Fiber optic cable

Abstract

To provide an optical fiber cable capable of attaining compatibility between optical characteristics and waterproofness in an optical fiber cable more properly than ever.SOLUTION: A slotless type optical fiber cable comprises an assembly core formed by collecting a plurality of optical fibers and a cable sheath provided on a periphery of the assembly core. A packaging density of the optical fibers is 53% or less, the packaging density being a ratio of a sectional area of the plurality of optical fibers to a sectional area of the assembly core. A pull-out force of the assembly core relative to the cable sheath is 3 N / 40 cm or more and 15 N / 40 cm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an optical fiber cable. [Background Art]

[0002] Patent Document 1 discloses an optical fiber cable including an optical fiber core wire, a buffer layer formed by gathering yarns around the optical fiber core wire, and a jacket provided outside the buffer layer. [Prior Art Document] [Patent Document]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-337581 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] By the way, optical characteristics and water resistance in an optical fiber cable have a trade-off relationship, and it is necessary to achieve both of them. In many cases, compatibility between optical characteristics and water resistance of an optical fiber cable is achieved by adjusting the mounting density, which is the ratio of the cross-sectional area of the optical fibers mounted in the aggregated core to the cross-sectional area of the aggregated core provided in the optical fiber cable. However, such adjustment of the mounting density may not be able to properly achieve both optical characteristics and water resistance in the optical fiber cable.

[0005] An object of the present disclosure is to provide an optical fiber cable that can more appropriately achieve both optical characteristics and water resistance in the optical fiber cable. [Means for Solving the Problem]

[0006] A slotless optical fiber cable according to one aspect of the present disclosure is an aggregated core in which a plurality of optical fibers are gathered, and a cable jacket provided around the aggregated core, The optical fiber mounting density, which is the ratio of the cross-sectional area of ​​the plurality of optical fibers to the cross-sectional area of ​​the aggregated core, is 53% or less. The pulling force of the bundled core against the cable sheath is 3N / 40cm or more and 15N / 40cm or less. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide an optical fiber cable that can more appropriately balance optical properties and waterproofness in an optical fiber cable. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of an optical fiber cable according to an embodiment of the present disclosure. [Figure 2] Figure 2 illustrates the relationship between implementation density and transmission loss value. [Figure 3] Figure 3 illustrates the relationship between tensile force and waterproofing. [Figure 4] Figure 4 illustrates the relationship between mounting density and pull-out force. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described. A slotless optical fiber cable according to one aspect of this disclosure is (1) A bundled core made up of multiple optical fibers, The assembly core comprises a cable sheath provided around it, The optical fiber mounting density, which is the ratio of the cross-sectional area of ​​the plurality of optical fibers to the cross-sectional area of ​​the aggregated core, is 53% or less. The pulling force of the bundled core against the cable sheath is 3N / 40cm or more and 15N / 40cm or less. With this configuration, by setting the optical fiber mounting density to 53% or less, transmission loss can be suppressed within an appropriate range, while the water flow velocity can be suppressed within an appropriate range by setting the pull-out force of the bundled core against the cable sheath to 3N / 40cm or more and 15N / 40cm or less. Therefore, the optical properties and waterproofness of the optical fiber cable with the above configuration can be more appropriately balanced.

[0010] (2) In the slotless optical fiber cable described in (1) above, the pull-out force may be 5N / 40cm or more and 10N / 40cm or less. With this configuration, by setting the pull-out force of the bundled core against the cable sheath, a parameter related to the water velocity, to 5N / 40cm or more and 10N / 40cm or less, it is possible to further enhance waterproofing while maintaining good optical properties.

[0011] [Details of the embodiments of this disclosure] Specific examples of optical fiber cables according to embodiments of this disclosure are described below with reference to the drawings. However, this disclosure is not limited to these examples and is intended to include all modifications within the meaning and scope of the claims as indicated by the claims.

[0012] As illustrated in Figure 1, the optical fiber cable 1 is a slotless cable. However, this disclosure is also applicable to slot-type cables having slot rods (also called spacers) capable of housing optical fiber cores. The optical fiber cable 1 comprises a bundled core 11 and a cable sheath 13 provided around the bundled core.

[0013] The assembled core 11 is, for example, circular. A plurality of optical fiber ribbons 10 are accommodated in the assembled core 11. In the optical fiber ribbon 10, 12 optical fiber fibers are rounded from a parallel state to be in a dense state. The optical fiber ribbon 10 may be a non-intermittent optical fiber ribbon in which all parallel optical fiber fibers are connected to each other, and includes a connection region where adjacent optical fiber fibers are connected to each other and an optical fiber. It may be an intermittent optical fiber ribbon constituted by a non-connection region where adjacent mutual fibers are separated. For example, 40 or more and 1000 or less optical fiber fibers are accommodated in the assembled core 11. That is, 40 or more and 1000 or less optical fiber fibers are collected in the assembled core 11. In the present embodiment, 1000 optical fiber fibers are accommodated in the assembled core 11. Further, in the present embodiment, a 12-fiber intermittent optical fiber ribbon is used, and a connection portion and a non-connection portion are intermittently provided in the longitudinal direction of the optical fiber fibers for every two fibers. A 2-fiber intermittent optical fiber ribbon is used. The non-connection portion is formed, for example, by cutting a part of the connection resin for forming the connection portion with a rotary blade or the like.

[0014] As illustrated in FIG. 1, the assembled core 11 is formed into a round shape by, for example, vertically or horizontally winding a bundle of a plurality of optical fiber ribbons 10 with a pressing wrapping tape 12. If the intermittent optical fiber ribbon 10 is used, transmission loss is less likely to increase even when deformed in the assembled core 11, so that optical fiber fibers can be assembled at high density while maintaining a small cable outer diameter.

[0015] In the present embodiment, the optical fiber mounting density, which is the ratio of the cross-sectional area of the plurality of optical fibers to the cross-sectional area of the assembled core 11, is 47% or more and 53% or less. The mounting density is obtained by dividing the cross-sectional area of the optical fibers mounted in the assembled core 11 by the cross-sectional area of the assembled core 11 up to the pressing wrapping tape 12.

[0016] The outer side of the press-wound tape 12 is covered with a cable jacket 13. The cable jacket 13 can be formed of, for example, polyethylene resin, flame-retardant polyethylene resin, polyvinyl chloride resin, or the like. In the cable jacket 13, two tensile strength members 14 for maintaining longitudinal strength and two tear cords 15 for tearing the cable jacket 15 in the longitudinal direction of the cable can be longitudinally inserted and embedded during extrusion molding of the cable jacket 13.

[0017] In the present embodiment, the pull-out force of the assembled core 11 with respect to the cable jacket 13, that is, the force required when pulling the assembled core 11 out of the cable jacket 13, is 3N / 40cm or more and 15N / 40cm or less, preferably 5N / 40cm or more and 10N / 40cm or less. It can be said that the higher the pull-out force, the higher the adhesion between the cable jacket 13 and the assembled core 11. Note that "pull-out force of 3N / 40cm" means that the maximum value of the force when pulling the assembled core 11 out of the cable jacket 13 in the optical fiber cable 1 having a length of 40 cm is 3N.

[0018] The tensile strength member 14 is formed of, for example, fiber reinforced plastic (FRP). Examples of the fiber reinforced plastic include aramid FRP, glass FRP, carbon FRP, and the like. Note that the tensile strength member 14 may be formed of a liquid crystal polymer. It is preferable that the tensile strength member 14 is non-inductive. The tensile strength member 14 has, for example, a circular shape in cross-sectional view.

[0019] The tear cords 15 are provided, for example, one on each side of the assembled core 11 at positions on a line orthogonal to a line connecting the centers of the two tensile strength members 14, with the assembled core 11 interposed therebetween. The tear cord 15 is, for example, a cord-like member having a circular cross section made of a resin material such as nylon or polyester. Note that in the present embodiment, two protrusions 16 are formed on the cable jacket 13 during extrusion molding so that the embedded positions of the tear cords 15 can be visually recognized from the outside. However, one or three or more protrusions 16 may be formed on the cable jacket 13, or no protrusion 16 may be formed.

[0020] The projections 16 are provided along the longitudinal direction of the optical fiber cable 1. Each projection 16 may be provided continuously or intermittently along the longitudinal direction. The surface 16a of the projection 16 in the direction of projection is curved.

[0021] [Relationship between implementation density and transmission loss] The higher the optical fiber mounting density, which is the ratio of the cross-sectional area of ​​multiple optical fibers to the cross-sectional area of ​​the bundled core 11, the more difficult it is for water to pass into the bundled core 11, thus improving waterproofing. However, this also increases lateral pressure, leading to an increase in transmission loss (an example of a value indicating optical characteristics). Therefore, the inventors measured the transmission loss using an OTDR (Optical Time Domain Reflectometer) while varying the mounting density to determine the range in which good optical characteristics can be maintained while maximizing the mounting density. In this embodiment, good optical characteristics were defined as occurring when the maximum transmission loss over the entire length of each core at a wavelength of 1.55 μm was less than 0.30 dB / km.

[0022] Figure 2 illustrates the relationship between implementation density and transmission loss. As illustrated in Examples 1 to 4 in Figure 2, the transmission loss was measured for multiple optical fiber cables 1 with varying optical fiber implementation densities. The transmission loss value on the vertical axis of Figure 2 represents the maximum transmission loss for each cable, and as mentioned above, a value of less than 0.30 dB / km is considered good. In each of the optical fiber cables 1 from Examples 1 to 4, 1000 optical fiber cores are housed in a bundled core 11, and the implementation density was changed by changing the cross-sectional area of ​​the bundled core 11. Of Examples 1 to 4, Examples 1 to 3, shown as circles in the graph of Figure 2, are optical fiber cables whose cable sheath 13 is made of flame-retardant polyethylene (FR), while Example 4, shown as a square, is an optical fiber cable whose cable sheath 13 is made of polyethylene (PE).

[0023] In the optical fiber cable of Example 1, with a mounting density of 51%, the maximum transmission loss was less than the good value of 0.30 dB / km, and there were 0 abnormal cores among the 1000 optical fiber cores housed in the bundled core 11. An abnormal core is defined as an optical fiber core in the cable that has a portion with high transmission loss (a step), or whose transmission loss is 0.30 dB / km or more along its entire length or in part. The number of abnormal cores indicates the number of optical fiber cores that became abnormal. "There were 0 abnormal cores" means that there were no abnormal cores. In the optical fiber cable of Example 2, with a mounting density of 53.5%, although the maximum transmission loss was less than the good value of 0.30 dB / km, 2 abnormal cores occurred among the 1000 optical fiber cores. Furthermore, in the optical fiber cable of Example 3, with a mounting density of 58%, the maximum transmission loss was 0.30 dB / km or more, which is a poor value, and 2 abnormal cores occurred among the 1000 optical fiber cores. In the optical fiber cable of Example 4, which had a mounting density of 55%, the maximum transmission loss was less than the good value of 0.30 dB / km, but 24 out of 1000 optical fiber cores were abnormal. From the above, it was confirmed that an optical fiber mounting density, which is the ratio of the cross-sectional areas of multiple optical fibers to the cross-sectional area of ​​the aggregated core 11, is preferable as it does not result in abnormal cores. However, since high density cannot be achieved if the mounting density is less than 40%, it is preferable that the mounting density be 40% or higher.

[0024] [Relationship between tensile strength and waterproofing] Next, the inventors focused on the fact that the lower the pull-out force, the easier it is for water to pass through the bundled core 11, and the higher the water velocity. They then evaluated the waterproofness of the optical fiber cable 1 by measuring the water velocity. In this embodiment, waterproofness was considered good when the water velocity was less than 0.17 m / h. Water flow velocity refers to the speed at which water penetrates the optical cable when it is injected into the cable from a height of 1 meter.

[0025] Figure 3 illustrates the relationship between pull-out force and waterproofness. In Figure 3, the results of measuring the pull-out force and water flow velocity are plotted for optical fiber cables 1 of Examples 1 to 4, in which the optical fiber mounting density shown in Figure 2 is varied. In this example, the pull-out force was measured as the maximum force when pulling the bundled core 11 from the cable sheath 13 over a length of 40 cm. As a result, as shown in Figure 3, in the optical fiber cable of Example 1, where the pull-out force of the bundled core 11 against the cable sheath 13 was 7.7 N / 40 cm, the water flow velocity was 0.065 m / h, indicating good waterproofing. On the other hand, in the optical fiber cable of Example 2, where the pull-out force was 2.8 N / 40 cm, the water flow velocity was 0.17 m / h, indicating poor waterproofing. Furthermore, in the optical fiber cable of Example 3, where the pull-out force was 15.2 N / 40 cm, the water flow velocity was 0.125 m / h, indicating good waterproofing. In the optical fiber cable of Example 4, where the pull-out force was approximately the same as in Example 3 at 14.8 N / 40 cm, the water flow velocity was 0.092 m / h, indicating good waterproofing. Thus, among the optical fiber cables of Examples 1 to 4, the optical fiber cable of Example 2, which had a pull-out force of less than 3N / 40cm, had poor waterproofing characteristics, while the optical fiber cables of Examples 1, 3, and 4, which had a pull-out force of 3N / 40cm or more, were confirmed to have good waterproofing characteristics. From the above, it was confirmed that the pull-out force of the bundled core 11 against the cable sheath 13 is preferably between 3N / 40cm and 15N / 40cm. Furthermore, to ensure even better waterproofing characteristics, a pull-out force of 5N / 40cm or more is even more preferable.

[0026] Figure 4 illustrates the relationship between mounting density and pull-out force. In Figure 4, the pull-out force was measured for multiple optical fiber cables 1 with varying optical fiber mounting densities. As shown in Figure 4, there is a correlation between mounting density and pull-out force, and as shown in Figure 3, waterproofing can be achieved by adjusting the optical fiber mounting density so that the pull-out force falls within a predetermined desirable range (3N / 40cm to 15N / 40cm, more preferably 5N / 40cm to 10N / 40cm). On the other hand, as shown in Figure 2, if the mounting density is 53% or less, no abnormal cores will occur. Therefore, it was confirmed that by setting the mounting density and pull-out force within the shaded area of ​​Figure 4, it is possible to manufacture an optical fiber cable that satisfies both optical properties and waterproofing. As shown in Figure 4, when the pull-out force is 3N / 40cm, the mounting density is 47%. When the pull-out force is 5N / 40cm, the mounting density is 50%. When the pull-out force is 10N / 40cm, the mounting density is 53%. Therefore, it is preferable that the mounting density be 47% or more, more preferably 50% or more, and from the viewpoint of the transmission loss mentioned above, it is preferable that the pull-out force is 10N / 40cm (mounting density 53%).

[0027] With the optical fiber cable 1 described above, transmission loss can be suppressed within an appropriate range by setting the optical fiber mounting density to 53% or less, while the water flow velocity can be suppressed within an appropriate range by setting the pull-out force of the bundled core 11 against the cable sheath 13 to 3N / 40cm or more and 15N / 40cm or less. Therefore, with the optical fiber cable 1, optical properties and waterproofness can be better balanced.

[0028] Furthermore, according to the optical fiber cable 1, when the pull-out force of the bundled core 11 against the cable sheath 13, which is a parameter related to the water flow velocity, is between 5N / 40cm and 10N / 40cm, it is possible to further improve waterproofness while maintaining good optical characteristics.

[0029] Although this 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 this disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the embodiments described above and can be changed to a number, position, shape, etc. that is suitable for carrying out this disclosure. [Explanation of Symbols]

[0030] 1. Fiber optic cable 10 Fiber Optic Ribbons 11 Collective Core 12 tapes 13 Cable sheath 14 Tensile strength body 15 string 16 Protrusion 16a surface

Claims

1. A bundled core made up of multiple optical fibers, The assembly core comprises a cable sheath provided around it, The optical fiber mounting density, which is the ratio of the cross-sectional area of ​​the plurality of optical fibers to the cross-sectional area of ​​the aggregated core, is 47% or more and 51% or less. A slotless optical fiber cable in which the pull-out force of the bundled core against the cable sheath is 7.7 N / 40 cm or more and 15 N / 40 cm or less.

2. The slotless optical fiber cable according to claim 1, wherein the pull-out force is 7.7 N / 40 cm or more and 10 N / 40 cm or less.

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