JP2005189608A - Optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber cable capable of flexibly being bent while satisfactorily maintaining tensile characteristics. <P>SOLUTION: The optical fiber cable 10 comprises a coated optical fiber 11; tension members 12 which are arranged in parallel on both sides of the coated optical fiber 11; and a clad 13 with which the coated optical fiber 11 and the tension members 12 are collectively covered. By using a twisted structure, for instance, a steel twisted wire as the tension members 12, it is made possible to flexibly bend the optical fiber cable while satisfactorily maintaining tensile characteristics. Further, by optimizing a positional relation of the coated optical fiber 11 and a thickness of the clad 13, such an optical fiber cable 10 that the coated optical fiber 11 does not break even upon the kinking of the cable can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber cable.

  When an optical fiber core wire is wired in a house, an indoor optical fiber cable is used (see Patent Document 1). A cross-sectional view of this optical fiber cable is shown in FIG. In FIG. 5, an optical fiber cable 50 collectively covers an optical fiber core wire 51, a tensile body 52 arranged in parallel on both sides of the optical fiber core wire 51, and the optical fiber core wire 51 and the tensile body 52. The outer jacket 53 is provided with a notch portion 54 for facilitating taking out the optical fiber core wire 51. Typical dimensions of these optical fiber cables are about 3.0 to 3.5 mm for the long side and about 1.5 to 2.0 mm for the short side.

  Here, as the optical fiber core wire 51, a single-core optical fiber core wire or a multi-core optical fiber core wire such as an optical fiber tape core wire may be used. As the strength member 52, a single steel wire is used in terms of tensile properties and cost. As the jacket 53, a resin such as polyvinyl chloride or polyethylene is preferably used.

JP 2003-43321 A

By the way, in recent years, construction of an optical subscriber line network is progressing rapidly, and the opportunity to perform optical fiber cable wiring work in a house is increasing. Such wiring work is a small-scale construction, and it is preferable that each user without specialized technology can perform it by himself / herself, and it is desired to provide an optical fiber cable with good workability.
The inventors of the present invention diligently studied to provide an optical fiber cable with good workability, and have come to focus on the ease of bending of the optical fiber cable and the possibility of damage when the optical fiber cable is bent. That is, it has been found that the single steel wire used for the strength member has excellent tensile properties, but has a large repulsive force when bent, and has the following problems when used for an optical fiber cable. For example, when an optical fiber cable is laid in a pipe, depending on the form of the pipe to be laid, the optical fiber cable may stick to the pipe due to repulsion caused by bending and may be damaged. Also, when wiring along the wall surface or when bundled to a small diameter, there is a problem that the bending rigidity of the optical fiber cable is large and workability is impaired.
In addition, when each user without specialized technology performs wiring work, the optical fiber cable is excessively bent and damaged, and it is difficult to determine whether or not the optical fiber cable is damaged. Therefore, it has been recognized that the property of not damaging even if there is some work mistake is a matter that should be realized with particular priority.

  Therefore, an object of the present invention is to provide an optical fiber cable that can be flexibly bent while maintaining sufficient tensile characteristics, and to suppress damage that occurs temporarily during wiring work.

  The invention of claim 1 is an optical fiber cable in which tensile strength members are arranged in parallel on both sides of an optical fiber core wire and are collectively covered, and the tensile strength member has a twisted structure. .

The invention of claim 2 is the invention of claim 1, wherein the repulsive force F (unit: N) when the bending strength of 20 mm is applied to the strength member is
0.117 ≦ F ≦ 0.736
It is characterized by being.

According to a third aspect of the present invention, in the first or second aspect of the invention, the bending radius of the optical fiber constituting the optical fiber core wire is R (unit: mm), and the thickness of the optical fiber cable is A (unit). : Mm), where d (unit: mm) is the deviation between the straight line connecting the centers of the tensile bodies and the fiber center,
0 ≦ R <(A / 2) −d
The relationship is established.

The invention of claim 4 is the invention of claim 3, wherein the thickness A (unit: mm) of the optical fiber cable and the deviation d (unit: mm) are
1 ≦ (A / 2) −d and A ≦ 4
The relationship is established.

  The optical fiber cable of the present invention has a structure in which tensile strength members arranged in parallel on both sides of the optical fiber core have a twisted structure, so that the optical fiber cable can be bent flexibly while maintaining sufficient tensile characteristics. Therefore, it is possible to obtain easier construction and lineability. Furthermore, by optimizing the thickness of the optical fiber cable, it is possible to provide an optical fiber cable with few accidents during wiring work. That is, by using the optical fiber cable of the present invention, easy cable construction is possible, which greatly contributes to the spread of the optical fiber network.

  An embodiment of the present invention will be described.

  FIG. 1 is a cross-sectional view showing an example of an optical fiber cable according to an embodiment of the present invention. In FIG. 1, an optical fiber cable 10 collectively covers an optical fiber core wire 11, a tensile body 12 arranged in parallel on both sides of the optical fiber core wire 11, and the optical fiber core wire 11 and the tensile body 12. The outer cover 13 is provided with a notch 14. These configurations in FIG. 1 are basically the same as those of the conventional optical fiber cable shown in FIG.

  Here, the optical fiber cable shown in FIG. 1 is different from the conventional optical fiber cable shown in FIG. 5 in that the strength member 12 has a twisted structure. A specific example of the strength member 12 is a stranded wire such as a steel stranded wire. Hereinafter, in order to simplify the description, the tensile body 12 in FIG. 1 will be described as a steel stranded wire, and the tensile body 52 in FIG. 5 will be described as a single steel wire, but the actual tensile body 12 may be other than a steel wire, for example, a plurality of FRPs. Those formed by twisting together can also be used.

  In the embodiment of the present invention, since the strength member 12 has a twisted structure, the strain is relieved by the movement of each twisted steel wire, and the strength member 52 of the conventional optical fiber cable 50 is reduced. Thus, the optical fiber cable 10 that can be bent flexibly can be obtained as compared with the case where a single steel wire is used.

  In addition, regarding the tensile characteristics, by making the sum of the cross-sectional areas of the steel wires constituting the strength member 12 to be approximately the same as the cross-sectional area of the single steel wire constituting the strength body 52 in FIG. It is possible to keep.

  About the bending rigidity of the optical fiber cables 10 and 50, the repulsive force at the time of bending the strength members 12 and 52 influences strongly. Therefore, by setting the repulsive force within an appropriate range, it is possible to obtain the optical fiber cable 10 that can be bent flexibly while maintaining the tensile characteristics sufficiently.

  Here, the measurement of the repulsive force at the time of bending a tension body is demonstrated. FIG. 2 is an explanatory diagram showing a measurement system used when measuring a repulsive force when a tensile body according to IEC60794-2-1 E17C is bent. The measuring device is a balance to which a slider having a presser plate is attached, and the slider is adjusted to set the bending diameter of the tensile strength body to 20 mm. At that time, the repulsive force F (unit: : N) is required.

In the present invention, the value of the repulsive force F measured by the measurement system of FIG.
0.117 ≦ F ≦ 0.736
By setting it as the range of this, the optical fiber cable 10 which can be bent flexibly can be obtained, maintaining a tension | pulling characteristic fully.

  The upper limit value of the repulsive force F is determined by evaluating whether or not the outer sheath 13 is damaged when the optical fiber cable 10 is laid on the pipe. The lower limit value of the repulsive force F is determined based on the optical fiber core wire. 11 was set to a value capable of suppressing an increase in loss due to buckling. The buckling of the optical fiber core 11 is considered to be caused by the tensile body 12 buckling due to the temperature contraction of the jacket 13, and this effect also acts on the optical fiber core 11 as a compressive force to buckle.

  By the way, the workability is improved by making the optical fiber cable 10 shown in FIG. 1 flexible. However, when the cable is caught on something unexpectedly, the cable may be bent excessively. It tends to increase from the case of.

  Therefore, by making the thickness of the jacket 13 of the optical fiber cable 10 larger than the fracture bend diameter of the optical fiber core wire 11, a bend radius equal to or larger than the fracture bend of the optical fiber core wire 11 is always secured as the optical fiber cable 10. Therefore, even when the optical fiber cable 10 is bent excessively, the optical fiber core wire 11 is not broken. This state is shown in FIG. FIG. 3 is an explanatory view showing an example of a state in which the optical fiber cable is bent to the maximum, (A) shows a sectional view of the optical fiber cable, and (B) shows a side sectional view.

  By the way, it is ideal that the straight line connecting the centers of the strength members 12 becomes the center of bending of the optical fiber cable 10 and this straight line coincides with the center of the optical fiber core wire 11. However, in the actual optical fiber cable 10, the center of the optical fiber core wire 11 may deviate from the straight line connecting the centers of the tensile strength members 12 due to manufacturing variations. Therefore, it is necessary to consider the amount of this deviation. This state is shown in FIG. 4A and 4B are explanatory views showing a state in which the optical fiber cable is bent to the maximum extent in the direction in which the optical fiber core wire is displaced. FIG. 4A is a cross-sectional view of the optical fiber cable, and FIG. Show.

The condition for the optical fiber core wire 11 not to be broken even when the optical fiber cable 10 is bent to the maximum is that the bending radius of the optical fiber core wire 11 constituting the optical fiber core wire 10 is R (unit: mm), When the thickness of the optical fiber cable 10 is A (unit: mm), and the deviation between the straight line connecting the centers of the strength members 12 and the center of the optical fiber core wire 11 is d (unit: mm),
0 ≦ R <(A / 2) −d
Is to establish the relationship.

  On the other hand, if the wall thickness A of the jacket 13 is too thick, the contraction force of the jacket 13 increases at low temperatures, the optical fiber core wire 11 buckles, and the loss increases. Therefore, the upper limit value of the thickness of the jacket 13 needs to be a value that does not cause a loss fluctuation that causes a problem even at low temperatures in the optical fiber cable 10.

Therefore, between the thickness A (unit: mm) of the jacket 13 of the optical fiber cable 10 and the above-described deviation d (unit: mm),
1 ≦ (A / 2) −d and A ≦ 4
If the above relationship is established, it is possible to obtain the optical fiber cable 10 that does not cause a loss fluctuation that causes a problem even at a low temperature.

  Examples for explaining embodiments of the present invention will be given below.

  Table 1 shows an example of the strength member 12 of the optical fiber cable 10 in FIG. 1 and an example of the strength member 52 of the optical fiber cable 50 in FIG. Table 1 shows the types of strength members, the outer diameter at the time of twisting, the sum of the cross-sectional areas, and the repulsive force. The repulsive force was measured by the measurement system shown in FIG.

  As shown in Table 1, in the comparison between Example 1 and the conventional example, the repulsive force indicating the suppleness is about 1/3 even though the outer diameter is hardly changed, and it is considerably reduced by using a stranded wire. It turns out to be supple. Further, since the cross-sectional area is almost the same as that of the single steel wire, it can be seen that the example of the stranded wire has almost the same level of tensile property.

  Next, in order to determine the upper limit value of the repulsive force F of the strength member 12, the presence or absence of damage to the optical fiber cable was confirmed when a plurality of optical fiber cables having different strength members were laid in the pipe. The results are shown in Table 2. The pipe type was a synthetic resin flexible conduit, the pipe bending diameter was 160 mm, and the number of pipe bending points was 10.

  As shown in Table 2, in order to avoid troubles when wiring into the pipe, in order to exert an effect if the repulsive force F of the tensile body 12 is 0.735 N or less, a twisted wire is used as the tensile body 12. When used, the repulsive force F must be 0.735 N or less.

  Next, in order to determine the lower limit value of the repulsive force F of the tensile body 12, the increase in loss at low temperatures was evaluated using a plurality of optical fiber cables 10 having different tensile bodies. The results are shown in Table 3. The optical fiber core 11 is a 1.3 μm zero-dispersion optical fiber (outer diameter ??? μm), the cable length is 1 km, the temperature is lowered from normal temperature to −30 ° C. until it stabilizes, and the measurement wavelength is The thickness was 1.55 μm.

  As shown in Table 3, it is desirable that the loss increase level at low temperature should not exceed 0.1 (dB / km). From this viewpoint, the repulsive force F needs to be 0.118 N or more.

  Next, when the optical fiber cable 10 is bent to the maximum extent, a value defined by the thickness A of the outer sheath 13 where the optical fiber core wire 11 is not bent and the deviation from the bending center of the optical fiber core wire. evaluated. The results are shown in Table 4. The deviation d between the straight line connecting the centers of the strength members 12 shown in FIG. 4 and the center of the optical fiber core wire 11 was set to 0.2 mm.

  As shown in Table 4, when the value (A / 2) -d defined by the thickness A of the jacket 13 and the deviation d from the bending center of the optical fiber core wire is 1.0 mm or more, the optical fiber Even if the cable was bent as much as possible, no breakage of the core occurred. This shows that the fracture bend radius R of the optical fiber core wire 11 used this time is a constant value of approximately 0.9 mm. If the thickness of the jacket 13 of the optical fiber cable 10 is optimized, the break bend radius is always maintained. It is because it is not bent below. In addition, although the tensile strength body 12 was changed in the range of all the samples shown in Table 1, the same results as in Table 4 were obtained.

  Next, in order to determine the upper limit value of the thickness of the outer jacket 13, the sample was varied in temperature at a low temperature, and the presence or absence of fluctuations in loss was confirmed. The results are shown in Table 5. In addition, a 1.3 μm zero-dispersion optical fiber 1 core (outer diameter ??? μm) is used as the optical fiber core wire 11, and the tensile body 12 of Example 1 in Table 1 (repulsive force F = 0. 422N), the cable length was 500 m, the temperature was lowered from normal temperature to −30 ° C. until stabilization, and the measurement wavelength was 1.55 μm.

  As shown in Table 5, when the value of the thickness A of the jacket 13 is too large, the shrinkage force of the jacket 13 is increased, and 0.1 (which is desirable as a level of increase in loss at low temperatures) dB / km). For this reason, the value of the thickness A of the jacket 12 needs to be 4 mm or less.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the matters described in the claims.

It is sectional drawing which shows an example of the optical fiber cable which concerns on embodiment of this invention. It is explanatory drawing which shows the measuring system used when measuring the repulsive force at the time of bending a tension body. It is explanatory drawing which shows an example of the state which the optical fiber cable kinked, (A) is sectional drawing of an optical fiber cable, (B) shows a sectional side view, respectively. It is explanatory drawing which shows the state which the optical fiber cable kinked in the direction which the optical fiber core wire shifted | deviated, (A) is sectional drawing of an optical fiber cable, (B) shows a sectional side view, respectively. It is sectional drawing which shows an example of the conventional optical fiber cable.

Explanation of symbols

10, 50 Optical fiber cable 11, 51 Optical fiber core wire 12, 52 Tensile body 13, 53 Outer sheath 14, 54 Notch

Claims (4)

  An optical fiber cable in which tensile strength members are arranged in parallel on both sides of an optical fiber core and collectively covered, and the tensile strength member has a twisted structure. The repulsive force F (unit: N) when a bending with a bending diameter of 20 mm is applied to the tensile body,
0.117 ≦ F ≦ 0.736
The optical fiber cable according to claim 1, wherein: The breaking bend radius of the optical fiber constituting the optical fiber core wire is R (unit: mm), the thickness of the optical fiber cable is A (unit: mm), and the straight line connecting the centers of the tensile members and the fiber center When the deviation is d (unit: mm),
0 ≦ R <(A / 2) −d
The optical fiber cable according to claim 1, wherein the relationship is established. Between the thickness A (unit: mm) of the optical fiber cable and the deviation d (unit: mm),
1 ≦ (A / 2) −d and A ≦ 4
The optical fiber cable according to claim 3, wherein the relationship is established.

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