Optical cable slot and optical cable

Abstract

To provide an optical cable slot that includes a rib excellent in collapse strength even if being a thin wall, and enabling suppressing undulation upon flexing of an optical cable.SOLUTION: An optical cable slot according to one embodiment of the present disclosure has a plurality of ribs that contains resin of which a flexural modulus is 1000 MPa or more, and is provided in an outer surface in a spiraling way to an axial direction. A ratio h1 / t of an average height h1 to an average thickness t in the rib is 4 or more, the rib has a plurality of slits that extends toward a direction from an outer edge part in a longitudinal direction, and a ratio h2 / h1 of an average depth h2 of the slit to the average height h1 of the rib is 0.5 or more, and 0.8 or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a slot for an optical cable and an optical cable. [Background technology]

[0002] Conventionally, optical cable slots have been known that have multiple grooves on the outer surface, each of which accommodates a single optical fiber or a ribbon optical fiber consisting of multiple optical fibers bundled together with a covering.

[0003] Generally, optical fiber slots are formed by extrusion molding using a resin composition such as polyethylene. The optical fiber slot has multiple spiral or SZ-shaped ribs extending axially along the outer periphery, with two adjacent ribs forming a groove.

[0004] As such a slot for an optical cable, one formed using polyethylene, which exhibits excellent properties such as surface smoothness and dimensional stability, has been devised (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-333476 Summary of the Invention

[0006] A slot for an optical cable according to one embodiment of the present disclosure contains a resin having a flexural modulus of elasticity of 1000 MPa or more, has a plurality of ribs arranged spirally in the axial direction on the outer surface, the ratio h1 / t of the average height h1 of the ribs to the average thickness t of the ribs being 4 or more, the ribs having a plurality of slits extending in the axial direction from the longitudinal outer edge, and the ratio h2 / h1 of the average depth h2 of the slits to the average height h1 of the ribs being 0.5 or more and 0.8 or less. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view of an optical cable according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view of an optical cable slot according to one embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic partial perspective view of a rib. [Figure 4] FIG. 4 is a schematic partial view of a slot for explaining the average height of a rib. [Figure 5] FIG. 5 is a schematic partial plan view of a rib. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Problem to be solved by this disclosure] Optical cables are subject to external bending during cable routing, so they require crushing strength to withstand such bending. Furthermore, optical cables used in data centers and other applications are required to transmit large amounts of data, so they must pack as many optical fibers as possible into a given diameter of optical cable to increase density. However, when polyethylene, which has traditionally been used as a material for optical cable slots, is used, the crushing strength of the optical cable ribs is insufficient when the ribs are thinned to increase optical fiber density. On the other hand, using a high-strength material for optical cable slots reduces flexibility, which creates the problem of rib undulations occurring more easily when the optical cable is bent.

[0009] The present disclosure has been made based on the above circumstances, and aims to provide a slot for an optical cable that is thin-walled but has excellent crushing strength and is equipped with ribs that can suppress undulation when the optical cable is bent.

[0010] [Effects of this disclosure] The optical cable slot of the present disclosure allows for a thinner rib, and is excellent in the crush strength of the rib and in the suppression of undulations when the optical cable is bent.

[0011] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0012] A slot for an optical cable according to one embodiment of the present disclosure contains a resin having a flexural modulus of elasticity of 1000 MPa or more, has a plurality of ribs arranged spirally in the axial direction on the outer surface, the ratio h1 / t of the average height h1 of the ribs to the average thickness t of the ribs being 4 or more, the ribs having a plurality of slits extending in the axial direction from the longitudinal outer edge, and the ratio h2 / h1 of the average depth h2 of the slits to the average height h1 of the ribs being 0.5 or more and 0.8 or less.

[0013] The optical cable slot (hereinafter simply referred to as the slot) contains a resin with a flexural modulus of 1000 MPa or more, thereby providing excellent crushing strength against bending. Furthermore, by setting the ratio h1 / t (the average height h1 of the rib of the optical cable slot to its average thickness t) to 4 or more, the rib can be thinned. Furthermore, by having the rib have multiple slits extending axially from the longitudinal outer edge, and by setting the ratio h2 / h1 (the average depth h2 of the slits to their average height h1) to 0.5 or more and 0.8 or less, the rib can be provided with appropriate elasticity while maintaining its crushing strength. Therefore, the optical cable slot not only allows for thinning of the rib, but also provides excellent rib crushing strength and suppresses undulation when the optical cable is bent. Here, the "flexural modulus" is a value measured in accordance with JIS-K-7171 (2016). In this disclosure, the "average" in the "average thickness" refers to the average value of thicknesses measured at three arbitrary points. The same applies to the "average height," "average width," and "average depth" described below. In this disclosure, "thin-walled" means that the ratio h1 / t of the average height h1 to the average thickness t is 4 or more.

[0014] The twist pitch of the ribs is preferably 600 mm or more and 1600 mm or less. By having the twist pitch of the ribs be 600 mm or more and 1600 mm or less, the crushing strength of the ribs can be maintained while improving the effect of suppressing undulations during bending. The "twist pitch of the ribs" refers to the axial spacing at which the ribs 2 are twisted spirally and are positioned at the same radial position in the cross section of the slot for optical cable.

[0015] The average width of the slits is preferably 0.1 mm or more and 20 mm or less. By setting the average width of the slits to 0.1 mm or more and 20 mm or less, the crushing strength of the rib can be maintained while the effect of suppressing undulations during bending can be improved.

[0016] It is preferable that the rib has at least one slit per pitch, which can maintain the crush strength of the rib while enhancing the effect of suppressing undulations during bending.

[0017] An optical cable according to another aspect of the present disclosure comprises the slot, a tension member embedded in the center of the slot, an optical fiber arranged between adjacent ribs, and an outer jacket covering the slot and the optical fiber.

[0018] The optical cable includes the optical cable slot of the present disclosure, which allows for the thinning of the ribs in the optical cable slot, and provides excellent rib crush strength and suppression of undulation when the optical cable is bent.

[0019] [Details of the embodiments of the present disclosure] Hereinafter, an optical cable slot and an optical cable according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0020] <Optical cable> As shown in Figure 1, the optical cable 11 includes a slot for the optical cable (hereinafter also referred to as a slot) 2 having a plurality of ribs 21, a tension member 1 embedded in the center of the slot 2, an optical fiber 4 arranged between adjacent ribs 21, and an outer jacket 5 covering the slot 2 and the optical fiber 4.

[0021] The optical cable 11 may further include an adhesive layer that bonds the tension member 1 to the optical cable slot, and the tension member 1 may be embedded in the optical cable slot 2 via the adhesive layer. The adhesive layer is mainly composed of an adhesive that bonds the tension member 1 to the optical cable slot 2. There are no particular restrictions on the adhesive as long as it can adhere to the tension member 1 and the optical cable slot 2, and a thermoplastic resin such as polyethylene can be used. The "main component" refers to the component with the highest content, for example, a component that accounts for 50% or more by mass of the total mass of the adhesive layer.

[0022] <Optical cable slot> The optical cable slot 2 according to one embodiment of the present disclosure has a tension member 1 embedded in the center and multiple ribs spiraling in the axial direction on the outer circumferential surface. The optical cable slot 2 has multiple ribs 21 protruding from the circumferential surface of the main body 24. The central axis of the main body 24 coincides with the central axis of the tension member 1.

[0023] The optical cable slot 2 contains a resin having a flexural modulus of 1000 MPa or more. If the flexural modulus of the optical cable slot 2 is lower than the lower limit, the deformability of the optical cable 11 may be insufficient. The upper limit of the flexural modulus of the optical cable slot 2 is not particularly limited, but is, for example, 2500 MPa.

[0024] Examples of resins having a flexural modulus of 1000 MPa or more that can be used to form the slot for optical cable 2 include polyethylene and polypropylene. Among these, polypropylene or high-density polyethylene is preferred from the viewpoint of increasing the crushing strength of the rib 21.

[0025] The lower limit of the content of the resin having a flexural modulus of 1000 MPa or more in the slot 2 for optical cable is preferably 60% by mass, more preferably 70% by mass, and even more preferably 75% by mass. If the content of the resin is less than 50% by mass, the crush strength of the slot 2 for optical cable and the effect of suppressing undulation during bending may not be sufficiently obtained.

[0026] The slot 2 for optical cable may contain other components in addition to the resin having a strength of 1000 MPa or more. Examples of other components include resins other than the resin having a strength of 1000 MPa or more and various additives. The upper limit of the content of other components is preferably 5% by mass, more preferably 1% by mass, and even more preferably, the slot 2 for optical cable may be substantially free of other components.

[0027] The optical cable slot 2 has a groove formed by the surfaces of the adjacent ribs 21, and the optical fiber 4 is disposed in this groove. FIG. 2 shows an example in which eight optical cable slots 2 have grooves. As shown in FIG. 3, the grooves of the optical cable slots 2 are formed in a spiral shape. Also, as shown in FIG. 3, the grooves of the optical cable slots 2 are formed in a spiral shape. Furthermore, the shape of the grooves formed by the adjacent ribs 21 in a cross-sectional view can be, for example, a V-shape, a rectangular shape, a U-shape, a fan shape, etc. As shown in FIG. 2, in this embodiment, the shape of the groove is a fan shape.

[0028] (rib) The ribs 21 have a shape that protrudes from the peripheral surface of the main body of the slot 2. The ribs 21 are provided spirally in the axial direction on the outer peripheral surface. Each rib 21 is strip-shaped and is formed integrally with the main body 24 such that its inner edge in the longitudinal direction is joined to the main body 24 in a spiral shape. Each rib 21 is strip-shaped and is formed integrally with the main body 24 such that its inner edge in the longitudinal direction is joined to the main body 24 in a spiral shape.

[0029] A groove of the slot 2 is formed between adjacent ribs 21, and is separated from the grooves of other slots 2 for optical cables. In other words, the groove of the slot 2 for optical cables is a groove between adjacent ribs 21. The optical fiber 4 is placed in the groove formed between adjacent ribs 21.

[0030] The twist pitch of the ribs is preferably 600 mm or more and 1600 mm or less, and more preferably 600 mm or more and 800 mm or less. By having the twist pitch of the ribs be 600 mm or more and 1600 mm or less, the crush strength of the ribs can be maintained while the effect of suppressing undulations during bending can be improved.

[0031] The average height h1 of the ribs 21 is preferably 5 mm or more and 30 mm or less, and more preferably 6 mm or more and 25 mm or less. By setting the average height h1 of the ribs 21 to 5 mm or more and 30 mm or less, the crushing strength of the ribs 21 can be maintained while improving the effect of suppressing undulation during bending.

[0032] The "average height h1 of the ribs 21" refers to the average value of heights measured in the following procedure. Fig. 4 is a schematic partial diagram of the slot 2 to explain the average height h1 of the ribs 21. As shown in Fig. 4, first, a straight line is set connecting two points L1 and L2 located at the lowest points of adjacent grooves with any rib 21 interposed therebetween. Then, when this straight line is set as the base, the average height h1 is determined as the average height of the perpendicular lines connecting the base and the apex of the rib 21.

[0033] The average thickness t of the rib 21 is preferably 0.5 mm or more and 5.0 mm or less, and more preferably 0.5 mm or more and 3 mm or less. By setting the average thickness t of the rib 21 to 0.5 mm or more and 3 mm or less, the crush strength of the rib 21 can be maintained while improving the effect of suppressing undulation during bending.

[0034] The ratio h1 / t of the average height h1 to the average thickness t of the rib 21 is 4 or more, and more preferably 5 or more. When the ratio h1 / t of the average height h1 to the average thickness t of the rib 21 is 4 or more, the rib 21 can be made thinner. By making the rib 21 thinner, optical fibers can be accommodated at a higher density.

[0035] (slit) The rib has a plurality of slits 25 extending axially from the outer edge in the longitudinal direction. The slits 25 are arranged at intervals in the longitudinal direction of the rib 21. The slits 25 open on the outer edge side in the longitudinal direction, and as shown in Fig. 4, the slits 25 extend inward substantially perpendicularly from the outer edge in the longitudinal direction of the rib 21 in a plan view.

[0036] The ratio h2 / h1 of the average depth h2 of the slits 25 to the average height h1 of the ribs 21 is 0.5 or more and 0.8 or less, and preferably 0.6 or more and 0.8 or less. By setting the ratio h2 / h1 of the average depth h2 of the slits 25 to the average height h1 of the ribs 21 to 0.5 or more and 0.8 or less, it is possible to impart appropriate elasticity to the ribs while maintaining their crushing strength.

[0037] It is preferable that the rib 21 has at least one slit per pitch, and more preferably four or more slits per pitch. By having the rib 21 have at least one slit per pitch, the crush strength of the rib 21 can be maintained while improving the effect of suppressing undulation during bending.

[0038] The average width w1 of the slits 25 is preferably 0.1 mm or more and 20 mm or less, and more preferably 2 mm or more and 18 mm or less. By setting the average width w1 of the slits 25 to 0.1 mm or more and 20 mm or less, the crushing strength of the rib can be maintained while improving the effect of suppressing undulation during bending.

[0039] (tension member) The optical fiber 11 has a tension member 1 disposed in the center to bear tension and prevent it from stretching due to its own weight during installation. If the optical fiber slot and the tension member are not firmly bonded, they may shift during installation, causing only the optical fiber slot to stretch, putting tension on the optical fiber and potentially causing transmission loss or breakage. The tension member 1 can be, for example, a metal single wire or twisted wire, or a linear body made of organic or inorganic fibers.

[0040] (optical fiber) A known optical fiber can be used as the optical fiber 4. For example, a ribbon core wire in which a plurality of optical fiber core wires are bundled with a coating can be suitably used, but a single optical fiber core wire can also be used. When a ribbon core wire is used as the optical fiber 4, the optical cable 11 becomes a so-called tape slot type optical cable.

[0041] (outer covering) The jacket 5 is a resin layer that covers the outer periphery of the slot for optical cable 2 and the optical fiber 4. There are no particular limitations on the main component of the jacket 5, and polyethylene or the like is used, for example. The jacket 5 may have a multi-layer structure having multiple types of layers.

[0042] [Optical cable manufacturing method] Next, an example of a method for manufacturing the optical cable will be described. The method for manufacturing the optical cable includes, for example, a step of manufacturing a slot for the optical cable, a step of assembling the optical cables, and a step of covering the outer jacket.

[0043] In the process of manufacturing an optical cable slot (optical cable slot manufacturing process), the optical cable slot is formed, for example, by profile extrusion of a resin composition that constitutes the optical cable slot. Specifically, the optical cable slot that covers the tension member is formed by extruding a tension member and a heated resin composition through a die. During this extrusion, the die is rotated, and multiple ribs are erected spirally in the axial direction on the outer peripheral surface of the optical cable slot.

[0044] The optical cable slot can be manufactured not only by extrusion molding, but also by injection molding, compression molding, etc. A cutting machine presses blades against the resulting slot at regular intervals from the longitudinal outer edge of the rib toward the axial direction to form slits. The depth and width of the slit can be adjusted by changing the length and thickness of the blades pressed against it.

[0045] In the step of assembling the optical cables (assembling step), the optical fibers are inserted into the grooves of the optical cable slots formed in the optical cable slot manufacturing step and are then pressed and wound to assemble the optical cables.

[0046] In the step of covering with an outer jacket, the assembly of the optical fiber and slot for optical cable obtained in the assembling step is covered with an outer jacket by a method such as extrusion molding.

[0047] According to this optical cable slot, by thinning the ribs, it is possible to increase the amount of optical fibers that can be accommodated, and the crushing strength of the ribs and the effect of suppressing undulation when the optical cable is bent are excellent.

[0048] According to this optical cable, since it is equipped with the optical cable slot of the present disclosure, the ribs in the optical cable slot can be made thinner, and the ribs have excellent crush strength and are effective in suppressing undulation when the optical cable is bent.

[0049] [Other embodiments] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. [Example]

[0050] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples.

[0051] <Test No. 4~Test No. 6> A slot was molded using 100 parts by mass of polypropylene (Novatec PP EA9FTD, manufactured by Japan Polypropylene) with a flexural modulus of 1800 MPa as the forming material, and was coated on the outer surface of the metal tension member.

[0052] The flexural modulus of the resin used to make the slots was measured using a tensile tester in accordance with JIS-K-7171 (2016).

[0053] The slots were fabricated by heating the resin to 180°C and extrusion molding. The rib shape was such that the average rib height h1 was 24 mm, the average rib thickness t was 3 mm (thin-walled type), and the ratio of the average rib height to the average rib thickness h1 / t was 8. The spiral slot shape was unidirectionally twisted, with one pitch (twist pitch) of 600 mm. The ribs were formed with slits having the average slit depth h2, the ratio h2 / h1 of the average slit depth h2 to the average rib height h1, the average slit width w1, and the number of slits per pitch as shown in Table 1.

[0054] <Test No. 3> The slot was molded in the same manner as in Test No. 4, except that no slits were formed in the ribs of the slot, and the outer peripheral surface of the tension member was covered.

[0055] <Test No. 2> The slot was formed using 100 parts by mass of polyethylene (Nipolon L F13 manufactured by Tosoh Corporation) with a flexural modulus of 800 MPa as the material for forming the slot, and the slot was molded in the same manner as in Test No. 4, except that no slit was formed in the slot, and the slot was coated on the outer surface of the tension member.

[0056] <Test No. 1> The slot was molded in the same manner as in Test No. 2, except that the rib shape of the slot was such that the average rib height h1 was 24 mm, the average rib thickness t was 8 mm (conventional type), and the ratio of the average rib height to the average rib thickness h1 / t was 3, and the slot was coated on the outer surface of the tension member.

[0057] <Evaluation> The test specimens No. 1 to No. 6, which were equipped with the fabricated tension members and slots, were evaluated as follows. The results are shown in Table 1.

[0058] (Swell evaluation) After winding the optical cable slot in two layers around a drum with a radius of 10D (D: diameter of the optical cable slot) mm with a tension of 500 N, the presence or absence of ribs was visually checked. If ribs were found to be wavy, the product was deemed to have failed.

[0059] (Crushing strength test) Two 100mm square stainless steel plates with an average thickness of 10mm were placed above and below the slot, and a load was applied using a compression testing machine. The load at which the rib deformed was taken as the crushing strength, with a grade of A (pass) for a load of 2200N or more and a grade of B (fail) for a load of less than 2200N.

[0060] (Opportunity of optical fiber in the cable) Regarding the density of optical fibers within a cable, the optical fiber occupancy rate is calculated by dividing the total cross-sectional area of ​​all optical fibers contained in the space surrounded by the two ribs and the outer sheath by the cross-sectional area of ​​the space surrounded by the two ribs and the outer sheath.An occupancy rate of 0.4 or more is rated A, and an occupancy rate of less than 0.4 is rated B.

[0061] [Table 1]

[0062] As shown in Table 1, Tests No. 4, No. 6, and No. 7, in which the flexural modulus of the resin material was 1000 MPa or more, the ratio h1 / t (the ratio of the average height h1 of the slot ribs to the average thickness t) was 4 or more, and the ratio h2 / h1 (the ratio of the average depth h2 of the slits to the average height h1 of the ribs) was 0.5 or more and 0.8 or less, had excellent rib crush strength, and no rib waviness was observed in the evaluation of the rib waviness after winding on the drum. Tests No. 4, No. 6, and No. 7 show that the optical fiber density can be improved while maintaining the same crush strength as Test No. 1, a conventional reference example with thick ribs (h1 / t less than 4) whose flexural modulus of the resin material was 800 MPa.

[0063] On the other hand, in Test No. 2, which had a thinner rib than Reference Example Test No. 1, a resin material with a flexural modulus of 800 MP, and no slits, the rib did not undulate when wrapped, but the crushing strength of the rib was poor. In Test No. 3, which had a thinner rib, a resin material with a flexural modulus of 900 MP, and no slits, the rib undulated when wrapped and had poor crushing strength. Furthermore, as shown in Test No. 5, even if the flexural modulus of the resin material was 1000 MPa or more, if the thin rib did not have a slit, undulation occurred when the material was wound around the rib. Furthermore, as shown in Test No. 8, even if the thin rib had a flexural modulus of 1000 MPa or more and a slit, if the h2 / h1 ratio was less than 0.5, undulation occurred when the material was wound around the rib. In Test No. 9, where the h2 / h1 ratio exceeded 0.8, the rib had poor crush strength.

[0064] As a result of the above, it was shown that the slot for optical cable can reduce the thickness of the rib, has high crushing strength of the rib, and is excellent in suppressing ribbing when the optical cable is bent.

[0065] The optical cable slots have thin ribs, which allow for increased optical fiber capacity, and the ribs have excellent crush strength and suppression of undulations when the optical cable is bent. Therefore, optical cables equipped with the optical cable slots are suitable for use in wiring between data centers or data center floors where large amounts of information are transmitted. [Explanation of symbols]

[0066] 1 tension member 2 Optical cable slot 4. Optical fiber 5 Outer cover 11 Optical cable 21 Ribs 22 Center of the slot 24-slot main unit 25 slit

Claims

1. Contains a resin having a flexural modulus of 1000 MPa or more, a main body; and a plurality of ribs spirally provided on an outer circumferential surface of the main body in a direction along the central axis of the main body; a ratio h1 / t of an average height h1 of the rib from the central axis toward the apex of the rib to an average thickness t of the rib in a cross section perpendicular to the central axis is 4 or more; the rib has a plurality of slits extending from its longitudinal outer edge toward the central axis; A slot for optical cable, wherein the ratio h2 / h1 of the average depth h2 of the slit from the longitudinal outer edge of the slit toward the central axis to the average height h1 of the rib is 0.5 or more and 0.8 or less.

2. 2. The slot for optical cable according to claim 1, wherein the twist pitch of the ribs is 600 mm or more and 1600 mm or less.

3. 3. The optical cable slot according to claim 1, wherein the average width of the slit is 0.1 mm or more and 20 mm or less.

4. 3. The optical cable slot according to claim 1, wherein the rib has at least one slit per pitch.

5. The optical cable slot according to claim 1 or 2; a tension member embedded in the center of the slot; an optical fiber disposed between adjacent said ribs; a jacket covering the slot and the optical fiber; An optical cable comprising:

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