Patent Application
20250138268
The present disclosure relates to an optical cable and a method for manufacturing the optical cable.
For example, Patent Literature 1 discloses a unidirectional stranded slot-less optical cable in which polarization mode dispersion (PMD) is reduced. Patent Literature 2 discloses an SZ-stranded slot-less optical cable in which PMD is reduced. In Patent Literatures 1 and 2, PMD is reduced by setting a twist ratio of a strand, which is a twist amount per unit length of a strand of an optical fiber, to a certain value or more.
A slot-less optical cable including:
A method for manufacturing a slot-less optical cable that includes a plurality of optical fiber units each including a plurality of optical fibers, and a cable sheath covering the plurality of optical fiber units, the method including:
In a slot-less optical cable formed by stranding a plurality of optical fibers, in a case where the plurality of optical fibers are in a form of an optical fiber ribbon, when a twist ratio of the strand of the optical fibers is large, a bending tendency of a ribbon increases, and there is a concern that melting workability decreases. In Patent Literature 1, it is preferable that the twist ratio of the strand is 0.0104 (rad/mm) or more. However, when the twist ratio is too large, there is a possibility that the melting workability is deteriorated.
An object of the present disclosure is to provide an optical cable and a method for manufacturing the optical cable, which are capable of reducing PMD to a low level without deteriorating melting workability.
According to the present disclosure, it is possible to provide an optical cable and a method for manufacturing the optical cable, which are capable of reducing PMD to a low level without deteriorating melting workability.
An overview of an embodiment of the present disclosure will be described.
(1) A slot-less optical cable includes:
According to the above configuration, when the twist ratio of the stranding of the plurality of optical fiber units is at least partially set to 0.0014 (rad/mm) or more. PMD of the optical cable can be reduced to 0.1 ps/km1/2 or less without being greatly twisted. In addition, with such a degree of the twist ratio, a bending tendency of the plurality of optical fibers increases, and thus melting workability does not decrease.
The twist ratio is a maximum value of a twist amount per unit length of the optical fiber unit, and is, for example, a maximum value (maximum angle) when a twist amount (angle) of the unit is measured every 1 cm by peeling off a sheath in a range of 1 m.
(2) In the optical cable according to item (1), the plurality of optical fibers include optical fibers having an outer diameter of 220 μm or less, and the plurality of optical fibers form an optical fiber ribbon with fiber adhesive parts and non-adhesive parts in which, a coupling portion and a non-coupling portion are intermittently provided in the longitudinal direction in a state where the plurality of optical fibers are arranged in parallel in a direction orthogonal to the longitudinal direction, the coupling portion being a state where adjacent optical fibers of some or all of the plurality of optical fibers are coupled, the non-coupling portion being a state where the adjacent optical fibers are not coupled.
According to the above configuration, even when the plurality of optical fibers are accommodated at a high density, an increase in transmission loss is unlikely to occur, and when the optical fibers are taken out, a single fiber separation operation is easily performed.
(3) In the optical cable according to item (1) or (2), an upper limit value of the twist ratio is 0.0100 (rad/mm) or less.
According to the above configuration, it is possible to prevent a decrease in melting workability due to an increase in the bending tendency of the plurality of optical fibers.
(4) In the optical cable according to item (3), the plurality of optical fiber units are stranded back in the stranding direction.
According to the above configuration, it is possible to eliminate the twist of each optical fiber occurring when the plurality of optical fiber units are stranded.
(5) In a method for manufacturing a slot-less optical cable that includes a plurality of optical fiber units each including a plurality of optical fibers, and a cable sheath covering the plurality of optical fiber units, the method includes:
According to the above method, in the step of stranding the plurality of optical fiber units, the twist ratio of the stranding of the plurality of optical fiber units is at least partially set to 0.0014 (rad/mm) or more, and thus it is possible to manufacture an optical cable in which PMD is reduced to 0.1 ps/km1/2 or less.
(6) In the method for manufacturing an optical cable according to item (5), in the step of stranding, an upper limit value of the twist ratio is set to 0.0100 (rad/mm) or less.
According to the above method, it is possible to manufacture an optical cable that reduces a decrease in melting workability due to an increase in the bending tendency of the plurality of optical fibers.
(7) In the method for manufacturing an optical cable according to any one of items (1) to (6), the step of stranding includes a step of stranding back the plurality of optical fiber units in the stranding direction.
According to the above method, it is possible to manufacture an optical cable in which the twist of each optical fiber occurring when the plurality of optical fiber units are stranded is eliminated.
Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Members having the same reference numerals as those members already described in description of the present embodiment will not be described for convenience of description. Dimensions of the members shown in the drawings are for convenience of description and may be different from actual dimensions of the members.
The optical fiber unit 2 includes a plurality of optical fibers. An outer diameter of glass fibers provided in the plurality of optical fibers is, for example, 125 μm. An outer diameter of the optical fiber is, for example, any one of 165 μm, 200 μm, 220 μm, and 250 μm.
The water absorbing ribbon 3 is wrapped around the entire periphery of the plurality of optical fiber units 2, for example, longitudinally or helically. The water absorbing ribbon 3 is, for example, a ribbon subjected to water absorption processing by applying a water absorption powder to a base fabric made of polyester or the like.
The cable sheath 4 covers the periphery of the water absorbing ribbon 3. The cable sheath 4 is made of, for example, a resin such as polyvinyl chloride (PVC) or polyethylene (PE), and is formed by extrusion-molding the resin on the plurality of optical fiber units 2 around which the water absorbing ribbon 3 is wound.
The tensile strength members 5 are embedded in the cable sheath 4. The tensile strength members 5 are made of fiber reinforced plastic (FRP) such as aramid FRP, glass FRP, or carbon FRP. The tensile strength members 5 may be formed of a liquid crystal polymer.
The tensile strength members 5 are formed in a circular shape, in a cross-sectional view. Two tensile strength members 5 are provided inside the cable sheath 4 along a longitudinal direction of the optical cable 1.
The tear strings 6 are for tearing the cable sheath 4, and is embedded in the cable sheath 4 along the longitudinal direction of the optical cable 1. In this example, two tear strings 6 are provided. The two tear strings 6 face each other at substantially intermediate positions of the two tensile strength members 5. By pulling out the tear strings 6, the cable sheath 4 is torn in the longitudinal direction, and the optical fiber unit 2 can be taken out. The tear strings 6 are made of, for example, a plastic material (for example, polyester) resistant to tension.
The plurality of optical fibers provided in the optical fiber unit 2 form a plurality of optical fiber ribbons 10. The plurality of optical fiber ribbons 10 are assembled in a bundled state or stranded state.
The optical fiber unit 2 may not be in the form of an optical fiber ribbon, and may be an assembly of single optical fibers.
The optical fiber ribbons 10 in the optical fiber unit 2 may be stranded or may be stranded back.
As shown in
As shown in
In the present embodiment, the twist ratio of the stranding of the plurality of optical fiber units 2 is at least partially 0.0014 (rad/mm) or more. Accordingly, the PMD of the optical cable can be reduced to 0.1 ps/km1/2 or less.
A method for manufacturing the optical cable according to the present embodiment will be described. The plurality of optical fiber units 2 are stranded while periodically reversing the stranding direction along the longitudinal direction of the optical cable. When the plurality of optical fiber units 2 are stranded, the twist ratio is at least partially set to 0.0014 (rad/mm) or more. Thereafter, the water absorbing ribbon 3 is longitudinally or helically wrapped around the periphery of the stranded plurality of optical fiber units 2, and the periphery thereof is covered with the cable sheath 4. In the stranding step, the twist ratio of the stranding of the plurality of optical fiber units 2 is at least partially set to 0.0014 (rad/mm) or more, and thus it is possible to manufacture an optical cable in which the PMD is reduced to 0.1 ps/km1/2 or less.
Further, in the step pf stranding, the twist ratio may be set to 0.0100 (rad/mm) or less. Accordingly, it is possible to manufacture the optical cable 1 that reduces a decrease in melting workability due to an increase in the bending tendency of the plurality of optical fibers.
The “0.0100 (rad/mm) or less” means that the upper limit value of the twist ratio is 0.0100 (rad/mm), and means that the twist ratio does not exceed 0.0100 (rad/mm) even in a part.
Table 1 shows evaluation results of the PMD of the optical cable 1 according to the present disclosure. In optical cable samples to be evaluated, an optical fiber having an outer diameter of 200 μm and an optical fiber ribbon with fiber adhesive parts and non-adhesive parts are used. In samples 1 to 5, a strand angle for each pitch between optical fiber units is changed to change a twist ratio.
In Table 1, “strand back of ribbon” indicates strand back of the optical fiber ribbon in the optical fiber unit, “stranding direction” indicates a stranding direction of the optical fiber units, and “twist ratio” indicates a twist ratio of the optical fiber units. The twist ratio is a twist ratio measured in a part of the optical cable 1. The SZ-stranding of the optical fiber ribbon in the optical fiber unit and the stranding back of the optical fiber units are performed in samples 1 to 5.
A plurality of optical cables of such samples are manufactured, the PMD is measured, and a maximum value of the PMD is shown in the table.
Even in the sample 5 without stranding back of the ribbon, similarly to the samples with stranding back, it is confirmed that the PMD is reduced to 0.1 ps/km1/2 or less by setting the twist ratio of the optical fiber units to 0.0014 (rad/mm) or more. However, since the twist occurs, when the twist ratio is too large, the melting workability may deteriorate. When the optical fiber units are spirally stranded, similarly to the case where the optical fiber units are SZ-stranded, it is expected that the PMD of the optical cable is reduced to 0.1 ps/km1/2 or less by setting the twist ratio to 0.0014 (rad/mm) or more.
As shown in Table 1, in a part of the optical cable 1, by setting the twist ratio of the stranding to 0.0014 (rad/mm) or more, the PMD of the optical cable 1 can be reduced to 0.1 ps/km1/2 or less. However, when the twist ratio is less than 0.0014 (rad/mm) in a part of the optical cable 1, the PMD cannot be set to 0.1 ps/km1/2 or less. When the twist ratio of the stranding is set to be larger than 0.0100 (rad/mm) in a part of the optical cable 1, the PMD is smaller, but the melting workability deteriorates. As described above, by setting the twist ratio of the stranding to 0.0100 (rad/mm) or less, it is possible to prevent a decrease in the melting workability due to an increase in the bending tendency of the plurality of optical fibers.
Although the embodiment of the present disclosure has been described above, it goes without saying that the technical scope of the present disclosure should not be interpreted to be limited by the description of the present embodiment. The present embodiment is merely an example, and it is understood by those skilled in the art that various modifications to the present embodiment can be made within the scope of the invention described in the claims. As described above, the technical scope of the present disclosure should be defined based on the scope of the invention described in the claims and the scope of equivalents thereof.
The present application claims priority based on Japanese Patent Application No. 2021-210965 filed on Dec. 24, 2021, and incorporates all the contents described in the Japanese Application.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-210965 | Dec 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/047758 | 12/23/2022 | WO |
