Fiber optic cable

Abstract

This optical fiber cable 10 has optical fiber core wires 12, a sheath 11 that encloses and contains the optical fiber core wires 12 with an inside surface 11a, and a plurality of tensile bodies 13 that are embedded in the sheath 11 so as to extend along the optical fiber core wires 12. The plurality of tensile bodies 13 include two adjacent tensile bodies 13 that are arranged such that a plane 21, which is tangent to the two adjacent tensile bodies 13 and faces the optical fiber core wires 12 with the two adjacent tensile bodies 13 interposed therebetween, is tangent to the inside surface 11a of the sheath 11.

Description

Technical Field

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

Background Art

[0002] In the construction of an optical communication network, optical fiber cables are widely used. Patent Document 1 discloses an optical fiber cable in which optical fiber cores are bundled at a high density. A tensile strength member is provided on the outer jacket of the optical fiber cable to prevent breakage and suppress an increase in transmission loss. Note that, as shown in Patent Document 2, a plurality of tensile strength members may be used.

[0003] When taking out the optical fiber cores accommodated in an optical fiber cable, it is necessary to remove the outer jacket to expose the optical fiber cores. At this time, the removal of the outer jacket must be performed so as not to damage the optical fibers. In order to remove the outer jacket and take out the optical fiber cores, it is necessary to continuously tear the outer jacket in the longitudinal direction. In order to easily perform this operation, a tear string may be provided on the outer jacket (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, unlike tensile strength materials, tear strips do not contribute to the mechanical strength of the optical fiber cable. Therefore, areas of the sheath where tear strips are provided are more vulnerable to external forces than areas where tear strips are not provided. Furthermore, in order to ensure mechanical strength, the optical fiber cable must be able to withstand external forces in the radial direction of some cross-sections perpendicular to the longitudinal direction of the sheath.

[0006] This disclosure is made in view of the above circumstances and aims to provide an optical fiber cable that allows for easy extraction of the optical fiber core, does not damage the optical fiber core when the outer sheath is cut to extract the optical fiber core, and does not easily create vulnerable points in the outer sheath that are susceptible to external forces. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the optical fiber cable includes an optical fiber core, an outer sheath that surrounds and houses the optical fiber core on its inner surface, and a plurality of tensile strength members embedded in the outer sheath so as to extend along the optical fiber core, wherein the plurality of tensile strength members are in contact with two adjacent tensile strength members, and the planes facing the optical fiber core with the two adjacent tensile strength members interposed between them are in contact with the inner surface of the outer sheath.

[0008] Furthermore, the optical fiber cable includes an optical fiber core, a sheet surrounding the optical fiber core, an outer sheath that encloses and houses the optical fiber core on its inner surface via the sheet, and a plurality of tensile strength members embedded in the outer sheath so as to extend along the optical fiber core. The plurality of tensile strength members may include two adjacent tensile strength members that are in contact with each other, and the planes facing the optical fiber core with the two adjacent tensile strength members interposed between them are located in a range extending from the position in contact with the inner surface of the outer sheath to a position further advanced by the thickness of the sheet toward the optical fiber core.

[0009] Furthermore, the optical fiber cable includes an optical fiber core, an outer sheath that encloses and houses the optical fiber core on its inner surface, and a plurality of tensile strength members embedded in the outer sheath so as to extend along the optical fiber core. In a cross-section perpendicular to the longitudinal direction of the outer sheath, the axis that minimizes the second moment of the cross-section is in contact with two adjacent tensile strength members and is parallel to a plane facing the optical fiber core with these two adjacent tensile strength members interposed between them. This plane may include two adjacent tensile strength members in contact with the inner surface of the outer sheath. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide an optical fiber cable that allows for easy extraction of the optical fiber core, does not damage the optical fiber core when the outer sheath is cut to extract the optical fiber core, and does not easily create vulnerable points in the outer sheath that are susceptible to external forces. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing an optical fiber cable according to the first embodiment. [Figure 2] This is a cross-sectional view of the optical fiber cable in the first embodiment while the outer sheath is being trimmed. [Figure 3] Figure 2 shows a cross-sectional view after further trimming of the outer sheath of the optical fiber cable and removing two adjacent tensile strength members. [Figure 4] This is a cross-sectional overhead view showing a modified example of the optical fiber cable according to the first embodiment. [Figure 5] This is a cross-sectional view showing an optical fiber cable according to a second embodiment. [Figure 6] This is a partially enlarged cross-sectional view of the optical fiber cable according to the second embodiment. [Figure 7] This is a cross-sectional view showing an optical fiber cable according to a third embodiment. [Figure 8] This is a cross-sectional view showing a modified example of the optical fiber cable according to the third embodiment. [Modes for carrying out the invention]

[0012] Hereinafter, the optical fiber cable of the present embodiment will be described in order from the first embodiment to the fourth embodiment with reference to the drawings.

[0013] (First Embodiment) FIG. 1 is a cross-sectional view showing an optical fiber cable 10 of the first embodiment. The optical fiber cable 10 of the first embodiment includes an optical fiber core wire 12, an outer jacket 11 that surrounds the optical fiber core wire 12 and houses the optical fiber core wire 12 in a space 14 formed by an inner surface 11a, and a plurality of tensile strength members 13 embedded in the outer jacket 11 so as to extend along the optical fiber core wire 12.

[0014] The optical fiber core wire 12 is composed of one or a plurality of optical fiber core wires 12. The optical fiber core wire 12 may be a bundle of a plurality of optical fiber tapes in which a plurality of optical fiber core wires 12 are arranged in a tape shape. For example, an optical fiber tape composed of four optical fiber core wires 12 may be used, and six of these optical fiber tapes may be bundled to form the optical fiber core wire 12.

[0015] The outer jacket 11 is a tubular member having a substantially cylindrical shape with a predetermined inner diameter and outer diameter for the inner surface 11a and the outer surface 11b. The outer jacket 11 may be composed of a synthetic resin of polyolefin such as polyethylene (PE).

[0016] The tensile strength member 13 may be arranged at a substantially rotationally symmetric position with respect to the axis of the outer jacket 11 having a substantially cylindrical shape. The tensile strength member 13 may be composed of, for example, four tensile strength members 13. The tensile strength member 13 may extend along the optical fiber core wire 12 in the longitudinal direction of the outer jacket 11 and have a substantially cylindrical shape. The tensile strength member 13 may be composed of fiber-reinforced plastic (FRP) such as aramid fiber or glass fiber, or may be composed of a steel wire.

[0017] In the optical fiber cable 10 of the first embodiment, among the plurality of tensile strength members 13, the plane 21 that contacts the two tensile strength members 13 that face the optical fiber core wire 12 with two adjacent tensile strength members 13 interposed therebetween includes two adjacent tensile strength members 13 that contact the inner surface 11a of the outer sheath 11. The outer surface 11b of the outer sheath 11 of the optical fiber cable 10 may be processed with protrusions, markings, etc. so as to indicate the position of such a plane 21.

[0018] Using FIGS. 2 and 3, the process of extracting the optical fiber core wire 12 from the optical fiber cable 10 of the first embodiment will be described. FIG. 2 is a cross-sectional view when the outer sheath 11 of the optical fiber cable 10 of the first embodiment is being shaved. As shown in FIG. 2, the outer sheath 11 of the optical fiber cable 10 is shaved from the outer surface 11b with a blade toward the plane 21 that contacts the two tensile strength members 13 that face the optical fiber core wire 12 with two adjacent tensile strength members 13 interposed therebetween.

[0019] The position of such a plane 21 may be determined by referring to the processing such as protrusions and markings formed on the outer surface 11b of the outer sheath 11. Even when there is no processing on the outer surface 11b of the outer sheath 11 indicating the position of the plane 21, by shaving the outer sheath 11, the first tensile strength member 13 can be reached, and by shaving from different angles, the second adjacent tensile strength member 13 that contacts the common plane 21 can be reached.

[0020] When the outer sheath 11 is further shaved from FIG. 2, the plane 21 that contacts the two adjacent tensile strength members 13 and the inner surface 11a of the outer sheath 11 is reached. Since the tensile strength member 13 is harder than the outer sheath 11, when the blade hits the tensile strength member 13, it is transmitted to the operator's hand feeling, and it can be known that the blade has hit the tensile strength member 13. Also, by making the outer sheath 11 and the tensile strength member 13 have different colors, the operator can visually distinguish when shaving the outer sheath 11 and the tensile strength member 13 is exposed. When the operator knows that the tensile strength member 13 has been reached, the operation of shaving the outer sheath 11 is terminated, so the blade is not advanced to the inner surface 11a of the outer sheath 11. Therefore, the optical fiber core wire 12 is not damaged by the blade.

[0021] Figure 3 is a cross-sectional view of the optical fiber cable 10 after further trimming of the outer sheath 11 from the cross-sectional view of Figure 2, and removing two adjacent tensile strength members 13. Since the plane 21 is in contact with the two adjacent tensile strength members 13, the outer sheath 11 can be trimmed down to the plane 21 to expose and remove the two adjacent tensile strength members 13. Since the plane 21 is also in contact with the inner surface 11a of the outer sheath 11, when the two adjacent tensile strength members 13 are removed, the outer sheath 11 tears open along the longitudinal direction of the outer sheath 11 through which the optical fiber core wire 12 extends, forming a tear 16. The optical fiber core wire 12, housed in the space 14 formed by the inner surface 11a of the outer sheath 11, can be removed from the outer sheath 11 through the tear 16.

[0022] In the first embodiment, the optical fiber cable 10 allows for easy removal of the optical fiber core wire 12 housed in the space 14 formed on the inner surface 11a of the outer sheath 11 without damaging it, through the process described above. Therefore, a tearing string used to cut open the optical fiber cable 10 is not required when removing the optical fiber core wire 12 from the optical fiber cable 10. Furthermore, since the optical fiber cable 10 of the first embodiment does not have a tearing string, the mechanical strength of the outer sheath 11 is ensured. When the optical fiber cable 10 is laid inside or outside a building, it is more resistant to external forces, making it less susceptible to damage and allowing for continuous use over a long period, thus improving cost-effectiveness.

[0023] Figure 4 is a cross-sectional view showing a modified example of the optical fiber cable 10 of the first embodiment. As shown in Figure 4, in the modified example, the inner surface 11a of the outer sheath 11 is formed such that the thickness of the outer sheath 11 changes along the circumferential direction, which differs from the first embodiment in that the inner surface 11a of the outer sheath 11 had a generally cylindrical shape. Other configurations of the modified example are the same as those of the optical fiber cable 10 of the first embodiment.

[0024] As shown in Figure 4, in the modified example, the inner surface 11a of the outer sheath 11 may be formed such that the thickness of the outer sheath 11 is minimized at a position where the inner surface 11a is close to each tensile strength member 13. Alternatively, the inner surface 11a of the outer sheath 11 may be formed such that the thickness of the outer sheath 11 is minimized at a position where the inner surface 11a faces the optical fiber core 12 with two adjacent tensile strength members 13 interposed between them, and contacts the plane 21 that is in contact with the two tensile strength members 13 and the inner surface 11a of the outer sheath 11.

[0025] In the modified example, by following the steps shown in Figures 2 and 3, the outer sheath 11 is shaved with a cutting tool from the outer surface 11b toward the two adjacent tensile strength members 13 and the plane 21 in contact with the inner surface 11a of the outer sheath 11, the two adjacent tensile strength members 13 are removed, and the resulting slit 16 in the outer sheath 11 is opened, allowing the optical fiber core 12 housed in the space 14 formed on the inner surface 11a of the outer sheath to be removed from the outer sheath 11.

[0026] In the modified example, the inner surface 11a of the outer sheath 11 is formed such that the thickness of the outer sheath 11 changes in the circumferential direction of the inner surface 11a. This makes it possible to provide the outer sheath 11 with thicker sections. For example, at positions where the inner surface 11a is close to each tensile strength member 13, the thickness may be minimized because the strength is ensured by the tensile strength member 13. At positions where the inner surface 11a is in contact with the plane 21, the thickness may be minimized to reduce the amount of outer sheath 11 that needs to be removed to reach the plane 21. Other parts of the outer sheath 11 may have thicker sections. In this way, in the modified example, by providing the outer sheath 11 with thicker sections, the vulnerability of the entire optical fiber cable 10 to external forces can be improved. The same applies to the other embodiments described below.

[0027] (Second Embodiment) Figure 5 is a cross-sectional view showing the optical fiber cable 10 of the second embodiment. The optical fiber cable 10 of the second embodiment differs from the optical fiber cable 10 of the first embodiment shown in Figure 1 in that the optical fiber core 12 is surrounded by a sheet 15, the outer sheath 11 surrounds the optical fiber core 12 via the sheet 15, and the optical fiber core 12 surrounded by the sheet 15 is housed in a space 14 formed by the inner surface 11a. The sheet 15 may be made of, for example, a nonwoven fabric or a synthetic resin such as polyethylene terephthalate (PET).

[0028] Figure 6 is a partially enlarged cross-sectional view of the optical fiber cable 10 of the second embodiment. In the optical fiber cable 10 of the second embodiment, the plurality of tensile strength members 13 include two adjacent tensile strength members 13 that are in contact with each other, and the plane 21 that faces the optical fiber core 12 with the two adjacent tensile strength members 13 interposed between them is located in a range from the position where it contacts the inner surface 11a of the outer sheath 11 to a position further advanced by the thickness T of the sheet 15 toward the optical fiber core 12. The outer surface 11b of the outer sheath 11 of the optical fiber cable 10 may be processed with protrusions or markings to indicate the position of such plane 21. Other structures of the optical fiber cable 10 of the second embodiment are the same as those of the first embodiment.

[0029] The process of extracting the optical fiber core 12 from the optical fiber cable 10 in the second embodiment is the same as in the first embodiment described with reference to Figures 2 and 3. However, as shown in Figure 6, the optical fiber core 12 is surrounded by a sheet 15, and the sheet 15 has a thickness T. Therefore, the plane 21 that contacts the two adjacent tensile strength members 13 facing the optical fiber core 12, with the two tensile strength members 13 interposed between them, may extend from the position where it contacts the inner surface 11a of the outer sheath 11 to a position further advanced by the thickness T of the sheet 15 toward the optical fiber core 12. When the outer sheath 11 is shaved toward the optical fiber core 12, the precision of the position where the outer sheath 11 is shaved by a distance corresponding to the thickness T of the sheet 15 is relaxed.

[0030] In the second embodiment, the optical fiber cable 10 allows for easy removal of the optical fiber core wire 12 housed in the space 14 formed on the inner surface 11a of the outer sheath 11 without damaging it, through the process described above. Therefore, a tearing string used to cut open the optical fiber cable 10 when removing the optical fiber core wire 12 is not required. Furthermore, since the optical fiber cable 10 of the second embodiment does not have a tearing string, the mechanical strength of the outer sheath 11 is ensured. When the optical fiber cable 10 is laid inside or outside a building, it is more resistant to external forces, making it less susceptible to damage and allowing for continuous use over a long period, thus improving economic efficiency. Moreover, in the optical fiber cable 10 of the second embodiment, a displacement in the position where the outer sheath 11 is scraped by the thickness T of the sheet 15 is permitted, thus relaxing the strictness required during manufacturing.

[0031] (Third embodiment) Figure 7 is a cross-sectional view showing the optical fiber cable 10 of the third embodiment. The optical fiber cable 10 of the third embodiment differs from the optical fiber cable 10 of the first embodiment shown in Figure 1 in that, in a cross section perpendicular to the longitudinal direction of the outer sheath 11, the axis 22 that minimizes the second moment of the cross section is in contact with two adjacent tensile strength bodies 13 and is parallel to a plane 21 that faces the optical fiber core 12 with the two adjacent tensile strength bodies 13 interposed between them, and the plane 21 includes two adjacent tensile strength bodies 13 that are in contact with the inner surface 11a of the outer sheath 11. The other structures of the optical fiber cable 10 of the third embodiment are the same as those of the first embodiment.

[0032] The process of extracting the optical fiber core 12 from the optical fiber cable 10 in the third embodiment is the same as in the first embodiment described with reference to Figures 2 and 3. However, in a cross section perpendicular to the longitudinal direction of the sheath 11, a difference arises between the bending stiffness with respect to the plane containing the axis 22 where the second moment is minimized and the bending stiffness of the plane not containing the axis 22. That is, the bending stiffness with respect to the plane containing the axis 22 where the second moment is minimized is minimized. Here, the plane containing the axis 22 where the second moment is minimized is the plane containing the axis 22 and the longitudinal direction of the sheath 11, and the plane not containing the axis 22 is the plane containing the longitudinal direction of the sheath 11 but not the axis 22.

[0033] Therefore, an operator extracting the optical fiber core 12 from the optical fiber cable 10 can identify an axis 22 parallel to a plane 21 that minimizes the bending stiffness in a cross section perpendicular to the longitudinal direction of the optical fiber cable 10, is in contact with two adjacent tensile strength members 13, faces the optical fiber core 12 with the two adjacent tensile strength members 13 in between, and is in contact with the inner surface 11a of the outer sheath 11. By then cutting the outer sheath 11 toward this axis 22, the plane 21 in contact with the two adjacent tensile strength members 13 can be reached.

[0034] In the third embodiment, the optical fiber cable 10 allows for easy removal of the optical fiber core 12 housed in the space 14 formed on the inner surface 11a of the outer sheath 11 without damaging it, through the process described above. Therefore, a tearing string used to cut open the optical fiber cable 10 when removing the optical fiber core 12 is not required. Furthermore, since the optical fiber cable 10 of the third embodiment does not have a tearing string, the mechanical strength of the outer sheath 11 is ensured. When the optical fiber cable 10 is laid inside or outside a building, it is more resistant to external forces, making it less susceptible to damage and allowing for continuous use over a long period, thus improving cost-effectiveness. Moreover, in the optical fiber cable 10 of the third embodiment, based on the bending rigidity in a cross-section perpendicular to the longitudinal direction of the outer sheath 11, a plane 21 can be easily identified that is in contact with two adjacent tensile strength members 13, faces the optical fiber core 12 with the two adjacent tensile strength members 13 interposed, and is in contact with the inner surface 11a of the outer sheath 11. Therefore, there is no need to process the outer surface 11b of the outer sheath 11 with protrusions or markings to indicate the position of the plane 21, making it easier to manufacture the optical fiber cable 10. In addition, there is no need to shave off protrusions, reducing the burden. Furthermore, even when the optical fiber cable 10 is laid on a wall or road surface, for example, the direction in which the outer sheath can be scraped to extract the optical fiber core is not limited.

[0035] Figure 8 is a cross-sectional view showing a modified example of the optical fiber cable 10 of the third embodiment. As shown in Figure 8, in the modified example, six tensile strength members 13 are embedded in the outer sheath 11, which differs from the third embodiment in that four tensile strength members 13 are embedded in positions that are approximately rotationally symmetric with respect to the axis of the outer sheath 11, which has a generally cylindrical shape. The other configurations of the modified example are the same as those of the optical fiber cable 10 of the third embodiment.

[0036] In the modified example, the tensile strength members 13 are arranged such that, in a cross-section perpendicular to the longitudinal direction of the outer sheath 11, the axis 22 that minimizes the second moment of the cross-section is in contact with two adjacent tensile strength members 13, and is parallel to a plane 21 facing the optical fiber core 12 with the two adjacent tensile strength members 13 interposed between them, and the plane 21 has two adjacent tensile strength members 13 that are in contact with the inner surface 11a of the outer sheath 11. Therefore, the worker can identify the axis 22 by bending the optical fiber cable 10 in each direction and comparing the bending stiffness, and reach the plane 21 by cutting the outer sheath 11 toward this axis 22. In the modified example, the mechanical strength is reduced by using six tensile strength members 13, but the plane 21 in contact with the inner surface 11a of the outer sheath 11 can be easily identified based on the bending stiffness in a cross-section perpendicular to the longitudinal direction of the outer sheath 11. [Explanation of Symbols]

[0037] 10 Fiber optic cables 11 Outer cover 11a Inner surface of the outer covering 11b Outer surface of the outer covering 12 Optical fiber core 13 Tensile strength body 15 sheets

Claims

1. Optical fiber core and The optical fiber core is surrounded and housed on the inner surface, and the inner surface has a circular cross-sectional shape. Four or more tensile strength members embedded in the outer sheath so as to extend along the optical fiber core, Includes, Of the four or more tensile strength members mentioned above, four are laid at the vertices of a rectangle centered on the cross-sectional center of the inner surface. Of the four tensile strength members, the planes that are in contact with the outside of at least one pair of adjacent tensile strength members are arranged to be in contact with the inner surface of the outer covering. Fiber optic cable.

2. Optical fiber core and A sheet surrounding the optical fiber core, The optical fiber core is housed by surrounding it on the inner surface via the aforementioned sheet, and the inner surface has a circular cross-sectional shape. Four or more tensile strength members embedded in the outer sheath so as to extend along the optical fiber core, Includes, Of the four or more tensile strength members mentioned above, four are laid at the vertices of a rectangle centered on the cross-sectional center of the inner surface. Of the four tensile strength members, the planes that are in contact with the outside of at least one pair of adjacent tensile strength members are arranged to pass through the area from the inner surface of the outer covering to the inner surface of the sheet. Fiber optic cable.

3. Optical fiber core and The optical fiber core is surrounded and housed on the inner surface, and the inner surface has a circular cross-sectional shape. Four or more tensile strength members embedded in the outer sheath so as to extend along the optical fiber core, Includes, Of the four or more tensile strength members mentioned above, four are laid at the vertices of a rectangle centered on the cross-sectional center of the inner surface. Of the four tensile strength members, the planes tangent to the outside of at least one pair of adjacent tensile strength members are parallel to the axis that minimizes the second moment of the cross-section in a cross-section perpendicular to the longitudinal direction of the outer covering, and are arranged to be tangent to the inner surface of the outer covering. Fiber optic cable.

4. The optical fiber cable according to claim 1 or 2, wherein the outer surface of the outer sheath is processed to indicate a position of a plane that is in contact with the inner surface of the outer sheath.

5. The optical fiber cable according to any one of claims 1 to 3, wherein the tensile strength member has a different color from the outer sheath.

6. Optical fiber core and An outer sheath that surrounds and houses the optical fiber core on its inner surface, Multiple tensile strength members embedded in the outer sheath so as to extend along the optical fiber core, Includes, Of the plurality of tensile strength members, the planes that are in contact with the outside of at least one pair of adjacent tensile strength members are arranged to be in contact with the inner surface of the outer covering. The outer surface of the aforementioned outer covering has a circular cross-section, and the inner surface has minimal thickness at the point where it contacts the aforementioned plane. Fiber optic cable.

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