Slotted Fiber Optic Cable

Abstract

To provide a slotted optical fiber cable which allows for densely mounting optical fibers while suppressing bending anisotropy.SOLUTION: A slotted optical fiber cable is provided, comprising a slotted rod having multiple ribs for forming multiple slotted grooves and multiple optical fiber core wires accommodated in the slotted grooves, where the number of the slotted grooves is 3 or 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to slotted fiber optic cables. [Background technology]

[0002] Patent Document 1 discloses a slotted optical fiber cable having six slot grooves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-204687 Summary of the Invention [Problem to be solved by the invention]

[0004] The slotted optical fiber cable disclosed in Patent Document 1 includes a slot rod (also called a spacer) with six slot grooves formed therein, and the slot grooves are divided by ribs. Since the ribs are usually uniformly arranged in the circumferential direction in a cross-sectional view, bending anisotropy (presence or absence of an easy-to-bend direction) is unlikely to occur. However, the presence of the ribs makes it difficult to increase the packaging density of the optical fibers.

[0005] An object of the present disclosure is to provide a slotted optical fiber cable that can package optical fibers at high density while suppressing bending anisotropy. [Means for solving the problem]

[0006] In order to achieve the above object, a slotted optical fiber cable according to one aspect of the present invention comprises: a slotted rod having a plurality of ribs for forming a plurality of slotted grooves; a plurality of optical fiber cores housed in the slot grooves; a tape wound around the slot rod; The number of the slot grooves is 3 or 4, The thickness of the tip of the rib is thinner than the thickness immediately below the base of the rib, The rib Including the root of the rib Includes straight sections where the thickness does not change, Each of the slot grooves accommodates 800 or more of the optical fiber core wires, When viewed in cross section, the optical fiber core is arranged in a central region surrounded by the ribs and a line formed by connecting the vertices of adjacent ribs among the multiple ribs, and in an outer edge region located between the line and the holding winding tape. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a slotted optical fiber cable that can mount optical fibers at high density while suppressing bending anisotropy. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a slotted optical fiber cable according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Description of Embodiments of the Present Disclosure) First, embodiments of the present disclosure will be listed and described. A slotted optical fiber cable according to one aspect of the present disclosure includes: (1) a slot rod having a plurality of ribs for forming a plurality of slot grooves; a plurality of optical fiber cores housed in the slot grooves; a tape wound around the slot rod; The number of the slot grooves is 3 or 4, The thickness of the tip of the rib is thinner than the thickness immediately below the base of the rib, The rib Including the root of the rib Includes straight sections where the thickness does not change, Each of the slot grooves accommodates 800 or more of the optical fiber core wires, When viewed in cross section, the optical fiber core is arranged in a central region surrounded by the ribs and a line formed by connecting the vertices of adjacent ribs among the multiple ribs, and in an outer edge region located between the line and the holding winding tape. According to this configuration, the slotted optical fiber cable includes a slot rod having a plurality of ribs that form slot grooves in which a plurality of optical fiber cores are housed, and the number of the slot grooves is three or four. Thus, since the slotted optical fiber cable according to the above configuration has a relatively small number of slot grooves, the slot rod also has a relatively small number of ribs. Therefore, the slotted optical fiber cable according to the above configuration has a relatively large space for housing optical fiber cores, and more optical fiber cores can be housed in the slot rod. Meanwhile, since the number of slot grooves is three or four and the number of ribs is also three or four, which is more than two, bending anisotropy is small. Therefore, the slotted optical fiber cable according to the above configuration can package optical fibers at a high density while suppressing bending anisotropy. Furthermore, according to this configuration, optical fiber cores are also arranged in the outer edge region, and therefore the slotted optical fiber cable according to the above configuration can also package optical fibers at a high density.

[0011] In addition, in a slotted optical fiber cable according to one aspect of the present disclosure, ( 2 ) The Young's modulus of the material forming the slot rod may be 0.6 GPa or more and 1.8 GPa or less. According to this configuration, although the number of ribs is relatively small at 3 or 4, the Young's modulus of the material forming the slot rod is 0.6 GPa or more and 1.8 GPa or less, so that an appropriate rigidity for an optical fiber cable can be obtained.

[0012] In addition, in a slotted optical fiber cable according to one aspect of the present disclosure, ( 3) a tensile strength member disposed at the center of the slotted rod; Body Further preparation, When the length of the rib in the thickness direction is a and the length from the part of the rib that contacts the holding winding tape to the base of the rib is b, the value of a / b is 0.1 or more and may be smaller than 0.25. According to this configuration, the ribs have a thin thickness while still having appropriate mechanical strength, so that optical fibers can be mounted at a high density while maintaining strength.

[0014] (Details of the embodiments of the present disclosure) Specific examples of slotted fiber optic cables according to embodiments of the present disclosure are described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0015] A slotted optical fiber cable 1 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view of the slotted optical fiber cable 1.

[0016] 1, the slotted optical fiber cable 1 includes a slotted rod 2, a holding winding tape 3, and a cable jacket 4. The slotted optical fiber cable 1 has an outer diameter of, for example, 24.5 mm. The slotted optical fiber cable 1 has a structure in which a plurality of slot grooves 21 are radially provided in the slotted rod 2 having a tensile strength member 23 at the center. The plurality of slot grooves 21 may be provided in a twisted shape, such as a spiral or SZ shape, in the longitudinal direction of the slotted optical fiber cable 1.

[0017] The tension member 23 is formed, for example, from fiber reinforced plastic (FRP). Examples of fiber reinforced plastic include aramid FRP, glass FRP, and carbon FRP. The tension member 23 may also be formed from a liquid crystal polymer. It is preferable that the tension member 23 is non-inductive. The tension member 23 has a circular shape in cross section.

[0018] Each slot groove 21 accommodates a plurality of optical fiber ribbons 10 that have been rolled up from a parallel state into a densely packed state. A pressure winding tape 3 is wound around the slot rod 2. A cable jacket 4 is formed around the pressure winding tape 3.

[0019] The slotted rod 2 is formed of, for example, a resin having a Young's modulus of 0.6 GPa or more and 1.8 GPa or less at room temperature. Examples of such resins include general-purpose polyethylene and hard polyethylene. The slotted rod 2 has a plurality of ribs 22 for forming a plurality of slot grooves 21. In this embodiment, the slotted rod 2 has four ribs 22 (a first rib 221, a second rib 222, a third rib 223, and a fourth rib 224), and the four ribs 22 are, for example, regularly arranged at 90-degree intervals around the tensile strength member 23. Therefore, the slotted optical fiber cable 1 is a four-groove slotted optical fiber cable having four slot grooves 21. Each slot groove 21 accommodates, for example, 144 optical fiber ribbons 10.

[0020] The optical fiber ribbon 10 includes, for example, 12 optical fibers. The outer diameter of the optical fibers is relatively thin, for example, between 170 μm and 200 μm. The 12 optical fibers are arranged in parallel in a direction perpendicular to the longitudinal direction. At least some adjacent optical fibers in the optical fiber ribbon 10 are intermittently provided in the longitudinal direction of the optical fiber with connected portions where the adjacent optical fibers are connected and non-connected portions where the adjacent optical fibers are not connected. In this embodiment, connected portions and non-connected portions are provided intermittently every two fibers in the longitudinal direction of the optical fiber. The non-connected portions are formed, for example, by cutting a portion of the connecting resin used to form the connected portions with a rotary blade or the like.

[0021] In this embodiment, 1728 optical fiber cores are housed in each slot groove 21. Therefore, the slotted optical fiber cable 1 has 6912 optical fiber cores.

[0022] The first rib 221 has vertices 220A and 220B, the second rib 222 has vertices 220C and 220D, the third rib 223 has vertices 220E and 220F, and the fourth rib 224 has vertices 220G and 220H. The vertices 220A to 220H are corners of each rib 22 and correspond to the points where the rib 22 contacts the holding winding tape 3. Here, the area surrounded by lines L1 to L4 formed by connecting the vertices of adjacent ribs 22 in the circumferential direction (vertices 220B and 220C, 220D and 220E, 220F and G, and 220A and 220H) among the multiple ribs 22 and the ribs 22 is referred to as the central region CR. The area between the lines L1 to L4 and the holding winding tape 3 is referred to as the outer edge region OR. The optical fiber ribbon 10 is disposed in both the central region CR and the outer edge region OR. That is, optical fibers are disposed in both the central region CR and the outer edge region OR.

[0023] The holding and winding tape 3 may be, for example, a polyethylene terephthalate (PET) tape, or a tape formed by bonding a base material such as PET to a nonwoven fabric. Note that a water absorbing agent (for example, water absorbing powder) may be applied to the inside of the holding and winding tape 3.

[0024] The cable jacket 4 is made of a thermoplastic resin such as polyethylene (PE). The cable jacket 4 contains, for example, a silicone-based lubricant. The cable jacket 4 is formed by extrusion molding a resin around the slot rod 2 around which the pressure winding tape 3 is wound and the plurality of optical fiber ribbons 10. The thickness of the cable jacket 4 is, for example, 1.2 mm to 1.8 mm.

[0025] Next, examples of the present embodiment will be described, but the present disclosure is not limited to the following examples.

[0026] By varying the shape of the rib 22 (thickness and height of the rib 22), the temperature characteristics of the slotted optical fiber cable 1 and whether the rib 22 provided on the slotted optical fiber cable 1 deformed (also known as rib collapse) during slot rod manufacturing or during the mechanical test described below were compared.

[0027] Table 1 shows the thickness a and height b of the rib 22, the evaluation of the temperature characteristics, and whether the rib collapsed. As shown in FIG. 1, the thickness a of the rib 22 is the length of the rib 22 in the thickness direction at the base position P1 of the rib 22. Position P1 is the boundary between the bottom 210 of the slot groove 21 and the straight portion 211 of the rib, and is the base position of the portion (straight portion of the rib) 211 that extends radially outward from the bottom 210 in a straight line or in a manner that approximates a straight line. The height b of the rib 22 is the length from the tip position P2 of the rib 22 (the position where the length of the rib 22 is the longest) to position P1. The temperature characteristics were evaluated by measuring the loss when subjected to a temperature cycle from -40°C to +70°C in a drum state or in a state simulating installation. A Δα (loss variation during the test) of 0.3 dB / km or less was evaluated as "good" (grade A), and otherwise a "poor" (grade B). Rib collapse was evaluated during slotted rod manufacturing and all mechanical tests (bending, lateral pressure, and impact tests). Rib collapse was evaluated as "good" if the rib collapse angle was 10 degrees or less, and "bad" if it was greater than 10 degrees. The rib collapse angle is the angle between the center line of the slotted rib in its original position and the center line of the collapsed slotted rib. In the bending test, slotted optical fiber cable 1 was wound around a 600 mm diameter mandrel while reversing the winding direction. The sample was wound and released 10 times, and the increase in transmission loss was measured to be 0.15 dB or less. In the lateral pressure test, a pressure of 2200 N / 100 mm was applied to slotted optical fiber cable 1, and the increase in transmission loss was measured to be 0.15 dB or less after 11 minutes of application of pressure. In the impact experiment, a roughly rectangular parallelepiped weight weighing 1.5 kg was dropped from a height of 60 cm onto the slotted optical fiber cable 1, and it was measured whether the increase in transmission loss was 0.15 dB or less. [Table 1]

[0028] First, experimental examples 1 to 5 will be described. In experimental examples 1 to 5, the height b of the rib 22 was 10 mm in all cases, but the thickness a of the rib 22 was different for each case, and therefore the value of a / b was also different for each case. The slotted optical fiber cables 1 according to experimental examples 1 to 4 were given an A rating because the increase in transmission loss was 0.3 dB / km or less in the temperature characteristic experiment. On the other hand, the slotted optical fiber cable 1 according to experimental example 5 was given an A rating because the increase in transmission loss was greater than 0.3 dB / km in the temperature characteristic experiment. Furthermore, in the slotted optical fiber cables 1 according to experimental examples 2 to 5, no rib collapse occurred during mechanical testing during slot rod manufacturing, but rib collapse occurred in the slotted optical fiber cable 1 according to experimental example 1.

[0029] Next, experimental examples 6 and 7 will be described. In experimental examples 6 and 7, the height b of the rib 22 was 7 mm in both cases, but the thickness a of the rib 22 was different, and therefore the value of a / b was also different. In the temperature characteristic experiment, the slotted optical fiber cables 1 according to experimental examples 6 and 7 showed an increase in transmission loss of 0.3 dB / km or less, and were therefore rated A. Furthermore, in the slotted optical fiber cables according to experimental examples 6 and 7, no rib collapse occurred during mechanical testing during slot rod manufacturing.

[0030] From these results, it was confirmed that when the value of a / b is 0.25 or more, the optical fiber density increases and the temperature characteristics deteriorate. It was also confirmed that when the value of a / b is less than 0.1, the mechanical strength of the slotted optical fiber cable 1 decreases and rib collapse occurs. Therefore, it was confirmed that the slotted optical fiber cable 1 designed so that the value of a / b is 0.1 or more and less than 0.25 has a mechanical strength that does not cause rib collapse and can pack optical fibers at a high density.

[0031] According to the slotted optical fiber cable 1 described above, the slotted optical fiber cable 1 has four slot grooves 21, which is relatively small, and therefore the slotted rod 2 also has four ribs 22, which is relatively small. Therefore, the space that can accommodate optical fiber core wires in the slotted optical fiber cable 1 is relatively large. Therefore, the slotted optical fiber cable 1 can accommodate more optical fiber core wires in the slotted rod 2. On the other hand, since the number of slot grooves 21 is four and the number of ribs is also four, which is more than two, bending anisotropy is small. According to the slotted optical fiber cable 1, optical fibers can be packed at a high density while maintaining strength.

[0032] Furthermore, according to the slotted optical fiber cable 1, each slot groove 21 can accommodate 1728 cores, a relatively large number of optical fiber cores, ie, 800 cores or more.

[0033] Furthermore, although the slotted optical fiber cable 1 has a relatively small number of ribs 22 at four, the slotted rod 2 is formed from a resin having a Young's modulus of 0.6 GPa or more and 1.8 GPa or less at room temperature, and therefore has appropriate rigidity for an optical fiber cable.

[0034] Furthermore, according to the slotted optical fiber cable 1, the thickness b of the rib 22 is thin while having appropriate mechanical strength, so that optical fibers can be packed at high density while suppressing bending anisotropy.

[0035] Furthermore, according to the slotted optical fiber cable 1, optical fibers are arranged also in the outer edge region OR, so that optical fibers can be packaged at a high density.

[0036] Although the present disclosure 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 disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure.

[0037] In the above embodiment, the slotted optical fiber cable 1 has four slot grooves 21, but it may have three slot grooves 21.

[0038] In the above embodiment, each slot groove 21 accommodates 1728 optical fiber cores, but the number of optical fiber cores accommodated in the slot groove 21 may be 800 or more and is not limited to 1728.

[0039] In the above embodiment, the rib 22 is partially curved, but it may be curved entirely. Even if the entire rib 22 is curved, the height and thickness of the rib can be determined by linearly approximating the rib portion. [Explanation of symbols]

[0040] 1: Slotted fiber optic cable 2: Slot rod 3: Press-down tape 4: Cable sheath 10: Optical fiber ribbon 21: Slot groove 22: Rib 23: Tensile strength body 210: Bottom 211: Straight part of rib 220A, 220B, 220C, 220D, 220E, 220F, 220G, 220H: Apex 221: First Rib 222: Second Rib 223: Third Rib 224: Fourth Rib a: Rib thickness b: Rib height CR: Central area L1, L2, L3, L4: Lines OR: outer edge region P1: Root position P2: Tip position

Claims

1. a slotted rod having a plurality of ribs for forming a plurality of slotted grooves; a plurality of optical fiber cores housed in the slot grooves; a tape wound around the slot rod; The number of the slot grooves is 3 or 4, The thickness of the tip of the rib is thinner than the thickness immediately below the base of the rib, The rib includes a straight portion including a root of the rib, the thickness of which does not change, Each of the slot grooves accommodates 800 or more of the optical fiber core wires, A slotted optical fiber cable in which, when viewed in cross section, the optical fiber core wires are arranged in a central region surrounded by the ribs and a line formed by connecting the vertices of adjacent ribs among the multiple ribs, and in an outer edge region located between the line and the holding winding tape.

2. 2. The slotted optical fiber cable according to claim 1, wherein the Young's modulus of the material forming the slot rod is 0.6 GPa or more and 1.8 GPa or less.

3. Further, a tension member is provided at the center of the slot rod, A slotted optical fiber cable as described in claim 1 or claim 2, wherein the value of a / b is 0.1 or more and less than 0.25, when the thickness direction length of the rib is a and the length from the part of the rib that contacts the holding winding tape to the base of the rib is b.

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