JP7704693B2 - Optical fiber ribbon and method for manufacturing the same - Google Patents

Description

The present invention relates to an optical fiber ribbon and a method for manufacturing an optical fiber ribbon.

A technology is known for manufacturing colored optical fiber by forming a primary layer covering a bare optical fiber, a secondary layer covering the primary layer, and a colored layer covering the secondary layer from ultraviolet-curable resin so as to have the desired Young's modulus (Patent Documents 1 and 2).
When the Young's modulus of the primary layer is set low, it is possible to buffer the external force applied to the bare optical fiber and suppress the optical transmission loss due to minute deformation of the bare optical fiber (hereinafter referred to as "microbend loss"). Conversely, when the Young's modulus of the secondary layer is set high, it is possible to protect the bare optical fiber and the primary layer from external forces.
In addition, the optical fiber ribbon is manufactured by covering a plurality of colored optical fiber cores with an ultraviolet-curable resin and connecting the plurality of colored optical fiber cores to each other by irradiating ultraviolet (UV) rays. Even if the Young's modulus of the primary layer is low in the colored optical fiber cores before the manufacturing process of the optical fiber ribbon, the Young's modulus of the primary layer increases when irradiated with UV rays in the manufacturing process of the optical fiber ribbon, which causes microbend loss.
In response to this, a method for manufacturing an optical fiber ribbon in which the primary layer has a Young's modulus close to the saturated Young's modulus has been proposed (Patent Document 3), and a method for preventing an unintended increase in Young's modulus due to UV exposure in later processes by adding an ultraviolet absorber to the primary layer has been proposed (Patent Document 4).

JP 2005-162522 A Special Publication No. 2002-524581 International Publication No. 2018/062364 Special table 2019-505648 publication

In recent years, the use of optical fiber strands with insufficient primary layer curing has become common in optical fiber manufacturing due to factors such as the shift to LED UV light sources and increased drawing speeds. In order to fully cure the primary layer, significant restrictions are placed on the manufacturing conditions, such as increasing the number of UV light sources, so it is important to find a way to effectively use optical fiber strands with insufficient primary layer curing.

However, if UV irradiation is performed in a post-process on an optical fiber strand with an insufficiently cured primary layer, the Young's modulus of the primary layer increases. In addition, depending on the combination of the UV-curable resin used in the coloring layer and the wavelength of the UV light irradiated by the UV light source, the absorbance of the UV light source varies for each color of the coloring layer, so that a difference may occur in the amount of UV irradiation that penetrates the coloring layer and reaches the inner primary layer in the coloring process, which is one of the post-processes. For example, when the coloring layer is cured using a UV-LED that irradiates UV light with a wavelength of 365 nm, if the absorbance of the UV-curable resin used in the coloring layer with UV light with a wavelength of 365 nm varies greatly depending on the color, a difference may occur in the amount of UV light absorbed in the coloring layer. In other words, the degree of increase in the Young's modulus of the primary layer may differ depending on the color of the coloring layer. As a result, when an optical fiber ribbon is manufactured using multiple colored optical fiber cores with different colored colored layers, colored optical fiber cores with significantly different Young's moduli of the primary layer may be mixed in the same optical fiber ribbon. Generally, as the Young's modulus of the primary layer increases, the microbend loss worsens, so it is conceivable that the microbend loss will vary for each colored optical fiber core that makes up the same optical fiber ribbon. If differences in microbend loss occur between the colored optical fiber cores contained in the same optical fiber ribbon, it will become difficult to indicate the ribbon specifications and manage the ribbon when it is in use. Furthermore, if the Young's modulus of the primary layer of the colored optical fiber cores contained in the same optical fiber ribbon differs, it is conceivable that differences in strength will occur for each colored optical fiber core.

On the other hand, in the manufacturing method described in Patent Document 3, since it is necessary to cure with a Young's modulus close to the saturated Young's modulus, it is not assumed that the primary layer will not be sufficiently cured due to, for example, changing the UV light source to an LED or increasing the drawing speed. Therefore, if the absorbance of the UV light source differs depending on the color used in the colored layer, the Young's modulus of the primary layer may differ due to UV irradiation during the coloring process. In addition, in the manufacturing method described in Patent Document 4, since it is necessary to minimize the spectral overlap of the photoinitiator and the UV absorber, there are considerable restrictions on the options for the resin composition of the colored optical fiber core.

The present invention has been made in consideration of the above-mentioned problems, and aims to provide an optical fiber ribbon and a method for manufacturing the optical fiber ribbon that reduce the difference in microbend loss and strength between multiple optical fiber colored cores having different colored layers.

According to one aspect of the present invention, there is provided an optical fiber ribbon comprising: a bare optical fiber; a plurality of colored optical fiber core wires, each of which has a primary layer formed of a first ultraviolet-curable resin covering the bare optical fiber, a secondary layer formed of a second ultraviolet-curable resin covering the primary layer, and a colored layer formed of a third ultraviolet-curable resin covering the secondary layer; and an adhesive layer formed of a fourth ultraviolet-curable resin covering the plurality of colored optical fiber core wires and connecting the plurality of colored optical fiber core wires, 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 difference in the Young's modulus of the primary layer between the colored optical fiber core wires having different colored layers among the plurality of colored optical fiber core wires is 0.1 MPa or less.

According to another aspect of the present invention, there is provided a method for producing an optical fiber ribbon, comprising the steps of: drawing a bare optical fiber from an optical fiber preform; applying a first ultraviolet-curing resin around the bare optical fiber to form a primary layer; applying a second ultraviolet-curing resin around the primary layer and irradiating the second ultraviolet-curing resin with ultraviolet light to form a secondary layer, thereby producing an optical fiber strand; applying a third ultraviolet-curing resin around the bare optical fiber and irradiating the third ultraviolet-curing resin with ultraviolet light to form a colored layer, thereby producing an optical fiber ribbon; applying a fourth ultraviolet-curing resin around a plurality of the colored optical fiber strands and irradiating the fourth ultraviolet-curing resin with ultraviolet light to form an adhesive layer, thereby producing an optical fiber ribbon in which a plurality of the colored optical fiber strands are connected, wherein the Young's modulus of the primary layer is lower than the maximum Young's modulus of the first ultraviolet-curing resin, and the difference in the Young's modulus of the primary layer between the colored optical fiber strands having different colored layers among the plurality of colored optical fiber strands is 0.1 MPa or less.

The present invention provides an optical fiber ribbon and a method for manufacturing the optical fiber ribbon that reduce the microbend loss and strength difference between multiple optical fiber colored cores having different colored layers.

1 is a cross-sectional view of a colored optical fiber core according to an embodiment of the present invention. 1 is a cross-sectional view of an optical fiber according to an embodiment. 1 is a schematic diagram showing a part of a manufacturing apparatus used in a method for manufacturing a colored optical fiber according to an embodiment of the present invention. 4 is a schematic diagram showing another part of the manufacturing apparatus used in the method for manufacturing a colored optical fiber according to the first embodiment. FIG. 1 is a cross-sectional view of an optical fiber ribbon according to one embodiment. 1 is a schematic diagram of a ribbon forming apparatus used in an optical fiber ribbon manufacturing method according to one embodiment. FIG. 1 is a flowchart of a method for manufacturing a colored optical fiber and an optical fiber ribbon according to an embodiment. 1 is a graph showing the relationship between the Young's modulus difference of the primary layer of the optical fiber colored core wire according to the embodiment and the proportion of the microbend loss difference of 0.05 dB/km or more.

Embodiments of the present invention will be described in detail below with reference to the drawings. Elements having common functions throughout the drawings will be given the same reference numerals, and duplicate descriptions may be omitted or simplified.

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

The bare optical fiber 2 is made of, for example, quartz glass, and transmits light. The primary layer 3, secondary layer 4, and colored layer 5 are each formed by curing an ultraviolet-curable resin by irradiating it with ultraviolet light. There are no particular limitations on the ultraviolet-curable resin, so long as it can be polymerized by irradiating it with ultraviolet light. The ultraviolet-curable resin can be polymerized, for example, by photoradical polymerization.

The ultraviolet-curable resin is, for example, an ultraviolet-curable resin having a polymerizable unsaturated group such as an ethylenically unsaturated group that polymerizes and hardens when exposed to ultraviolet light, such as urethane (meth)acrylates, such as polyether-based urethane (meth)acrylates and polyester-based urethane (meth)acrylates, epoxy (meth)acrylates, and polyester (meth)acrylates, and preferably has at least two polymerizable unsaturated groups.

Examples of polymerizable unsaturated groups in ultraviolet-curable resins include groups with unsaturated double bonds, such as vinyl groups, allyl groups, acryloyl groups, and methacryloyl groups, and groups with unsaturated triple bonds, such as propargyl groups. Among these, acryloyl groups and methacryloyl groups are preferred in terms of polymerizability.

The UV-curable resin may be a monomer, oligomer, or polymer that initiates polymerization and hardens when irradiated with UV light, but is preferably an oligomer. An oligomer is a polymer with a degree of polymerization of 2 to 100. 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") that has sensitivity in the UV region.

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

Furthermore, the UV-curable resin may contain, in addition to the oligomer and photoinitiator, for example, a diluent monomer, a photosensitizer, a chain transfer agent, and various additives. As the diluent monomer, a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate is used. Here, the diluent monomer means a monomer for diluting the UV-curable resin.

The primary layer 3 is a soft layer and has the function of cushioning the external force applied to the bare optical fiber 2. When the optical fiber strand 6 is formed, there may still be room for hardening in the primary layer 3, but when it has hardened to the point where there is no room for hardening, the Young's modulus of the primary layer 3 is at its 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 the "maximum Young's modulus."

Ultraviolet rays are irradiated at an appropriate illuminance and dose using, for example, a mercury lamp or UV-LED. The maximum Young's modulus varies with the optical fiber manufacturing conditions (e.g., line speed, UV irradiation intensity, type of UV light source, resin application temperature, etc.) and cannot be determined uniquely by the ultraviolet-curable resin used. In the optical fiber strand 6, optical fiber colored core 1, and optical fiber ribbon 100 of this embodiment, the Young's modulus of the primary layer 3 is lower than the maximum Young's modulus of the ultraviolet-curable resin that forms 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 the function of protecting the bare optical fiber 2 and the primary layer 3 from external forces.

The colored layer 5 is the outermost layer of the colored optical fiber core 1, and has the 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 containing a pigment, a lubricant, etc., to identify the colored optical fiber core 1. Examples of colors include white, black, gray, purple, blue, light blue, green, brown, yellow, orange, pink, and red.

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

The optical fiber preform BM is made of, for example, quartz-based glass, and is manufactured by a known method such as the VAD method, the OVD method, or the MCVD method. The heating device 20 has a heater 21. The heater 21 can be any heat source such as a tape heater, a ribbon heater, a rubber heater, an oven heater, a ceramic heater, or a halogen heater. The end of the optical fiber preform BM is heated and melted by the heater 21 arranged around the optical fiber preform BM, and is drawn to extract 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 applicator 31 and an ultraviolet ray irradiation device 32. The resin applicator 31 holds an ultraviolet ray curing resin (hereinafter referred to as "first ultraviolet ray curing resin"), which is a coating material for forming the primary layer 3. The resin applicator 31 applies the first ultraviolet ray curing resin to the bare optical fiber 2 drawn out from the optical fiber preform BM.

An ultraviolet ray irradiation device 32 is provided below the resin application device 31. The ultraviolet ray irradiation device 32 is equipped with any ultraviolet ray light source such as a metal halide lamp, a mercury lamp, or a UV-LED. A first ultraviolet ray curing resin is applied to the bare optical fiber 2 by the resin application device 31, and the bare optical fiber 2 enters the ultraviolet ray irradiation device 32, where ultraviolet rays are irradiated onto the first ultraviolet ray curing resin. As a result, the first ultraviolet ray curing 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 ray irradiation device 42. The resin coating device 41 holds an ultraviolet ray curing resin (hereinafter referred to as "second ultraviolet ray curing resin"), which is a coating material for forming the secondary layer 4. The second ultraviolet ray curing resin is applied to the primary layer 3 by the resin coating device 41.

An ultraviolet irradiation device 42 is provided below the resin application device 41. The ultraviolet irradiation device 42 may be configured in the same manner as 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 light. As a result, the second ultraviolet-curable resin is cured and the secondary layer 4 is formed. The primary layer 3 and the secondary layer 4 are coated on the bare optical fiber 2, forming the optical fiber strand 6.

The resin applicator 31 may be configured to hold the first UV-curable resin and the second UV-curable resin separately. In this case, the resin applicator 31 applies the first UV-curable resin to the bare optical fiber 2, and then applies the second UV-curable resin on top of the first UV-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 light. This forms the primary layer 3 and the secondary layer 4. In this case, the manufacturing device 10 does not necessarily need to have the secondary layer coating device 40.

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

Figure 2B is a schematic diagram showing other parts of the manufacturing apparatus 10 used in the manufacturing method of the colored optical fiber core wire 1 according to this embodiment. In Figure 2B, the manufacturing apparatus 10 has a bare wire holding device 55, a guide roller 56, a colored layer coating device 60, a guide roller 65, and a second winding device 70. The manufacturing apparatus 10 manufactures the colored optical fiber core wire 1 from the optical fiber bare wire 6 manufactured by the multiple devices shown in Figure 2A.

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

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

The colored layer coating device 60 has a resin coating device 61 and an ultraviolet ray irradiation device 62. The resin coating device 61 holds an ultraviolet ray curing resin (hereinafter referred to as the "third ultraviolet ray curing resin"), which is a coating material for forming the colored layer 5.

A third ultraviolet-curing resin is applied to the optical fiber strand 6 by a resin applicator 61. An ultraviolet irradiator 62 is provided below the resin applicator 61. The ultraviolet irradiator 62 may be configured in the same manner as the ultraviolet irradiators 32 and 42.

The optical fiber strand 6 with the third ultraviolet-curable resin applied to the outer periphery of the secondary layer 4 enters the ultraviolet irradiation device 62, which irradiates the third ultraviolet-curable resin and the optical fiber strand 6 with ultraviolet light. This hardens the third ultraviolet-curable resin, and forms the colored layer 5.

The primary layer 3, secondary layer 4, and colored layer 5 are applied to the bare optical fiber 2 to form the colored optical fiber core 1. After manufacture, the colored optical fiber core 1 is guided by a guide roller 65 provided below the colored layer application device 60, and wound up on the second winding device 70.

Figure 3 is a cross-sectional view of an optical fiber ribbon 100 according to this embodiment. The optical fiber ribbon 100 is formed by bundling n (n is a natural number of 2 or more) optical fiber colored core wires 1-1 to 1-n into a band via an adhesive layer 101.

In addition, in this embodiment, the colored layers 5 of the multiple colored optical fiber cores 1-1 to 1-n are not all the same color. In other words, the same optical fiber ribbon 100 contains two or more types of colored optical fiber cores 1 having colored layers 5 of different colors.

It is also preferable that there is no difference in the absorbance of ultraviolet light depending on the color of the colored layer 5. For example, if the optical fiber colored core 1-1 has a white colored layer 5 and the optical fiber colored core 1-n has a black colored layer 5, the absorbance of ultraviolet light may differ between these two optical fiber colored cores 1. One possible solution to this problem is to add an additive to the third ultraviolet-curable resin that forms the colored layer 5 to adjust the absorbance of ultraviolet light of a specified wavelength according to the color of the colored layer 5 to be formed. By appropriately adjusting the type and amount of additive for each color of the colored layer 5, the difference in absorbance between the multiple optical fiber colored cores 1-1 to 1-n can be reduced.

It is preferable that at least a portion of the wavelength range (first wavelength range) in which the additive added to the third ultraviolet curing resin absorbs ultraviolet light overlaps with the wavelength range (second wavelength range) in which the photoinitiator added to the first ultraviolet curing resin absorbs ultraviolet light.

The adhesive layer 101 is formed by irradiating a coating material containing an ultraviolet-curable resin with ultraviolet light to cure it. In this specification, the adhesive layer 101 is also referred to 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. The colored optical fiber core wires 1 can be bundled at a high density by taking the form of an optical fiber ribbon 100. The optical fiber ribbon 100 is not limited to the configuration shown in FIG. 3. The optical fiber ribbon 100 may also take the form of an optical fiber ribbon cable in which the optical fiber ribbon 100 is housed in a sheath.

Figure 4 is a schematic diagram of a ribbon forming device 80 used in the manufacturing method of the optical fiber ribbon 100 according to this embodiment. The ribbon forming device 80 has a resin applicator 81 and an ultraviolet ray irradiation device 82. The resin applicator 81 holds an ultraviolet ray curing resin (hereinafter referred to as the "fourth ultraviolet ray curing resin") which is the coating material of the adhesive layer 101.

The colored optical fiber core wires 1 prepared in multiple different colors enter the ribbon forming device 80, where a fourth ultraviolet-curable resin is applied by a resin application device 81. The colored optical fiber core wires 1 coated with the fourth ultraviolet-curable resin are bundled together with multiple other colored optical fiber core wires 1 coated with the fourth ultraviolet-curable resin. The bundled multiple colored optical fiber core wires 1 are irradiated with ultraviolet light by an ultraviolet irradiation device 82 provided in the ribbon forming device 80. As a result, the fourth ultraviolet-curable resin is hardened and becomes an adhesive layer 101. The multiple colored optical fiber core wires 1 arranged in parallel are connected via the adhesive layer 101. In this way, an optical fiber ribbon 100 is formed from the multiple colored optical fiber core wires 1.

The ribbon forming device 80 may be, for example, the ribbon forming device described in JP 2012-118358 A. As a result, the adhesive layer 101 is intermittently formed at a predetermined interval in the longitudinal direction of adjacent colored optical fiber cores 1, and an intermittently bonded optical fiber ribbon 100 is formed.

Figure 5 is a flowchart of the manufacturing method of the colored optical fiber core 1 and the optical fiber ribbon 100 according to this embodiment. First, the user places the optical fiber preform BM in the manufacturing device 10 (step S101).

Next, the heater 21 installed in the heating device 20 heats the optical fiber preform BM, and drawing of the bare optical fiber 2 begins (step S102).

The primary layer coating device 30 applies a first ultraviolet-curing resin around the drawn bare optical fiber 2 and irradiates the first ultraviolet-curing resin with ultraviolet light to form a 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 light to form the secondary layer 4 (step S104). This results in the optical fiber strand 6. The manufactured optical fiber strand 6 is wound up by the first winding device 50.

Then, the colored layer coating device 60 pulls out the optical fiber 6 from the fiber holding device 55 or the first winding device 50, applies a third ultraviolet-curing resin around the secondary layer 4 of the optical fiber 6, and irradiates the third ultraviolet-curing resin with ultraviolet light to form a colored layer 5 (step S105). By coating the optical fiber 6 with the colored layer 5, the optical fiber colored core wire 1 is obtained. After manufacture, the colored optical fiber core wire 1 is wound up by the second winding device 70.

In this embodiment, multiple optical fiber colored cores 1 are manufactured, each having a different color of colored layer 5. Therefore, the processing of step S105 is performed by changing the manufacturing conditions, such as the composition of the third ultraviolet-curable resin, for each color.

In addition, it is not necessary to irradiate ultraviolet light in the process of forming the primary layer 3 (step S103). In this case, the primary layer 3 can be hardened in the process of forming the secondary layer 4 (step S104).

After the colored layer 5 is formed in step S105, the ribboning device 80 applies a fourth ultraviolet-curing resin to cover the multiple colored optical fiber cores 1 prepared in different colors, and irradiates the fourth ultraviolet-curing resin with ultraviolet light to connect the multiple colored optical fiber cores 1 to each other (step S106). In this way, the optical fiber ribbon 100 is manufactured.

According to this embodiment, when coloring an optical fiber strand 6 having a primary layer that is not sufficiently cured, the absorbance difference for each color of the colored layer 5 at the wavelength of the UV light source is reduced. Specifically, among multiple colored optical fiber cores 1 included in the same optical fiber ribbon 100, the difference in Young's modulus of the primary layer 3 between the optical fiber cores 1 having different colored layer 5 colors is adjusted to be 0.1 MPa or less. As a result, even if the same optical fiber ribbon 100 includes multiple colored optical fiber cores 1 having different colored layer 5 colors, the microbend loss difference and strength difference between the multiple colored optical fiber cores 1 can be reduced.

The following describes the results of an experiment conducted to simulate the coloring process on the optical fiber strand 6 described above.

When additional UV irradiation was applied to the optical fiber strand 6, in order to simulate the coloring process of the optical fiber, the third UV-curable resin constituting the coloring layer 5 was applied to a thickness of 6 μm ± 2 μm on the quartz glass that does not have absorption properties for the UV light used, covering the optical fiber strand 6. When additives were added, they were added to the third UV-curable resin constituting the coloring layer 5. The third UV-curable resin constituting the coloring layer 5 is composed of oligomers, monomers, etc., and may also contain additives such as photoinitiators, photosensitizers, UV absorbers, antioxidants, and pigments.

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

The "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. Also, the "Young's modulus" in Table 1 is the ISM (In Situ Modulus) of the primary layer 3 of the colored optical fiber core 1. The ISM is defined as being measured by the following method.

First, a commercially available stripper is used to strip off the primary layer 3 and the secondary layer 4 from the middle of the sample optical fiber by a length of several mm, and then one end of the optical fiber on which the coating layer is formed is fixed on a slide glass with an adhesive, and a load F is applied to the other end of the optical fiber on which the coating layer is formed. In this state, the displacement δ of the primary layer 3 at the boundary between the part where the coating layer is stripped off and the part where the coating layer is formed is read under a microscope. Then, a graph of the displacement δ against the load F is created by setting the load F to 10, 20, 30, 50, and 70 gf (i.e., 98, 196, 294, 490, and 686 mN, respectively). Then, the primary elastic modulus is calculated using the slope obtained from the graph and the following formula (1). The calculated primary elastic modulus corresponds to the so-called ISM, and is hereinafter referred to as P-ISM as appropriate. When drawing the colored optical fiber 1, the drawing speed and the illuminance of the ultraviolet light were controlled to adjust the P-ISM.
P-ISM=(3F/δ)*(1/2πl)*ln(DP/DG)...(1)

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

There are various possible methods for measuring microbend loss. In this specification, the value of microbend loss is defined as the difference between the transmission loss of the optical fiber to be measured in state A, in which an optical fiber of 400 m or more in length is wound in a single layer with no overlapping, with a tension of 100 gf, around a large bobbin wrapped with #1000 grit sandpaper, and the transmission loss of the optical fiber in state B, in which the optical fiber is wound around the same bobbin as in state A, with the same tension and length as in state A, but without sandpaper. Here, the transmission loss of the optical fiber in state B does not include microbend loss, and is considered to be a transmission loss inherent to the optical fiber itself.

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

The effective core area Aeff can be used as an index of the susceptibility of an optical fiber to microbend loss. The effective core area is expressed by the following formula (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 area Aeff represents the area of a portion of a cross section perpendicular 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, the weaker the optical confinement in the cross section of the bare optical fiber 2. That is, when the effective core area Aeff of the bare optical fiber 2 is large, the light in the bare optical fiber 2 is likely to leak due to an external force applied to the bare optical fiber 2. For this reason, when the effective core area Aeff of the bare optical fiber 2 is large, the microbend loss of the colored optical fiber 1 is likely to occur.

In each of the examples and comparative examples, an optical fiber having an effective core area Aeff of 80 ^μm2 or more is used as the optical fiber. In an optical fiber, the effective core area Aeff is an index of microbending sensitivity, and the larger the effective core area Aeff, the higher the microbending sensitivity. In general, it is said that an effective core area Aeff of more than 100 ^μm2 has high microbending sensitivity. Therefore, an effective core area Aeff of 130 ^μm2 or more and 150 ^μm2 or less means an optical fiber with high microbending sensitivity without any problems.

The absorbance in each of the examples and comparative examples was determined as follows. The third ultraviolet-curable resin constituting the colored layer was applied to a quartz glass with a film thickness of 6 μm±2 μm, and the absorbance of the prepared coated quartz glass was measured using a spectrophotometer (PerkinElmer, Lambda 900). The absorbance of the third ultraviolet-curable resin forming the colored layer 5 was determined by subtracting the absorbance of the quartz glass alone, which was measured in advance, from the absorbance of the coated quartz glass. The absorbance A in each of the examples and comparative examples is expressed 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 molar extinction coefficient, c is the concentration of the absorbing substance, and l is the distance of the medium through which the light passes.

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

For the optical fiber strand 6 used in each of the examples and comparative examples, first, a first ultraviolet-curable resin was applied around the drawn bare optical fiber strand 2, and then ultraviolet light was irradiated onto the first ultraviolet-curable resin to form a primary layer 3.

Next, a second ultraviolet-curable resin was applied around the primary layer 3, and the second ultraviolet-curable resin was irradiated with ultraviolet light to form the secondary layer 4. Note that it is not always necessary to irradiate ultraviolet light in the process of forming the primary layer 3. In this case, the primary layer 3 can be hardened by irradiating it with ultraviolet light in the process of forming the secondary layer 4.

When drawing the optical fiber 6, the drawing speed and illuminance were controlled to adjust the Young's modulus of the P-ISM or secondary layer 4. 2,4,6-trimethylbenzoyl-diphenylphosphine oxide was used as the photoinitiator for the primary layer 3 of the colored optical fiber core 1. When this photoinitiator is used in a reaction by UV irradiation, the absorbance in the vicinity of 340 to 410 nm decreases.

By comparing the absorbance before and after UV irradiation to confirm the change in absorbance, the absorption wavelength of the photoinitiator contained in the primary layer 3 can be detected. Of course, it is easy to determine whether the absorption wavelength is derived from the photoinitiator without using this method. For 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 available on the market.

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

In each of the examples and comparative examples, the manufacturing conditions (linear speed and illuminance) were controlled and the first UV-curable resin that forms the primary layer 3 was selected to adjust the fibers used to have various Young's moduli and maximum Young's moduli. 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. In Examples 2, 5, and 8, 10.0 wt% of TiO ₂ (Ishibashi Sangyo Co., Ltd./CR-60-2) was added as Additive B. By adding these additives to the ultraviolet curing resin that forms the colored layer, the absorbance of ultraviolet light in a specified wavelength range is increased.

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

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

In Example 3, an optical fiber strand with 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 was covered with a third ultraviolet-curing resin that formed a white colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 3a), the Young's modulus after additional UV irradiation was 0.38 MPa. On the other hand, when the optical fiber strand was covered with an ultraviolet-curing resin that formed a black colored layer with 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, a difference from the white color of 0.01 MPa.

In Example 4, an optical fiber strand with 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 a third ultraviolet-curing resin that formed a white colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 4a), the Young's modulus after additional UV irradiation was 0.58 MPa. On the other hand, when the optical fiber strand 6 was covered with a third ultraviolet-curing resin that formed a black colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm by adding additive A (Example 4b), the Young's modulus after additional UV irradiation was 0.62 MPa, a difference from the white color of 0.04 MPa.

In Example 5, an optical fiber strand with 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 a third ultraviolet-curing resin that formed a white colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 5a), the Young's modulus after additional UV irradiation was 0.58 MPa. On the other hand, when the optical fiber strand 6 was covered with a third ultraviolet-curing resin that formed a black colored layer 5 with an absorbance of 0.55 for ultraviolet rays with a wavelength of 365 nm by adding additive B (Example 5b), the Young's modulus after additional UV irradiation was 0.63 MPa, a difference from the white color of 0.05 MPa.

In Example 6, an optical fiber strand with 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 was covered with a third ultraviolet-curing resin that formed a white colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 6a), the Young's modulus after additional UV irradiation was 0.51 MPa. On the other hand, when the optical fiber strand 6 was covered with a third ultraviolet-curing resin that formed a black colored layer 5 with an absorbance of 0.25 for ultraviolet rays with a wavelength of 365 nm (Example 6b), the Young's modulus after additional UV irradiation was 0.55 MPa, a difference from the white color of 0.04 MPa.

In Example 7, an optical fiber strand with 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 was covered with a third ultraviolet-curing resin that formed a white colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 7a), the Young's modulus after additional UV irradiation was 0.63 MPa. On the other hand, when the optical fiber strand 6 was covered with a third ultraviolet-curing resin that formed a black colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm by adding additive A (Example 7b), the Young's modulus after additional UV irradiation was 0.63 MPa, the difference from the white color was 0.00 MPa.

In Example 8, an optical fiber strand with 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 was covered with a third ultraviolet-curing resin that formed a white colored layer with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Example 8a), the Young's modulus after additional UV irradiation was 0.63 MPa. On the other hand, when the optical fiber strand 6 was covered with a third ultraviolet-curing resin that formed a black colored layer 5 with an absorbance of 0.55 for ultraviolet rays with a wavelength of 365 nm by adding additive B (Example 8b), the Young's modulus after additional UV irradiation was 0.67 MPa, a difference from the white color of 0.04 MPa.

In Comparative Example 1, an optical fiber strand 6 with 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 was covered with a third ultraviolet-curing resin that formed a white colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Comparative Example 1a), the Young's modulus after additional UV irradiation was 0.82 MPa. On the other hand, when the optical fiber strand was covered with a third ultraviolet-curing resin that formed a black colored layer 5 with an absorbance of 0.25 for ultraviolet rays with a wavelength of 365 nm (Comparative Example 1b), the Young's modulus after additional UV irradiation was 1.04 MPa. The difference between the white and black strands was 0.22 MPa, which was more than 0.1 MPa.

In Comparative Example 2, an optical fiber 6 with 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 was covered with a third ultraviolet-curing resin that formed a white colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Comparative Example 2a), the Young's modulus after additional UV irradiation was 0.58 MPa. On the other hand, when the optical fiber 6 was covered with a third ultraviolet-curing resin that formed a black colored layer 5 with an absorbance of 0.25 for ultraviolet rays with a wavelength of 365 nm (Comparative Example 2b), the Young's modulus after additional UV irradiation was 0.71 MPa. The difference between the white and black colors was 0.13 MPa, which was more than 0.1 MPa.

In Comparative Example 3, an optical fiber strand 6 with 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 was covered with a third ultraviolet-curing resin that formed a white colored layer 5 with an absorbance of 0.66 for ultraviolet rays with a wavelength of 365 nm (Comparative Example 3a), the Young's modulus after additional UV irradiation was 0.63 MPa. On the other hand, when the optical fiber strand was covered with a third ultraviolet-curing resin that formed a black colored layer 5 with an absorbance of 0.25 for ultraviolet rays with a wavelength of 365 nm (Comparative Example 3b), the Young's modulus after additional UV irradiation was 0.74 MPa. The difference between the white and black strands was 0.11 MPa, which was greater than 0.1 MPa.

In the above examples and comparative examples, the colored layers are white and black, but the present invention can be applied to any combination of colors that have different absorbance in the UV range. Examples of colors include white, black, gray, purple, blue, light blue, green, brown, yellow, orange, pink, and red.

In each of the examples and comparative examples, the Young's modulus after additional UV irradiation is defined as the P-ISM when the optical fiber 6 is re-irradiated with ultraviolet light under conditions of 1500 mW/cm ² and 500 mJ/cm ² using a UV-LED with an irradiation wavelength of 365 nm±20 nm, but the UV light source is not limited to a UV-LED with a wavelength of 365 nm±20 nm. For example, a similar effect can be obtained when an additive having an absorption region within the range of a UV-LED with a different wavelength, such as a UV-LED with a wavelength of 385 nm±20 nm or a UV-LED with a wavelength of 395 nm±20 nm, or a UV-LED that emits UV light other than a UV-LED, such as a metal halide lamp or a mercury lamp, is used. In addition, a similar effect can be obtained when irradiation is performed under other conditions regarding illuminance and irradiation amount.

In addition, the additives used in Examples 1, 2, 4, 5, and 7 are merely examples, and are not limited to ultraviolet absorbers and pigments, but may be additives such as photoinitiators and photosensitizers that have an absorption wavelength in the ultraviolet wavelength range of the UV light source used. In addition to additives A and B, for example, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide), 2-isopropylthioxanthone, 2,2-dihydroxy-4,4-dimethoxybenzophenone, 2,4,6-tris[4-(hexyloxy)-2-hydroxy-3-methylphenyl]-1,3, Compounds such as 5-triazine (2,4,6-Tris[4-(hexyloxy)-2-hydroxy-3-methylphenyl]-1,3,5-triazine) and 2-(2-hydroxy-5-methylphenyl)benzotriazole can also be used as additives.

It is also clear that the type of additive that is effective depends on the absorption wavelength of the photoinitiator used in the primary layer 3. Therefore, it is important to add an additive that has an absorption wavelength range that is at least partially the same as the absorption wavelength range of the photoinitiator used.

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

In addition, 19 types of optical fiber colored cores 1 with secondary layer 4 having a Young's modulus of approximately 1000 MPa and primary layer 3 having different Young's moduli were randomly selected, and the Young's modulus difference and microbend loss difference of each primary layer 3 were calculated.

Figure 6 is a graph showing the relationship between the Young's modulus difference of the primary layer 3 of the optical fiber colored core 1 according to the embodiment and the proportion of microbend loss differences of 0.05 dB/km or more. As shown in Figure 6, when the proportion of microbend loss differences of 0.05 dB/km or more was calculated for each range of 0.05 MPa of Young's modulus difference, it was confirmed that the proportion of microbend loss differences of 0.05 dB/km or more increases sharply at the boundary of a Young's modulus difference of 0.1 MPa. This shows that it is desirable for the difference in Young's modulus of the primary layer 3 of each optical fiber colored core 1 used in the same optical fiber ribbon 100 to be 0.1 MPa or less. This is consistent with the results of the above-mentioned Examples 1 to 8.

The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, an example in which part of the configuration of one of the embodiments is added to another embodiment, or an example in which part of the configuration of another embodiment is replaced with another embodiment, is also an embodiment of the present invention. Furthermore, with regard to parts not specifically explained or illustrated in the embodiments, well-known or publicly known techniques in the relevant technical field can be applied as appropriate.

Reference Signs List 1 Colored optical fiber core 2 Bare optical fiber 3 Primary layer 4 Secondary layer 5 Colored layer 6 Optical fiber core 100 Optical fiber ribbon 101 Adhesive layer

Claims (14)

a plurality of colored optical fiber core wires, each of which has a bare optical fiber, a primary layer formed of a first ultraviolet-curable resin covering the bare optical fiber, a secondary layer formed of a second ultraviolet-curable resin covering the primary layer, and a colored layer formed of a third ultraviolet-curable resin covering the secondary layer;
an adhesive layer formed of a fourth ultraviolet curing resin covering the plurality of colored optical fibers and connecting the plurality of colored optical fibers;
An optical fiber ribbon comprising:
the 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 fibers, a difference in Young's modulus between the colored optical fibers having different colors of the colored layer is 0.1 MPa or less;
The photoinitiator added to the first ultraviolet curable resin has absorption in a wavelength range of 340 nm or more and 410 nm or less.
1. An optical fiber ribbon comprising: When the photoinitiator reacts , the absorbance decreases in the wavelength range of 340 nm or more and 410 nm or less.
2. The optical fiber ribbon according to claim 1. The Young's modulus of the primary layer is 0.15 MPa or more and 0.89 MPa or less.
3. The optical fiber ribbon according to claim 1 or 2. At least one of the type and the amount of an additive that changes the absorbance of the third ultraviolet curable resin is adjusted so that a difference in absorbance of the third ultraviolet curable resin is reduced depending on the color of the colored layer in the wavelength range absorbed by the photoinitiator added to the first ultraviolet curable resin.
4. The optical fiber ribbon according to claim 1, wherein the optical fiber ribbon is a tubular member. a difference in absorbance of the third ultraviolet curing resins forming the colored layers having different colors with respect to ultraviolet light is 0.41 or less at a wavelength of 365 nm;
5. The optical fiber ribbon according to claim 1, wherein the optical fiber ribbon is a tubular member. The optical fiber ribbon according to claim 5, wherein the difference in absorbance of the ultraviolet light between the third ultraviolet-curing resins forming the colored layers of different colors is 0.11 or less at a wavelength of 365 nm. A step of drawing a bare optical fiber from an optical fiber preform;
applying a first ultraviolet-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 light to form a secondary layer, thereby manufacturing an optical fiber;
a step of applying a third ultraviolet-curable resin around the optical fiber core and irradiating the third ultraviolet-curable resin with ultraviolet light to form a colored layer, thereby manufacturing a colored optical fiber core;
a step of applying a fourth ultraviolet-curing resin around the plurality of colored optical fiber cores, and irradiating the fourth ultraviolet-curing resin with ultraviolet light to form an adhesive layer, thereby manufacturing an optical fiber ribbon in which the plurality of colored optical fiber cores are connected;
Equipped with
the 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 fibers, a difference in Young's modulus between the colored optical fibers having different colors of the colored layer is 0.1 MPa or less;
The photoinitiator added to the first ultraviolet curable resin has absorption in a wavelength range of 340 nm or more and 410 nm or less.
A method for manufacturing an optical fiber ribbon comprising the steps of: When the photoinitiator reacts , the absorbance decreases in the wavelength range of 340 nm or more and 410 nm or less.
8. The method for producing an optical fiber ribbon according to claim 7. 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;
9. The method for producing an optical fiber ribbon according to claim 7 or 8. The Young's modulus of the primary layer is 0.15 MPa or more and 0.89 MPa or less.
10. The method for producing an optical fiber ribbon according to claim 7, wherein the first and second fibers are arranged in a first direction. At least one of the type and the amount of an additive that changes the absorbance of the third ultraviolet curable resin is adjusted so that a difference in absorbance of the third ultraviolet curable resin is reduced depending on the color of the colored layer in the wavelength range absorbed by the photoinitiator added to the first ultraviolet curable resin.
11. The method for producing an optical fiber ribbon according to claim 7. a difference in absorbance of the ultraviolet ray between the third ultraviolet curing resins forming the colored layers having different colors is 0.41 or less at a wavelength of 365 nm;
12. The method for producing an optical fiber ribbon according to claim 7, wherein the optical fiber ribbon is a ribbon having a diameter of 100 mm or less. The method for manufacturing an optical fiber ribbon according to claim 12, wherein the difference in absorbance of the ultraviolet light between the third ultraviolet-curing resins forming the colored layers of different colors is 0.11 or less at the wavelength of 365 nm. In the step of manufacturing the optical fiber, the first ultraviolet curing resin and the second ultraviolet curing resin are irradiated with ultraviolet light.
14. The method for producing an optical fiber ribbon according to claim 7, wherein the optical fiber ribbon is a ribbon having a diameter of 100 mm or less.

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