Method for manufacturing an optical fiber

Abstract

A method for manufacturing an optical fiber, comprising coating a first resin onto a glass fiber drawn from a glass matrix and curing the first resin to form a first coated optical fiber, comprising: a first step in which the glass fiber is traveled at a first speed during a first period; a second step in which the speed of the glass fiber is increased from the first speed to a second speed during a second period after the first period; and a third step in which the speed of the glass fiber is maintained at the second speed during a third period after the second period, wherein the thickness of the first coating in the second step from the start of coating the first resin to reaching a third speed that is faster than the first speed and slower than the second speed is defined as TB1, and the thickness of the first coating in the third step is defined as TB2, wherein TB2 / TB1 is greater than 1.0 and less than 11.0.

Description

TECHNICAL FIELD

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

[0002] This application claims priority based on Japanese Application No. 2021-073480 filed on April 23, 2021, and all the recitations described in the Japanese application are incorporated by reference. BACKGROUND

[0003] A method for manufacturing an optical fiber is generally configured to coat a resin on the outer periphery of a glass fiber while drawing an optical fiber preform to form the glass fiber, and then to cure the resin by ultraviolet irradiation and to wind up. After the start of drawing, the speed (linear speed) of the glass fiber increases, and the speed of the glass fiber is maintained at a predetermined stable manufacturing linear speed. In addition, the resin is coated on the glass fiber at a certain thickness. One example of a drawing method for an optical fiber is described in Patent Documents 1 and 2. For example, in Patent Document 1, it is described that the supply pressure of the resin is adjusted according to the linear speed.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Publication No. 2001-66476

[0007] Patent Document 2: Japanese Patent Application Publication No. 2003-226556 SUMMARY

[0008] The method for manufacturing an optical fiber of the present disclosure is a method for manufacturing an optical fiber by coating a first resin on a glass fiber obtained by drawing a glass preform, and curing the first resin to become a first coating, and has: a first step of causing the glass fiber to travel at a first speed in a first period; a second step of causing the speed of the glass fiber to increase from the first speed to a second speed in a second period after the first period; and a third step of maintaining the speed of the glass fiber at the second speed in a third period after the second period, and when a thickness of the first coating from the start of coating the first resin to reaching a third speed faster than the first speed and slower than the second speed in the second step is set as TB1, and a thickness of the first coating in the third step is set as TB2, TB2 / TB1 is greater than 1.0 and is 11.0 or less. BRIEF DESCRIPTION OF DRAWINGS

[0009] [ Figure 1 ] Figure 1 is a schematic view showing a manufacturing apparatus for an optical fiber.

[0010] [ Figure 2 ] Figure 2 is a cross-sectional view of a resin coating apparatus.

[0011] [ Figure 3 ] Figure 3 is a graph showing changes in the speed of the glass fiber, changes in the thickness of the first resin and the second resin in the manufacturing method of the optical fiber to which the embodiments relate.

[0012] [ Figure 4 ] Figure 4 is a cross-sectional view of the optical fiber at the time of good portion manufacturing.

[0013] [ Figure 5 ] Figure 5 is a graph showing the relationship between the thickness ratio and the occurrence probability of breakage. DETAILED DESCRIPTION

[0014] [Problem to be Solved by the Invention]

[0015] When drawing an optical fiber, the transmission characteristics easily deviate from the predetermined good range before the speed (linear velocity) of the glass fiber reaches the stable manufacturing linear velocity, and therefore, this portion is usually removed from the good portion of the optical fiber as a defective portion and discarded. Therefore, the resin coated before the speed of the glass fiber reaches the stable manufacturing linear velocity becomes a waste. If the coating amount of the resin of such a defective portion is reduced, the waste of the resin can be saved, but if the coating amount is simply reduced, the glass fiber comes into contact with the outside air, damage is easily caused, and breakage can occur in the rise of the linear velocity. When breakage occurs in the rise of the linear velocity, it is necessary to start from the drawing operation of the optical fiber parent material again, and the yield is greatly reduced.

[0016] An object of the present disclosure is to provide a manufacturing method of an optical fiber capable of reducing the waste of resin while avoiding the occurrence of breakage.

[0017] [Effects of the Invention]

[0018] According to the present disclosure, it is possible to reduce the waste of resin while avoiding the occurrence of breakage.

[0019] The following describes the modes for carrying out the invention.

[0020] [Explanation of Embodiments of the Invention]

[0021] First, the embodiments of the present disclosure are exemplified and explained.

[0022] 〔1〕One embodiment of the present disclosure relates to a method for manufacturing an optical fiber, which is a method for manufacturing an optical fiber by coating a first resin on a glass fiber obtained by drawing a glass parent material and curing the first resin to be a first coating, the method including: a first step of causing the glass fiber to travel at a first speed in a first period; a second step of increasing the speed of the glass fiber from the first speed to a second speed in a second period after the first period; and a third step of maintaining the speed of the glass fiber at the second speed in a third period after the second period, wherein, when a thickness of the first coating from the start of coating the first resin to reaching a third speed that is faster than the first speed and slower than the second speed in the second step is set to TB1 and a thickness of the first coating in the third step is set to TB2, TB2 / TB1 is greater than 1.0 and is 11.0 or less.

[0023] The ratio of the thickness TB2 of the first coating on the glass fiber in the third step to the thickness TB1 of the first coating from the start of coating the first resin to reaching the third speed that is faster than the first speed and slower than the second speed in the second step is greater than 1.0. That is, the first resin coated on the glass fiber in the second step is less than the first resin coated on the glass fiber in the third step. Thus, the amount of the first resin contained in the defective portion removed from the optical fiber can be reduced, and thus waste can be reduced. In addition, if the ratio TB2 / TB1 is 11.0 or less, it is known from experiments by the present inventor that even if the amount of the first resin is reduced, the occurrence of breakage in the speed increase of the glass fiber can be suppressed.

[0024] 〔2〕In〔1〕, in the second step, the thickness of the first coating can be adjusted by adjusting the coating pressure of the first resin to the glass fiber. In this case, the thickness of the first resin is easily adjusted with high precision.

[0025] 〔3〕In〔1〕or〔2〕, in the second step, the coating of the first resin to the glass fiber can be started when the speed of the glass fiber is 0.2 times or less of the second speed. In this case, the entry of bubbles between the first resin and the glass fiber is easily suppressed.

[0026] 〔4〕In〔1〕to〔3〕, the third speed can be 0.95 times or less of the second speed. In this case, the first resin is easily coated stably between the speed of the glass fiber reaching the third speed and reaching the second speed, and the occurrence of breakage is easily suppressed.

[0027] [5] In [1] to [4], the increase in the thickness of the first coating per 10 seconds from the time the speed of the glass fiber reaches the third speed to the time the second speed can be up to 1.00 μm. In this case, the first resin can be applied stably and the occurrence of wire breakage can be easily suppressed.

[0028] [6] In [1] to [5], the first step may include a threading step of hanging the front end of the glass fiber on a pick-up device via a first mold and a second mold, wherein the pick-up device is positioned downstream of the glass fiber in the direction of travel, closer to the second mold. The second step may include: a step of applying a second resin to the outer side of the glass fiber through the second mold; and a threading step of hanging the front end of the glass fiber coated with the second resin on a winding device, wherein the winding device is positioned downstream of the glass fiber in the direction of travel, closer to the pick-up device. In this case, at the start of drawing, the front end of the glass fiber can be hung on the pick-up device and the winding device.

[0029] [7] In [6], the first resin can be filled into the first mold before the wire-hanging process, and the first resin can be coated onto the glass fiber during the wire-hanging process. In this case, the first mold does not need to be replaced each time the glass substrate is replaced, and even if air bubbles are mixed into the first resin in the first mold, the air bubbles are easily detached as the glass fiber speed increases.

[0030] [8] In [6] or [7], before the wire-hanging process, the second resin is filled into the second mold, and during the wire-hanging process, the second resin is coated onto the glass fiber. In this case, the second mold may not need to be replaced each time the glass substrate is replaced, and even if air bubbles are mixed into the second resin in the second mold, the air bubbles are easily detached as the glass fiber speed increases.

[0031] [9] Another aspect of this disclosure relates to a method for manufacturing an optical fiber by coating a first resin onto a glass fiber drawn from a glass matrix and curing the first resin to form a first coated optical fiber, comprising: a first step of causing the glass fiber to travel at a first speed during a first period; a second step of increasing the speed of the glass fiber from the first speed to a second speed during a second period following the first period; and a third step of maintaining the speed of the glass fiber at the second speed during a third period following the second period, wherein the first resin is applied to the glass fiber in the second step. When the thickness of the first coating from the first resin up to a third speed that is faster than the first speed and slower than the second speed is set to TB1, and the thickness of the first coating in the third step is set to TB2, TB2 / TB1 is greater than 1.0 and less than 11.0. In the second step, there is a step of starting to coat the first resin onto the glass fiber when the speed of the glass fiber is less than 0.2 times the second speed, and the increase in the thickness of the first coating from the speed of the glass fiber from the third speed up to the second speed is at most 1.00 μm per 10 seconds.

[0032] By ensuring the ratio of TB2 / TB1 is greater than 1.0 and less than 11.0, resin waste can be reduced while preventing wire breakage. Furthermore, it facilitates the suppression of air bubbles entrapment between the first resin and the glass fiber. Additionally, it facilitates stable coating of the first resin and further reduces the likelihood of wire breakage.

[0033] [Detailed Description of Embodiments of this Disclosure]

[0034] The embodiments of this disclosure will be described in detail below, but the embodiments are not limited to these. It should be noted that in this specification and drawings, for constituent elements that have substantially the same functional configuration, repeated descriptions are sometimes omitted by using the same symbols.

[0035] First, the optical fiber manufacturing apparatus applicable to the optical fiber manufacturing method of the embodiment will be described. Figure 1 This is a schematic diagram showing an optical fiber manufacturing apparatus.

[0036] like Figure 1 As shown, in the optical fiber manufacturing apparatus 100, firstly, the lower end of the optical fiber preform 1 is melted and drawn by heating it in the drawing furnace 2. The glass fiber G1 formed by drawing is then directed along the direction of travel of the glass fiber G1 (…). Figure 1The cooling device 8, located downstream of the drawing furnace 2 (in the direction of arrow A), passes through the resin coating device 3. The outer diameter of the glass fiber G1 is adjusted to be smaller than the first mold hole 31a of the first mold 31 and the second mold hole 32a of the second mold 32, as described later. The optical fiber parent material 1 is an example of a glass parent material.

[0037] A resin supply device 10 is connected to the resin coating apparatus 3 to supply resin for coating the glass fiber G1. By passing the glass fiber G1 through the resin coating apparatus 3, two layers of resin are coated on the outer periphery of the glass fiber G1.

[0038] Resin-coated glass fiber G1 is cured by a resin curing device 4 (e.g., an ultraviolet irradiation device) located downstream of the resin coating device 3, thereby forming optical fiber G2. Optical fiber G2 is wound onto a take-up drum 7 via guide rollers 5 and a winch 6. The winch 6 is an example of a pickup device, and the take-up drum 7 is an example of a winding device.

[0039] Next, the resin coating apparatus 3 will be described. Figure 2 This is a cross-sectional view of a resin coating apparatus as an example.

[0040] like Figure 2 As shown, the resin coating apparatus 3 includes a first mold 31 for coating a first resin 21 around the outer periphery of the glass fiber G1, and a second mold 32 for coating a second resin 22 around the outer periphery of the first resin 21. For example, the first mold 31 and the second mold 32 are integrally assembled. The resin coating apparatus 3 is an apparatus for coating the first resin 21 and the second resin 22 around the glass fiber G1 together, but the first resin 21 and the second resin 22 can also be coated separately.

[0041] The first mold 31 is generally cylindrical, and a first mold hole 31a is provided in its central part for the glass fiber G1 and the first resin 21 to pass through. For example, the upstream portion of the first mold hole 31a is formed into a cone shape, and the downstream portion is formed into the same shape.

[0042] The second mold 32 is generally cylindrical, and a second mold hole 32a is provided in its central portion for the passage of glass fiber G1 coated with the first resin 21 and the second resin 22. For example, the upstream portion of the second mold hole 32a is formed into a cone shape, and the downstream portion is formed into the same shape. The second mold 32 is disposed downstream of the first mold 31. A second connecting flow path 32b is formed in the upper part of the second mold 32, forming part of the flow path through which the second resin 22 flows. The second connecting flow path 32b is formed continuously with the second mold hole 32a.

[0043] A nipple 33 for introducing glass fiber G1 into the first mold 31 is provided on the upstream side of the first mold 31. The nipple 33 is formed in a generally cylindrical shape, and a tapered through hole 33a is provided in its central part for the glass fiber G1 to pass through. In addition, a first connecting flow path 33b is formed at the lower part of the nipple 33, forming part of the flow path through the first resin 21. The first connecting flow path 33b is formed continuously with the through hole 33a.

[0044] A cylindrical dieholder 34 is provided on the outer periphery of the pipe connector 33, the first mold 31, and the second mold 32. The pipe connector 33, the first mold 31, and the second mold 32 are housed within the dieholder 34 with their respective outer peripheral surfaces fitting seamlessly into the inner peripheral surface of the dieholder 34. In this housed state, the gap formed between the first connecting flow path 33b of the pipe connector 33 and the upper surface of the first mold 31 functions as a first resin flow path 35 through which the first resin 21 flows. Furthermore, the gap formed between the lower surface of the first mold 31 and the second connecting flow path 32b of the second mold 32 functions as a second resin flow path 36 through which the second resin 22 flows. A through hole 37 communicating with the first resin flow path 35 and a through hole 38 communicating with the second resin flow path 36 are formed on the side wall of the dieholder 34. The second resin flow path 36 is located downstream of the glass fiber G1 in the direction of travel of the first resin flow path 35.

[0045] The front end of the first resin supply tube 39, used to supply the first resin 21, is connected to the through hole 37. The base end of the first resin supply tube 39 is connected to the resin supply device 10 (see reference). Figure 1 The first resin supply source is connected. Additionally, the front end of the second resin supply pipe 40 for supplying the second resin 22 is connected to the through hole 38. The base end of this second resin supply pipe 40 is connected to the second resin supply source of the resin supply device 10. The first resin 21 is supplied from the resin supply device 10 to the first resin flow path 35 via the first resin supply pipe 39 and the through hole 37, and the second resin 22 is supplied from the resin supply device 10 to the second resin flow path 36 via the second resin supply pipe 40 and the through hole 38. Then, the first resin 21 is coated onto the glass fiber G1 using a first mold 31 filled with the first resin 21 in the first resin flow path 35, and the second resin 22 is coated onto the glass fiber G1 using a second mold 32 filled with the second resin 22 in the second resin flow path 36. The first resin 21 and the second resin 22 are, for example, UV-curable resins, and are cured by irradiation with ultraviolet light after coating.

[0046] Next, the detailed description of the optical fiber manufacturing method according to the embodiment will be provided. In this embodiment, an optical fiber G2 is manufactured with a good portion having a first coating with a thickness TB equal to the thickness TB2 surrounding the glass fiber G1, and a second coating with a thickness TC equal to the thickness TC1 surrounding the first coating. It should be noted that, as described above, the optical fiber manufactured before reaching a stable manufacturing line speed is considered a defective portion. Figure 3 It is a graph that shows the variation of the speed (linear speed) V of the glass fiber in the optical fiber manufacturing method according to the embodiment, and the variation of the thickness of the first coating and the second coating applied to the glass fiber. Figure 3 The horizontal axis in the graph represents time t. Figure 3 The speed V of the glass fiber G1 is the speed inside the resin coating device 3. Figure 3 The thicknesses TB of the first coating and TC of the second coating are the thicknesses after the resin is applied by the resin coating device 3 and cured by the resin curing device 4.

[0047] First, the change in the speed V of the glass fiber G1 will be explained. In this embodiment, at time t0, it is assumed that the leading end of the glass fiber G1 is hung on the winch 6 via the cooling device 8, the resin coating device 3, the resin curing device 4, and the guide roller 5. The glass fiber G1 is drawn from the lower end of the optical fiber parent material 1, and the speed V of the glass fiber G1 is maintained at speed V1 until time t2. It should be noted that the speed V1 may not be constant and may vary slightly. Time t1 is the time when the second resin 22 is coated, as will be described later. After time t1, the resin-coated optical fiber G2 is hung from the winch 6 onto the winding spool 7 and wound onto the winding spool 7. Then, between time t2 and time t5, the speed V of the glass fiber G1 increases to speed V2. Then, after time t5, the speed V of the glass fiber G1 is maintained at speed V2. Speed ​​V2 is the stable manufacturing line speed. After time t5, the optical fiber G2 is wound as a good part. The speed V2 is, for example, between 2000 m / min and 3000 m / min. Furthermore, the fiber G2 wound between time t0 and time t5 is discarded as a defect in subsequent processes. The period from time t0 to time t2 is an example of the first period, the period from time t2 to time t5 is an example of the second period, and the period after time t5 is an example of the third period. Additionally, speed V1 is an example of the first speed, and speed V2 is an example of the second speed.

[0048] Next, the changes in the thickness TB of the first coating and the thickness TC of the second coating will be explained. From time t0 to time t1, the coating of the first resin 21 and the second resin 22 is not performed. Then, at time t1, the coating of the second resin 22 begins. The amount of the second resin 22 applied increases from time t1 to time t5, so that at time t5, the thickness TC of the second coating reaches thickness TC1. The coating of the first resin 21 does not begin at time t1, but begins at time t3, after time t2. Therefore, from time t1 to time t3, the second resin 22 is directly coated onto the glass fiber G1.

[0049] Between time t3 and time t5, until time t4 when the speed V of glass fiber G1 becomes speed V3, which is faster than speed V1 but slower than speed V2, the coating amount of the first resin 21 is adjusted to a first coating thickness TB, known as thickness TB1. The relationship between thickness TB1 and thickness TB2 holds: "1.0 < TB2 / TB1 ≤ 11.0". That is, thickness TB1 is a thickness whose ratio to thickness TB2 is greater than 1.0 and less than 11.0. When coating the first resin 21 begins at time t3, the first resin 21 is directly coated onto the glass fiber G1, and the second resin 22 is coated on top of it. That is, the first resin 21 and the second resin 22 are coated together on the glass fiber G1. It should be noted that the thickness TB1 does not need to be constant; it can vary as long as the relationship "1.0 < TB2 / TB1 ≤ 11.0" holds. For example, the thickness TB1 can be gradually increased. Speed ​​V3 is an example of a third speed.

[0050] Then, the coating amount of the first resin 21 increases from time t4 to time t5, so that the thickness TB of the first coating reaches the thickness TB2 at time t5.

[0051] Then, after time t5, the speed V of glass fiber G1 is maintained at speed V2, the thickness TB of the first coating is maintained at thickness TB2, and the thickness TC of the second coating is maintained at thickness TC1. That is, after time t5, optical fiber G2 manufactures the good part at a stable manufacturing line speed. Figure 4 This is a cross-sectional view of the well-manufactured G2 optical fiber. Figure 4 , the reference code 21X indicates the first coating in the good part, and the reference code 22X indicates the second coating.

[0052] The first resin 21 and the second resin 22 coated on the glass fiber G1 are cured by ultraviolet irradiation in the resin curing apparatus 4. It should be noted that the first resin 21 and the second resin 22 coated between time t1 and time t5 are less numerous and thinner than those coated after time t5. Therefore, the power of the ultraviolet light used to cure the first resin 21 and the second resin 22 coated between time t1 and time t5 can also be lower than the power of the ultraviolet light used to cure the first resin 21 and the second resin 22 coated after time t5. By reducing the power, effects such as reduced power consumption, extended lifespan of the ultraviolet source, and suppression of bleeding in the quartz tube within the resin curing apparatus 4 can be achieved.

[0053] In the optical fiber G2 manufactured according to this embodiment, the first resin 21 is not coated between time t0 and time t3, and the relationship between thickness TB1 and thickness TB2 is "1.0 < TB2 / TB1" between time t3 and time t4. Therefore, the amount of first resin 21 coated can be small. Thus, the amount of first resin 21 coated in the defective part can be reduced. However, in order to suppress resin waste, TB2 / TB1 is preferably greater than 2.0, more preferably greater than 5.0. In addition, as will be described later, since the relationship between the thickness TB1 of the first coating in the defective part and the thickness TB2 of the first coating in the good part is "TB2 / TB1 ≤ 11.0", it is possible to suppress the occurrence of wire breakage while reducing the amount of first resin 21 coated in the defective part.

[0054] It should be noted that in the above method, the glass fiber is passed through the mold and coated with resin before filling the mold with resin. However, it is also possible to thread the fiber with the first mold 31 filled with the first resin 21 and the second mold 32 filled with the second resin 22. Normally, the mold is replaced each time the glass matrix is ​​replaced. However, in this way, when drawing the next glass matrix, the first mold 31 and the second mold 32 do not need to be replaced, thus maintaining a high operating rate of the optical fiber manufacturing apparatus 100. Alternatively, the first resin 21 can be thinly coated onto the glass fiber G1 during threading. In this way, even if air bubbles are mixed into the first resin 21 in the first mold 31, the air bubbles are easily dislodged during the increase in fiber speed. Similarly, the second resin 22 can be thinly coated onto the glass fiber G1 during threading. In this way, even if air bubbles are mixed into the second resin 22 in the second mold 32, the air bubbles are easily dislodged during the increase in fiber speed.

[0055] The thickness TB of the first coating can be adjusted, for example, according to the coating conditions of the first resin 21 in the resin coating apparatus 3. When adjusting the thickness TB of the first coating, adjusting the coating pressure is particularly preferable. This is because the thickness TB can be adjusted with high precision. Alternatively, the thickness TB of the first coating can also be adjusted by changing the cooling conditions in the cooling device 8; or by changing both the cooling conditions in the cooling device 8 and the coating conditions of the first resin 21 in the resin coating apparatus 3.

[0056] It should be noted that if the speed V of the glass fiber G1 is too high when the first resin 21 is first applied, air bubbles can easily become trapped between the glass fiber G1 and the first resin 21, causing damage to the glass fiber and potentially resulting in fiber breakage. For example, if the speed V of the glass fiber G1 exceeds 0.2 times the speed V2 when the first resin 21 is applied, fiber breakage is likely to occur. Therefore, the speed Vp of the glass fiber G1 at the time t3 when the first resin 21 is first applied is preferably 0.2 times or less than the speed V2. That is, it is preferable to begin applying the first resin 21 to the glass fiber G1 when the speed V of the glass fiber G1 is 0.2 times or less than the speed V2. Furthermore, the speed Vp of the glass fiber G1 at the time t3 when the first resin 21 is first applied is more preferably 0.1 times or less than the speed V2. It should be noted that the lower limit of the speed Vp is the speed V1.

[0057] Furthermore, when the difference between speed V3 and speed V2 is small, the time it takes for speed V to increase from speed V3 to speed V2, i.e., the time between time t4 and time t5, is shortened. Therefore, when the thickness TB1 of the first coating at time t4 is significantly smaller than the thickness TB2, for example, about 0.1 times, increasing the thickness TB of the first coating from thickness TB1 to thickness TB2 in a short time may cause the coating of the first resin 21 to become unstable and prone to breakage. For example, when speed V3 exceeds 0.95 times speed V2, breakage may easily occur. Therefore, speed V3 is preferably 0.95 times or less than speed V2, more preferably 0.90 times or less, and even more preferably 0.80 times or less. It should be noted that, in order to obtain the effect of reducing resin waste, speed V3 is preferably about 0.5 times or more than speed V2.

[0058] Furthermore, from the viewpoint of suppressing line breakage, the increase in the thickness TB of the first coating every 10 seconds is preferably 1.00 μm, more preferably 0.80 μm or less, and even more preferably 0.60 μm or less. For example, even if there is a moment when the thickness TB of the first coating increases sharply due to the stepwise supply of the first resin 21, the increase within 10 seconds including that moment is preferably 1.00 μm or less. It should be noted that, in order to achieve the effect of reducing resin waste, the increase in the thickness TB of the first coating every 10 seconds is preferably 0.10 μm or more.

[0059] It should be noted that, in Figure 3 In the process, the thicknesses TB of the first coating and TC of the second coating vary linearly, but the variations of the thicknesses TB of the first coating and TC of the second coating may not be linear.

[0060] Here, the experiments conducted by the inventors of this application are described.

[0061] In this experiment, optical fibers were manufactured under various conditions with different ratios of thickness TB2 to thickness TB1 (TB2 / TB1), following the method described above. The probability of wire breakage was then investigated for each condition. The probability of wire breakage referred to here is the percentage (%) of the number of wire breaks occurring during the rise in wire speed. The results are as follows: Figure 5 As shown. Figure 5 The horizontal axis represents the ratio of thickness TB2 to thickness TB1 (TB2 / TB1), and the vertical axis represents the probability of line breakage.

[0062] like Figure 5 As shown, if the ratio (TB2 / TB1) is 11.0 or less, the probability of line breakage is as low as 20% or less. Furthermore, if the ratio (TB2 / TB1) is 10.0 or less, the probability of line breakage is further reduced to approximately 10% or less. Therefore, the ratio (TB2 / TB1) is preferably 10.0 or less.

[0063] The embodiments have been described in detail above, but are not limited to specific embodiments. Various modifications and alterations can be made within the scope of the claims.

[0064] Explanation of symbols

[0065] 1: Fiber Optic Matrices

[0066] 2: Wire drawing furnace

[0067] 3: Resin Coating Device

[0068] 4: Resin curing device

[0069] 5: Guide rollers

[0070] 6: Winch

[0071] 7: Roll

[0072] 8: Cooling device

[0073] 10: Resin supply device

[0074] 21: First Resin

[0075] 21X: 1st cover

[0076] 22: Second Resin

[0077] 22X: 2nd cover

[0078] 31: Mold No. 1

[0079] 31a: First mold hole

[0080] 32: Mold No. 2

[0081] 32a: Second mold hole

[0082] 32b: Second connection path

[0083] 33: Pipe fitting

[0084] 33a: Hole

[0085] 33b: First connection path

[0086] 34: Mold support

[0087] 35: First resin flow path

[0088] 36: Second resin flow path

[0089] 37: Through hole

[0090] 38: Through hole

[0091] 39: First Resin Supply Pipe

[0092] 40: Second resin supply pipe

[0093] 100: Manufacturing equipment

[0094] A: Arrow

[0095] G1: Glass fiber

[0096] G2: Fiber Optic

[0097] TC1, TB1, TB2: Thickness

Claims

1. A method for manufacturing an optical fiber, comprising coating a first resin onto glass fibers drawn from a glass matrix and curing the first resin to form a first coated optical fiber, comprising: During the first period, a first step is performed in which the glass fiber is moved at a first speed; In the second period following the first period, a second step is performed to increase the speed of the glass fiber from the first speed to the second speed; and In the third period following the second period, the speed of the glass fiber is maintained at the second speed in the third process. When the thickness of the first coating in the second step, from the start of coating the first resin until a third speed, which is faster than the first speed but slower than the second speed, is defined as TB1, and the thickness of the first coating in the third step is defined as TB2, TB2 / TB1 is greater than 1.0 and less than 11.

0.

2. The method for manufacturing optical fiber according to claim 1, wherein, In the second step, the thickness of the first coating is adjusted by adjusting the coating pressure of the first resin onto the glass fiber.

3. The method for manufacturing optical fiber according to claim 1 or claim 2, wherein, In the second step, when the speed of the glass fiber is less than 0.2 times the second speed, the first resin is applied to the glass fiber.

4. The method for manufacturing optical fiber according to claim 1 or claim 2, wherein, The third speed is less than 0.95 times the second speed.

5. The method for manufacturing optical fiber according to claim 1 or claim 2, wherein, The maximum increase in the thickness of the first coating per 10 seconds from the time the speed of the glass fiber reaches the third speed to the time it reaches the second speed is 1.00 μm.

6. The method for manufacturing optical fiber according to claim 1 or claim 2, wherein, The first step includes a threading step of hanging the front end of the glass fiber on a pickup device via a first mold and a second mold, wherein the pickup device is positioned downstream of the glass fiber in the direction of travel, closer to the second mold. The second process includes: The process of applying the second resin to the outer side of the glass fiber using the second mold; and The process of hanging the front end of the glass fiber coated with the second resin on a winding device, wherein the winding device is positioned downstream of the glass fiber in the direction of travel, closer to the pickup device.

7. The method for manufacturing optical fiber according to claim 6, wherein, Before the wire hanging process, the first resin is filled into the first mold. In the wire hanging process, the first resin is coated onto the glass fiber.

8. The method for manufacturing optical fiber according to claim 6, wherein, Before the wire hanging process, the second resin is filled into the second mold. In the wire hanging process, the second resin is coated onto the glass fiber.

9. The method for manufacturing optical fiber according to claim 7, wherein, Before the wire hanging process, the second resin is filled into the second mold. In the wire hanging process, the second resin is coated onto the glass fiber.

10. A method for manufacturing an optical fiber, comprising coating a first resin onto glass fibers drawn from a glass matrix and curing the first resin to form a first coated optical fiber, comprising: During the first period, a first step is performed in which the glass fiber is moved at a first speed; In the second period following the first period, a second step is performed to increase the speed of the glass fiber from the first speed to the second speed; and In the third period following the second period, the speed of the glass fiber is maintained at the second speed in the third process. When the thickness of the first coating in the second step, from the start of coating the first resin until reaching a third speed that is faster than the first speed but slower than the second speed, is defined as TB1, and the thickness of the first coating in the third step is defined as TB2, TB2 / TB1 is greater than 1.0 and less than 11.

0. The second step includes a step of coating the glass fiber with the first resin when the speed of the glass fiber is less than or equal to 0.2 times the second speed. The maximum increase in the thickness of the first coating per 10 seconds from the time the speed of the glass fiber reaches the third speed to the time it reaches the second speed is 1.00 μm.

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