guide rail 108 constitute a movement mechanism for the burner 107.

[0029] The raw material gas supplying device 110 supplies raw material gas for synthesizing an optical fiber preform to the burner 107 via a mass flow controller (not shown) and a raw material gas supplying line 111 in accordance with instructions from the control unit 200. The raw material gas supplying device 110 includes a vaporizer (not shown). The vaporizer heats a liquid raw material of an organosilicon compound supplied from a storage tank (not shown) to a vaporization temperature or higher, thereby vaporizing the liquid raw material and supplying the raw material gas to the burner 107.

[0030] As the source gas, for example, octamethylcyclotetrasiloxane, hexamethyldisiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethoxymethylsilane, tetramethoxysilane, or the like can be used.

[0031] The carrier gas supply device 112 supplies a carrier gas to the burner 107 via a mass flow controller (not shown) and a carrier gas supply line 113 in accordance with an instruction from the control unit 200. The carrier gas is mixed with the raw material gas in the burner 107.

[0032] As the carrier gas, an inert gas such as nitrogen, argon, or helium, a mixed gas of oxygen and an inert gas, or oxygen can be used.

[0033] The combustion gas supply device 114 supplies combustion gas to the burner 107 via a mass flow controller (not shown) and a combustion gas supply line 115 in accordance with an instruction from the control unit 200. The combustion gas contains, for example, hydrogen and oxygen.

[0034] The exhaust mechanism 116 is installed facing the guide rail 108 so as to face the guide rail 108 via the target rod 104. The exhaust mechanism 116 has an exhaust hood 116a to collect exhaust gas after the flame combustion by the burner 107 to an exhaust port. The exhaust hood 116a is provided over the entire movable range of the burner 107 along the horizontal direction. The exhaust mechanism 116 also has a pump and a valve (not shown), and by driving the pump according to an instruction from the control unit 200, a flow of gas (exhaust gas G2) from the intake side of the reaction vessel 101 to the exhaust side is formed, and the inside of the reaction vessel 101 is exhausted. That is, the excess glass soot that could not be deposited on the target rod 104 is collected by the pump through the exhaust hood 116a and exhausted by the exhaust mechanism 116. This makes it possible to stabilize the flame of the burner 107.

[0035] 2 is a block diagram showing a schematic configuration of a control system according to this embodiment. The control unit 200 is a control device having a CPU (Central Processing Unit) 201 that executes various processing operations such as calculations, controls, and discrimination, and a ROM (Read Only Memory) 202 that stores various control programs executed by the CPU 201. The control unit 200 further has a RAM (Random Access Memory) 203 that temporarily stores data during processing operations of the CPU 201, input data, and the like, and a non-volatile memory 204 such as an HDD (Hard Disk Drive) or SSD (Solid State Drive).

[0036] In addition, the control unit 200 is connected to an input operation unit 205 including a keyboard or various switches for inputting predetermined commands or data, and a display unit 206 (e.g., a liquid crystal display or an organic EL display) for displaying various information including the input / setting status of the manufacturing equipment 100.

[0037] The control unit 200 is also connected to the spindle mechanism 102, the load cell 106, the burner 107, the traverse motor 109, the raw material gas supply device 110, the carrier gas supply device 112, the combustion gas supply device 114, and the exhaust mechanism 116 via drive circuits 207a to 207h. In this manner, each device of the manufacturing apparatus 100 is controlled by the control unit 200.

[0038] Hereinafter, the operation of the manufacturing apparatus 100 configured as described above will be described with reference to the drawings.

[0039] 3 is a flow chart showing an example of a process for forming glass soot in the manufacturing apparatus 100 according to the present embodiment. Note that this process is only an example and can be arbitrarily changed.

[0040] First, the control unit 200 controls the spindle mechanism 102 to load the target rod 104 into the reaction vessel 101 (step S101), and disposes the target rod 104 at a predetermined position (step S102).

[0041] Next, the control unit 200 refers to the manufacturing conditions stored in the ROM 202 or the RAM 203 and starts the glass soot forming process (step S103). In the glass soot forming process, the control unit 200 controls the spindle mechanism 102 to rotate the target rod 104 in a rotation direction R with the longitudinal direction L of the target rod 104 as the rotation axis.

[0042] In addition, in the glass soot forming step, the control unit 200 controls the combustion gas supply device 114 to supply combustion gas to the burner 107 to form a flame in the burner 107, and hydrolyzes the glass raw material gas supplied from the raw material gas supply device 110 to the burner 107 in the flame to form glass soot (glass particles), and blows the flame containing the glass soot onto the target rod 104. In this way, the control unit 200 deposits glass soot on the outer circumferential surface of the target rod 104 (step S104).

[0043] Next, the control unit 200 causes the burner 107 to reciprocate along the longitudinal direction L of the target rod 104 (step S105).

[0044] Specifically, when the position of the burner 107 moving along the longitudinal direction L of the target rod 104 reaches the left end or the right end of the target rod 104, the control unit 200 controls the rotation of the traverse motor 109 to reverse the moving direction of the burner 107. By repeating the reciprocating motion, glass soot is deposited on the outer circumferential surface of the target rod 104 with a uniform thickness in the longitudinal direction L.

[0045] Next, the control unit 200 controls the load cell 106 to measure the vertical downward load during a predetermined reference period (step S106), and calculates the average value of the amplitude of the vertical downward load during the same period (step S107). Hereinafter, the value obtained in step S107 is referred to as the "first load amplitude." Note that the reference period in this embodiment is the time length for the target rod 104 to rotate five times.

[0046] Next, the control unit 200 measures the vertical downward load in a predetermined period immediately after the reference period (step S108) and calculates the amplitude (step S109). Hereinafter, the value obtained in step S109 is referred to as the "second load amplitude." Note that the predetermined period in this embodiment is the time length for the target rod 104 to rotate once.

[0047] Next, the control unit 200 calculates the ratio between the first load amplitude and the second load amplitude with the first load amplitude as a reference (step S110).

[0048] Next, the control unit 200 determines a reference value of the ratio based on the first load amplitude (step S111). The first load amplitude may become larger as the weight of the glass soot deposited on the target rod 104 increases. Therefore, the reference value used to determine the ratio may be changed over time. The reference value may be determined based on the second load amplitude. The reference value may be set to, for example, 1.1 or more based on experimental results. Furthermore, the reference value may be a fixed value such as 1.05.

[0049] Next, the control unit 200 determines whether or not the ratio calculated in step S110 is equal to or smaller than a reference value (step S112).

[0050] Here, when the control unit 200 determines that the ratio is equal to or less than the reference value (step S112: YES), the process proceeds to step S113.

[0051] On the other hand, if the control unit 200 determines that the ratio exceeds the reference value (step S112: NO), the process proceeds to step S114.

[0052] In step S113, the control unit 200 determines whether the elapsed time has reached the end time of the glass soot forming process.

[0053] Here, if the control unit 200 determines that the elapsed time is the end time (step S113: YES), the process proceeds to step S115.

[0054] On the other hand, if the control unit 200 determines that the elapsed time is not the end time (step S113: NO), the process returns to step S104.

[0055] In step S114, the control unit 200 notifies the display unit 206 of the occurrence of a crack in the optical fiber preform 10. After that, the process proceeds to step S115, and the glass soot formation process is automatically stopped.

[0056] In step S115, the control unit 200 ends the glass soot formation process. Specifically, the control unit 200 controls the raw material gas supply device 110, the carrier gas supply device 112, and the combustion gas supply device 114 to stop the gas supply. In addition, the control unit 200 controls the spindle mechanism 102 to stop the rotation of the target rod 104.

[0057] Then, the control unit 200 drives the target rod 104 via the spindle mechanism 102 to carry out the optical fiber preform 10 with the glass soot deposited on the surface of the target rod 104 from the reaction vessel 101 (step S116).

[0058] As described above, in the manufacturing apparatus 100 according to the present embodiment, when the amplitude of the vertical downward load of the target rod 104, which is the rotation axis, exceeds a predetermined standard, the rotation of the target rod 104 can be stopped. As a result, the optical fiber preform 10 can be prevented from falling during the deposition of the glass soot, thereby eliminating the loss of the optical fiber preform 10 and avoiding damage to the manufacturing equipment.

[0059] Moreover, according to the manufacturing apparatus 100 of the present embodiment, when the amplitude of the vertical downward load of the target rod 104 exceeds a predetermined standard, it is possible to detect the occurrence of a crack in the optical fiber preform 10. That is, since the occurrence of a crack can be detected during the execution of the glass soot formation process, a prompt response can be made.

[0060] Even if a crack occurs, the target rod 104 can be recycled by removing the glass soot deposited on the outer circumferential surface of the target rod 104, which can reduce the manufacturing cost.

[0061] Furthermore, according to the manufacturing apparatus 100 of this embodiment, the weight of the optical fiber preform 10 can be measured without having to be measured after the apparatus is stopped, as is the case with conventional apparatus, so that the occurrence of cracks can be detected quickly.

[0062] <Example> Next, an embodiment of the present invention will be described. In the embodiment, the time for the target rod 104 to rotate five times is set as a reference period, and the average value of the vertical downward load amplitude during the reference period can be monitored. In addition, the time for the target rod 104 to rotate one time immediately after the reference period is set as a predetermined period, and the vertical downward load amplitude during the predetermined period is measured. In addition, an emergency stop function is set to stop the rotation of the target rod 104 when the average value of the vertical downward load amplitude during the predetermined period becomes 1.1 times the vertical downward load amplitude during the reference period.

[0063] 4 and 5 are diagrams for explaining the change in the measured value of the vertical downward load over time. FIG. 4 shows the data obtained by monitoring the output of the vertical downward load when the optical fiber preform 10 falls due to the breakage of the dummy rod 105. In FIG. 4, it is found that the vertical downward load amplitude increases rapidly in the period from time t1 to time t2. Then, at time t3, the optical fiber preform 10 falls in the reaction vessel 101 due to the breakage of the dummy rod 105. It is considered that such a change in the amplitude is caused by the weight of the optical fiber preform 10 becoming uneven in the radial direction due to the crack.

[0064] On the other hand, FIG. 5 shows data in which a new target rod 104 is set in another manufacturing apparatus 100, manufacturing of an optical fiber preform 10 is started, and the rotation of the target rod 104 and the gas supply are urgently stopped based on a change in amplitude.

[0065] Specifically, the vertical downward load amplitude changes significantly from the period T2 from time t12 to time t13 compared to the vertical downward load amplitude in the period T1 from time t11 to t12. The vertical downward load amplitude in the period T2 exceeds 1.1 times the average value of the vertical downward load amplitude in the period T1.

[0066] For this reason, the manufacturing apparatus 100 stopped the deposition of the glass soot by urgently stopping the rotation of the target rod 104 and the gas supply. As expected, it was confirmed that a crack had occurred in the axial direction of the optical fiber preform 10 after the stop.

[0067] It should be noted that the above-described embodiments are merely illustrative examples of the implementation of the present invention, and the technical scope of the present invention should not be construed as being limited thereby. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0068] 10. Optical fiber base material 100...Manufacturing equipment 101... Reaction vessel 102 Spindle mechanism 103···Chuck 104 Target Rod 105···Dummy rod 106 Load cell 107 Burner 108···Guide rail 109 Traverse motor 110 Raw material gas supply device 111 Raw gas supply line 112 Carrier gas supply device 113 Carrier gas supply line 114 Combustion gas supply device 115 Combustion gas supply line 116...Exhaust mechanism 116a···Exhaust hood 200...Control section 201···CPU 202...ROM 203...RAM 204...Non-volatile memory 205 Input operation section 206...Display section 207a~207h Drive circuit

Claims

1. a rotation holding mechanism that rotatably holds a starting substrate of an optical fiber preform; a burner for blowing a flame containing glass soot onto an outer peripheral surface of the starting substrate during rotation; A measurement mechanism for measuring a load acting in a direction perpendicular to the rotation axis of the starting substrate; a controller that stops rotation of the starting substrate when the amplitude of the load measured over a predetermined period of time exceeds a predetermined criterion; Equipped with The control device detects occurrence of a crack in the glass soot deposited on the outer peripheral surface when the amplitude of the load exceeds the reference value.

2. An optical fiber preform manufacturing apparatus comprising:

2. The predetermined period is set to a time length for the starting substrate to rotate once.

2. The apparatus for manufacturing an optical fiber preform according to claim 1.

3. the control device stops the rotation of the starting substrate when a ratio between an amplitude of the load measured during a reference period and an amplitude of the load measured during the predetermined period immediately after the reference period exceeds a predetermined reference value.

3. The apparatus for manufacturing an optical fiber preform according to claim 1 or 2.

4. The reference value is updated to a lower value as the weight of the glass soot deposited on the starting substrate increases.

4. The apparatus for manufacturing an optical fiber preform according to claim 3.

5. The reference value is 1.1 or more.

5. The apparatus for manufacturing an optical fiber preform according to claim 3 or 4.

6. The reference value is 1.

05.

4. The apparatus for manufacturing an optical fiber preform according to claim 3.

7. A step of rotatably holding a starting substrate for an optical fiber preform; spraying a flame containing glass soot onto an outer peripheral surface of the starting substrate while rotating; Measuring a load acting in a direction perpendicular to the axis of rotation of the starting substrate; stopping rotation of the starting substrate when the amplitude of the load measured over a predetermined period of time exceeds a predetermined criterion; detecting the occurrence of cracks in the glass soot deposited on the outer peripheral surface when the amplitude of the load exceeds the reference value; 2. A method for manufacturing an optical fiber preform comprising the steps of:

8. The predetermined period is set to a time length for the starting substrate to rotate once.

8. The method for producing an optical fiber preform according to claim 7.

9. In the step of stopping, the rotation of the starting substrate is stopped when a ratio between an amplitude of the load measured during a reference period and an amplitude of the load measured during the specified period immediately after the reference period exceeds a specified reference value.

9. The method for producing an optical fiber preform according to claim 7 or 8.

10. The reference value is updated to a lower value as the weight of the glass soot deposited on the starting substrate increases.

10. The method for producing an optical fiber preform according to claim 9.

11. The reference value is 1.1 or more.

11. The method for producing an optical fiber preform according to claim 9 or 10.

12. The reference value is 1.

05.

10. The method for producing an optical fiber preform according to claim 9.

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