JP2023109095A - Optical fiber ribbon and method for manufacturing optical fiber ribbon - Google Patents

Abstract

To reduce the difference in microbend loss and strength between a plurality of optical fiber colored cores differing in the color of a colored layer.SOLUTION: Provided is an optical fiber ribbon comprising: a plurality of optical fiber colored cores, each of which includes an optical fiber bare wire, a primary layer formed from a first ultraviolet curable resin that covers the optical fiber bare wire, a secondary layer formed from a second ultraviolet curable resin that covers the primary layer, and a colored layer formed from a third ultraviolet curable resin that covers the secondary layer; and an adhesive layer formed from a fourth ultraviolet curable resin that covers the plurality of optical fiber colored cores, for connecting the plurality of optical fiber colored cores. The Young's modulus of the primary layer is lower than the Young's modulus of the first ultraviolet curable resin, and the difference in the Young's modulus of the primary layer between the optical fiber colored cores, of the plurality of optical fiber colored cores, differing in the color of the colored layer is 0.1 MPa or less.SELECTED DRAWING: Figure 6

Description

TECHNICAL FIELD The present invention relates to optical fiber ribbons and methods of manufacturing optical fiber ribbons.

A primary layer that covers the bare optical fiber, a secondary layer that covers the primary layer, and a colored layer that covers the secondary layer are each formed with a UV curable resin so as to have a desired Young's modulus, thereby manufacturing a colored optical fiber. Techniques are known (Patent Documents 1 and 2).
When the Young's modulus of the primary layer is set low, the external force applied to the bare optical fiber is buffered, and the transmission loss of light due to minute deformation of the bare optical fiber (hereinafter referred to as "micro bend loss") is suppressed. be able to. Conversely, when the Young's modulus of the secondary layer is set high, the bare optical fiber and the primary layer can be protected from external forces.
Also, an optical fiber ribbon is manufactured by covering a plurality of colored optical fiber core wires with an ultraviolet curable resin and irradiating ultraviolet (UV) rays to connect the plurality of colored optical fiber core wires to each other. Even if the Young's modulus of the primary layer is low in the colored optical fiber before the manufacturing process of the optical fiber ribbon, the Young's modulus of the primary layer increases when exposed to UV light during the manufacturing process of the optical fiber ribbon, resulting in microbend loss. causes the
On the other hand, in a method for manufacturing an optical fiber ribbon in which the primary layer has a Young's modulus close to the saturation Young's modulus (Patent Document 3), or by adding an ultraviolet absorber to the primary layer, unintended Young's modulus due to UV exposure in the post-process is reduced. A technique for preventing the rate from increasing has been proposed (Patent Document 4).

JP 2005-162522 A Japanese Patent Publication No. 2002-524581 WO2018/062364 Japanese Patent Publication No. 2019-505648

In the recent optical fiber production, due to the use of LEDs as UV light sources and the increase in drawing speed, optical fiber strands whose primary layer is not sufficiently cured are often used. In order to harden the primary layer sufficiently, manufacturing conditions are greatly restricted, for example, by increasing the number of UV light sources.

However, if UV irradiation is performed in a post-process on an optical fiber whose primary layer is not sufficiently cured, the Young's modulus of the primary layer increases. In addition, depending on the combination of the ultraviolet curable resin used in the colored layer and the wavelength of the ultraviolet light irradiated by the UV light source, the absorbance of the colored layer with respect to the UV light source varies depending on the color of the colored layer. Differences can occur in the amount of UV radiation that is transmitted through the colored layer and reaches the inner primary layer. For example, when the colored layer is cured using a UV-LED that irradiates ultraviolet light with a wavelength of 365 nm, if the absorbance of the ultraviolet curable resin used in the colored layer for ultraviolet light with a wavelength of 365 nm varies greatly depending on the color, the colored layer absorbs There may be differences in the amount of UV light applied. That is, there is a possibility that the degree of increase in the Young's modulus of the primary layer differs depending on the color of the colored layer. As a result, when an optical fiber ribbon is manufactured using a plurality of colored optical fiber core wires having colored layers with different colors, colored optical fiber core wires with significantly different Young's moduli of the primary layers may coexist in the same optical fiber ribbon. . Since the microbend loss generally worsens as the Young's modulus of the primary layer increases, it is conceivable that the microbend loss will change for each colored optical fiber core wire constituting the same optical fiber ribbon. If there is a difference in microbend loss between the colored optical fibers included in the same optical fiber ribbon, it becomes difficult to describe the specifications of the ribbon and to manage the usage of the ribbon. Furthermore, if the Young's modulus of the primary layer of the colored optical fiber core wires included in the same optical fiber ribbon is different, it is conceivable that the strength of each colored optical fiber core wire will be different.

On the other hand, in the manufacturing method described in Patent Document 3, since it is necessary to cure at a Young's modulus close to the saturation Young's modulus, the curing of the primary layer may not be sufficient due to, for example, the use of LEDs as the UV light source or an increase in the drawing speed. Not envisioned. Therefore, when the absorbance for the UV light source differs depending on the color used for the colored layer, the Young's modulus of the primary layer may vary due to the UV irradiation during the coloring process. In addition, in the manufacturing method described in Patent Document 4, it is necessary to minimize the spectral overlap between the photoinitiator and the ultraviolet absorber, which considerably limits the options for the resin composition of the colored core of the optical fiber. put away.

Accordingly, the present invention has been made in view of the above-described problems, and provides an optical fiber ribbon and an optical fiber ribbon that reduce the difference in microbend loss and strength between a plurality of colored optical fiber core wires having different colored layers. It is an object of the present invention to provide a method for manufacturing a fiber ribbon.

According to one aspect of the present invention, an optical fiber bare wire, a primary layer formed of a first ultraviolet curable resin covering the optical fiber bare wire, and a second ultraviolet curable resin covering the primary layer a plurality of colored optical fiber core wires each having a secondary layer and a colored layer formed of a third UV curable resin covering the secondary layer; and a fourth UV curable core wire covering the plurality of colored optical fiber core wires. an adhesive layer formed of a mold resin and connecting the plurality of colored optical fibers, wherein the Young's modulus of the primary layer is higher than the maximum Young's modulus of the first ultraviolet curable resin. and that the difference in the Young's modulus of the primary layer between the optical fiber colored core wires having the colored layers of different colors among the plurality of colored optical fiber core wires is 0.1 MPa or less. A featured optical fiber ribbon is provided.

According to another aspect of the present invention, a step of drawing a bare optical fiber from an optical fiber preform; and applying a first ultraviolet curable resin around the bare optical fiber to form a primary layer. and a step of applying a second ultraviolet curable resin around the primary layer and irradiating the second ultraviolet curable resin with ultraviolet rays to form a secondary layer, thereby manufacturing an optical fiber strand. a step of applying a third ultraviolet curable resin around the optical fiber strand and irradiating the third ultraviolet curable resin with the ultraviolet rays to form a colored layer, thereby manufacturing a colored optical fiber core wire; and applying a fourth ultraviolet curable resin around the plurality of colored core wires of the optical fibers, and irradiating the fourth ultraviolet curable resin with the ultraviolet rays to form an adhesive layer, whereby the plurality of optical fibers and a step of manufacturing an optical fiber ribbon in which colored core wires are connected, wherein the Young's modulus of the primary layer is lower than the maximum Young's modulus of the first ultraviolet curable resin, and the plurality of colored core wires of the optical fibers. Among them, there is provided a method for manufacturing an optical fiber ribbon, wherein the difference in the Young's modulus of the primary layer between the optical fiber colored core wires having the colored layers of different colors is 0.1 MPa or less. be.

ADVANTAGE OF THE INVENTION According to the present invention, it is possible to provide an optical fiber ribbon and a method for manufacturing an optical fiber ribbon that reduce differences in microbend loss and strength between a plurality of colored optical fiber core wires having colored layers of different colors.

1 is a cross-sectional view of an optical fiber colored core wire according to one embodiment; FIG. 1 is a cross-sectional view of an optical fiber bare wire according to an embodiment; FIG. 1 is a schematic diagram showing a part of a manufacturing apparatus used in a method for manufacturing a colored optical fiber cord according to one embodiment; FIG. FIG. 4 is a schematic diagram showing another part of the manufacturing apparatus used in the method for manufacturing the colored optical fiber cord according to the first embodiment; 1 is a cross-sectional view of an optical fiber ribbon according to one embodiment; FIG. 1 is a schematic diagram of a ribbon forming apparatus used in a method for manufacturing an optical fiber ribbon according to one embodiment; FIG. 1 is a flow chart of a method for manufacturing an optical fiber colored core wire and an optical fiber ribbon according to one embodiment. FIG. 5 is a graph showing the relationship between the difference in Young's modulus of the primary layer of the colored optical fiber core wire according to the example and the rate at which the microbend loss difference is 0.05 dB/km or more.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Elements having common functions throughout the drawings are denoted by the same reference numerals, and redundant description may be omitted or simplified.

FIG. 1A is a cross-sectional view of a colored optical fiber 1 according to this embodiment. The colored optical fiber core 1 consists of a bare optical fiber 2, a primary layer 3 coated on the outer circumference of the bare optical fiber 2, a secondary layer 4 coated on the outer circumference of the primary layer 3, and an outer circumference of the secondary layer 4. and a colored layer 5 coated with. The optical fiber bare wire 2 is coated with three coating layers, ie, a primary layer 3 , a secondary layer 4 and a colored layer 5 . FIG. 1B is a cross-sectional view of the optical fiber strand 6 according to this embodiment. The optical fiber strand 6 is a fiber in a state before the colored layer 5 is formed.

The optical fiber bare wire 2 is made of, for example, quartz-based glass or the like, and transmits light. The primary layer 3, the secondary layer 4, and the colored layer 5 are each formed by curing an ultraviolet curable resin by irradiating ultraviolet rays. The ultraviolet curable resin is not particularly limited as long as it can be polymerized by irradiation with ultraviolet rays. The UV curable resin is polymerizable by, for example, photoradical polymerization.

UV curable resins are polymerized and It is an ultraviolet curable resin having a polymerizable unsaturated group such as a curable ethylenically unsaturated group, and preferably has at least two polymerizable unsaturated groups.

Examples of the polymerizable unsaturated group in the ultraviolet curable resin include groups having unsaturated double bonds such as vinyl groups, allyl groups, acryloyl groups, and methacryloyl groups, groups having unsaturated triple bonds such as propargyl groups, and the like. mentioned. Among these, an acryloyl group and a methacryloyl group are preferable in terms of polymerizability.

The UV-curable resin may be a monomer, an oligomer, or a polymer that initiates polymerization and cures when irradiated with UV rays, but is preferably an oligomer. The oligomer is a polymer with a degree of polymerization of 2-100. Moreover, in this specification, "(meth)acrylate" means one or both of acrylate and methacrylate. The UV-curable resin contains any photopolymerization initiator (hereinafter referred to as "photoinitiator") having sensitivity in the UV region.

Polyether-based urethane (meth)acrylate is a polyether segment, (meth)acrylate and urethane bond, such as a reaction product of a polyol having a polyether skeleton, an organic polyisocyanate compound and a hydroxyalkyl (meth)acrylate. It is a compound having Further, the polyester urethane (meth)acrylate is a polyol having a polyester skeleton, a polyester segment, a (meth)acrylate and a urethane bond, such as a reaction product of an organic polyisocyanate compound and a hydroxyalkyl (meth)acrylate. is a compound.

Furthermore, the UV curable resin may contain, for example, diluent monomers, photosensitizers, chain transfer agents and various additives in addition to oligomers and photoinitiators. Monofunctional (meth)acrylates or polyfunctional (meth)acrylates are used as diluent monomers. Here, the diluting monomer means a monomer for diluting the ultraviolet curable resin.

The primary layer 3 is a soft layer and has a function of buffering external force applied to the bare optical fiber 2 . The primary layer 3 may still have room for curing when the optical fiber strand 6 is formed, but the Young's modulus of the primary layer 3 is maximum. In this embodiment, the maximum Young's modulus that the primary layer 3 of the optical fiber strand 6 can exhibit is defined as "maximum Young's modulus."

Irradiation of ultraviolet rays is performed at appropriate illuminance/irradiation amount at any time using, for example, a mercury lamp or UV-LED. In addition, the maximum Young's modulus varies depending on the optical fiber manufacturing conditions (e.g., line speed, UV irradiation intensity, type of UV light source, resin coating temperature, etc.), and is primarily determined by the UV-curable resin used. I don't get it. Further, in the optical fiber strand 6, the optical fiber colored core wire 1, and the optical fiber ribbon 100 according to the present embodiment, the Young's modulus of the primary layer 3 is lower than the maximum Young's modulus of the ultraviolet curable resin forming the primary layer 3. .

The secondary layer 4 is preferably a hard layer having a Young's modulus of 500 MPa or more, and has a function of protecting the bare optical fiber 2 and the primary layer 3 from external force.

The colored layer 5 is the outermost layer of the colored optical fiber core wire 1 and has a function of protecting the bare optical fiber 2, the primary layer 3 and the secondary layer 4 from external forces. The colored layer 5 is colored with a coloring agent mixed with a pigment, a lubricant, or the like for identifying the colored optical fiber 1 . Color types include, for example, white, black, gray, purple, blue, light blue, green, brown, yellow, orange, pink, and red.

FIG. 2A is a schematic diagram showing a part of the manufacturing apparatus 10 used in the manufacturing method of the colored optical fiber 1 according to this embodiment. In FIG. 2A, the manufacturing apparatus 10 includes a heating device 20, a primary layer coating device 30, a secondary layer coating device 40, guide rollers 45 and a first winding device 50. In FIG.

The optical fiber preform BM is made of, for example, silica-based glass, and is manufactured by a known method such as the VAD method, the OVD method, the MCVD method, or the like. The heating device 20 has a heater 21 . The heater 21 can be any heat source such as tape heaters, ribbon heaters, rubber heaters, oven heaters, ceramic heaters, halogen heaters. The end portion of the optical fiber preform BM is heated and melted by the heater 21 arranged around the optical fiber preform BM, and drawn to draw out the bare optical fiber 2 .

A primary layer coating device 30 is provided below the heating device 20 . The primary layer coating device 30 has a resin coating device 31 and an ultraviolet irradiation device 32 . The resin coating device 31 holds an ultraviolet curable resin (hereinafter referred to as “first ultraviolet curable resin”) that is a coating material for forming the primary layer 3 . A resin coating device 31 applies a first ultraviolet curable resin to the bare optical fiber 2 pulled out from the optical fiber preform BM.

An ultraviolet irradiation device 32 is provided below the resin coating device 31 . The ultraviolet irradiation device 32 includes any ultraviolet light source such as a metal halide lamp, a mercury lamp, or a UV-LED. A first ultraviolet curable resin is applied to the bare optical fiber 2 by a resin coating device 31, and the bare optical fiber 2 enters an ultraviolet irradiation device 32, where the first ultraviolet curable resin is irradiated with ultraviolet rays. As a result, the first ultraviolet curable resin is cured and the primary layer 3 is formed.

A secondary layer coating device 40 is provided below the primary layer coating device 30 . The secondary layer coating device 40 has a resin coating device 41 and an ultraviolet irradiation device 42 . The resin coating device 41 holds an ultraviolet curable resin (hereinafter referred to as “second ultraviolet curable resin”) that is a coating material for forming the secondary layer 4 . The primary layer 3 is coated with a second ultraviolet curable resin by a resin coating device 41 .

An ultraviolet irradiation device 42 is provided below the resin coating device 41 . The ultraviolet irradiation device 42 can be configured similarly to the ultraviolet irradiation device 32 . The bare optical fiber 2 with the second ultraviolet curable resin coated on the primary layer 3 enters the ultraviolet irradiation device 42, and the second ultraviolet curable resin is irradiated with ultraviolet rays. As a result, the second ultraviolet curable resin is cured and the secondary layer 4 is formed. The bare optical fiber 6 is formed by coating the bare optical fiber 2 with the primary layer 3 and the secondary layer 4 .

In addition, the resin coating device 31 may be configured to separately hold the first ultraviolet curable resin and the second ultraviolet curable resin. In this case, the resin coating device 31 applies the first ultraviolet curable resin to the bare optical fiber 2, and then applies the second ultraviolet curable resin on the first ultraviolet curable resin.

The ultraviolet irradiation device 32 irradiates the first ultraviolet curing resin and the second ultraviolet curing resin applied to the bare optical fiber 2 with ultraviolet rays. Thereby, the primary layer 3 and the secondary layer 4 are formed. In this case, the manufacturing apparatus 10 does not necessarily need to have the secondary layer coating apparatus 40 .

A guide roller 45 and a first winding device 50 are provided below the secondary layer coating device 40 . The manufactured optical fiber 6 is guided by the guide rollers 45 and wound by the first winding device 50 .

FIG. 2B is a schematic diagram showing another part of the manufacturing apparatus 10 used in the manufacturing method of the colored optical fiber 1 according to this embodiment. 2B, the manufacturing apparatus 10 has a strand holding device 55, a guide roller 56, a colored layer coating device 60, a guide roller 65 and a second winding device . The manufacturing device 10 manufactures the colored optical fiber core wire 1 from the optical fiber strands 6 manufactured by the plurality of devices shown in FIG. 2A.

The strand holding device 55 holds the manufactured optical fiber strand 6 in a wound state. 2B, the wire holding device 55 is a separate device from the first winding device 50, but the first winding device 50 may serve as the wire holding device 55 as well.

A colored layer coating device 60 is provided below the wire holding device 55 . The optical fiber strand 6 drawn out from the strand holding device 55 is guided by a guide roller 56 provided between the strand holding device 55 and the colored layer coating device 60, and conveyed into the colored layer coating device 60. be done.

The colored layer coating device 60 has a resin coating device 61 and an ultraviolet irradiation device 62 . The resin coating device 61 holds an ultraviolet curable resin (hereinafter referred to as “third ultraviolet curable resin”) that is a coating material for forming the colored layer 5 .

The optical fiber strand 6 is coated with a third UV-curing resin by a resin coating device 61 . An ultraviolet irradiation device 62 is provided below the resin coating device 61 . The ultraviolet irradiation device 62 can be configured similarly to the ultraviolet irradiation devices 32 and 42 .

The optical fiber wire 6 with the third ultraviolet curing resin applied to the outer periphery of the secondary layer 4 enters the ultraviolet irradiation device 62, and the third ultraviolet curing resin and the optical fiber wire 6 are irradiated with ultraviolet rays. Thereby, the third ultraviolet curable resin is cured and the colored layer 5 is formed.

By coating the bare optical fiber 2 with the primary layer 3 , the secondary layer 4 and the colored layer 5 , the colored optical fiber 1 is formed. The optical fiber colored core wire 1 after manufacture is guided by a guide roller 65 provided below the colored layer coating device 60 and wound up by the second winding device 70 .

FIG. 3 is a cross-sectional view of the optical fiber ribbon 100 according to this embodiment. The optical fiber ribbon 100 is configured by bundling n (n is a natural number of 2 or more) colored optical fiber core wires 1-1 to 1-n with an adhesive layer 101 interposed therebetween.

In this embodiment, the color of the colored layers 5 of the plurality of colored optical fibers 1-1 to 1-n are not all the same. That is, the same optical fiber ribbon 100 includes two or more types of optical fiber colored core wires 1 having colored layers 5 of different colors.

Moreover, it is preferable that the color of the colored layer 5 does not cause a difference in absorbance to ultraviolet rays. For example, when the colored optical fiber 1-1 has a white colored layer 5 and the colored optical fiber 1-n has a black colored layer 5, these two colored optical fibers Lines 1 may have different absorbances for UV light. As one of the solutions in this case, the third ultraviolet curable resin forming the colored layer 5 is added with an additive for adjusting the absorbance of ultraviolet rays of a predetermined wavelength according to the color of the colored layer 5 to be formed. A method of adding is conceivable. By appropriately adjusting the type and amount of the additive for each color of the colored layer 5, it is possible to reduce the difference in absorbance among the plurality of colored optical fibers 1-1 to 1-n.

At least part of the wavelength range (first wavelength range) in which the additive added to the third UV-curable resin absorbs UV rays is the photoinitiator added to the first UV-curable resin. preferably overlaps with the wavelength range (second wavelength range).

The adhesive layer 101 is formed by curing a coating material containing an ultraviolet curable resin by irradiating it with ultraviolet rays. The adhesive layer 101 is also referred to herein as a ribbon layer. The ultraviolet curable resin forming the adhesive layer 101 is composed of the same resin as the ultraviolet curable resin forming the primary layer 3 , the secondary layer 4 and the colored layer 5 . By taking the form of the optical fiber ribbon 100, the colored optical fiber core wires 1 can be bundled at a high density. Note that the optical fiber ribbon 100 is not limited to the configuration shown in FIG. It may also take the form of an optical fiber ribbon cable in which the optical fiber ribbon 100 is enclosed by a sheath.

FIG. 4 is a schematic diagram of a ribbon forming apparatus 80 used in the method for manufacturing the optical fiber ribbon 100 according to this embodiment. The ribbon forming device 80 has a resin coating device 81 and an ultraviolet irradiation device 82 . The resin coating device 81 holds an ultraviolet curable resin (hereinafter referred to as “fourth ultraviolet curable resin”) that is a coating material for the adhesive layer 101 .

A plurality of colored optical fiber core wires 1 prepared in different colors enter a ribbon forming device 80 and are coated with a fourth ultraviolet curable resin by a resin coating device 81 . The colored optical fiber cord 1 coated with the fourth ultraviolet curable resin is bundled together with a plurality of other colored optical fiber cords 1 coated with the fourth ultraviolet curable resin. The plurality of bundled colored optical fibers 1 are irradiated with ultraviolet rays by an ultraviolet irradiation device 82 provided in the ribbon forming device 80 . As a result, the fourth ultraviolet curable resin is cured and becomes the adhesive layer 101 . A plurality of colored optical fiber core wires 1 arranged in parallel are connected via an adhesive layer 101 . Thus, an optical fiber ribbon 100 is formed from a plurality of colored optical fiber core wires 1 .

Note that the ribbonization device 80 may be the ribbonization device disclosed in, for example, Japanese Patent Application Laid-Open No. 2012-118358. As a result, the adhesive layers 101 are intermittently formed at predetermined intervals in the longitudinal direction of the adjacent colored optical fibers 1, and the intermittent adhesive optical fiber ribbon 100 is formed.

FIG. 5 is a flow chart of a method for manufacturing the colored optical fiber 1 and the optical fiber ribbon 100 according to this embodiment. First, the user installs the optical fiber preform BM in the manufacturing apparatus 10 (step S101).

Next, the heater 21 provided in the heating device 20 heats the optical fiber preform BM to start drawing the bare optical fiber 2 (step S102).

The primary layer coating device 30 applies a first ultraviolet curable resin around the drawn optical fiber bare wire 2, irradiates the first ultraviolet curable resin with ultraviolet rays, and forms the primary layer 3 (step S103). .

Next, the secondary layer coating device 40 applies a second ultraviolet curable resin around the primary layer 3 and irradiates the second ultraviolet curable resin with ultraviolet rays to form the secondary layer 4 (step S104). Thereby, the optical fiber strand 6 is obtained. The manufactured optical fiber strand 6 is wound by the first winding device 50 .

Subsequently, when the colored layer coating device 60 pulls out the optical fiber strand 6 from the strand holding device 55 or the first winding device 50, the secondary layer 4 of the optical fiber strand 6 is coated with the third ultraviolet curable resin. is applied, and the colored layer 5 is formed by irradiating the third ultraviolet curable resin with ultraviolet rays (step S105). The colored optical fiber core wire 1 is obtained by coating the colored layer 5 around the optical fiber strand 6 . The manufactured colored optical fiber core wire 1 is wound by the second winding device 70 .

In this embodiment, a plurality of colored optical fiber core wires 1 having colored layers 5 of different colors are manufactured. Therefore, the process of step S105 is performed by changing the manufacturing conditions such as the composition of the third ultraviolet curable resin for each color.

Moreover, it is not always necessary to irradiate ultraviolet rays in the step of forming the primary layer 3 (step S103). In this case, the primary layer 3 can be cured in the step of forming the secondary layer 4 (step S104).

After the colored layer 5 is formed in step S105, the ribbon forming device 80 applies a fourth ultraviolet curable resin so as to cover the plurality of colored optical fiber core wires 1 prepared in different colors. are irradiated with ultraviolet rays to connect the plurality of colored optical fibers 1 (step S106). Thereby, the optical fiber ribbon 100 is manufactured.

According to this embodiment, when coloring the optical fiber 6 having a primary layer that is not sufficiently cured, the absorbance difference with respect to the wavelength of the UV light source for each color of the colored layer 5 is reduced. Specifically, among a plurality of colored optical fiber core wires 1 included in the same optical fiber ribbon 100, the difference in Young's modulus of the primary layer 3 between the colored optical fiber core wires 1 having different colors of the colored layers 5 is It is adjusted to be 0.1 MPa or less. As a result, even if the same optical fiber ribbon 100 includes a plurality of colored optical fibers 1 having different colors of the colored layers 5, the difference in microbending loss and the difference in strength between the plurality of colored optical fibers 1 can be reduced. can be made smaller.

Experimental results obtained when an experiment simulating the coloring process was conducted on the above-described optical fiber strand 6 will be described below.

In order to simulate the coloring process of the optical fiber when the optical fiber strand 6 is additionally irradiated with UV, a colored layer 5 is formed on quartz glass that does not have absorption characteristics for the UV light used. A third UV curable resin was applied to a film thickness of 6 μm±2 μm to cover the optical fiber 6 . Additives were added to the third UV curable resin forming the colored layer 5 . The third UV curable resin constituting the colored layer 5 is composed of oligomers, monomers, etc., and contains additives such as photoinitiators, photosensitizers, UV absorbers, antioxidants and pigments. But it's okay.

Table 1 shows the Young's modulus (MPa), the maximum Young's modulus (MPa), the Young's modulus increase, and the ultraviolet curing type forming the colored layer 5 of the primary layer 3 of the fibers used in Examples 1 to 8 and Comparative Examples 1 to 3. Color of resin, presence or absence and type of additive, absorbance for ultraviolet rays with a wavelength of 365 nm, Young's modulus (MPa) after additional UV irradiation, amount of increase in Young's modulus, difference from Young's modulus when color of colored layer 5 is white represents.

"Maximum Young's modulus" in Table 1 is the maximum Young's modulus that the primary layer 3 of the optical fiber strand 6 can exhibit. In addition, the “Young's modulus” in Table 1 is the ISM (In Situ Modulus) of the primary layer 3 of the colored optical fiber 1 . ISM is defined as measured by the following method.

First, using a commercially available stripper, the primary layer 3 and the secondary layer 4 in the middle portion of the sample optical fiber were stripped by a length of several millimeters, and then one end of the optical fiber with the coating layer formed thereon was adhered. A load F is applied to the other end of the optical fiber on which the coating layer is formed while the optical fiber is fixed on the slide glass with an agent. In this state, the displacement .delta. of the primary layer 3 at the boundary between the portion where the coating layer is peeled off and the portion where the coating layer is formed is read with a microscope. Then, a graph of displacement δ versus load F is created by setting the load F to 10, 20, 30, 50 and 70 gf (that is, 98, 196, 294, 490 and 686 mN sequentially). Then, the gradient obtained from the graph and the following equation (1) are used to calculate the primary elastic modulus. Since the calculated primary elastic modulus corresponds to the so-called ISM, it is hereinafter appropriately referred to as P-ISM. When the colored optical fiber 1 was drawn, the drawing speed and the illuminance of the ultraviolet rays were controlled in order to adjust the P-ISM.
P-ISM=(3F/δ)*(1/2πl)*ln(DP/DG) (1)

Here, the unit of P-ISM is [MPa]. Further, F/δ is the slope indicated by the graph of displacement (δ) [μm] against load (F) [gf], l is the sample length (for example, 10 mm), and DP/DG is the outer diameter (DP) of the primary layer 3 [ μm] and the outer diameter (DG) [μm] of the clad portion of the optical fiber. Therefore, when calculating P-ISM using the above formula from the used F, δ, and l, it is necessary to perform a predetermined unit conversion. The outer diameter of the primary layer 3 and the outer diameter of the clad portion can be measured by observing the cross section of the optical fiber cut by the fiber cutter with a microscope.

Various methods are conceivable for measuring the microbend loss. In this specification, an optical fiber with a length of 400 m or longer is wound in a single layer on a large bobbin wrapped with #1000 sandpaper under a tension of 100 gf so as not to overlap each other. Micro bend loss defined as a value. Here, the transmission loss of the optical fiber in state B does not include the microbend loss, and is considered to be the transmission loss inherent in the optical fiber itself.

This measuring method is similar to the fixed diameter drum method defined in JIS C6823:2010. This measurement method is also called a sandpaper method. In this measurement method, the transmission loss is measured at a wavelength of 1550 nm, so the microbend loss below is also the value at the wavelength of 1550 nm.

An effective core cross-sectional area (effective core cross-sectional area) Aeff can be used as an index representing the likelihood of occurrence of microbend loss in an optical fiber. The effective core cross-sectional area is represented by the following equation (2).
Aeff=(πk/4)*(MFD) ² (2)
Here, the effective core area Aeff is a value at a wavelength of 1550 nm, MFD is a mode field diameter (μm), and k is a constant. The effective core cross-sectional area Aeff represents the area of the portion of the cross section orthogonal to the axis of the bare optical fiber 2 through which light having a predetermined intensity passes. In general, the larger the effective core area Aeff of the bare optical fiber 2 is, the weaker the optical confinement in the cross section of the bare optical fiber 2 is. That is, when the effective core area Aeff of the bare optical fiber 2 is large, the light in the bare optical fiber 2 tends to leak due to the external force applied to the bare optical fiber 2 . Therefore, when the effective core area Aeff of the bare optical fiber 2 increases, the colored optical fiber 1 tends to suffer micro-bend loss.

In each example and comparative example, an optical fiber having an effective core area Aeff of 80 μm ² or more is used as the optical fiber. In an optical fiber, the effective core area Aeff is an index of microbend sensitivity, and the larger the effective core area Aeff, the higher the microbend sensitivity. In general, it is said that if the effective core area Aeff exceeds 100 μm ² , the microbend sensitivity is high. Therefore, when the effective core area Aeff is 130 μm ² or more and 150 μm ² or less, an optical fiber with high microbend sensitivity can be obtained.

The absorbance in each example and comparative example was determined as follows. A third UV curable resin forming a colored layer was applied on quartz glass to a film thickness of 6 μm±2 μm, and the absorbance of the coated quartz glass was measured using a spectrophotometer (PerkinElmer, Lambda 900). However, the absorbance of the third ultraviolet curable resin forming the colored layer 5 was obtained by subtracting the previously measured absorbance of the silica glass alone from the absorbance of the coated silica glass. The absorbance A in each example and comparative example is represented by the following formula (3).
A=-log(I/I0)=-log(T/100)=εcl (3)
T is the transmittance, I is the transmitted light intensity, I0 is the incident light intensity, A is the absorbance, ε is the molecular extinction coefficient, c is the concentration of the absorbing substance, and l is the distance of the medium through which the light is transmitted.

The "Young's modulus after additional UV irradiation" in Table 1 is obtained by using a UV-LED that irradiates ultraviolet rays with a wavelength of 365 nm ± 20 nm to the optical fiber 6 at an illuminance of 1500 mW/cm ² and an irradiation dose of 500 mJ/cm ² . Defined as P-ISM upon re-irradiation.

In the optical fiber bare wire 6 used in each example and comparative example, first, a first ultraviolet curable resin is applied around the drawn optical fiber bare wire 2, and the first ultraviolet curable resin is irradiated with ultraviolet rays. and the primary layer 3 was formed.

Next, the secondary layer 4 was formed by applying a second UV-curable resin around the primary layer 3 and irradiating the second UV-curable resin with UV rays. In addition, it is not always necessary to irradiate ultraviolet rays in the step of forming the primary layer 3 . In this case, the primary layer 3 can be cured by UV irradiation in the step of forming the secondary layer 4 .

When the optical fiber strand 6 was drawn, the drawing speed and illumination were controlled in order to adjust the Young's modulus of the P-ISM or the secondary layer 4 . 2,4,6-trimethylbenzoyl-diphenylphosphine oxide was used as a photoinitiator for the primary layer 3 of the colored optical fiber 1 . This photoinitiator reduces the absorbance around 340-410 nm when used in the reaction by UV irradiation.

The absorption wavelength of the photoinitiator contained in the primary layer 3 can be detected by comparing the absorbance before and after UV irradiation and confirming the change in absorbance. Of course, even if it is not this method, it is easy to judge whether the absorption wavelength is derived from the photoinitiator. For example, as an example, it is possible to determine the absorption wavelength of the photoinitiator added to the primary layer 3 by comparing it with the absorption wavelength of photoinitiators on the market.

The diameter of the bare optical fiber 2 may be 80 μm or more and 150 μm or less, preferably 124 μm or more and 126 μm or less. The thickness of the primary layer 3 can be 5 μm or more and 60 μm or less. The thickness of the secondary layer 4 may be ≧5 μm and ≦60 μm. Moreover, the thickness of the colored layer 5 can be about several μm.

In each of the examples and comparative examples, various Young's moduli and maximum Young's moduli of the fibers used can be obtained by controlling the manufacturing conditions (linear velocity and illuminance) and selecting the first ultraviolet curable resin forming the primary layer 3. adjusted to be Moreover, the Young's modulus of the secondary layer 4 is 800 to 1000 MPa.

In Examples 1, 4 and 7, 1.0 wt% of 2,2',4,4'-tetrahydroxybenzophenone was added as additive A. bottom. In Examples 2, 5 and 8, TiO ₂ (Ishibashi Sangyo Co., Ltd./CR-60-2) was added as additive B at 10.0 wt %. Addition of these additives to the ultraviolet curable resin forming the colored layer increases the absorbance of ultraviolet rays in a predetermined wavelength range.

In Example 1, an optical fiber strand 6 having a Young's modulus of 0.15 MPa and a maximum Young's modulus of 1.15 MPa was used. When the optical fiber strand 6 is covered with the third ultraviolet curable resin forming the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 1a), the Young's The modulus was 0.82 MPa. On the other hand, when the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the black colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm by adding the additive A (Example 1b ), the Young's modulus after additional UV irradiation was 0.81 MPa, and the difference from white was 0.01 MPa.

In Example 2, an optical fiber strand 6 having a Young's modulus of 0.15 MPa and a maximum Young's modulus of 1.15 MPa was used. When the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 2a), the Young's The modulus was 0.82 MPa. On the other hand, when the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the black colored layer 5 having the absorbance of 0.55 for ultraviolet rays with a wavelength of 365 nm by adding the additive B (Example 2b ), the Young's modulus after additional UV irradiation was 0.89 MPa, and the difference from white was 0.07 MPa.

In Example 3, an optical fiber strand having a Young's modulus of 0.37 MPa and a maximum Young's modulus of 0.40 MPa was used. When the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 3a), the Young's The modulus was 0.38 MPa. On the other hand, when the optical fiber is covered with an ultraviolet curable resin that forms a black colored layer having an absorbance of 0.25 for ultraviolet rays with a wavelength of 365 nm (Example 3b), the Young's modulus after additional UV irradiation was 0.39 MPa, and the difference from white was 0.01 MPa.

In Example 4, an optical fiber strand having a Young's modulus of 0.39 MPa and a maximum Young's modulus of 0.73 MPa was used. When the optical fiber 6 is covered with the third ultraviolet curable resin that forms the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 4a), the Young's The modulus was 0.58 MPa. On the other hand, when additive A is added to form a black colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm, the optical fiber strand 6 is covered with a third ultraviolet curable resin (Example 4b ), the Young's modulus after additional UV irradiation was 0.62 MPa, and the difference from white was 0.04 MPa.

In Example 5, an optical fiber strand having a Young's modulus of 0.39 MPa and a maximum Young's modulus of 0.73 MPa was used. When the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 5a), the Young's The modulus was 0.58 MPa. On the other hand, when the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the black colored layer 5 having the absorbance of 0.55 for ultraviolet rays with a wavelength of 365 nm by adding the additive B (Example 5b ), the Young's modulus after additional UV irradiation was 0.63 MPa, and the difference from white was 0.05 MPa.

In Example 6, an optical fiber strand having a Young's modulus of 0.43 MPa and a maximum Young's modulus of 0.56 MPa was used. When the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 6a), the Young's The rate was 0.51 MPa. On the other hand, when the optical fiber strand 6 is covered with the third ultraviolet curable resin forming the black colored layer 5 having an absorbance of 0.25 for ultraviolet rays with a wavelength of 365 nm (Example 6b), additional UV irradiation The later Young's modulus was 0.55 MPa and the difference from white was 0.04 MPa.

In Example 7, an optical fiber strand having a Young's modulus of 0.54 MPa and a maximum Young's modulus of 0.76 MPa was used. When the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 7a), the Young's The modulus was 0.63 MPa. On the other hand, when the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the black colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm by adding the additive A (Example 7b ), the Young's modulus after additional UV irradiation was 0.63 MPa, and the difference from white was 0.00 MPa.

In Example 8, an optical fiber strand having a Young's modulus of 0.54 MPa and a maximum Young's modulus of 0.76 MPa was used. When the optical fiber strand is covered with the third UV-curable resin forming a white colored layer having an absorbance of 0.66 for UV light with a wavelength of 365 nm (Example 8a), the Young's modulus after additional UV irradiation is It was 0.63 MPa. On the other hand, when the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the black colored layer 5 having the absorbance of 0.55 for ultraviolet rays with a wavelength of 365 nm by adding the additive B (Example 8b ), the Young's modulus after additional UV irradiation was 0.67 MPa, and the difference from white was 0.04 MPa.

In Comparative Example 1, an optical fiber strand 6 having a Young's modulus of 0.15 MPa and a maximum Young's modulus of 1.15 MPa was used. When the optical fiber strand 6 is covered with the third ultraviolet curable resin forming the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Comparative Example 1a), the Young's The modulus was 0.82 MPa. On the other hand, when the optical fiber strand was covered with the third UV-curable resin forming the black colored layer 5 having an absorbance of 0.25 for UV light with a wavelength of 365 nm (Comparative Example 1b), after the additional UV irradiation The Young's modulus of was 1.04 MPa. The difference between white and black was 0.22 MPa, which was 0.1 MPa or more.

In Comparative Example 2, an optical fiber strand 6 having a Young's modulus of 0.39 MPa and a maximum Young's modulus of 0.73 MPa was used. When the optical fiber strand 6 was covered with the third ultraviolet curable resin forming the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Comparative Example 2a), Young The modulus was 0.58 MPa. On the other hand, when the optical fiber strand 6 is covered with the third UV-curable resin forming the black colored layer 5 having an absorbance of 0.25 for UV light with a wavelength of 365 nm (Comparative Example 2b), additional UV irradiation The subsequent Young's modulus was 0.71 MPa. The difference between white and black was 0.13 MPa, which was 0.1 MPa or more.

In Comparative Example 3, an optical fiber strand 6 having a Young's modulus of 0.54 MPa and a maximum Young's modulus of 0.76 MPa was used. When the optical fiber strand 6 is covered with the third ultraviolet curable resin that forms the white colored layer 5 having an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Comparative Example 3a), the Young's The modulus was 0.63 MPa. On the other hand, when the optical fiber strand was covered with the third UV-curable resin forming the black colored layer 5 having an absorbance of 0.25 for UV light with a wavelength of 365 nm (Comparative Example 3b), after the additional UV irradiation The Young's modulus of was 0.74 MPa. The difference between white and black was 0.11 MPa, which was 0.1 MPa or more.

In the above-described examples and comparative examples, the case where the color of the colored layer is white and black was taken up, but the present invention can be similarly applied to any combination of colors having different absorbances in the UV region to be used. obtain. Color types include, for example, white, black, gray, purple, blue, light blue, green, brown, yellow, orange, pink, and red.

In addition, in each example and comparative example, the Young's modulus after additional UV irradiation was 1500 mW/cm ² with a UV-LED with an irradiation wavelength of 365 nm ± 20 nm and 500 mJ/cm ² with respect to the optical fiber strand 6. was defined as P-ISM when re-irradiated, but the UV light source is not limited to UV-LEDs with a wavelength of 365 nm ± 20 nm. For example, UV-LEDs with different wavelengths such as UV-LEDs with a wavelength of 385 nm ± 20 nm and UV-LEDs with a wavelength of 395 nm ± 20 nm, and in addition to UV-LEDs, those that emit UV light such as metal halide lamps and mercury lamps. , the same effect can be produced when an additive having an absorption region in that range is used. Also, the same effect can be produced even if irradiation is performed under other conditions regarding the illuminance/irradiation amount.

In addition, the additives used in Examples 1, 2, 4, 5 and 7 are only examples, and are not limited to UV absorbers and pigments. Additives such as agents and photosensitizers may be used. In addition to additives A and B, for example, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2-isopropylthioxanthone ), 2,2-dihydroxy-4,4-dimethoxybenzophenone, 2,4,6-tris[4-(hexyloxy)-2-hydroxy-3-methyl Phenyl]-1,3,5-triazine (2,4,6-Tris[4-(hexyloxy)-2-hydroxy-3-methylphenyl]-1,3,5-triazine), 2-(2-hydroxy- Compounds such as 5-methylphenyl)benzotriazole (2-(2-Hydroxy-5-methylphenyl)benzotriazole) can also be additives.

It is also clear that the type of effective additive differs depending on the absorption wavelength of the photoinitiator used in the primary layer 3 . Therefore, it is important to add an additive having an absorption wavelength range even partially in the same absorption wavelength range as the photoinitiator used.

The Young's modulus of the primary layer 3 shown in each example and comparative example is merely an example, and is not limited to this. For example, the Young's modulus of the primary layer 3 can range from 0.1 to 2.0 MPa. The Young's modulus of the secondary layer can range, for example, from 500 to 2000 MPa.

In addition, 19 types of optical fiber colored core wires 1 whose secondary layer 4 has a Young's modulus of about 1000 MPa and whose primary layer 3 has a different Young's modulus are selected at random. Calculate the difference.

FIG. 6 is a graph showing the relationship between the difference in Young's modulus of the primary layer 3 of the colored optical fiber 1 according to the example and the rate at which the microbend loss difference is 0.05 dB/km or more. As shown in FIG. 6, when calculating the ratio of the micro bend loss difference of 0.05 dB / km or more for each range of Young's modulus difference of 0.05 MPa, the micro bend loss It was confirmed that the ratio of the difference of 0.05 dB/km or more increased sharply. From this, it was found that the difference in Young's modulus of the primary layer 3 for each colored optical fiber 1 used in the same optical fiber ribbon 100 is preferably 0.1 MPa or less. This coincided with the results of Examples 1 to 8 described above.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, examples in which a part of the configuration of any one embodiment is added to another embodiment, and examples in which a part of the configuration of another embodiment is replaced are also embodiments of the present invention. In addition, well-known techniques and known techniques in the relevant technical field can be appropriately applied to parts that are not particularly described or illustrated in the embodiments.

1 optical fiber colored core wire 2 optical fiber bare wire 3 primary layer 4 secondary layer 5 colored layer 6 optical fiber bare wire 100 optical fiber ribbon 101 adhesive layer

Claims (12)

An optical fiber bare wire, a primary layer formed of a first ultraviolet curable resin covering the optical fiber bare wire, a secondary layer formed of a second ultraviolet curable resin covering the primary layer, and the secondary layer a plurality of colored optical fiber core wires each having a colored layer formed of a third ultraviolet curable resin for covering;
an adhesive layer formed of a fourth ultraviolet curable resin covering the plurality of colored optical fibers and connecting the plurality of colored optical fibers;
An optical fiber ribbon comprising:
Young's modulus of the primary layer is lower than the maximum Young's modulus of the first ultraviolet curable resin,
Among the plurality of colored optical fiber core wires, the difference in the Young's modulus of the primary layer between the optical fiber colored core wires having different colors of the colored layers is 0.1 MPa or less.
An optical fiber ribbon characterized by: The Young's modulus of the primary layer is 0.15 MPa or more and 0.89 MPa or less.
The optical fiber ribbon according to claim 1, characterized in that: The difference in absorbance for ultraviolet rays between the third ultraviolet curable resins forming the colored layers of different colors is 0.11 or less in at least part of the wavelength range of 350 nm to 410 nm.
The optical fiber ribbon according to claim 1 or 2, characterized in that: An additive that changes the absorbance is added to the third ultraviolet curable resin,
4. The optical fiber ribbon of claim 3, wherein: At least part of the first wavelength range of the ultraviolet rays absorbed by the additive overlaps with a second wavelength range of the ultraviolet rays absorbed by the photoinitiator added to the first ultraviolet-curable resin,
5. The optical fiber ribbon of claim 4, wherein: drawing a bare optical fiber from an optical fiber preform;
applying a first UV curable resin around the bare optical fiber to form a primary layer;
a step of applying a second ultraviolet curable resin around the primary layer and irradiating the second ultraviolet curable resin with ultraviolet rays to form a secondary layer, thereby manufacturing an optical fiber strand;
a step of applying a third ultraviolet curable resin around the optical fiber strand and irradiating the third ultraviolet curable resin with the ultraviolet rays to form a colored layer, thereby manufacturing a colored optical fiber core wire; ,
By applying a fourth ultraviolet curable resin around the plurality of colored optical fiber core wires and irradiating the fourth ultraviolet curable resin with the ultraviolet rays to form an adhesive layer, a plurality of the colored optical fiber cores are formed. a step of manufacturing an optical fiber ribbon with connected wires;
with
Young's modulus of the primary layer is lower than the maximum Young's modulus of the first ultraviolet curable resin,
Among the plurality of colored optical fiber core wires, the difference in the Young's modulus of the primary layer between the optical fiber colored core wires having different colors of the colored layers is 0.1 MPa or less.
A method for manufacturing an optical fiber ribbon, characterized by: A difference between the Young's modulus of the primary layer and the maximum Young's modulus of the optical fiber is greater than 0.13 MPa,
7. The method for manufacturing an optical fiber ribbon according to claim 6, wherein: The Young's modulus of the primary layer is 0.15 MPa or more and 0.89 MPa or less.
The method for manufacturing an optical fiber ribbon according to claim 6 or 7, characterized in that: The difference in absorbance with respect to the ultraviolet rays between the third ultraviolet curable resins forming the colored layers of different colors is 0.11 or less in at least part of the wavelength range of 350 nm to 410 nm.
The method for manufacturing an optical fiber ribbon according to any one of claims 6 to 8, characterized in that: An additive that changes the absorbance is added to the third ultraviolet curable resin,
The method for manufacturing an optical fiber ribbon according to claim 9, characterized in that: At least part of the first wavelength range of the ultraviolet rays absorbed by the additive overlaps with a second wavelength range of the ultraviolet rays absorbed by the photoinitiator added to the first ultraviolet-curable resin,
11. The method for manufacturing an optical fiber ribbon according to claim 10, wherein: irradiating the first ultraviolet curable resin and the second ultraviolet curable resin with the ultraviolet rays in the step of manufacturing the optical fiber strand;
The method for manufacturing an optical fiber ribbon according to any one of claims 6 to 11, characterized in that:

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