The present invention relates to an optical cable and the jacket removing method.
BACKGROUND
[0002]
　Patent Document 1, an optical fiber cable for laying the micro duct (small diameter tubular duct) in feed air pressure is described. Patent Document 1, around the loose tube (plurality of storage tubes for optical fiber along with the water shut-off possible fillers), it is described that the three strength members are embedded in the jacket at 120 ° intervals there.
[0003]
　Patent Document 2 discloses a plurality of optical cable containing the optical fiber unit into the interior of the envelope wrapped with a holding tape optical fiber. Patent Document 2, so as to sandwich the container portion containing the optical fiber units, it is described that two strength members are embedded in the jacket.
CITATION
Patent Document
[0004]
Patent Document 1: JP 2010-204368 Patent Publication
Patent Document 2: JP 2015-169756 JP
Summary of the Invention
Problems that the Invention is to Solve
[0005]
　The optical fiber cable described in Patent Document 1, three strength members are arranged in twisted around the loose tube. Therefore, when taking out the optical fiber from an optical fiber cable, only the removal of the envelope, will have strength members are in the way, it is difficult to take out the optical fiber. As a result, in order to take out the optical fiber from the optical fiber cable described in Patent Document 1, and cut strength member it becomes necessary.
[0006]
　Meanwhile, strength member of Patent Document 1 has been arranged twisted into contact with loose tube, if the inner strength member is an optical fiber unit (a plurality of optical fibers of Patent Document 2, rather than loose tube when it is Tate添 in a state in which a member and contacted as wrapped aggregate) which in holding tape, when the optical cable is bent, tensile strength body will bite into the inside (optical fiber unit), this results, light damage to the fiber, which may lead to an increase in transmission loss.
[0007]
　The present invention aims at providing a easily removed novel optical cable optical fiber.
Means for Solving the Problems
[0008]
　The main invention for achieving the above object, a plurality of the optical fiber unit wrapped with the holding tape optical fiber, at least three of the strength members which are disposed outside the circumferential direction at intervals of the optical fiber unit If, when the outer covering of the optical fiber unit and the strength member, wherein the strength member, said optical fiber units and are arranged in parallel, between the strength members and the optical fiber unit the jacket is formed, the envelope of the inner wall surface formed between the optical fiber unit and the strength member, than the envelope of the inner wall disposed non the strength member, the cable projects toward the center, of the holding tape, the portion that is disposed on the inner wall surface that protrudes toward the cable center, toward the cable center A cable, characterized in that has Nde.
[0009]
　Other features of the invention will become clear by reading the description of the specification and drawings described below.
Effect of the invention
[0010]
　According to the present invention, it is easy to take out the optical fiber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
[1] Figure 1 is a cross-sectional view of the optical cable 100 of the present embodiment.
[2] Figure 2A is an illustration of a bundle unit 11. Figure 2B is an explanatory view of an optical fiber ribbon 1 of the intermittent-linked.
FIG. 3 is an explanatory view of a recessed rate holding tape 14.
[4] FIGS. 4A and 4B are explanatory views of the envelope elimination method of the optical cable 100 of the present embodiment.
[5] FIGS. 5A and 5B are a partially enlarged view of a cross section of the optical cable 100.
FIG. 6 is a graph of measurement results of the flexural rigidity of the optical cable.
[7] FIG. 7 is a graph of measurement results of the air pressure-feeding performance.
[8] FIG. 8 is a graph of measurement results of the flexural rigidity of the optical cable of the third embodiment.
[9] FIG. 9 is a graph of measurement results of the air pressure-feeding performance of the third embodiment.
DESCRIPTION OF THE INVENTION
[0012]
　From the description of the specification and the drawings described below, at least the following matters will be made clear.
[0013]
　An optical fiber unit wrapped by a holding tape plurality of optical fibers, and at least three strength members is disposed outside circumferentially at intervals of the optical fiber unit, the optical fiber unit and the strength members When the outer covering, wherein the strength member, said optical fiber units and are arranged in parallel, being the envelope is formed between the optical fiber unit and the strength members, the optical the envelope of the inner wall surface is formed between the the fiber unit strength member, the than the arrangement that is not the envelope of the inner wall surface of the strength member protrudes toward the cable center, the pressing winding of tape, portions disposed in said inner wall surface that protrudes toward the cable center, optical cable, characterized in that recessed toward the cable center The Laka. According to such an optical cable, it is easy to take out the optical fiber.
[0014]
　Number of the strength members of the optical cable is preferably a three. Thus, the strength members of the small number as possible, it is possible to obtain an optical cable with isotropic bending direction.
[0015]
　The inner diameter of the portion recessed the holding tape and r, the inner diameter of the sites not recessed of the holding tape and R, when dent rate H (%) was the H = (R-r) / R × 100 , depressions ratio H (%) is desirably 20% or less. Thus, the increase in transmission loss of the optical fiber can be suppressed.
[0016]
　Outer tangents of the two adjacent of said strength members is desirably positioned outside the said optical fiber unit. This can suppress damage to the optical fiber unit.
[0017]
　Some of the optical fiber unit is preferably located outside the outer tangent of the two said strength members adjacent. Thus, it is easy to take out the optical fiber.
[0018]
(1) a plurality of the optical fiber unit wrapped by a holding tape optical fiber, at least three strength members disposed at intervals in the circumferential direction on the outside of the optical fiber unit, the optical fiber unit and the When the outer covering the tension member, wherein the strength members is, the optical fiber unit and providing a cable that is arranged parallel to, and (2) longitudinal edge line of the blade of the tool the optical cable the blade of the tool so as to intersect against the jacket of the optical cable with respect to, the tool is moved along the longitudinal direction, clear jacket removing method of performing the removal of the envelope to become. According to such a jacket removing method, it is easy to take out the optical fiber.
[0019]
　Wherein while the cutting tool is guided by the tension member, to move along the tool in the longitudinal direction is desirable. This facilitates the operator by envelope removal.
[0020]
　When removing the jacket, it is desirable to contact with the tension member of two of the blades of the tool adjacent. This can suppress that the blade of the tool penetrates deeply more than that.
[0021]
　When removing the envelope by the tool, it is desirable that the holding tape is deformed so as to be recessed inwardly by the blade moving in the longitudinal direction. Thus, it is easy to take out the optical fiber.
[0022]
　=== embodiment ===
　
　FIG. 1 is a cross-sectional view of the optical cable 100 of the present embodiment. Optical cable 100 of the present embodiment has an optical fiber unit 10, and at least three strength members 20, and a jacket 30.
[0023]
　Optical fiber unit 10 is wrapped a plurality of optical fibers 3 in holding tape 14 units (aggregates). Optical fiber unit 10, the "core of the optical cable", "optical fiber core", "core unit", sometimes also called just as "unit". In the present embodiment, the optical fiber unit 10 includes a plurality of bundles unit 11 (see FIG. 2A) formed by bundling a plurality of optical fiber ribbon 1 in bundle member 12, a plurality of bundles units 11 are wrapped in holding tape 14 It is constituted by. Incidentally, the plurality of bundles of optical fibers 3 which are enveloped in holding tape 14 is not limited to those composed of a plurality of bundles units 11, for example it is constituted by bundling optical fibers 3 of the number of single fibers good.
[0024]
　Figure 2A is an illustration of a bundle unit 11. Bundle unit 11 has a structure in which a bundle of bundle of a plurality of optical fibers 3 in the bundle material 12. Bundle unit 11 may also be referred to as "sub-unit". Bundles member 12 are a plurality of binding can filamentous optical fiber 3, cord-like or tape-like member. The identification color of the bundle material 12 can be identified with other bundles unit 11. However, it is also possible to form the identification mark in the bundle material 12. Bundle unit in FIG. 11, although the two bundles member 12 has a plurality of bundled optical fibers 3 wrapped around the SZ form, bundling a plurality of optical fibers 3 by winding a single bundle member 12 of helically and it may be. Bundle of optical fibers 3 is constituted by bundling optical fiber ribbon 1 of the plurality of intermittent linked.
[0025]
　Figure 2B is an explanatory view of an optical fiber ribbon 1 of the intermittent-linked. Right view in FIG. 2B is a cross-sectional view taken along A-A or B-B in perspective view a left. In the following description, as shown in FIG. 2B, a direction parallel to the optical fiber 3 that constitutes the optical fiber tape 1 is "longitudinal". Further, the direction of arrangement of the plurality of optical fibers 3 included in the optical fiber ribbon 1 to the "width direction".
[0026]
　Intermittent coupling type optical fiber tape 1 is an optical fiber ribbon 1 that is intermittently connected by parallel a plurality of optical fibers 3. Optical fiber 3 of the adjacent two hearts are connected by a connecting portion 5. A plurality of connecting portions 5 for connecting the optical fiber 3 of the adjacent two hearts are intermittently arranged longitudinally. Further, a plurality of connecting portions 5 of the optical fiber ribbon 1, are two-dimensionally intermittently arranged in the longitudinal direction and the width direction. Connecting part 5, by solidifying by irradiating ultraviolet rays after coating an ultraviolet curable resin as a coupling agent is formed. It is also possible to configure the connecting section 5 of a thermoplastic resin. Region other than the connection portion 5 between two adjacent core optical fiber is in a non-coupling part 7 (separation unit). The unbound portion 7, the optical fiber 3 of adjacent 2 mind not restrained. Thereby, or a rounded optical fiber ribbon 1 tubular (bundles), it is possible to collapse, comprising a number of optical fibers 3 can be accommodated at high density. When the single-core separating optical fiber 3 from the optical fiber ribbon 1, the operator, by such tearing between the optical fiber 3, will destroy the connection portion 5.
[0027]
　The optical fiber ribbon 1 of the intermittent connection type, not limited to those shown in Figure 2B. For example, it is also possible to change the mind of the optical fiber tape 1. It is also possible to change the arrangement of the connecting portion 5 which is arranged intermittently.
[0028]
　Holding tape 14 is a member surrounding the plurality of optical fibers 3. Prevented by wrapping the optical fiber 3 by holding tape 14, when coated with molten resin forming the outer cover 30, the optical fiber 3 in the interior of the envelope 30 would be embedded (that would dig) it can. The holding tape 14, polyimide tape, polyester tape, polypropylene tape, polyethylene tape or the like is used. In addition, it is possible to utilize the nonwoven as holding tape 14. In this case, non-woven fabric, polyimide, polyester, polypropylene, polyethylene or the like that is formed into a tape is used. Holding tape 14 may be one formed by bonding a film such as a polyester film to the nonwoven fabric.
[0029]
　Holding tape 14 has a configuration obtained by adhering a water powder to the tape-like base material (or coating). Therefore, holding tape 14 functions as a water absorption tape. Water powder, water-absorbing granular or powder substances (water absorbing material). Water powder may be adhered to the surface of the base material tape (coating), it may be arranged in between the base material tape made up of two non-woven fabrics. The absorption of water (when water powder has absorbed water), water absorption powder granular or powdery expands, becomes jelly (swelling). Such water-absorbing powder, for example, particle size 5 ~ 30 [mu] m of starch-based, cellulose-based, polyacrylic, polyvinyl alcohol, polyoxyethylene-based superabsorbent material, or be a mixture thereof it can. By water absorption powder became jelly blocks the internal clearance of the optical cable 100, the optical cable 100 can stop water. Incidentally, the base material itself may have a water absorption. Also, holding tape 14 may not have a water absorption.
[0030]
　Strength member 20 is Aragai the shrinkage of the jacket 30 is a member for suppressing the distortion and bending is applied to the optical fiber unit 10 by contraction of the envelope 30 (especially optical fibers 3). Strength member 20 is a linear member, is embedded in the jacket 30. As the material of the strength member 20, non-metallic materials or metallic materials can be used. The non-metallic materials such as glass FRP (GFRP), Kevlar aramid fiber-reinforced plastic reinforced by (R) (KFRP), a fiber-reinforced plastic, such as polyethylene fiber-reinforced plastic reinforced by polyethylene fibers (FRP) can be used is there. The metallic material, metal wire such as steel wire can be used.
[0031]
　Optical cable 100 of the present embodiment has at least three tension members 20. Here, three strength members 20 is buried in the interior of the envelope 30. Three strength member 20 (here the interval of 120 °) equal intervals in the circumferential direction are spaced. Thus, by at least three strength members 20 are arranged at intervals in the circumferential direction, the optical cable 100 can obtain an isotropic bending direction. If the number of strength members 20 is three, the minimum number of strength members 20, it is possible to obtain an optical cable 100 having an isotropic bending direction. However, the number of strength members 20 is not limited to three, it may be four or more. Incidentally, the optical cable 100 when having the N number of strength members 20, strength members 20 of the N book will be placed at intervals of 360 ° / N in the circumferential direction. For example, if the optical cable 100 has four strength members 20, four strength members 20 will be positioned at 90 ° intervals in the circumferential direction. Also, inside the region surrounded by at least three strength members 20, accommodating portion of the optical fiber unit 10 is formed.
[0032]
　Meanwhile, if the if the two strength members 20 are arranged so as to sandwich the optical fiber unit 10, the optical cable 100, the line connecting a specific direction (the two strength members 20 bend the neutral axis easy to bend in the direction), it becomes difficult to bend in a direction other than that. Thus bending direction of the cable is limited, air pressure-feeding property of the micro duct is reduced. In contrast, in the case of the optical cable 100 of the present embodiment, it is possible to obtain an isotropic bending direction, it is possible to achieve good air feeding characteristics of the micro-duct.
[0033]
　Jacket 30 is a member for covering the optical fiber unit 10 and the strength member 20. Envelope 30 of outer (cross-section) is circular. As the material of the envelope 30, such as polyvinyl chloride (PVC), polyethylene (PE), nylon (registered trademark), a resin such as fluorinated ethylene or polypropylene (PP) can be used, if polyethylene (PE) the high-density polyethylene, medium density polyethylene, low density polyethylene, or the like linear low density polyethylene can be used. Further, as the material of the jacket 30, for example, magnesium hydroxide, polyolefins compound containing metal hydrate such as aluminum hydroxide as a flame retardant can be used. Incidentally, in the envelope 30, another member may be embedded in the optical fiber unit 10 and the strength member 20.
[0034]
　When forming the envelope 30 the molten resin extruded with, distortion optical fiber unit 10 (especially the optical fiber 3) by the contraction of the jacket 30 during cooling, as a result, the signal loss of the optical fiber 3 is increased risk there is. However, by embedding a tension member 20 in the jacket 30, the load at the time of contraction of the jacket 30 because according to the tension member 20, the optical fiber unit 10 hardly load is applied.
[0035]
　In this embodiment, strength member 20 is disposed parallel to the optical fiber unit 10. If when the strength members 20 are twisted outside the optical fiber unit 10, the outer strength member 20 of the optical fiber unit 10 from the optical fiber unit 10 when taking out the optical fiber 3 becomes a hindrance, strength member 20 since the need to cut the resulting workability is lowered. In contrast, in the present embodiment, the tension member 20 since only disposed in parallel with the optical fiber unit 10 can be taken out easily the optical fiber 3 by simply removing the envelope 30. Note that the extraction method of the optical fiber 3 in the present embodiment (jacket removing method of the optical cable 100) will be described later.
[0036]
　In the case where the strength members 20 is arranged parallel to the optical fiber unit 10 as in this embodiment, if without forming the envelope 30 between the optical fiber unit 10 and the tension member 20, the optical fiber unit 10 when the tension member 20 resulting in the structure in contact, because there is no serving as a partition between the optical fiber unit 10 and the tension member 20, when the optical cable 100 is bent, a tension member 20 to the optical fiber unit 10 bite at will. As a result, or the optical fiber 3 is damaged, the signal loss of the optical fiber 3 is likely to be or to increase. Incidentally, if if the tension member 20 is twisted, even without forming the envelope 30 between the optical fiber unit 10 and the tension member 20, when the optical cable 100 is bent, tension member 20 is light need not bite into the fiber unit 10. However, in this case, as already described, when taking out the optical fiber 3, it is not necessary to cut the tension member 20 occurs, the workability is lowered.
[0037]
　Therefore, in this embodiment, while adopting a configuration in which strength members 20 disposed in parallel with the optical fiber unit 10, envelope between the optical fiber unit 10 (details holding tape 14) and the strength members 20 30 It employs a configuration but formed. In other words, in this embodiment, strength members 20 are not in contact with the optical fiber unit 10, disposed in parallel with the optical fiber unit 10. By envelope 30 is formed between the holding tape 14 and strength members 20 of the optical fiber unit 10, the envelope 30 is a partition wall separating the optical fiber unit 10 and the strength member 20, the optical cable 100 is curved It is possible to prevent the strength members 20 bites into the optical fiber unit 10.
[0038]
　In the configuration jacket 30 is formed between the optical fiber unit 10 and the strength member 20, to become a structure envelope 30 is formed inside the strength member 20, the housing space of the optical fiber unit 10 is narrow turn into. Meanwhile, in order to widen the accommodation space of the optical fiber unit 10, when the envelope 30 is formed between the optical fiber unit 10 and the tension members 20 resulting in thin, the optical fiber unit 10 and the strength member 20 functions as a partition wall separating may be decreased. Further, in order to widen the accommodation space of the optical fiber unit 10, the result in thin envelope 30 formed between the optical fiber unit 10 and the tension member 20, tension member that anticaries contraction of the jacket 30 All it also no longer fulfill the original function of the 20.
[0039]
　In contrast, in the present embodiment, the inner wall surface of the envelope 30 formed between the optical fiber unit 10 and the tension member 20, than the inner wall surface of the envelope 30 that is not disposed strength member 20, the cable and it is configured so as to protrude toward the center. Accordingly, it is possible to secure the jacket 30 thickness of around the strength member 20 (including the inside of the strength member 20), and functions as a partition wall that separates the optical fiber unit 10 and the tension member 20, the envelope 30 of the it is possible to fulfill the original function of the strength member 20 that anticaries to contraction. Further, in the present embodiment, among the holding tape 14, parts which are arranged on the inner wall surface of the envelope 30 which projects towards the cable center is configured as a depression towards the cable center. Thus, holding tape 14, since the portion does not protrude outside the 30 not recessed, it is possible to secure the size of the housing space of the optical fiber unit 10. That is, according to the optical cable 100 of the present embodiment, the securing of the thickness of the jacket 30 surrounding the strength member 20 (including the inside of the strength member 20), of ensuring size of the accommodation space of the optical fiber unit 10 , it is possible to achieve both the resolution of conflicting problems.
[0040]
　Figure 3 is an illustration of a dent rate holding tape 14. In the figure, there is shown the shape of the holding tape 14 in the cross section of the optical cable 100. r in the drawing indicates the inner diameter of the holding tape 14 on the inside of the strength member 20. In other words, r in the drawing indicates the inner diameter of a portion recessed holding tape 14. In addition, R in the drawing indicates the inner diameter of the holding tape 14 at a site other than the inner strength member 20. In other words, R in the shows the inner diameter of sites not recessed with holding tape 14.
[0041]
　We define indentations ratio H (%) of the following equation.
　H = (R-r) / R × 100
[0042]
　In the optical cable 100 of the present embodiment, as the dent ratio H is large, the (inner space of the envelope 30, the space occupied by the optical fiber unit 10) housing space to the cross-sectional area of ​​the optical cable 100 is the area of ​​the spread, the outer of the optical cable 100 it is possible to reduce the diameter. On the other hand, when the dent rate H is too large, becomes the optical fiber 3 susceptible to lateral pressure when bending an optical cable 100, because the transmission loss is easily increased, dent rate H (%) is 20% or less it is desirable that the (later).
[0043]
　
　FIGS. 4A and 4B are explanatory views of the envelope elimination method of the optical cable 100 of the present embodiment. In FIG. 4B (illustration is viewed from the side of the removal operation of the envelope 30), for convenience of explanation, the tool 50 (yarn end finding tool, jacket removal tool) only blade 51 of the is shown.
[0044]
　In the present embodiment, when the jacket removal of the optical cable 100, the operator, the edge line of the blade 51 of the tool 50 (flat blade) is a blade 51 of the tool 50 so as to intersect the longitudinal direction of the optical cable 100 against the envelope 30, it is moved along the edge 51 of the tool 50 in the longitudinal direction, to remove the jacket 30. In other words, the operator, as cut by the planer and peeler, removing the envelope 30 in the blade 51 of the tool 50 (flat blade). Here, the direction of moving the tool 50 (the longitudinal direction) is a direction perpendicular to the edge line of the blade 51 (flat blade).
[0045]
　In the present embodiment, since the strength members 20 disposed on the outside circumferential direction at intervals of the optical fiber unit 10 is disposed in parallel with the optical fiber unit 10, the operator, the envelope along the longitudinal direction by removing the 30, it can be accessed from the gap between the tension member 20 to the optical fiber unit 10. Note that if when the strength members 20 are twisted outside the optical fiber unit 10, only the removal of the jacket 30 along the longitudinal direction, the outer strength member 20 of the optical fiber unit 10 is in the way Therefore, to access from the gap between the tension member 20 to the optical fiber unit 10 becomes difficult (this result, such as cutting strength member 20 becomes necessary.)
[0046]
　In addition, in the present embodiment, since the strength members 20 are arranged parallel to the optical fiber unit 10, the operator, when moving along the blade 51 of the tool 50 in the longitudinal direction, the blade in tension member 20 51 can be guided. That is, the tension member 20 functions as a guide for the tool 50. Further, the blade 51 of the tool 50, by contacting the tension member 20, it is prevented from entering deeply into the optical cable 100 any more. Therefore, the tension member 20 has a function to suppress damage to the optical fiber unit 10.
[0047]
　Figure 5A is a partially enlarged view of a cross section of the optical cable 100. In the drawing, the outer tangential two strength members 20 adjacent is indicated by a dotted line.
　Blade 51 of the tool 50, by contacting the two strength members 20, it is prevented from entering deeply into the optical cable 100 any more. Thus, two outer tangential strength members 20 (dotted line in the figure) will indicate the limits depth of the edge line of the tool 50.
[0048]
　In the present embodiment, as shown in FIG. 5A, 2 pieces of the outer tangential strength members 20 (dotted line in the figure) is an optical fiber unit 10 (details holding tape 14) has outside the. Accordingly, it is possible to prevent the blade 51 of the tool 50 is in contact with the optical fiber unit 10 (especially the optical fiber 3), can suppress damage to the optical fiber unit 10. However, the operator, in order to take out the optical fiber 3 from the optical cable 100, after removal of the jacket 30 in the blade 51 of the tool 50, tore thin-walled envelope 30 remaining outside of the optical fiber unit 10 it is necessary to access the optical fiber unit 10.
[0049]
　On the other hand, as shown in FIG. 5B, 2 pieces of the outer tangential strength members 20 may be to become inside the envelope 30. In other words, a part of the optical fiber unit 10 may protrude outward from the outer tangents of the two strength members 20. If the structure shown in FIG. 5B, when the operator has removed the jacket 30 in the blade 51 of the tool 50, since the optical fiber unit 10 is exposed, there is an advantage that it becomes easy access to the optical fiber unit 10. However, if the structure shown in FIG. 5B, it may occur that the blade 51 of the tool 50 is in contact with the optical fiber unit 10, holding tape 14 of the optical fiber unit 10 is recessed inwardly by a blade 51 which moves in the longitudinal direction deformed so as, this way, damage to the optical fiber unit 10 (especially the optical fiber 3) can be suppressed. In particular, in the present embodiment, among the holding tape 14, parts which are arranged on the inner wall surface of the envelope 30 which projects towards the cable center, since it is configured such depression towards the cable center, the tool 50 when the blade 51 of the contacts the holding tape 14, since the contact portion is likely to dent inwardly, holding tape 14 is not easily damaged. Therefore, as shown in FIG. 5B, 2 pieces of the outer tangential strength members 20, it is also allowed to be inside than the jacket 30.
[0050]
　
　As a first example was prepared an optical cable 100 shown in FIG. The optical cable 100 of the first embodiment, are arranged in parallel to the three strength members 20 disposed at 120 ° intervals with the optical fiber unit 10 without contacting the optical fiber unit 10. Optical cable 100 of the first embodiment is composed of 72 hearts (The optical fiber unit 10 of the optical cable 100 of the first embodiment, are housed 72 optical fibers 3).
　Further, as the first and second comparative examples, it was prepared optical cable described in Patent Document 1 (JP 2010-204368). The optical cable of the first and second comparative examples, the three strength members 20 disposed at 120 ° intervals, they are arranged in a state of being twisted to the outside of the loose tube. Optical cable of the first comparative example is composed of mind, the number of optical cable is composed of 72 hearts (optical fiber housed in the loose tube of the second comparative example is 12 in the first comparative example, the second comparative in the example is 72 lines).
[0051]
　Figure 6 is a graph of measurement results of the flexural rigidity of the optical cable. To examine the our of bending stiffness of the cable, by changing the bending direction at 30 ° increments, optical cable bending stiffness in each of the bending direction (unit: N / m @ 2) was measured. As shown in the figure, the optical cable of the first embodiment, it was confirmed that substantially isotropic bending stiffness is obtained. (Note that the flexural rigidity of the optical cable 100 of the first embodiment is 4-5 times that of the first comparative example was 1.5 to 2 times the second comparative example.)
[0052]
　Figure 7 is a graph of measurement results of the air pressure-feeding performance. For the determination of the air pressure-feeding performance, providing a micro-duct having an inner diameter of 8 mm, laid the microduct with the 8-shaped one rotation about 125m, each optical cable to send the air pressure within microducts, to measure the distance . Transmission distance of the optical cable of the first embodiment is 3000 m, it can be obtained a good pumping characteristics (was transmission distance 2500m optical cable comparative example) was confirmed.
[0053]
　
　was a second embodiment, to produce a dent rate plurality of types of optical cables 100 having different H a (%) (see Figure 1). Is composed of any of the optical cable 100 is also 72 heart (The optical fiber unit 10 of the optical cable 100, 72 optical fibers 3 are accommodated).
[0054]
　To confirm the diameter effect dent rate H (%), it was measured outer diameter of the optical cable 100. The dent rate H (%) is with respect to the outer diameter of the 0% optical cable (optical cable without indentations), and the outer diameter of the optical cable 100 to the outer diameter of the optical cable as a reference to evaluate the thin effect.
[0055]
　In addition, to measure the air pressure-feeding performance of each optical cable 100. Method of measuring the air pressure-feeding performance is as previously described. Equivalent to the above-described comparative example, or if there is a comparative example above pumping characteristics were evaluated as good (○).
[0056]
　It was also measured transmission characteristics of each optical cable 100. Respect 600m cable 100 wound around the drum, and a measurement wavelength 1.55 .mu.m, the transmission loss of the optical fiber 3 in the environment of temperature 20 ° C. The (dB / km) measured, a large optical fiber of most transmission loss transmission loss of 3 is evaluated as valid if it is less than 0.2dB / km (○), was evaluated as bad if 0.3 dB / miles or more (×).
[0057]
　In addition, to evaluate the lead-out of each optical cable 100. As shown in FIGS. 4A and 4B, based on whether scratch the optical fiber 3 when the removal of the envelope of the optical cable 100 (yarn end finding) using a tool to evaluate the yarn end finding properties.
[0058]
　Dent rate different diameter effect of each optical cable 100, pumping characteristics, the transmission characteristics and the lead-out of the evaluation results are shown in the following table.
[0059]
[Table 1]

[0060]
　More As shown the outer diameter of Table 1 (mm) in diameter effect (%), dent rate H (%) is large, it was confirmed that it is possible to narrow the outer diameter of the optical cable 100.
[0061]
　Further, as shown in pumping characteristics of the table 1, the optical cable 100 according to the embodiment, it was confirmed that Comparative Example least equivalent pumping characteristics described above are obtained. In particular, if the dent rate H is 7.5% or more, pumping characteristics described above comparative examples that were obtained. This is because as the dent ratio H (%) is large, can be thinner the outer diameter of the optical cable 100 is considered to be because became an optical cable 100 easily feed air pressure within a narrow microducts.
[0062]
　On the other hand, as shown in the transmission characteristics of Table 1, dent rate H (%) is the equal to or greater than 25% was evaluated transmission characteristics as bad. Why the transmission characteristics are deteriorated, it is considered to be because the lateral pressure is applied to the optical fiber 3 when the bending an optical cable 100. Thus, dent rate H (%), it was confirmed 20% or less.
[0063]
　Further, as shown in the lead-out of the evaluation results of Table 1, in any of the optical cable 100, damage to the optical fiber 3 was not confirmed. Therefore, with respect to the optical cable 100 of the structure shown in FIG. 1, it was confirmed that the coat removing method shown in FIG. 4A is valid.
[0064]
　
　As a third example, 4 (when the number of strength members and the N, spacing 360 ° / N in the circumferential direction) - six strength members are circumferentially evenly spaced apart arrangement to produce an optical cable that is. Incidentally, the optical cable of the structure of the third embodiment is different from the optical cable arrangement of the first embodiment, except the number N of the strength members is substantially the same. Therefore, also in the third embodiment, strength members are disposed in parallel to the optical fiber unit, between the optical fiber unit and the strength members and the jacket is formed, the optical fiber unit and the strength members outside the formed jacket of the inner wall surface between, than the jacket of the inner wall is not disposed strength member protrudes toward the cable center, among the holding tape, which protrudes toward the cable center was site located the inner wall surface is configured as to be recessed toward the cable center. However, when the number N of the strength member, although the optical cable of N = 3, 4 is composed of 72 hearts, optical cable N = 5, 6 is composed of 288 heart.
[0065]
　Figure 8 is a graph of measurement results of the flexural rigidity of the optical cable of the third embodiment (and the first embodiment). To examine the our of bending stiffness of the cable, by changing the bending direction at 30 ° increments, optical cable bending stiffness in each of the bending direction (unit: N / m @ 2) was measured. As shown in the figure, also in the optical cable of the third embodiment (N = 4 ~ 6), equivalent to the optical cable of the first embodiment (N = 3), be substantially isotropic bending stiffness is obtained confirmed.
[0066]
　Figure 9 is a graph of measurement results of the air pressure-feeding performance of the third embodiment (and the first embodiment). As shown in the measurement result, in the optical cable of the third embodiment (N = 4, 6), equivalent to the optical cable of the first embodiment (N = 3), can be obtained a good pumping properties confirmed It was.
[0067]
　=== Other ===
　The embodiments described above are intended to facilitate 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.
DESCRIPTION OF SYMBOLS
[0068]
1 optical fiber ribbon, 3 optical
fibers, 5 connecting section, 7 unconsolidated
portion, 10 an optical fiber
unit, 11 bundle units, 12 bundles
member, 14 holding tape, 20 a tension member, 30
jacket, 50 tools, 51 blade,
100 optical cable

WE claims

[Requested item 1]
　An optical fiber unit wrapped by a holding tape plurality of optical fibers,
　and at least three strength members is disposed outside circumferentially at intervals of the optical fiber unit,
　the optical fiber unit and the strength members When the outer covering,
comprising a
　said strength member, said optical fiber units and are arranged in parallel,
　being the envelope is formed between the optical fiber unit and the strength members,
　the optical the envelope of the inner wall surface is formed between the the fiber unit strength member, the than the arrangement that is not the envelope of the inner wall surface of the strength member protrudes toward the cable center,
　the pressing winding of tape portion that is disposed on the inner wall surface that protrudes toward the cable center is recessed toward the cable center
cable, characterized in that.
[Requested item 2]
　A cable according to claim 1,
　the number of the strength members of the optical cable, optical cable, which is a three.
[Requested item 3]
　A cable according to claim 1 or 2,
　the inner diameter of a portion recessed the holding tape and r,
　the inner diameter of the sites not recessed of the holding tape and R,
　dent rate H of (%) H = when the (R-r) / R × 100,
　dent rate H (%) is an optical cable, characterized in that 20% or less.
[Requested item 4]
　A cable according to any one of claims 1 to 3,
　the optical cable outer tangents of the two said strength members adjacent, characterized in that located outside the said optical fiber unit.
[Requested item 5]
　A cable according to any one of claims 1 to 3,
　the optical cable part of the optical fiber unit, characterized in that located outside the outer tangent of the two said strength members adjacent.
[Requested item 6]
(1) a plurality of the optical fiber unit wrapped by a holding tape optical fiber, at least three strength members disposed at intervals in the circumferential direction on the outside of the optical fiber unit, the optical fiber unit and the When the outer covering the tension member, includes a,
　the strength members is, the optical fiber unit and providing a cable that is arranged parallel to, and
(2) longitudinal edge line of the blade of the tool the optical cable wherein the blade of the tool against the casing of the optical cable, the tool is moved along the longitudinal direction, removing the sheath so as to intersect the
envelope removal process of performing.
[Requested item 7]
　A jacket removal according to claim 6,
　while the blade of the tool is guided by the tension member, the jacket removal method characterized by moving along the tool in the longitudinal direction.
[Requested item 8]
　A jacket removing method according to claim 7,
　when removing the jacket, the jacket removal method characterized by contact with the tension member 2 of which the blade adjacent the tool.
[Requested item 9]
　A jacket removal method according to any one of claims 6-8,
　when removing the envelope by the tool, deformed to the holding tape is recessed inwardly by the blade moving in the longitudinal direction jacket removing method characterized by.