JP2005049658A - Optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber cable that, while satisfying tensile characteristics, is less prone to cause breaking of a tension member or lowering of the Young's modulus even if the cable is bent with a small diameter. <P>SOLUTION: The optical fiber cable is one in which a coated optical fiber and tension members are integrated, and is characterized in that the cross section of the tension members is flat in a prescribed direction. The optical fiber cable is further characterized in that the cross section of the optical fiber cable body portion is also flat in a prescribed direction, that a coated optical fiber and at least one tension member are contained in the optical fiber cable body portion, and that the tension member is flat in the direction of the longer side of the cross section of the optical fiber cable body portion. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber cable. In particular, the present invention relates to an optical fiber cable having excellent handling properties in a drop optical fiber cable used for taking an optical fiber into a house and an indoor optical fiber cable used in a house or on a premises.

  In recent years, the construction of optical subscriber line networks has been progressing rapidly. Conventionally, a drop optical fiber cable as shown in FIG. 1 is used as a pull-in optical fiber cable for pulling from a trunk optical fiber cable into a home such as each home. In addition, indoor optical fiber cables as shown in FIG. 2 are used in the homes and 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. These optical fiber cables are an optical fiber cable body in which the optical fiber core wire 5 and two strength members are arranged in a straight line and covered with a flat covering material 3 so that the arrangement direction is the long side direction and the cross section is flat. Part 7 is formed. The support wire 6 is for holding the optical fiber cable body 7 and is connected to the optical fiber cable 7 by the covering material 3. In general, these optical fiber cables are formed with notches 8 and cuts along the longitudinal direction, so that the optical fiber cables can be easily removed from the notches 8 by human hands without using a special tool when laying. The optical fiber core wire 5 inside the optical fiber cable body 7 can be easily taken out. 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.

  Since these optical fiber cables are directly drawn into the house from the outside, if a metal member is used in the fiber optic cable when a lightning strike occurs, surge currents from the lightning may be transmitted to the house and damage optical equipment. is there. Therefore, a structure using a non-conductive member has been adopted for the optical fiber cable main body portion 7 drawn into the house. In particular, the tension member 4 is mounted so that the tension is not transmitted to the optical fiber core wire 5 when the optical fiber cable is pulled or stretched due to a temperature change or the like. It is increasingly composed of sex substances. A reinforced plastic containing glass fibers (generally referred to as glass FRP) is often used as a non-conductive strength member. Since this glass FRP contains glass fibers, the Young's modulus is relatively large and has an excellent tensile strength function. Further, as a tensile strength other than glass FRP, a plastic having a relatively large Young's modulus such as PET (polyethylene terephthalate) is used.

JP 2003-090943 A Japanese Patent Laid-Open No. 2003-140011

  However, the drop optical fiber cable and the indoor optical fiber cable are sometimes housed and laid in a pipe in a column, in a house, or in the ground, but may be bent to a small diameter in the pipe during laying. In addition, when laying along a wall surface, there are many occasions where it is bent to a small diameter, such as being bent to a small diameter at a corner of the wall surface. And when the tensile strength body of the optical fiber cable was comprised with glass FRP, when bending to the small diameter, it produced a problem because it broke.

  Further, when the tensile strength member of the optical fiber cable is made of PET, it does not fold relatively even when bent to a small diameter, but plastic deformation occurs when the bending diameter is small and the bending strain becomes larger than the amount of strain in the elastic deformation region. The Young's modulus is lowered and the function as a tensile body is inferior.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber cable that satisfies the tensile properties and is less likely to be bent or have a reduced Young's modulus even when bent to a small diameter.

  In order to solve the above-mentioned problem, an optical fiber cable according to the invention of claim 1 is an optical fiber cable in which an optical fiber core and a tensile body are integrated, and the cross-sectional shape of the tensile body is flattened in a predetermined direction. It is characterized by.

  An optical fiber cable according to a second aspect of the present invention is an optical fiber cable in which an optical fiber core wire and a plurality of strength members are integrated, and the plurality of strength members are flattened in a predetermined direction as a group. It is characterized by that.

  An optical fiber cable according to a third aspect of the present invention is the optical fiber cable according to any one of the first or second aspects, wherein the cross-sectional shape of the optical fiber cable main body is flat in a predetermined direction, An optical fiber core and at least one strength member are provided in the fiber cable main body, and the strength member is flattened in the long side direction of the optical fiber cable main body.

An optical fiber cable according to a fourth aspect of the present invention is the optical fiber cable according to the third aspect, wherein the maximum value of the length in the short side direction of the flat tensile body is A (mm), and the tensile body. The total cross-sectional area of S is (mm ² ) and the Young's modulus of the tensile body is E (kgf / mm ² )
And the bending strain (A / 2 × 2) × 100 of the tensile body when the optical fiber cable main body is bent with a radius of curvature of 2 (mm) in the long side direction is 6% or less, and the optical fiber cable The tensile strain (35 / 9.8) / (E × S) × 100 of the tensile body when the main body is pulled in the longitudinal direction at 35 N is 1% or less.

An optical fiber cable according to claim 5 is the optical fiber cable according to claim 3, wherein the maximum value of the length in the short side direction of the flat strength member is A (mm), and the total strength of the strength member is cut off. The area is S (mm ² ) and the Young's modulus of the tensile body is E (kgf / mm ² ).
The bending strain (A / 2 × 20) × 100 when the optical fiber cable main body is bent with a radius of curvature of 20 (mm) in the long side direction is equal to or less than the strain amount (%) of the elastic deformation region of the tensile body. The tensile strain (35 / 9.8) / (E × S) × 100 when the optical fiber cable main body is pulled at 35 N in the longitudinal direction is 1% or less.

The relationship between bending strain and tensile strain will be described below. When two strength members 4 having a circular cross section are mounted as in the drop optical fiber cable of FIG. 1, considering the optical fiber cable main body 7, the optical fiber cable main body 7 is bent, When bending at a radius of curvature R (mm), the bending strain ε of the tensile body 4 is
ε = (d / 2R) × 100% (1)
It is. Here, d (mm) is the diameter of the strength member 4. When this bending strain becomes large, for example, glass FRT breaks, and in the case of PET, the Young's modulus decreases. It is desirable to keep this bending strain as small as possible even when bending with a small curvature. For this purpose, it is effective to reduce the diameter d (mm) of the strength member as shown in the equation (1). However, if the diameter of the strength member is reduced, the cross-sectional area is reduced correspondingly and the strength function is lowered. Now, for example, it is assumed that a conventional tensile body having a circular cross section needs to have a diameter d (mm) or less in order to suppress bending of the tensile body and decrease in Young's modulus due to bending strain. Then, it is assumed that the outer diameter of the strength member needs to be 2d (mm) or more because of the demand on the tension characteristics of the optical fiber cable. A conventional tensile strength member having a circular cross-section cannot naturally satisfy these two requirements at the same time.

  Therefore, according to the first aspect of the present invention, the bending strain is suppressed with respect to a predetermined curvature with respect to the bending in the direction perpendicular to the long side direction of the strength body by making the strength body a flat shape. The tensile strength characteristics can also be satisfied by increasing the cross-sectional area in the long side direction.

  According to the configuration of claim 2, each of the plurality of strength members is not necessarily flattened, but the plurality of strength members are configured to be flattened as a group, so that the strength members are flattened. The same effect as the case can be produced.

  Further, the main body of the drop optical fiber cable or indoor optical cable is generally flattened in a predetermined direction (left and right direction in FIGS. 1 and 2) as shown in FIGS. It is advantageous in handling to bend easily in a direction perpendicular to the direction (vertical direction in FIGS. 1 and 2). According to the structure which concerns on Claim 3, since the flat direction of an optical fiber cable main-body part and a tensile strength body corresponds, the suitable optical fiber cable which is easy to bend | curve with respect to the bending of a direction perpendicular | vertical to a long side direction is provided. it can.

  According to the configuration of the fourth aspect, even when the optical fiber cable is bent with a radius of curvature of 2 mm smaller than the allowable bending radius of 30 mm of a normal optical fiber core wire, the bending strain of the tensile strength body is suppressed to 6% or less. Thus, it is possible to suppress the occurrence of bending due to bending of the tensile strength body. Further, even when a normally assumed 35 N tension is applied, it is possible to suppress the breakage of the optical fiber core wire by suppressing the tensile strain of the strength member to 1% or less.

  According to the configuration of the fifth aspect, even when the optical fiber cable is bent with a radius of curvature of 20 mm which is smaller than the allowable bending radius of 30 mm of a normal optical fiber core wire, the bending strain of the tensile strength body is elastically deformed. By suppressing the strain amount to be equal to or less than the strain amount, a decrease in Young's modulus due to bending of the tensile body can be suppressed. In addition, even when a normally assumed 35 N tension is applied, the tensile strain of the strength member is suppressed to 1%, thereby preventing the optical fiber core from being broken.

The best mode recognized by the inventors for carrying out the present invention will be described below. 3, the optical fiber cable main body 70 of the optical fiber cable 10 is formed in a shape flattened in the left-right direction in FIG. An optical fiber core wire 50 is disposed at the centroid of the optical fiber cable main body 70, and the optical fiber core wire 50 is interposed between the optical fiber cable main body 70 and a line parallel to the flat direction of the optical fiber cable main body portion 70 passing through the centroid. Two strength members 40 are arranged. Each of the two strength members 40 has a length in the short side direction A (mm) and a length in the long side direction B (mm), and is flat in the long side direction of the optical fiber cable main body. In this case, the maximum value in the short side direction of the flat tensile body 40 is A (mm), and the total cross-sectional area S of the tensile body 40 is 2 (lines) × A × B (mm ² ).

  By the way, in the optical fiber cable having the conventional structure shown in FIGS. 1 and 2, the conventional tensile strength member 4 having a circular cross section needs to have a diameter d (mm) or less in order to suppress bending strain. In the case where the outer diameter of the strength member 4 needs to be 2d (mm) or more due to characteristics requirements, for example, it is assumed that it is configured as shown in FIG. Each material is the same as the conventional product. In this case, if A = d (mm) from the viewpoint of suppressing bending strain, the bending strain can be sufficiently suppressed. From the viewpoint of tensile strength characteristics, the diameter of the tensile body is 2d (mm) if B = πd (mm). In this case, the cross-sectional area is the same as in the above case, and the tensile strain can be sufficiently suppressed.

In this embodiment, it is also possible to reduce the bending rigidity while maintaining the tensile characteristics. For example, when A = d (mm) and B = πd (mm) as described above, a cross section around an axis in the bending direction (vertical direction in FIG. 3) serving as an index of bending rigidity for one of the strength members 40. The second moment I ₃ is
I ₃ = (1/12) A ³ × B = (1/12) πd ⁴ (2)
It is. On the other hand, when the diameter of the strength member 4 is d (mm) in FIG. 1 and the cross-sectional area of the strength member 4 is the same, the bending direction (up and down in FIG. Direction) and the secondary moment of inertia I ₁ is
I ₁ = 4πd ⁴ (3)
Since I ₃ <I ₁ , in this embodiment, it is possible to reduce the bending rigidity without deteriorating the tensile strength characteristics and to easily bend the optical fiber cable. When laying the optical fiber cable, the work of connecting it to the pipe or connecting it to the optical equipment is performed, but the optical fiber cable that bends more flexibly has good workability and is necessary for the optical fiber cable of tensile strength characteristics. It becomes possible to improve workability without impairing the characteristics.

For example, in the optical fiber cable 1 shown in FIG. 2, it is assumed that the outer diameter of the tensile body 4 made of glass FRP is 0.4 (mm) in terms of tensile strength. If it is necessary to bend this to a radius of curvature of 2.0 (mm), the FRP itself will be broken and cannot be used as it is. Therefore, if the outer diameter of the strength member 4 is reduced to 0.2 (mm), the bending strain can be ½ that of the outer diameter of 0.4 (mm), so that bending does not occur. However, since the cross-sectional area decreases, the tensile strength characteristics deteriorate. Here, in the embodiment (A), the structure shown in FIG. 3 is adopted, and the same cross-sectional area as that in the case where the tensile body 40 has an outer diameter of 0.4 (mm) is maintained and bending is applied due to the necessity of tensile strength characteristics. In order to suppress the folding, rectangular glass FRP having an A dimension of 0.2 (mm) and a B dimension of 0.63 (mm) in FIG. 3 is employed. As a result, it is possible to provide a tensile body 40 equivalent to the case of the outer diameter of 0.2 (mm) with respect to bending while maintaining the tension-elongation characteristic equivalent to that of the outer diameter of 0.4 (mm). Become. This example is shown in the table below. The Young's modulus of the tensile body used here is 5000 (kgf / mm ² ). In addition, the tension strain when the maximum tension value 35N applied to the drop optical fiber cable is actually applied to the optical fiber cable main bodies 7 and 70 is the outer diameter of the strength member 4 in the embodiment (A). Is equivalent to 0.4 mm.

Table 1

表２より、抗張力体の曲げ歪（Ａ／２×２）×１００が６％以下となる実施例（ロ）、（ハ）、（ニ）においては折れが生じないためより好適であることが分かる。 As another embodiment, the case where the tensile body is a fiber reinforced tensile body such as glass FRP will be considered more specifically. In the case of a fiber reinforced tensile body, bending occurs when the bending strain exceeds a certain value, and therefore the tensile body needs to be equal to or less than a certain bending strain. In addition, since the optical fiber cable is required to have a predetermined tensile strength characteristic, there is a possibility that the optical fiber cable that is mounted will be broken unless the tensile strength characteristic of the tensile strength body exceeds a certain level. First, in the optical fiber cable having the structure shown in FIG. 3, Examples (B), (C), (D) and Example (E) in which the dimension A of the tensile body 40 is changed are created. An experiment was performed in which bending was performed in a direction perpendicular to the direction so that the radius of curvature of the strength member 40 was 2.0 (mm) to obtain a limit value of bending strain. As the material of the tensile body 40, glass FRP having a Young's modulus of 5000 (kgf / mm ² ) was used. The results are shown in Table 2.
Table 2

From Table 2, it is more preferable that the bending strain (A / 2 × 2) × 100 of the tensile strength body is 6% or less in Examples (B), (C), and (D) because no bending occurs. I understand.

表３をみればわかるように、張力歪が１．０％以下ではケーブルを引っ張っても心線の破断は生じないが、それを超えると心線の破断が生じてくる。したがってガラスＦＲＰ等の繊維強化型プラスチックのような材料で抗張力体を作成する場合、抗張力体の張力歪（３５／９．８）／（Ｅ×Ｓ）が１％以下となることが好ましい。これは、材質が強化繊維プラスチックにかぎらず曲げが入ると折れ又は座屈が生じる材料全般にあてはまり、たとえば抗張力体としてアクリル棒やガラス棒などを使用する場合にもあてはまる。 Next, experiments on tensile properties were conducted. An optical fiber cable with the cross-sectional area A × B of the tensile strength member changed in the structure shown in FIG. 3 was prepared as Examples (F), (G), and (H), and a tensile load of 35 N was applied to the optical fiber cable. The presence or absence of optical fiber core wire breakage in the optical fiber cable was confirmed. The material is glass FRP with a Young's modulus of 5000 (kgf / mm ² ), and the cable length is 10 m. The results are shown in Table 3.

Table 3

As can be seen from Table 3, when the tensile strain is 1.0% or less, the cable does not break even when the cable is pulled, but when it exceeds that, the cable breaks. Accordingly, when the tensile body is made of a material such as fiber reinforced plastic such as glass FRP, it is preferable that the tensile strain (35 / 9.8) / (E × S) of the tensile body is 1% or less. This applies not only to the reinforcing fiber plastic but also to all materials that will bend or buckle when bent, such as when an acrylic rod or glass rod is used as the strength member.

実施例（リ）、（ヌ）、（ル）において抗張力体の材料は上述の通り弾性変形領域の歪量が０．６％のＰＥＴであり、曲げ歪が弾性変形領域の歪量を超えるとヤング率の劣化が生じることが分かる。そこで曲げ歪の値を弾性変形領域の歪量以下に抑えることで抗張力体のヤング率の減少を抑制できる。このため、抗張力特性の低下を抑制でき好適である。これはＰＥＴだけでなく、ＰＢＴ（ポリブチレンテレフタレート）、ポリフッ化エチレンなどのポリエチレン、ナイロンその他のエンジニアリングプラスチック一般、また金属まで適用でき、曲げ歪みによって折れが生じるのではなく、癖が残ってヤング率の低下が問題となるような材料一般にあてはまる。 Other embodiments are described below. Some materials do not fold or buckle when bent slightly. For example, when a rod made of PET or the like is not bent but is bent to a small diameter, wrinkles are generated, and the Young's modulus of the wrinkled portion is reduced from a value before bending. Such a material has a problem that the function as a tensile strength body is lowered by bending. In order to solve such a problem, there is a method of reducing the diameter of the strength member in order to reduce the strain at the time of applying the bending as in the case of the glass FRP. Accordingly, in the optical fiber cable having the structure shown in FIG. 3, Examples (Li), (N), and (Le) in which the dimension A of the strength member 40 is variously changed are created, and the direction perpendicular to the long side direction of the strength member 40 is created. Experiments were performed to determine the bending strain when bending was performed so that the radius of curvature of the strength member 40 was 20 mm, and the ratio of Young's modulus to the bending before the bending. As the material of the strength member 40, PET having a strain amount of 0.6% in the elastic deformation region was used. The results are shown in Table 4.
Table 4

In Examples (L), (N), and (L), the material of the tensile body is PET having a strain amount of 0.6% in the elastic deformation region as described above, and the bending strain exceeds the strain amount in the elastic deformation region. It can be seen that the Young's modulus deteriorates. Therefore, by suppressing the value of the bending strain to be equal to or less than the amount of strain in the elastic deformation region, it is possible to suppress the decrease in Young's modulus of the tensile body. For this reason, the fall of a tensile strength characteristic can be suppressed and it is suitable. This can be applied not only to PET, but also to PBT (polybutylene terephthalate), polyethylene such as polyfluorinated ethylene, nylon and other engineering plastics, and even metals. This applies to general materials in which a decrease in the thickness is a problem.

このように実施例（ヲ）によると、剛性を約１／３まで下げながら張力歪は従来例（３）と同等に保つことができることが分かる。
この曲げ剛性はＡとＢのコントロールで丸型よりも大きくすることも可能であり、柔軟性よりも反発力が必要なケーブル種には曲げ剛性をアップして対応することも可能となる。 As another example, the tensile strength characteristics and the bending rigidity are compared with the conventional example. An optical fiber cable having the structure shown in FIG. 2 (conventional example 3) and an optical fiber cable having the structure shown in FIG. The cross section of the strength member is as shown in Table 5. Table 5 shows the bending strain and the tensile strain when 35 N tension is applied to the optical fiber cable for the conventional example 3 and the example (v).

Table 5

Thus, according to the embodiment (W), it can be seen that the tension strain can be kept equal to the conventional example (3) while the rigidity is lowered to about 1/3.
This bending rigidity can be made larger than that of the round shape by controlling A and B, and it is possible to cope with a cable type that requires a repulsive force rather than flexibility by increasing the bending rigidity.

  Other embodiments will be described below. As an embodiment of the present invention, as shown in FIG. 4, a support line 6 may be added. Further, the optical fiber core wire 50 is not limited to a single core and may be multi-core. Note that. When the number of optical fiber cores is multiple, various types of tape cores such as 2, 3, 4, 5, 6, 8, 12, 12, and 16 can be used.

  As an embodiment of the present invention, the cross-sectional shape, number, and location of the strength members can be appropriately changed. For example, it may be formed in an elliptical shape as shown in FIG. In this case, the maximum value of the length in the short side direction is A1 (A1> A2), and the total cross-sectional area of the tensile body is the sum of the tensile bodies 41 and 42. As shown in FIG. 5B, four strength members may be provided. In this case, the maximum value of the length in the short side direction is A3, and the total cross-sectional area of the tensile body is the sum of the tensile bodies 43, 44, 45, and 46. Further, as shown in FIG. 5C, for example, three circular strength members 401 to 403 may be arranged in the long side direction of the optical fiber cable main body 70. In this case, even if each strength member has a circular cross section, when the group of strength members 401 and 402 is viewed as a strength member, it can be regarded as a flat strength member. In this case, the maximum value of the length in the short side direction is A4, and the total cross-sectional area of the tensile body is the sum of the tensile bodies 401, 402, and 403. Of course, the number of strength members having a circular cross section may be 20, for example, 20 as shown in FIG. Also in this case, the strength members 404 to 413 and 414 to 423 can be regarded as flat strength members as a group. The maximum value of the length in the short side direction is A5, and the total cross-sectional area of the tensile body is the sum of the tensile bodies 404 to 423.

  As another embodiment of the present invention, as shown in FIG. 6, various shapes such as an elliptical shape can be applied to the cross-sectional shape of the optical fiber cable main body 70, and the position of the optical fiber core wire 50 is also the optical fiber cable main body. The centroid of the part 70 may not be used.

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 an example of the optical fiber cable which concerns on this invention. The figure which shows the 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 figure which shows the cross section of an example of the optical fiber cable which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drop optical fiber cable 2 Optical fiber cable 2 'Indoor optical fiber cable 3 Coating | covering material 4, 40-46, 401-423 Strength member 5, 50 Optical fiber core wire 6 Support line 7, 70 Optical fiber cable main-body part 8 Notch 10 Fiber optic cable

Claims (5)

  An optical fiber cable in which an optical fiber core and a tensile body are integrated, wherein the cross-sectional shape of the tensile body is flattened in a predetermined direction.   An optical fiber cable in which an optical fiber core wire and a plurality of strength members are integrated, and the plurality of strength members are flattened in a predetermined direction as a group.   3. The optical fiber cable according to claim 1, wherein a cross-sectional shape of the optical fiber cable main body is flat in a predetermined direction, and the optical fiber core and at least one of the optical fiber core wire are provided in the optical fiber cable main body. An optical fiber cable comprising a tensile body, wherein the tensile body is flattened in the long side direction of the optical fiber cable main body. 4. The optical fiber cable according to claim 3, wherein a maximum value in a short side direction of the flat strength member is A (mm), a total cross-sectional area of the strength member is S (mm ² ), and a strength member. Young's modulus of E (kgf / mm ² )
And the bending strain (A / 2 × 2) × 100 of the tensile body when the optical fiber cable main body is bent with a radius of curvature of 2 (mm) in the long side direction is 6% or less, and the optical fiber cable An optical fiber cable, wherein a tensile strain (35 / 9.8) / (E × S) × 100 of the strength member when the main body is pulled in the longitudinal direction at 35 N is 1% or less. 4. The optical fiber cable according to claim 3, wherein a maximum value in a short side direction of the flat strength member is A (mm), a total cross-sectional area of the strength member is S (mm ² ), and a strength member. Young's modulus of E (kgf / mm ² )
The bending strain (A / 2 × 20) × 100 when the optical fiber cable main body is bent with a radius of curvature of 20 (mm) in the long side direction is equal to or less than the strain amount (%) of the elastic deformation region of the tensile body. A tensile strain (35 / 9.8) / (E × S) × 100 when the optical fiber cable main body is pulled at 35 N in the longitudinal direction is 1% or less.

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