Optical fiber manufacturing method and optical fiber manufacturing apparatus

Abstract

The present invention is a method for producing an optical fiber wherein the circumference of a glass fiber is covered with an ultraviolet cured resin. This method for producing an optical fiber comprises: a step wherein the starting material of an ultraviolet cured resin is applied to the circumference of a glass fiber; a step wherein the glass fiber, to which the starting material of an ultraviolet cured resin has been applied, is passed through the inside of a cylindrical body that is capable of transmitting ultraviolet light (as exemplified by a quartz tube); a step wherein the starting material is cured by means of ultraviolet irradiation from the outside of the cylindrical body with use of a light source (as exemplified by an UV bulb), thereby forming a covering; and a step wherein the input power to the light source is controlled (as exemplified by a power control unit) so that the degree of curing of the covering is constant on the basis of the illuminance of ultraviolet of the light source and the illuminance of ultraviolet that has transmitted through the cylindrical body.

Description

[Technical field]

[0001] The present disclosure relates to a method and an apparatus for manufacturing an optical fiber. This application claims priority based on Japanese Patent Application No. 2020-030232, filed on February 26, 2020, and incorporates by reference all of the contents of said application. [Background technology]

[0002] Patent Document 1 discloses an ultraviolet irradiation device that controls the power input to a light source so that the illuminance of ultraviolet light transmitted through a quartz tube (hereinafter referred to as transmitted light through the quartz tube) is constant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2005-162524 Summary of the Invention [Means for solving the problem]

[0004] A method for producing an optical fiber according to one aspect of the present disclosure includes the steps of: A method for manufacturing an optical fiber having a glass fiber coated with an ultraviolet curing resin, the method comprising the steps of: applying an ultraviolet curing resin raw material to the glass fiber; passing the glass fiber coated with the ultraviolet curing resin raw material through an ultraviolet ray-transmitting cylindrical body; irradiating the cylindrical body with ultraviolet rays from a light source to harden the glass fiber, thereby forming a coating; and controlling the input power to the light source based on the illuminance of the ultraviolet rays from the light source and the illuminance of the ultraviolet rays transmitted through the cylindrical body so that the degree of hardening of the coating is constant. and the step of controlling the input power controls the input power based on a product of an illuminance of the ultraviolet light from the light source and an illuminance of the ultraviolet light transmitted through the cylindrical body. .

[0005] An optical fiber manufacturing apparatus according to one aspect of the present disclosure includes: An apparatus for manufacturing an optical fiber coated with an ultraviolet curing resin, comprising: a cylindrical body configured to be able to transmit ultraviolet light, through which a glass fiber coated with an ultraviolet curing resin raw material passes; an ultraviolet irradiation furnace having a light source that irradiates the ultraviolet light from outside the cylindrical body onto the ultraviolet curing resin raw material; and a power control unit that controls the input power to the light source based on the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light transmitted through the cylindrical body so that the degree of hardening of the coating formed by hardening the ultraviolet curing resin raw material is constant. The power control unit controls the input power to the light source based on the product of the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light transmitted through the cylindrical body. . Moreover, an optical fiber manufacturing apparatus according to one aspect of the present disclosure is an optical fiber manufacturing apparatus coated with an ultraviolet curing resin, comprising: a cylindrical body configured to be able to transmit ultraviolet light, through which a glass fiber coated with an ultraviolet curing resin raw material passes; an ultraviolet irradiation furnace having a light source that irradiates the ultraviolet light from outside the cylindrical body onto the ultraviolet curing resin raw material; and a power control unit that controls an input power to the light source based on the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light that has passed through the cylindrical body so that the degree of curing of the coating formed by curing the ultraviolet curing resin raw material is constant, wherein the power control unit determines the illuminance of the ultraviolet light within the cylindrical body from the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light that has passed through the cylindrical body, and controls the input power to the light source based on the determined illuminance of the ultraviolet light within the cylindrical body. . [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram of an optical fiber manufacturing apparatus according to one embodiment of the present disclosure. [Figure 2A] FIG. 2A is a diagram showing an example of a UV irradiation furnace. [Figure 2B] FIG. 2B is a diagram showing an example of a UV irradiation furnace. [Diagram 3] FIG. 3 is a diagram illustrating a control device in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [Problem that this disclosure aims to solve] The ultraviolet light from the light source penetrates the peripheral wall of the quartz tube (more specifically, the peripheral wall on the front side as viewed from the light source) to enter the inside of the quartz tube, then penetrates the peripheral wall of the quartz tube again (more specifically, the peripheral wall on the back side as viewed from the light source) to exit the quartz tube, and is detected by a sensor located outside the quartz tube as transmitted light. If the quartz tube is clouded, the transmitted light is attenuated by the cloudy part of the peripheral wall on the front side, and is then further attenuated by the cloudy part of the peripheral wall on the back side and detected by the sensor, so that the sensor detects a value that is smaller than the illuminance of the ultraviolet light inside the quartz tube by the amount that has passed through the peripheral wall on the back side. For this reason, when the input power to the light source is controlled so that the illuminance of the light transmitted through the quartz tube is constant, the illuminance of the ultraviolet light from the light source becomes greater than the illuminance required for hardening the coating inside the quartz tube in order to compensate for the attenuation caused by the light passing through the inner peripheral wall. As a result, as the quartz tube becomes cloudy, the illuminance of the ultraviolet light inside the quartz tube gradually increases, and the degree of hardening of the coating also gradually increases, so that the degree of hardening of the coating is not uniform along the length of the optical fiber. Therefore, it is desirable to make the degree of hardening of the coating uniform along the length of the optical fiber.

[0008] [Effects of this disclosure] According to the present disclosure, the degree of hardening of the coating can be made uniform along the length of the optical fiber.

[0009] [Description of the embodiments of the present disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. The method for manufacturing an optical fiber according to the present disclosure is (1) a method for manufacturing an optical fiber having an ultraviolet curing resin coated around a glass fiber, the method including the steps of: applying an ultraviolet curing resin raw material around the glass fiber; passing the glass fiber coated with the ultraviolet curing resin raw material through an ultraviolet ray-transmitting cylindrical body; irradiating the cylindrical body with ultraviolet rays from a light source to harden the glass fiber, thereby forming a coating; and controlling the input power to the light source based on the illuminance of the ultraviolet rays from the light source and the illuminance of the ultraviolet rays transmitted through the cylindrical body so that the degree of hardening of the coating is constant. and the step of controlling the input power controls the input power based on a product of an illuminance of the ultraviolet light from the light source and an illuminance of the ultraviolet light transmitted through the cylindrical body. . The illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light that has passed through the cylindrical body are obtained, and the input power to the light source is controlled so that the illuminance of the ultraviolet light inside the cylindrical body is constant. This eliminates the need to compensate for the ultraviolet light that has passed through the inner peripheral wall, as occurs when the illuminance of the ultraviolet light that has passed through the cylindrical body is kept constant. This makes it possible to make the degree of hardening of the coating uniform along the length of the optical fiber. In addition, the product of the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light that has passed through the cylindrical body corresponds to a characteristic that correlates with the degree of hardening of the coating by irradiation with ultraviolet light, so if the power input to the light source is controlled so that this product is constant, it becomes easy to uniformize the degree of hardening of the coating along the length of the optical fiber.

[0011] The optical fiber manufacturing apparatus according to the present disclosure comprises: 2) A manufacturing apparatus for an optical fiber coated with an ultraviolet curing resin, the manufacturing apparatus comprising: a cylindrical body configured to be able to transmit ultraviolet light, through which a glass fiber coated with an ultraviolet curing resin raw material passes; an ultraviolet irradiation furnace having a light source that irradiates the ultraviolet light from outside the cylindrical body onto the ultraviolet curing resin raw material; and a power control unit that controls the input power to the light source based on the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light that has passed through the cylindrical body so that the degree of hardening of the coating formed by hardening the ultraviolet curing resin raw material is constant. The power control unit controls the power input to the light source based on the product of the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light transmitted through the cylindrical body. The illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light that has passed through the cylindrical body are obtained, and the input power to the light source is controlled so that the illuminance of the ultraviolet light inside the cylindrical body is constant. This makes it possible to make the degree of hardening of the coating uniform along the length of the optical fiber. In addition, the product of the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light that has passed through the cylindrical body corresponds to a characteristic that correlates with the degree of hardening of the coating by irradiation with ultraviolet light, so if the power input to the light source is controlled so that this product is constant, it becomes easy to uniformize the degree of hardening of the coating along the length of the optical fiber.

[0012] (3) An optical fiber manufacturing apparatus according to the present disclosure is an optical fiber manufacturing apparatus coated with an ultraviolet curing resin, comprising: a cylindrical body configured to be transparent to ultraviolet rays, through which a glass fiber coated with an ultraviolet curing resin raw material passes; an ultraviolet irradiation furnace having a light source that irradiates the ultraviolet rays from outside the cylindrical body onto the ultraviolet curing resin raw material; and a power control unit that controls the input power to the light source based on the illuminance of the ultraviolet rays from the light source and the illuminance of the ultraviolet rays that have passed through the cylindrical body so that the degree of hardening of the coating formed by the hardened ultraviolet curing resin raw material is constant, wherein the power control unit determines the illuminance of the ultraviolet rays within the cylindrical body from the illuminance of the ultraviolet rays from the light source and the illuminance of the ultraviolet rays that have passed through the cylindrical body, and controls the input power to the light source based on the determined illuminance of the ultraviolet rays within the cylindrical body. The illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light that has passed through the cylindrical body are obtained, and the input power to the light source is controlled so that the illuminance of the ultraviolet light inside the cylindrical body is constant. This makes it possible to make the degree of hardening of the coating uniform along the length of the optical fiber. Also, By determining the illuminance of the ultraviolet light inside the cylinder and controlling the power input to the light source so that the illuminance of the ultraviolet light inside the cylinder is constant, it becomes easy to uniformize the degree of hardening of the coating along the length of the optical fiber. ( 4 ) One aspect of the optical fiber manufacturing apparatus of the present disclosure includes a gas blowing section that blows gas onto an ultraviolet sensor that measures the illuminance of ultraviolet light that has passed through the cylindrical body. Gas is blown onto the ultraviolet sensor from the gas blowing section, so adhesion of volatile components can be suppressed.

[0013] [Details of the embodiment of the present disclosure] Hereinafter, specific examples of the optical fiber manufacturing method and optical fiber manufacturing apparatus according to the present disclosure will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing an example of an optical fiber manufacturing apparatus 10. As shown in FIG.

[0014] As shown in FIG. 1, an optical fiber manufacturing apparatus 10 includes a drawing furnace 11 for heating and softening an optical fiber preform G at its most upstream position. The drawing furnace 11 has a cylindrical core tube 12 into whose inside an optical fiber preform G is supplied, a heating element 13 surrounding the core tube 12, and a gas supply unit 14 that supplies an inert gas into the core tube 12. The heating element 13 may be a resistance furnace or an induction furnace.

[0015] The upper part of the optical fiber preform G is held by a preform feeding unit F, and the optical fiber preform G is fed into the furnace tube 12 by the preform feeding unit F. When the lower end part of the optical fiber preform G is heated by the heating element 13 and drawn downward, a glass fiber G1, which is a component of the optical fiber strand G2, is formed. The glass fiber G1 has a core portion and a cladding portion, and is an optical waveguide with a standard outer diameter of, for example, 125 μm.

[0016] The optical fiber manufacturing apparatus 10 includes a cooling unit 15 downstream of the drawing furnace 11. A cooling gas, for example, helium gas, is supplied to the cooling unit 15, and the glass fiber G1 drawn from the optical fiber preform G is cooled by the cooling unit 15. The optical fiber manufacturing apparatus 10 includes an outer diameter measuring unit 16 downstream of the cooling unit 15. The outer diameter measuring unit 16 is configured to be able to measure the outer diameter of the glass fiber G1 using, for example, laser light, and the glass fiber G1 cooled by the cooling unit 15 has its outer diameter measured by the outer diameter measuring unit 16 and is sent downward. Note that the outer diameter measuring unit 16 may use a measurement method other than laser light as long as it can measure the outer diameter of the glass fiber G1 in a non-contact manner.

[0017] The optical fiber manufacturing apparatus 10 includes a resin applicator 17 for ultraviolet curing resin raw material, and a UV curing oven 1, downstream of the outer diameter measuring unit 16. The UV curing oven 1 corresponds to the ultraviolet irradiation oven of the present disclosure. The resin applicator 17 stores, for example, an ultraviolet curing resin raw material for protecting the glass fiber. The resin applicator 17 applies an ultraviolet curing resin raw material (e.g., urethane acrylate resin) to the glass fiber G1 whose outer diameter has been measured, and the ultraviolet curing resin raw material is irradiated with ultraviolet rays in the UV curing oven 1 and cured. This results in an optical fiber wire G2 in which a coating of ultraviolet curing resin is formed around the glass fiber G1.

[0018] The UV-curable resin for protecting the glass fiber may be composed of a primary resin and a secondary resin. In this case, a resin applicator for the primary coating and a first UV curing furnace are provided, and a resin applicator for the secondary coating and a second UV curing furnace are provided downstream of the first UV curing furnace. Alternatively, a resin applicator storing a UV-curable resin material for coloring may be provided, and the optical fiber core may be coated with the UV-curable resin for coloring on the optical fiber core G2. Therefore, in addition to the optical fiber core G2, the optical fiber core also corresponds to the optical fiber of the present disclosure.

[0019] The optical fiber manufacturing apparatus 10 includes a direct below roller 18 and a guide roller 19 downstream of the UV curing furnace 1. The direct below roller 18 is disposed directly below the drawing furnace 11, and changes the running direction of the optical fiber G2 from a vertical direction to, for example, a horizontal direction. The optical fiber G2, whose running direction has been changed by the direct below roller 18, is guided by the guide rollers, and the running direction is changed from the horizontal direction to, for example, diagonally upward.

[0020] The optical fiber manufacturing apparatus 10 further includes a take-up device 20, a guide roller 21, a dancer roller 22, and a winding device 23 downstream of the guide roller 19. The optical fiber G2 is taken up at a predetermined speed by the capstan of the take-up device 20, and wound onto a bobbin B of the winding device 23 via the dancer roller 22.

[0021] 2A and 2B are diagrams showing an example of a UV curing oven 1. FIG. The UV curing furnace 1 includes a cylindrical quartz tube 2, a UV bulb 4 disposed outside the quartz tube 2, and a reflector 3 for focusing ultraviolet light from the UV bulb 4 onto the optical fiber G2. The quartz tube 2 is translucent to ultraviolet light, and is disposed so that the central axis of the quartz tube 2 is the position through which the optical fiber G2 passes. The quartz tube 2 corresponds to the cylindrical body of the present disclosure.

[0022] The UV bulb 4 has, for example, a UV-LED (Light Emitting Diode) light source and can irradiate the optical fiber strand G2 with ultraviolet light. Note that instead of the UV-LED light source, a UV lamp that radiates ultraviolet light by discharging in mercury vapor may be used. The reflecting mirror 3 is disposed so as to surround the quartz tube 2 and the UV bulb 4, and the ultraviolet light irradiated from the UV bulb 4 is reflected by the reflecting mirror 3 and irradiated onto the quartz tube 2.

[0023] A purge gas containing an inert gas such as helium gas or nitrogen gas is supplied in a downflow manner into the quartz tube 2. In detail, the upper end side of the quartz tube 2 is connected to a gas supply path, and the purge gas whose flow rate is adjusted by a flow rate regulator 8 is supplied into the quartz tube 2 from the upper end side of the quartz tube 2. The lower end side of the quartz tube 2 is connected to a gas exhaust path, and the purge gas supplied into the quartz tube 2 and gas such as air that has entered the quartz tube 2 from the inlet 5 and outlet 6 of the UV curing furnace 1 are exhausted from the lower end side of the quartz tube 2.

[0024] If oxygen is present in the quartz tube 2, the ultraviolet curing reaction of the ultraviolet curing resin raw material is inhibited. Therefore, the flow rate of the purge gas is increased to increase the concentration of the purge gas in the quartz tube 2 and to decrease the oxygen concentration in the quartz tube 2. The oxygen concentration in the quartz tube 2 may be adjusted by adjusting the opening of the shutter 7 provided at the inlet 5 or outlet 6, or by exhausting the gas in the quartz tube 2 with the suction pump 9 provided in the exhaust path. In addition, a photocatalytic coating layer C is provided on the inner surface of the quartz tube 2. The photocatalytic coating layer C is mainly composed of titanium dioxide (TiO2) and also contains a binder component. A coating liquid containing a mixture of titanium dioxide and a binder component is applied to the inner surface of the quartz tube 2 and baked onto the inner surface of the quartz tube 2 by heating, for example.

[0025] The optical fiber G2 is introduced into the quartz tube 2 from the entrance 5 of the UV curing furnace 1. The optical fiber G2 passes through the inside of the quartz tube 2 and is sent out from the exit 6 of the UV curing furnace 1 to the outside of the quartz tube 2 and heads toward the roller 18. Ultraviolet rays from the UV bulb 4 are irradiated from outside the quartz tube 2 onto the optical fiber G2 passing through the inside of the quartz tube 2. This irradiation of ultraviolet rays progresses the hardening of the coating of the optical fiber G2. In the present disclosure, the illuminance of the ultraviolet rays transmitted through the quartz tube 2 is detected, and the control device 40 controls the input power to the light source of the UV bulb 4 based on the detection result so that the degree of hardening of the coating is constant.

[0026] As shown in FIG. 3, an ultraviolet sensor 42 is disposed on the opposite side of the quartz tube 2 to the UV bulb 4. The ultraviolet light transmitted through the quartz tube 2 exits from a hole 3a provided in the reflector 3 (or may be a gap between the mirror parts if the reflector 3 is composed of multiple mirror parts) and is detected by the ultraviolet sensor 42. This detection result is output to the control device 40. The control device 40 has, for example, one or more CPUs (Central Processing Units) and loads various programs and data stored in, for example, a ROM (Read Only Memory) into a RAM (Random Access Memory) and executes the programs loaded in the RAM. This allows the operation of the optical fiber manufacturing apparatus 10 to be controlled.

[0027] The control device 40 also includes a power control unit 41. The power control unit 41 controls the illuminance I in and the illuminance I of the ultraviolet light transmitted through the quartz tube 2. out Therefore, the illuminance I of the ultraviolet light in the quartz tube 2 is F and calculate the ultraviolet illuminance I F The power input to the light source is controlled based on the illuminance I of the ultraviolet light irradiated toward the quartz tube 2. in corresponds to the illuminance of the ultraviolet light of the light source of the present disclosure. This ultraviolet illuminance I in can be substituted by the power input to the light source, but it may also be monitored. When monitoring, the illuminance of the ultraviolet light is measured at a position on the line connecting the light source and the center of the quartz tube 2, before it passes through the quartz tube 2. It is preferable to measure the position close to the quartz tube.

[0028] An example will be described in which the ultraviolet light transmitted through the quartz tube 2 is modeled as light transmitted in a straight line along the horizontal direction (the same as the radial direction of the quartz tube 2) from the light source. In this case, it is assumed that the volatile components of the ultraviolet curing resin raw material adhere to the inner surface of the quartz tube 2 with a uniform thickness. From the Lambert-Beer law, the illuminance I of the ultraviolet light inside the quartz tube 2 is F is the illuminance I of the ultraviolet light transmitted through the quartz tube 2 in Equation 1. out are shown in Equation 2, respectively.

[0029] I F =I in e -αl-αglg ...Formula 1 I out =I F e -αl-αglg ...Formula 2 α is the absorption coefficient of the volatile component attached to the quartz tube 2 , l is the thickness of the volatile component attached to the quartz tube 2 , αg is the absorption coefficient of the quartz tube 2 , and lg is the thickness of the quartz tube 2 . From these equations 1 and 2, -αl-αglg By eliminating I F =I in (I out / I F ), we can obtain the following equation 3. I F =√(I in ×I out )...Equation 3 The illuminance I of the ultraviolet light transmitted through the quartz tube 2 out A portion of the ultraviolet light is blocked by the optical fiber G2 and measured by the ultraviolet sensor 42. However, since the outer diameter of the optical fiber G2 is small, the effect of the blocking of a portion of the ultraviolet light on the measurement value is small and can be ignored.

[0030] The power control unit 41 controls the power input to the light source of the UV bulb 4 so that the degree of hardening of the coating is constant within a predetermined range. For example, the illuminance I F If it is determined that the degree of hardening of the coating is low, the power control unit 41 outputs a signal to the UV bulb 4 to increase the input power to the light source. As a result, the illuminance I in Since the UV illuminance I F can be made larger.

[0031] In this way, the illuminance I of the ultraviolet light irradiated toward the quartz tube 2 in and the illuminance I of the ultraviolet light transmitted through the quartz tube 2 out The illuminance I of ultraviolet light in the quartz tube 2 is obtained. FThe power input to the light source is controlled so that the illuminance I of the ultraviolet light transmitted through the quartz tube 2 is constant. out Unlike the case where the thickness is constant, the amount of light that passes through the inner peripheral wall does not need to be compensated for. Therefore, the degree of hardening of the coating can be made uniform along the length of the optical fiber.

[0032] The illuminance I of the ultraviolet light transmitted through the quartz tube 2 out The detection position is preferably, for example, between the center and the bottom end of the quartz tube 2. The reason is that clouding of the quartz tube tends to worsen on the bottom end side. In the above embodiment, the illuminance I of the ultraviolet light irradiated toward the quartz tube 2 is in and the illuminance I of the ultraviolet light transmitted through the quartz tube 2. out The illuminance I F of the ultraviolet light in the quartz tube 2 is calculated from the square root of the product of I and I, but the present disclosure is not limited to this example. For example, the illuminance I of the ultraviolet light irradiated toward the quartz tube 2 is calculated from the square root of the product of I and I. in and the illuminance I of the ultraviolet light transmitted through the quartz tube 2. out The power input to the light source may be controlled based on another relational expression using

[0033] Alternatively, in the above embodiment, the illuminance I of the ultraviolet light transmitted through the quartz tube 2 out The power input to the light source is controlled so that the degree of hardening of the coating is constant by monitoring the intensity of the ultraviolet light in the quartz tube 2 (the intensity of the ultraviolet light directly hitting the coating of the optical fiber G2) I F It is also possible to monitor the curing rate and control the power input to the light source to achieve a consistent degree of cure of the coating.

[0034] The problem with determining the illuminance inside the quartz tube 2 is that the sensor itself becomes cloudy due to the volatile components, making accurate measurement difficult. Therefore, gas is sprayed onto the sensor itself to suppress adhesion of the volatile components. In order to suppress inhibition of curing of the ultraviolet curing resin raw material by oxygen, the inside of the quartz tube 2 is basically filled with an inert gas. Therefore, an inert gas is preferable as the spray gas. Also, a modified example in which an oxygen-containing gas is sprayed with the aim of oxidizing and decomposing the attached volatile components is effective. Furthermore, it is also effective to coat the sensor itself with titanium oxide, which is a photocatalyst. The gas flow rate is preferably at least 5 L / min or more, since it is necessary to blow away the volatile components.

[0035] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the above meaning, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0036] 1...UV curing furnace (ultraviolet irradiation furnace), 2...quartz tube (cylindrical body), 3...reflector, 3a...hole, 4...UV bulb (light source), 5...inlet, 6...outlet, 7...shutter, 8...flow regulator, 9...suction pump, 10...optical fiber manufacturing device, 11...drawing furnace, 12...furnace tube, 13...heating element, 14...gas supply unit, 15...cooling unit, 16...outer diameter measurement unit, 17...resin application device, 18...directly below roller, 19, 21...guide roller, 20...take-up device, 22...dancer roller, 23...winding device, 40...control device, 41...power control unit, 42...ultraviolet sensor, B...bobbin, C...photocatalytic coating layer, F...base material feed unit, G...optical fiber base material, G1...glass fiber, G2...optical fiber strand.

Claims

1. A method for manufacturing an optical fiber in which a glass fiber is coated with an ultraviolet curable resin, comprising the steps of: applying an ultraviolet curing resin material around the glass fiber; passing the glass fiber coated with the ultraviolet curable resin material through a cylindrical body capable of transmitting ultraviolet light; a step of irradiating ultraviolet light from a light source onto the outside of the cylindrical body to harden the cylindrical body and form a coating; controlling an input power to the light source based on an illuminance of the ultraviolet light from the light source and an illuminance of the ultraviolet light transmitted through the cylindrical body so that the degree of hardening of the coating is constant; Including, A method for manufacturing an optical fiber, wherein the step of controlling the input power controls the input power based on the product of the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light transmitted through the cylindrical body.

2. An apparatus for manufacturing an optical fiber coated with an ultraviolet curable resin, comprising: a cylindrical body configured to be able to transmit ultraviolet light and through which a glass fiber coated with an ultraviolet curing resin material passes; an ultraviolet irradiation furnace having a light source that irradiates the ultraviolet ray from outside the cylindrical body onto the ultraviolet curable resin raw material; a power control unit that controls the input power to the light source based on the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light transmitted through the cylindrical body so that the degree of hardening of the coating formed by hardening the ultraviolet curing resin raw material is constant; Equipped with The optical fiber manufacturing apparatus, wherein the power control unit controls the power input to the light source based on the product of the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light transmitted through the cylindrical body.

3. An apparatus for manufacturing an optical fiber coated with an ultraviolet curable resin, comprising: a cylindrical body configured to be able to transmit ultraviolet light and through which a glass fiber coated with an ultraviolet curing resin material passes; an ultraviolet irradiation furnace having a light source that irradiates the ultraviolet ray from outside the cylindrical body onto the ultraviolet curable resin raw material; a power control unit that controls the input power to the light source based on the illuminance of the ultraviolet light from the light source and the illuminance of the ultraviolet light transmitted through the cylindrical body so that the degree of hardening of the coating formed by hardening the ultraviolet curing resin raw material is constant; Equipped with An optical fiber manufacturing apparatus, wherein the power control unit calculates the illuminance of ultraviolet light within the cylindrical body from the illuminance of ultraviolet light from the light source and the illuminance of ultraviolet light that has passed through the cylindrical body, and controls the input power to the light source based on the calculated illuminance of ultraviolet light within the cylindrical body.

4. 4. The optical fiber manufacturing apparatus according to claim 2, further comprising a gas blowing section that blows gas onto an ultraviolet sensor that measures an illuminance of ultraviolet light that has passed through said cylindrical body.

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