0001]The present invention relates to an optical fiber unit and an optical fiber cable.
BACKGROUND
[0002]As the optical fiber unit a set of optical fiber bundling a plurality of optical fibers, a technique for constituting the optical fiber cable is known. At that time, by winding rough winding yarn bundle of optical fibers (the bundle material), while a bundle of optical fibers is prevented from falling apart, identify the optical fiber unit by the color of the bundle material the method is common.
[0003]
　In connection with such bundle material, in particular Figure 7 of Patent Document 1, when the bundling around the bundle of a plurality of optical fibers in two bundles material, the two bundles material SZ shape wound, two bonded technique bundle material in the inverted position of the winding direction is disclosed. Further, Patent Document 2, includes three or more bundles member bundling a plurality of optical fibers, the first bundle material bonded to the second bundle material at the point of contact in contact with the second bundle material while it is, at the contact point in contact with the third bundle member is joined with the third bundle material, optical fibers at the contact point between the contact point of the second bundle material and the third bundle material technology direction is reversed winding is disclosed for the bundle.
CITATION
Patent Document
[0004]
Patent Document 1: JP 2012-88454 JP
Patent Document 2: WO 2015/053146 Patent Publication
Summary of the Invention
Problems that the Invention is to Solve
[0005]
　The optical fiber unit described in Patent Document 1 and Patent Document 2, workability when taking out the optical fiber has an advantage of improving. However, when winding the width is large bundle material the thickness in the cross section of the bundle material SZ form, wound twisted bundle material occurs at the inverting portions of the direction, the bundle material with each other with respect to the optical fiber bundle sometimes they are joined in a standing shape. Due junction thus upstanding bundle material is caught up in other optical fiber bundle, there is a possibility to cause breaking of the optical fiber.
[0006]
　The present invention aims to suppress twisting in the reverse position of the winding direction of the bundle material.
Means for Solving the Problems
[0007]
　The main invention for achieving the above object, comprises an optical fiber bundle obtained by bundling a plurality of optical fibers, a plurality of bundles materials, one of the bundles member of the plurality of bundles material, said optical fiber bundle on the outer circumference of the winding while reversing the direction alternately with are wound along the longitudinal direction of the optical fiber bundle, the inverted portion of the winding direction, is joined with other bundles member, the bundle material width to thickness in the cross section is an optical fiber unit, characterized in that less than 20 times.
[0008]
　Other features of the invention will become clear by reading the description of the specification and drawings described below.
Effect of the invention
[0009]
　According to the present invention, it is possible to suppress the twisting in the reverse position of the winding direction of the bundle material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
[1] Figure 1A is a cross-sectional view of an optical fiber cable 1 having an optical fiber unit 2. Figure 1B is a perspective view of an optical fiber unit 2 of Reference Example.
FIG. 2 is an explanatory view of an optical fiber tape 7 intermittent fixed.
FIG. 3 is a diagram illustrating the sectional structure of the bundle member 10 when performing the bonding by thermal fusion.
[4] Figures 4A to 4C are cross-sectional views of a bundle member 10 for explaining a sectional shape of the bundle material 10.
FIG. 5 is an explanatory diagram explaining how to wrap the bundle member 10.
FIG. 6 is an enlarged perspective view of the vicinity of the junction point 15 of the bundle material 10 in the comparative example.
[7] FIG. 7 is a perspective view of a junction of winding direction standing bundle material 10 are joined at the inverting portions of the bundle material 10.
[8] FIG. 8 is a diagram for explaining the optical fiber unit 2 pop-out occurs in the optical fiber 8.
[9] FIG. 9 is a diagram for explaining the optical fiber unit 2 of the second embodiment.
[10] Figure 10A is a developed view of a bundle member 10 for illustrating the exposed area of the optical fiber. 10B is a developed view of another bundle member 10 for illustrating the exposed area of the optical fiber.
DESCRIPTION OF THE INVENTION
[0011]
　From the description of the specification and the drawings described below, at least the following matters will be made clear.
[0012]
　Comprising an optical fiber bundle obtained by bundling a plurality of optical fibers, a plurality of bundles materials, one of the bundles member of the plurality of bundles material, on the outer periphery of the optical fiber bundle, wrapped reverse direction alternately while, with are wound along the longitudinal direction of the optical fiber bundle, the inverted portion of the winding direction, is joined with other bundles material, the width to thickness in the cross section of the bundle material is less than 20 times it becomes clear that the optical fiber unit according to claim is. According to such an optical fiber unit, it is possible to suppress the twisting in the reverse position of the winding direction of the bundle material.
[0013]
　It is desirable width to thickness in the cross section of the bundle material is 18 times or less. Thus, it is possible to further suppress twist in the reverse position of the winding direction of the bundle material.
[0014]
　The bundle material each other, it is desirable that are joined by an adhesive. In such a case, it is particularly advantageous.
[0015]
　The number of cores of the optical fiber A, the number of the bundle material is taken as N, the optical fiber bundle periphery on the said optical fiber is exposed to area 150A / N square mm from the bundle material less it is desirable. Thus, in the bending portion of the optical fiber units, it is possible to suppress the jumping out from a gap surrounded by the bundle material between the optical fibers.
[0016]
　Area in which the optical fiber on the outer periphery of the optical fiber bundle is exposed from the bundle material is desirably 10 square mm or more. Thus, waterproofing characteristics of the bundle material it is possible to suppress the decrease.
[0017]
　A plurality of optical fiber unit, an optical fiber cable with jacket city that covers the plurality of the optical fiber unit, the optical fiber unit includes an optical fiber bundle obtained by bundling a plurality of optical fibers, a plurality comprising a bundle material, one of the bundles member of the plurality of bundles material, on the outer periphery of the optical fiber bundle, while reversing the winding direction alternately wound along the longitudinal direction of the optical fiber bundle together and, at the inverting portions of the winding direction, is joined with other bundles material, it is desirable width of the cross section to the thickness in the cross section of the bundle material is less than 20 times. Thus, it is possible to suppress the twisting in the reverse position of the winding direction of the bundle material.
[0018]
　=== Example ===
　
　FIG. 1A is a cross-sectional view of an optical fiber cable 1 having an optical fiber unit 2. Optical fiber cable 1 has a plurality of optical fiber unit 2, and a jacket 3. Optical fiber unit 2 is a structure in which a plurality of bundled optical fibers 8 in the bundle material 10. For detailed structure of the optical fiber unit 2 will be described later. Here, the optical fiber cable 1 has three optical fiber unit 2. Three optical fiber unit 2 is covered by the holding tape 5 is covering the outwardly jacket 3. The jacket 3, tension member 4A and ripcord 4B is embedded.
[0019]
　Figure 1B is a perspective view of an optical fiber unit 2 of Reference Example. Optical fiber unit 2 is a structure in which a bundle of bundle of a plurality of optical fibers 8 in the bundle material 10. Hereinafter referred a bundle of multiple optical fibers 8 and the optical fiber bundle 6. Bundles material 10 is wound on the outer periphery of the optical fiber bundle 6, thereby a plurality of optical fibers 8 are bundled so as not fall apart. Here, the optical fiber bundle 6 is constituted by bundling optical fiber tape 7 of a plurality of intermittent fixed.
[0020]
　Figure 2 is an explanatory view of an optical fiber tape 7 intermittent fixed. Intermittent fixed optical fiber tape 7, a plurality (here, 12) is an optical fiber tape 7 which is intermittently connected to the optical fiber 8 is parallel. Optical fibers 8 of the adjacent two hearts are connected by a connecting portion 9A. Between two adjacent core optical fiber 8, a plurality of connecting portions 9A are intermittently arranged longitudinally. Further, a plurality of connecting portions 9A of the intermittent fixed optical fiber tape 7, two-dimensionally in the longitudinal direction and tape width direction are intermittently arranged. Region other than the connection portion 9A between the optical fiber 8 of two adjacent heart is in a non-connecting portion 9B. The unbound portion 9B, optical fibers 8 between two adjacent mind not restrained. Accordingly, or intermittently stationary optical fiber tape 7 to rounding tubular (bundles), it is possible to collapse, it is possible to bundle a number of optical fiber 8 at a high density.
[0021]
　Note that the intermittent stationary optical fiber tape 7 constituting the optical fiber bundle 6 is not limited to those shown in FIG. For example, it may be changed the arrangement of the connecting portion 9A. It is also possible to change the number of optical fibers 8 constituting the intermittent stationary optical fiber tape 7. The optical fiber bundle 6 may not be constituted by the optical fiber tape 7 intermittent fixed, for example may be configured by bundling a plurality of single-core optical fiber 8.
[0022]
　Bundles member 10 is a member for bundling a plurality of optical fibers 8. Bundles member 10 are a plurality of binding can filamentous an optical fiber 8, the cord-like or tape-like member. Bundles material 10 is wound on the outer periphery of the optical fiber bundle 6. Optical fiber unit 2 in Figure 1B, although bundled optical fiber bundle 6 by four bundle material 10, the bundle material 10 of the optical fiber unit 2 may be four or more. In the following description, the suffix (A ~ D) the bundle material 10, which may be described by distinguishing the respective bundles member 10.
[0023]
　Bundles member 10 is colored in a predetermined color, also functions as an identification member. Bundles material 10 of the optical fiber unit 2 is colored in different colors, it can be identified. If each optical fiber unit 2 as shown in FIG. 1B has four bundle material 10, by the combination of the color of the bundle material 10, it is possible to identify each optical fiber unit 2. Further, instead of coloring the bundle material 10 may be printed an identification mark on the surface of the bundle member 10.
[0024]
　Bundles member 10 joined between, for example, when bonding a bundle material 10 (A) and bundled material 10 and (D) is carried out by using an adhesive. The adhesive used in making the bonding of the bundle material 10 to each other, for example, an adhesive of the modified olefin-based or the like using an ultraviolet curable resin or a solvent, the use of reactive adhesive such as an epoxy-based adhesive it can. Further, the bundle material 10 joining each other, rather than using an adhesive, may be by heat sealing.
[0025]
　Figure 3 is a diagram illustrating the sectional structure of the bundle member 10 when performing the bonding by thermal fusion. Bundles member 10 includes a core portion 11, and a cover portion 12. The core portion 11 is a member extending in the longitudinal direction of the optical fiber unit 2, the bundle member 10 includes a plurality of core portions 11. Covering portion 12 covers the outer periphery of the core portion 11 is a member having a lower melting point of the core portion 11 mp. Two bundle material 10 for bundling the optical fiber unit 2, the adhesiveness developed by coating 12 is heated above the melting point, is thermally fused both in the intersection. The difference in melting points between the covering portion 12 of the core portion 11 is preferably more than 20 ° C.. Preferably the melting point of the core portion 11 is 200 ~ 230 ° C., the melting point of the covering portion 12 is preferably 0.99 ~ 180 ° C.. Further, the covering portion 12 is also melted by heating be or adhesive does not adhere to the optical fiber 8 lower its adhesive force, yet it is desirable not to degrade the coating layer of the optical fiber 8.
[0026]
　4A through 4C are cross-sectional views of a bundle member 10 for explaining a sectional shape of the bundle material 10. Cross-sectional shape of the bundle material 10 may be a variety of shapes. 4A shows a case where the cross-sectional shape of the bundle material 10 is substantially rectangular. Further, FIG. 4B shows a case where the cross-sectional shape of the bundle member 10 is in the form of a substantially rectangular corner portion shown in Figure 4A are rounded. Further, FIG. 4C shows a case where the cross-sectional shape of the bundle material 10 to a substantially circular shape (including an elliptical shape).
[0027]
　Next, whether which portion in each of the shape corresponding to the thickness and width, as defined herein. In any cross-sectional shape of FIG. 4A to FIG. 4C, the thickness T of the length of the shortest portion in the cross section, to the length of the longest portion of the width W in the direction perpendicular to the thickness direction. Although FIGS. 4A to 4C show the case where the bundle member 10 is wound around the optical fiber bundle 6 without upright, even when standing bundle member 10 as will be described later, it does not change the above definition .
[0028]
　Figure 5 is an explanatory diagram explaining how to wrap the bundle member 10. Hereinafter, with reference also Figure 1B, it will be described winding how bundles member 10 with respect to the optical fiber bundle 6.
[0029]
　Bundles material 10, so as to wind around on the outer periphery of the optical fiber bundle 6 is arranged so as to draw an arc of half the circumference along the longitudinal direction of the optical fiber unit 2 (180 degrees). Then, the bundle member 10 is joined with other bundles member 10 at the junction 15. Further, the bundle material 10, the winding direction with respect to the optical fiber bundle 6 is inverted at the junction 15 with other bundles member 10. Thus, the bundle material 10 is wound on the SZ shape with respect to the optical fiber bundle 6. In the following description, with attaching a subscript AD is the junction point 15 between the bundle member 10A and bundles member 10D, by attaching a subscript BC is the junction point 15 between the bundle material 10B bundled material 10C, respectively sometimes it is distinguished the junction 15.
[0030]
　Bundles material 10, on the outer periphery of the optical fiber bundle 6, while reversing the winding directions alternately, is wound along the longitudinal direction of the optical fiber bundle 6, the inverted portion of the winding direction, another bundle member 10 It is joined to the. Thus, if separated junction at the inverting portion, the outer periphery of the optical fiber bundle 6 can open bundle member 10 which covers the mesh, it can be taken out optical fiber 8 from the optical fiber unit 2.
[0031]
　Bonding strength of the junction 15 is not destroyed in the junction 15 unexpectedly, while, it is desirable that the extent that easy separation by operator's hand. The force required to separate the junctions 15 of the bundle material 10, it is desirable less than the force required to cut the bundles member 10, the bonding strength of the bundle material 10, not more than the breaking strength of the bundle member 10 desirable. Also, two bundles member 10, after removal of the optical fiber 8 in the middle branch operations, or applying an adhesive, by or heated by the heater, it is desirable to be able to be joined again.
[0032]
　When viewed optical fiber unit 2 from one side in the longitudinal direction as shown in FIG. 5, the junction 15 so as to sandwich the optical fiber bundle 6 is arranged. For illustration here, the position of one of the junction 15 and the reference position (0 °), the position of the other junction is 180 degrees. In the reference example, to be the 180 degree position to the reference position, the junction 15AD and junction 15BC are present.
[0033]
　First, explaining how to wrap the bundle material 10A and the bundle material 10D of the four bundle material 10. Bundles member 10A is wrapped around the upper periphery of the optical fiber bundle 6 in the clockwise direction (see FIG. 5 above), at the junction 15AD bonded bundles member 10D (see FIG. 5 above), winding direction is reversed light winding on the outer periphery of the fiber bundle 6 in the counterclockwise direction (see FIG. 5 middle panel), it is bonded to the bundle material D at the junction 15ad (see FIG. 5 middle panel), again on the outer circumference of the optical fiber bundle 6 in the clockwise winding (see FIG. 5 below (or FIG. 5 above)), repeated. Further, the bundle member 10D is winding on the outer periphery of the optical fiber bundle 6 in the counterclockwise direction (see FIG. 5 above), at the junction 15AD bonded bundles member 10A (see FIG. 5 above), winding direction reversal to winding on the outer periphery of the optical fiber bundle 6 in the clockwise direction (see FIG. 5 middle panel), it is bonded to the bundle member 10A at the junction 15ad (see FIG. 5 middle panel), again counter on the outer peripheral of the optical fiber bundle 6 winding clockwise (FIG. 5 below (or FIG. 5 above) refer), repeating this. In this way, as shown in FIG. 1B, the bundle material 10A and the bundle material 10D is wound in SZ form with respect to the optical fiber bundle 6. Also, when looking at the optical fiber unit 2 as shown in FIG. 5 from one side in the longitudinal direction, two junctions 15AD are arranged so as to sandwich the optical fiber bundle 6 (juncture 15AD is 0 degrees and 180 degrees It is placed in position).
[0034]
　Similarly bundled material 10B and bundled material 10C, as shown in FIG. 1B, is wrapped SZ shape with respect to the optical fiber bundle 6. Also, when looking at the optical fiber unit 2 as shown in FIG. 5 from one side in the longitudinal direction, two junction 15BC are arranged so as to sandwich the optical fiber bundle 6 (junction 15BC is 0 degrees and 180 degrees It is placed in position).
[0035]
　
　FIG. 6 is a perspective view enlarging a vicinity of the junction point 15 of the bundle material 10 in the comparative example. Incidentally, illustrated only bundled material 10 in order to facilitate the explanation in FIG. 6 does not show the optical fiber bundle 6. As shown in FIG. 6, the bundle material 10 wound around the SZ shape, the winding direction at the junction 15 with another bundle member 10 is inverted. When reversing the winding direction of the bundle member 10, bending stress M is generated in the bundle member 10. Bending stress M, based on the center line of the bundle member 10 indicated by a broken line in FIG. 6, the compressive stress in the inner bend, the outer bending is a collective term for two stress of tensile stress.
[0036]
　Incidentally, generally bending stress generated in the member is known to be different by the cross-sectional shape. That is, the bending easiness of members depends on the cross-sectional shape. Further, the cross-sectional shape in the thickness and width are different members as such rectangular, depending on the ratio of the width to thickness, pliability is known in general different. When to bend the bundle member 10 shown in FIG. 6 in the width direction, hardly bend as becomes the greater the width W is the thickness T. When you bend the bundle material 10 in the case of certain higher there is a range W of the thickness T to the width direction, it may be impossible bear the stress only bending deformation of the member. In this case, it acts in the direction of tensile and compressive stress stress twisted, sometimes deformed twisted is the result bundles member 10.
[0037]
　Figure 7 is a perspective view of a junction of winding direction standing bundle material 10 are joined at the inverting portions of the bundle material 10. Acts in a direction in which compressive stress rises with respect to the optical fiber bundle 6, a tensile stress to act in the longitudinal direction of the optical fiber bundle 6, twisted bundles member 10, the inverted portion of the results bundle member 10 is erected It will be joined Te. By thus junction upright bundles member 10 with each other involving the optical fiber of the other optical fiber bundle 6, the optical fiber is bent locally large, it can cause an increase in transmission loss is there. Further, there is a possibility to cause breaking of the entrained optical fiber.
[0038]
　=== First Embodiment ===
　(Evaluation of entrainment characteristics by bundling material joint)
　entrainment bundle material 10 coated optical fiber by the joint between the, there is a range W of the thickness T of the bundle material joint bundle material between the case of constant or is caused by standing. Therefore, to create multiple prototype optical fiber unit cross-sectional dimension of the bundle material, evaluations were carried out properties entrainment by the junction between the bundle member 10.
[0039]
　First, the plurality of trial optical fiber unit both to set the 80-core optical fiber core wire, it is wound around the bundled material in SZ form. Method of winding a bundle material is the same as that shown in FIGS. 1B and FIG. The prototype optical fiber unit by changing the width and thickness to create multiple, rotated respectively, when contacted with another optical fiber unit, the optical fiber bundles in the other optical fiber unit, bundle materials prototype optical fiber unit junction was evaluated whether or not involved. The evaluation results are shown in the following Table 1.
[0040]
[Table 1]

[0041]
　Table 1 shows the ratio of the width of the bundle material the upper of the respective evaluation result column relative to the thickness of the bundle material. Hereinafter referred to the ratio between the width-thickness ratio. Also shows what if the lower evaluation result column is brought into contact with the other optical fiber unit is not involved in rotation by "○", "×" what is involved in rotation. Result is "○" if, can be evaluated as a good optical fiber units standing to the extent that entrainment of the optical fiber by the junction between the bundle material does not occur is suppressed.
[0042]
　Table as 1 to indicate apparent from the results, the prototype optical fiber unit of less than 20.0 width thickness ratio is evaluated as "○". Also, of the prototype optical fiber unit, which is evaluated as "○" and those width-thickness ratio of the maximum, a prototype optical fiber unit of width 1.80 mm, thickness 0.10 mm, width thickness ratio 18 it is a .0. Therefore, from the above result, the width-thickness ratio is less than 20.0, preferably 18.0 or less of the optical fiber unit, and standing to the extent that entanglement does not occur in the optical fiber is suppressed by the junction between the bundle material a good optical fiber units in.
[0043]
　(Differences in twist-friendliness of the differences in the bonding method of the bundle material)
　bundled material 10 joining each other, he said the case is performed using an adhesive, and it may be done by heat sealing. Among them, as compared with the case of thermal fusion, better if you joined using an adhesive, twisting the bundle material at the inverting portions of the winding direction is likely to occur. If this is the thermal fusion for easily slightly deform melted covering portion 12 of the bundle member 10 (see FIG. 3), is believed to become more easily bend. Thus, the optical fiber unit in the above described numerical value range, when joined with an adhesive, is particularly advantageous.
[0044]
　=== Second Embodiment ===
　
　In the above-described reference example, when bending the optical fiber unit has been added, the optical fiber through a gap surrounded by the bundle material with each other it may sometimes jump out. Jumps out portion of the optical fiber or other optical fiber unit, by being caught in the bundle material, locally bent, it was causing breakage or an increase in the optical fiber transmission loss.
[0045]
　Figure 8 is a diagram for explaining the optical fiber unit 2 pop-out occurs in the optical fiber 8. In order to facilitate the explanation in FIG. 8, only one of the multiple bundles member 10 shown, not shown for the other bundle member 10 to be bonded thereto. In the following description, it is to explain the optical fiber 8 with a subscript (A, B). When bending the optical fiber unit 2 is applied as shown in FIG. 8, line length difference in the trajectory of the optical fiber 8 each from S point to point E occurs. For example, the optical fiber 8 through the inside of the bend (A) for the optical fiber 8 through the outer bend (B), the length of the trajectory is shortened.
[0046]
　However, the optical fiber 8 (A), since the bundle member 10 is restrained wound, through a trajectory that is actually to eliminate the line length difference between the optical fiber 8 (B). That is, optical fibers 8 (A) accumulates the line length difference by meandering, tries to eliminate the line length difference between the optical fiber 8 (B). However, the optical fiber bundle such as wound on the drum, if the continuous bending is applied, only meandering can no longer solve the line length difference, the result of accumulation appeared once the line length difference, finally bundle member 10 together it may sometimes jump out from the enclosed gap.
　
[0047]
　Figure 9 is a diagram for explaining the optical fiber unit 2 of the second embodiment. As shown in FIG. 9, by shortening increases or the number of bundled material, the pitch of winding, it is possible to suppress the protrusion of the optical fiber 2. This partial bundle member 10 is not wound, that area becomes smaller exposed optical fiber, as a result jumping out of the optical fiber 2 is considered to thereby inhibited.
[0048]
　Figure 10A is a developed view of a bundle member 10 for illustrating the exposed area of ​​the optical fiber. Figure 10A is an outer circumferential surface of the optical fiber bundle 6 virtually the circumferential surface, the bundle material 10 wound around on the outer periphery of the optical fiber bundle 6 shows a state in which deployment. Bundles material 10, while the winding direction on the outer periphery of the optical fiber bundle 6 is inverted alternately, is wound along the longitudinal direction of the optical fiber bundle, the inverted portion of the winding direction, and another bundle member 10 joined It is. The exposed area in this example, an area of ​​a region surrounded by the bundle between as shown in the shaded portion of FIG. 10A.
[0049]
　10B is a developed view of another bundle member 10 for illustrating the exposed area of ​​the optical fiber. Figure 10B is disposed are four bundles material 10, not only the inverted position of the winding direction, are joined to as the bundle member 10 at the intersection intersecting the other bundles member 10. The exposed area in this example, the area of ​​a region surrounded by the bundle between as shown in the shaded portion of FIG. 10B.
[0050]
　
　jumping out of the optical fiber is caused when more than a certain there is exposed area. Therefore, a prototype optical fiber unit and a plurality created for exposed area was evaluated for popping characteristics of the optical fiber.
[0051]
　First, was prepared and the optical fiber bundle using 80 heart fraction of 8-fiber intermittent fixed ribbons, thickness of 0.08 mm, the bundle material width 1.4 mm. To bundle material with different number from two to eight, and create multiple prototype optical fiber unit having different exposed area by changing the winding pitch of the bundle material. Bending each of the trial optical fiber unit, jumping out of the optical fiber was evaluated whether generated. The evaluation results are shown in the following Table 2.
[0052]
[Table 2]

[0053]
　Table 2 shows what the respective evaluation result column is jumping out of the optical fiber did not occur by "○", those jumping out of the optical fiber has occurred "×". Result is "○" if, can be evaluated as a good optical fiber unit jumping out of the optical fiber does not occur even when the bent optical fiber unit.
[0054]
　From the results of Table 2, the exposed area S (square mm), the number of bundles member as N (present), is shown to be the following equation 1.
　[Number 1]
　　　　　　　　　　S ≦ 1200 / N (Equation 1)
[0055]
　Also, jumping out when using the 1-core optical fiber single fiber was also evaluated whether generated. The evaluation results are shown in Table 3 below.
[0056]
　Table 2 and from the results of Table 3, it is possible to determine the condition of the exposed area S of about one per optical fiber. The exposed area S (square mm), the number of bundles material N (present), optical fiber (including fiber ribbon) the number of cores per one as A, is shown to be the following equation 2.
　[Number 2]
　　　　　　　　　　S ≦ 150A / N (Equation 2)
[0057]
[table 3]

[0058]
　
　optical fiber cables, there is the water from entering the optical fiber cable by the application environment. The water entering along the the optical fiber cable to reach the junction box of the closure or the like, may affect the other optical fiber cable via the junction box. Therefore, the optical fiber cable excellent waterproof properties is required. Generally, such as by applying the water stopping material to a surface of the optical fiber unit 2 side of the holding tape 5 shown in Figure 1A, there is possible to enhance the waterproof performance of the optical fiber unit. At this time, the area of a region surrounded by the bundle material together, that is, when smaller than the certain value exposed area, sometimes water stopping material is not spread could not get bundled material in the optical fiber unit. As a result, the water stopping property is deteriorated.
[0059]
　Therefore, we evaluated waterproofing properties of the prototype optical fiber cable was evaluated above. Prototype fiber optic cable length is 40 m, performs a water injection in head length 1m from the optical fiber cable end face, was evaluated as a test time 240 hours. As water for evaluation, using artificial seawater dissolved water per liter of sodium chloride 24.5g and magnesium chloride hexahydrate 11.1 g. The evaluation results are shown in the following Table 4.
[0060]
[Table 4]

[0061]
　From the results of Table 4, the water stopping capability does not depend on the number of bundle material, by securing the exposed area 10 square mm or more was obtained a sufficient effect.
[0062]
　Table 2 or from the results of Table 4, it is possible to obtain the upper and lower limits of the exposed area S of about one per optical fiber. The exposed area S (square mm), the number of bundles material N (present), optical fiber (including fiber ribbon) the number of cores per one as A, is shown to be the following equation 3.
　[Number 3]
　　　　　　　　　　10 ≦ S ≦ 150A / N (Equation 3)
[0063]
　Other Embodiments
　embodiments described above are intended to facilitate the understanding of the present invention and are not to be construed as limiting the present invention. The present invention, without departing from the spirit thereof, may be changed or improved, the present invention is, of course, includes the equivalents thereof.
[0064]
　
　In the embodiment described above, the number of bundles member 10 wound around the optical fiber bundle 6 has been described four examples. However, the number of bundles member 10 provided in one optical fiber unit 2 is not limited to this. For example, there is 6 or more, may be or a odd number.
DESCRIPTION OF SYMBOLS
[0065]
1 optical fiber cable, 2 optical fiber unit, 3
envelope, 4A tension member, 4B ripcord, 5 holding
tape, 6 fiber optic bundle, 7 intermittently stationary optical fiber
tape, 8 optical fibers, 9A connecting portion, 9B unconsolidated
portion, 10 the bundle
material, 15 joints

WE CLAIM

Comprising an optical fiber bundle obtained by bundling a plurality of optical fibers, a plurality of bundles materials,
　one of the bundles member of the plurality of bundles material,
　　on the outer periphery of the optical fiber bundle, wrapped reverse direction alternately while, with are wound along the longitudinal direction of the optical fiber bundle,
　　the inverted portion of the winding direction, is joined with other bundles material,
　　the width to thickness in the cross section of the bundle material is less than 20 times it is
an optical fiber unit, characterized in that.
[Requested item 2]
　An optical fiber unit according to claim 1,
　the width to the thickness in the cross section of the bundle material is 18 times or less
the optical fiber unit, characterized in that.
[Requested item 3]
　An optical fiber unit according to claim 1 or 2,
　wherein the bundle material each other, are joined by an adhesive
optical fiber unit, characterized in that.
[Requested item 4]
　An optical fiber unit according to claim 1 or 2,
　the number of cores of the optical fiber A, the number of the bundle material is taken as N,
　the optical fiber centered on the outer periphery of the optical fiber bundle area line is exposed from the bundle material is not more than 150A / N square mm
optical fiber unit, characterized in that.
[Requested item 5]
　An optical fiber unit according to claim 4,
　the area of the optical fiber on the outer periphery of the optical fiber bundle is exposed from the bundle material is 10 square mm or more
optical fiber units, characterized in that.
[Requested item 6]
　A plurality of optical fiber unit, an optical fiber cable with jacket city that covers the plurality of the optical fiber unit,
　the optical fiber unit includes an optical fiber bundle obtained by bundling a plurality of optical fibers, a plurality comprising a bundle material,
　one of the bundles member of the plurality of bundles material,
　　on the outer periphery of the optical fiber bundle, while reversing the winding direction alternately wound along the longitudinal direction of the optical fiber bundle together and,
　　at the inverting portions of the winding direction, it is joined with other bundles material,
　　width in the cross-section to the thickness in the cross section of the bundle material is less than 20 times
the optical fiber cable, characterized in that.