JP2018189962A - Optical fiber cable and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber cable which protects optical fibers from rat bites and makes it easy to take out optical fibers.SOLUTION: An optical fiber cable 10A comprises a core 8 having multiple optical fibers 1a, an outer sheath 5, and a reinforcement layer 4 located between the core 8 and the outer sheath 5. The reinforcement layer comprises multiple layer elements 4a, 4b that are bonded together, where each of the multiple layer elements is formed of sheet materials obtained by bonding and fixing juxtaposed fibers using an adhesive.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical fiber cable and a method for manufacturing an optical fiber cable.

  An optical fiber cable built, laid, or buried (hereinafter simply referred to as “installation”) in a mountain or forest is damaged by the wild animals such as mice, squirrels, and woodpeckers, and the optical fiber inside the cable is damaged. There is a case. In order to prevent such damage, it is conceivable to protect the optical fiber by covering it with a reinforcing sheet formed of a steel plate. However, when a steel plate is used as the reinforcing sheet, the optical fiber cable becomes heavy, or the steel plate causes metal fatigue when the optical fiber cable is twisted. For this reason, the structure which prevents the above biting is proposed by forming a sheath twice and providing a reinforcement layer between these sheaths, without using a steel plate.

  For example, Patent Document 1 below discloses an optical fiber cable in which a reinforcing layer (exterior 20) is provided between an inner sheath and an outer sheath. The reinforcing layer is formed by impregnating a glass fiber or the like with a thermosetting resin and curing the thermosetting resin.

  Patent Document 2 below discloses an optical fiber cable in which a protective layer is provided on the outside of a core having an optical fiber. The protective layer includes an outer sheath (outer layer) that forms the cable surface, an inner sheath (inner layer) provided inside the outer sheath, and a reinforcing layer provided between the sheaths. This reinforcing layer is formed of a mesh material made of glass cloth.

JP-A-8-190036 JP 2012-181300 A

  By the way, in such an installation work of the optical fiber cable or the like, an operation of grasping and pulling the outer sheath is often performed. When such an operation is performed, a strong tension acts on the outer sheath in the longitudinal direction, and the outer sheath extends in the longitudinal direction. At this time, if the elongation in the longitudinal direction of the inner sheath is smaller than the elongation in the longitudinal direction of the outer sheath, the inner sheath enters the inner side in the longitudinal direction of the outer sheath. When such a phenomenon occurs, when the longitudinal tension acting on the outer sheath is released, the optical fiber or the like meanders in the outer sheath, leading to an increase in transmission loss of the optical fiber.

Moreover, in such an optical fiber cable, an optical fiber may be taken out from the inside during intermediate post-branching work or the like. In order to perform such an intermediate post-branch operation more smoothly, it is necessary to reduce the labor when removing the reinforcing layer.
With respect to these problems, the configurations of the optical fiber cables described in Patent Document 1 and Patent Document 2 have room for improvement.

  The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide an optical fiber cable that can easily take out an optical fiber while protecting the optical fiber from biting.

  In order to solve the above problems, an optical fiber cable according to a first aspect of the present invention includes a core having a plurality of optical fibers, an outer sheath, and a reinforcing layer positioned between the core and the outer sheath. The reinforcing layer has a plurality of layer elements bonded to each other, and each of the plurality of layer elements is formed of a sheet material in which a plurality of parallel fibers are fixed with an adhesive. .

According to the optical fiber cable according to the first aspect, the plurality of layer elements constituting the reinforcing layer are formed of a sheet material in which a plurality of parallel fibers are fixed with an adhesive. Each layer element can be easily torn along the extending direction. Therefore, the reinforcing layer can be easily removed and the optical fiber can be taken out from the cable during the intermediate post branching operation. On the other hand, each layer element has high strength against an external force that tries to tear along the direction orthogonal to the direction in which the fibers extend, and therefore the optical fiber can be protected from biting by the reinforcing layer.
In addition, since the reinforcing layer has a multiple structure having a plurality of layer elements, even if the same portion of the outermost layer element is repeatedly bitten by an animal and the outermost layer element is displaced, The exposure of the optical fiber can be suppressed by the inner layer element.

  The method for manufacturing an optical fiber cable according to the second aspect of the present invention includes an entering step for entering a plurality of optical fibers into a pipe, and a winding step for forming a reinforcing layer by winding a plurality of sheet materials around the pipe. And a passing step of allowing the plurality of optical fibers to pass through the pipe in a state of being covered by the reinforcing layer, and a covering step of forming a sheath that covers the reinforcing layer.

  According to the second aspect, an optical fiber cable in which an inner sheath is not disposed between the reinforcing layer and the optical fiber can be stably manufactured.

  According to the above aspect of the present invention, it is possible to provide an optical fiber cable in which an optical fiber can be easily taken out while protecting the optical fiber from biting.

It is a cross-sectional view of the optical fiber cable according to the first embodiment. It is a figure explaining an example of the method of forming a reinforcement layer. It is a figure explaining the other example of the method of forming a reinforcement layer. It is a cross-sectional view of the optical fiber cable according to the second embodiment. It is a cross-sectional view of the optical fiber cable which concerns on 3rd Embodiment. It is a cross-sectional view of the optical fiber cable which concerns on 4th Embodiment. It is a figure explaining the manufacturing method of the optical fiber cable which concerns on 3rd, 4th embodiment. It is a cross-sectional view of the optical fiber cable which concerns on a comparative example.

(First embodiment)
Hereinafter, the configuration of the optical fiber cable according to the first embodiment will be described with reference to FIG. In each drawing used in the following description, the scale is appropriately changed so that the shape of each constituent member can be recognized.

  As shown in FIG. 1, an optical fiber cable 10 </ b> A according to the present embodiment is provided on a core 8 having a plurality of optical fibers 1 a, an inner sheath 3 that accommodates the core 8 inside, and an outer side of the inner sheath 3. An outer sheath 5, a reinforcing layer 4 provided between the inner sheath 3 and the outer sheath 5, and a pair of linear bodies 7 and a pair of strength members 6 embedded in the outer sheath 5 are provided.

Here, in the present embodiment, the inner sheath 3 and the outer sheath 5 are formed in a cylindrical shape having a common central axis O.
In the present embodiment, a direction along the central axis O is referred to as a longitudinal direction, and a cross section perpendicular to the longitudinal direction is referred to as a transverse cross section. In a cross-sectional view, a direction orthogonal to the central axis O is referred to as a radial direction, and a direction around the central axis O is referred to as a circumferential direction. The case where the optical fiber cable 10A or its constituent members are viewed from the outside in the radial direction is referred to as a side view.

  The core 8 includes a plurality of optical fiber units 1 each having a plurality of optical fibers 1 a and a presser winding 2 that wraps these optical fiber units 1. The plurality of optical fiber units 1 are wrapped by the presser winding 2 in a state of being twisted in an SZ shape or a spiral shape. The core 8 may be configured by wrapping one optical fiber unit 1 with the presser winding 2.

  As the presser winding 2, a nonwoven fabric, a polyester tape, or the like can be used. Moreover, you may use the water absorbing tape which provided the water absorption to the nonwoven fabric, the polyester tape, etc. as the presser winding 2. FIG. In this case, the waterproof performance of the optical fiber cable 10A can be improved. The core 8 may not have the presser winding 2.

  As the optical fiber 1a, an optical fiber core wire, an optical fiber strand, or the like can be used. The optical fiber unit 1 includes a plurality of optical fibers 1a and a binding material 1b that bundles these optical fibers 1a. The optical fiber unit 1 may be a so-called intermittently fixed tape core. When the optical fiber unit 1 is an intermittently fixed tape core wire, the plurality of optical fibers 1a are bonded to each other so as to spread in a mesh shape (spider web shape) when pulled in a direction orthogonal to the extending direction. ing. Specifically, one optical fiber 1a is bonded to the adjacent optical fibers 1a at different positions in the longitudinal direction, and the adjacent optical fibers 1a are spaced apart from each other by a certain distance in the longitudinal direction. Are bonded to each other.

In addition, the aspect of the optical fiber unit 1 included in the core 8 is not limited to the intermittently fixed tape core wire, and may be appropriately changed.
Further, the plurality of optical fibers 1 a may not be bundled by the binding material 1 b but may be wrapped by the presser winding 2 as they are.

  The inner sheath 3 is located between the core 8 and the reinforcing layer 4. Examples of the material of the inner sheath 3 include polyolefins such as polyethylene (PE), polypropylene (PP), ethylene ethyl acrylate copolymer (EEA), ethylene vinyl acetate copolymer (EVA), and ethylene propylene copolymer (EP) ( PO) resin, polyvinyl chloride (PVC), and the like can be used.

  The filament 7 is used as a lip cord for tearing the outer sheath 5. As the filament 7, a cylindrical rod made of PP or nylon can be used. The pair of filaments 7 are disposed with the core 8 sandwiched in the radial direction. In addition, the number of the line bodies 7 embedded in the inner sheath 3 may be 1 or 3 or more.

As the material of the strength member 6, for example, a metal wire (such as a steel wire), a strength fiber (such as an aramid fiber), FRP, or the like can be used.
The pair of strength members 6 are disposed with the core 8 sandwiched in the radial direction. The direction in which the pair of tensile bodies 6 sandwich the core 8 and the direction in which the pair of linear bodies 7 sandwich the core 8 are substantially orthogonal to each other.
The number of strength members 6 embedded in the outer sheath 5 may be 1 or 3 or more.

The outer sheath 5 covers the core 8, the inner sheath 3, and the reinforcing layer 4. As a material of the outer sheath 5, PO resin such as PE, PP, EEA, EVA, EP, PVC, or the like can be used.
A pair of protrusions 5 a extending along the longitudinal direction are formed on the outer peripheral surface of the outer sheath 5. Each protrusion 5a is disposed on a portion of the outer peripheral surface of the outer sheath 5 where the pair of filaments 7 are located on the radially inner side. Since the protrusion 5a is used for positioning when the outer sheath 5 is cut, another form may be adopted. For example, a concave portion that is recessed from the outer peripheral surface of the outer sheath 5 toward the inner side in the radial direction, marking with a paint, or the like may be used.
Note that capsaicin or the like may be included in the material forming the outer sheath 5. In this case, for example, an animal such as a rat can be prevented from biting the outer sheath 5.

  The reinforcing layer 4 has a first layer element 4a that is spirally wound into a cylindrical shape, and a second layer element 4b that is wound around the first layer element 4a from the outside in the radial direction and has a cylindrical shape. doing. In the present embodiment, the first layer element 4 a is wound around the inner sheath 3. The first layer element 4a and the second layer element 4b are formed of a sheet material in which a plurality of parallel fibers are fixed with an adhesive. The first layer element 4a and the second layer element 4b are bonded to each other.

As a fiber used for the sheet material used as the first layer element 4a and the second layer element 4b, glass fiber, aramid fiber, carbon fiber, metal fiber (for example, iron fiber, stainless steel fiber) and the like can be used.
The first layer element 4a and the second layer element 4b may contain different types of fibers. For example, the glass material may be contained in the sheet material that becomes the first layer element 4a, and the aramid fiber may be contained in the sheet material that becomes the second layer element 4b. In this case, as compared with the case where the same type of fiber is used for the first layer element 4a and the second layer element 4b, there are cases where the disadvantages of each fiber can be compensated while utilizing the advantages of each fiber as shown below. is there.

For example, since carbon fiber has high strength against tension, it is suitable when the first layer element 4a or the second layer element 4b is used as a tension member. On the other hand, since the unit price is high and it has conductivity, a configuration for grounding the reinforcing layer 4 may be required.
Since the glass fiber has an insulating property, a configuration for grounding is not required. Moreover, the unit price is lower than that of aramid fiber. On the other hand, compared with other materials (fibers), the strength against tension is low.

Since an aramid fiber has an insulating property, a configuration for grounding is not required. Moreover, the intensity | strength with respect to tension is high compared with glass fiber. On the other hand, for example, when the outer sheath 5 and the inner sheath 3 try to contract in a low temperature environment, the ability to suppress the contraction deformation is relatively low, and the optical fiber 1a is easily affected. Moreover, the unit price is higher than that of glass fiber.
Metal fibers have high strength against tension. Moreover, the ability to suppress the contraction deformation of the outer sheath 5 and the inner sheath 3 is high, and the optical fiber 1a is hardly affected. On the other hand, since it has electroconductivity, the structure for earth | grounding the reinforcement layer 4 may be requested | required.

  As an adhesive used for the sheet material to be the first layer element 4a and the second layer element 4b, an adhesive having a melting point lower than the extrusion temperature when the outer sheath 5 is extruded can be used. In this case, when the outer sheath 5 is extruded, the adhesive contained in the sheet material is melted, and the inner sheath 3 and the first layer element 4a, the first layer element 4a and the second layer element 4b, and the second layer. Element 4b and outer sheath 5 are fused together. Thereby, the reinforcement layer 4 adhere | attaches the inner sheath 3 and the outer sheath 5, and the inner sheath 3 and the outer sheath 5 are integrated. The reinforcing layer 4 may be bonded to the inner sheath 3 and the outer sheath 5 by adhesion or the like, not limited to the case of being fused in this way.

  When forming the reinforcing layer 4, as shown in FIGS. 2A and 2B, a sheet material that becomes the first layer element 4 a is wound around the inner sheath 3 without a gap. In addition, arrow F1 shown to Fig.2 (a)-(c) shows the direction (henceforth fiber direction F1) where the fiber contained in the sheet | seat material used as the 1st layer element 4a extends. Similarly, an arrow F2 indicates a direction (hereinafter referred to as a fiber direction F2) in which fibers included in the sheet material to be the second layer element 4b extend.

Next, as shown in FIGS. 2B and 2C, a sheet material to be the second layer element 4b is wound around the first layer element 4a from the outside in the radial direction. The direction in which the second layer element 4b is wound is the same as the direction in which the first layer element 4a is wound. At this time, as shown in FIG. 2 (c), the boundary line between the first layer elements 4a which are adjacent to each other on the surface of the inner sheath 3 and are in a tubular shape may be wound so as to be covered with the second layer element 4b. . Thereby, even if it is a case where a clearance gap arises between the 1st layer elements 4a adjacent on the surface of the inner sheath 3, this clearance gap can be covered with the 2nd layer element 4b.
When the reinforcing layer 4 is formed by the method shown in FIGS. 2A to 2C, the fiber direction F1 of the first layer element 4a and the fiber direction F2 of the second layer element 4b are seen in a side view. They are parallel to each other.

  In addition, as shown to Fig.3 (a)-(c), you may make the winding direction at the time of winding the 2nd layer element 4b into a reverse direction with the winding direction at the time of winding the 1st layer element 4a. When the reinforcing layer 4 is formed by the method shown in FIGS. 3A to 3C, the fiber direction F1 of the first layer element 4a and the fiber direction F2 of the second layer element 4b are seen in a side view. Cross each other.

  As described above, according to the optical fiber cable 10 </ b> A of the present embodiment, the reinforcing layer 4 bonds the inner sheath 3 and the outer sheath 5 to each other even if a strong tensile force is applied to the outer sheath 5 in the longitudinal direction. Therefore, the inner sheath 3 extends in the longitudinal direction together with the outer sheath 5. Thereby, it can suppress that the inner sheath 3 penetrates into the inner side of the outer sheath 5 in the longitudinal direction.

  Further, even if a tool such as an electric knife is used to open the outer sheath 5, the reinforcing layer 4 can stop the tip of the tool from moving toward the core 8. Therefore, the optical fiber 1a and the like can be prevented from being damaged by the tool. Further, the reinforcing layer 4 has a plurality of layer elements 4a and 4b bonded to each other, and each of the plurality of layer elements 4a and 4b is a sheet material in which a plurality of parallel fibers are fixed with an adhesive. Can be easily torn along the fiber directions F1 and F2. Accordingly, the reinforcing layer 4 can be easily torn and the optical fiber 1a can be taken out from the optical fiber cable 10A during an intermediate post branching operation or the like. On the other hand, the first layer element 4a and the second layer element 4b have high strength against the external force to tear along the direction orthogonal to the fiber directions F1 and F2. 1a can be protected from biting.

In addition, since the reinforcing layer 4 has a two-layer structure (multiple structure) of the first layer element 4a and the second layer element 4b, the same portion of the second layer element 4b located on the outermost side is repeatedly bitten by animals. Thus, even if the second layer element 4b is displaced, the first layer element 4a can prevent the inner sheath 3 from being exposed.
Here, when the same part of the second layer element 4b is repeatedly bitten and displaced as described above, the second layer element 4b is likely to be displaced in a direction perpendicular to the fiber direction F2. Therefore, as shown in FIG. 3 (c), the fiber direction F1 of the first layer element 4a and the fiber direction F2 of the second layer element 4b intersect each other in the side view, so that the first layer together with the second layer element 4b. The layer element 4a is less likely to be displaced, and it is possible to more reliably prevent the inner sheath 3 from being exposed due to biting.

  The first layer element 4a is wound around the inner sheath 3, and the second layer element 4b is further wound from the outside in the radial direction. With this configuration, even when a gap is generated between adjacent first layer elements 4a on the surface of the inner sheath 3 when the first layer element 4a is wound around the inner sheath 3, the gap is formed in the second sheath. It can be covered by the layer element 4b.

Moreover, you may apply | coat water absorption powder to the sheet | seat material used as the 1st layer element 4a or the 2nd layer element 4b. In this case, the water-absorbing powder applied to the surface of the reinforcing layer 4 can enhance the waterproof performance of the optical fiber cable 10A.
Further, when the sheet material (reinforcing layer 4) is formed of non-conductive fibers such as glass fibers, a current flows inside the reinforcing layer 4 without providing a configuration for grounding the reinforcing layer 4. It can be suppressed. Thereby, it can suppress that the influence by an electromagnetic field is exerted on the inside or the outside of the optical fiber cable 10A.

  The first layer element 4a and the second layer element 4b may contain different types of fibers. In this case, there is a possibility that the shortcomings of each fiber can be compensated while utilizing the advantages of each fiber as compared with the case where a common type of fiber is used for the first layer element 4a and the second layer element 4b.

(Second Embodiment)
Next, a second embodiment according to the present invention will be described. The basic configuration is the same as that of the first embodiment. For this reason, the same code | symbol is attached | subjected to the same structure, the description is abbreviate | omitted, and only a different point is demonstrated.

  As shown in FIG. 1, the optical fiber cable 10 </ b> A of the first embodiment has a pair of strength members 6. By the way, when a material having high rigidity such as a steel wire is used as such a strength member 6, the flexibility of the optical fiber cable is reduced. In particular, when a pair of strength members 6 is provided so as to sandwich the core 8, the optical fiber cables are difficult to bend in the direction in which the strength members 6 are arranged in a cross-sectional view, and the work of bundling or winding the optical fiber cables is performed. It becomes difficult to rub.

  On the other hand, since the sheet material used as the first layer element 4a and the second layer element 4b includes a plurality of glass fibers and the like, the sheet material has high tensile strength in the fiber directions F1 and F2. Yes. In addition, when the angle formed between the longitudinal direction and the fiber directions F1 and F2 of the layer elements 4a and 4b is sufficiently small in a side view, the tensile strength of the reinforcing layer 4 in the longitudinal direction is sufficiently strong.

  Therefore, as shown in FIG. 4, the optical fiber cable 10B of the present embodiment does not have the strength member 6 (see FIG. 1), and the reinforcing layer 4 receives the tension acting on the optical fiber 1a. Has been. As described above, by using the reinforcing layer 4 as a tension member, the flexibility of the optical fiber cable can be increased and the weight and manufacturing cost of the optical fiber cable can be reduced as compared with the case where the tensile body is provided. can do.

(Third embodiment)
Next, a third embodiment according to the present invention will be described. The basic configuration is the same as that of the first embodiment. For this reason, the same code | symbol is attached | subjected to the same structure, the description is abbreviate | omitted, and only a different point is demonstrated.

  As shown in FIG. 5, the optical fiber cable 10 </ b> C of the present embodiment does not have an inner sheath, and the core 8 and the outer sheath 5 are bonded by the reinforcing layer 4. If the reinforcement by the reinforcing layer 4 is sufficient, the inner sheath can be omitted as in the present embodiment.

(Fourth embodiment)
Next, a fourth embodiment according to the present invention will be described. The basic configuration is the same as that of the third embodiment. For this reason, the same code | symbol is attached | subjected to the same structure, the description is abbreviate | omitted, and only a different point is demonstrated.

As shown in FIG. 6, in the optical fiber cable 10 </ b> D of this embodiment, the strength member 6 is not embedded in the outer sheath 5. When the reinforcement by the reinforcement layer 4 is sufficient and the reinforcement layer 4 can sufficiently receive the tension acting on the optical fiber 1a, both the inner sheath and the strength member are omitted as in the present embodiment. Is also possible.
In addition, about which structure of 1st Embodiment-4th Embodiment is selected, it is good to determine according to the tension | tensile_strength, external force, etc. which act on the optical fiber cable.

(Optical fiber cable manufacturing method)
The optical fiber cables according to the third and fourth embodiments can be manufactured, for example, by a manufacturing method as shown in FIG.
First, as shown to Fig.7 (a), the some optical fiber 1a is entered in the cylindrical pipe P (entry process). As the pipe P, a highly heat-resistant material having a higher melting point than the reinforcing layer 4 and the outer sheath 5 can be suitably used. The shape of the pipe P may be cylindrical, rectangular, elliptical or the like. The optical fiber 1 a that enters the pipe P may be bundled by the binding material 1 b or may be wrapped by the presser winding 2. That is, in the entering step, a plurality of optical fibers 1a in the state of the optical fiber unit 1 or the core 8 may be entered into the pipe P.

  Next, as shown in FIG.7 (b), the some sheet material used as the reinforcement layer 4 is tightly wound around the pipe P (winding process). Thereby, the cylindrical reinforcement layer 4 which has the same shape as the pipe P is formed. At this time, as shown in FIGS. 2A to 2C, the direction in which the fibers included in the first layer element 4a extend and the direction in which the fibers included in the second layer element 4b extend are parallel to each other. In addition, a plurality of sheet materials may be wound. Or as shown to Fig.3 (a)-(c), a some sheet | seat is crossed so that the direction in which the fiber contained in the 1st layer element 4a extends and the direction in which the fiber contained in the 2nd layer element 4b extends may intersect. A material may be wound.

Next, a plurality of optical fibers 1a are passed through the pipe P while being covered with the reinforcing layer 4 (passing step). At this time, the reinforcing layer 4 is moved on the outer peripheral surface of the pipe P in accordance with the speed (linear speed) at which the optical fiber 1a passes through the pipe P. As a result, the state shown in FIG.
Next, the reinforcing layer 4 is heated as necessary (heating step). Thereby, the surface of the reinforcing layer 4 is melted and, for example, the presser winding 2 and the reinforcing layer 4 can be bonded. In the heating step, the optical fiber 1a around which the reinforcing layer 4 is wound may pass through a heating device such as a furnace after the passing step.

Next, as shown in FIG. 7D, a sheath (outer sheath 5) that covers the reinforcing layer 4 is formed (covering step). Thereby, the optical fiber cables 10C and 10D are obtained.
In addition, when the temperature at the time of extrusion molding of the outer sheath 5 is higher than the melting point of the reinforcing layer 4, the reinforcing layer 4 can be heated and melted using the heat of the outer sheath 5. In this case, the heating step and the covering step can be performed simultaneously.

According to the manufacturing method described above, it is possible to stably manufacture the optical fiber cables 10C and 10D in which the inner sheath 3 is not disposed between the reinforcing layer 4 and the optical fiber 1a.
In addition, the manufacturing method of optical fiber cable 10C, 10D is not limited above. For example, without using the pipe P, a sheet material that becomes the reinforcing layer 4 may be directly wound around the core 8.

  The above embodiment will be described below using specific examples. The following examples do not limit the present invention.

(Example 1)
In this example, an optical fiber cable 10A having the same configuration as that of the first embodiment shown in FIG. As the core 8, a 72-core core in which six 12-core intermittently fixed tape core wires were wound with a winding 2 was used. Glass fibers were employed as the fibers contained in the sheet material to be the first layer element 4a and the second layer element 4b. Further, as shown in FIG. 2C, the reinforcing layer 4 was formed so that the fiber direction F1 of the first layer element 4a and the fiber direction F2 of the second layer element 4b were parallel to each other in a side view. The thickness of the sheet material used as the first layer element 4a and the second layer element 4b was 0.25 mm and the width was 2.1 mm. That is, the thickness of the reinforcing layer 4 was 0.5 mm.

(Example 2)
In the present embodiment, as shown in FIG. 3C, the reinforcing layer 4 is formed so that the fiber direction F1 of the first layer element 4a and the fiber direction F2 of the second layer element 4b intersect each other in a side view. did. The conditions were the same as in Example 1 except for other points.

(Comparative Example 1)
As Comparative Example 1, an optical fiber cable 10E configured as shown in FIG. The optical fiber cable 10E was set to the same conditions as in Example 1 except that the reinforcing layer 4 was not provided.

(Comparative Example 2)
As Comparative Example 2, an optical fiber cable having no second layer element 4b and having only the first layer element 4a as the reinforcing layer 4 was experimentally manufactured. The conditions were the same as in Example 1 except that the second layer element 4b was not provided. That is, the thickness of the reinforcing layer 4 was 0.25 mm.

  Table 1 below shows the results obtained by leaving each of the above optical fiber cables in a gauge in which mice were raised for 7 days and confirming whether the optical fiber was damaged.

As shown in Table 1, in the optical fiber cables of Comparative Example 1 and Comparative Example 2, damage was confirmed in the optical fiber. On the other hand, in the optical fiber cable of Example 1 and Example 2, damage was not confirmed to the optical fiber.
From the above, it was confirmed that the reinforcing layer 4 has a two-layer structure of the first layer element 4a and the second layer element 4b. Moreover, it was confirmed that the thickness of the sheet material used as the first layer element 4a and the second layer element 4b is preferably 0.25 mm or more.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the first to fourth embodiments, the reinforcing layer 4 has a two-layer structure including the first layer element 4a and the second layer element 4b. However, on the radially outer side of the second layer element 4b, A layer may be provided. That is, the reinforcing layer 4 may be composed of three or more layers.
Further, when the reinforcing layer 4 has three or more layer elements, at least two layer elements may contain different types of fibers.

  Moreover, although the optical fiber cable of the said 1st Embodiment-4th Embodiment had the linear body 7 for tearing the outer sheath 5, the structure which does not have such a linear body 7 is employ | adopted. May be. In particular, when the outer sheath 5 is incised with a tool as described above, if the tip of the tool can be sufficiently stopped by the reinforcing layer 4, the outer sheath 5 is not necessary for the wire rod 7 and the tool has the required length. Can be torn. Thereby, it becomes possible to make the operation | work which takes out the optical fiber 1a easier.

  In the optical fiber cable of the first embodiment or the third embodiment, the pair of strength members 6 are embedded in the outer sheath 5, but the pair of strength members 6 are embedded in the inner sheath 3. It may be adopted.

  In addition, the constituent elements in the above-described embodiment can be appropriately replaced with known constituent elements without departing from the gist of the present invention, and the above-described embodiments and modifications may be appropriately combined.

  DESCRIPTION OF SYMBOLS 1 ... Optical fiber unit 1a ... Optical fiber 2 ... Holding winding 3 ... Inner sheath 4 ... Reinforcement layer 4a ... 1st layer element 4b ... 2nd layer element 6 ... Strength body 8 ... Core 10A-10D ... Optical fiber cable F1, F2 ... Fiber direction O ... Center axis P ... Pipe

Claims (12)

A core having a plurality of optical fibers;
An outer sheath;
A reinforcing layer positioned between the core and the outer sheath,
The reinforcing layer has a plurality of layer elements bonded together,
Each of the plurality of layer elements is an optical fiber cable formed of a sheet material in which a plurality of parallel fibers are fixed with an adhesive. The plurality of layer elements includes a first layer element and a second layer element,
The optical fiber cable according to claim 1, wherein the first layer element and the second layer element include different types of fibers.   The optical fiber cable according to claim 1 or 2, wherein the reinforcing layer has a two-layer structure having a first layer element and a second layer element. An inner sheath positioned between the core and the reinforcing layer;
4. The optical fiber cable according to claim 1, wherein the reinforcing layer adheres the inner sheath and the outer sheath to each other. 5.   The optical fiber cable according to any one of claims 1 to 4, wherein the core has a holding winding that wraps the plurality of optical fibers.   The optical fiber cable according to claim 5, wherein the presser winding is a water absorbing tape having water absorption.   7. The device according to claim 1, wherein at least one pair of strength members disposed with the core interposed therebetween is embedded in the inner sheath or the outer sheath positioned between the core and the reinforcing layer. The optical fiber cable described. The plurality of layer elements includes a first layer element and a second layer element,
In the side view, the direction in which the fibers included in the first layer element extend and the direction in which the fibers included in the second layer element extend are parallel to each other. Fiber optic cable. The plurality of layer elements include a first layer element that is spirally wound into a cylindrical shape, and a second layer element that is wound around the first layer element from a radially outer side,
The optical fiber cable according to claim 8, wherein the second layer element covers a boundary between the cylindrical first layer elements. The plurality of layer elements includes a first layer element and a second layer element,
In the side view, the direction in which the fibers included in the first layer element extend and the direction in which the fibers included in the second layer element extend intersect each other. The optical fiber cable described.   The optical fiber cable according to claim 1, wherein water absorption powder is applied to a surface of the reinforcing layer. An approach step of allowing a plurality of optical fibers to enter the pipe;
A winding step of winding a plurality of sheet materials around the pipe to form a reinforcing layer;
Passing the plurality of optical fibers through the pipe in a state covered with the reinforcing layer; and
And a covering step for forming a sheath for covering the reinforcing layer.

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