JPH09243886A - Nonmetallic optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a nonmetallic optical cable having excellent tensile strength and flexibility and good temp. characteristics by arranging an aramid fiber around an optical fiber core wire, forming a sheath around the aramid fiber and inserting a high-tensile body comprising an inorg. fiber reinforced plastic into the sheath. SOLUTION: An aramid fiber 3 is arranged around an optical fiber core wire 2, an inorg. fiber reinforced plastic (FRO) formed into a rod is used as a high-tensile body 5. An FRP prepared by solidifying a reinforcing material comprising an inorg. fiber such as a glass fiber together with a plastic material such as heat-resistant unsatd. polyester resin is preferably used. The first high- tensile body 5, the optical fiber core wire 2 and the second high-tensile body 5 are successively arranged at a same interval on one plane. A sheath 4 is used to integrate the first and second high-tensile bodies 5 and the optical fiber core wire 2 surrounded with the aramid fiber 3 into one body and the sheath is formed around these elements by batch extrusion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-metallic optical fiber cable, and more particularly to a small-fiber non-metallic optical fiber cable suitable for indoor wiring.

[0002]

2. Description of the Related Art A non-metallic optical fiber cable with a small number of fibers is preferably used when an optical fiber is led into a building or the like for wiring. Such a non-metallic optical fiber cable for indoor wiring is required to have a tensile strength so that the optical fiber does not break against a tensile load, and to have flexibility in terms of ease of wiring. It FIG. 2 is a sectional view showing an example of a conventional non-metallic optical fiber cable for indoor wiring. A non-metallic optical fiber cable (hereinafter referred to as a non-metallic optical cable) of this example has an aramid fiber 13 arranged around an optical fiber core wire 12 formed by forming a coating layer on the circumference of an optical fiber element wire 11. A sheath 14 made of vinyl chloride (PVC) or polyethylene (PE) is provided on the circumference. Since the non-metallic optical cable of this example uses the aramid fiber 13 as a strength member, it has excellent tensile strength and flexibility.

However, due to the difference in temperature characteristic between the sheath 14 and the optical fiber, there is a problem in the temperature characteristic of the non-metallic optical cable, especially at low temperature. That is, since the sheath 14 has a higher shrinkage rate at low temperature than the optical fiber, a compressive force may be applied to the optical fiber as the sheath 14 shrinks at low temperature, resulting in distortion.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a non-metallic optical cable having excellent tensile strength and flexibility and good temperature characteristics.

[0005]

In order to solve the above problems, the invention according to claim 1 is such that aramid fibers are arranged around an optical fiber core wire and a sheath is provided on the circumference of the aramid fibers. A non-metallic optical fiber cable characterized in that a tensile strength member made of an inorganic fiber reinforced plastic is inserted into the sheath. Claim 2
The described invention is a first invention comprising an inorganic fiber reinforced plastic.
The tensile strength member, the optical fiber core wire around which the aramid fiber is arranged, and the second tensile strength member made of the inorganic fiber reinforced plastic are sequentially arranged on the same plane, and are extruded and integrally covered to form a sheath. And a weakening groove is provided between the first tensile strength member and the second tensile strength member.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
FIG. 1 is a sectional view showing an embodiment of the non-metallic optical cable of the present invention. In the figure, reference numeral 1 is an optical fiber strand, 2
Is an optical fiber core wire, 3 is an aramid fiber, 4 is a sheath, 5
Indicates a strength member, and 6 indicates a weakening groove. The optical fiber core wire 2 is formed by coating the circumference of the optical fiber wire 1 with nylon resin, ultraviolet curable resin, or the like, and may have any structure. In this embodiment, the single-core optical fiber core wire 2 is used, but it is also possible to use a small number of optical fiber core wires formed by integrating about two optical fiber element wires with a coating layer.

An aramid fiber 3 is arranged around the optical fiber core wire 2. As the aramid fiber 3, for example, poly-p-phenylene terephthalamide fiber (Kevlar: trademark) is preferably used. The aramid fiber 3 is used by being vertically attached to the optical fiber core wire 2 in a state of a long fiber that is not cut midway. The aramid fiber 3 bears most of the tensile strength of the non-metallic optical cable, and if the amount used is too small, the required tensile strength cannot be obtained. Further, if the amount of the aramid fiber 3 used is too large, the nonmetallic optical cable itself becomes thick and the flexibility becomes poor. In this embodiment, the amount of aramid fiber 3 used is preferably set to about 8000 to 9000 denier.

The tensile strength member 5 mainly suppresses the contraction of the non-metallic optical cable against the contraction of the sheath 4 at a low temperature, and the inorganic fiber reinforced plastic (inorganic fiber reinforced plastic having a small expansion coefficient and excellent strength ( FRP: fiber reinfo
rced plastics) are used in the form of rods. As the FRP, for example, a reinforcing material made of inorganic fiber such as glass fiber and solidified with plastic such as heat-resistant unsaturated polyester resin is preferably used. If the strength member 5 is too thick, the flexibility of the non-metallic optical cable is impaired, and if it is too thin, the sheath 4 cannot be sufficiently shrunk. Therefore, the thickness of the strength member 5 is appropriately changed depending on the allowable bending diameter, but in this embodiment, the FRP rod 5 having a diameter of about 0.4 to 0.5 mm is used. One or more tensile strength members 5 can be arranged in an arbitrary number. However, if the number of the tensile strength members 5 is too large, the flexibility of the non-metallic optical cable is deteriorated, and the optical fiber core wire 2 can be easily exposed. It also becomes worse.

In this embodiment, two strength members 5 (a first strength member and a second strength member) are used, and the first strength member 5, the optical fiber core wire 2 and the second strength member are used. The body 5 and the body 5 are sequentially arranged on the same plane so as to be arranged at equal intervals. The distance between the first and second strength members 5 and 5 and the optical fiber core wire 2 can be appropriately changed. Here, “arranged on the same plane” means that the respective members are arranged in parallel so that the central axes of the respective members are located on the same plane. The size of the non-metallic optical cable in the direction parallel to the plane where the central axis of each member is located is called the cable width, and the size of the non-metallic optical cable in the direction perpendicular thereto is called the cable thickness.

The sheath 4 integrates the first and second strength members 5, 5 and the optical fiber core wire 2 around which the aramid fiber 3 is arranged, and is formed on the circumference of these by collective extrusion. To be done. The material of the sheath 4 is PVC
(Polyvinyl chloride) and PE (polyethylene) are preferably used. If the thickness of the sheath 4 is too thin, the loss characteristics deteriorate when mechanical stress such as lateral pressure or impact is applied to the non-metallic optical cable. On the other hand, if it is too thick, the non-metallic optical cable becomes thick and the flexibility deteriorates. Therefore, the thickness and cross-sectional shape of the sheath 4 are appropriately set in consideration of these conditions.

In this embodiment, the sheath 4 has a cross-sectional shape formed into a substantially elliptical shape whose major axis direction is the cable width direction, and the sheath 4 near the optical fiber core 2 has a cable thickness direction. The weakening grooves 6 and 6 are formed by making a notch. The position where the weakening grooves 6 and 6 are provided in the sheath 4 can be appropriately changed as long as it is between the first tensile strength member 5 and the second tensile strength member 5, but the closer to the optical fiber core wire 2, the optical fiber core wire. 2 is preferable because it is easy to put out. Although the weakening groove 6 may be provided at one place, it is preferable to provide the weakening groove 6 on both sides of the optical fiber core wire 2 as in this embodiment because the optical fiber core wire 2 can be easily exposed.

In the non-metallic optical cable having such a structure, the aramid fiber 3 is arranged around the optical fiber core wire 2, and the first tensile strength member 5 and the second tensile strength member 5 are arranged in parallel on both sides thereof. In this state, it is obtained by forming the sheath 4 by batch extrusion coating.

The non-metallic optical cable of this embodiment is
Since the aramid fiber 3 is arranged around the optical fiber core wire 2, the required tensile strength can be obtained. Further, a tensile strength member 5 made of FRP is inserted into the sheath 4, which prevents the entire non-metallic optical cable from contracting as the sheath 4 contracts at a low temperature. The characteristics are improved. Further, since most of the tensile strength of the non-metallic optical cable is carried by the aramid fiber, the strength member 5 made of the FRP rod may be a relatively thin one as long as it can withstand the contraction of the sheath 4. Therefore, by disposing the strength member 5, the flexibility of the non-metallic optical cable is not impaired, and good flexibility can be obtained.

Further, in the non-metallic optical cable of the present embodiment, the first tensile strength member 5 and the second tensile strength member 5 are arranged at positions facing each other with the optical fiber core wire 2 interposed therebetween, and Since the weakening grooves 6 and 6 are provided in the sheath 4 between the tensile strength member 5 and the second tensile strength member 5, the first tensile strength member 5 and the second tensile strength member 5 are pulled in the direction away from each other. Thereby, the sheath 4 can be easily torn at the position of the weakening groove 6. Therefore, when the optical fiber core wire 2 is connected, the optical fiber core wire 2 can be easily exposed without damaging the optical fiber core wire 2 or applying a large bending stress to the optical fiber core wire 2. it can.

[0015]

【Example】

(Example 1) The non-metallic optical cable shown in FIG. 1 was manufactured. First, a nylon resin was coated on the circumference of an optical fiber element wire having an outer diameter of 0.25 mm to prepare an optical fiber core wire having an outer diameter of 0.5 mm. On the other hand, two FRP rods having an outer diameter of 0.4 mm and obtained by hardening glass fibers with a heat-resistant unsaturated polyester resin were prepared. Kevlar of 8500 denier was placed around the optical fiber core, and FRP rods were arranged in parallel on both sides of the optical fiber, and batch extrusion coating was performed.
A sheath made of polyvinyl chloride resin was formed on these circumferences. The distance between the center of the optical fiber and the center of the FRP rod was set to 1.7 mm. The cross-sectional shape of the sheath is a substantially elliptical shape having a major axis length of 5.1 mm and a minor axis length of 4.0 mm with the cable width direction as the major axis direction.
A weakening groove having a depth of 0.5 mm in the cable thickness direction was formed in the vicinity of. When the tensile strength of the non-metallic optical cable thus obtained was measured, the elongation strain when it was pulled under a load of 15 kgf was 0.15%.
In addition, the increase in transmission loss when the normal temperature state of 20 ° C. is changed to the low temperature state of −20 ° C. is 0.06 dB / km (measurement wavelength 1.
55 μm). The flexibility of the non-metallic optical cable was good.

Comparative Example 1 A conventional non-metallic optical cable shown in FIG. 2 was manufactured. The same optical fiber core wire as that used in the first embodiment was used. 8 around the optical fiber
With a Kevlar of 500 denier along, a single extrusion coating was performed, and a sheath made of polyvinyl chloride resin was formed on the periphery thereof. The outer diameter of the sheath was 4.2 mmφ. The transmission loss of the obtained non-metallic optical cable was 0.6 dB / km (measurement wavelength 1.55 μm) when the temperature was changed from a room temperature of 20 ° C. to a low temperature of −20 ° C. The flexibility of the non-metallic optical cable was good.

From these results, the non-metallic optical cable obtained in the above-mentioned Example 1 has almost the same flexibility as that of Comparative Example 1, and the FRP in Example 1
About 20% of the total tensile strength is required for the rod (2 rods)
Therefore, it can be seen that, by using the FRP rod, the tensile strength is slightly improved as compared with Comparative Example 1, and the temperature characteristics are improved.

[0018]

As described above, in the non-metallic optical cable according to claim 1 of the present invention, the aramid fiber is arranged around the optical fiber core wire, and the sheath is provided on the circumference of the aramid fiber. In addition, a tensile strength member made of an inorganic fiber reinforced plastic is inserted into the sheath. Therefore, since the aramid fiber is arranged around the optical fiber core, the required tensile strength can be obtained. Further, since the strength member made of FRP using inorganic fiber is inserted into the sheath, this prevents the entire non-metallic optical cable from shrinking as the sheath shrinks at low temperature. Therefore, the temperature characteristics of the non-metallic optical cable can be improved without impairing the flexibility of the non-metallic optical cable.

A non-metallic optical cable according to a second aspect of the present invention comprises a first tensile strength member made of an inorganic fiber reinforced plastic, an optical fiber core wire around which aramid fibers are arranged, and an inorganic fiber reinforced plastic. The second strength member and the second strength member are sequentially arranged on the same plane and are collectively extruded and covered to form a sheath, which is integrated, and a weakening groove is provided between the first strength member and the second strength member. It is what Therefore, since the first tensile strength member and the second tensile strength member are arranged at positions facing each other across the optical fiber core wire, the temperature characteristics are improved without impairing the flexibility of the non-metallic optical cable. be able to. Further, since the weakening groove is provided in the sheath between the first strength member and the second strength member, the sheath can be formed by pulling the first strength member and the second strength member away from each other. It can be easily torn at the position of the weakening groove. Therefore, the optical fiber core wire can be easily exposed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a non-metallic optical fiber cable of the present invention.

FIG. 2 is a cross-sectional view showing an example of a conventional non-metallic optical fiber cable.

[Explanation of symbols]

2 ... Optical fiber core wire, 3 ... Aramid fiber, 4 ... Sheath,
5 ... tensile strength member, 6 ... weakening groove.

Claims (2)

[Claims] 1. An aramid fiber is arranged around an optical fiber core, a sheath is provided on the circumference of the aramid fiber, and a tensile strength member made of an inorganic fiber reinforced plastic is inserted into the sheath. A non-metallic optical fiber cable characterized in that 2. A first member made of an inorganic fiber reinforced plastic.
The tensile strength member, the optical fiber core wire around which the aramid fiber is arranged, and the second tensile strength member made of the inorganic fiber reinforced plastic are sequentially arranged on the same plane, and are extruded and integrally covered to form a sheath. A non-metallic optical fiber cable, wherein a weakening groove is provided between the first strength member and the second strength member.