JP2016124731A - Method for producing optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an optical fiber having a good quality coating in which a resin is sufficiently cured and having a good surface nature.SOLUTION: A method for producing an optical fiber is provided that comprises: a resin application step of applying an ultraviolet-curable resin onto an outer circumference of a running glass optical fiber; an accompanied gas flow formation step of forming an accompanied gas flow composed of an inert gas in the vicinity of a surface of the resin by passing the glass optical fiber having the resin applied thereon through a first inert gas atmosphere forming part; a coating formation step of forming a coating by curing the resin by passing the glass optical fiber having the resin applied thereon and covered with the accompanied gas flow through an ultraviolet light irradiating part comprising an ultraviolet light source which emits ultraviolet light and an ultraviolet light transmitting tube which transmits the ultraviolet light. The first inert gas atmosphere forming part and the ultraviolet irradiating part are separated from each other, and the glass optical fiber having the resin applied thereon is passed through a second inert gas atmosphere forming part which is supplied with an inert gas and which is disposed in the ultraviolet irradiating part at a side where the glass optical fiber is inserted.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical fiber manufacturing method in which a coating is formed on a glass optical fiber.

  An optical fiber is formed by heating and melting one end of an optical fiber preform made of glass in a drawing furnace, drawing the glass optical fiber from the one end, and forming a resin coating on the outer periphery of the drawn glass optical fiber. Manufactured.

  The coating of the optical fiber is generally formed as follows. First, a glass optical fiber is passed through a resin coating die in which an ultraviolet curable resin (hereinafter, appropriately referred to as a resin) is stored, and the resin is coated. Next, the glass optical fiber coated with resin is passed through a coating forming apparatus.

  The coating forming apparatus is made of, for example, quartz glass, and includes a transparent tube that transmits ultraviolet rays, and an ultraviolet ray source disposed on the outer periphery of the transparent tube. Then, while passing the glass optical fiber coated with the resin through the transparent tube of the coating forming apparatus, the resin is cured by irradiating ultraviolet rays from the periphery of the transparent tube with an ultraviolet source to form a coating.

Here, when the ultraviolet curable resin is generally cured in an atmosphere having a high oxygen (O ₂ ) concentration, it reacts with oxygen to be insufficiently cured, resulting in a low quality coating. In order to prevent this, the technique which irradiates ultraviolet rays to resin under inert gas atmosphere is disclosed (for example, refer patent documents 1-3).

Japanese Patent Laid-Open No. 6-211545 JP 2011-168457 A JP 2012-236728 A Japanese Patent No. 5202951 JP 2010-210711 A

  However, in recent years, the drawing speed of an optical fiber tends to be further increased, and there is a problem that the resin is insufficiently cured in the manufactured optical fiber and the surface property may be deteriorated.

  The present invention has been made in view of the above, and an object of the present invention is to provide a method of manufacturing an optical fiber capable of manufacturing an optical fiber having a good surface property having a good quality coating in which a resin is sufficiently cured. It is to provide.

  In order to solve the above-described problems and achieve the object, an optical fiber manufacturing method according to one aspect of the present invention includes a resin coating step of applying an ultraviolet curable resin to the outer periphery of a traveling glass optical fiber, and a resin A glass optical fiber coated with a gas is passed through the first inert gas atmosphere forming section to form an accompanying flow comprising an inert gas in the vicinity of the surface of the resin, and a resin covered with the accompanying flow A coating forming step of curing the resin to form a coating by passing the coated glass optical fiber through an ultraviolet irradiation unit having an ultraviolet light source that emits ultraviolet rays and an ultraviolet transmission tube that transmits ultraviolet rays. The first inert gas atmosphere forming unit and the ultraviolet irradiation unit are spaced apart from each other, and the second inert gas is supplied to the ultraviolet irradiation unit on the side where the glass optical fiber is inserted. Sexual gas atmosphere forming part, and wherein the passing the glass optical fiber resin has been applied.

  An optical fiber manufacturing method according to an aspect of the present invention is characterized in that, in the above-described invention, the oxygen concentration inside the second inert gas atmosphere forming part is 300 ppm or less.

  In the method for manufacturing an optical fiber according to one aspect of the present invention, in the above invention, the second inert gas atmosphere forming part is composed of an upper sealing member disposed above the ultraviolet irradiation part, One end of the permeation tube is included, and in the coating forming step, an inert gas is introduced into the upper sealing member through at least two systems of introduction paths, and one of the two systems of introduction paths is introduced. The supply port is located inside the ultraviolet transmissive tube, and the supply port of the other one system introduction path is located inside the upper sealing member and outside the ultraviolet transmissive tube.

  An optical fiber manufacturing method according to an aspect of the present invention is characterized in that, in the above-described invention, an inert gas is introduced at least in the vicinity of the glass optical fiber at a flow rate of 35 L / min or more in the coating forming step.

  In the optical fiber manufacturing method according to one aspect of the present invention, in the above invention, the optical fiber is an optical fiber colored core wire in which at least one of the coating layers is colored.

  According to the method for manufacturing an optical fiber according to the present invention, it is possible to manufacture an optical fiber having a good quality coating in which a resin is sufficiently cured and having excellent surface properties.

FIG. 1 is a schematic diagram showing an overall configuration of an optical fiber manufacturing apparatus used for carrying out an optical fiber manufacturing method according to an embodiment. FIG. 2 is a schematic diagram showing details of the resin coating die and the coating forming apparatus of FIG. FIG. 3 is a schematic diagram for explaining a first arrangement pattern of the inert gas introduction path in the coating forming apparatus according to the embodiment. FIG. 4 is a schematic diagram for explaining a second arrangement pattern of the inert gas introduction path in the coating forming apparatus according to the embodiment. FIG. 5 is a schematic diagram showing an outline of a Knot Test performed in an example based on the embodiment and a comparative example. FIG. 6 is a cross-sectional view for explaining a general loose tube cable structure. FIG. 7 is a schematic diagram illustrating a modification of the overall configuration of the optical fiber manufacturing apparatus used for carrying out the optical fiber manufacturing method according to the first embodiment.

  Embodiments of an optical fiber manufacturing method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In the drawings, the same or corresponding elements are denoted by the same reference numerals.

(Optical fiber manufacturing equipment)
FIG. 1 is a schematic diagram showing an overall configuration of an optical fiber manufacturing apparatus used for carrying out an optical fiber manufacturing method according to an embodiment of the present invention. As shown in FIG. 1, the manufacturing apparatus 100 includes a drawing furnace 10, a resin coating die 20, a coating forming apparatus 30, guide rollers 40 and 50, and a winding drum 60.

  The drawing furnace 10 includes a heater 10a for heating and melting one end of the optical fiber preform 1 mainly composed of quartz glass. A resin coating die 20 as a resin coating device is disposed below the drawing furnace 10 in a path of the glass optical fiber 2 drawn from one end of the optical fiber preform 1. The coating forming apparatus 30 is disposed below the resin coating die 20. The guide roller 40 is disposed below the coating forming apparatus 30. The guide roller 50 is disposed so as to guide the optical fiber 3 taken up by the guide roller 40 to the winding drum 60. The guide roller 40 is configured to be able to control the drawing speed.

  FIG. 2 is a schematic diagram of the resin coating die 20 and the coating forming apparatus 30 shown in FIG. As shown in FIG. 2, the resin coating die 20 includes resin supply pipes 20a and 20b for supplying two types of liquid resins. The resin is an ultraviolet curable resin, and the two types of liquid resins are generally a primary resin that covers the outer periphery of the glass optical fiber 2 and a secondary resin that further covers the primary resin. The resin coating die 20 is configured such that two types of liquid resins to be coated on the glass optical fiber 2 can be coated on the outer periphery of the glass optical fiber 2 (see, for example, Patent Document 4).

  The coating forming apparatus 30 includes a protective tube 31, an upper sealing member 32, a transparent tube 33, an ultraviolet light source 34, a reflection mirror 35, a housing 36, a lower sealing member 37, and an oximeter 38. The The protective tube 31 as the first inert gas atmosphere forming part is provided so as to be connected to the resin coating die 20.

  The upper sealing member 32 is provided on the upper side of the housing 36 while being separated from the protective tube 31 below the protective tube 31. In the upper part of the upper sealing member 32, an opening (not shown) through which the glass optical fiber 2a can pass is formed. In addition, the transparent tube 33 as an ultraviolet ray transmitting tube through which the glass optical fiber 2 a passes is provided with a cylindrical body portion in the housing 36. The upper end of the transparent tube 33 is disposed so as to be included in the upper sealing member 32. Further, the lower sealing member 37 is provided on the lower side of the housing 36, and an opening (not shown) through which the glass optical fiber 2a can pass is formed in the lower part. The lower end of the transparent tube 33 is disposed so as to be enclosed in the lower sealing member 37. The lower sealing member 37 is connected to an exhaust pipe 37a for exhausting the gas inside the transparent pipe 33.

  Both the ultraviolet light source 34 and the reflection mirror 35 are disposed inside the housing 36. A plurality of reflecting mirrors 35 as ultraviolet reflecting mirrors are provided inside the housing 36 so as to face the ultraviolet light source 34. The plurality of reflection mirrors 35 are provided so as to sandwich the transparent tube 33. The housing 36 is installed so as to fix and hold the transparent tube 33, the ultraviolet light source 34, and the reflection mirror 35. The oxygen concentration meter 38 is connected to the oxygen concentration sensor 38a and configured to measure the oxygen concentration in the upper sealing member 32.

The protective tube 31 is formed in a tubular shape, and the material is, for example, glass, metal, plastic or the like, but is not particularly limited. In addition, a space between the protective tube 31 and the resin coating die 20 is a sealed structure that does not allow air to enter. The protective tube 31 has an inert gas supply tube 31 a for supplying an inert gas such as nitrogen (N ₂ ) gas in the protective tube 31. As the inert gas, nitrogen (N ₂ ), carbon dioxide (CO ₂ ), helium (He) gas, argon (Ar) gas, or the like can be used without particular limitation.

  The inert gas supply pipe 31a is connected to a gas supply source (not shown) for supplying an inert gas via a flow rate regulator (not shown). The flow rate regulator controls the supply amount and flow rate of the inert gas. The flow controller is, for example, a mass flow controller, but may be a control valve.

  The upper sealing member 32 is made of, for example, stainless steel, and iron, aluminum, quartz glass, or the like can also be used. The upper sealing member 32 is configured such that a cylindrical body and a top plate in which an opening through which the glass optical fiber 2a is inserted is formed are formed integrally or separately. The lower part of the upper sealing member 32 is fixed to the upper part of the housing 36 so as to pass through the glass optical fiber 2 a without communicating with the housing 36. The oxygen concentration meter 38 has an oxygen concentration sensor 38 a installed in the upper sealing member 32. For example, the oxygen concentration meter 38 can measure the oxygen concentration in the vicinity of the transparent tube 33 inside the upper sealing member 32 by the oxygen concentration sensor 38a.

  The transparent tube 33 is made of, for example, quartz glass having transmittance characteristics suitable for ultraviolet transmission, but is not particularly limited as long as it transmits ultraviolet light for curing the resin. The transparent tube 33 is formed of a cylindrical tube, preferably, for example, a cylindrical tube through which the glass optical fiber 2a coated with resin can pass.

  The lower sealing member 37 is made of, for example, stainless steel, and iron, aluminum, quartz glass, or the like can also be used. The lower sealing member 37 is configured such that a cylindrical body portion and a bottom plate in which an opening for allowing the glass optical fiber 2a to pass are formed integrally or separately. The upper part of the lower sealing member 37 is fixed to the lower part of the casing 36 so as to cover the lower end of the transparent tube 33 in a state where it can pass through the glass optical fiber 2 a without communicating with the casing 36.

  The exhaust pipe 37a provided in the lower sealing member 37 is connected to an intake pump (both not shown) via a regulating valve. The gas exhausted from the transparent tube 33 is exhausted through the exhaust pipe 37a by the intake pump. Further, as described above, the lower sealing member 37 and the housing 36 are not in communication. Therefore, the gas that has not been exhausted through the exhaust pipe 37 a in the lower sealing member 37 remains in the lower sealing member 37 or is exhausted from an opening (not shown) formed in the bottom plate of the lower sealing member 37. The

  The upper sealing member 32, the transparent tube 33, and the lower sealing member 37 as the second inert gas atmosphere forming unit described above are arranged so that the glass optical fiber 2a is inserted in order, and the glass optical fiber 2a The atmosphere is an inert gas atmosphere. The materials and shapes of the upper sealing member 32, the transparent tube 33, and the lower sealing member 37 are not necessarily limited to the materials and shapes described above.

  In addition, in the upper sealing member 32, inert gas introduction paths 321 and 322 are provided in a region through which the glass optical fiber 2 a coated with resin passes. The inert gas introduction paths 321 and 322 are each connected to an inert gas supply source (both not shown) via a flow rate regulator.

The inert gas introduction path 321 as one system of one introduction path is configured to be able to supply an inert gas at a first flow rate in the vicinity of the glass optical fiber 2a coated with the entering resin. For example, the supply port of the inert gas introduction path 321 is located inside the transparent tube 33. Further, the inert gas introduction path 322 as one system of the other introduction path has, for example, a supply port located in the upper sealing member 32 and in the vicinity of the upper portion of the transparent tube 33. The inert gas introduction path 322 is configured to be able to supply an inert gas at a second flow rate near the upper portion of the transparent tube 33 inside the upper sealing member 32. Here, as described above, the upper sealing member 32 and the housing 36 are not in communication. Therefore, the inert gas that has not been introduced into the transparent tube 33 stays in the upper sealing member 32 or is discharged through an opening (not shown) formed in the upper portion of the upper sealing member 32. As the inert gas, nitrogen (N ₂ ), carbon dioxide (CO ₂ ), helium (He) gas, argon (Ar) gas, or the like can be used without particular limitation.

  Here, an example of an installation pattern of the inert gas introduction paths 321 and 322 in this embodiment will be described. 3 and 4 show schematic diagrams of examples of these installation patterns. 3 and 4, the upper diagram is a schematic diagram from the side, and the lower diagram is a schematic diagram from above.

  As shown in FIG. 3, the first arrangement pattern of the inert gas introduction passages according to this embodiment is such that the inert gas introduction passages 321A and 322A have the same height in the upper sealing member 32 and have a circular cross section. It is the installation pattern extended | stretched and provided inside from the side surface of the cylindrical part of both sides. Then, the inert gas is mainly introduced into the transparent tube 33 at the first flow rate through the inert gas introduction path 321A. Further, the inert gas is mainly introduced into the upper sealing member 32 at the second flow rate through the inert gas introduction path 322A. In this case, the inert gas of the first flow rate and the inert gas of the second flow rate are introduced into the upper sealing member 32 and the transparent tube 33 from positions facing each other at the same height. The glass optical fiber 2a passes through the opening 321Aa formed in the inert gas introduction path 321A.

  On the other hand, as shown in FIG. 4, the second arrangement pattern of the inert gas introduction path according to this embodiment is that the inert gas introduction paths 321B and 322B are stepped while facing each other in the upper sealing member 32. It is the arrangement | positioning pattern extended | stretched and provided inside from the side surface of the cylindrical part of the both sides of a cross-sectional circle. The inert gas introduction paths 321B and 322B have opposite steps. Then, the inert gas is mainly introduced into the transparent tube 33 at the first flow rate through the inert gas introduction path 321B. Further, the inert gas is mainly introduced into the upper sealing member 32 at the second flow rate through the inert gas introduction path 322B. In this case, the inert gas having the first flow rate and the inert gas having the second flow rate are introduced into the upper sealing member 32 and the transparent tube 33 at different levels. The glass optical fiber 2a passes through the opening 321Ba formed in the inert gas introduction path 321B.

  3 and 4, the inert gas introduction path 321 and the inert gas introduction path 322 are arranged at an angle of 90 degrees, for example, as viewed from above, but the arrangement of both is in this form. It is not limited to. Specifically, the inert gas introduction path 321 and the inert gas introduction path 322 may be disposed so as to overlap each other when viewed from above, that is, at an angle of 0 degrees with each other. Alternatively, they may be arranged to form a predetermined angle other than 90 degrees.

  As shown in FIG. 2, the ultraviolet light source 34 is, for example, a UV lamp, but is not particularly limited as long as it can emit ultraviolet light that can cure the ultraviolet curable resin. The reflection mirror 35 is composed of a concave mirror that can reflect ultraviolet rays, but is not limited to a concave mirror as long as the reflected ultraviolet rays can be irradiated onto the glass optical fiber 2a. The housing 36 is preferably made of a material or a structure that does not leak ultraviolet rays to the outside. Further, the housing 36 may be provided with a fixture for fixing the upper sealing member 32 and the transparent tube 33 to the housing 36. The upper sealing member 32, the transparent tube 33, the ultraviolet light source 34, the reflection mirror 35, and the housing 36 constitute an ultraviolet irradiation unit 39.

(Optical fiber manufacturing method)
Next, the manufacturing method of the optical fiber by embodiment using the manufacturing apparatus 100 comprised as mentioned above is demonstrated. First, the optical fiber preform 1 is set in the drawing furnace 10. Next, one end of the optical fiber preform 1 is heated and melted by a heater 10a included in the drawing furnace 10, and the glass optical fiber 2 is drawn from the heated and melted end. The drawn glass optical fiber 2 travels downward and passes through the resin coating die 20. The resin coating die 20 stores two types of resins supplied from the resin supply pipes 20a and 20b. The resin application die 20 applies, for example, two layers of resin of an inner peripheral primary coating and an outer peripheral secondary coating to the outer periphery of the glass optical fiber 2 that passes while traveling (see, for example, Patent Document 4). In this way, the resin coating process is performed.

  Subsequently, the glass optical fiber 2a coated with the two layers of resin enters the coating forming apparatus 30 immediately after the resin is coated. In the coating forming apparatus 30, the glass optical fiber 2 a coated with resin is cured by the ultraviolet light irradiated by the ultraviolet light source 34, and the optical fiber 3 is formed. In this way, the coating forming process is performed.

  Next, the guide rollers 40 and 50 shown in FIG. 1 guide the optical fiber 3 on which the coating is formed. The winding drum 60 finally winds the optical fiber 3 guided by the guide rollers 40 and 50. The traveling speed (linear speed) of the glass optical fibers 2 and 2a and the optical fiber 3 is controlled by adjusting the rotational speed of the guide roller 40.

  Below, the detail of the coating | coated formation process mentioned above is demonstrated. That is, in the coating forming apparatus 30, the glass optical fiber 2 a coated with resin first passes through the protective tube 31. The protective tube 31 has an inert gas atmosphere due to the inert gas supplied through the inert gas supply tube 31a. By passing the glass optical fiber 2a through this inert gas atmosphere, an accompanying flow f made of an inert gas is formed in the vicinity of the surface around the resin. Thus, the accompanying flow formation process is performed.

  Next, the glass optical fiber 2a enters the upper sealing member 32 with the accompanying flow f made of an inert gas. The accompanying flow f is formed more stably as the drawing speed of the optical fiber is higher, and is not easily peeled off from the glass optical fiber 2a. Here, the drawing speed for stably forming the accompanying flow f is 500 m / min or more, more preferably 850 m / min or more. The resin applied to the glass optical fiber 2a is protected by the accompanying flow f. Therefore, contact with oxygen is suppressed even in a region between the protective tube 31 and the upper sealing member 32 where the resin applied to the glass optical fiber 2a is exposed to the outside air.

  Further, an inert gas is supplied into the upper sealing member 32 in the vicinity of the glass optical fiber 2a through the inert gas introduction paths 321 and 322. Thereby, the accompanying flow f is further enhanced, and the resin of the glass optical fiber 2a is protected by the inert gas supplied through the inert gas introduction paths 321 and 322 (mainly the inert gas introduction path 321). Thereby, the resin of the glass optical fiber 2a is further suppressed from contacting with oxygen. Further, by supplying an inert gas into the upper sealing member 32 through the inert gas introduction paths 321 and 322 (mainly the inert gas introduction path 322), the pressure in the upper sealing member 32 is changed from the atmospheric pressure. Also make it bigger. Thereby, the sealing performance with respect to the opening (not shown) provided in the upper part of the upper sealing member 32 through which the glass optical fiber 2a passes is improved. Therefore, it is possible to further suppress oxygen from entering the upper sealing member 32 from the outside through the opening.

  Here, it is preferable that the oxygen concentration measured by the oxygen concentration sensor 38a is 300 ppm or less at least in the vicinity of the glass optical fiber 2a in the upper sealing member 32. Thereby, it can suppress further that resin of glass optical fiber 2a contacts oxygen. When the oxygen concentration in the vicinity of the glass optical fiber 2a exceeds 300 ppm, the resin is not sufficiently cured, and the surface property of the formed optical fiber may be deteriorated. In this case, the winding state when the bobbin is aligned and wound is deteriorated. Further, there is a possibility that the transmission loss (loss) is deteriorated when the cable is used.

  Further, the flow rate of the inert gas supplied to the inside of the upper sealing member 32 and the transparent tube 33 through the inert gas introduction paths 321 and 322, that is, the sum of the first flow rate and the second flow rate is 35 L / min or more. It is preferable to do this. In addition, you may comprise an inert gas introduction path from a single introduction path. Also in this case, the flow rate of the inert gas introduced into the upper sealing member 32 is preferably 35 L / min or more. As a result, the accompanying flow f can be increased, the atmosphere inside the upper sealing member 32 can be set to an atmospheric pressure higher than atmospheric pressure, and the entry of outside air containing oxygen from the opening of the upper sealing member 32 can be suppressed. Therefore, it can further suppress that oxygen contacts the glass optical fiber 2a passing through the upper sealing member 32.

  Further, the gas in the transparent pipe 33 and the lower sealing member 37 is exhausted through the exhaust pipe 37a by the intake pump. Here, the flow rate of the exhausted gas is adjusted by an adjustment valve or the like. Thereby, since the volatilized resin component is sufficiently exhausted without adhering to the inner surface, fogging of the transparent tube 33 can be suppressed, and a sufficient amount of ultraviolet rays can reach the resin. Here, in order to sufficiently exhaust the volatilized resin component, it is preferable that the flow rate of the atmospheric gas in the transparent tube 33 is 1.8 m / s or more.

  Further, the coating forming apparatus 30 is likely to vibrate as the gas is exhausted. When this vibration is transmitted to the resin coating die 20, a coating failure occurs when the resin is applied to the glass optical fiber 2, and a coating failure may occur due to this. Therefore, in this embodiment, the coating forming apparatus 30 is provided apart from the resin coating die 20. Thereby, it is possible to prevent the vibration of the coating forming apparatus 30 from being transmitted to the resin coating die 20, and it is possible to suppress defective coating and defective coating.

  In this way, the resin is prevented from reacting with oxygen, and further, the inner surface of the transparent tube 33 is suppressed so that the resin is sufficiently cured by a sufficient amount of ultraviolet rays. As a result, the optical fiber 3 having a good quality coating is manufactured.

  As described above, according to the method for manufacturing an optical fiber according to the present invention, it is possible to manufacture the optical fiber 3 having a good quality coating in which the resin is sufficiently cured. In particular, according to the above-described embodiment, not only the accompanying flow f formed by passing the glass optical fiber 2a under the inert gas atmosphere, but also the inert gas in the upper sealing member 32 and the transparent tube 33. By introducing, it is suppressing that the resin of the surface of the glass optical fiber 2a and oxygen contact. Thereby, a good quality coating can be formed and the surface property of the optical fiber 3 to be manufactured can be further improved.

(Modification)
In the above-described embodiment, an example using the so-called wet-on-wet method in which the primary layer resin and the secondary layer resin are applied and then cured is described, but the present invention is not necessarily limited to this method. Specifically, it is also possible to use a so-called wet-on-dry method in which a primary resin is applied and then cured, and a secondary resin is applied thereon and cured.

  FIG. 7 is a schematic diagram showing the overall configuration of an optical fiber manufacturing apparatus that employs a wet-on-dry system as a modification. As shown in FIG. 7, an optical fiber manufacturing apparatus 200 is the same as the manufacturing apparatus 100 shown in FIG. 1, except that the resin coating die 20 is replaced with a resin coating die 20A and the protective tube 31 is replaced with a protective tube 31A. The manufacturing apparatus 200 has a configuration in which a resin coating die 20B as a resin coating apparatus, a protective tube 31B, and a coating forming apparatus 30B are further added between the coating forming apparatus 30A and the guide roller 40. Since other configurations are the same as those of the manufacturing apparatus 100, description thereof is omitted. The resin coating dies 20A and 20B include resin supply pipes 20Aa and 20Ba for supplying a liquid resin, respectively. The glass optical fiber 2 passes through the coating forming apparatus 30A, whereby the primary coated optical fiber 2A is formed. Subsequently, the optical fiber 3 is formed by the primary coating optical fiber 2A passing through the coating forming apparatus 30B.

  In such a configuration, the coating forming apparatus 30 according to the above-described embodiment can be applied as both the coating forming apparatus 30A for curing the primary resin and the coating forming apparatus 30B for curing the secondary resin. The coating forming apparatus 30 according to the embodiment is particularly effective when employed in the coating forming apparatus 30B that cures the secondary resin that forms the outermost layer.

  Further, in recent years, from the viewpoint of cost reduction, an optical fiber colored core wire having a two-layer structure in which either a primary layer or a secondary layer as a coating layer is colored and there is no colored layer on the outer periphery of the optical fiber has been adopted. . In the case of such a two-layered optical fiber colored core, the surface property is inferior to that of a three-layered colored core having a rigid colored layer as the outermost layer. Increase is likely to occur. In particular, when the optical fiber cable is a loose tube cable, which will be described later, the loss may increase due to contact between the optical fibers. Therefore, the present invention is particularly effective when used in manufacturing such a two-layered optical fiber colored core.

(Examples 1-12, Comparative Examples 1-4)
Next, as Examples 1 to 12 and Comparative Examples 1 to 4 of the present invention, optical fibers were manufactured using the optical fiber manufacturing apparatus 100 shown in FIG. Here, the implementation conditions are the linear velocity of the glass optical fiber 2a, the flow rate (first flow rate, second flow rate) of the inert gas introduced into the upper sealing member 32 and the transparent tube 33, the type, the inflow position, and the ultraviolet light. For example, the bulb type of the light source 34.

  Table 1 is a table showing the measurement values of the implementation conditions in Examples 1 to 12, the oxygen concentration in the upper sealing member 32, the Knot Test, and the loose tube loss at a wavelength of 1.55 μm. Table 2 is a table showing the measurement values of the implementation conditions in Comparative Examples 1 to 4, the oxygen concentration in the upper sealing member 32, the Knot Test, and the loose tube loss at a wavelength of 1.55 μm. In Tables 1 and 2, the case where all the conditions that Knot Test was 0.020 or more and 0.100 or less and the loose tube loss was 0.23 dB / km or less was judged as “◯”. On the other hand, the case where at least one of Knot Test and loose tube loss did not satisfy the above-described conditions was determined as “x”.

In Tables 1 and 2, “FIG. 3” and “FIG. 4” at the inflow positions are “inert gas introduction paths 321A and 322A of the first arrangement pattern” as the above-described inert gas introduction paths 321 and 322, respectively. This means that “the second arrangement pattern of the inert gas introduction paths 321B and 322B” (see FIG. 4) is used. In addition, Example 8 in Table 1 is an example at the time of using the inert gas introduction path 321 single. As the inert gas, either N ₂ or CO ₂ was used. In Comparative Example 4, an example in which O ₂ is used in order to confirm that an inert gas is effective as a gas introduced into the upper sealing member 32 and the transparent tube 33 will be described.

  Further, in Tables 1 and 2, “D” and “H” of the valves mean “D valve” and “H valve”, respectively. The D bulb is an ultraviolet light source showing an emission spectrum equivalent to that of a metal halide lamp, and the H bulb is an ultraviolet light source showing an emission spectrum equivalent to that of a high pressure mercury lamp. The H bulb has a higher emission intensity in a short wavelength region (for example, 200 to 350 nm) than in a long wavelength region (for example, 350 to 450 nm). On the other hand, in the D bulb, the emission intensity in the long wavelength region is stronger than the short wavelength region. The short wavelength ultraviolet light is effective for curing at a portion close to the surface of the optical fiber, and the long wavelength ultraviolet light is effective for curing at a portion deep from the surface of the optical fiber. Therefore, these UV light sources are selected according to the absorption peak of the photoinitiator blended in the UV curable resin, and the optical peak of the optical fiber is adjusted by combining the absorption peak wavelength of the photoinitiator with the wavelength having a strong emission intensity in the emission spectrum The curing reaction can be efficiently caused both in the vicinity of the surface and in the deep part.

  Moreover, Knot Test in Table 1 and Table 2 is evaluation of the dynamic friction force of the surface of the produced optical fiber (refer patent document 5). FIG. 5 is a schematic diagram showing an outline of the Knot Test performed in this example and the comparative example. First, a single loop is formed between one end and the other end of the optical fiber manufactured as shown in FIG. 5, and the one end of the optical fiber is passed through the loop twice so that the optical fiber is doubled. Make a 7cm circle. In this state, the optical fiber comes into contact with itself at five points A to E. Both ends of this optical fiber are pulled at a speed of 5 mm / min by a tensile tester. By measuring the load at this time, the dynamic friction force on the surface of the optical fiber can be measured.

  Moreover, all of the optical fibers in Examples 1 to 12 and Comparative Examples 1 to 4 are optical fiber colored cores having a two-layer structure in which the secondary coating is colored. FIG. 6 shows a cross-sectional view of a loose tube cable structure using this optical fiber colored core wire. As shown in FIG. 6, the loose tube cable 70 includes a tension member 71, an optical fiber colored core wire 72, a loose tube 73, a jelly 74, and a sheath 75. The tension member 71 is made of metal or plastic. A plurality of loose tubes 73 made of metal or plastic are provided through the optical fiber colored core wire 72 on the cylindrical side surface of the tension member 71. The loose tubes 73 are covered with a sheath 75 made of plastic, and a gap between them is filled with a jelly 74.

  The values of loose tube loss in Tables 1 and 2 are the values of all the optical fiber colored core wires in the cable measured by an optical pulse tester (OTDR: Optical Time Domain Reflectometer) after the loose tube cable was formed. It is an average value of loss at a wavelength of 1.55 μm.

  As shown in Table 1, since the optical fibers according to Examples 1 to 12 of the present invention have good surface properties, increase in loss could be suppressed even when used for a loose tube. Moreover, it is preferable that it is an inert gas to introduce into the upper sealing member 32 and the transparent tube 33 from the comparison with Examples 1-12 shown in Table 1, and Comparative Examples 1-4 shown in Table 2. I can confirm that. Further, when the total flow rate of the inert gas introduced into the upper sealing member 32 and the transparent tube 33 is less than 35 L / min and the oxygen concentration in the upper sealing member 32 and the transparent tube 33 exceeds 300 ppm, Knot It can be confirmed that the numerical value of Test is out of the preferable range described above, and the surface property of the optical fiber 3 is deteriorated.

  Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible. For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as necessary within the scope of the present invention.

  For example, in the above-described embodiment, an inert gas introduction path 321 that introduces an inert gas into the upper sealing member 32 and the transparent tube 33 at a first flow rate, and an inert gas that is introduced at a second flow rate. Although two systems with the introduction path 322 are used, it is not limited to this. Specifically, a further inert gas introduction path for introducing an inert gas into the upper sealing member 32 and the transparent tube 33 at a third flow rate is provided, and three or more inert gas introduction paths are provided. It is also possible to use it.

DESCRIPTION OF SYMBOLS 1 Optical fiber base material 2, 2a Glass optical fiber 2A Primary coating optical fiber 3 Optical fiber 10 Drawing furnace 10a Heater 20, 20A, 20B Resin coating die 20a, 20b, 20Aa, 20Ba Resin supply pipe 30, 30A, 30B Coating formation Apparatus 31, 31A, 31B Protective tube 31a Inert gas supply tube 32 Upper sealing member 33 Transparent tube 34 Ultraviolet light source 35 Reflecting mirror 36 Housing 37 Lower sealing member 37a Exhaust pipe 38 Oxygen concentration meter 38a Oxygen concentration sensor 39 Ultraviolet irradiation Part 40, 50 Guide roller 60 Winding drum 70 Loose tube cable 71 Tension member 72 Optical fiber colored core wire 73 Loose tube 74 Jerry 75 Sheath 100, 200 Manufacturing equipment 321, 321A, 321B, 322A, 322A, 322B Inert gas guide Entry path 321Aa, 321Ba Opening f associated flow

Claims (5)

A resin application step of applying an ultraviolet curable resin to the outer periphery of the traveling glass optical fiber;
An accompanying flow forming step of passing the glass optical fiber coated with the resin through the first inert gas atmosphere forming portion to form an accompanying flow made of an inert gas in the vicinity of the surface of the resin;
The glass optical fiber coated with the resin covered with the accompanying flow is passed through an ultraviolet irradiation unit including an ultraviolet light source that emits ultraviolet rays and an ultraviolet transmission tube that transmits the ultraviolet rays, thereby curing the resin. And a coating forming step of forming a coating.
The first inert gas atmosphere forming part and the ultraviolet irradiation part are separated from each other,
Passing the glass optical fiber coated with the resin through a second inert gas atmosphere forming part to which an inert gas is supplied, provided on the side where the glass optical fiber is inserted in the ultraviolet irradiation part. A method for manufacturing an optical fiber.   2. The method of manufacturing an optical fiber according to claim 1, wherein an oxygen concentration inside the second inert gas atmosphere forming part is 300 ppm or less.   The second inert gas atmosphere forming part is composed of an upper sealing member disposed above the ultraviolet irradiation part, and includes one end of the ultraviolet transmission tube. The inert gas is introduced into the sealing member through at least two systems of introduction paths, and the supply port of one of the two systems of introduction paths is located inside the ultraviolet transmission tube. And the supply port of the other one system introduction path is located inside the upper sealing member and outside the ultraviolet ray transmissive tube. Production method.   4. The optical fiber manufacturing method according to claim 1, wherein an inert gas is introduced at a flow rate of 35 L / min or more into at least the vicinity of the glass optical fiber in the coating forming step. 5. .   The optical fiber manufacturing method according to any one of claims 1 to 4, wherein the optical fiber is an optical fiber colored core wire in which at least one of the coating layers is colored.

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