Method for measuring optical fibers and method for manufacturing optical fibers

Abstract

This invention provides a method for measuring the length of an optical fiber with high precision. [Solution] A method for measuring an optical fiber unwound from a supply device, the method for measuring an optical fiber comprising the steps of supplying the optical fiber from the supply device to a capstan, and calculating the measured length of the optical fiber by correcting the geometrically measured running length of the optical fiber using the tension of the optical fiber supplied to the capstan and a correction parameter. The correction parameter is a parameter determined from the relationship between the tension and running speed of the optical fiber.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an optical fiber length measuring method and an optical fiber manufacturing method. BACKGROUND ART

[0002] Patent Document 1 discloses a method for measuring the winding length of a wire rod with little error when winding an elastic wire rod while applying tensile tension. Patent Document 2 discloses a winding method for winding a low-tension linear body with a constant tension. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0003] PATENT DOCUMENT 1 Japanese Unexamined Patent Application Publication No. 2002-372414 PATENT DOCUMENT 2 Japanese Unexamined Patent Application Publication No. 2001-233548 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In the optical fiber manufacturing process, after a long optical fiber is wound around a large-diameter bobbin, the optical fiber is unwound from the large-diameter bobbin, rewound onto a small-diameter bobbin, and then cut, whereby an optical fiber having a predetermined length may be obtained. Conventionally, the length of an optical fiber has been measured based on the amount of rotation of a capstan on which the optical fiber travels. However, since optical fibers expand and contract according to tension, when the same optical fiber is measured under two different tensions, a difference occurs between the measured lengths. The wire rod measurement method described in Patent Document 1 corrects the length using an empirically obtained linear approximation formula, and does not always allow the length to be calculated with sufficiently high accuracy.

[0005] An object of the present disclosure is to provide a method for measuring the length of an optical fiber with high accuracy. MEANS FOR SOLVING THE PROBLEMS

[0006] A method for measuring an optical fiber according to one embodiment of the present disclosure is a method for measuring an optical fiber unwound from a supply device, the method for measuring an optical fiber comprising the steps of: supplying the optical fiber from the supply device to a capstan; and calculating the measured length of the optical fiber by correcting the geometrically measured running length of the optical fiber using the tension of the optical fiber supplied to the capstan and a correction parameter, wherein the correction parameter is a parameter determined from the relationship between the tension and running speed of the optical fiber. [Effects of the Invention]

[0007] According to this disclosure, the length of an optical fiber can be measured with high precision. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing an example of the configuration of an optical fiber. [Figure 2] Figure 2 is a schematic diagram of a device for winding optical fibers onto bobbins. [Figure 3] Figure 3 is a diagram illustrating the method for calculating the spring constant. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] First, embodiments of this disclosure will be listed and described. One embodiment of the optical fiber measuring method of this disclosure is: (1) A method for measuring an optical fiber unwound from a supply device, the method for measuring an optical fiber comprising the steps of supplying the optical fiber from the supply device to a capstan, and calculating the measured length of the optical fiber by correcting the geometrically measured running length of the optical fiber using the tension of the optical fiber supplied to the capstan and a correction parameter, wherein the correction parameter is a parameter determined from the relationship between the tension and running speed of the optical fiber.

[0010] Since optical fibers expand and contract in response to tension, accurate measurement of the optical fiber length requires correction to account for tension with each measurement. According to this embodiment, the optical fiber's travel length is corrected using the tension and correction parameters applied when the optical fiber is supplied from the supply device, thereby enabling accurate measurement of the optical fiber length.

[0011] (2) In the optical fiber measurement method described in (1) above, the correction parameter is the spring constant of the optical fiber, and the spring constant may be calculated by formula (1).

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[0012] (3) In the optical fiber measurement method described in (1) or (2) above, the length L(T0) calculated by formula (2) may be used as the measured length of the optical fiber.

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[0013] (4) A method for manufacturing an optical fiber according to one embodiment of the present disclosure obtains an optical fiber having a desired length by cutting the optical fiber based on the measured length of the optical fiber calculated by the optical fiber length measuring method according to any one of the above (1) to (3). Conventionally, an extra length was provided in consideration of the error in the length of the optical fiber, and the portion longer than the desired length was discarded. Since the length of the optical fiber can be accurately calculated by the length measuring method of the present embodiment, it is not necessary to provide a long extra length, and the yield is improved.

[0014] [Details of Embodiments of the Present Disclosure] Specific examples of the optical fiber length measuring method and the optical fiber manufacturing method of the present disclosure will be described below with reference to the drawings. The present invention is not limited to these exemplifications, is indicated by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

[0015] First, an optical fiber that is a target to which the length measuring method and the manufacturing method of the present disclosure are applied will be described. Figure 1 is a cross-sectional view showing an example of the configuration of the optical fiber. As shown in Figure 1, the optical fiber 1 includes a glass fiber 11 and a coating resin layer 12 covering the glass fiber 11. The glass fiber 11 has a concentric cross-sectional structure including a core 11a having a high refractive index, and a clad 11b that covers the core 11a and has a lower refractive index than the core 11a. The glass fiber 11 contains, for example, silica glass. The coating resin layer 12 is, for example, a cured product of an ultraviolet curable resin, and is formed by applying the ultraviolet curable resin around the glass fiber 11 and then irradiating ultraviolet rays to cure the resin. The coating resin layer 12 may include a plurality of resin layers, and may include a colored layer.

[0016] The diameter of the glass fiber 11 is, for example, about 125 μm. The thickness of the coating resin layer 12 is, for example, 70 μm or less. The outer diameter of the optical fiber 1 is, for example, 180 μm or more and 265 μm or less.

[0017] The manufacturing process for the optical fiber 1 includes drawing a glass fiber 11 and forming a coating resin layer 12 around the drawn glass fiber 11. The manufacturing process for the optical fiber 1 may further include winding the optical fiber 1 onto a bobbin, screening the optical fiber 1 by applying a predetermined tension to remove low-strength portions, and transferring the optical fiber 1 wound on one bobbin to another bobbin. The linear velocity of the optical fiber 1 in each step may be, for example, 1000 m / min or more. In each step, it may be necessary to measure the optical fiber 1 as it travels at high speed.

[0018] Next, a method for measuring an optical fiber according to the present disclosure will be described. The method for measuring an optical fiber 1 includes the steps of supplying the optical fiber 1 from a supply device to a capstan, and calculating the measured length of the optical fiber 1 by correcting the travel length of the optical fiber 1, which is measured using the amount of rotation of the capstan, using the tension of the optical fiber 1 supplied to the capstan and a correction parameter.

[0019] Figure 2 is an example of an apparatus for carrying out the optical fiber measuring method of this disclosure, and is a schematic diagram of an apparatus 100 for rewinding an optical fiber onto a bobbin. As shown in Figure 2, the apparatus 100 comprises a supply device 2 and a bobbin 3, and the optical fiber 1 unwound from the supply device 2 is rewinded onto the bobbin 3.

[0020] The supply device 2 is, for example, a supply bobbin that unwinds the optical fiber 1. The optical fiber 1 unwinded from the supply device 2 is supplied to the capstan 5 via a guide roller 4a and a supply dancer roller 4b. The supply dancer roller 4b is movable up and down and maintains constant tension on the optical fiber 1 by rising or falling according to the travel speed. The supply speed of the optical fiber 1 from the supply device 2 may be adjusted according to the position of the supply dancer roller 4b. The optical fiber 1 unwinded from the capstan 5 is wound onto the bobbin 3 via a tension-adjusting winding dancer roller 4c and a guide roller 4d. The winding speed of the bobbin 3 may be adjusted according to the position of the winding dancer roller 4c.

[0021] In the device 100, the tension of the optical fiber 1 and the amount of rotation of the capstan 5 are measured while it is in motion. Specifically, the device 100 includes a tension measuring device 6 that measures the tension of the optical fiber 1 supplied from the supply dancer roller 4b to the capstan 5, and a rotation amount measuring device 7 that measures the amount of rotation of the capstan 5. The tension measuring device 6 and the rotation amount measuring device 7 are connected to a control device (not shown), for example, and the measurement results from each device are recorded in the control device.

[0022] Assuming that the optical fiber 1 does not slip in the capstan 5, the length of the optical fiber 1 that has traveled through the capstan 5 can be geometrically measured based on the amount of rotation of the capstan 5 measured by the rotation amount measuring device 7 and the circumference of the capstan 5. In the following explanation, the length of the optical fiber 1 that has traveled through the capstan 5, measured geometrically using the amount of rotation of the capstan 5 and the circumference of the capstan 5, will be referred to as the travel length. Accurately measuring the length of the optical fiber 1 that has traveled through the capstan 5 is important for quality assurance and product management purposes, such as standardizing the length of the optical fiber 1 that is rewound onto the bobbin 3, or identifying the location where an abnormality has been found.

[0023] Incidentally, tension is applied to the optical fiber 1 while it is moving, and the optical fiber 1 expands and contracts according to the magnitude of the tension. Therefore, even if the optical fiber 1 is cut based on the travel length and optical fibers of the same travel length are obtained, if the tension at the time of measurement was different, there will be a difference in the length of the optical fiber when the tension is adjusted to the same value. To avoid such a situation, it is necessary to convert the geometrically measured travel length of the optical fiber 1 to the length of the optical fiber at a predetermined reference tension. In the following explanation, the length of the optical fiber 1 at the reference tension, after the effect of expansion and contraction due to tension has been eliminated, will be called the measured length and will be distinguished from the travel length.

[0024] The inventors have found that by correcting the length of the optical fiber 1 using the tension of the optical fiber 1 and correction parameters, the length of the optical fiber 1 at different tensions can be accurately converted. That is, an optical fiber measuring method according to one embodiment of the present disclosure is a measuring method for an optical fiber 1 unwound from a supply device 2, wherein the optical fiber 1 is supplied from the supply device 2 to a capstan 5, and the length of the optical fiber 1 is calculated by correcting the travel length of the optical fiber 1, measured using the amount of rotation of the capstan 5, using the tension of the optical fiber 1 supplied to the capstan 5 and correction parameters. According to the measuring method according to this embodiment, the travel length measured at any tension can be converted with high accuracy to the length of the optical fiber 1 at a reference tension (measured length).

[0025] Here, we will explain the details of the correction parameters in this disclosure. The correction parameters are material-specific parameters that represent the relationship between the tension applied to the optical fiber and the degree of expansion and contraction. Based on the law of conservation of mass, the expansion and contraction of a moving optical fiber can be expressed as the difference in travel speed between two points, so the correction parameters in this disclosure are specifically determined from the relationship between the tension and travel speed of optical fiber 1.

[0026] In one embodiment of this disclosure, the correction parameter is the spring constant. Figure 3 is a diagram illustrating the method for calculating the spring constant. As shown in Figure 3, in calculating the spring constant, the optical fiber 1 is supplied from the supply bobbin 21 and wound onto the winding bobbin 25 via the supply dancer roller 22, test capstan 23, and winding dancer roller 24. The section from the supply bobbin 21 to the test capstan 23 is defined as the input section A1, and the section from the test capstan 23 to the winding bobbin 25 is defined as the output section A2. The tension and running speed of the optical fiber 1 are measured in each section. From the obtained tension and running speed of the optical fiber 1 in each section, the spring constant of the optical fiber 1 can be calculated. Specifically, the spring constant is calculated by the following equation (1).

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[0027] The spring constant k calculated by the method described above is a parameter that represents how much the optical fiber 1 expands and contracts when tension is applied to it. Using the tension of the optical fiber supplied to the capstan 5 and the spring constant k, the running length of the optical fiber 1 can be corrected to the length of the optical fiber 1 at a reference tension (measured length). More specifically, in this embodiment, the length L(T0) calculated by equation (2) can be used as the length of the optical fiber.

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[0028] The method of this embodiment allows for accurate measurement of the length, which facilitates quality assurance and product management of the optical fiber 1.

[0029] This disclosure also relates to a method for manufacturing optical fibers using the optical fiber measurement method described above. Specifically, in a method for manufacturing optical fibers according to one embodiment of this disclosure, an optical fiber having a desired length is obtained by cutting the optical fiber 1 based on the measured length of the optical fiber 1 calculated by the optical fiber measurement method according to one embodiment of this disclosure. Conventionally, an excess length was provided to account for errors in the length of the optical fiber, and the portion longer than the desired length was discarded. Since the correct length of the optical fiber can be calculated by the measurement method of this embodiment, it is no longer necessary to provide an excess length, and the yield is improved. The method for manufacturing optical fibers according to this embodiment can be applied, for example, to the control of the winding length onto the bobbin in the optical fiber drawing process, and to the control of the winding length in the coloring process and the rewinding process.

[0030] The optical fiber measurement method and optical fiber manufacturing method of this disclosure have been described above with reference to specific embodiments, but this disclosure is not limited to these examples.

[0031] In the embodiments described above, the apparatus 100 shown in Figure 2 and the apparatus for calculating the spring constant shown in Figure 3 were described separately, but the spring constant may also be calculated using the apparatus 100 shown in Figure 2. Specifically, the travel speed of the optical fiber 1 supplied from the supply dancer roller 4b to the capstan 5 is calculated based on the amount of rotation of the capstan 5 in Figure 2, and the tension and travel speed of the optical fiber 1 immediately after the capstan 5 (between the capstan 5 and the winding dancer roller 4c) are measured using an appropriate measuring device. The spring constant k can be calculated by substituting the measured tension and travel speed into equation (1). The spring constant k may be calculated in real time with such a configuration.

[0032] Although the above embodiments illustrate the case of rewinding an optical fiber onto a bobbin, the optical fiber measuring method and optical fiber manufacturing method of this disclosure are not limited to rewinding and can be applied to any process for running an optical fiber. The optical fiber measuring method and optical fiber manufacturing method of this disclosure can also be applied to, for example, a line drawing process, a coloring process, or a screening process. [Explanation of Symbols]

[0033] 1 Optical fiber 11. Glass fiber 11a core 11b Clad 12. Coating resin layer 100 devices 2 Feeding device 3 bobbins 4a, 4d Guide rollers 4b Supply Dancerola 4c winding dancer roller 5 Capstan 6. Tension measuring device 7. Rotational speed measuring device 21 Supply Bobbins 22 Supply Dancer Laura 23 Test Capstan 24 Retractable Dancer Roller 25 reel bobbins A1 Input section A2 Output Section

Claims

1. A method for measuring optical fibers unfurled from a supply device, The method for measuring the optical fiber is as follows: A step of supplying the optical fiber from the supply device to the capstan, The process includes a step of calculating the measured length of the optical fiber by correcting the geometrically measured length of the optical fiber using the tension of the optical fiber supplied to the capstan and correction parameters, A method for measuring optical fibers, wherein the correction parameter is determined from the relationship between the tension and travel speed of the optical fiber.

2. The correction parameter is the spring constant of the optical fiber, The spring constant is calculated by formula (1), the optical fiber measuring method according to claim 1: [Math 1] In equation (1), k is the spring constant, and T １ is the tension of the optical fiber in the input section that is input to the test capstan, and T ２ v is the tension of the optical fiber in the output section output from the test capstan, １ v is the travel speed of the optical fiber in the input section, ２ is the travel speed of the optical fiber in the output section.

3. The length L(T) calculated by equation (2) ０ The method for measuring an optical fiber according to claim 2, wherein the length of the optical fiber is defined as: [Math 2] In formula (2), T Ｓ is the tension of the optical fiber supplied to the capstan, and L(T Ｓ ) is the geometrically measured travel length of the optical fiber, T ０ is the reference tension, and L(T ０ ) is the measured length of the optical fiber when the tension of the optical fiber is converted to the reference tension T ０ .

4. A method for manufacturing an optical fiber, comprising cutting the optical fiber based on the measured length of the optical fiber calculated by the optical fiber measuring method described in any one of claims 1 to 3, thereby obtaining an optical fiber having a desired length.

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