Optical fiber manufacturing method

Abstract

To provide a method for manufacturing an optical fiber capable of suppressing disconnection of an optical fiber and an optical fiber.SOLUTION: A method for manufacturing an optical fiber includes: melting an optical fiber base material and drawing a glass fiber; applying a resin composition to an outer periphery of the glass fiber; and curing the applied resin composition. An amount of eccentricity of a central axis of the glass fiber from a central axis based on an outer periphery of the resin composition or an outer periphery of a coated resin layer formed by curing the resin composition, in a cross-section vertical to the central axis of the glass fiber is measured at 50 points or more over a range of a length of 50 m or more of the glass fiber, and the resin composition is coated such that an average value a of the eccentricity and standard deviation σ satisfy a+3σ≤10 μm.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] An optical fiber including a glass fiber and a resin coating layer covering the outer periphery of the glass fiber is known (for example, Patent Documents 1 to 3). Patent Document 1 describes defining the standard deviation of the outer diameter of the glass part. Patent Document 2 describes a method for detecting uneven thickness of the coating. Patent Document 3 describes a method for online measurement of the eccentricity fluctuation of an optical fiber.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the amount of eccentricity of the glass fiber from the central axis with respect to the outer periphery of the coating resin layer increases, there is a risk that the optical fiber will break.

[0005] An object of the present disclosure is to provide a method for manufacturing an optical fiber and an optical fiber capable of suppressing disconnection of the optical fiber.

Means for Solving the Problems

[0006] A method for manufacturing an optical fiber according to one aspect of the present disclosure comprises the steps of: melting an optical fiber base material and drawing a glass fiber; applying a resin composition to the outer circumference of the glass fiber; and curing the applied resin composition, wherein the eccentricity of the central axis of the glass fiber from the central axis with respect to the outer circumference of the resin composition or the outer circumference of the coating resin layer formed by curing the resin composition is measured at 50 or more points over a length range of 50 m or more of the glass fiber, and the resin composition is applied such that the average value a and standard deviation σ of the eccentricity satisfy a + 3σ ≤ 10 μm.

[0007] An optical fiber according to one aspect of this disclosure comprises a glass fiber and a coating resin layer covering the outer circumference of the glass fiber, wherein when the eccentricity of the central axis of the glass fiber from the central axis with respect to the outer circumference of the coating resin layer is measured at 500 or more points over a length range of 50 km or more of the glass fiber, the average value a and standard deviation σ of the eccentricity satisfy a + 3σ ≤ 10 μm. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a method for manufacturing an optical fiber that can suppress the breakage of the optical fiber, and an optical fiber. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows a cross-section of an optical fiber perpendicular to its length according to the embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view illustrating the definition of eccentricity in glass fibers. [Figure 3] Figure 3 is a flowchart showing a method for manufacturing an optical fiber according to the embodiment. [Figure 4] Figure 4 is a schematic diagram of the manufacturing apparatus used in the optical fiber manufacturing method according to the embodiment. [Figure 5] Figure 5 is a schematic diagram showing an example of an observation image observed by the imaging unit. [Figure 6] Figure 6 is a schematic diagram showing an example of an observation image observed by the imaging unit. [Figure 7] Figure 7 is a graph showing the eccentricity waveform of the glass fiber related to Experimental Example 1. [Figure 8] Figure 8 shows the histogram and cumulative line graph of the eccentricity of the glass fiber related to Experimental Example 1. [Figure 9] Figure 9 is a graph showing the eccentricity waveform of the glass fiber related to Experimental Example 3. [Figure 10] Figure 10 shows the histogram and cumulative line graph of the eccentricity of the glass fiber related to Experimental Example 3. [Modes for carrying out the invention]

[0010] [Description of Embodiments of this Disclosure] First, embodiments of the present disclosure will be listed and described. (1) A method for manufacturing an optical fiber according to one aspect of the present disclosure is a method for manufacturing an optical fiber comprising the steps of: melting an optical fiber base material and drawing a glass fiber; applying a resin composition to the outer circumference of the glass fiber; and curing the applied resin composition, wherein the eccentricity of the central axis of the glass fiber from the central axis with respect to the outer circumference of the resin composition or the outer circumference of the coating resin layer formed by curing the resin composition is measured at 50 or more points over a length range of 50 m or more of the glass fiber, and the resin composition is applied such that the average value a and standard deviation σ of the eccentricity satisfy a + 3σ ≤ 10 μm.

[0011] The above method for manufacturing optical fibers can suppress the eccentricity of glass fibers over a length range of 50m or more.

[0012] (2) In (1) above, the resin composition may be applied such that the histogram of eccentricity shows a single peak shape when the class width is set to 1 μm. In this case, fluctuations (variations) in the eccentricity of the glass fiber are suppressed.

[0013] (3) In the above (1) or (2), the amount of eccentricity may be measured with a sampling period of 20 ms or less. In this case, the amount of eccentricity of the glass fiber can be more reliably suppressed.

[0014] (4) In any of the above (1) to (3), the resin composition may be applied while adjusting the position or inclination of the coating device for applying the resin composition. In this case, the amount of eccentricity of the glass fiber can be adjusted.

[0015] (5) In any of the above (1) to (4), the resin composition may be applied while adjusting the position of the optical fiber preform or the position of the roller that converts the traveling direction of the optical fiber and is disposed directly below the curing device for curing the resin composition. In this case, the amount of eccentricity of the glass fiber can be adjusted.

[0016] (6) In any of the above (1) to (5), the measurement of the amount of eccentricity is performed before the curing step, and the amount of eccentricity may be measured as the amount of eccentricity of the glass fiber from the central axis with respect to the outer periphery of the resin composition. Even in this case, the amount of eccentricity of the glass fiber can be suppressed over the above length range.

[0017] (7) In any of the above (1) to (5), the measuring step is performed after the curing step, and the amount of eccentricity may be measured as the amount of eccentricity of the glass fiber from the central axis with respect to the outer periphery of the coating resin layer. Even in this case, the amount of eccentricity of the glass fiber can be suppressed over the above length range.

[0018] (8) An optical fiber according to one aspect of the present disclosure includes a glass fiber and a coating resin layer that covers the outer periphery of the glass fiber, and when the amount of eccentricity of the central axis of the glass fiber from the central axis with respect to the outer periphery of the coating resin layer is measured at 500 points or more over a length range of 50 km or more of the glass fiber, the average value a and the standard deviation σ of the amount of eccentricity satisfy a + 3σ ≤ 10 μm.

[0019] In the optical fiber described above, the eccentricity of the glass fiber can be suppressed over a length range of 50 km or more.

[0020] (9) In (8) above, the histogram of the eccentricity may show a single peak when the class width is 1 μm. In this case, fluctuations (variations) in the eccentricity of the glass fiber are suppressed.

[0021] [Details of the embodiments of this disclosure] The method for manufacturing an optical fiber and specific examples of optical fibers described herein will be explained below with reference to the drawings. However, the present invention is not limited to these examples, and is intended to include all modifications within the meaning and scope of the claims, as defined by the claims. In the description of the drawings, identical elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0022] (Optical fiber) Figure 1 shows a cross-section of an optical fiber according to an embodiment, perpendicular to the longitudinal direction (axial direction). The optical fiber 1 comprises a glass fiber 10 and a coating resin layer 20 provided on the outer circumference of the glass fiber 10. In recent years, there has been research into reducing the diameter of optical fibers to increase the density of optical cables containing multiple optical fibers. The optical fiber 1 is, for example, a reduced-diameter optical fiber. The diameter of the glass fiber 10 is, for example, 60 μm to 125 μm. The outer diameter of the coating resin layer 20, i.e., the diameter of the optical fiber 1, is, for example, 100 μm to 200 μm. The optical fiber 1 before coating with the colored resin layer is called a "strand," and the optical fiber obtained by coating the optical fiber 1 with the colored resin layer is also called a "core" or "colored core."

[0023] The glass fiber 10 includes a core 12 and a cladding 14. The cladding 14 surrounds the core 12. The core 12 and cladding 14 mainly contain glass such as quartz glass. For example, the core 12 can be made of germanium-doped quartz glass or pure quartz glass. The cladding 14 can be made of pure quartz glass or fluorine-doped quartz glass. Here, pure quartz glass refers to quartz glass that is substantially free of impurities.

[0024] The coating resin layer 20 includes a primary resin layer 22 and a secondary resin layer 24. The primary resin layer 22 is in contact with the outer circumferential surface of the cladding 14 and covers the entire cladding 14. The secondary resin layer 24 is in contact with the outer circumferential surface of the primary resin layer 22 and covers the entire primary resin layer 22. The secondary resin layer 24 constitutes the outermost layer of the coating resin layer 20.

[0025] The primary resin layer 22 and the secondary resin layer 24 are made of cured products of an ultraviolet-curable resin composition. This resin composition contains a urethane (meth)acrylate oligomer, a monomer, and a photopolymerization initiator. Here, (meth)acrylate means acrylate or the corresponding methacrylate. As the monomer, monofunctional monomers having one polymerizable group and polyfunctional monomers having two or more polymerizable groups can be used. Species The above may be mixed and used. As the photopolymerization initiator, it can be appropriately selected from known radical photopolymerization initiators. The resin composition may further contain a silane coupling agent, a photoacid generator, a leveling agent, an antifoaming agent, an antioxidant, etc.

[0026] Figure 2 is a schematic cross-sectional view illustrating the definition of the eccentricity of a glass fiber. As shown in Figure 2, the eccentricity d of the glass fiber 10 is defined as the distance (radial displacement) from the central axis RC, relative to the outer circumference of the coating resin layer 20, to the central axis GC of the glass fiber 10. The central axis GC is also the central axis relative to the inner circumference of the coating resin layer 20. Note that, before the coating resin layer 20 hardens, the central axis RC is set relative to the outer circumference of the resin composition that will become the coating resin layer 20. In other words, the eccentricity d may also be defined as the distance (radial displacement) from the central axis RC, relative to the outer circumference of the resin composition that will become the coating resin layer 20, to the central axis GC of the glass fiber 10.

[0027] In optical fiber 1, when the eccentricity d is measured at 500 or more points over a length range of 50 km or more of glass fiber 10, the mean value a and standard deviation σ of the measured eccentricity d satisfy a + 3σ ≤ 10 μm. The measurement interval is, for example, 100 m or less, more preferably 50 m or less, and even more preferably 1 m or less. In this way, since the eccentricity d is suppressed in optical fiber 1, breakage of the optical fiber 1 can be suppressed. In particular, when the optical fiber 1 is made smaller in diameter, the coating resin layer 20 is thin, so even a slight shift in the position of the glass fiber 10 can easily worsen the eccentricity d. In optical fiber 1, since the eccentricity d is suppressed, breakage of the optical fiber 1 is suppressed.

[0028] The eccentricity d may be measured online during line drawing by, for example, the measurement method performed in the measurement step S5 described later, or it may be measured offline by other known methods. In the optical fiber 1, the histogram of the measured eccentricity shows a single peak shape when the class width is set to 1 μm. The shape of the histogram will be described later.

[0029] (Manufacturing method for optical fibers) Figure 3 is a flowchart illustrating a method for manufacturing an optical fiber according to an embodiment. As shown in Figure 3, the method for manufacturing an optical fiber includes a drawing step S1, a cooling step S2, a coating step S3, a curing step S4, a measurement step S5, and a winding step S6. Steps S1 to S6 are shown in order when focusing on a certain point along the length of the optical fiber 1. In other words, a certain point along the length of the optical fiber 1 is manufactured by going through steps S1 to S6 in order. Note that the measurement step S5 may be performed between the coating step S3 and the winding step S6, or it may be performed before the curing step S4.

[0030] Figure 4 is a schematic diagram of a manufacturing apparatus used in the optical fiber manufacturing method according to the embodiment. As shown in Figure 4, the manufacturing apparatus 30 is an apparatus for manufacturing an optical fiber 1 from an optical fiber matrix 2. The manufacturing apparatus 30 includes a heating furnace 31, a cooling device 32, a die 33, an ultraviolet irradiation device 34, a measuring unit 35, guide rollers 36, 37, a capstan 38, a screening device 39, a dancer roller 40, a winding bobbin 41, and a control unit 42.

[0031] The following describes each step in the manufacturing method of optical fiber 1 with reference to Figures 3 and 4.

[0032] The drawing process S1 is a process in which the optical fiber base material 2 is melted in a heating furnace 31 and the glass fiber 10 is drawn. The heating furnace 31 has a cylindrical furnace core tube 31a into which the optical fiber base material 2 is supplied, and a heating element 31b surrounding the furnace core tube 31a. The heating furnace 31 melts the lower end of the optical fiber base material 2 by heating. The drawing speed is, for example, about 40 m / s.

[0033] Cooling step S2 is a process in which the glass fiber 10 drawn from the lower end of the optical fiber base material 2 is cooled by a cooling device 32. The cooling device 32 is located downstream of the heating furnace 31.

[0034] The coating step S3 is a step in which an ultraviolet-curable resin composition that will become a coating resin layer 20 is applied to the outer circumference of the glass fiber 10 using a die 33. The die 33 is located downstream of the cooling device 32. The die 33 is a coating device for applying the resin composition. In this embodiment, the resin composition that will become the primary resin layer 22 and the resin composition that will become the secondary resin layer 24 are applied sequentially to the outer surface of the glass fiber 10.

[0035] The curing step S4 is a step in which the resin composition is cured by an ultraviolet irradiation device 34. The ultraviolet irradiation device 34 is located downstream of the die 33 and irradiates the resin composition with ultraviolet light. The resin composition is cured by the irradiation of ultraviolet light and forms a coating resin layer 20. This results in an optical fiber 1 comprising a glass fiber 10 and a coating resin layer 20.

[0036] Measurement step S5 is a process in which the eccentricity d (see Figure 2) of the glass fiber 10 is measured at 50 or more points over a length range of 50 m or more of the glass fiber 10 using the measurement unit 35. Measurement step S5 is performed online during line drawing. A measurement length of 1000 m or more is more preferable. A number of data points of 1000 or more is more preferable. The eccentricity d is measured, for example, with a sampling period of 20 ms or less. In this case, 50 measurements are taken per second, so if the line drawing speed is 40 m / s, the measurement interval is 1 m or less.

[0037] The measurement unit 35 is located downstream of the ultraviolet irradiation device 34. The measurement process S5 is performed after the curing process S4, but may also be performed before the curing process S4. In this case, the measurement unit 35 is located upstream of the ultraviolet irradiation device 34. In this case, the central axis RC is set with reference to the outer circumference of the resin composition before curing. Details of the measurement method by the measurement unit 35 will be described later.

[0038] The winding process S6 is a process in which the optical fiber 1 is wound onto the winding bobbin 41 via guide rollers 36, 37, capstan 38, screening device 39, and dancer roller 40. The guide rollers 36, 37, capstan 38, screening device 39, dancer roller 40, and winding bobbin 41 are arranged in this order downstream of the ultraviolet irradiation device 34.

[0039] The guide roller 36 is a roller positioned directly below the ultraviolet irradiation device 34 in the vertical direction. The guide roller 36 contacts the optical fiber 1 and changes the direction of travel of the optical fiber 1 from the vertical direction to a direction different from the vertical direction. The dancer roller 40 may be positioned between the guide roller 37 and the capstan 38.

[0040] (Measurement method) The measurement unit 35 is configured as an eccentric image recognition device and includes, for example, a first light source, a first imaging unit, a second light source, and a second imaging unit. The first light source is positioned to irradiate the entire radial direction of the optical fiber 1 to be measured. The light from the first light source includes wavelengths that pass through the coating resin layer 20. The first imaging unit is positioned opposite the first light source with the optical fiber 1 to be measured in between, and is configured to acquire an image of the light that has passed through the optical fiber 1. The second light source and the second imaging unit are configured similarly to these, except that they are positioned perpendicular to the opposing direction of the first light source and the first imaging unit.

[0041] With this configuration, the positions of the outer circumference of the coating resin layer 20 and the inner circumference of the coating resin layer 20 (the positions of the outer circumference of the glass fiber 10) can be determined based on the light transmitted through the optical fiber 1 in two mutually orthogonal directions perpendicular to the central axis of the optical fiber 1, and the eccentricity d of the glass fiber 10, which is the distance between their centers, can be measured. In other words, the eccentricity d can be measured non-destructively while maintaining the optical fiber 1.

[0042] Figures 5 and 6 are schematic diagrams showing examples of observation images observed by the imaging unit. In the figures, the left-right direction corresponds to the radial direction of the optical fiber 1, and the up-down direction corresponds to the longitudinal direction of the optical fiber 1. A portion of the light emitted from the first light source passes through the coating resin layer 20 and is totally reflected at the outer surface of the glass fiber 10. Due to this totally reflected light, a dark area (shadow) is formed in the observation image corresponding to the position of the outer circumference of the glass fiber 10 (the position of the inner circumference of the coating resin layer 20). When there is no eccentricity, as shown in Figure 5, the distance from the center C of the observation image (the center of the outer circumference of the coating resin layer 20) to the dark area is equal on both sides. When eccentricity occurs, as shown in Figure 6, the distance from the center C to the dark area is uneven on both sides. The larger the amount of eccentricity d, the greater the degree of unevenness on both sides.

[0043] The measurement unit 35 is connected to the control unit 42 in a communication manner. The measurement results obtained in the measurement process S3 are transmitted to the control unit 42. The control unit 42 performs an analysis of the measurement results. Specifically, the control unit 42 calculates the mean value a and standard deviation σ of the eccentricity d, and creates a histogram of the eccentricity d with a class width of 1 μm.

[0044] Based on the analysis results, the control unit 42 performs feedback control on, for example, the die 33, the heating furnace 31, or the guide roller 36. Specifically, the control unit 42 adjusts the position or inclination of the die 33, the position of the optical fiber base material 2, or the position of the guide roller 36 so that the mean value a and standard deviation σ of the eccentricity d satisfy a+3σ≦10μm. In other words, the coating step S3 may include a step of adjusting the position or inclination of the die 33 so that a+3σ≦10μm is satisfied. The drawing step S1 may include a step of adjusting the position of the optical fiber base material 2 so that a+3σ≦10μm is satisfied. The winding step S6 may include a step of adjusting the position of the guide roller 36 so that a+3σ≦10μm is satisfied. In the method for manufacturing the optical fiber 1, the resin composition is applied while performing such eccentricity adjustments so that the mean value a and standard deviation σ of the eccentricity d satisfy a+3σ≦10μm.

[0045] Furthermore, the control unit 42 adjusts the position or tilt of the die 33, the position of the optical fiber base material 2, or the position of the guide roller 36 so that the histogram of eccentricity d shows a single peak shape when the class width is set to 1 μm. In other words, the coating process S3 may include the step of adjusting the position or tilt of the die 33 so that the histogram of eccentricity d shows a single peak shape. The drawing process S1 may include the step of adjusting the position of the optical fiber base material 2 so that the histogram of eccentricity d shows a single peak shape. The winding process S6 may include the step of adjusting the position of the optical fiber base material 2 so that the histogram of eccentricity d shows a single peak shape. Guide roller 36 The process may include adjusting the position of the eccentricity. In the manufacturing method of the optical fiber 1, the resin composition is applied while performing such eccentricity adjustment, such that the histogram of the eccentricity amount d shows a single peak shape when the class width is 1 μm.

[0046] The control unit 42 continuously monitors the eccentricity d measured during line drawing and, if it exceeds a set threshold, issues an alarm, for example. This allows the operator to readjust the manufacturing equipment 30 or discard defective parts. The operator may also observe the measurement results of the eccentricity d, understand the state of the eccentricity d, and perform the above eccentricity adjustment to bring it into the conditions for a good product (a + 3σ ≤ 10 μm, and the histogram has a single peak).

[0047] The control unit 42 may be configured as a computer system including, for example, a processor such as a CPU (Central Processing Unit), memory such as RAM (Random Access Memory) and ROM (Read Only Memory), input / output devices such as a touch panel, mouse, keyboard, and display, and communication devices such as a network card. The control unit 42 realizes its functions by operating each piece of hardware under the control of the processor based on a computer program stored in memory.

[0048] Traditionally, in the process of selecting only optical fibers manufactured at a constant drawing speed, the cross-sectional structure of several points on optical fibers manufactured before and after the start and end of the so-called "good fiber selection" process was sometimes measured to check for eccentricity. However, since the eccentricity changes along the length of the optical fiber, there is a possibility of missing eccentricity defects that occur during the good fiber selection process. In optical fiber manufacturing, for example, optical fibers with a length of 3000km to 4000km are drawn together as one lot. For example, even a lot that passes the eccentricity inspection at both ends of the good fiber selection process may fail the eccentricity inspection after being divided into 10km to 150km lengths during the subsequent colored resin layer coating process. If a fiber fails the inspection, it is discarded until it passes, which leads to problems such as a worsening of the defective discard rate and an increase in inspection time. Currently, the above-mentioned defective discard rate is about 1%.

[0049] In the manufacturing method of the optical fiber 1 according to this embodiment, in order to suppress the gradual deterioration of the eccentricity d during drawing, the eccentricity d is measured and monitored online, and feedback control is performed based on the measurement results. As a result, the eccentricity d is suppressed along the entire length of the optical fiber 1. As a result, the rate of defective discards can be reduced.

[0050] (Example of experiment) The following describes the experimental examples. Optical fibers according to Examples 1 to 7 were manufactured by changing the manufacturing conditions (drawing conditions). The diameter of the glass fiber was 125 μm, and the diameter of the optical fiber was 200 μm. For the optical fiber in each experimental example, the eccentricity was measured offline at more than 1000 points over a distance of 1000 m.

[0051] Table 1 summarizes the specifications of the optical fibers for each experimental example. Table 1 shows the average value a, 3σ, a+3σ of the eccentricity d, the defective discard rate per lot, and the number of peaks in the histogram of eccentricity d when the class width is set to 1 μm. [Table 1]

[0052] Figure 7 is a graph showing the eccentricity waveform of the glass fiber related to Experimental Example 1. The horizontal axis of Figure 7 represents the line length. The line length corresponds to the axial position of the glass fiber. The vertical axis represents the eccentricity of the glass fiber. Figure 8 is a histogram and cumulative line graph of the eccentricity of the glass fiber related to Experimental Example 1. The horizontal axis of Figure 8 represents the class value of the eccentricity d. The left vertical axis represents the frequency. The right vertical axis represents the cumulative value. In the optical fiber related to Experimental Example 1, as shown in Figure 8, the histogram is a single peak, and as shown in Table 1, the defect rate is 0% by maintaining the a+3σ value at 10 μm or less when drawing the line.

[0053] Figure 9 is a graph showing the eccentricity waveform of the glass fiber related to Experimental Example 3. Figure 10 is a histogram and cumulative line graph of the eccentricity of the glass fiber related to Experimental Example 3. In the optical fiber related to Experimental Example 3, as shown in Figure 9, the histogram is bimodal, and as shown in Table 1, the value of a+3σ exceeds 10 μm. The defective discard rate of the optical fiber related to Experimental Example 3 exceeds 80%.

[0054] In the optical fiber according to Experimental Example 6, the lot defect rate is 1.1%. Therefore, it is very difficult to detect defects using conventional sampling inspections that only check the eccentricity at both ends of the good product. In the optical fiber according to Experimental Example 7, the lot defect rate is also low at 9.10%, with good products accounting for over 90%. Therefore, it is difficult to detect defects using sampling inspections. With the manufacturing method of the optical fiber 1 according to this embodiment, the eccentricity d of the glass fiber 10 is measured online during drawing, making it easy to detect defects. Furthermore, the eccentricity d can be adjusted based on the measurement result of the eccentricity d.

[0055] When the histogram shows two peaks, as in the optical fibers related to experimental examples 2, 3, and 5, it indicates that fluctuations (variations) in eccentricity are occurring, which tends to result in a high rate of defective discards.

[0056] For the optical fiber used in Experimental Example 8, which was manufactured under the same conditions as Experimental Example 1, the eccentricity was measured at 4000 points over a length range of 3000m or more of glass fiber. Similar to the optical fiber used in Experimental Example 1, the histogram for the optical fiber in Experimental Example 8 was a single-peak shape, confirming that the defect rate was 0%. As the length of the optical fiber increases, the effort required to dispose of defective portions becomes greater, thus demonstrating the significant benefit of reducing the defect rate.

[0057] While embodiments and modifications have been described above, this disclosure is not necessarily limited to the embodiments and modifications described herein, and various modifications are possible without departing from its essence. The above embodiments and modifications may be combined as appropriate. [Explanation of symbols]

[0058] 1… Optical fiber 2… Optical fiber base material 10…Glass fiber 12... Cores 14…Clad 20…Coating resin layer 22…Primary resin layer 24…Secondary resin layer 30...Manufacturing equipment 31...Heating furnace 31a... Core tube 31b… Heating element 32…Cooling device 33... Dice 34...UV irradiation device 35...Measuring part 36... Guide roller 37... Guide roller 38... Capstan 39…Screening device 40...Dansarola 41...winding bobbin 42... Control Unit a...Average value C…center d...Eccentricity GC…Central axis RC…Central axis

Claims

1. The process involves melting the optical fiber preform and drawing the glass fiber into a wire, A step of applying a resin composition to the outer circumference of the glass fiber, A method for manufacturing an optical fiber, comprising the step of curing the applied resin composition, The eccentricity of the central axis of the glass fiber from the central axis relative to the outer circumference of the resin composition or the outer circumference of the coated resin layer formed by curing the resin composition, in a cross section perpendicular to the central axis of the glass fiber, is measured at 50 points or more over a length range of 50 m or more of the glass fiber with a sampling period of 20 ms or less. The resin composition is applied such that the average value a and standard deviation σ of the eccentricity satisfy a + 3σ ≤ 10 μm. The resin composition is applied such that the histogram of the eccentricity shows a single peak shape when the class width is 1 μm. The resin composition is applied while adjusting at least one of the following (A) and (B): A method for manufacturing optical fibers. (A) Position or inclination of the coating apparatus for applying the resin composition (B) The position of the optical fiber base material, or the position of the roller located directly below the curing apparatus for curing the resin composition and which changes the direction of travel of the optical fiber.

2. The measurement step is performed before the curing step, and the eccentricity is measured as the eccentricity of the glass fiber from the central axis with respect to the outer circumference of the resin composition. A method for manufacturing an optical fiber according to claim 1.

3. The measurement step is performed after the curing step, and the eccentricity is measured as the eccentricity of the glass fiber from the central axis with respect to the outer circumference of the coating resin layer. A method for manufacturing an optical fiber according to claim 1.

Images