JP2005128326A - Optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent excessive bending in which a bend radius of an optical fiber cable becomes an allowable radius of curvature or below without paying special attention to the bending degree when bending the optical fiber cable. <P>SOLUTION: In the optical fiber cable 1, tension members 5 and an optical fiber 3 which are arranged in parallel with each other in the same plane are collectively coated with a sheath 7. A plurality of grooves 11 which extend in the width direction of the cable along the plane passing through centers of the tension members 5 and the center of the optical fiber 3 are intermittently provided in the surface of the sheath 7 along the longitudinal direction of the cable. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber cable, and more particularly to an optical fiber cable in which one or more optical fibers and a strength member are integrated by being covered with a jacket.

  In recent years, as the demand for optical communication systems increases, an optical fiber cable as an optical transmission line is often used. As an optical fiber cable used for applications such as FTTH (Fiber To The Home), it is distributed and pulled down from one or more optical fibers to a multi-core optical fiber cable laid in an aerial space such as a utility pole. A drop cable (for example, refer to patent documents 1 to 3) can be mentioned. An example of an optical fiber cable used as a drop cable is shown in FIG.

As shown in FIG. 11, the conventional optical fiber cable 100 has a configuration in which a main body portion 107 and a messenger wire portion 108 are connected by a neck portion 105.
The main body 107 is formed by covering one optical fiber 101 and two strength members 102 disposed substantially at the center with a resin 103. That is, the resin 103 constitutes the outer cover of the main body 107. The two strength members 102 are disposed in parallel to each other on the same plane as the optical fiber 101, and the optical fiber 101 is disposed between the two strength members 102.

An example of the optical fiber 101 used here is one in which the outer periphery of the glass optical fiber is coated with an ultraviolet curable resin and has an outer diameter of 0.25 mm.
As the glass optical fiber, for example, a single mode optical fiber or a multimode optical fiber can be used. In addition, a colored layer may be provided on the outer periphery of the ultraviolet curable resin.

  The strength member 102 is made of steel, fiber reinforced plastic (FRP), or the like, and has a circular outer diameter in cross section. FRP is generally formed by impregnating a matrix resin into aggregated tensile fibers and then thermally curing the matrix resin. Since the optical fiber 101 and the tensile body 102 are collectively covered, the tensile body 102 receives an external force such as a tension applied to the optical fiber cable 100 and can protect the optical fiber 101 from the external force. it can.

  In addition, two notches 104 formed so that the cutting direction is directed to the optical fiber 101 are provided on the outer periphery of the main body 107 along the longitudinal direction. The notch 104 facilitates the removal of the optical fiber 101. At the time of removal, the notch 104 may be torn so that the resin 103 between the two notches 104, 104 is cut.

The messenger wire portion 108 is configured to have strength for supporting the optical fiber cable 100 in an aerial manner, and a steel support wire 106 is covered with a resin 103.
Further, the neck portion 105 is formed integrally with the main body portion 107 and the messenger wire portion 108 by, for example, thermoplastic resin, which is the same as the resin 103 of the main body portion 107 and the messenger wire portion 108.

  Here, the optical fiber cable 100 having one optical fiber 101 is illustrated, but a conventional drop cable has a plurality of optical fibers or an optical fiber tape core formed by tapering a plurality of optical fibers. Some have

In addition, since drop-type optical fiber cables are laid in a state where they are drawn indoors from aerial, there is a concern that an induced current generated by a lightning strike or the like is transmitted indoors. Therefore, there is an increasing demand for using non-inductive FRP as a tensile body instead of inductive steel wire.
For example, Patent Document 1 discloses that FRP, polyester (PET), polyaramid fiber, or the like is used as a tensile body of an optical fiber cable.

  Further, when the optical fiber cable 100 shown in FIG. 11 is drawn from the aerial into the building, the messenger wire part 108 for supporting the aerial becomes unnecessary, so the neck part 105 is torn and the main body part 107 and the messenger wire part are separated. 108 is divided. And as shown in FIG. 12, the optical fiber cable 100a comprised only by the main-body part 107 is wired in a building.

JP 2002-365499 A Japanese Patent Laid-Open No. 2000-171474 JP 2002-328276 A

However, the optical fiber cable 100a attached with the strength member 102 has a relatively high bending rigidity, and as shown in FIG. 13, when the cable is bent along a curved or bent routing route in the building, A large operating force is required, and if the cable is inadvertently bent when it is bent with force, the bending radius of the cable may be less than the allowable curvature radius.
Therefore, when bending the optical fiber cable 100a, it is necessary to carefully perform the bending operation little by little so that the bending radius is not less than the allowable curvature radius, and there is a problem that workability is not good.

Further, in the case of a cable using FRP as the tensile strength member 102, if the FRP is bent to be smaller than the allowable radius of curvature, the FRP is broken, and not only the tensile strength is lowered, but the entire cable is bent sharply. As a result, the long-term reliability of the optical fiber 101 may be reduced, or disconnection may be caused.
For this reason, FRP strength members have been expected in terms of preventing the inductive current from entering the indoors due to lightning strikes, etc., but due to the difficulty of such bending operations, practical use has been regarded as difficult.

  Therefore, an object of the present invention is to solve the above-mentioned problems, and when bending an optical fiber cable, the cable bend radius is excessively less than an allowable curvature radius without special care in bending. It is an object of the present invention to provide a good optical fiber cable that can reliably prevent bending.

The optical fiber cable of the present invention is an optical fiber cable in which a tensile body and an optical fiber, which are arranged in parallel with each other on the same plane, are collectively covered with a jacket,
A plurality of grooves extending in the cable width direction along a plane passing through the center of the tensile body and the center of the optical fiber are intermittently provided along the cable longitudinal direction on the surface of the jacket. And

Preferably, when the opening width of the groove is W, the depth is D, the interval between the grooves is P, and the allowable radius of curvature of the optical fiber is R, the groove is:
P / sin θ ≧ R (where θ = arc tan (W / 2D)
It is formed in the dimension which satisfy | fills.

  Preferably, the plurality of grooves are provided in a staggered manner along the longitudinal direction of the cable on each surface of the jacket facing each other across a plane passing through the center of the strength member and the center of the optical fiber. It is characterized by.

  Desirably, the optical fiber has a tensile strength test with a mode field diameter of 9.0 μm or less as defined by Petermann-I at a wavelength of 1.3 μm and a screening level of 1.2% or more. It is an optical fiber.

  Preferably, a support line for supporting the optical fiber cable in an aerial manner is provided continuously along the longitudinal direction of the cable.

According to the optical fiber cable of the present invention, when the cable is bent in such a direction that the outer surface of the cable provided with the groove extending in the cable width direction becomes the inner peripheral surface or the outer peripheral surface of the curve, in the portion of the groove extending in the cable width direction, Since the cross-sectional area of the jacket is small, it can be bent easily with a small operating force, and the work of bending the cable along a curved or bent routing route in the building becomes easy.
In addition, since bending work can be done with a small operating force, it becomes easier to adjust the bending, compared to the case of a conventional optical fiber cable that has been bent with a large operating force. The possibility that the bending radius of the cable becomes equal to or less than the allowable curvature radius can be prevented.

Furthermore, when the cable is bent, the resistance to the bending operation increases at once as soon as the opening edges of the groove are brought into contact with each other and closed, so the operator can bend with the resistance from the cable. It is possible to detect that the allowable limit has been approached, and to reliably prevent further bending.
In other words, when bending the cable, it is possible to detect that the bending state is approaching the allowable limit from the feel during the bending operation without taking special care to adjust the bending, and the bending radius of the cable is allowed. Excessive bending as described below can be reliably prevented.
Accordingly, it becomes possible to employ a strength member made of FRP that is vulnerable to excessive bending, and it is possible to provide an optical fiber cable that can easily prevent intrusion of an induced current due to lightning or the like by employing a strength member made of FRP.

Hereinafter, an optical fiber cable according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a partial perspective view of an optical fiber cable according to the first embodiment of the present invention. The optical fiber cable 1 according to the first embodiment has a configuration in which a tensile body 5 and an optical fiber 3 which are arranged in parallel to each other on the same plane are collectively covered with a jacket 7.

The plane on which the optical fiber 3 and the tensile body 5 are arranged in parallel with each other is a virtual line formed by translating the center line X connecting the center of the optical fiber 3 and the center of the tensile body 5 along the longitudinal direction of the cable. It is a plane.
In the present embodiment, there is one optical fiber 3. Two strength members 5 are arranged symmetrically on the center line X with one optical fiber 3 interposed therebetween.
The jacket 7 has a rectangular cross section with a long side in the cable width direction (direction along the center line X).

  As the optical fiber 3 according to the present embodiment, an optical fiber having an outer diameter of 0.25 mm, which is coated with an ultraviolet curable resin on the outer periphery of a glass-body optical fiber, is used. Further, as the glass optical fiber, for example, a single mode optical fiber or a multimode optical fiber can be used. In addition, a colored layer may be provided on the outer periphery of the ultraviolet curable resin.

  In the optical fiber 3 of the present embodiment, in terms of quality, the mode field diameter defined by Petermann-I at a wavelength of 1.3 μm is 9.0 μm or less, and the screening level is 1.2% or more. It is desirable to use one that has undergone a tensile strength test.

  When the mode field diameter is reduced, microbend loss and bending loss (macrobend loss) can be reduced. Therefore, for example, when a side pressure is applied to the optical fiber cable 1 and the glass body of the optical fiber 3 is likely to be distorted, or the optical fiber cable 1 is bent with a small bending radius to bend the glass body with a small diameter. Even when is added, an increase in transmission loss of the optical fiber 3 can be suppressed.

  The strength member 5 is made of steel, fiber reinforced plastic (FRP), or the like, and has a circular outer diameter in cross section. FRP is generally formed by impregnating a matrix resin into aggregated tensile fibers and then thermally curing the matrix resin. Since the optical fiber 3 and the strength member 5 are collectively covered with the outer sheath 7, the strength member 5 receives an external force such as a tension applied to the optical fiber cable 1, and the optical fiber 3 is applied from the external force. Can be protected.

  The jacket 7 is made of a thermoplastic resin, and is formed on the pair of cable outer surfaces 7a and 7a along the cable width direction (direction along the center line X) so that the respective cutting directions are directed to the optical fiber 3. Two notches 9 are provided along the longitudinal direction. The notch 9 facilitates the removal of the optical fiber 3, and at the time of removal, the resin layer between the two notches 9, 9 may be cut so as to be torn.

In the case of the present embodiment, since the cross-sectional shape of the jacket 7 is rectangular, the pair of cable outer surfaces 7a, 7a along the cable width direction is along a plane passing through the center of the strength member 5 and the center of the optical fiber 3. The plane extends in the cable width direction.
A plurality of grooves 11 extending in the cable width direction are intermittently provided on the pair of cable outer surfaces 7a and 7a at a constant interval P along the cable longitudinal direction.

As shown in FIG. 2, the groove 11 of this embodiment is formed in a V-shaped cross section. The groove 11 has an opening width W, a depth D, and an interval (pitch) between adjacent grooves 11. When the allowable curvature radius of P and the optical fiber 3 is R, the optical fiber 3 is formed in a size satisfying the following formula (1).
P / sin θ ≧ R where θ = arc tan (W / 2D) (1)

When the optical fiber cable 1 is bent with one outer surface 7a inside as shown in FIG. 3, the above equation (1) is shown in FIG. It means to become a different form.
In FIG. 4, the center axis position of the optical fiber 3 is represented by a center axis circle Cp, and the radius from the center of curvature O ₁ to the center axis circle Cp in a state where the cable is bent until the opening edges of the groove 11 abut each other. R ₀ is larger than the allowable radius of curvature R of the optical fiber 3.

  In the case of the present embodiment, the arrangement of the plurality of grooves 11 extending in the cable width direction of each cable outer surface 7a, 7a is shifted along the cable longitudinal direction by shifting the arrangement pitch in the cable longitudinal direction by a half pitch. They are arranged in a staggered manner.

  In the optical fiber cable 1 described above, the groove 11 extending in the cable width direction is obtained when the cable is bent in the direction of the inner peripheral surface or the outer peripheral surface when the cable outer surface 7a provided with the groove 11 extending in the cable width direction is curved. Since the cross-sectional area of the outer cover 7 is small in this part, it can be easily bent with a small operating force, and the work of bending the cable along a curved or bent routing route in the building becomes easy.

  In addition, because bending work can be done with a small operating force, it becomes easier to adjust the bending, compared to a conventional optical fiber cable that has been bent with a large operating force. There is little possibility, and the generation | occurrence | production of the excessive bending from which the bending radius of a cable is below the allowable curvature radius can be prevented.

  Further, in the optical fiber cable 1, when the cable is bent in the direction that becomes the inner peripheral surface when the cable outer surface 7a provided with the groove 11 extending in the cable width direction is curved, as shown in FIG. Before the bending radius reaches the allowable curvature radius R of the optical fiber 3, the opening edges of the grooves 11 extending in the cable width direction are in contact with each other and closed.

Then, as soon as the groove 11 is closed, the resistance to the bending operation increases at a stretch. Therefore, the operator can detect that the bending has approached the allowable limit by the resistance from the cable, and the bending can be further performed. Can be reliably prevented.
In other words, when bending the cable, it is possible to detect that the bending state is approaching the allowable limit from the feel during the bending operation without taking special care to adjust the bending, and the bending radius of the cable is allowed. Excessive bending as described below can be reliably prevented.
Accordingly, it is possible to use the FRP strength member 5 that is vulnerable to excessive bending, and it is possible to provide the optical fiber cable 1 that can easily prevent the intrusion of the induced current due to lightning or the like by using the FRP strength member 5. become.

  Further, in the optical fiber cable 1, since the mode fiber diameter and the tensile strength are compensated based on the definition of Peterman-I and the optical fiber 3 which is strong against bending is used, the coating can be easily bent. Therefore, it is possible to provide a high-performance optical fiber cable 1 with less transmission loss in accordance with the improvement in handling property and the effect of preventing excessive bending.

Needless to say, the number of the tension members 5 and the cross-sectional shape of the outer jacket 7 are not limited to those in the first embodiment, but can take various forms.
For example, like the optical fiber cable 21 according to the second embodiment of the present invention shown in FIG. 5, one optical fiber 3 and one strength member 5 are provided, and they are collectively packaged by a jacket 7 having a circular cross section. It can also be set as the structure covered.

However, in this case as well, a plurality of V-grooves 11 extending in the cable width direction along the plane passing through the center of the optical fiber 3 and the center of the strength member 5 are intermittently formed on the surface of the jacket 7 along the cable longitudinal direction. Is provided.
As described above, even when the cross-sectional shape of the outer jacket 7 is circular or when the number of the tension members 5 is one, the effect of the groove 11 can be obtained as in the case of the first embodiment. .

Further, the groove 11 in the cable width direction formed in each of the pair of cable outer surfaces 7a and 7a of the outer jacket 7 facing each other across the plane passing through the center of the strength member 5 and the center of the optical fiber 3 is shown in the above embodiment. As such, they are not necessarily the same size.
FIG. 6 shows an optical fiber cable according to the third embodiment of the present invention.
The optical fiber cable 25 of the third embodiment is provided on each of the cable outer surfaces 25a and 25b facing each other across a plane passing through the center of the tension member 5 and the center of the optical fiber 3 in order to facilitate bending of the cable. V-shaped grooves 27 and 29 extending in the cable width direction are provided.

However, in the groove 27 provided on one cable outer surface 25a, the angle θ1 and the interval P1 between the grooves are set larger than the angle θ2 of the groove 29 provided on the other cable outer surface 25b and the interval P2 between the grooves. ing.
Then, as shown in FIG. 7, the curvature radius R2 of the center axis circle Cp of the optical fiber 3 when the cable is bent until the inner groove 29 is closed with the one cable outer surface 25a facing outward is the optical fiber 3 The dimension of each part of the groove 29 is set based on the above formula (1) so as to be larger than the allowable curvature radius R (see FIG. 4).

8, the curvature radius R1 of the center axis circle Cp of the optical fiber 3 when the cable is bent until the inner groove 27 is closed with the other cable outer surface 25b facing outward is also the optical fiber 3 The dimension of each part of the groove 27 is set based on the above formula (1) so as to be larger than the allowable curvature radius R.
Further, in the present embodiment, the dimensions of the respective portions of the grooves 27 and 29 are set so that R1 = R2.

  Further, as shown in FIG. 9, an optical fiber cable 31 according to a fourth embodiment of the present invention includes an outer sheath 7 that includes strength members 5 and 5 and an optical fiber 3 that are arranged in parallel to each other on the same plane. The body portion 33 that is collectively covered, and the messenger wire portions 35 that are arranged in parallel to each other on the same plane as the strength members 5 and 5 and the optical fiber 3 of the body portion 33 are provided continuously along the longitudinal direction of the cable. A drop-type optical fiber cable.

The main body 33 constituting the optical fiber cable 31 of the fourth embodiment has the same configuration as that of the optical fiber cable 1 shown in the first embodiment. Is omitted.
The messenger wire portion 35 is configured to have strength to support the optical fiber cable 31 in an aerial manner, and a steel support wire 38 is covered with a resin 39 integrated with the outer cover 7 of the main body portion 33. . And this messenger wire part 35 is connected to the main-body part 33 through the neck part 37 by resin integral with the jacket 7 of the main-body part 33. As shown in FIG.

  In such an optical fiber cable 31, since the body portion 33 is equipped with a groove 11 that facilitates bending and suggests a bending limit, wiring work indoors is easy when the messenger wire portion 35 is disconnected. In addition, by using non-inductive FRP for the strength member 5 of the main body 33, the inductive current generated by lightning strikes and the like is prevented from entering the room, and the optical fiber cable connection devices are damaged. Can be prevented.

In the optical fiber cable according to the present invention, the cross-sectional shape of the groove provided on the surface of the jacket so as to facilitate the bending of the cable is not limited to the V-shaped cross section shown in the above embodiments.
For example, as shown in FIG. 10A, a groove 41 having a rectangular cross section can be used, and as shown in FIG. 10B, a groove 45 having a U-shaped cross section can be used.

  In any cross-sectional shape, when the bending radius of the cable is close to the allowable curvature radius of the optical fiber, the opening edge 43, 43 at the upper end in the case of the groove 41, and the upper end in the case of the groove 45 The opening edges 47 and 47 abut each other, and the resistance force against the bending operation increases at a stretch, so that the operator can detect that the bending has approached the allowable limit by the resistance force from the cable.

1 is a partial perspective view of an optical fiber cable according to a first embodiment of the present invention. It is explanatory drawing which shows the cross-sectional shape and dimension of the groove | channel shown in FIG. It is a perspective view which shows the bent state of the optical fiber cable shown in FIG. It is a schematic sectional drawing explaining the maximum bending state of the optical fiber cable shown in FIG. It is a fragmentary perspective view of the optical fiber cable which concerns on the 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the arrangement | sequence of the groove | channel of the optical fiber cable which concerns on the 3rd Embodiment of this invention. It is a schematic sectional drawing which shows the state which bent the optical fiber cable shown in FIG. 6 to the one side. It is a schematic sectional drawing which shows the state which bent the optical fiber cable shown in FIG. 6 to the other side. It is a fragmentary perspective view of the optical fiber cable which concerns on the 4th Embodiment of this invention. It is a cross-sectional view which shows the modification of the cross-sectional shape of the groove | channel in the optical fiber cable of this invention. It is a cross-sectional view of an optical fiber cable used as a conventional drop cable. It is a cross-sectional view of the state which cut away the messenger wire part from the optical fiber cable of FIG. It is a perspective view of the state which bent the optical fiber cable shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber cable 3 Optical fiber 5 Strength body 7 Outer sheath 7a Cable outer surface 11 Groove W Groove opening width D Groove depth P Groove interval R Allowable radius of curvature of optical fiber

Claims (5)

An optical fiber cable in which a tensile body and an optical fiber, which are arranged in parallel to each other on the same plane, are collectively covered with a jacket,
A plurality of grooves extending in the cable width direction along a plane passing through the center of the tensile body and the center of the optical fiber are intermittently provided along the cable longitudinal direction on the surface of the jacket. An optical fiber cable. When the opening width of the groove is W, the depth is D, the interval between the grooves is P, and the allowable radius of curvature of the optical fiber is R, the groove is:
P / sin θ ≧ R (where θ = arc tan (W / 2D)
The optical fiber cable according to claim 1, wherein the optical fiber cable is formed to a size satisfying the above. The plurality of grooves are provided in a staggered manner along the longitudinal direction of the cable on each surface of the jacket facing each other across a plane passing through the center of the strength member and the center of the optical fiber. The optical fiber cable according to claim 1 or 2. The optical fiber according to any one of claims 1 to 3 has a mode field diameter of 9.0 μm or less according to the definition of Petermann-I at a wavelength of 1.3 μm, and a screening level of 1. An optical fiber cable characterized by being an optical fiber that has undergone a tensile strength test of 2% or more. An optical fiber cable according to any one of claims 1 to 4,
An optical fiber cable, characterized in that a support line for supporting the optical fiber cable in an aerial space is continuously provided along the longitudinal direction of the cable.