Method for manufacturing optical fiber

Abstract

This method for manufacturing an optical fiber comprises: an application step for applying a UV-curable resin to a glass fiber; and a curing step for curing the UV-curable resin by irradiating the UV-curable resin with ultraviolet light, wherein the irradiation with ultraviolet light in the curing step is performed using a first light source and a second light source, the first light source and the second light source are each a UV LED, and the first light source and the second light source have different peak wavelengths.

Description

Optical fiber manufacturing method

[0001] This disclosure relates to a method for manufacturing optical fibers. This application claims priority under Japanese application No. 2024-228580, filed on 25 December 2024, and incorporates all the provisions contained herein.

[0002] In the manufacturing process of optical fibers, a coating layer is formed by coating a drawn glass fiber with an ultraviolet-curing resin and curing the resin by irradiating it with ultraviolet light. Conventionally, ultraviolet lamps have been used as the ultraviolet light source, but in recent years, the use of LEDs has been considered (for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 2018-177630

[0004] The present disclosure is a method for manufacturing an optical fiber, comprising a coating step of applying an ultraviolet-curable resin to a glass fiber, and a curing step of curing the ultraviolet-curable resin by irradiating it with ultraviolet light, wherein the irradiation of ultraviolet light in the curing step is performed using a first light source and a second light source, both of which are ultraviolet LEDs, and the peak wavelength of the first light source and the peak wavelength of the second light source are different.

[0005] Figure 1 is a cross-sectional view showing an example of the configuration of an optical fiber. Figure 2 is a schematic diagram showing an example of an apparatus for carrying out a method for manufacturing an optical fiber according to one embodiment of the present disclosure.

[0006] [Problems this disclosure aims to solve] When an LED is used as a UV light source to cure UV-curable resin, the curing of the coating resin may be insufficient compared to when a UV lamp is used. This disclosure aims to ensure sufficient curing of the resin when an LED is used as a UV light source to cure UV-curable resin during the manufacturing of optical fibers.

[0007] [Effects of this disclosure] According to this disclosure, when an LED is used as an ultraviolet light source to cure an ultraviolet curing resin during the manufacturing of an optical fiber, the curing of the resin can be sufficiently advanced.

[0008] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) A method for manufacturing an optical fiber according to one embodiment of the present disclosure is a method for manufacturing an optical fiber comprising a coating step of coating a glass fiber with an ultraviolet curing resin and a curing step of curing the ultraviolet curing resin by irradiating it with ultraviolet light, wherein the irradiation of ultraviolet light in the curing step is performed using a first light source and a second light source, both of which are ultraviolet LEDs, and the peak wavelength of the first light source and the peak wavelength of the second light source are different.

[0009] According to this embodiment, UV-curable resins can be sufficiently cured by using LEDs with different peak wavelengths. In particular, when a coating has a laminated structure such as a primary layer and a secondary layer, different photopolymerization initiators may be used in each layer. Conventional UV lamps have a wide wavelength range of emitted light, so it was possible to sufficiently cure resin layers containing different photopolymerization initiators simultaneously with one type of UV lamp. However, because UV LEDs have a narrow wavelength range of light, when attempting to cure resins containing different photopolymerization initiators with one type of UV LED, the polymerization reaction by the photopolymerization initiators having an absorption wavelength different from the LED's emission wavelength may not proceed sufficiently, resulting in insufficient curing. According to this embodiment, even when two or more photopolymerization initiators are used, the polymerization reaction of each resin can be promoted by two types of UV LEDs with different peak wavelengths, and the resin can be sufficiently cured.

[0010] (2) In (1) above, the peak wavelength of the second light source may be shorter than the peak wavelength of the first light source, and in the curing step, irradiation with ultraviolet light from the second light source may be performed after irradiation with ultraviolet light from the first light source. By irradiating with ultraviolet light in the order of long wavelength followed by short wavelength, the curing reaction can be carried out more reliably.

[0011] (3) In (1) or (2) above, the peak wavelength of the first light source may be 320 nm or more and 400 nm or less, and the peak wavelength of the second light source may be 100 nm or more and less than 320 nm. By using light sources in such wavelength ranges and combining relatively long-wavelength ultraviolet light with relatively short-wavelength ultraviolet light, the curing reaction can be made to proceed more reliably.

[0012] (4) In any of (1) to (3) above, the oxygen concentration near the glass fiber during ultraviolet irradiation may be 1000 ppm or less in the first light source and the second light source. By reducing the oxygen concentration, the effects of oxygen inhibition can be reduced.

[0013] (5) In any of (1) to (4) above, the coating eccentricity of the manufactured optical fiber may be 15 μm or less. When the coating eccentricity is within the above range, the coating resin film is uniformly formed around the glass fiber, so it can be cured more uniformly.

[0014] (6) In any of (1) to (5) above, the fiber vibration amplitude during ultraviolet irradiation may be 3 mm or less and the maximum peak of the vibration frequency may be 200 Hz or less in the first light source and the second light source. Reducing the fiber vibration amplitude and vibration frequency during ultraviolet irradiation makes it easier to sufficiently cure the ultraviolet curing resin.

[0015] (7) In any of (1) to (6) above, the maximum molar extinction coefficient of at least one molecule among the molecules constituting the photopolymerization initiator contained in the ultraviolet curing resin in methanol at a wavelength of 220 nm to 320 nm is 500 L·mol －１ ・cm －１ The above is also acceptable. To efficiently cure the resin, it is best to match the absorption wavelength of the photopolymerization initiator to the wavelength range of the ultraviolet LED used, and the molar extinction coefficient at that wavelength should be 500 L·mol. －１ ・cm －１ The above is desirable. A large molar extinction coefficient allows the curing reaction to proceed more efficiently.

[0016] [Details of Embodiments of the Present Disclosure] A specific example of the method for manufacturing an optical fiber according to the present disclosure will be described below with reference to the drawings. It should be understood that at least one configuration or feature described in each embodiment can be combined with other embodiments or variously modified. The present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0017] (Optical Fiber) First, an example of an optical fiber manufactured by the method for manufacturing an optical fiber according to the present embodiment will be described. FIG. 1 is a cross-sectional view showing the configuration of an optical fiber 1A, which represents a cross-section perpendicular to the central axis (optical axis) of the optical fiber 1A. As shown in FIG. 1, the optical fiber 1A includes a glass fiber 10 as an optical transmission body and a coating resin film 20. The glass fiber 10 includes a core 12 and a cladding 14 that covers the core 12. The coating resin film 20 is a film that is cured by ultraviolet rays and covers the cladding 14. The coating resin film 20 includes a plurality of layers. The coating resin film 20 includes, for example, a primary resin layer 22, a secondary resin layer 24, and a colored resin layer 26. At least the primary resin layer 22 and the secondary resin layer 24 among the plurality of layers of the coating resin film 20 are formed by curing an ultraviolet curable resin containing a photoinitiator.

[0018] The glass fiber 10 is a glass member, for example, formed of silica (SiO ２ ) glass. The glass fiber 10 transmits the light introduced into the optical fiber 1A. The core 12 is provided, for example, in a region including the central axis of the glass fiber 10. The core 12 is pure SiO ２ glass, or may be SiO ２ glass containing GeO ２ and / or fluorine element, etc. The cladding 14 is provided in a region surrounding the core 12. The cladding 14 has a refractive index lower than that of the core 12. The cladding 14 may be formed of pure SiO ２ glass, or may be formed of SiO ２ glass with fluorine element added.

[0019] 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 colored resin layer 26 is in contact with the outer circumferential surface of the secondary resin layer 24 and covers the entire secondary resin layer 24. For example, the thickness of the primary resin layer 22 may be 20 μm or more and 50 μm or less, the thickness of the secondary resin layer 24 may be 10 μm or more and the thickness of the colored resin layer 26 may be 3 μm or more and 10 μm or less. The secondary resin layer 24 may be colored and the colored resin layer 26 may be omitted. The Young's modulus of the primary resin layer 22 may be 0.5 MPa or less, or 0.3 MPa or less.

[0020] The primary resin layer 22 and the secondary resin layer 24 are formed, for example, by curing an ultraviolet-curable resin containing an oligomer, a monomer, and a photopolymerization initiator (reaction initiator).

[0021] As oligomers, urethane acrylates, epoxy acrylates, or mixtures thereof can be used. As urethane acrylates, those obtained by reacting polyol compounds, polyisocyanate compounds, and hydroxyl group-containing acrylate compounds can be used.

[0022] Possible polyol compounds include polytetramethylene glycol, polypropylene glycol, and bisphenol A / ethylene oxide addition diol. Possible polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and isophorone diisocyanate. Possible hydroxyl group-containing acrylate compounds include 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate, 1,6-hexanediol monoacrylate, pentaerythritol triacrylate, 2-hydroxypropyl acrylate, and tripropylene glycol diacrylate.

[0023] As monomers, cyclic N-vinyl monomers can be used, such as N-vinylpyrrolidone, N-vinylcaprolactam, and acryloylmorpholine. These monomers are preferred because they improve the curing speed. Other monomers include monofunctional monomers such as isobornyl acrylate, tricyclodecanyl acrylate, benzyl acrylate, dicyclopentanyl acrylate, 2-hydroxyethyl acrylate, nonylphenyl acrylate, phenoxyethyl acrylate, and polypropylene glycol monoacrylate; or polyfunctional monomers such as polyethylene glycol diacrylate, tricyclodecanediyldimethylene diacrylate, or bisphenol A / ethylene oxide diol diacrylate. Note that the acrylate compounds mentioned above may also be their corresponding methacrylate compounds.

[0024] Examples of photopolymerization initiators include acylphosphine oxide initiators and acetophenone initiators. Examples of acylphosphine oxide initiators include acylphosphine oxide compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide (registered trademark name: Lucilin TPO, manufactured by BASF), 2,4,4-trimethylpentylphosphine oxide, and 2,4,4-trimethylbenzoyldiphenylphosphine oxide. These acylphosphine oxide initiators have a broad absorption wavelength range and excellent deep curing properties, so they can be used in the primary resin layer 22 and the secondary resin layer 24.

[0025] Examples of acetophenone initiators include 1-hydroxycyclohexane-1-ylphenylketone (registered trademark: Irgacure 184, manufactured by BASF), 2-hydroxy-2-methyl-1-phenylpropan-1-one (registered trademark: Darocure 1173, manufactured by BASF), 2,2-dimethoxy-1,2-diphenylethane-1-one (registered trademark: Irgacure 651, manufactured by BASF), and 2-methyl-1-(4-methylthiophenyl)-2-morpholino Examples of acetophenone compounds include propan-1-one (registered trademark: Irgacure 907, manufactured by BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 (registered trademark: Irgacure 369, manufactured by BASF), 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, and 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one. Since these acetophenone initiators are less susceptible to oxygen inhibition, they can be used, for example, in combination with acylphosphine oxide initiators such as Lucilin TPO, which exhibits excellent deep curing properties, in a secondary resin layer 24.

[0026] (Method for Manufacturing Optical Fibers) Figure 2 is a schematic diagram showing an example of a manufacturing apparatus for carrying out a method for manufacturing optical fibers according to one embodiment of the present disclosure. The method for manufacturing optical fibers according to this embodiment will be described below with reference to Figure 2.

[0027] The heating furnace 100 is a device for heating the optical fiber preform 1. The heating furnace 100 comprises a furnace core tube 101 and a heater 102. Glass fibers 10 are obtained by drawing the optical fiber preform 1 heated by the heating furnace 100. The glass fibers 10 obtained by heating and drawing the optical fiber preform 1 advance in the direction of the arrows in Figure 2 and are sequentially fed into each process described later.

[0028] The drawn glass fiber 10 is first cooled in a cooling device 30. The cooled glass fiber 10 is then sent to a coating device 40, where an ultraviolet-curable resin is applied to the surface of the glass fiber 10 (coating step). More specifically, a first ultraviolet-curable resin is applied to the surface of the glass fiber 10 to form a first layer containing the first ultraviolet-curable resin on the surface of the glass fiber 10, and a second ultraviolet-curable resin is applied to the surface of the first layer to form a second layer containing the second ultraviolet-curable resin on the surface of the first layer. The first layer corresponds to the primary resin layer 22 after curing, and the second layer corresponds to the secondary resin layer 24 after curing. The first ultraviolet-curable resin and the second ultraviolet-curable resin may each contain an oligomer, a monomer, and a photopolymerization initiator. The first ultraviolet-curable resin may contain, for example, an acylphosphine oxide-based initiator as a photopolymerization initiator. The second ultraviolet-curable resin may contain, for example, an acylphosphine oxide-based initiator and an acetophenone-based initiator as photopolymerization initiators. A glass fiber 10 coated with an ultraviolet-curing resin becomes an optical fiber 1A.

[0029] Next, the glass fiber 10 is irradiated with ultraviolet light to cure the ultraviolet-curable resin applied to its surface (curing step). In the configuration shown in Figure 2, the curing step is carried out by the first ultraviolet irradiation furnace 51, the second ultraviolet irradiation furnace 52, the third ultraviolet irradiation furnace 53, and the fourth ultraviolet irradiation furnace 54. In the configuration shown in Figure 2, the first ultraviolet irradiation furnace 51, the second ultraviolet irradiation furnace 52, the third ultraviolet irradiation furnace 53, and the fourth ultraviolet irradiation furnace 54 are all equipped with ultraviolet LEDs as light sources. In the curing step, the glass fiber 10 is passed sequentially through each ultraviolet irradiation furnace, thereby forming a primary resin layer 22 and a secondary resin layer 24 on the surface of the glass fiber 10.

[0030] In this embodiment, the irradiation of ultraviolet light in the curing process is carried out using two types of ultraviolet LEDs having different peak wavelengths. Specifically, the first ultraviolet irradiation furnace 51, the second ultraviolet irradiation furnace 52, and the third ultraviolet irradiation furnace 53 are equipped with a first light source, and the fourth ultraviolet irradiation furnace 54 is equipped with a second light source. The first light source is an ultraviolet LED having a peak wavelength in the range of 320 nm to 400 nm, and specific examples of peak wavelengths include 365 nm, 385 nm, or 395 nm. The second light source is an ultraviolet LED having a peak wavelength in the range of 100 nm to less than 320 nm, and specific examples of peak wavelengths include 280 nm or 275 nm. The first light source may have a peak wavelength in the range of 360 nm to 400 nm, in the range of 370 nm to 400 nm, or in the range greater than 370 nm and less than or equal to 400 nm. Furthermore, the second light source may have a peak wavelength in the range of 100 nm to less than 300 nm, or in the range of 150 nm to less than 300 nm. Also, the difference between the peak wavelength of the first light source and the peak wavelength of the second light source may be 10 nm to 300 nm, 20 nm to 250 nm, 50 nm to 200 nm, or 80 nm to 150 nm.

[0031] A primary resin layer 22 and a secondary resin layer 24 are formed on the surface of the glass fiber 10, and then a colored resin layer 26 is formed to create a coating resin film 20. Subsequently, the optical fiber 1A is taken up by a take-up machine 70 via guide rollers 61 and 62, and then wound up by a winding machine 80 via guide rollers 63 and 64. In Figure 2, the take-up machine 70 includes a combination of rollers and a belt.

[0032] Incidentally, in conventional optical fiber manufacturing, ultraviolet lamps have been used to cure ultraviolet-curable resins. The ultraviolet light emitted from ultraviolet lamps includes light in a wide wavelength range from the near-ultraviolet to the deep ultraviolet region. Therefore, when using an ultraviolet lamp, the curing of the ultraviolet-curable resin proceeds sufficiently regardless of which wavelength of light, from the near-ultraviolet to the deep ultraviolet, is absorbed by the photopolymerization initiator. Furthermore, when using an ultraviolet lamp, even if multiple types of photopolymerization initiators with different absorption wavelengths are used simultaneously, the reactions of each photopolymerization initiator proceed, and the ultraviolet-curable resin can be sufficiently cured.

[0033] On the other hand, in recent years, the use of ultraviolet LEDs instead of ultraviolet lamps in the manufacture of optical fibers has been considered. However, the ultraviolet light emitted by ultraviolet LEDs typically has a specific wavelength, and its wavelength range is narrower than that of ultraviolet lamps. Therefore, when using ultraviolet LEDs instead of ultraviolet lamps, the emission wavelength of the ultraviolet LED and the absorption wavelength of the photopolymerization initiator may not match, and the curing of the ultraviolet-curable resin may not proceed sufficiently. Furthermore, when using multiple types of photopolymerization initiators with different absorption wavelengths simultaneously, even if the emission wavelength of the ultraviolet LED matches the absorption wavelength of one type of photopolymerization initiator, it may not match the absorption wavelength of the other photopolymerization initiators, and in that case, the curing reaction may not proceed sufficiently.

[0034] In the optical fiber manufacturing method according to this embodiment, ultraviolet irradiation in the curing process is performed using a first light source and a second light source. Both the first and second light sources are ultraviolet LEDs, and the peak wavelengths of the first and second light sources are different. In other words, in the optical fiber manufacturing method according to this embodiment, the ultraviolet curing resin is cured using two types of ultraviolet LEDs with different emission wavelengths. With this configuration, even when ultraviolet LEDs are used instead of ultraviolet lamps as light sources, the curing of the ultraviolet curing resin can be sufficiently advanced.

[0035] In this embodiment, the peak wavelength of the second light source may be shorter than the peak wavelength of the first light source, and after irradiation with ultraviolet rays from the first light source, the ultraviolet curable resin may be cured by irradiating with ultraviolet rays from the second light source. By irradiating ultraviolet rays in the order of long wavelength and short wavelength, the curing reaction can proceed more appropriately.

[0036] In this embodiment, the peak wavelength of the first light source may be 320 nm or more and 400 nm or less, and the peak wavelength of the second light source may be 100 nm or more and less than 320 nm. By combining and using ultraviolet rays with a relatively long wavelength and ultraviolet rays with a relatively short wavelength, the curing reaction can proceed more reliably. Further, in this aspect, a first photoinitiator that absorbs ultraviolet rays emitted from the first light source and a second photoinitiator that absorbs ultraviolet rays emitted from the second light source may be combined and used. More specifically, the first ultraviolet curable resin forming the primary resin layer 22 may contain at least the first photoinitiator, and the second ultraviolet curable resin forming the secondary resin layer 24 may contain at least the second photoinitiator. According to the above aspect, even when an ultraviolet LED is used, the curing of the resin can proceed sufficiently.

[0037] In this embodiment, the oxygen concentration near the glass fiber during ultraviolet irradiation with the first light source and the second light source may be 1000 ppm or less. By reducing the oxygen concentration, the influence of oxygen inhibition can be reduced. The oxygen concentration near the glass fiber during ultraviolet irradiation can be adjusted, for example, by blowing nitrogen into the ultraviolet irradiation furnace. More specifically, for example, the oxygen concentration can be adjusted to 1000 ppm or less by flowing nitrogen gas at 10 L / min or more from top to bottom in the ultraviolet irradiation furnace. The oxygen concentration near the glass fiber during ultraviolet irradiation with the first light source and the second light source may be 300 ppm or less.

[0038] In this embodiment, the coating eccentricity of the manufactured optical fiber may be 15 μm or less. The coating eccentricity is the distance between the center of the glass fiber 10 and the center of the coating resin film 20 in a cross-sectional view of the optical fiber 1A. A small coating eccentricity means that the coating resin film 20 is uniformly formed around the glass fiber 10. Since the coating resin film 20 is uniformly formed, the ultraviolet curable resin can be uniformly cured in the manufacturing process of the optical fiber.

[0039] In this embodiment, the fiber vibration amplitude during ultraviolet irradiation by the first light source and the second light source may be 3 mm or less, and the maximum peak of the vibration frequency may be 200 Hz or less. If the optical fiber running in the curing process vibrates, there is a risk that the optical fiber will deviate from the predetermined ultraviolet irradiation position and the curing will be insufficient. By reducing the fiber vibration amplitude and vibration frequency during ultraviolet irradiation, it is easier to sufficiently cure the ultraviolet curable resin. The fiber vibration amplitude and vibration frequency can be adjusted, for example, by arranging a fluid bearing on the pass line or adjusting the linear velocity. The lower limits of the fiber vibration amplitude and vibration frequency are not particularly limited.

[0040] In this embodiment, among the molecules constituting the photoinitiator contained in the ultraviolet curable resin, at least one molecule has a maximum molar absorption coefficient of 500 L·mol in methanol at a wavelength of 220 nm or more and 320 nm or less. －１ ·cm －１ or more. In order to efficiently cure the resin, it is advisable to match the absorption wavelength of the photoinitiator with the wavelength region of the ultraviolet LED used, and at that wavelength, the molar absorption coefficient is 500 L·mol －１ ·cm －１ or more. A large molar absorption coefficient allows the curing reaction to proceed more efficiently. The molar absorption coefficient of at least one molecule constituting the photoinitiator in methanol may be 500 L·mol －１ ·cm －１ or more at the peak wavelength of the second light source. The upper limit of the molar absorption coefficient is not particularly limited. For example, the maximum molar absorption coefficient in methanol at a wavelength of 220 nm or more and 320 nm or less is 50000 L·mol－１ ・cm －１ The following is also acceptable.

[0041] Although the method for manufacturing optical fibers according to the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above.

[0042] In the above, Figure 1 shows optical fiber 1A as an example of an optical fiber manufactured by the optical fiber manufacturing method of this disclosure, but the configuration of an optical fiber manufactured by the optical fiber manufacturing method of this disclosure is not limited to the configuration of optical fiber 1A. For example, an optical fiber manufactured by the optical fiber manufacturing method of this disclosure does not have to include a colored resin layer. In the manufacturing apparatus of Figure 2, the colored resin layer may be formed in a post-processing step after the optical fiber has been wound onto the winding machine 80.

[0043] Although the above describes an example using four ultraviolet irradiation furnaces, the number of ultraviolet irradiation furnaces in the optical fiber manufacturing method of this disclosure is not particularly limited and may be, for example, two to twenty. In the above embodiment, three ultraviolet irradiation furnaces having a first light source and one ultraviolet irradiation furnace having a second light source are used, but the combination of the number of each ultraviolet irradiation furnace is not particularly limited and may be, for example, two ultraviolet irradiation furnaces having a first light source and two ultraviolet irradiation furnaces having a second light source.

[0044] The above describes an example in which two types of ultraviolet LEDs, a first light source and a second light source, are used in the curing process. However, in the optical fiber manufacturing method of this disclosure, ultraviolet LEDs having peak wavelengths different from both the first and second light sources may be used further. That is, the irradiation of ultraviolet light in the curing process may be carried out using two types of ultraviolet LEDs, or it may be carried out using three or more types of ultraviolet LEDs.

[0045] 1 Optical fiber base material 1A Optical fiber 10 Glass fiber 12 Core 14 Cladding 20 Coating resin film 22 Primary resin layer 24 Secondary resin layer 26 Colored resin layer 30 Cooling device 40 Coating device 51 First ultraviolet irradiation furnace 52 Second ultraviolet irradiation furnace 53 Third ultraviolet irradiation furnace 54 Fourth ultraviolet irradiation furnace 61, 62, 63, 64 Guide roller 70 Take-up machine 80 Winding machine 100 Heating furnace 101 Furnace tube 102 Heater

Claims

1. A method for manufacturing an optical fiber, comprising a coating step of applying an ultraviolet-curable resin to a glass fiber, and a curing step of curing the ultraviolet-curable resin by irradiating it with ultraviolet light, wherein the irradiation of ultraviolet light in the curing step is performed using a first light source and a second light source, both of which are ultraviolet LEDs, and the peak wavelength of the first light source and the peak wavelength of the second light source are different.

2. The method for manufacturing an optical fiber according to claim 1, wherein the peak wavelength of the second light source is shorter than the peak wavelength of the first light source, and in the curing step, irradiation with ultraviolet light from the second light source is performed after irradiation with ultraviolet light from the first light source.

3. A method for manufacturing an optical fiber according to claim 1 or 2, wherein the peak wavelength of the first light source is 320 nm or more and 400 nm or less, and the peak wavelength of the second light source is 100 nm or more and less than 320 nm.

4. The method for manufacturing an optical fiber according to any one of claims 1 to 3, wherein the oxygen concentration near the glass fiber when ultraviolet light is irradiated in the first light source and the second light source is 1000 ppm or less.

5. A method for manufacturing an optical fiber according to any one of claims 1 to 4, wherein the coating eccentricity of the manufactured optical fiber is 15 μm or less.

6. The method for manufacturing an optical fiber according to any one of claims 1 to 5, wherein in the first light source and the second light source, the fiber vibration amplitude during ultraviolet irradiation is 3 mm or less, and the maximum peak of the vibration frequency is 200 Hz or less.

7. Of the molecules constituting the photopolymerization initiator contained in the UV-curing resin, at least one molecule has a maximum molar extinction coefficient of 500 L·mol in methanol at a wavelength of 220 nm to 320 nm. －１ ・cm －１ The method for manufacturing an optical fiber according to any one of claims 1 to 6.

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