Optical fiber ribbon

Abstract

An intermittent-connection-type optical fiber ribbon (1) in which bonded sections (2) in which adjacent optical fiber ribbons (10) are bonded together by an adhesive resin, and non-bonded sections (3) are provided intermittently in a longitudinal direction (L), said optical fiber ribbon (1) wherein the bonded sections (2) are provided on one side of the optical fiber ribbons (10), portions of the bonded sections (2) protrude past a tangent line (T) that passes through the surfaces of the adjacent optical fiber ribbons (10) on the one side thereof, the protrusion height of at least one of longitudinal end sections (2c, 2d) of the bonded sections (2) in the longitudinal direction (L) is greater than the height of central sections of the bonded sections (2), and the compound elastic modulus at 23°C of the adhesive resin is 0.5-6.0 GPa.

Description

[Technical Field]

[0001] This disclosure relates to an optical fiber ribbon. This disclosure claims priority to Japanese Patent Application No. 2020-210491, filed on December 18, 2020, and incorporates the entire contents of that application by reference. [Background technology]

[0002] Patent Documents 1 and 2 disclose a so-called intermittently connected optical fiber ribbon. Patent Document 1 discloses an optical fiber ribbon obtained by applying an adhesive member for bonding optical fiber strands that form the optical fiber ribbon to both the upper and lower surfaces of the optical fiber ribbon in approximately equal amounts. It also discloses that the thickness of the adhesive member of the optical fiber ribbon is set to "thickness = (√3-1) / 2 × D (D is the fiber diameter)", thereby preventing contact between the optical fiber strands and the adhesive member of other optical fiber strands when the optical fiber strands are stacked closely together.

[0003] The optical fiber ribbon of Patent Document 2 also has adhesive members applied to both the upper and lower surfaces of the optical fiber ribbon. Patent Document 2 also discloses that the thickness of a portion of the adhesive member is set to a thickness that protrudes from a tangent line passing through the surface of each mono-coated optical fiber at least in its central portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2016-133607 [Patent Document 2] Japanese Patent Publication No. 2016-146003 Summary of the Invention

[0005] An optical fiber ribbon according to one aspect of the present disclosure includes: An intermittently connected optical fiber ribbon in which, among some or all of a plurality of optical fiber core wires arranged in parallel in a width direction perpendicular to the longitudinal direction, bonded sections where adjacent optical fiber core wires are bonded with an adhesive resin and non-bonded sections where adjacent optical fiber core wires are not bonded with the adhesive resin are provided intermittently in the longitudinal direction, the adhesive portion is provided on one surface of the optical fiber ribbon, a part of the adhesive portion protruding from a tangent line passing through the surface of the adjacent optical fiber core wire on the one side; In the longitudinal direction, at least one of the longitudinal end portions of the adhesive portion has a larger protrusion height than a central portion of the adhesive portion, The adhesive resin has a composite elastic modulus at 23° C. of 0.5 GPa or more and 6.0 GPa or less. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic plan view showing an optical fiber ribbon according to an embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of an optical fiber core according to one embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view of a bonding portion in an optical fiber ribbon according to an embodiment. [Figure 4] FIG. 4 is a schematic side view of a bonding portion in an optical fiber ribbon according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Problem to be solved by this disclosure] The optical fiber ribbon described in Patent Document 1 has approximately the same amount of adhesive resin on both sides of the optical fiber ribbon. The thickness of the adhesive resin is set to a thickness that prevents it from coming into contact with other optical fibers. Therefore, when applying a force that rolls and bends the optical fiber ribbon in its cross-sectional direction during storage in an optical cable, the adhesive resin on the outer side of the bent portion is likely to break or the adhesive resin may peel off from the optical fibers. As a result, there is a risk that the optical fibers may come apart.

[0008] The optical fiber ribbon described in Patent Document 2 has a thickness such that the thickness of some of the adhesive portions on both sides of the optical fiber ribbon protrudes beyond the tangent line passing through the surface of each single-coated optical fiber, at least in the center, which increases the cross-sectional area of ​​the optical fiber ribbon, which is disadvantageous in terms of increasing the density of the optical cable.

[0009] The object of the present disclosure is to suppress an increase in the cross-sectional area of ​​the optical fiber ribbon while making it less likely for the adhesive resin to break down or for the adhesive resin to peel off from the optical fiber, thereby reducing the risk of the optical fiber coming apart.

[0010] [Effects of this disclosure] According to the configuration of the present disclosure, it is possible to suppress an increase in the cross-sectional area of ​​the optical fiber ribbon while making it less likely for the adhesive resin to break down or for the adhesive resin to peel off from the optical fiber core, thereby reducing the risk of the optical fiber core coming apart.

[0011] [Description of the embodiments of the present disclosure] Embodiments of the present disclosure will be listed and described below. An optical fiber ribbon according to one aspect of the present disclosure includes: An intermittently connected optical fiber ribbon in which, among some or all of a plurality of optical fiber core wires arranged in parallel in a width direction perpendicular to the longitudinal direction, bonded sections where adjacent optical fiber core wires are bonded with an adhesive resin and non-bonded sections where adjacent optical fiber core wires are not bonded with the adhesive resin are provided intermittently in the longitudinal direction, the adhesive portion is provided on one surface of the optical fiber ribbon, a part of the adhesive portion protruding from a tangent line passing through the surface of the adjacent optical fiber core wire on the one side; In the longitudinal direction, at least one of the longitudinal end portions of the adhesive portion has a larger protrusion height than a central portion of the adhesive portion, The adhesive resin has a composite elastic modulus at 23° C. of 0.5 GPa or more and 6.0 GPa or less. Typically, the adhesive resin is cut off at the longitudinal ends of the adhesive portion during application, resulting in a thinner adhesive resin than the central portion of the adhesive portion. As a result, the adhesive portion is more likely to break or peel from the longitudinal ends, where stress tends to concentrate. The above configuration makes at least one of the longitudinal ends of the adhesive portion thicker than the central portion of the adhesive portion, thereby suppressing breakage or peeling from the longitudinal ends and reducing the risk of the optical fiber fiber coming apart. Furthermore, the composite elastic modulus of the adhesive resin is 0.5 GPa or more, further reducing the likelihood of the adhesive resin breaking or peeling. Furthermore, the composite elastic modulus of the adhesive resin is 6.0 GPa or less, thereby suppressing transmission loss at low temperatures. Furthermore, the adhesive resin is provided only on one side of the optical fiber ribbon, thereby suppressing an increase in the cross-sectional area of ​​the optical fiber ribbon, contributing to higher optical cable density.

[0012] In the optical fiber ribbon, The tearing force when tearing the adhesive joint, measured based on the tearing test specified in JIS C 6838:2019, is preferably 0.005 N or more and 0.200 N or less. According to this configuration, the tear strength of the adhesive joint is set to 0.005 N or more, which makes it even more difficult for the adhesive resin to break and further reduces the risk of the optical fiber coming apart. Also, because the tear strength of the adhesive joint is set to 0.200 N or less, when a worker tears the adhesive joint, the adhesive resin is unlikely to remain on the optical fiber, which makes it possible to suppress a decrease in workability in subsequent processes, such as the ease of inserting the optical fiber into a protective tube.

[0013] In the optical fiber ribbon, The maximum height of the protrusion from the tangent line in the adhesive portion is preferably 10 μm or more and 100 μm or less. According to this configuration, the maximum protrusion height is set to 10 μm or more, and the amount of adhesive resin used and the cross-sectional area of ​​the adhesive resin are increased, thereby enabling a stronger bond between adjacent optical fibers. As a result, it is even less likely that the adhesive resin will be damaged by external forces, etc., and the risk of the optical fibers coming apart can be further reduced. In addition, the maximum protrusion height is set to 100 μm or less, which can suppress deterioration of transmission loss at low temperatures.

[0014] The optical fiber ribbon comprises: In the width direction, each of the width direction ends of the adhesive portion is preferably positioned outside the center of each of the adjacent optical fibers. According to this configuration, a sufficient amount of adhesive resin is used, and the contact area between the adhesive resin and the optical fiber core wire is increased in the width direction, making it even less likely that the adhesive resin will break or peel off from the optical fiber core wire, thereby further reducing the risk of the optical fiber core wire coming apart.

[0015] [Details of the embodiments of the present disclosure] Hereinafter, examples of embodiments according to the present disclosure will be described with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals even in different drawings, and duplicate descriptions will be omitted as appropriate. In addition, the scale of each drawing used in the following description has been changed as appropriate to make each component recognizable.

[0016] First, an outline of an optical fiber ribbon 1 according to the present disclosure and an optical fiber 10 included therein will be described using Figures 1 and 2. Figure 1 is a schematic plan view showing the optical fiber ribbon 1 according to the present embodiment. The optical fiber ribbon 1 includes a plurality (12 in this example) of optical fibers 10 (including 10A and 10B). The optical fibers 10 are arranged in parallel in a width direction W perpendicular to a longitudinal direction L. The optical fiber ribbon 1 is an intermittently connected optical fiber ribbon in which bonded portions 2, where adjacent optical fibers 10 are bonded with an adhesive resin, and non-bonded portions 3, where adjacent optical fibers 10 are not bonded with an adhesive resin, are provided intermittently along the longitudinal direction L.

[0017] 1, each of the optical fiber ribbon 1 is formed by bonding two or more optical fibers 10, each having one independent core, with an adhesive resin, but this is not limited thereto and each of the optical fiber ribbon 1 may be bonded three or more cores. The optical fiber ribbon 1 may also be formed by using a plurality of optical fibers 10, each having one core, which are collectively coated with a coating resin and connected together. The bonded portions 2 and non-bonded portions 3 may be provided intermittently between some or all of the optical fiber ribbons 10.

[0018] Fig. 2 is a schematic cross-sectional view of the optical fiber 10 according to this embodiment. Specifically, Fig. 2 is a schematic cross-sectional view of the optical fiber 10 shown in Fig. 1 cut along a plane including a thickness direction perpendicular to the longitudinal direction L and width direction W.

[0019] 2 includes an optical fiber 11, a primary resin layer 12, a secondary resin layer 13, and a colored resin layer 14. The outer diameter of the optical fiber 10 is not particularly limited and may be, for example, about 200 μm, or may be larger or smaller than that.

[0020] The optical fiber 11 includes a core and a cladding. The optical fiber 11 is, for example, a glass fiber. The primary resin layer 12 coats the outer periphery of the optical fiber 11. The primary resin layer 12 is formed, for example, from a soft ultraviolet-curable resin with a relatively low Young's modulus. The secondary resin layer 13 coats the outer periphery of the primary resin layer 12. The secondary resin layer 13 is formed, for example, from a hard ultraviolet-curable resin with a relatively high Young's modulus. The colored resin layer 14 coats the outer periphery of the secondary resin layer 13. The colored resin layer 14 is a layer for improving the identification of the optical fiber core 10, and is formed, for example, from a colored ultraviolet-curable resin.

[0021] Next, the bonding portion 2 in the optical fiber ribbon 1 will be described in detail with reference to Fig. 3 and Fig. 4. Fig. 3 is a schematic cross-sectional view of the bonding portion 2 in the optical fiber ribbon 1 according to this embodiment. Specifically, Fig. 3 is a schematic cross-sectional view of the optical fiber cores 10A and 10B shown in Fig. 1 and the bonding portion 2 formed between the optical fiber cores 10A and 10B, cut along a plane including the thickness direction. Note that in Fig. 3, the layers included in the optical fiber cores 10A and 10B are omitted from the illustration.

[0022] The adhesive portion 2 is formed by curing an adhesive resin. The type of adhesive resin is not particularly limited as long as the composite elastic modulus satisfies the above-mentioned requirement, and for example, an acrylic ultraviolet-curable resin or an epoxy ultraviolet-curable resin can be used. The adhesive resin may also be a thermosetting resin.

[0023] The composite modulus of elasticity at 23°C after curing of the adhesive resin is 0.5 GPa or more and 6.0 GPa or less. Furthermore, from the viewpoint of further reducing the risk of breakage of the adhesive resin, the composite modulus is preferably 1 GPa or more, and more preferably 2 GPa or more. Furthermore, from the viewpoint of further suppressing transmission loss at low temperatures, the composite modulus is preferably 4.5 GPa or less, and more preferably 3.0 GPa or less. The composite modulus of elasticity of the adhesive resin can be adjusted, for example, by the type of adhesive resin, the molecular weight of the oligomer, the number of functional groups contained in the monomer, and the compounding ratio thereof. The composite modulus in this specification refers to the composite modulus of elasticity in the thickness direction measured by a test method based on ISO 14577.

[0024] 3, a part of the adhesive portion 2 protrudes above a tangent line T passing through the surfaces (contact points Q1 and Q2) on one side of the adjacent optical fiber cores 10A and 10B. Such a protrusion can be achieved, for example, by adjusting the amount of adhesive resin applied. Here, one side means either above or below the line connecting the centers of the adjacent optical fiber cores.

[0025] Furthermore, the maximum height H of the protrusion from the tangent line T in the adhesive portion 2 is preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 50 μm or less. Such maximum height H of the protrusion can be set, for example, by adjusting the amount of adhesive resin applied.

[0026] Furthermore, it is preferable that the height of the protrusion is greatest near the center of the bonding portion 2 in the width direction W. That is, it is preferable that the height of the protrusion is greatest near the line P3 passing through the contact point between the optical fiber 10A and the optical fiber 10B. It is also preferable that the bonding portion 2 is gently inclined in a curved shape from near the center of the bonding portion 2 in the width direction W toward the width direction ends 2a and 2b.

[0027] In addition, in the width direction W, each of the width direction ends 2a and 2b of the bonding portion 2 is located outside the center of the adjacent optical fiber 10A and 10B. Specifically, the width direction end 2a is located outside the line P1 connecting the center point O1 of the optical fiber 10A and the tangent point Q1. Similarly, the width direction end 2b is located outside the line P2 connecting the center point O2 of the optical fiber 10B and the tangent point Q2. Note that the above-mentioned "outside" refers to the outside when the line P3 is the center. When three or more optical fibers 10 are bonded to form the bonding portion 2, the width direction end 2a and the width direction end 2b are formed between the two outermost optical fibers 10 and the optical fiber 10 located one fiber inward of them.

[0028] In the width direction W, the distance U between the width direction end 2a and the center of the optical fiber 10A (the distance between the line P1 and the line P4 that passes through the width direction end 2a and is parallel to the line P1) is preferably 1 / 10R or more (R is the radius of the optical fiber 10A and 10B) and more preferably 1 / 5R or more, from the viewpoint of further reducing the likelihood of damage to the adhesive resin. Furthermore, from the viewpoint of suppressing deterioration of transmission loss at low temperatures, the distance U is preferably 2 / 3R or less and more preferably 1 / 2R or less. The distance U can be controlled, for example, by adjusting the viscosity and amount of adhesive resin applied when it is applied. The same applies to the distance U between the width direction end 2b and the center of the optical fiber 10B (the distance between the line P2 and the line P2 that passes through the width direction end 2b and is parallel to the line P2).

[0029] The tear strength in the width direction W of the adhesive joint 2 is preferably 0.005 N or more and 0.200 N or less, and more preferably 0.02 N or more and 0.10 N or less. The tear strength in this specification is measured based on the tear test specified in JIS C 6838:2019 (IEC60794-1-23:2019 Ribbon tear test). It is determined as follows.

[0030] FIG. 4 is a schematic side view of a bonding portion 2 in an optical fiber ribbon 1 according to this embodiment. In the longitudinal direction L, at least one of the longitudinal end portions 2c and 2d of the bonding portion 2 preferably protrudes to a greater height than the central portion of the bonding portion 2. As shown in the example of FIG. 4, it is more preferable that both of the longitudinal end portions 2c and 2d of the bonding portion 2 in the longitudinal direction L protrude to a greater height than the central portion of the bonding portion 2 in the longitudinal direction L. The protrusions of the longitudinal end portions 2c and 2d of the bonding portion 2 can be achieved by, for example, adjusting the amount of adhesive resin applied. The protrusion height of the bonding portion 2 from the central portion is preferably 20 μm or more and 100 μm or less.

[0031] [Example] The present disclosure will be described in more detail below by showing examples according to the present disclosure, but the present disclosure is not limited to the following examples.

[0032] The structures and physical properties of the following production examples were measured by the following methods.

[0033] (composite modulus) Using a nanoindenter (BRUKER HYSITRON TI950 Tribolndenter), the composite elastic modulus in the thickness direction of the cured adhesive resin was determined according to the test method based on ISO 14577. The indentation depth was set to 100 nm, and the measurement was performed using a Berkovich indenter.

[0034] (Presence or absence of protrusion, height, and end position) The presence or absence of protrusion of the adhesive portion 2 from the tangent line T in the width direction W, the maximum protrusion height H, and the positions of the width direction ends 2a and 2c were measured using a laser microscope. The same applies to the presence or absence of protrusion of the longitudinal direction ends 2c and 2d of the adhesive portion 2 in the longitudinal direction L.

[0035] (Split resistance) The optical fiber ribbon 1 was evaluated based on the twisting test specified in IEC60794-1-2. The evaluation criteria are as follows: A: It can be twisted 180 degrees 20 times without coming apart. B: It comes apart after 15 to 20 twists at 180°. C: It comes apart after 10 to 15 twists at 180°. D: It comes apart after 180° twisting 5 to 10 times. E: Twists 180° and comes apart in less than 5 times.

[0036] (Low temperature characteristics) A heat cycle test was conducted on the optical fiber ribbon 1, in which one cycle of room temperature (23°C) → -40°C → -60°C was repeated six times. At 23°C and -60°C, the attenuation per unit distance was measured when light with a wavelength of 1.55 μm was incident on the optical fiber 11 included in the optical fiber ribbon 1, and the attenuation was evaluated based on the difference between the measured values ​​under the two temperature environments. The evaluation criteria are as follows: A: The difference in measurement value is 0.05 dB / km or less B: The difference in measurement value is more than 0.05 dB / km and less than 0.1 dB / km C: The difference in measurement value is more than 0.1 dB / km and less than 0.3 dB / km D: The difference in measurement value is 0.3 dB / km or more

[0037] (Tearing force) The tear strength was measured based on the tear test specified in JIS C 6838 (2019). In the tear test, the sample length was 150 mm (set so that the adhesive part was at the center), the chuck distance was 70 mm, and the pulling speed was 200 mm / min. The peak value was taken as the measured value, and measurements were taken for five samples for each manufacturing example, and the arithmetic average of the measured values ​​was taken as the tear strength.

[0038] (Production Examples 1 to 42) Six types of adhesive resins with different composite elastic moduli were used to produce optical fiber ribbons 1 in Production Examples 1 to 42, varying the presence or absence of protrusion from the tangent line T at the adhesive portion 2 and the presence or absence of protrusion at the longitudinal end. In Production Examples 1 to 42, the tear force was approximately 0.03 N. The maximum protrusion height H was approximately 30 μm. The distance U in the width direction W was in the range of 0 to 1 / 2R.

[0039] The optical fiber ribbons 1 of Production Examples 1 to 42 were evaluated for their resistance to fragmentation and low-temperature characteristics. The results are shown in Table 1. In Table 1, Production Examples 8, 9, 14, 15, 20, 21, 26, 27, 32, 33, 38, and 39 are working examples, and the other Production Examples are comparative examples.

[0040] [Table 1]

[0041] (Production Examples 43 to 52) Six types of adhesive resins with different composite elastic moduli were used to vary the tear strength at the adhesive joint 2, and optical fiber ribbons 1 of Production Examples 43 to 52 were produced. In Production Examples 43 to 52, the adhesive joint 2 protruded from the tangent line T, and the distance U in the width direction W of the adhesive joint 2 was in the range of 0 to 1 / 2R. The maximum protrusion height H was approximately 30 μm. The longitudinal ends 2c and 2d of the adhesive joint 2 in the longitudinal direction L protruded more than the center of the adhesive joint 2 in the longitudinal direction L. The optical fiber ribbons 1 of Production Examples 43 to 52 were evaluated for their resistance to unraveling. The results are shown in Table 2. Note that Production Examples 43 to 52 are all working examples.

[0042] [Table 2]

[0043] (Production Examples 53 to 67) Six types of adhesive resins with different composite elastic moduli were used to produce optical fiber ribbons 1 in Production Examples 53 to 67, varying the maximum protrusion height H of the bonded portion 2. In Production Examples 53 to 67, the bonded portion 2 protruded from the tangent line T, and the distance U of the bonded portion 2 in the width direction W was in the range of 0 to 1 / 2R. The tear strength was approximately 0.03 N. The longitudinal ends 2c and 2d of the bonded portion 2 in the longitudinal direction L protruded more than the center of the bonded portion 2 in the longitudinal direction L. The optical fiber ribbons 1 in Production Examples 53 to 67 were evaluated for their resistance to fragmentation and low-temperature properties. The results are shown in Table 3. All of Production Examples 53 to 67 are working examples.

[0044] [Table 3]

[0045] (Production Examples 68 to 87) Six types of adhesive resins with different composite elastic moduli were used to produce optical fiber ribbons 1 in Production Examples 68 to 87, varying the distance U in the width direction W. In Production Examples 68 to 87, the bonded portion 2 protruded from the tangent line T. The tear force was approximately 0.03 N. The maximum protrusion height H was approximately 30 μm. The longitudinal ends 2c and 2d of the bonded portion 2 in the longitudinal direction L protruded further than the center of the bonded portion 2 in the longitudinal direction L. The optical fiber ribbons 1 in Production Examples 68 to 87 were evaluated for their resistance to unraveling and low-temperature characteristics. The results are shown in Table 4. In Table 4, a distance U of less than 0 R means that the widthwise end 2a of the bonded portion 2 in the width direction W was located inside the line P1, and the widthwise end 2b was located inside the line P2. Production Examples 68 to 87 are all working examples.

[0046] [Table 4]

[0047] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to any number, position, shape, etc. that is suitable for implementing the present invention. [Explanation of symbols]

[0048] 1: Optical fiber ribbon 2: Adhesive part 2a, 2b: Width direction end 2c, 2d: Longitudinal ends 3: Non-adhesive area 10, 10A, 10B: Optical fiber core 11: Optical fiber 12: Primary resin layer 13: Secondary resin layer 14: Colored resin layer T: tangent H: Maximum protrusion height L: Longitudinal direction W: Width direction U: distance O1,O2: Center point P1,P2,P3,P4: Straight line Q1, Q2: Contact points R: Radius

Claims

1. An intermittently connected optical fiber ribbon in which, among some or all of a plurality of optical fiber core wires arranged in parallel in a width direction perpendicular to the longitudinal direction, bonded sections where adjacent optical fiber core wires are bonded with an adhesive resin and non-bonded sections where adjacent optical fiber core wires are not bonded with the adhesive resin are provided intermittently in the longitudinal direction, the adhesive portion is provided on one surface of the optical fiber ribbon, a part of the adhesive portion protruding from a tangent line passing through the surface of the adjacent optical fiber core wire on the one side; In the longitudinal direction, at least one of the longitudinal end portions of the adhesive portion has a larger protrusion height than a central portion of the adhesive portion, The adhesive resin has a composite elastic modulus at 23°C of 0.5 GPa or more and 6.0 GPa or less. Optical fiber ribbon core wire.

2. The tear force when tearing the adhesive joint, measured based on the tear test specified in JIS C 6838:2019, is 0.005 N or more and 0.200 N or less. The optical fiber ribbon according to claim 1 .

3. the maximum value of the height of the protrusion from the tangent line at the adhesive portion is 10 μm or more and 100 μm or less; 3. The optical fiber ribbon according to claim 1.

4. In the width direction, each of the width direction ends of the adhesive portion is located outside the center of each of the adjacent optical fibers. The optical fiber ribbon according to any one of claims 1 to 3.

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