JP2015225168A - Optical cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress increase in transmission loss generated in an optical cable when the optical cable is bent.SOLUTION: An optical cable 1 includes at least one optical fiber ribbon 8a to 8f having a plurality of coated optical fiber 9 arranged in parallel and a sheath 3a provided so as to cover the optical fiber ribbon 8a to 8f. In a cross section orthogonal to the longer direction DL of an optical cable 1, optical fiber ribbon 8a, 8f, 8c, and 8d are disposed at a misaligned position from the center line of flexure of the optical cable 1. There are stress concentration zones 13a and 13b that are established in the cross section at a position opposing to the optical fiber ribbon 8a, 8f, 8c, and 8d and can intensively provide part of optical fiber ribbons 8a, 8f, 8c, and 8d with stress.

Description

  The present invention relates to an optical cable having a tape core.

  In recent years, with the spread of the Internet, FTTH (Fiber to The Home) that realizes a high-speed communication service by introducing an optical fiber into a general home is rapidly expanding. An optical cable used for FTTH contains a large number of optical fiber cores.

  In particular, as an optical cable that accommodates a large number of optical fiber cores, a tape-stacked optical cable in which a plurality of optical fiber core wires covered with a resin are stacked in a plurality of stages has been proposed (see, for example, Patent Document 1). ).

JP 2003-295011 A

  However, in the tape laminated optical cable disclosed in Patent Document 1, the tape core wire is disposed at a position shifted from the bending center line of the optical cable passing through the support line and the tension member in the cross section orthogonal to the longitudinal direction of the optical cable. Yes.

  For this reason, when the optical cable is bent, a compressive stress acts on the tape core located inside the bend, so the tape core located inside the bend is displaced with respect to the sheath and meanders in the longitudinal direction. There is a fear. As described above, when the optical cable is bent, the transmission loss of the optical cable may increase.

  It is an object of the present invention to provide an optical cable that can suppress an increase in transmission loss that occurs when the optical cable is bent.

  An optical cable according to an aspect of the present invention is an optical cable including at least one tape core having a plurality of optical fiber cores arranged in parallel and a sheath provided to cover the tape core. In the cross section orthogonal to the longitudinal direction of the optical cable, the tape core wire is disposed at a position shifted from the center line of bending of the optical cable, and is provided at a position facing the tape core wire in the cross section. And a stress concentrating portion capable of concentrating stress on a part of the tape core wire.

  According to the present invention, it is possible to suppress an increase in transmission loss that occurs when an optical cable is bent.

It is sectional drawing which shows the optical cable which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the optical cable which concerns on a reference example. (A) It is the figure which expanded and showed the tape cable core of the optical cable shown in FIG. 2, and its vicinity. (B) It is AA sectional drawing of the optical cable shown by FIG. (A) It is sectional drawing which expanded and showed the tape core wire of the optical cable shown in FIG. 1, and its vicinity. (B) It is AA sectional drawing of the optical cable shown by FIG. It is sectional drawing which shows the optical cable which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the optical cable which concerns on other embodiment of this invention. It is sectional drawing which shows the modification of the projection part formed in the sheath of the optical cable which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the modification of the optical cable which concerns on the 1st Embodiment of this invention.

[Description of Embodiment of the Present Invention]
An outline of an embodiment of the present invention will be described.
(1) at least one tape core having a plurality of optical fiber cores arranged in parallel;
A sheath provided to cover the tape core;
An optical cable comprising:
In the cross section orthogonal to the longitudinal direction of the optical cable, the tape core wire is disposed at a position shifted from the bending center line of the optical cable,
An optical cable provided with a stress concentrating portion that is provided at a position facing the tape core in the cross section and capable of intensively applying stress to a part of the tape core.

  According to the said structure, the stress concentration part which can give stress intensively to a part of tape core wire in the direction orthogonal to the longitudinal direction of an optical cable is provided. Therefore, when an optical cable is bent, stress is concentrated on a part of the tape core, so that the stress can resist the compressive stress generated in the tape core inside the bend. The occurrence of meandering can be suppressed. In this way, it is possible to suppress an increase in transmission loss that occurs when the optical cable is bent.

  (2) The optical cable according to item (1), wherein the stress concentration portion is constituted by a protruding portion facing the tape core wire of the sheath.

  According to the above configuration, the protrusions facing the tape core wire of the sheath concentrate stress on the tape core wire, thereby suppressing the meandering of the tape core wire. Moreover, it is possible to implement | achieve a stress concentration part by forming a projection part in the opposing surface of a sheath by extrusion molding.

(3) further comprising a protective wall provided between the facing surface of the sheath facing the tape core and the tape core, and having a protrusion protruding toward the tape core;
The optical cable according to item (1), wherein the stress concentration portion is configured by a protruding portion of the protective wall.

  According to the said structure, the meandering of a tape core wire is suppressed because the protrusion part formed in the protective wall concentrates stress on a tape core wire. Moreover, it is possible to implement | achieve a stress concentration part by previously forming a projection part in a protective wall. In this case, the stress concentration portion can be easily formed as compared with the structure in which the projection is formed on the sheath.

(4) The tape core wire is laminated in three stages in a direction perpendicular to the bending center line of the optical cable,
Of the tape cores laminated in the three stages, the central tape core is disposed on the center line,
The stress concentration portion is any one of items (1) to (3), wherein stress can be applied intensively to the tape core wires disposed on both sides of the central tape core wire. Optical cable.

  According to the above configuration, when the optical cable is bent, among the tape core wires arranged on both sides of the central tape core wire, the tape core wire (hereinafter referred to as the inner tape core wire) arranged inside the bending center line. Compressive stress acting in the longitudinal direction occurs. Further, a tensile stress acting in the longitudinal direction is generated on a tape core wire (hereinafter referred to as an outer tape core wire) arranged outside the center line of bending. Here, when the optical cable is bent, stress is applied intensively to a part of the inner tape core wire and a part of the outer tape core wire, and the tape core wires laminated in three stages are separated from both sides by the stress concentration portion. It is gripped firmly. Thus, this structure can counter the compressive stress which arises in an inner side tape core wire, and can suppress the meandering of an inner side tape core wire.

(5) The tape core wire is disposed adjacent to a plurality of rows in the direction of the center line,
The stress concentration portion is any one of items (1) to (4) capable of intensively applying stress to the optical fiber core wire in the vicinity of the boundary between the adjacently disposed tape core wires. The optical cable according to one.

  According to the above configuration, stress is concentrated on the optical fiber core wire in the vicinity of the boundary between the tape core wires adjacent in the direction of the center line. For this reason, meandering of two tape core wires can be suppressed by one stress concentration part.

[Details of the embodiment of the present invention]
A specific example of the optical cable according to the embodiment of the present invention will be described with reference to the drawings shown in FIGS. The present invention is not limited to the embodiments described below, and various modifications can be made within the scope of the claims and their equivalents. In the description of the embodiments, elements having the same reference numerals as those already described have the same configuration, and the details of the description are omitted.

(First embodiment)
FIG. 1 is a sectional view showing an optical cable according to the first embodiment of the present invention. The cross-sectional view shown in FIG. 1 is a cross-sectional view orthogonal to the longitudinal direction of the optical cable. As shown in FIG. 1, the optical cable 1 is a drop-type optical cable composed of a main body portion 4 and a support wire portion 6.

  The support wire portion 6 is configured to have strength to support the optical cable 1 in an aerial manner, and includes a support wire 17, a sheath 3c that covers the support wire 17, and a neck portion 3b. The support wire 17 is made of, for example, steel or glass fiber reinforced plastic. The sheath 3c is made of a thermoplastic resin, for example, a material such as flame retardant polyethylene or PVC. The neck 3b is formed integrally with the sheath 3c and is made of the same material as the sheath 3c. The neck portion 3 b connects the support wire portion 6 and the main body portion 4.

  The main body portion 4 is supported by a support wire portion 6 and includes a sheath 3a, a pair of tension members 2a and 2b embedded in the sheath 3a, and a plurality of stacked tape core wires 8a to 8f. .

  The sheath 3a is made of the same material as the sheath 3c and the neck portion 3b, and is formed integrally with the sheath 3c via the neck portion 3b. The sheath 3a is provided so as to cover the tape core wires 8a to 8f. A plurality of notches 7 extending along the longitudinal direction of the optical cable 1 are formed on the outer peripheral surface of the sheath 3a. The sheath 3a includes a hollow portion S extending along the longitudinal direction. The notch 7 makes it easy to take out the tape core wires 8a to 8f from the sheath 3a by tearing the sheath 3a. In the hollow portion S, a plurality of laminated tape cores 8a to 8f are accommodated. The sheath 3a is formed with curved protruding portions 13a and 13b so as to face the tape core wires 8a to 8f accommodated in the hollow portion S. The protruding portion 13a functions as a stress concentration portion that can apply stress to the tape core wires 8a and 8f in a concentrated manner. Similarly, the protruding portion 13b functions as a stress concentration portion that can apply stress to the tape core wires 8d and 8c in a concentrated manner.

  The sheaths 3a and 3c and the neck portion 3b are collectively formed by extrusion molding. Further, the protrusions 13a and 13b formed on the sheath 3a can be formed in a desired shape by adjusting the positional relationship between the die and the nipple, the amount of resin supply, and the extrusion linear velocity during extrusion molding. It is.

  The tension members 2a and 2b are provided so as to extend in the longitudinal direction of the optical cable 1 while being buried in the sheath 3a. Each tension member 2a, 2b consists of steel, glass fiber reinforced plastics, etc., for example. An adhesive layer (not shown) may be provided on the outer periphery of the tension members 2a and 2b. In such a case, the tension members 2a and 2b and the sheath 3 are strongly bonded. For example, polyethylene is used as the material of the adhesive layer. Thus, by providing the tension members 2a and 2b, the rigidity of the main body portion 4 can be increased, and the tape core wires 8a to 8f can be protected from external force.

  When the optical cable 1 is bent, the bending center line Lc of the optical cable 1 in the cross section orthogonal to the longitudinal direction of the optical cable 1 shown in FIG. It passes through the center point of the diameter of the line 17.

  The tape core wires 8a to 8f are provided so as to extend in parallel without being twisted in the longitudinal direction. The tape core wires 8a to 8f are covered with the sheath 3a by being accommodated in the hollow portion S of the sheath 3a. In the cross-sectional view of the optical cable 1 shown in FIG. 1, the tape core wires 8a, 8b, and 8c are laminated in three stages in a direction orthogonal to the center line Lc. Similarly, the tape core wires 8d, 8e, and 8f are laminated in three stages in the direction orthogonal to the center line Lc.

  Of the tape cores 8a, 8b, and 8c stacked in three stages, the center tape core 8b is disposed on the center line Lc. Similarly, among the tape cores 8d, 8e, and 8f laminated in three stages, the central tape core 8e is disposed on the center line Lc.

  Further, the laminated tape cores 8a, 8b, 8c and the tape cores 8d, 8e, 8f are arranged adjacent to each other in the direction of the center line Lc. In FIG. 1, six tape cores are shown, but the number of tape cores is not limited to six (3 stages × 2 columns) and can be determined as appropriate.

  Each of the tape cores 8a to 8f includes a plurality of optical fiber cores 9 (four optical fiber cores 9 are illustrated in FIG. 1) arranged in parallel with each other and a batch covering the optical fiber cores 9. And a coating layer 15. In the cross-sectional view of the optical cable 1 shown in FIG. 1, the optical fiber cores 9 in the tape cores 8 a to 8 f are arranged in a straight line and are provided so as to extend in parallel to each other in the longitudinal direction of the optical cable 1. . Since each optical fiber core wire 9 has a general optical fiber configuration, the details thereof are omitted. For example, each optical fiber core wire 9 has a double-structured glass body composed of a core layer through which light propagates and a clad layer covering the core layer, and an ultraviolet curable resin layer covering the glass body. The collective coating layer 15 covers a plurality of optical fiber cores 9 arranged on a straight line, and is made of, for example, an ultraviolet curable resin or a thermoplastic resin.

  Of the tape cores 8a to 8f, the tape cores 8b and 8e are arranged on the center line Lc. In particular, the tape cores 8b and 8e are arranged on the center line Lc so that the center line (not shown) passing through the center axis of each optical fiber core 9 of the optical fiber cores 8b and 8e substantially coincides with the center line Lc. Has been. Therefore, even if the optical cable 1 is bent, the tape core wires 8b and 8e are arranged on the center line Lc, and therefore, no compressive stress or tensile stress acting in the longitudinal direction is generated on the tape core wires 8b and 8e.

(Description of optical cable according to reference example)
FIG. 2 is a cross-sectional view showing an optical cable 100 according to a reference example. 2 and 3, elements having the same reference numerals as those described in FIG. 1 have the same configuration as in FIG.

  In the optical cable 100 shown in FIG. 2, the shape of the sheath 3d of the main body 4a is different from the shape of the sheath 3a of the main body 4 shown in FIG. Specifically, the sheath 3d is different from the sheath 3a shown in FIG. 1 in that the protrusions 13a and 13b (stress concentration portions) shown in FIG. 1 are not provided, but the other configurations are the same. . In particular, in the optical cable 100 shown in FIG. 2, the facing surfaces 14a and 14b facing the tape core wires 8a to 8f of the sheath 3d are formed as uniform flat surfaces. Here, the side surfaces of the tape core wires 8a and 8f that face the facing surface 14a are in contact with the facing surface 14a as a whole, and the side surfaces of the tape core wires 8c and 8d that face the facing surface 14b are wholly. It is in contact with the facing surface 14b.

  FIG. 3A is an enlarged cross-sectional view illustrating the tape core wires 8a to 8f and the vicinity thereof of the optical cable 100 illustrated in FIG. FIG. 3B is a cross-sectional view of the optical cable 100 shown in FIG. In particular, the cross-sectional view shown in FIG. 3B is a cross-sectional view when the optical cable 100 is viewed from above when the optical cable 100 is bent with a predetermined curvature.

  When the optical cable 100 according to the reference example is bent with a predetermined curvature as shown in FIG. 3B, the tape core wire 8b (in other words, extends along the longitudinal direction DL) disposed on the center line Lc. Compressive stress acting in the longitudinal direction DL is generated in the tape core wire 8a located on the inner side of the bending centering on the tape core wire 8b) extending along the locus Lc1 of the center line Lc. On the other hand, a tensile stress acting in the longitudinal direction DL is generated on the tape core wire 8c located outside the bend.

  Here, in the optical cable 100 according to the reference example, as shown in FIG. 3A, the facing surfaces 14a and 14b of the sheath 3d facing the tape core wires 8a to 8f are formed on a uniform flat surface. The stress exerted on the tape core 8a and the tape core 8c by the opposing surfaces 14a and 14b is evenly distributed. For this reason, the stress exerted on the tape core 8a located on the inner side of the bending by the facing surface 14b cannot resist the compressive stress acting in the longitudinal direction DL, and the tape core 8a may meander (FIG. 3B). )reference).

  In the above description, the tape cores 8a to 8c stacked in three stages have been described. However, the same phenomenon occurs in the tape cores 8d to 8f stacked in three stages adjacent to the tape cores 8a to 8c. Yes. In other words, a compressive stress acting in the longitudinal direction DL is generated on the tape core wire 8f positioned inside the bend, while a tensile stress acting on the longitudinal direction DL is generated on the tape core wire 8d positioned outside the bend. Thus, the stress exerted on the tape core wire 8f located on the inner side of the bending by the opposing surface 14b cannot resist the compressive stress acting in the longitudinal direction DL, and the tape core wire 8f is displaced with respect to the sheath 3d. It may meander in the longitudinal direction.

(Description of the operation of the optical cable according to the first embodiment)
Next, the operation of the optical cable 1 according to the first embodiment will be described with reference to FIG.

  FIG. 4A is an enlarged cross-sectional view of the tape core wires 8a to 8f and the vicinity thereof of the optical cable 1 shown in FIG. FIG. 4B is a cross-sectional view taken along the line AA of the optical cable 1 shown in FIG. In particular, the cross-sectional view shown in FIG. 4B is a cross-sectional view when the optical cable 1 is viewed from above when the optical cable 1 is bent with a predetermined curvature.

When the optical cable 1 according to the first embodiment is bent at a predetermined curvature as shown in FIG. 4B, the tape core 8b disposed on the center line Lc is the same as in FIG. 3B. (In other words, the tape core wire 8b extending along the locus Lc1 of the center line Lc extending along the longitudinal direction DL) is centered on the tape core wire 8a located inside the bend in the longitudinal direction DL. An acting compressive stress is generated. On the other hand, a tensile stress acting in the longitudinal direction DL is generated on the tape core wire 8c located outside the bend.
Similarly, a compressive stress acting in the longitudinal direction DL is generated on the tape core wire 8f positioned inside the bend, while a tensile stress acting on the longitudinal direction DL is generated on the tape core wire 8d positioned outside the bend.

  On the other hand, in the optical cable 1 according to the first embodiment of the present invention, the optical fiber core 9a which is a part of the tape cores 8a and 8f located inside the bend in the direction orthogonal to the center line Lc. , 9f is provided with a protrusion 13a that functions as a stress concentration portion that applies stress intensively. Similarly, a protruding portion 13b is provided that functions as a stress concentration portion that concentrates stress on the optical fiber core wires 9c and 9d that are part of the tape core wires 8c and 8d located outside the bend.

  Therefore, when the optical cable 1 is bent, stress is concentrated on the optical fiber cores 9a and 9f, which are part of the tape core wires 8a and 8f located inside the bend, by the protrusion 13a. Similarly, stress is intensively applied to the optical fiber cores 9c and 9d, which are part of the tape cores 8c and 8d located outside the bend, by the protrusion 13b. For this reason, the tape core wires 8a to 8c and the tape core wires 8d to 8f stacked in three stages are firmly held from both sides by the protruding portions 13a and 13b.

  In particular, when stress is intensively applied to the optical fiber cores 9a and 9f, which are part of the tape cores 8a and 8f located inside the bend, the stress is applied intensively. The positional deviation of the optical fiber core wires 9a and 9f with respect to the sheath 3a is suppressed. At this time, since the remaining optical fiber core wires 9 other than the optical fiber core wire 9a in the tape core wire 8a are integrated with the optical fiber core wire 9a via the collective coating layer 15, the remaining optical fiber core wires 9a. The displacement of the line 9 with respect to the sheath 3a is also suppressed at the same time. Similarly, since the remaining optical fiber cores 9 other than the optical fiber core 9f in the tape core 8f are integrated with the optical fiber core 9f via the collective coating layer 15, the remaining optical fiber cores are integrated. The displacement of the line 9 with respect to the sheath 3a is also suppressed at the same time.

  For this reason, the stress intensively applied to the optical fiber cores 9a and 9f, which are part of the tape cores 8a and 8f, by the protrusion 13a can counter the compressive stress acting in the longitudinal direction DL. As shown in FIG. 4B, meandering of the tape core wires 8a and 8f located inside the bend is suppressed. Therefore, when the optical cable 1 is bent, it is possible to provide the optical cable 1 that can suppress an increase in transmission loss.

  Further, in the optical cable 1 shown in FIG. 4A, the tape core wires 8a and 8f are arranged adjacent to a plurality of rows (here, two rows) in the direction of the center line Lc, and function as a stress concentration portion. The protrusion 13a is configured to concentrate stress on the optical fiber cores 9a and 9f in the vicinity of the boundary between the tape cores 8a and 8f. For this reason, it is possible to suppress meandering of the two tape core wires 8a and 8f by the single protrusion 13a.

  In the optical cable 100 according to the reference example shown in FIG. 3, in order to prevent the meandering of the tape core wires 8a and 8f located inside the bend, the rigidity of the sheath 3d itself is increased and the thickness of the sheath 3d itself is increased. However, it is not a good idea from the viewpoint of flexibility of material selection and manufacturing cost.

(Second Embodiment)
FIG. 5 is a cross-sectional view showing an optical cable 1a according to the second embodiment of the present invention. In FIG. 5, elements having the same reference numerals as those described in FIG. 1 have the same configuration as in FIG.

  The optical cable 1a shown in FIG. 5 is different from the main body 4 shown in FIG. 1 in the main body 4b. Specifically, the main body 4b includes a sheath 3e, tension members 2a and 2b embedded in the sheath 3e, a plurality of stacked tape cores 8a to 8f, and a plurality of tape cores 8a to 8f. A pair of protective walls 23 and 24 facing each other and a pair of filling members 25 facing each other via tape cores 8a to 8f are provided. The filling member 25 is made of a fibrous material such as an aramid fiber, for example.

  The sheath 3e includes a hollow portion S2 extending along the longitudinal direction. The hollow portion S2 is a space defined by the pair of protective walls 23 and 24 and the pair of filling members 25. The sheath 3e is formed with curved facing surfaces 18a and 18b so as to face the tape core wires 8a to 8f accommodated in the hollow portion S2.

  The protective walls 23 and 24 are made of, for example, polyethylene terephthalate, polyethylene naphthalate, polyamide resin, or polyester elastomer resin. Moreover, it is desirable that the protective walls 23 and 24 are made of a material harder than the sheath 3e. As a result, even if the cicada pierces the egg laying tube into the sheath 3e, the protective wall 23, 24 prevents the egg laying tube from entering the tape core wires 8a to 8f. Thus, by providing the protective walls 23 and 24, it is possible to reliably protect the tape core wires 8a to 8f from an external force such as a semi-conductor.

  The protective wall 24 is provided between the facing surface 18a of the sheath 3e and the tape core wires 8a to 8f. Similarly, the protective wall 23 is provided between the facing surface 18b of the sheath 3e and the tape core wires 8a to 8f. The protective wall 24 has a protrusion 24a that protrudes toward the tape core wires 8a to 8f. The protective wall 23 has a protrusion 23a protruding toward the tape core wires 8a to 8f. In the present embodiment, the protruding portions 23a and 24a are formed in a curved shape, but the shape of the protruding portions 23a and 24a is not limited to this, and may be a rectangular shape or the like.

  The protruding portion 23a functions as a stress concentration portion that can apply stress intensively to a part of the tape core wires 8c and 8d. Similarly, the protruding portion 24a functions as a stress concentration portion that can apply stress intensively to a part of the tape core wires 8a and 8f.

  Therefore, when the optical cable 1a is bent, stress is applied intensively to the optical fiber cores 9a and 9f, which are part of the tape cores 8a and 8f, by the protrusion 24a. Similarly, stress is concentrated on the optical fiber cores 9c and 9d, which are part of the tape cores 8c and 8d, by the protrusion 23a. For this reason, when the tape core wires 8a and 8f are located inside the bend of the optical cable 1a, the stress concentratedly applied to the optical fiber core wires 9a and 9f which are part of the tape core wires 8a and 8f is applied. It is possible to resist the longitudinal compressive stress generated in the tape cores 8a and 8f, and to suppress the meandering of the tape cores 8a and 8f.

  Similarly, when the tape cores 8c and 8d are positioned inside the bend of the optical cable 1a, stress applied intensively to the optical fiber cores 9c and 9d, which are part of the tape cores 8c and 8d, is applied. It can counter the longitudinal compressive stress generated in the tape cores 8c and 8d, and can suppress meandering of the tape cores 8c and 8f.

  Thus, when the optical cable 1a is bent, it is possible to provide the optical cable 1a that can suppress an increase in transmission loss.

  In addition, description of the effect | action of the optical cable 1a which concerns on 2nd Embodiment is the same as description of the effect | action of the optical cable 1 which concerns on 1st Embodiment mentioned above. That is, the operation of the protrusions 23a and 24a functioning as the stress concentration portion in the second embodiment is the same as the operation of the protrusion portions 13a and 13b functioning as the stress concentration portion in the first embodiment. The description of the operation is omitted here.

  In addition, the structure in which the protrusions 23a and 24a are formed on the protective walls 23 and 24 according to the present embodiment is made compared to the structure in which the protrusions 13a and 13b are directly formed on the sheath 3a according to the first embodiment. There is an advantage in easy point. That is, in this embodiment, after preparing the protective walls 23 and 24 having the protrusions 23a and 24a in advance, the sheath 3e is formed by extrusion molding. Therefore, compared with the process of directly forming the protrusions on the sheath 3e, it is not necessary to strictly adjust the positional relationship between the die and the nipple, the amount of resin supply, and the extrusion linear velocity during extrusion molding. It is possible to provide a stress concentrating part.

(Other embodiments)
FIG. 6 is a cross-sectional view showing an optical cable according to another embodiment of the present invention. In the first and second embodiments, the optical cables 1 and 1a provided with the support line portion 6 have been described, respectively, but also in the optical cable 1b provided with no support line portion as shown in FIG. Similarly, it is included in the technical scope of the present invention. In this case, the center line Lc of the bending of the optical cable passes through the center point of the diameter of each tension member 2a, 2b.
Further, as shown in FIG. 6B, the optical cable 1c in which the support line portion and the tension member are not provided is similarly included in the embodiment of the present invention. In this case, the center line Lc of the bending of the optical cable is determined on the basis of the center line of the rigidity of the entire sheath 3f.

(Modification of protrusion)
FIG. 7 is a cross-sectional view showing a modification of the protrusions 13a and 13b formed on the sheath 3a of the optical cable 1 according to the first embodiment of the present invention. In the first embodiment, the protrusions 13a and 13b are described as the protrusions formed in a curved shape. However, as shown in FIG. 7A, the protrusions 30a and 30b may be formed in a rectangular shape. Good. Here, the protrusion 30a is formed on the facing surface 31a facing the tape core wires 8a to 8f of the sheath 3g. The protruding portion 30b is formed on the facing surface 31b facing the tape core wires 8a to 8f of the sheath 3g.

  Also in this case, the protruding portion 30a functions as a stress concentration portion that can apply stress intensively to the optical fiber core wires 9a and 9f that are part of the tape core wires 8a and 8f. Similarly, the protruding portion 30b functions as a stress concentration portion that can apply stress intensively to the optical fiber core wires 9c and 9d that are part of the tape core wires 8c and 8d.

  Further, as shown in FIG. 7B, a plurality of protrusions may be formed on the same facing surface as stress concentration portions. Here, the protrusions 40a and 42a formed in a rectangular shape are formed on the facing surface 41a of the sheath 3h facing the tape core wires 8a to 8f. Furthermore, the protrusion parts 40b and 42b formed in rectangular shape are formed on the opposing surface 41b of the sheath 3h which opposes the tape core wires 8a-8f.

  Here, the protruding portion 40a functions as a stress concentration portion capable of applying stress intensively to the optical fiber core wire 9a1, which is a part of the tape core wire 8a. The protruding portion 42a functions as a stress concentration portion that can apply stress intensively to the optical fiber core wire 9f1 that is a part of the tape core wire 8f. Further, the protruding portion 40b functions as a stress concentration portion capable of concentrating stress on the optical fiber core wire 9c1 that is a part of the tape core wire 8c. The protruding portion 42b functions as a stress concentration portion that can apply stress intensively to the optical fiber core wire 9d1, which is a part of the tape core wire 8d.

  Moreover, the modification of the projection part formed in the sheath shown in FIG. 7 is each applied also to the projection parts 23a and 24a formed in the protection walls 23 and 24 shown in FIG. 5 according to the second embodiment. Is possible. That is, even when the protrusions 23a and 24a formed on the protective walls 23 and 24 are deformed into the same shape as the modification of the protrusion shown in FIG. 7, the deformed protrusions 23a and 24a are stress-concentrated. It is possible to function as a part.

  As described above, the modified example of the stress concentration portion has been described. However, compared to the facing surfaces 14a and 14b of the sheath 3d of the optical cable 100 shown as the reference example, stress is applied to a part of the tape core wire intensively. If such a configuration is possible, such a configuration functions as a stress concentration portion in the present invention.

(Modification of the optical cable according to the first embodiment)
FIG. 8 is a sectional view showing a modification of the optical cable 1 according to the first embodiment of the present invention. In the optical cable shown in FIGS. 1 to 7, a plurality of tape cores 8a to 8f (3 stages × 2 rows) are provided, but a single tape core 8g is provided as shown in FIG. The optical cable 1d is also included in the technical scope of the present invention.

  In this case, the center line Lt passing through the center point of each optical fiber core wire 9 in the tape core wire 8g coincides with the center line Lc passing through the center point of the diameter of each tension member 2a, 2b and the support wire 17. In the cross section orthogonal to the longitudinal direction of the optical cable 1d shown in FIG. 8, the optical cable 1d is disposed at a position shifted from the center line Lc. For this reason, when the optical cable 1d is bent, when the tape core wire 8g is positioned inside the bend, a compressive stress acting in the longitudinal direction of the optical cable is generated on the tape core wire 8g.

  On the other hand, in the present modification, in the cross-sectional view shown in FIG. 8, projections 50a and 50b are formed on the sheath 3i at positions facing the tape core 8g, and the projections 50a and 50b are formed on the tape core 8g. It functions as a stress concentration part that can apply stress intensively to a part.

  Therefore, when the optical cable 1d is bent, stress is concentrated on a part of the tape core wire 8g by the protrusions 50a and 50b. For this reason, when the tape core 8g is positioned inside the bend of the optical cable 1d, the stress concentratedly applied to a part of the tape core 8g counters the longitudinal compressive stress generated in the tape core 8g. And the meandering of the tape core 8g can be suppressed. Thus, when the optical cable 1d is bent, it is possible to provide the optical cable 1d that can suppress an increase in transmission loss.

  As mentioned above, although the detail of embodiment of this invention was demonstrated, it cannot be overemphasized that the technical scope of this invention should not be limitedly interpreted by description of embodiment. The technical scope of the present invention should be determined based on the claims and their equivalents.

DESCRIPTION OF SYMBOLS 1, 1a-1d Optical cable 2a, 2b Tension member 3 Sheath 3a, 3c-3i Sheath 3b Neck part 4, 4a, 4b Body part 6 Support line part 7 Notch 8a-8f Tape core wire 9, 9a-9f Optical fiber core wire 13a , 13b Protruding portions 14a, 14b Opposing surface 15 Collective coating layer 17 Support lines 18a, 18b Opposing surfaces 23, 24 Protective walls 23a, 24a Protruding portions 25 Filling members 30a, 30b Protruding portions 31a, 31b Opposing surfaces 40a, 42a 42b Protruding portions 41a, 41b Opposing surfaces 42a, 42b Protruding portions 50a, 50b Protruding portions 100 Optical cable DL Longitudinal direction Lc Center line Lc1 Trajectory Lt Center lines S, S2 Hollow portion

Claims (5)

At least one tape core having a plurality of optical fiber cores arranged in parallel;
A sheath provided to cover the tape core;
An optical cable comprising:
In the cross section orthogonal to the longitudinal direction of the optical cable, the tape core wire is disposed at a position shifted from the bending center line of the optical cable,
An optical cable provided with a stress concentrating portion that is provided at a position facing the tape core in the cross section and capable of intensively applying stress to a part of the tape core.   The optical cable according to claim 1, wherein the stress concentration portion is constituted by a protruding portion facing the tape core wire of the sheath. A protective wall provided between the facing surface of the sheath facing the tape core and the tape core, further comprising a protective wall having a protrusion protruding toward the tape core;
The optical cable according to claim 1, wherein the stress concentration portion is configured by a protrusion of the protective wall. The tape core is laminated in three stages in a direction perpendicular to the center line of bending of the optical cable,
Of the tape cores laminated in the three stages, the central tape core is disposed on the center line,
The optical cable according to any one of claims 1 to 3, wherein the stress concentration portion is capable of intensively applying stress to a tape core disposed on both sides of the central tape core. . The tape core wire is disposed adjacent to a plurality of rows in the direction of the center line,
5. The stress concentration part is capable of intensively applying stress to the optical fiber core wire in the vicinity of the boundary between the adjacently disposed tape core wires. 6. The optical cable described in 1.

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