JP4205523B2 - Drop optical fiber cable - Google Patents

Description

  The present invention relates to an optical fiber cable. More particularly, the present invention relates to an optical fiber cable that can be easily separated in a drop optical fiber cable used for taking an optical fiber into a home or an indoor optical fiber cable used for handling in a home or a premises.

  In recent years, the construction of optical subscriber line networks has been progressing rapidly. 2. Description of the Related Art Conventionally, a drop optical fiber cable 11 as shown in FIG. 1 is used as a pull-in optical fiber cable for pulling into a home such as a home from a trunk optical fiber cable. Moreover, the indoor optical fiber cable 1 as shown in FIG. 2 is used for the inside and the premises of each home. 1 and 2, reference numeral 7 denotes an optical fiber cable main body, 5 denotes an optical fiber core wire, 4 denotes a strength member, 3 denotes a covering material, and 6 in FIG. 1 denotes a support wire. Further, as shown in FIG. 3, the optical fiber core wire may be a tape core wire 5 'in which a plurality of optical fibers are arranged in parallel and collectively coated to form a tape shape. The support wire 6 is for holding the optical fiber cable main body 7 and is connected to the optical fiber cable main body 7 by the covering material 3. In general, these optical fiber cables are formed with notches 8 and cuts along the longitudinal direction, and the optical fiber cables are cut from the notches 8 by human hands without using a special tool when laying. The convenience at the time of taking out the optical fiber core wire 5 inside the optical fiber cable main body 7 is achieved. As the covering material 3, polyvinyl chloride, polyethylene or the like is generally used. Examples of such a drop optical fiber cable include those disclosed in Patent Document 1 and Patent Document 2.

  Further, as shown in FIG. 4, a plurality of single optical fiber cores 5 are assembled, and the optical fiber cores 5 are protected from the external force applied to the optical fiber cable 30 by improving the separability of the assembled optical fiber cores 5. For this purpose, there is also known an optical fiber cable in which an interposition 9 made of a buffer material is provided and the outer periphery thereof is covered (see Non-Patent Document 1).

JP 2003-090943 A Japanese Patent Laid-Open No. 2003-140011 2002 IEICE Communication Society Proceedings B-10-11 “Examination of multi-core drop cable”

  Since an optical fiber cable is connected to an optical device at the time of laying, it is necessary to take out an internal optical fiber core separately for each single core or for each of a plurality of cores. However, when the coating material 3 is configured to contact almost the entire surface of the optical fiber core wire 5 as in the optical fiber cables 11 and 1 shown in FIGS. 1 and 2, the surface of the optical fiber core wire 5 and the coating are covered. It is difficult to separate the optical fiber core wire 5 from the covering material 3 due to the adhesive force and frictional force with the material 3.

  Further, when the tape core wire 5 'is employed as shown in FIG. 3, the tape core wire 5' can be separated from the covering material 3, or the internal optical fiber can be separated from the tape core wire 5 '. Have difficulty.

  When the interposition 9 is arranged around the optical fiber core 5 as shown in FIG. 4, the optical fiber core wire 5 is disposed while holding a certain amount of space in a state where the optical fiber core wire 5 is wrapped in the interposition 9. It is relatively easy to separate the optical fiber core wires 5. However, on the other hand, the optical fiber core wire 5 and the coating material 3 are caused by external force applied to the optical fiber cable 30 after installation, for example, expansion / contraction of the optical fiber cable due to temperature change in the installation environment, vibration due to wind, rain, and the like. It may move relatively. The movement of the optical fiber core wire 5 may cause distortion in the optical fiber, leading to an increase in transmission loss.

  The present invention has been made to solve the above-mentioned problems in optical fiber cables, and is an optical fiber cable that achieves both improvement in laying workability of the optical fiber cable and suppression of movement of the optical fiber core wire after laying. It is intended to provide.

In order to solve the above-described problems, a drop optical fiber cable according to the present invention has a plurality of optical fiber cores arranged adjacent to the outer periphery of the center tension member so as to surround the entire outer periphery of the center tension member, In the drop optical fiber cable in which a coating material is coated on the outer periphery of a plurality of optical fiber core wires, the coating material is composed of at least one of low density polyethylene, linear low density polyethylene, medium density polyethylene, and high density polyethylene, The optical fiber core is difficult to move with respect to the external force received by the drop optical fiber cable, maintains stable characteristics even after installation, and can be easily taken out without using a tool. for 70% more than 30% of the surface area of the optical fiber or less has to be in contact with the covering material, Serial dressing is extruded, on the side in contact with the central tension members of the optical fiber is characterized in that space is formed.

  According to the configuration of the present invention, it is possible to optimize the restraining force between the optical fiber core and the covering material, thereby achieving both improvement in installation workability and suppression of movement of the optical fiber core after installation. That is, when less than 30% of the surface area of the optical fiber core wire is in contact with the coating material, the binding force of the coating material on the optical fiber core wire such as adhesion and friction force is weakened, and the external force received by the optical fiber cable, etc. As a result, the optical fiber core wire moves. The moved optical fiber core is subjected to a compressive strain or a tensile strain inside the optical fiber cable and may cause an increase in transmission loss or disconnection. On the other hand, when 70% or more of the surface area of the optical fiber core is in contact with the coating material, the binding force of the coating material on the optical fiber core is too strong, and it is difficult to separate the optical fiber core from the coating material. Become.

  The best mode recognized by the inventors for carrying out the present invention will be described below. 5 and 6 are sectional views showing one embodiment of the present invention. In the optical fiber cable 1 of FIG. 5, 3 is a covering material, 4 is a tensile member, 4 'is a central tension member, and 5 is an optical fiber core. As the center tension member 4 ', high tensile strength fibers such as glass fibers and aromatic polyamide fibers can be used alone or in combination. Also, FRP rods made of high-strength fibers such as glass fibers and aromatic polyamide fibers, which are hardened with resin, steel wires, copper wires, and optical fibers whose outer diameters are adjusted as required are used alone or in combination. Can be used.

  For example, eight optical fiber cores 5 are arranged adjacent to the outer periphery of the center tension member 4 ′, and the outer side thereof is covered with the covering material 3. Here, as shown in the enlarged view of the vicinity of the optical fiber core in FIG. 7, a space 10 is formed on the side of the optical fiber core 5 in contact with the central tension member 4 ′. When all or part of the space 10 is covered with the covering material 3, the melt viscosity is adjusted by setting the temperature at the time of extrusion of the covering material 3, the extruder dies and nipples are designed, or the distance between the dies and nipples is adjusted. By doing so, the optical fiber cable 1 is formed without being filled with the covering material 3, that is, in a state where the optical fiber core wire 5 and the covering material 3 are not in contact with each other. In this embodiment, about 50% of the surface area of the optical fiber core wire 5 is in contact with the covering material 3 to form the optical fiber cables 11 and 1, and the binding force between the optical fiber core wire 5 and the covering material 3 is optimized. This improves both the workability of installation and the suppression of movement of the optical fiber after installation. In addition, as the coating | covering material 3, a low density polyethylene, a linear low density polyethylene, a medium density polyethylene, a high density polyethylene etc. can be used individually or in mixture as needed. In addition, a thermoplastic resin that has been subjected to flame retardant treatment in consideration of flame retardancy can also be used. Since drop optical fiber cables and indoor optical fiber cables are often used mainly in a customer's house, it is more preferable to use a thermoplastic resin that has been subjected to flame retardant treatment. Further, when it is necessary to adapt to the outdoor environment, additives such as carbon black, color pigments, antioxidants, ultraviolet inhibitors, and ultraviolet absorbers can be added as appropriate.

  The tensile body 4 can be used alone or in combination with high tensile fibers such as glass fibers and aromatic polyamide fibers in the same manner as the central tension member 4 '. Also, FRP rods made of high-strength fibers such as glass fibers and aromatic polyamide fibers, which are hardened with resin, steel wires, copper wires, and optical fibers whose outer diameters are adjusted as required are used alone or in combination. Can be used. Moreover, since the strength member 4 and the covering material 3 are brought into close contact with each other as needed, the strength member 4 can be coated with an adhesive or coated.

  The notch 8 is added to easily take out the optical fiber core wire 5 from the optical fiber cable 1 and is not essential to the present invention, but the covering material 3 is easily cut in the longitudinal direction of the optical fiber cable. Is possible and preferable.

  The optical fiber cable 11 shown in FIG. 6 has a configuration in which a support line 6 is added to the optical fiber cable 1 of FIG. 5 and is suitable when it is configured as a drop optical fiber cable mainly used for withdrawal into a subscriber's house. . The support wire 6 may be configured so as to be able to protect the optical fiber cable from the pulling tension at the time of laying the optical fiber cable and the external force received during the laying, for example, a single steel wire, a stranded steel wire, or glass High tensile strength fibers such as fibers and aromatic polyamide fibers, and FRP rods obtained by hardening these with resin are generally used. Moreover, it can also be used in combination with the above-described tensile body or center tension member as necessary. Furthermore, since the support wire 6 and the coating | covering material 3 are closely_contact | adhered as needed, it is also possible to coat or coat | cover the support wire 6 with an adhesive agent.

Examples of the present invention will be described below. In the optical fiber 1 whose cross section is shown in FIG. 5, the center of the optical fiber cable main body portion 7 of the optical fiber cable 1 is coated with an ultraviolet curable resin on the outer periphery of the optical fiber core wire having a diameter of 0.25 mm. A central tension member 4 ′ having a diameter of 4 mm was arranged, and eight optical fiber core wires 5 were gathered at a twist pitch of 200 mm on the outer periphery thereof. At this time, the adjacent optical fiber core wires 5 and the optical fiber core wire 5 and the center tension member 4 ′ are in contact with each other. Further, a galvanized single steel wire having a diameter of 0.4 mm as the strength member 4 is an optical fiber core assembled in an extruder nipple designed to be symmetrical with respect to the optical fiber core wire 5 in FIG. Set with line 5, center tension member 4 '. A cross section in which a flame retardant thermoplastic resin (manufactured by Nihon Unicar Co., Ltd .: NUC-9739) is extruded and coated as a coating material 3 with a 60 mm extruder, 3 mm in length, 4 mm in width and 0.3 mm in depth of notch 8 Examples (A), (C), and (E) having an optical fiber cable main body 7 having a shape were obtained. Moreover, the optical fiber cable 11 to which the support wire 6 shown in FIG. 6 was added was prepared as Examples (B), (D), and (F). The optical fiber cable 11 was prepared by simultaneously extruding a galvanized single steel wire having a diameter of 1.2 mm as a support wire 6 when forming the optical fiber cable 1 of the above-described embodiment. As will be described later in Table 1 together with various evaluations, in Examples (A) and (B), 30% of the surface area of the optical fiber core wire 5 was brought into contact with the coating material 3. In Examples (c) and (d), 50% of the surface area of the optical fiber core wire 5 was brought into contact with the coating material 3. In Examples (e) and (f), 70% of the surface area of the optical fiber core wire 5 was brought into contact with the coating material 3.

  As Comparative Examples (a) to (e), the following five types of optical fiber cables were prepared. In Comparative Example (a), the optical fiber cable 1 without the support wire 6 shown in FIG. 5 was used, and 20% of the surface area of the optical fiber core wire 5 was in contact with the coating material 3. In the comparative example (b), an optical fiber cable 11 to which the support wire 6 shown in FIG. 6 was added was used so that 20% of the surface area of the optical fiber core wire 5 was in contact with the coating material 3. In the comparative example (c), the optical fiber cable 1 without the support wire 6 shown in FIG. 5 was used, and 90% of the surface area of the optical fiber core wire 5 was in contact with the coating material 3. The comparative example (d) was an optical fiber cable 11 to which the support wire 6 shown in FIG. 6 was added, and 90% of the surface area of the optical fiber core wire 5 was in contact with the coating material 3. The comparative example (e) was prepared by adding a support wire to an optical fiber cable 30 having an intervening 9 as shown in FIG. At this time, the optical fiber cable 30 uses eight optical fiber cores 5 with an aromatic polyamide fiber (manufactured by Toray Industries, Inc .: Kevlar) as an intervening 9 so as to enclose the optical fiber core wire 5 and an extruder nipple. The coating material 3 was formed by extrusion coating. The covering material 3, the strength member 4 and the support wire were the same as those in the above example. In the comparative example (e), since the surface of the optical fiber core wire 5 is encased in the interposition 9, 0% of the surface area of the optical fiber core wire 5 is in contact with the coating material 3.

  The following tests were conducted using the optical fiber cables according to the above-described examples and comparative examples. The obtained results are shown in Table 1. In addition, the structure of each Example and the comparative example was shown with the figure number in the table | surface.

(1) Vibration test As shown in FIG. 8, the optical fiber cables 1, 11, 30 according to the respective examples and comparative examples were cut to a length of about 10 m, and the center portions of the cut optical fiber cables 1, 11, 30 were cut. 1 m was set on the vibration testing machine 101. The portions of the optical fiber cables 1, 11, and 30 that are not set on the vibration tester 101 were fixed at the fixing point 102 outside the vibration tester as a loop 103 (2 turns) having a diameter of about 300 mm. The optical fiber core wires 5 at both ends of the optical fiber cables 1, 11, 30 are not fixed and are in a free state. The vibration test conditions were vibration amplitude ± 5 mm, vibration frequency 10 Hz, vibration frequency 1,000,000 times, and transmission loss at a wavelength of 1.55 μm before and after the test was measured. As evaluation criteria, a case where the increase in transmission loss was less than 0.1 dB was marked as ◯, and a case where the increase in transmission loss was 0.1 dB or more was marked as x. As a result, Examples (A) to (F) and Comparative Examples (C) and (D) were evaluated as ◯, and Comparative Examples (A), (B), and (E) were evaluated as x. That is, in an optical fiber cable in which 30% to 70% of the surface area of the optical fiber core is in contact with the coating material, even if vibration is applied, the optical fiber core does not move in the optical fiber cable, and transmission loss is reduced. It turns out that it is hard to increase.

(2) Protrusion test After a 30 m long optical fiber cable was bundled with a diameter of about 2 m and left in an atmosphere at 23 ° C. for 4 hours, the coating material 20 mm on both ends of the optical fiber cable was peeled off and marked on the optical fiber core. Was attached. Then, after being left in an atmosphere of −30 ° C. for 4 hours, the amount of movement of the marked optical fiber was measured with a caliper. Further, after leaving in a 70 ° C. atmosphere for 4 hours, the amount of movement of the marked optical fiber was measured with a caliper. As evaluation criteria, the case where the amount of movement of the optical fiber core wire is less than ± 3.0 mm is indicated by ◯, and the case where the amount of movement of the optical fiber core wire is ± 3.0 mm or more is indicated by ×. As a result, from Examples (A) to (E), Comparative Examples (I) to (D) were evaluated as o, and Comparative Example (E) was evaluated as x. That is, it can be seen that in an optical fiber cable in which 30% to 70% of the surface area of the optical fiber core is in contact with the coating material, the movement of the optical fiber core is small even with expansion and contraction due to temperature changes. Therefore, the optical fiber cable according to the present invention can maintain stable characteristics against temperature changes in the laying environment.

(3) Pull-out test of the optical fiber core The optical fiber cable is cut to a length of about 100 mm, and the coating material, the tensile strength member, and the support wire before and after the optical fiber cable are removed, leaving the coating material at the central portion of the optical fiber cable. Thus, a sample for pulling test between the coating material and the optical fiber core wire was obtained. Here, in any of the examples and comparative examples, the diameter of the aggregate of the central tension member and the optical fiber core or the aggregate of the optical fiber core and the interposition does not exceed 0.97 mm. From the coating material in which the optical fiber core wire is left at a length of 10 mm at a drawing speed of 50 mm / min with a Tensilon type tensile tester through a die having a hole of 1.2 mm from one end of the optical fiber core wire from which the coating material has been removed. the force required to pull out was measured. As evaluation criteria, the maximum value of the force required for extraction was 30N or more, and the force required for extraction was less than 30N was evaluated as x. As a result, Examples (A) to (F) and Comparative Examples (C) and (D) were evaluated as ◯, and Comparative Examples (A), (B), and (E) were evaluated as x. That is, in an optical fiber cable in which 30% to 70% of the surface area of the optical fiber core wire is in contact with the coating material, the optical fiber core wire is difficult to move with respect to the external force received by the optical fiber cable, and is stable after installation. Maintained characteristics.

(4) Optical fiber cable take-out test The optical fiber cable is cut to a length of about 5 m, and the center of the cut optical fiber cable is covered with the optical fiber cable along the notch added to the coating material surface with respect to the longitudinal direction. The material was torn by a length of 200 mm, and an optical fiber core wire extraction work test was carried out with bare hands without using a tool. As an evaluation standard, the case where the optical fiber core wire could be easily taken out was rated as ◯, and the case where it was difficult to take out the optical fiber core wire was rated as x. As a result, Examples (A) to (F) and Comparative Examples (A), (B), and (E) were evaluated as ◯, and Comparative Examples (C) and (D) were evaluated as ×. That is, it can be seen that in the optical fiber cable in which 30% to 70% of the surface area of the optical fiber core wire is in contact with the coating material, the optical fiber core wire can be easily taken out without using a tool.

  As described above, in all the tests, those evaluated as ○ are optical fiber cables in which 30% to 70% of the surface area of the optical fiber core wire is in contact with the coating material, and the optical fiber cable is suitable. I understand.

As an embodiment of the present invention, as shown in FIG. 9, various cross-sectional shapes of the optical cable main body 7 can be applied, such as the elliptical shape of FIG. 12 (a), the gourd shape of FIG. 12 (b), and FIG. The optical fiber core wire 5 and the central tension member 4 'of c) arranged eccentrically can be applied.

In any of the embodiments, the presence / absence of a support line, the presence / absence of a tensile body, and the presence / absence of a notch can be appropriately selected, and may include other components.

The figure which shows the cross section of the conventional drop optical fiber cable. The figure which shows the cross section of the conventional indoor optical fiber cable. The figure which shows the cross section of the optical fiber cable using the conventional tape core wire. The figure which shows the cross section of the optical fiber cable using the conventional intervention. The figure which shows the cross section of an example of the optical fiber cable which concerns on this invention. The figure which shows the cross section of an example of the optical fiber cable which concerns on this invention. The enlarged view which shows the cross section of the optical fiber core wire vicinity of the optical fiber cable which concerns on this invention. The figure which shows the outline | summary of a vibration test. The figure which shows the cross section of an example of the optical fiber cable which concerns on this invention.

Explanation of symbols

11 drop optical fiber cable
1, 20, 30 Optical fiber cable
3 Coating material
4 Strength body
4 'center tension member
5 Optical fiber core wire
5 'optical fiber ribbon
6 Support lines
7 Optical fiber cable body
8 notches
9 Intervention
10 spaces
101 Vibration testing machine
102 fixed points
103

Claims (1)

A drop optical fiber in which a plurality of optical fiber cores are arranged adjacent to the outer periphery of the center tension member so as to surround the entire outer periphery of the center tension member, and the outer periphery of the plurality of optical fiber cores is covered with a coating material In the cable, the covering material is made of at least one of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene, and the optical fiber core wire is against the external force that the drop optical fiber cable receives. 30% to 70% of the surface area of the optical fiber core in order to maintain the stable characteristics after installation, and to easily take out the optical fiber core without using a tool. Is in contact with the covering material ,
The drop optical fiber cable, wherein the covering material is extruded and a space is formed on a side of the optical fiber core wire that contacts the central tension member .

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