Optical fiber core wire manufacturing method

Abstract

To provide a manufacturing method of an optical fiber core wire capable of improving a yield in forming a coloring layer.SOLUTION: A manufacturing method of an optical fiber core wire includes: a coloring process of passing an optical fiber strand through a passage port of a coloring die where a coloring resin is supplied from a supply port to form a coloring layer over a circumference of the optical fiber strand to obtain an optical fiber core wire; and a stand-by process of arranging the coloring die on a pass line of the optical fiber strand in the coloring process under a linear velocity stop state of the optical fiber strand. In the stand-by process, a resin pressure of the coloring resin in the coloring die is a positive pressure, and the coloring process is started while the resin pressure of the coloring resin is the positive pressure.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a method of forming a colored layer on an optical fiber by applying a colored resin to the outer periphery of a fed optical fiber strand. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-197455 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses controlling the resin pressure of the coloring resin in the coloring die when applying the coloring resin to the outer circumference of an optical fiber. Specifically, when the linear velocity of the optical fiber passing through the coloring die is zero, the resin pressure is also zero. When the linear velocity of the optical fiber passing through the coloring die begins to increase, the resin pressure also increases. When the linear velocity of the optical fiber passing through the coloring die reaches a steady state, the resin pressure is also controlled to maintain a predetermined value.

[0005] However, in optical fiber cores obtained by applying a colored resin to an optical fiber strand, defective molding portions such as lumps may be formed in the colored layer.

[0006] The present disclosure provides a method for manufacturing an optical fiber that improves yield in forming a colored layer. [Means for solving the problem]

[0007] A method for manufacturing an optical fiber according to one aspect of the present disclosure includes: a coloring step of passing an optical fiber through a passage opening of a coloring die into which a colored resin is supplied from a supply opening, thereby forming a colored layer on the outer periphery of the optical fiber, thereby producing an optical fiber core; a standby step of disposing the coloring die on a pass line through which the optical fiber passes in the coloring step while the optical fiber is in a stopped state of drawing speed, In the waiting step, the resin pressure of the colored resin in the coloring die is positive pressure, The coloring process is started while the resin pressure of the colored resin is kept positive. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a method for manufacturing an optical fiber that improves the yield in forming a colored layer. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of an optical fiber coated wire manufacturing apparatus. [Figure 2] FIG. 2 is a diagram showing the relationship between the drawing speed and time in the method for manufacturing an optical fiber coated wire, and the relationship between the resin pressure and time in the method for manufacturing an optical fiber coated wire and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Description of Embodiments of the Present Disclosure) First, embodiments of the present disclosure will be listed and described. A method for manufacturing an optical fiber according to one aspect of the present disclosure includes: (1) a coloring step of passing an optical fiber through a passage opening of a coloring die into which a colored resin is supplied from a supply opening, thereby forming a colored layer on the outer periphery of the optical fiber, thereby producing an optical fiber core; a standby step of disposing the coloring die on a pass line through which the optical fiber passes in the coloring step while the optical fiber is in a stopped state of drawing speed, In the waiting step, the resin pressure of the colored resin in the coloring die is positive pressure, The coloring process is started while the resin pressure of the colored resin is kept positive. According to the above configuration, even during the standby process, the resin pressure of the colored resin in the coloring die is positive, so that the colored resin in the coloring die can be prevented from flowing back toward the supply port. If the colored resin in the coloring die flows back toward the supply port, air will be entrained during the backflow, causing air bubbles to form inside the colored resin. If colored resin with air bubbles floating inside is applied during the coloring process, this can cause defective moldings to form. However, in the manufacturing method for optical fiber core wire disclosed herein, backflow of the colored resin is unlikely to occur, so air bubbles are also unlikely to form, the occurrence of defective moldings can be suppressed, and yields can be improved.

[0011] (2) In the method for manufacturing an optical fiber core according to (1) above, the height of the liquid surface of the colored resin in a supply tank that supplies the colored resin to the coloring die may be higher than the height of the liquid surface of the colored resin in the coloring die. With this configuration, the liquid level of the pre-colored resin in the supply tank is higher than the liquid level of the colored resin in the coloring die, so the resin pressure of the colored resin in the coloring die naturally becomes positive, thereby realizing a manufacturing method of optical fiber that suppresses the occurrence of molding defects with a simple configuration.

[0012] (3) In the standby step of the method for manufacturing an optical fiber according to (1) or (2) above, the optical fiber may be stopped in a state where it passes through the passage opening. According to the above configuration, the optical fiber is stopped while being passed through the passage opening, so that even if the resin pressure of the colored resin in the coloring die is positive, the colored resin is unlikely to overflow from the passage opening.

[0013] (4) In the method for manufacturing an optical fiber according to any one of (1) to (3) above, the passage opening has an entrance opening through which the optical fiber enters the coloring die; In the waiting step, a cover portion that covers the wire inlet may be attached to the coloring die. According to the above configuration, a cover portion is provided at the inlet port to seal the gap between the optical fiber wire and the coloring die, so that the coloring resin is less likely to overflow from the inlet port even when resin pressure of the coloring resin is applied in the coloring die.

[0014] (5) In the method for manufacturing an optical fiber according to any one of (1) to (4) above, the passage opening has an entrance opening through which the optical fiber enters the coloring die, The colored resin overflowing from the inlet may be collected. According to the above configuration, even if the colored resin overflows from the coloring die, the overflowed colored resin can be collected and reused.

[0015] (6) In the method for manufacturing an optical fiber core according to (5) above, the temperature of the colored resin inside the colored die during the waiting process may be controlled to be lower than the temperature of the colored resin inside the colored die during the coloring process. According to the above configuration, by controlling the temperature of the colored resin inside the coloring die so that the viscosity of the colored resin in the waiting process is higher than the viscosity of the colored resin in the coloring process, the colored resin is less likely to overflow from the coloring die even when pressurized.

[0016] (Details of the embodiments of the present disclosure) Specific examples of the method for manufacturing an optical fiber according to an embodiment of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0017] In addition, in the description of this embodiment, for convenience of explanation, the "vertical direction" will be referred to as appropriate. Here, the "vertical direction" includes the "upward direction" and the "downward direction." The symbol U shown in the drawings described below indicates the upward direction. The symbol D indicates the downward direction.

[0018] 1 is a schematic diagram of an apparatus 1 for manufacturing an optical fiber G2. The apparatus 1 for manufacturing an optical fiber G2 applies the method for manufacturing an optical fiber G2 according to this embodiment to a coloring step of coating the outer periphery of an optical fiber G1 with a colored resin.

[0019] 1, an apparatus 1 for manufacturing an optical fiber G2 includes a die unit 2 that applies a colored resin to an optical fiber G1, and an ultraviolet irradiation device 3 that irradiates the applied colored resin with ultraviolet light. A guide roller 11 is attached above the die unit 2 to guide the optical fiber G1 paid out from a payout bobbin (not shown) to the die unit 2. A guide roller 12 is provided below the ultraviolet irradiation device 3 to guide the optical fiber G2 formed by irradiating it with ultraviolet light to a take-up bobbin (not shown).

[0020] The die unit 2 includes a coloring die 23, a receiving portion 22, and a cover portion 21. The cover portion 21, receiving portion 22, and coloring die 23 are arranged in this order in the direction in which the optical fiber G1 enters the die unit 2 (from top to bottom). The cover portion 21 is preferably attached so as to cover an inlet 23a, which will be described later. The cover portion 21 has a hole for passing the optical fiber G1 through. The receiving portion 22 has an upper resin reservoir 221 therein capable of containing a colored resin. Similarly, the coloring die 23 has a lower resin reservoir 231 therein capable of containing a colored resin. The coloring die 23 has an inlet 23a therein, which is a passage through which the optical fiber G1 can be placed. The upper resin reservoir 221 and the lower resin reservoir 231 are connected by the inlet 23a. The coloring die 23 is further provided with an outlet port 23b through which the optical fiber G1 can be taken out.

[0021] A supply tank ST is connected to the coloring die 23 via a supply pipe SP. The supply tank ST supplies the colored resin stored therein by flowing it into the lower resin reservoir 231 through the supply port of the coloring die 23. The supply tank ST is preferably positioned so that the height of the colored resin liquid level F2 in the supply tank ST is higher than the height of the colored resin liquid level F1 in the coloring die 23. However, if the colored resin that overflows from inside the coloring die 23 can be temporarily held by the receiver 22 as shown in FIG. 1, the colored resin liquid level F1 in the receiver 22 is considered to be the colored resin liquid level in the coloring die 23.

[0022] The colored resin applied to the optical fiber G1 may be, for example, an ultraviolet-curable resin containing a pigment for coloring. The colored resin supplied from a supply tank ST is applied to the outer periphery of the optical fiber G1 passing through the coloring die 23. In this example, the optical fiber G1 refers to a glass fiber formed by drawing a preform (optical fiber base material), the outer periphery of which is coated with a coating layer (for example, a primary resin and a secondary resin).

[0023] The upper resin reservoir 221 of the receiving section 22 can temporarily store the colored resin that overflows from the coloring die 23. A recovery tank DT that recovers the temporarily stored colored resin is connected to the upper resin reservoir 221 via a recovery pipe DP. The recovery tank DT is preferably positioned so that the height of the liquid surface F3 of the colored resin in the recovery tank DT is lower than the height of the liquid surface F1 of the colored resin in the coloring die 23.

[0024] A pressure gauge 24 is provided at the connection between the coloring die 23 and the supply pipe SP. A heater 25 is attached to a part of the supply pipe SP. The heater 25 is connected to a control unit 26. The control unit 26 can raise and lower the temperature of the colored resin inside the coloring die 23 by controlling the temperature of the heater 25.

[0025] In addition to the heater 25, the control unit 26 may be connected to, for example, a capstan (not shown) provided downstream of the guide roller 12. For example, the control unit 26 may control the capstan to change the running speed (linear speed) of the optical fiber G1 in the manufacturing apparatus 1. The control unit 26 may also be connected to a pump (not shown) that sends colored resin from the supply tank ST toward the coloring die 23, and may control the pressure inside the coloring die 23.

[0026] The ultraviolet irradiation device 3 is a device that irradiates ultraviolet rays onto the optical fiber G1 coated with the colored resin to harden the colored resin. The ultraviolet irradiation device 3 is configured, for example, with a single-stage or multi-stage ultraviolet irradiation furnace.

[0027] Next, a method for manufacturing an optical fiber using the manufacturing apparatus 1 will be described. First, when the coloring process, which is part of the optical fiber manufacturing process, begins, the optical fiber G1 begins to be unwound from the unwound bobbin, enters the coloring die 23, and is set on the path to the take-up bobbin.

[0028] When the coloring process starts, the drawing speed of the optical fiber G1 becomes greater than zero and increases to a predetermined drawing speed. A coloring resin supplied from a supply tank ST through a supply pipe SP is applied to the outer periphery of the optical fiber G1 that has entered the coloring die 23. The optical fiber G1 with the coloring resin applied thereto is drawn out of the coloring die 23.

[0029] The optical fiber G1 drawn out from the coloring die 23 is sent to the ultraviolet irradiation device 3. When ultraviolet light is irradiated onto the optical fiber G1 fed into the ultraviolet irradiation device 3 (irradiation furnace), the colored resin applied to the outer periphery of the optical fiber G1 is cured to form a colored layer. After being drawn out from the ultraviolet irradiation device 3, the optical fiber G2 produced in this manner is wound onto a take-up bobbin (not shown) via a guide roller 12.

[0030] When the colored layer is formed for a predetermined length, the drawing speed of the optical fiber G1 is reduced to terminate the coloring process. When the drawing speed of the optical fiber G1 becomes 0 (i.e., the drawing speed stops), the process proceeds to a standby process. In the standby process, for example, replacement of the payout bobbin of the optical fiber G1 may be performed. The standby process may take, for example, several tens of minutes or more. For example, even when replacement of the payout bobbin of the optical fiber G1 is performed, the coloring die 23 remains positioned on the pass line during the standby process.

[0031] Furthermore, in the standby step, the optical fiber G1 may be stopped in a state in which it is passed through the passage openings (the inlet opening 23a and the outlet opening 23b) provided in the coloring die 23. For example, when the payout bobbin of the optical fiber G1 is replaced, it is preferable to maintain the state in which the optical fiber G1 is passed through the inlet opening 23a and the outlet opening 23b as much as possible by cutting the optical fiber G1 before or after the coloring die 23, for example. Note that a state in which the optical fiber G1 is not on the path line due to, for example, replacement of the payout bobbin also corresponds to the drawing speed stop state.

[0032] Furthermore, the control unit 26 may change the control of the operation of the heater 25 between the coloring process and the standby process. For example, the control unit 26 may monitor the temperature of the colored resin inside the coloring die 23 and operate the heater 25 so that the temperature of the colored resin in the standby process is lower than the temperature of the colored resin in the coloring process.

[0033] (Colored resin supply pressure) Next, the supply pressure of the colored resin of the coloring die 23 according to this embodiment (hereinafter referred to as resin pressure) will be described. FIG. 2 shows the relationship between the drawing speed and time in the manufacturing method of the optical fiber G2, and the relationship between the resin pressure and time in the manufacturing method of the optical fiber G2 and a comparative example. The resin pressure is the gauge pressure of the colored resin at the supply port of the coloring die 23. The resin pressure is measured using a pressure gauge 24 attached between the coloring die 23 and the supply pipe SP. Alternatively, the resin pressure may be calculated from the difference between the height of the colored resin liquid surface F2 in the supply tank ST and the height of the colored resin liquid surface F1 in the coloring die 23, the density of the colored resin, and the gauge pressure inside the supply tank ST. In addition, in the graph of supply pressure in FIG. 2, the solid line graph shows the resin pressure when the optical fiber G2 is manufactured using the method of this embodiment, and the dashed line graph shows the resin pressure when the optical fiber G2 is manufactured using the comparative example method described below.

[0034] At time t0, the coloring process is started. When the coloring process is started, the drawing speed of the optical fiber G1 increases from 0 to V1 between time t0 and time t1. In response to this, the resin pressure is increased from pressure P1 (>0) to pressure P2. From time t1 to time t2, the optical fiber G1 travels at a constant linear velocity V1, and the resin pressure is maintained at a constant pressure P2. From time t2 to time t3, in order to complete the coloring step, the drawing speed of the optical fiber G1 is reduced from V1 to 0. Correspondingly, the resin pressure is reduced from pressure P2 to pressure P1. When the coloring step is completed at time t3, the process proceeds to the standby step. In the standby step, the drawing speed of the optical fiber G1 is 0, but it is desirable to maintain the resin pressure at P1. In other words, the resin pressure is positive even in the standby step.

[0035] When the coloring step is started again at time t4, the drawing speed and resin pressure of the optical fiber G1 are controlled until time t7 in the same manner as in the coloring step from time t0 to time t3.

[0036] At time t7, the standby process starts again. As in the standby process from time t3 to time t4, in the standby process from time t7 to time t8, the drawing speed of the optical fiber G1 is 0, but the resin pressure is maintained at pressure P1. In other words, in the standby process from time t7 to time t8, the resin pressure is positive.

[0037] When the coloring process is resumed at time t8, the resin pressure remains positive, as at time t4. When the coloring process and the standby process are repeated thereafter, the drawing speed of the optical fiber G1 and the resin pressure are controlled in the same manner for the coloring process from time t0 to time t3 and the standby process from time t3 to time t4.

[0038] (Comparative Example) Next, a comparative example will be described with respect to the above-described embodiment. The comparative example is based on the manufacturing method of an optical fiber core described in Patent Document 1. In the comparative example, the drawing speed of the optical fiber core at each time t0 to t9 is the same as that of the embodiment. However, the resin pressure at each time t0 to t9 differs from that of the embodiment. For example, in the standby process from time t3 to time t4 or from time t7 to time t8, the resin pressure is 0. Furthermore, as shown by the dashed line graph in Figure 2, at the start times of the coloring process, t0, t4, and t8, the resin pressure is not positive when the coloring process is started.

[0039] However, when applying colored resin to the optical fiber, defective molding parts such as lumps may be formed. Since optical fiber cores with defective molding parts are discarded, it is essential to reduce the number of defective molding parts as much as possible in order to improve yield.

[0040] The inventors have found that the formation of defectively molded portions can be reduced by making improvements to the waiting process, rather than the coloring process. More specifically, the inventors discovered that defective moldings, such as lumps, are caused by air bubbles floating in the colored resin. When the resin pressure is zero during the standby process, as in the comparative example, the colored resin may flow backward through the supply pipe, entraining air into the colored resin. The air entrained in the colored resin becomes air bubbles and floats inside the colored resin. If the coloring process is performed under these conditions, a defective colored layer will be formed.

[0041] According to the manufacturing method of the optical fiber G2 of this embodiment, since the resin pressure of the colored resin in the coloring die 23 is positive even during the standby step, it is possible to prevent the colored resin in the coloring die 23 from flowing back toward the supply port, and it is difficult for bubbles to occur in the colored resin. Since the coloring step is started while maintaining this state, it is possible to prevent the occurrence of defective molding parts in the coloring step and improve the yield.

[0042] In the manufacturing method of the optical fiber G2 of this embodiment, the height of the liquid surface F2 of the colored resin in the supply tank ST is higher than the height of the liquid surface F1 of the colored resin in the coloring die 23. As a result, the colored resin is automatically supplied from the supply tank ST to the coloring die 23, and the resin pressure of the colored resin in the coloring die 23 naturally becomes positive. Therefore, a manufacturing method of the optical fiber G2 can be realized with a simple configuration that suppresses the occurrence of defective molding portions.

[0043] In the standby step of the method for manufacturing the optical fiber G2 of this embodiment, the optical fiber G1 stops while passing through the passage opening, which makes it difficult for the colored resin to overflow from the passage opening even if the resin pressure of the colored resin in the coloring die 23 is positive.

[0044] In the manufacturing method of the optical fiber G2 of this embodiment, the cover portion 21 is attached to the coloring die 23 so as to cover the inlet 23a. This makes it difficult for the colored resin to overflow from the inlet 23a even if the resin pressure in the coloring die 23 is positive.

[0045] In the manufacturing method of the optical fiber G2 of this embodiment, the colored resin that overflows from the inlet 23a is collected. As a result, even if the colored resin overflows from the coloring die 23, the overflowed colored resin can be collected and reused.

[0046] Furthermore, if the liquid level F3 of the colored resin in the recovery tank DT is lower than the height of the liquid level F1 of the colored resin in the coloring die 23, the colored resin inside the upper resin reservoir 221 can be automatically discharged, making it possible to recover the overflowing colored resin with a simple configuration.

[0047] In the manufacturing method of the optical fiber G2 of this embodiment, the temperature of the coloring resin inside the coloring die 23 during the waiting process is controlled to be lower than the temperature of the coloring resin inside the coloring die 23 during the coloring process. Generally, the viscosity of coloring resin increases as the temperature decreases. By controlling the temperature of the coloring resin in this embodiment, the viscosity of the coloring resin during the waiting process becomes higher than the viscosity of the coloring resin during the coloring process. This makes it less likely for the coloring resin to overflow from the coloring die 23 even when the resin pressure is positive.

[0048] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure.

[0049] For example, the means for applying positive pressure to the colored resin in the coloring die is not limited to the example of this embodiment. For example, applying positive pressure to the colored resin can be achieved by a known method, such as providing a pump in a supply tank or supply pipe to send the resin to the coloring die, or by supplying an inert gas into the supply tank to pressurize the inside of the supply tank. [Explanation of symbols]

[0050] 1 Manufacturing equipment 2 Dice Unit 3 Ultraviolet irradiation device 21 Cover 22 Receiving part 23 colored dice 23a Entrance 23b Exit 24 Pressure gauge 25 Heater 26 Control Unit DP recovery pipe DT Recovery Tank F1,F2,F3 liquid level G1 optical fiber G2 optical fiber core SP supply pipe ST Supply Tank

Claims

1. a coloring step of passing an optical fiber through a passage opening of a coloring die into which a colored resin is supplied from a supply opening, thereby forming a colored layer on the outer periphery of the optical fiber, thereby producing an optical fiber core; a standby step of disposing the coloring die on a pass line through which the optical fiber passes in the coloring step while the optical fiber is in a stopped state of drawing speed, In the waiting step, the resin pressure of the colored resin in the coloring die is positive pressure, A method for manufacturing an optical fiber core, wherein the coloring step is started while the resin pressure of the colored resin is kept positive.

2. 2. The method for manufacturing an optical fiber according to claim 1, wherein a liquid level of the colored resin in a supply tank that supplies the colored resin to the coloring die is higher than a liquid level of the colored resin in the coloring die.

3. In the waiting step, the optical fiber is stopped in a state where it passes through the passage opening.

3. The method for manufacturing an optical fiber according to claim 1.

4. the passage opening has an entrance opening through which the optical fiber enters the coloring die; In the waiting step, a cover portion for covering the wire inlet is attached to the coloring die. The method for manufacturing an optical fiber according to any one of claims 1 to 3.

5. the passage opening has an entrance opening through which the optical fiber enters the coloring die, Collecting the colored resin that has overflowed from the inlet. The method for manufacturing the optical fiber according to any one of claims 1 to 4.

6. The temperature of the colored resin inside the coloring die in the waiting step is controlled to be lower than the temperature of the colored resin inside the coloring die in the coloring step. The method for manufacturing the optical fiber according to any one of claims 1 to 5.

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