JP5520680B2 - Fiber optic cable - Google Patents

Description

  The present invention relates to an optical fiber cable.

  2. Description of the Related Art Conventionally, various optical fiber cables in which a sheath is formed by collectively covering an optical fiber core wire, a pair of tension members, and a support wire at predetermined positions while being sheathed are manufactured and used. In such an optical fiber cable, a V-shaped notch is provided in the sheath so as to easily tear the sheath and take out the optical fiber core wire.

  When these optical fiber cables are installed over the air, characteristic deterioration of unknown cause may occur over time. In recent years, it has become clear that this cause is due to the spawning behavior of cicada, especially the komazemi, on the optical fiber cable that occurs in summer. Specifically, the cause is that an optical fiber cable laying in an imaginary mist is mistaken for a trunk or branch of a tree, and a spawning tube is inserted into the sheath to lay eggs inside. In particular, since the notch portion has a short distance from the sheath surface to the optical fiber core wire, when the laying tube is inserted into the notch portion, the optical fiber may be damaged by the laying tube.

  For this reason, it has been proposed to fill the notch with a peelable protective material (see, for example, Patent Document 1). Alternatively, it has been proposed to form a notch having a narrower width than the semi-vibrating tube in an optical fiber cable (see, for example, Patent Document 2).

JP 2002-90596 A JP 2006-330606 A

  However, even when a notch having a narrower width than that of a semi-vibrated oviduct is provided, the oviduct may be inserted along the notch. On the other hand, when no groove or notch is provided, it is difficult to tear the sheath. In addition, when the protective material is buried in the sheath, the sheath cannot be torn without a special tool.

  The subject of this invention is providing the optical fiber cable which can take out an optical fiber core wire easily, preventing the damage of the optical fiber core wire by a semi-laying oviduct.

In order to solve the above problems, the present invention provides an optical fiber cable in which an optical fiber core is covered with a resin sheath, and the sheath is broken along the optical fiber core more than the sheath. A breakable material made of a resin material having low strength is embedded, and the sheath has a notch formed along the optical fiber core, and the breakable material is disposed between the notch and the optical fiber core. It is characterized by being.

Preferably, the breaking material has a triangular cross section .
Preferably, one surface of the breakable material is exposed on the surface of the sheath, and the color of the exposed surface of the breakable material is a color different from that of the sheath.
Preferably, the width of the fracture material is 0.05 mm to 0.30 mm.
Preferably, the distance from the breaking material to the optical fiber core wire is 0.2 mm to 0.7 mm.

  ADVANTAGE OF THE INVENTION According to this invention, the optical fiber cable which can take out an optical fiber core wire easily can be provided, preventing the damage of the optical fiber core wire by a semi-annual oviduct.

It is sectional drawing perpendicular | vertical to the length direction of the optical fiber cable 1 which concerns on embodiment of this invention. It is sectional drawing which shows schematic structure of the extrusion machine 20 used for extrusion molding of the optical fiber cable 1. FIG. It is the front view which looked at the nipple 21 of the extrusion molding machine 20 from the exit side. It is the front view which looked at the extrusion die 22 of the extrusion molding machine 20 from the exit side. It is sectional drawing perpendicular | vertical to the length direction which shows the optical fiber cable 1 of another form. It is sectional drawing perpendicular | vertical to the length direction which shows the optical fiber cable 1 of another form. It is sectional drawing perpendicular | vertical to the length direction which shows the optical fiber cable 1 of another form. It is sectional drawing perpendicular | vertical to the length direction which shows the optical fiber cable 1 of another form. It is sectional drawing perpendicular | vertical to the length direction which shows the optical fiber cable 1 of another form. It is a figure which shows the state which hold | gripped the edge part of the tension member 12 and the divided | segmented sheath 15 with the chuck | zipper 30 of a tensile testing machine. It is explanatory drawing of an abrasion resistance test.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a cross-sectional view perpendicular to the length direction of an optical fiber cable 1 according to an embodiment of the present invention. As shown in FIG. 1, the optical fiber cable 1 includes an optical fiber core wire 11, two tension members 12, a support wire 14, a sheath 15 that collectively covers these members, and a breakable material embedded in the sheath 15. 16. The portion covering the optical fiber core wire 11 and the tension member 12 (main body portion 2) is formed to have the same shape as the indoor cable, and between the portion covering the support wire 14 (support wire portion 3). A constricted connection 4 is formed. The optical fiber core wire 11, the tension member 12, and the support wire 14 have the same length direction (the direction perpendicular to the paper surface of FIG. 1).
The support wire 14 supports the entire weight of the optical fiber cable 1, and for example, a galvanized steel wire or the like can be used.

  The main body 2 has a substantially rectangular shape with a square cross section, and an optical fiber core wire 11 is disposed at the center. In addition, tension members 12 are respectively arranged on both sides of the main body 2 in the longitudinal direction with respect to the optical fiber core wire 11.

The tension member 12 bears tension acting on the main body 2. For the tension member 12, for example, a steel wire, fiber reinforced plastic (FRP), or the like can be used.
The sheath 15 covers the optical fiber core wire 11, the tension member 12, and the support wire 14. For example, a thermoplastic resin such as non-halogen flame-retardant polyolefin can be used.

The polymer material forming the sheath 15 preferably has a breaking strength of 12 MPa or more. By setting the breaking strength to 12 MPa or more, problems such as damage to the sheath when the optical fiber cable is laid are less likely to occur. On the other hand, in order to facilitate tearing of the sheath 15, the breaking strength is preferably 25 MPa or less.
The breaking strength of the sheath 15 can be appropriately adjusted depending on the type of thermoplastic resin, the temperature of the thermoplastic resin during extrusion molding, and the extrusion pressure.
When a thermoplastic resin is used as the polymer material, the breaking strength can be adjusted, for example, by changing the blending ratio of polypropylene blended with the base polyethylene and the addition amount of magnesium hydroxide added as a flame retardant. .

  The breaking material 16 is embedded from the portion closest to the optical fiber core wire 11 on the surface of the sheath 15 toward the optical fiber core wire 11. A stress acting on the sheath 15 is concentrated on the breaking material 16.

  The rupture material 16 is formed by forming a low-strength rupture resin material having a lower strength than the sheath 15 into a tape shape. The width w (tape thickness) of the breaking material 16 is preferably 0.05 to 0.30 mm. This is because extrusion molding is difficult when it is smaller than 0.05 mm. On the other hand, if the diameter is larger than 0.30 mm, it becomes larger than the diameter of the bear's egg-laying tube, so that the probability that the fiber-optic core wire is damaged by inserting the bear's egg-laying tube into the breaking material 16 increases.

  The breaking material 16 preferably has a breaking strength of 2.3 MPa to 10.2 MPa. This is because extrusion molding is difficult when the breaking strength is less than 2.3 MPa. On the other hand, if it is higher than 10.2 MPa, the stress that tears the sheath 15 does not concentrate on the fracture material 16, and tearing becomes difficult.

  Examples of such a low-strength fracture resin material used for the fracture material 16 include EEA resin (Ethylene-Ethylacrylate Copolymer), EVA resin (Ethylene-Vinyl Acetate; ethylene-vinyl acetate copolymer resin), thermoplastic elastomer, polyurethane, Silicon, low density polyethylene, linear low density polyethylene, medium density polyolefin, and the like can be used.

  Since the fracture material 16 has a moderately weak strength as compared with the sheath 15, the fracture surface propagates along the fracture material 16 when the sheath 15 is torn.

  The thickness d of the sheath 15 from the breaking material 16 to the optical fiber core wire 11 is preferably 0.7 mm or less so that the sheath 15 can be easily torn. On the other hand, d is preferably 0.2 mm or more so that the optical fiber core wire 11 is not exposed even when mechanical deterioration is applied in an impact test or the like.

  Moreover, it is preferable that at least one surface of the breaking material 16 is exposed from the sheath 15 so that the portion of the breaking material 16 can be easily identified when cutting with a nipper or the like. The portion of the breaking material 16 exposed from the sheath 15 is preferably a color different from that of the sheath 15.

  Next, the extruder 20 used for manufacturing the optical fiber cable 1 will be described. FIG. 2 is a cross-sectional view illustrating a schematic configuration of an extruder 20 used for extrusion of the optical fiber cable 1. The extrusion molding machine 20 includes a nipple 21 and an extrusion die 22.

  FIG. 3 is a front view of the nipple 21 of the extrusion molding machine 20 as viewed from the outlet side. As shown in FIG. 3, the nipple 21 is inserted with an insertion hole 23 a through which the optical fiber core wire 11 is inserted, an insertion hole 23 b through which the tension member 12 is inserted, an insertion hole 23 c through which the support wire 14 is inserted, and the breaking member 16. An insertion hole 23d is provided.

  FIG. 4 is a front view of the extrusion die 22 of the extrusion molding machine 20 as viewed from the outlet side. As shown in FIG. 4, the extrusion die 22 is provided with an extrusion port 24 through which a thermoplastic resin 25 serving as a sheath 15 is extruded together with the optical fiber core wire 11, the tension member 12, the support wire 14, and the breaking material 16. .

  Next, a method for manufacturing the optical fiber cable 1 will be described. First, in a state where the optical fiber core wire 11, the tension member 12, the support wire 14, and the breaking material 16 are inserted through the insertion holes 23 a, 23 b, 23 c, 23 d of the nipple 21 and the extrusion port 24 of the extrusion die 22, The resulting molten thermoplastic resin 25 is fed between the nipple 21 and the extrusion die 22. Then, the thermoplastic resin is extruded while the optical fiber core wire 11, the tension member 12, the support wire 14, and the breaking material 16 are fed from the insertion holes 23 a, 23 b, 23 c, and 23 d side of the nipple 21 to the extrusion port 24 side of the extrusion die 22. As a result, the sheath 15 that collectively covers the optical fiber core wire 11, the tension member 12, the support wire 14, and the breaking material 16 is formed.

  Next, a method for exposing the optical fiber core wire 11 from the main body 2 of the optical fiber cable 1 of the present embodiment will be described. First, the nail is cut into the sheath 15 along the breaking material 16 of the cable terminal portion. Next, the sheath 15 is torn right and left from the cut. Then, since the fracture surface propagates along the fracture material 16 and the sheath 15 is torn, the optical fiber core wire 11 can be exposed from the inside.

In addition, as shown in FIG. 5, it is good also considering the cross-sectional shape of the fracture | rupture material 16 as a wedge shape.
Alternatively, as shown in FIG. 6, a notch 18 may be formed in the sheath, and the breaking material 16 may be arranged from the bottom of the notch 18 toward the optical fiber core wire 11. Thus, when the notch 18 is formed, it is easy to specify the place where the breaking material 16 is formed, and the optical fiber core wire can be taken out more easily.

  Alternatively, as shown in FIG. 7, the two breaking members 16 may be shifted from the portion closest to the optical fiber core wire 11 on the surface of the sheath 15 to a position closer to the tension member 12. At this time, the optical fiber core wire 11 is disposed in the middle of the two breaking members 16.

  Or as shown in FIG. 8, it is good also as the optical fiber cable 1 which consists only of the main-body part 2. As shown in FIG. Alternatively, as shown in FIG. 9, an optical fiber cable 1 having a plurality of optical fiber core wires 11 may be used.

  In the above embodiment, one surface of the breaking material 16 embedded in the sheath 15 is exposed. However, the entire breaking material 16 may be embedded in the sheath 15 and not exposed.

  Hereinafter, the present invention will be described in more detail with reference to examples.

  The optical fiber cable 1 similar to FIG. 1 was manufactured by changing the breaking strength and the width W of the breaking material 16. Using these, the tearing force necessary to tear the main body 2, the take-out property of the optical fiber core wire 11, the manufacturability, and the damage probability of the optical fiber core wire 11 were evaluated.

An optical fiber core wire 11 having a diameter of 0.25 mm was used. For the tension member 12, an aramid fiber reinforced plastic (AFRP) having a diameter of 0.5 mm was used. Moreover, the long side dimension of the main-body part 2 was 3.1 mm, and the short side dimension was 2.0 mm.
A galvanized steel wire having a diameter of 1.2 mm was used for the support wire 14. The outer diameter of the support wire portion 3 was 2.0 mm.
The feeding speed of the optical fiber core wire 11, the tension member 12, the support wire 14, and the breaking material 16 was 80 m / min.

  Flame retardant polyolefin was used as the thermoplastic resin forming the sheath 15. The temperature of the thermoplastic resin was 219 ° C., and the extrusion pressure was 26.4 to 26.5 MPa. The breaking strength of the sheath 15 was 12 MPa, and the durometer hardness D was 50. The breaking strength was measured by a method according to JIS K7113, and the durometer hardness D was measured by a method according to JIS K7215.

  As the breaking material 16, a tape made of EEA resin was used. The depth D (different from the lowercase letter d) of the fractured material 16 was adjusted to 0.18 mm (corresponding to d = 0.695 mm≈0.7 mm). The breaking strength (MPa) and the width W (mm) of the breaking material 16 are as shown in Table 1. The breaking strength was measured by a method according to JIS K7113.

[Cable tearing force]
At the end of the optical fiber cable 1, the breaking material 16 and the sheath 15 are cut with a nipper, and are manually broken along the breaking material 16 by about 30 mm. Next, as shown in FIG. 10, the ends of the bisected sheath 15 are gripped by chucks 30 and 30 of a tensile tester, and the chucks 30 and 30 are moved away at 500 mm / min. The maximum value of tearing force when tearing 150 mm was measured.

[Optical fiber take-out property]
When the maximum value of the tearing force of the optical fiber cable is less than 5N, ◎ (very easy), when it is 5N or more and less than 13N, ○ (easy), when it is 13N or more and less than 20N, △ (heavy), stress is concentrated well When it was 20N or more, it was set as x (difficult).
〔Manufacturability〕
The case where it was possible to produce without problems was marked with ◯, and the case where it broke during production was marked with x.

[Optical fiber damage probability]
Two optical fiber cables 1 cut to 13 cm length were made into one set, and a total of 20 sets of 40 were prepared. In one experiment, one set of two optical fiber cables was left in a container having a width of 200 mm, a depth of 200 mm, and a height of 300 mm together with a kuma-zemi and taken out after 24 hours. The damage probability of the optical fiber core 11 (= the number of damage of the optical fiber core 11 ÷ the number of spawning wounds left on the optical fiber cable) was examined.
The results are shown in Table 1.

[Evaluation of breaking strength]
When the breaking strength of the breaking material 16 is 10.2 MPa or less (Production Examples 1 to 7, 11, and 12), the stress that tears the main body 2 is concentrated on the breaking material 16, so that the main body 2 can be easily torn. Line 11 can be removed. On the other hand, when the breaking strength of the breaking material 16 is 12.6 MPa or more (Production Examples 8 to 10), the breaking strength of the breaking material 16 is larger than the breaking strength of the sheath 15, and the stress that tears the main body 2 is increased. It does not concentrate on the breaking material 16. For this reason, the cable tearing force exceeds 20 N, it is difficult to tear by hand, and it is difficult to take out the optical fiber core wire 11.
Further, when the breaking strength of the fractured material 16 was 1.5 MPa (Production Example 1), the fractured material 16 broke during the extrusion production, and could not be stably produced.

[Evaluation of width]
When the width of the breakable material 16 was 0.30 mm or less, which is narrower than the thickness of the laying tube of Coomasemi (Production Examples 3 to 10), the optical fiber core wire 11 was not damaged by Coomasemi. On the other hand, when the width of the breakable material 16 was 0.31 mm or more (Production Examples 1, 2, 11, and 12), the optical fiber core wire 11 was damaged.
Moreover, when the width | variety of the fracture | rupture material 16 was 0.04 or less (manufacture example 8, 10), the fracture | rupture material 16 fractured | ruptured in the middle of extrusion manufacture, and could not be manufactured stably.

An optical fiber cable 1 having the same structure as that of Example 1 was manufactured except that the thickness d of the sheath 15 from the breaking material 16 to the optical fiber core wire 11 was changed. Note that a flame-retardant polyolefin was used as the thermoplastic resin forming the sheath 15. The temperature of the thermoplastic resin was 229 ° C., and the extrusion pressure was 27.5 to 27.7 MPa. The breaking strength of the sheath 15 was 25 MPa, and the durometer hardness D was 59.
Using these, the tearing force necessary for tearing the main body 2, the take-out property of the optical fiber core wire 11 and the manufacturability were evaluated.
As the breaking material 16, a tape made of EEA resin was used. The width W of the fracture material 16 was 0.18 mm, and the fracture strength was 10.2 MPa. Table 2 shows the distance d (mm) from the broken material 16 to the optical fiber core wire 11.
The results are shown in Table 2.

  When the thickness d of the sheath 15 from the breaking material 16 to the optical fiber core wire 11 is 0.7 mm or less (Production Examples 14 to 18), the tearability of the main body 2 is facilitated. On the other hand, when d is set to 0.15 (Production Example 18), there is a high possibility that the breakable material 16 and the optical fiber core wire 11 will be in contact with each other before being damaged, and the productivity will deteriorate.

The optical fiber cable 1 having the same structure as that of Example 1 was manufactured by changing the breaking strength of the sheath 15. Using these, the tearing force necessary for tearing the main body 2, the take-out property of the optical fiber core wire 11, and the damage degree of the sheath 15 were evaluated.
Note that a flame-retardant polyolefin was used as the thermoplastic resin forming the sheath 15. The breaking strength and durometer hardness D of the sheath 15 were adjusted by the temperature of the thermoplastic resin and the extrusion pressure.
As the breaking material 16, a tape made of EEA resin was used. The width W of the fracture material 16 was 0.18 mm, and the fracture strength was 10.2 MPa (similar to Example 2). The depth D of the fracture material 16 was 0.18 mm (similar to Example 1).

[Sheath abrasion resistance test]
A wear resistance test in accordance with JIS C3005 was performed. As shown in FIG. 11, a load 41 of 1 kg was attached to one end of the main body 2, and a predetermined distance (> 30 cm) from the end was fixed by a fixing member 42. A rotating shaft of a grinder 43 made of silicon carbide having a particle size of 36 and a main material was disposed at a position 30 cm below the fixed position. With the main body 2 in contact with the surface of the grinder 43, the grinder 43 was rotated 2000 times at a speed of 60 times / minute. The case where the optical fiber core wire 11 was disconnected after 2,000 rotations was rated as x, and the case where there was no disconnection was rated as ◯.
The results are shown in Table 3.

[Sheath wear resistance]
When the breaking strength of the sheath 15 was less than 12 MPa, the optical fiber core wire 11 was broken in the sheath abrasion resistance test (Production Example 19). On the other hand, when the breaking strength was 12 MPa or more, the optical fiber core wire 11 was not broken in the sheath abrasion resistance test (Production Examples 20 to 22).

[Ease of tearing]
When the breaking strength of the sheath 15 is 25 MPa or less, since the tearing force is less than 20 N, tearing is easy (Production Examples 19 to 21). On the other hand, when the breaking strength of the sheath 15 is greater than 25 MPa, the tearing force is 20 N or more, and tearing is difficult.

DESCRIPTION OF SYMBOLS 1 Optical fiber cable 2 Main-body part 3 Support line part 4 Connection part 11 Optical fiber core wire 12 Tension member 14 Support line 15 Sheath 16 Breaking material 18 Notch 30 Chuck

Claims (5)

An optical fiber cable formed by coating an optical fiber core with a resin sheath,
A breaking material made of a resin material having a breaking strength smaller than that of the sheath is embedded in the sheath along the optical fiber core wire,
A notch is formed in the sheath along the optical fiber core wire,
The optical fiber cable, wherein the breaking material is disposed between the notch and the optical fiber core wire.   The optical fiber cable according to claim 1, wherein the breaking material has a triangular cross section. 3. The optical fiber cable according to claim 1, wherein one surface of the breakable material is exposed on a surface of the sheath, and a color of the exposed surface of the breakable material is different from that of the sheath. The optical fiber cable according to any one of claims 1 to 3 , wherein a width of the breaking material is 0.05 mm to 0.30 mm. The distance from the said fracture | rupture material to an optical fiber core wire is 0.2 mm-0.7 mm, The optical fiber cable as described in any one of Claims 1-4 characterized by the above-mentioned.

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