Method and device for manufacturing optical fiber

Abstract

The invention provides an optical fiber manufacturing method and an optical fiber manufacturing device, which can effectively prevent a large number of unqualified optical fibers from being manufactured. A method for manufacturing an optical fiber in which an optical fiber base material is drawn and cooled by a cooling device, the method comprising the steps of: acquiring a monitoring result of a line position of the optical fiber on a route from the optical fiber base material to a directly below roller in which the drawn optical fiber first contacts; and detecting discontinuity of the line position of the optical fiber based on the monitoring result.

Description

Technical Field

[0001] The present disclosure relates to a method and apparatus for manufacturing an optical fiber. Background Art

[0002] Conventionally, technologies related to manufacturing devices for manufacturing optical fibers by drawing optical fibers from optical fiber mother materials have been developed. For example, Patent Document 1 discloses a device for detecting the line position of the optical fiber upstream and downstream of a cooling device in order to avoid manufacturing defective optical fibers due to contact between the cooling device and the optical fiber.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 11-130458 Summary of the invention

[0006] Technical problem to be solved by the invention

[0007] However, in the drawing of optical fibers, the inclination of the entire tower supporting the mother material may change momentarily as the weight of the mother material changes, and in such a case, the line position of the optical fiber also changes constantly. Therefore, for example, in a manufacturing method in which the line position of the optical fiber is measured and the drawing is stopped according to the displacement of the line position from the initial position, this may not be effective as a method for preventing a large number of defective optical fibers from being manufactured.

[0008] An object of the present disclosure is to more effectively prevent the mass production of defective optical fibers.

[0009] Solutions for solving technical problems

[0010] The optical fiber manufacturing method disclosed in the present invention is a method for manufacturing an optical fiber by drawing an optical fiber mother material and cooling the optical fiber by a cooling device, and the optical fiber manufacturing method comprises the following steps:

[0011] Acquiring a monitoring result of the linear position of the optical fiber on a route from the optical fiber preform to a roller directly below which the drawn optical fiber first contacts; and

[0012] Based on the monitoring result, discontinuity of the line position of the optical fiber is detected.

[0013] The optical fiber manufacturing device disclosed in the present invention comprises:

[0014] Optical fiber mother material;

[0015] A cooling device for cooling the optical fiber drawn from the optical fiber mother material;

[0016] The directly lower roller that the optical fiber first contacts;

[0017] a monitor, disposed on a route from the optical fiber mother material to the roller directly below, to monitor the line position of the optical fiber; and

[0018] The detection device detects discontinuity of the line position of the optical fiber based on the monitoring result of the monitor.

[0019] Effects of the Invention

[0020] According to the present disclosure, it is possible to more effectively prevent a large number of defective optical fibers from being manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram showing the structure of the manufacturing apparatus according to the present embodiment.

[0022] Figure 2 It is shown Figure 1 A block diagram of the structure of the control device is shown.

[0023] Figure 3 Is used to illustrate the Figure 2 FIG. 4 is a diagram showing the position of the optical fiber on the measurement surface detected by the detection unit.

[0024] Figure 4 Is used to illustrate the Figure 2 A diagram showing discontinuities in the line positions of optical fibers detected by a detection unit.

[0025] Figure 5 This is a flowchart for explaining the flow of operations when the optical fiber manufacturing apparatus according to the embodiment of the present disclosure detects discontinuity in the line position of the optical fiber. DETAILED DESCRIPTION

[0026] [Description of Embodiments of the Present Disclosure]

[0027] First, the contents of the embodiments of the present disclosure are listed and described.

[0028] (1) The optical fiber manufacturing method disclosed in the present invention is a method for manufacturing an optical fiber by drawing an optical fiber mother material and cooling the optical fiber by a cooling device, comprising the following steps:

[0029] Acquiring a monitoring result of the linear position of the optical fiber on a route from the optical fiber preform to a roller directly below which the drawn optical fiber first contacts; and

[0030] Based on the monitoring result, discontinuity of the line position of the optical fiber is detected.

[0031] As described above, by detecting the discontinuity of the line position of the optical fiber, it is possible to infer the occurrence of events that may cause the position of the cooling device to shift or deform, such as the opening and closing of the cooling device or the occurrence of an earthquake. Therefore, appropriate measures such as stopping the production of the optical fiber can be taken, which can more effectively prevent the mass production of defective optical fibers.

[0032] (2) Alternatively, the method for manufacturing an optical fiber according to (1) above may further include the following steps:

[0033] When the discontinuity is detected during a target period including a time when the opening and closing operation of the cooling device is performed, the drawing of the optical fiber is stopped.

[0034] In this way, by more reliably detecting a discontinuity that is likely to be caused by the opening and closing operation of the cooling device and stopping the drawing of the optical fiber, it is possible to more effectively prevent a large number of defective optical fibers from being produced.

[0035] (3) Alternatively, the method for manufacturing an optical fiber according to (1) above may further include the following steps:

[0036] When the discontinuity is detected during a target period including a time when the opening and closing operation of the cooling device is performed, a screening tension of a screening roller provided downstream of the directly below roller is applied to the optical fiber.

[0037] In this way, by more reliably detecting discontinuities that are likely to be caused by the opening and closing operations of the cooling device and applying screening tension, appropriate measures can be taken, such as stopping drawing when the optical fiber is broken and continuing drawing when the optical fiber is not broken.

[0038] (4) In the method for manufacturing an optical fiber according to (3) above,

[0039] In the step of applying the screening tension, the optical fiber is drawn to a length of 5 km or more in a state where the screening tension is set to 300 gf or more.

[0040] According to such a method, it is possible to more reliably prevent a large number of defective optical fibers from being manufactured.

[0041] (5) Alternatively, the method for manufacturing an optical fiber according to any one of (1) to (4) above may further include the following steps:

[0042] When the discontinuity is detected during a target period including the time of occurrence of an earthquake with a seismic intensity of 1 or higher, drawing of the optical fiber is stopped.

[0043] In this way, by more reliably detecting a discontinuity that is likely to be caused by an earthquake and stopping the drawing of the optical fiber, it is possible to more effectively prevent a large number of defective optical fibers from being produced.

[0044] (6) Alternatively, the method for manufacturing an optical fiber according to any one of (1) to (4) above may further include the following steps:

[0045] When the discontinuity is detected during a target period including the time of occurrence of an earthquake of seismic intensity 1 or higher, a screening tension of a screening roller disposed downstream of the immediately below roller is applied to the optical fiber.

[0046] In this way, by more reliably detecting discontinuities that are likely to be caused by earthquakes and applying screening tension, appropriate measures can be taken, such as stopping drawing when the optical fiber is broken and continuing drawing when the optical fiber is not broken.

[0047] (7) In the method for manufacturing an optical fiber according to (6),

[0048] In the step of applying the screening tension, the optical fiber is drawn to a length of 5 km or more in a state where the screening tension is set to 300 gf or more.

[0049] According to such a method, it is possible to more reliably prevent a large number of defective optical fibers from being manufactured.

[0050] (8) In the method for manufacturing an optical fiber according to any one of (1) to (7),

[0051] In the step of detecting discontinuity of the monitoring result, when a change amount of a moving average value of the line position of the optical fiber within a target period of a predetermined length is 20 μm / second or more, it is determined that the line position has discontinuity.

[0052] This makes it possible to more accurately determine whether or not to take measures such as stopping the production of optical fibers.

[0053] (9) In the method for manufacturing an optical fiber according to (8) above,

[0054] In the step of detecting discontinuity of the monitoring result, when a change amount of a moving average value of the line position of the optical fiber within a target period of a predetermined length is 50 μm / second or more, it is determined that the line position has discontinuity.

[0055] This makes it possible to more accurately determine whether or not to take measures such as stopping the production of optical fibers.

[0056] (10) The optical fiber manufacturing device of the present disclosure comprises:

[0057] Optical fiber mother material;

[0058] A cooling device for cooling the optical fiber drawn from the optical fiber mother material;

[0059] The directly lower roller that the optical fiber first contacts;

[0060] a monitor, disposed on a route from the optical fiber mother material to the roller directly below, to monitor the line position of the optical fiber; and

[0061] The detection device detects discontinuity of the line position of the optical fiber based on the monitoring result of the monitor.

[0062] As described above, by detecting the discontinuity of the line position of the optical fiber, it is possible to infer the occurrence of events that may cause the position of the cooling device to shift or deform, such as the opening and closing of the cooling device or the occurrence of an earthquake. Therefore, appropriate measures such as stopping the production of the optical fiber can be taken, which can more effectively prevent the mass production of defective optical fibers.

[0063] [Details of the embodiments of the present disclosure]

[0064] Hereinafter, specific examples of the manufacturing method and manufacturing device of the optical fiber involved in the embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the present invention is not limited to these examples, but is shown by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims. In addition, in the drawings used in the following description, the scale is appropriately changed to make each component a recognizable size.

[0065] (Optical fiber manufacturing device)

[0066] Figure 1 1 is a schematic diagram showing the structure of a manufacturing device 1 according to the present embodiment. Figure 1 As shown, the manufacturing apparatus 1 is provided with a heating furnace 21 on the upstream side for heating a glass matrix material (optical fiber matrix material) 200 for optical fiber. The heating furnace 21 includes a cylindrical furnace core tube 3 into which the glass matrix material 200 is supplied, and a heating element 4 surrounding the furnace core tube 3, and a heating area for softening the glass matrix material 200 is formed by the heating element 4. In addition, the heating furnace 21 is provided with a gas supply unit 5 for supplying a purge gas to the heating area.

[0067] The glass mother material 200 is supported by a dummy rod D on the upper part of the glass mother material 200 held by the holding mechanism 6, and is sent into the heating furnace 21 in such a manner that the lower end portion thereof is located in the heating area inside the furnace core tube 3. The lower end portion of the glass mother material 200 is pulled downward to be thinned, and the optical fiber G1 before resin coating is drawn.

[0068] The holding mechanism 6 includes a feeder 22 that lowers the held glass base material 200 as the wire drawing proceeds. The feeder 22 includes a rotation mechanism that rotates the glass base material 200 about an axis and a horizontal movement mechanism that moves the glass base material 200 in the horizontal direction (XY direction).

[0069] A cooling device 7 is provided downstream of the heating furnace 21. The cooling device 7 has a structure that can bring a pair of cooling bodies closer to each other (closed state) or away from each other (open state). When the cooling device 7 is in the closed state, the optical fiber G1 is cooled.

[0070] A guide wire nozzle 9 for coating an ultraviolet curing resin on the optical fiber G1 and an ultraviolet irradiation device 10 for curing the coated ultraviolet curing resin are provided on the downstream side of the cooling device 7. The optical fiber G1 passing through the guide wire nozzle 9 and the ultraviolet irradiation device 10 has a coating layer of ultraviolet curing resin formed on its outer periphery, and becomes an optical fiber G2.

[0071] After passing through the ultraviolet irradiation device 10 , the optical fiber G2 is hung on a directly below roller 11 provided directly below the heating furnace 21 , and the traveling direction is changed by the directly below roller 11 .

[0072] A guide roller 12 is provided downstream of the roller 11 directly below, and the optical fiber G2 passing through the guide roller 12 is sent to the screening section 13. Then, the optical fiber G2 is guided by the guide roller 17 through the screening section 13, and is sent to the winding bobbin 20 for winding through the adjustment rollers 18 and 19. Hereinafter, the optical fiber G1 and the optical fiber G2 are each also referred to as "optical fiber G".

[0073] The screening section 13 includes a capstan 14, a guide roller 15, and a screening roller 16. In the screening section 13, the optical fiber G2 is pulled by the capstan 14, guided by the guide roller 15, and a screening tension is applied to the screening roller 16. The screening roller 16 is, for example, a friction roller, and can apply a screening tension of a value corresponding to the difference in rotation speed between the capstan 14 and the screening roller 16 to the optical fiber G2.

[0074] Furthermore, the manufacturing apparatus 1 includes a control device (detection device) 2. The feeder 22, the screening unit 13, and the like are connected to the control device 2 in a communicable manner, and the control device 2 appropriately controls them.

[0075] Specifically, the screening section 13 controls the rotation speeds of the capstan 14 and the screening roller 16 by the control device 2 , respectively, so as to generate screening tension according to the difference in rotation speed between the capstan 14 and the screening roller 16 .

[0076] (Detection of optical fiber line position)

[0077] The manufacturing apparatus 1 further includes one or more monitors 30, which are provided on the route from the glass base material 200 to the roller 11 directly below, and are used to monitor the line position of the optical fiber G. Figure 1 In the manufacturing apparatus 1 shown in the figure, as an example, a first monitor 30A, a second monitor 30B, and a third monitor 30C are provided as the monitors 30 .

[0078] The first monitor 30A is provided on the route between the glass base material 200 and the cooling device 7. The second monitor 30B is provided on the route between the cooling device 7 and the wire guide nozzle 9. The third monitor 30C is provided on the route between the ultraviolet irradiation device 10 and the roller 11 directly below.

[0079] Each monitor 30 is, for example, an optical measuring device, and measures the line position of the optical fiber G on a measuring plane intersecting the traveling direction of the optical fiber G. More specifically, each monitor 30 always measures the line position of the optical fiber G in a first direction (hereinafter referred to as the "X direction") on the measuring plane and the line position of the optical fiber G in a second direction (hereinafter referred to as the "Y direction") on the measuring plane. Then, each monitor 30 transmits the measurement result (monitoring result) to the control device 2 by wire or wirelessly.

[0080] The control device 2 controls the feeder 22 so that the line position of the optical fiber G becomes constant, for example, based on the measurement result transmitted from the first monitor 30A.

[0081] In addition, the control device 2 detects the discontinuity of the line position of the optical fiber G based on the measurement results sent from each monitor 30. Then, when the discontinuity of the line position of the optical fiber G is detected, the control device 2 stops the drawing of the optical fiber G by, for example, controlling the feeder 22 to pull up the glass base material 200.

[0082] (Structure of control device)

[0083] Figure 2 It is shown Figure 1 The block diagram of the structure of the control device 2 shown in FIG. Figure 2 The control device 2 includes an acquisition unit 31, a detection unit 32, a storage unit 33, and a control unit 34. The storage unit 33 is a ROM (Read Only Memory) or a RAM (Random Access Memory) or the like.

[0084] The acquisition unit 31 acquires data transmitted from an external device. For example, when the acquisition unit 31 receives measurement results transmitted from each monitor 30 , the acquisition unit 31 stores the received measurement results together with time information in the storage unit 33 .

[0085] The acquisition unit 31 can also receive an earthquake early warning sent from an external device. When receiving an earthquake early warning, the acquisition unit 31 stores, for example, the earthquake intensity and the time of occurrence of the earthquake indicated in the earthquake early warning in the storage unit 33 .

[0086] The control unit 34 periodically checks the measurement results from the first monitor 30A stored in the storage unit 33, and controls the feeder 22 as described above so that the line position of the optical fiber G is constant. In addition, the control unit 34 controls the opening and closing of the cooling device 7 by sending a control signal to the cooling device 7. The control timing of the cooling device 7 by the control unit 34 is stored in the storage unit 33.

[0087] The detection unit 32 determines whether or not there is discontinuity in the line position of the optical fiber G based on the measurement results stored in the storage unit 33 .

[0088] Here, in the Figure 1 When the cooling device 7 shown in FIG. 1 is displaced or deformed, the optical fiber G may be in contact with the cooling device 7, and the strength of the optical fiber G may be reduced. In addition, when the nozzle 9 is displaced or deformed, the coating of the ultraviolet curing resin on the optical fiber G may be uneven, and an unqualified optical fiber G with uneven thickness may be manufactured. Therefore, the control device 2 detects the discontinuity of the line position of the optical fiber G based on the measurement result from the monitor 30.

[0089] Figure 3 Is used to illustrate the Figure 1 FIG. 1 is a diagram showing the line position of the optical fiber G measured by the monitor 30 . Figure 4 Is used to illustrate the Figure 2 FIG. 1 is a diagram showing discontinuities in the line positions of the optical fiber G detected by the detection unit 32 .

[0090] Reference Figure 3 and Figure 4 Specifically, assuming that during the period from time t1 to time t2, Figure 1 The line position of the optical fiber G measured by one of the plurality of monitors 30 is Figure 3 In addition, it is assumed that at time t2, the linear position of the optical fiber G changes due to the control of the cooling device 7 or an earthquake. Then, it is assumed that at time t3 later than time t2, the linear position of the optical fiber G measured by the monitor 30 is Figure 3 The position of the reference numeral B (XY coordinates: 20, 40).

[0091] The detection unit 32 always monitors the line position of the optical fiber G by referring to the measurement results stored in the storage unit 33, for example. Specifically, the detection unit 32 regularly calculates the moving average value in the X direction and the moving average value in the Y direction.

[0092] Then, the detection unit 32 determines that the line position of the optical fiber G has discontinuity when at least one of the moving average value in the X direction and the moving average value in the Y direction is greater than the threshold value. The threshold value is, for example, 20 μm / second, or may be 50 μm / second. Thus, it is possible to more accurately determine whether to take measures such as stopping the production of the optical fiber. In addition, when the detection unit 32 detects the discontinuity of the line position of the optical fiber G, it outputs a detection signal to the control unit 34.

[0093] As described above, in the manufacturing device 1 according to the embodiment of the present disclosure, the discontinuity of the line position of the optical fiber G is detected. As a result, it is possible to infer the occurrence of an event that may cause the positional displacement or deformation of the cooling device 7 or the wire guide nozzle 9, so as to be described below, appropriate measures such as stopping the drawing of the optical fiber G can be taken, and a large number of defective optical fibers G can be more effectively prevented from being manufactured.

[0094] It should be noted that the detection unit 32 is not limited to a structure that always monitors the linear position of the optical fiber G. For example, when an event occurs that may cause the positional displacement or deformation of the cooling device 7 or the guide wire nozzle 9, the detection unit 32 may monitor the linear position of the optical fiber G during a period including the time when the event occurs. That is, the detection unit 32 may also be a structure that, in a state where the occurrence of an event is determined, monitors the linear position of the optical fiber G during a period limited to including the time when the event occurs.

[0095] Specifically, when the control timing of the cooling device 7 or the occurrence time of an earthquake is newly stored in the storage unit 33, the detection unit 32 sets a target period including the control timing or the occurrence time. The length of the target period is, for example, within a range of 1 second to 10 seconds. Then, the detection unit 32 determines whether the moving average value in the X direction and the moving average value in the Y direction of the optical fiber G during the target period are each greater than a threshold value, thereby determining whether there is discontinuity in the line position of the optical fiber G during the target period.

[0096] In such a configuration, since the discontinuity of the line position of the optical fiber G caused by the event can be detected more reliably, a more appropriate response can be taken according to the content of the event. In addition, by limiting the monitoring to the target period including the time of occurrence of the event, the processing load for monitoring by the detection unit 32 can be reduced.

[0097] In addition, the detection unit 32 can be based on the data from the plurality of monitors 30 (see Figure 1) to detect the discontinuity of the line position of the optical fiber G. Alternatively, when the detection unit 32 outputs a detection signal indicating that the discontinuity of the line position is detected to the control unit 34, the detection unit 32 may also notify the control unit 34 of the identification information of the monitor 30 that is the transmission source of the measurement results used in the detection.

[0098] (Details of control by the control unit)

[0099] When the control unit 34 receives a detection signal indicating that discontinuity of the line position of the optical fiber G is detected from the detection unit 32, for example, the control unit 34 sends a signal to the optical fiber G to stop drawing the optical fiber G. Figure 1 The feeder 22 shown sends a control signal. This can prevent a large number of defective optical fibers from being produced.

[0100] Alternatively, the control unit 34 may control the optical fiber G so that the screening tension is applied to the optical fiber G when the control unit 34 receives the detection signal from the detection unit 32. Figure 1 The rotation speeds of the capstan 14 and the selection roller 16 are set for a certain period of time. For example, the control unit 34 controls the optical fiber G to be drawn to a length of 5 km or more in a state where the selection tension is 300 gf or more.

[0101] In this way, when discontinuity of the line position of the optical fiber G is detected, by applying a screening tension, for example, when the optical fiber G is broken, the drawing can be stopped, thereby preventing a large number of defective optical fibers from being produced. In addition, appropriate measures can be taken, such as continuing the drawing when the optical fiber G is not broken.

[0102] (Action flow)

[0103] Figure 5 This is a flowchart for explaining the flow of actions when the optical fiber manufacturing apparatus 1 according to the embodiment of the present disclosure detects discontinuity in the line position of the optical fiber G. Here, a case where control is performed to close the cooling device 7 and the line position of the optical fiber G is monitored during a target period including the timing of the control is explained.

[0104] Reference Figure 1 , Figure 2 and Figure 5 First, when the control unit 34 in the control device 2 performs control to close the cooling device 7 , the control timing is stored in the storage unit 33 (step S11 ).

[0105] Next, when the above-mentioned control timing is newly stored in the storage unit 33 , the detection unit 32 sets a target period including the control timing (step S12 ).

[0106] Next, the detection unit 32 checks whether there is discontinuity in the line position of the optical fiber G during the target period based on the measurement results from each monitor 30 stored in the storage unit 33 (step S13 ).

[0107] Next, when the detection unit 32 detects discontinuity in the line position of the optical fiber G during the target period (YES in step S13 ), the control unit 34 controls the screening unit 13 to apply screening tension to the optical fiber G for a certain period of time (step S14 ).

[0108] Next, the detection unit 32 obtains a test result indicating whether the optical fiber G is broken from, for example, a test device (not shown) or the like, thereby confirming whether the optical fiber G is broken (step S15 ).

[0109] Then, when the optical fiber G is broken (“Yes” in step S15), the detection unit 32 controls the Figure 1 The feeder 22 shown is turned on, thereby stopping the drawing of the optical fiber G1 (step S16).

[0110] On the other hand, when the detection unit 32 does not detect discontinuity in the line position of the optical fiber G during the target period ("No" in step S13), or when the optical fiber G is not broken even when the control of the screening unit 13 is performed ("No" in step S15), the drawing of the optical fiber G continues.

[0111] It should be noted that, as described above, the detection unit 32 in the control device 2 may be configured to always monitor the line position of the optical fiber G regardless of whether an event occurs or not. Figure 5 The processing of step S11 and step S12 is shown.

[0112] The present invention has been described in detail with reference to specific embodiments, but various changes or modifications can be made without departing from the spirit and scope of the present invention, which is obvious to those skilled in the art. In addition, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the preferred number, position, shape, etc. when implementing the present invention.

[0113] Description of Reference Numerals

[0114] 1 Manufacturing device; 2 Control device; 3 Furnace core tube; 4 Heater; 5 Gas supply unit; 6 Holding mechanism; 7 Cooling device; 9 Wire guide nozzle; 10 Ultraviolet irradiation device; 11 Directly below roller; 12, 15, 17 Guide rollers; 13 Screening unit; 14 Capstan; 16 Screening roller; 18, 19 Adjusting rollers; 20 Bobbin; 21 Heating furnace; 22 Feeder; 30 Monitor; 30A First monitor; 30B Second monitor; 30C Third monitor; 31 Acquisition unit; 32 Detection unit; 33 Storage unit; 34 Control unit; 200 Glass base material (optical fiber base material); G, G1, G2 Optical fiber; t1, t2, t3 Time.

Claims

1. A method for manufacturing an optical fiber, which is a method for manufacturing an optical fiber by drawing an optical fiber mother material and cooling the optical fiber by a cooling device, comprising the following steps: Acquiring a monitoring result of the linear position of the optical fiber on a route from the optical fiber preform to a roller directly below which the drawn optical fiber first contacts; and Based on the monitoring result, discontinuity of the line position of the optical fiber is detected.

2. The method for manufacturing an optical fiber according to claim 1, The manufacturing method further comprises the following steps: When the discontinuity is detected during a target period including a time when the opening and closing operation of the cooling device is performed, the drawing of the optical fiber is stopped.

3. The method for manufacturing an optical fiber according to claim 1, The manufacturing method further comprises the following steps: When the discontinuity is detected during a target period including a time when the opening and closing operation of the cooling device is performed, a screening tension of a screening roller provided downstream of the directly below roller is applied to the optical fiber.

4. The method for manufacturing an optical fiber according to claim 3, In the step of applying the screening tension, the optical fiber is drawn to a length of 5 km or more in a state where the screening tension is set to 300 gf or more.

5. The method for manufacturing an optical fiber according to claim 1, The manufacturing method further comprises the following steps: When the discontinuity is detected during a target period including the time of occurrence of an earthquake with a seismic intensity of 1 or higher, drawing of the optical fiber is stopped.

6. The method for manufacturing an optical fiber according to claim 1, The manufacturing method further comprises the following steps: When the discontinuity is detected during a target period including the time of occurrence of an earthquake of seismic intensity 1 or higher, a screening tension of a screening roller disposed downstream of the immediately below roller is applied to the optical fiber.

7. The method for manufacturing an optical fiber according to claim 6, In the step of applying the screening tension, the optical fiber is drawn to a length of 5 km or more in a state where the screening tension is set to 300 gf or more.

8. The method for producing an optical fiber according to any one of claims 1 to 7, In the step of detecting discontinuity of the monitoring result, when a change amount of a moving average value of the line position of the optical fiber within a target period of a predetermined length is 20 μm / second or more, it is determined that the line position has discontinuity.

9. The method for manufacturing an optical fiber according to claim 8, In the step of detecting discontinuity of the monitoring result, when a change amount of a moving average value of the line position of the optical fiber within a target period of a predetermined length is 50 μm / second or more, it is determined that the line position has discontinuity.

10. An optical fiber manufacturing device, comprising: Optical fiber mother material; A cooling device for cooling the optical fiber drawn from the optical fiber mother material; The directly lower roller that the optical fiber first contacts; A monitor is provided on the route from the optical fiber mother material to the roller directly below to monitor the line position of the optical fiber; as well as The detection device detects discontinuity of the line position of the optical fiber based on the monitoring result of the monitor.

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