JP4918058B2 - Optical fiber cord - Google Patents

Description

  The present invention relates to an optical fiber cord having bending strength and mechanical strength.

  In future information communication such as NGN, video communication services will be the center, and networks using optical fibers are being built for broadband information communication. Conventionally, optical fibers have been weak against bending, and have the property of easily increasing transmission loss and breaking. However, in optical fiber wiring in the home or building that will increase toward FTTH in the future, maintenance of transmission quality against sudden bends such as wiring freely in a room or along a wall surface, exposed wiring Strict requirements such as ensuring mechanical strength from external pressure at the part are required.

  A general optical fiber core has a structure in which an optical fiber protected by a protective material such as polyamide is surrounded by a tensile body such as Kevlar and further surrounded by a coating. However, with this structure, there is a risk of loss when bending is applied. Therefore, there is an example of an optical fiber cord in which an optical fiber core wire is inserted into a pipe or a corrugated tube for the purpose of suppressing bending. However, there is a problem that the pipe is too difficult to bend. Further, in a normal corrugated tube, when the radius of curvature is reduced, a force that compresses the optical fiber core wire is applied, and a steep bend occurs. In general, the above-described optical fiber core wire is often referred to as an optical fiber cord. However, in order to clarify the difference between the presence or absence of a reinforcing member that suppresses bending, an optical fiber cord is referred to as an optical fiber cord in this specification, and the object to which the reinforcing member that suppresses bending is attached is optical. It will be called a fiber core.

As another method for suppressing the bending of the optical fiber core, there is an example in which a reinforcing member is spirally wound around the optical fiber core. FIG. 1 is a view showing an optical fiber cord in which a reinforcing member is spirally wound around an optical fiber core wire. The optical fiber cord 900 includes an optical fiber core 910 and a reinforcing member 920 spirally wound around the optical fiber core 910. There is also an invention of Patent Document 1.
JP 2000-221371 A

FIG. 2 is a view showing a state of a cross section when the optical fiber cord 900 shown in FIG. 1 is bent with a small radius of curvature. When the reinforcing member is simply spirally wound, a portion 990 where the reinforcing members 920 overlap with each other is generated as the radius of curvature is reduced, and the optical fiber core 910 is damaged or compressed as shown in FIG. There is a risk of doing . If the structure of the reinforcing member shown in FIG. 5 and FIG. 7 of Patent Document 1, it is considered that can be resolved such problems, because the structure is complicated, increases the production cost can not be avoided.
An object of the present invention is to provide an optical fiber cord that is provided with a bending suppressing means that has a low possibility of damaging or compressing an optical fiber core and that is easy to manufacture.

  The optical fiber cord of the present invention includes an optical fiber core, an insulating reinforcing member spirally wound around the optical fiber core so as to have a gap, and a jacket. The jacket has elasticity, covers the reinforcing member and the optical fiber core wire, and enters the gap between the reinforcing members.

  According to the optical fiber cord of the present invention, since the outer jacket having elasticity enters the gap between the reinforcing members, the reinforcing members are difficult to overlap even if the radius of curvature is reduced. Therefore, the optical fiber cord of the present invention can disperse the bending over a wide range (long range), and can prevent the curvature radius from becoming locally small. Moreover, the optical fiber cord of the present invention is easy to manufacture.

  Examples of the present invention will be described below. In addition, the same number is attached | subjected to the same structure part, and duplication description is abbreviate | omitted.

  FIG. 3 shows a structure when the outer cover of the optical fiber cord of the present invention is removed (the outer cover is indicated by a dotted line). FIG. 4 shows the shape of the reinforcing member. 5 is a cross-sectional view when the optical fiber cord 100 is cut along AA in FIG. 3, and FIG. 6 is a cross-sectional view when the optical fiber cord 100 is cut along BB in FIG. The optical fiber cord 100 includes an optical fiber core 110, an insulating reinforcing member 120 spirally wound so as to have a gap in the optical fiber core 110, and a jacket 130. In addition, there is a gap 140 between the reinforcing member 120 and the optical fiber core wire 110.

  The optical fiber core 110 has a structure in which an optical fiber 111 protected by a protective material such as polyamide is further surrounded by a tensile body such as Kevlar and a coating 112. Generally, the diameter of the optical fiber core wire 110 is 1 to 2 mm. The reinforcing member 120 is an insulating material having a width w and a thickness h, and is spirally wound around the optical fiber core wire 110 so as to have a gap d. That is, the spiral pitch p is w + d. The reinforcing member 120 may be made of, for example, a non-metallic material such as polyamide resin, having a width of 2 to 3 mm and a thickness of 0.5 mm. In this case, the pitch may be 3 to 4 mm. The jacket 130 has elasticity, covers the reinforcing member and the optical fiber core wire, and enters the gap between the reinforcing members. A material such as vinyl chloride or polyethylene may be used for the jacket, and flame retardant polyethylene may be used when fire resistance is required. For example, the outer diameter of the outer cover 130 may be 4 mm.

  FIG. 7 is a view showing a state of a BB cross section when the optical fiber cord 100 is bent. In the optical fiber cord 100, since the outer jacket 130 having elasticity is inserted in the gap between the reinforcing members 120, the reinforcing members 120 are difficult to overlap even if the radius of curvature is reduced. Because the reinforcement members are difficult to overlap, when bending exceeding the allowable range is applied, the bending is distributed over a wide range (long range) by bending other parts (the part where bending up to the allowable range is not applied). Can be made. Therefore, it is possible to prevent the curvature radius from being locally reduced.

Further, since the outer cover 130 is compressed on the inner periphery side of the bending, a force for spreading the outer cover 130 is generated. Since the outer cover 130 extends on the outer peripheral side of the bending, a contracting force is generated in the outer cover 130. The bending can be dispersed in a wide range (long range) also by such a force of the jacket 130.
Furthermore, if the reinforcing member 120 and the outer jacket 130 are brought into close contact with each other, the reinforcing member 120 becomes more difficult to overlap, and a force to pull on the outer peripheral side of the bending also occurs. Therefore, it is possible to further prevent the radius of curvature from being locally reduced.

In addition, what is necessary is just to design suitably the width w of the reinforcement member 120, and the pitch p to wind around according to the requirements of the minimum curvature radius. In addition, the thickness h of the reinforcing member 120 and the hardness of the outer jacket 130 may be appropriately designed according to the requirements regarding the force for bending the optical fiber cord 100. In addition, the optical fiber cord of the present invention can be manufactured by controlling the viscosity of the jacket and the pressure applied to the jacket at the time of manufacture, so that it is easy to manufacture.
As described above, the optical fiber cord 100 can protect the optical fiber core wire from external pressure and force to bend. Therefore, even when used for wiring in a house, disconnection due to bending is unlikely to occur.

8 is a cross-sectional view when the optical fiber cord is cut along AA in FIG. 3, and FIG. 9 is a cross-sectional view when the optical fiber cord 200 is cut along BB in FIG. Note that the structure when the jacket of the optical fiber cord is removed is the same as FIG. The optical fiber cord 200 is different from the optical fiber cord 100 in that the jacket 130 ′ is bonded to the optical fiber core wire 110. There is a space 150 between the reinforcing member 120 and the optical fiber core wire 110.
The optical fiber cord 200 has a greater effect of suppressing local bending than the optical fiber cord 100 because the outer sheath 130 ′ is bonded to the optical fiber core wire 110. Other effects are the same as those of the optical fiber cord 100.

10 is a cross-sectional view when the optical fiber cord is cut along AA in FIG. 3, and FIG. 11 is a cross-sectional view when the optical fiber cord 300 is cut along BB in FIG. Note that the structure when the jacket of the optical fiber cord is removed is the same as FIG. The optical fiber cord 300 is different from the optical fiber cord 100 in that the reinforcing member 120 is in close contact with the optical fiber core wire 110 (there is no gap 140). The optical fiber cord 300 having the structure can be manufactured by being wound around the optical fiber core wire 110 while applying a predetermined tension to the reinforcing member 120.
Further, the jacket 130 may be bonded to the optical fiber core wire 110. In the case of the optical fiber cord 300, it is easy to manufacture the outer sheath 130 to be bonded to the optical fiber core wire 110.

  In the optical fiber cord 300, since the reinforcing member 120 is in close contact with the optical fiber core wire 110, the possibility that the reinforcing member 120 overlaps as shown in FIG. 2 is further reduced. Moreover, if the jacket 130 is bonded to the optical fiber core 110, the effect of suppressing local bending becomes greater.

[Experiment]
Next, a comparison experiment result between the optical fiber cord 300 and the optical fiber core wire 110 and a comparison experiment result between the optical fiber cord 300 and the optical drop cable are shown. The optical drop cable is an optical cable for outdoor use mainly used between a utility pole and a house, and its structure is disclosed in Japanese Patent Application Laid-Open No. 10-333000.

  In this experiment, an optical fiber cord 300 in which a reinforcing member 120 having a width w = 2.03 mm and a thickness h = 0.53 mm was spirally wound around the optical fiber core 110 with a pitch p = 2.4 mm was used. In addition, as the optical fiber core, one having a diameter of 1.7 mm was used (in this specification, called an optical fiber core, but generally an optical fiber cord of φ1.7). The jacket 130 and the optical fiber core wire 110 are not bonded. As the optical drop cable, an optical drop cable having a structure as disclosed in FIG. 2 of JP-A-10-333000 was used.

  FIG. 12 is a diagram showing a side pressure test method performed on the optical fiber cord 300 and the optical fiber core wire. A cord to be measured such as the optical fiber cord 300 was sandwiched between flat plates 511 and 512 having a length of 100 mm and pressed with a force F to obtain a force F with an insertion loss of 0.1 dB. As a result, the optical fiber core wire was 2136.53N, while the optical fiber cord 300 was 4188.27N. Therefore, it can be seen that it can withstand about twice the lateral pressure.

  FIG. 13 is a diagram illustrating a bending test method performed on the optical fiber cord 300 and the optical fiber core wire. A cord to be measured such as the optical fiber cord 300 was rotated around the mandrel 521, bent while applying tension with a weight 522, and insertion loss was measured. The mandrel 521 was prepared with a diameter of 30 mm, 18 mm, 10 mm, and 6 mm, and the weight was 500 g. The experimental results are shown in FIG. As can be seen from the experimental results, the insertion loss of the optical fiber cord 300 does not increase even when the mandrel diameter decreases. That is, it can be seen that the optical fiber cord 300 can disperse the bending over a wide range (long range) and can prevent the curvature radius from being locally reduced.

  FIG. 15 is a diagram illustrating a method of an impact test performed on the optical fiber cord 300 and the optical drop cable. A cord to be measured such as the optical fiber cord 300 is fixed on the plate 531, and an impact tool 532 having a radius of 10 mm is placed on the cord. Then, the weight was dropped from a height of 1000 mm onto the impacting tool 532, and the maximum value of insertion loss was measured. The mass of the weight was 0.2 kg, 0.3 kg, 0.4 kg, 0.5 kg, 1.0 kg, and 1.5 kg. The experimental results are shown in FIG. As can be seen from this result, it can be seen that it has characteristics several times better than the optical drop cable that requires impact characteristics. Therefore, the optical fiber cord 300 can be fixed by using a staple or the like with indoor wiring.

  The optical fiber cord of the present invention can suppress an increase in loss even when a force to be bent suddenly is applied even though the SM optical fiber used conventionally is used as described above. . Moreover, it has the mechanical strength with respect to the external pressure requested | required of an exposed wiring part. Therefore, it is an optical fiber cord that can practically realize optical fiber wiring in the home or building that will play a leading role in future FTTH.

The figure which shows the structure of the conventional optical fiber cord. The figure which shows the mode of a cross section when the conventional optical fiber cord is bent with a small curvature radius. The figure which shows a structure when the jacket of the optical fiber cord of this invention is removed. The figure which shows the shape of a reinforcement member. Sectional drawing when the optical fiber cord of Example 1 is cut by AA in FIG. Sectional drawing when the optical fiber cord of Example 1 is cut by BB in FIG. The figure which shows the mode of the BB cross section when the optical fiber cord of this invention is bent. Sectional drawing when the optical fiber cord of Example 2 is cut by AA in FIG. Sectional drawing when the optical fiber cord of Example 2 is cut by BB in FIG. Sectional drawing when the optical fiber cord of Example 3 is cut by AA in FIG. Sectional drawing when the optical fiber cord of Example 3 is cut by BB in FIG. The figure which shows the method of the side pressure test done with respect to the optical fiber cord 300 and the optical fiber core wire. The figure which shows the method of the bending test performed with respect to the optical fiber cord 300 and the optical fiber core wire. The figure which shows the result of the bending test done with respect to the optical fiber cord 300 and the optical fiber core wire. The figure which shows the method of the impact test done with respect to the optical fiber cord 300 and the optical drop cable. The figure which shows the result of the impact test done with respect to the optical fiber cord 300 and the optical drop cable.

Explanation of symbols

100, 200, 300, 900 Optical fiber cord 110, 910 Optical fiber core wire 111 Optical fiber 112 Coating 120, 920 Reinforcement member 130, 130 'Outer jacket 140, 150 Spacing 990 Overlapping part

Claims (3)

An optical fiber core,
An insulating reinforcement member spirally wound around the optical fiber core wire so as to have a gap;
An outer cover that has elasticity, covers the reinforcing member and the optical fiber core, enters the gap between the reinforcing members, and adheres to the optical fiber core;
With
By setting the width w of the reinforcing member to 2 to 3 mm, the pitch p of the spiral to 3 to 4 mm, and the gap to a gap d where p = w + d, the gap of the reinforcing member and the outer jacket can be deformed. An optical fiber cord having a limited radius of curvature. The optical fiber cord according to claim 1,
The outer jacket is in close contact with the reinforcing member. The optical fiber cord according to claim 1 or 2,
The optical fiber cord, wherein the reinforcing member is in close contact with the optical fiber core wire.

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