Fiber optic cable

Abstract

Fiber optic cable (1) which has: a coat (10); a number of tensile strength elements (30) embedded in the sheath (10); a core (20) which is housed in the sheath (10) and has an intermittently bonded fiber optic tape (21) which has: optical fibers (21a); ​​and Adhesive sections (21c) that intermittently bond the optical fibers (21a) together in a longitudinal direction; and a sheathing tube (22) that encloses the intermittently bonded fiber optic tape (21), wherein the sheathing tube (22) has: a sheath section (22a) wherein a first end section of the sheath tube (22) overlaps with a second end section of the sheath tube (22); and a non-envelope section (22b) positioned between the first end section and the second end section, characterized by the fact that: the fiber optic cable (1) has a compressive strength of 12.8 N / mm² 2 or more and 32.4 N / mm 2 or less.

Description

[Technical field]

[0001] The present invention relates to a fiber optic cable. [Technical background]

[0002] A fiber optic cable, as described in patent document 1, is known from the prior art. This fiber optic cable comprises a sheath and a number of optical fibers housed within the sheath. The outer circumferential surface of the sheath is provided with recesses and projections arranged alternately in the circumferential direction. According to patent document 1, the optical fibers are housed in a twisted state within a tube. Alternatively, the optical fibers are coated together with a UV-curable resin to form a ribbon core wire.

[0003] Patent document 2 discloses a fiber optic cable 1 with a cable core containing coated optical fibers, which is enclosed by a sheath. At least two tension elements are arranged around the cable core and are completely enclosed by the sheath. The fiber optic cable has an air gap in the sheath on a common tangent of two of the tension elements on an outer circumferential side of the two adjacent tension elements. This air gap is connected to an interior space in which the cable core is located. Patent document 3 discloses an optical unit containing a number of optical fibers formed by arranging the optical fibers in two lines and several rows (in this case, two lines and two rows) and by intermittently bonding the optical fibers together in a longitudinal direction. A connecting element is then formed by securing the optical fibers in a stack.It is desirable that the connecting part has a fixed length in the longitudinal direction.

[0004] Patent document 4 discloses a mono-coated optical fiber having a bending loss characteristic in which the optical loss increase at a bending radius of 13 mm is 0.2 dB / 10 revolutions or less, a fiber optic tape containing two-dimensionally arranged resin sections for connecting the adjacent 2-fiber mono-coated optical fibers at several points, the resin sections being arranged separately from each other in the longitudinal direction of the fiber optic tape, and a fiber optic cable containing a cable core section that stores the twisting of several units in which the mono-coated optical fibers forming the fiber optic tape are collected. [List of citations][Patent literature] [Patent Document 1] US Patent No. 6963686 [Patent Document 2] JP2016080747A [Patent Document 3] JP2013109172A [Patent Document 4] US2011 / 110635A1 [Summary of the invention][Technical problem]

[0005] In the fiber optic cable according to patent document 1, the recess is a V-shaped groove. Therefore, if, for example, a circumferential force is applied to the projection, the stress is concentrated on the inner end section of the groove, and the sheath tends to tear.

[0006] Furthermore, it has been found that the configuration in which a number of optical fibers are simply twisted and housed in the conduit impairs the stiffness of the fiber optic cable and is disadvantageous in terms of its suitability for air blowing. On the other hand, in a configuration where several optical fibers are coated together with a resin, the stiffness of the fiber optic cable can be achieved. However, when the optical fibers are coated together with resin, the core becomes large, which is disadvantageous with regard to reducing the cable diameter, and the stress exerted on the optical fibers also becomes high, which is detrimental with regard to transmission loss.

[0007] The present invention was made in view of such circumstances, and one objective of the present invention is to provide a fiber optic cable which is advantageous in terms of the properties for air blowing, diameter reduction and transmission loss, while increasing the strength of the sheath. [Solution to the problem]

[0008] To solve the above problems, a fiber optic cable with the features of the independent claims is provided. Further advantageous embodiments of the invention are defined in the dependent claims. [Advantageous effects of the invention]

[0009] According to the above aspect of the present invention, it is possible to provide a fiber optic cable that is advantageous in terms of the properties for air blowing, diameter reduction and transmission loss, while increasing the strength of the sheath. [Brief description of the drawings] Fig. 1A is an example of a cross-section through a fiber optic cable. Fig. IB is an enlarged view of part I of Fig. 1 A. Fig. Figure 2 is a schematic representation of an intermittently bonded fiber optic tape. Fig. Figure 3 is a schematic representation of a method for blowing in air. Fig. Figure 4 is a schematic representation of a path used for an experiment in blowing air into a path. Fig. Figure 5 is a cross-sectional view of a deformed fiber optic cable. Fig. Figure 6 is an illustrative view of a cross-sectional area of ​​a depression. Fig. 7A is a diagram illustrating a case in which a projection and a tensile strength element extend linearly. Fig.7B is a diagram showing a case where the projection and the tensile strength element are spirally twisted. Fig. Figure 8 is a diagram showing the effect of the spiral twisting of the projection and the tensile strength element on the bending stiffness of the fiber optic cable. Fig. Figure 9 is a diagram showing a measurement angle X that is the horizontal axis of Fig. 8 is. Fig. Figure 10 is a cross-sectional view of a fiber optic cable in which a number of tensile strength elements are arranged within a projection. Fig. Figure 11 is a diagram showing the effect of the SZ-shaped twisting of the projection and the tensile strength element on the bending stiffness of the fiber optic cable. Fig. Figure 12A is a cross-sectional view of a fiber optic cable in which a low-friction material is arranged on the top of a projection. Fig. Figure 12B is a cross-sectional view of a fiber optic cable in which a layer of low-friction material is arranged over the entire surface of the jacket. Fig. 12C is a cross-sectional view of a fiber optic cable with a protrusion made of a low-friction material. Fig. Figure 13A is a cross-sectional view of a fiber optic cable in which a tear strip is located in one part of the projection and a tensile strength element is located in the other projection. Fig. Figure 13B is a cross-sectional view of a fiber optic cable in which a protrusion, in which a tear strip is embedded, is larger than the other protrusions. Fig. 13C is a cross-sectional view of a fiber optic cable where the width of a projection in which a tear strip is embedded is smaller than the other projections. Fig.13D is a cross-sectional view of a fiber optic cable in which tensile strength elements are arranged at equal intervals and rip cords are arranged between the tensile strength elements in the circumferential direction. Fig. 14A is an example of a cross-section through a fiber optic cable. Fig. Figure 14B is a cross-sectional view of a fiber optic cable according to a further modification example of the present embodiment. [Description of illustrative examples]

[0010] The optical fiber of the present invention is defined by the appended claims. Examples of a fiber optic cable are described below with reference to the drawings. Examples not covered by the claims are not part of the present invention.

[0011] As in Fig.As shown in Figure 1A, the fiber optic cable 1 comprises a sheath 10, a core 20 housed in the sheath 10 and a number of tensile strength elements 30 embedded in the sheath 10.

[0012] The core 20 comprises a number of fiber optic units 21 and a sheathing tube 22 that encloses these fiber optic units 21. Each of the fiber optic units 21 comprises a number of optical fibers 21a and a binding material 21b that connects the optical fibers 21a. (Definition of direction)

[0013] The central axis of the fiber optic cable 1 is referred to as the central axis O. Furthermore, the longitudinal direction of the fiber optic cable 1 (longitudinal direction of the optical fiber 21a) is simply referred to as the longitudinal direction. The cross-section orthogonal to the longitudinal direction is referred to as the cross-section. In the cross-sectional view ( Fig.1A) A direction that intersects the central axis O is called the radial direction, and a direction that revolves around the central axis O is called the circumferential direction.

[0014] If the fiber optic cable 1 is not circular in cross-section, the central axis O is located in the middle of the fiber optic cable 1.

[0015] As in Fig.As shown in Figure 2, the fiber optic unit 21 is a so-called intermittently bonded fiber optic tape. This means that the fiber optic unit 21 has a number of optical fibers 21a and a number of bonding sections 21c for bonding adjacent optical fibers 21a together. In the intermittently bonded fiber optic tape, the optical fibers 21a spread out in a network-like (spiderweb-like) pattern when several optical fibers 21a are pulled in a direction orthogonal to the longitudinal direction. In particular, an optical fiber 21a is bonded to the adjacent optical fibers 21a at various positions in the longitudinal direction by the bonding sections 21c. Furthermore, the adjacent optical fibers 21a are bonded to each other at a specific distance in the longitudinal direction by the bonding section 21c.

[0016] A thermosetting resin, a UV-curing resin or similar can be used as the adhesive section 21c.

[0017] The multiple fiber optic units 21 are twisted together around the central axis O. The twisting can be spiral or SZ-shaped.

[0018] The encapsulation tube 22 surrounds a number of fiber optic units 21 and is cylindrical in shape. The two end sections (first end section and second end section) of the encapsulation tube 22 overlap circumferentially and form an encapsulation section 22a. The portion of the encapsulation tube 22 that does not belong to encapsulation section 22a is referred to as non-encapsulation section 22b. Non-encapsulation section 22b is located between the first end section and the second end section that form encapsulation section 22a.

[0019] A non-woven fabric, a plastic tape, or a similar material can be used for the sheathing 22. If the sheathing 22 is made of plastic, polyethylene terephthalate, polyester, or a similar material can be used. Furthermore, a water-absorbing tape can be used as the sheathing 22. This tape is obtained by impregnating the non-woven fabric or tape element described above with water-absorbing properties. In this case, the water resistance of the fiber optic cable 1 can be improved. If a plastic tape is used as the sheathing 22, water absorption can be achieved by applying a water-absorbing powder to the surface of the tape element.

[0020] The multiple tensile strength elements 30 are embedded in the sheath 10 at equal intervals in the circumferential direction. The intervals at which the multiple tensile strength elements 30 are embedded need not be equal. The number of tensile strength elements 30 can be changed as required. The material of the tensile strength elements 30 can be, for example, metal wire (steel wire or similar), tensile fiber (aramid fiber or similar), fiber-reinforced plastics (FRP), or similar. Specific examples of FRP include KFRP with Kevlar fibers and PBO-FRP with polyparaphenylenebenzobisoxazole (PBO).

[0021] In addition to the tensile strength element 30, for example a tear strip or similar can be embedded in the sheath 10.

[0022] The sheath 10 is formed into a cylindrical shape centered on the central axis O. The material of the sheath 10 can be polyolefin resin (PO) such as polyethylene (PE), polypropylene (PP), ethylene ethyl acrylate copolymer (EEA), ethylene vinyl acetate copolymer (EVA), ethylene propylene copolymer (EP), polyvinyl chloride (PVC), or similar materials.

[0023] A number of depressions 12 and projections 11 are formed on the outer circumferential surface of the shell 10. The depressions (concavities) 12 and the projections (convexities) 11 are arranged alternately in the circumferential direction. In this way, an irregular shape is formed on the outer circumferential surface of the shell 10. The depressions 12 and the projections 11 extend longitudinally.

[0024] The projection 11 is located circumferentially at the same position as the tensile strength element 30. In other words, the projection 11 lies on a straight line extending from the central axis O towards the center of the tensile strength element 30 in the cross-sectional view. The recess 12 is located at a position that differs from that of the tensile strength element 30 circumferentially. In other words, the recess 12 does not lie on a straight line extending from the central axis O towards the center of the tensile strength element 30 in the cross-sectional view.

[0025] The recess 12 has two connecting sections 12a and a base surface 12b. The connecting section 12a is connected to the radially inner end of the circumferentially adjacent projection 11. The base surface 12b is located between the two connecting sections 12a in each recess 12. As shown in Fig. IB, the connecting sections 12a have a curved surface shape that is convex radially inwards.

[0026] The base surface 12b has a curved surface centered on the central axis O and, in a cross-sectional view, exhibits an arc shape centered on the central axis O. However, the shape of the base surface 12b is not limited to a curved surface centered on the central axis O. For example, the base surface 12b can have a shape in which two connecting sections 12a are joined in a straight line.

[0027] Since, as described above, each of the recesses 12 has the two connecting sections 12a and the bottom surface 12b located between the connecting sections 12a, even if a circumferential force acts on the projection 11, hardly any stress is concentrated in the recess 12. Therefore, cracks and the like are suppressed in the recess 12, and the strength of the shell 10 is increased.

[0028] Furthermore, the core 20 features an intermittently bonded fiber optic tape (fiber optic unit 21) with a number of optical fibers 21a and a number of adhesive sections 21c for the intermittent bonding of the optical fibers 21a in the longitudinal direction. This ensures the stiffness of the fiber optic cable 1 compared to the case where a number of unbonded optical fibers are simply twisted together, and the structure is advantageous with regard to kink resistance and air blowing properties. Moreover, the diameter of the fiber optic cable 1 can be reduced compared to the case where several optical fibers are coated together with a resin, and an increase in transmission loss can be suppressed.

[0029] Furthermore, the connecting section 12a is provided with a curved surface that is radially convex. This more reliably suppresses the concentration of stresses on the connecting section 12a, and the strength of the shell 10 can be further increased.

[0030] Since the sheath 22 has the sheath section 22a, it is also possible to prevent the jacket 10 from coming into contact with the components inside the sheath 22. When the jacket 10 is extruded and shaped, this prevents the optical fiber 21a from being drawn into the softened jacket 10 and thus prevents the length ratio of the optical fiber 21a to the fiber optic cable from becoming unstable. Furthermore, it prevents an increase in transmission losses that would otherwise occur if the optical fiber 21a were pinched between the sheath 22 and the jacket 10.

[0031] The radius of curvature of the outer circumferential surface of the projection 11 can be smaller than the radius of the sheath 10 (the radius of the fiber optic cable 1). According to this configuration, the contact area between the projection 11 and the microchannel (details will be described later) becomes smaller. Therefore, processability can be improved when the fiber optic cable 1 is inserted into the microchannel. The "radius of sheath 10" is the maximum value of the distance between the outer circumferential surface of the projection 11 and the central axis O. If the maximum value is different for each projection 11, the average of each maximum value is defined as the "radius of sheath 10".

[0032] The following describes a specific example of a fiber optic cable 1. (Maximum compressive stress)

[0033] As in Fig.Figure 3 shows how the processability was investigated when the fiber optic cable is inserted into the microchannel D by blowing it with air. The microchannel D is a pipe that has been pre-laid in the ground or similar. During the air blowing process, a seal S is attached to the end of the microchannel D, and a fiber optic cable is inserted into the microchannel D through the opening of the seal S. A pump P is also connected to the seal S to allow air to flow from the seal S into the microchannel D. This creates an air gap between the fiber optic cable and the microchannel D to reduce friction.

[0034] During the installation of the fiber optic cable, the fiber optic cable can be inserted into the microduct D over a long distance, e.g., 2000 m or more. When the fiber optic cable is inserted into the microduct D over such a long distance, the force in the longitudinal direction of the fiber optic cable must be efficiently transferred from the upstream side (-X side) to the downstream side (+X side).

[0035] As a result of careful examination by the inventors of the present application, it was found that the compressive strength (maximum compressive stress) of the fiber optic cable is preferably within a predetermined range in order to adequately transmit the force from the upstream side to the downstream side of the fiber optic cable.

[0036] The following describes the results of the feasibility study of air blowing through the production of several fiber optic cables (test examples 1-1 to 1-7) with varying compressive strengths, as shown in Table 1. Test example 1-8 is a loose tube fiber optic cable. Details of test example 1-8 are described later. [Table 1] Test example 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 Diameter d (mm) 9,2 10,5 10,0 6,1 6,3 8,0 9,4 6,5 Cross-sectional area a (mm2) 66,5 86,6 78,5 29,2 31,2 50,3 69,4 33,2 Secondary cross-sectional moment I 351,7 596,7 490,9 68,0 77,3 201,1 383,2 87,6 Secondary cross-sectional radius i 2,3 2,6 2,5 1,5 1,6 2,0 2,4 1,6 Sample length L' (mm) 11,5 13,1 12,5 7,6 7,9 10,0 11,8 8,1 Contact condition of the edge surface and buckling length 0,5 0,5 0,5 0,5 0,5 0,5 0,5 0,5 Slimming level X 5 5 5 5 5 5 5 5 d / L' 0,8 0,8 0,8 0,8 0,8 0,8 0,8 0,8 Compressive strength (N / mm2) 11,6 9,3 12,8 19,2 19,4 16,4 14,4 32,4 Test for blowing in air NG NG OK OK OK OK OK OK

[0037] The results of the air blowing test for fiber optic cables are shown in the "Air Blowing Test" field in Table 1. More precisely, if each fiber optic cable is blown into microduct D with air and 2000 m can be blown, the result is good (OK), and if 2000 m cannot be blown, the result is not good (NG).

[0038] The microchannel D used for the air blowing test has the shape of a figure eight, as shown in Fig.4 shown. The inner width of the curved section is 18.33 m, and the length of one circumference of the in Fig. The figure eight shown in the diagram is 125 m. Although not shown, a track with a total length of 2000 m is constructed by repeating the figure eight 16 times. The pump P (see Fig. 3) is arranged in an essentially straight section in the shape of a figure eight and blows the fiber optic cable with air into the microchannel D in the direction indicated by arrow F. Fig. 4 in the indicated direction.

[0039] The "compressive strength" in Table 1 refers to a value determined by dividing the maximum compressive load (N), measured for each test example by compressing a specimen of length "specimen length L'(mm)" in Table 1 using a compression testing device, by the "cross-sectional area a (mm²)." The compressive strength is calculated according to JIS K7181: 2011.

[0040] More precisely, a universal general-purpose materials testing machine is used as the compression testing device. Both ends of each sample are inserted into a metal cylinder attached to the compression testing machine. This means that both ends of the sample are firmly supported during the compression test. Each sample is compressed longitudinally at a speed of 1 mm / min. The compressive stress is then measured immediately before each sample buckles and is defined as the "maximum compressive stress".

[0041] The sample length L' of each sample is set such that the value of d / L' is constant (0.8).

[0042] As shown in Table 1, the results of the air blowing tests for test samples (1-1, 1-2) with a compressive strength of 11.6 N / mm² or less are not good. This is because the compressive strength of the fiber optic cable is insufficient, and the fiber optic cable kinks during movement within the microchannel D. When the fiber optic cable kinks in the microchannel D, the force transmitted from the upstream to the downstream end of the fiber optic cable is converted into a force that pushes the fiber optic cable against the inner surface of the microchannel D at the kinked point. This makes it difficult for the force to be transmitted to the downstream end of the fiber optic cable, and the advancement of the fiber optic cable is halted. Consequently, air blowing to 2000 m is deemed not feasible.

[0043] On the other hand, in test examples (1-3 to 1-7) with a compressive strength of 12.8 N / mm² or more, good results can be achieved in the air blowing test. This is because the compressive strength, i.e., the difficulty of deformation with respect to the force in the direction (longitudinal direction) along the central axis O of the fiber optic cable, is within a predetermined amount or more, so that kinking of the fiber optic cable in the microchannel D is suppressed. It is assumed that by suppressing kinking of the fiber optic cable in this way, the force is reliably transferred to the downstream end of the fiber optic cable, and air blowing over a length of 2000 m is possible.

[0044] The results above indicate that the compressive strength of the fiber optic cable is preferably 12.8 N / mm² or higher. This configuration suppresses kinking of the fiber optic cable in the microchannel D and improves the processability of the fiber optic cable.

[0045] As shown in test example 1-8 of Table 1, the result of the air blowing test is also good for the fiber optic cable with a compressive strength of 32.4 N / mm². Therefore, it is assumed that good results for the air blowing test can be achieved if the compressive strength is set to 32.4 N / mm² or less.

[0046] This means that the compressive strength of the fiber optic cable is preferably 12.8 N / mm2 or more and 32.4 N / mm2 or less. (Envelope rate)

[0047] As in Fig.As shown in Figure 1A, a sheath section 22a is formed on the sheath tube 22. As a result of the investigation by the inventors of the present application, it was found that if the ratio of the circumferential length of the sheath section 22a to the total circumferential length of the sheath tube 22 is large, the fiber optic cable is likely to be deformed into a substantially elliptical shape, as shown in Figure 1A. Fig. 5 shown. More precisely, it tends to assume an elliptical shape, such that the direction in which the hull section 22a extends has a principal axis of the elliptical shape. If such a deformation occurs, the seal at the opening (see Fig. 3) of the sealing section S. In addition, the projection 11, which lies on the main axis of the elliptical shape, can be strongly pressed against the inner circumferential surface of the microchannel D, thereby increasing friction.

[0048] This means that it has been shown that the ratio between the sheath section 22a and the total circumference of the sheath tube 22 influences the processability when blowing the fiber optic cable with air.

[0049] Therefore, the result of the test of the preferred ratio of the hull section 22a is described below.

[0050] As in Fig. As shown in Figure 1A, the perimeter length of the envelope section 22a in the cross-sectional view W1 is given. Furthermore, the perimeter length of the non-envelope section 22b is given in Figure W2 (not shown). At this point, the envelope ratio R is defined by the following equation (1). R=W1÷(W1+W2)×100

[0051] The envelope ratio R indicates the ratio of the circumferential length of the envelope section 22a to the total circumferential length of the envelope tube 22.

[0052] In the present example, as shown in Table 2, several fiber optic cables (test examples 2-1 to 2-6) with different encapsulation rates R are produced.

[0053] The measurement result for the transmission loss of each fiber optic cable is given in Table 2 in the field "Transmission Loss". More precisely, at a wavelength of 1550 nm, the result is good (OK) if the transmission loss is 0.30 dB / km or less, and the result is not good (NG) if the transmission loss is greater than 0.30 dB / km.

[0054] The meaning of the field “Test for blowing with air” in Table 2 is the same as in Table 1. [Table 2] Test example 2-1 2-2 2-3 2-4 2-5 2-6 Envelopment rate R 27% 20% 13% 9% 5% 3% Transmission loss OK OK OK OK OK NG Test for blowing in air NG OK OK OK OK OK

[0055] As can be seen from Table 2, the transmission loss results in test examples (2-1 to 2-5) are good with a cladding ratio R of 5% or more. In contrast, the transmission loss result for test example (26) with a cladding ratio R of 3% is not good. This is assumed to be due to the fact that when the cladding ratio R is significantly small, the optical fiber protrudes from the cladding section 22a to the outside of the cladding tube 22, causing local bending of the optical fiber and increasing transmission loss.

[0056] For test samples (2-2 to 2-6) with a envelopment rate R of 20% or less, the results of the air blowing test are good. However, for test sample (2-1) with a envelopment rate R of 27%, the result of the air blowing test is not good. This is because the envelopment rate R is very high and, as described above, the fiber optic cable is deformed into an elliptical shape, thus reducing its processability during air blowing.

[0057] The results above indicate that the encapsulation rate R is preferably 5% or more and 20% or less. With this configuration, it is possible to improve the feasibility of air blowing while simultaneously suppressing an increase in transmission losses due to local bending of the optical fiber. (Cross-sectional area of ​​the depressions)

[0058] When the fiber optic cable is inserted into the microchannel D by blowing air in, at least some of the air flows through the recess 12 as a flow path. A portion of the air flowing through the recess 12 then flows between the projection 11 and the microchannel D, forming an air layer between them to reduce friction. The inventors of the present application have determined in their investigations that the cross-sectional area of ​​the recesses 12 serving as airflow paths is preferably located within a predetermined range to ensure the proper formation of the aforementioned air layer. The results of the investigation are described below.

[0059] In the present example, a number of fiber optic cables (test examples 3-1 to 3-6) with different cross-sectional areas A of the in Fig.The 6 shown recesses are produced. The cross-sectional area A of the recesses is the cross-sectional area of ​​the space defined by the closed curve L and all recesses 12 when the closed curve L is drawn in contact with the radially outer end of each projection 11 in the cross-sectional view. In other words, the cross-sectional area A of the recesses is the difference between the cross-sectional area of ​​the fiber optic cable of the present example and the cross-sectional area of ​​the virtual fiber optic cable having the closed curve L as its outer circumferential surface.

[0060] The closed curve L is normally circular with the central axis O at its center. However, due to the deformation of the fiber optic cable, the closed curve L can have an elliptical shape. [Table 3] Test example 3-1 3-2 3-3 3-4 3-5 3-6 Cross-sectional area A of the depressions (mm2) 5,2 4,8 3,4 2,8 1,3 0,0 Test for blowing in air NG OK OK OK OK NG

[0061] As shown in Table 3, the results of the air blow test for test example (3-1) with a recess cross-sectional area A of 5.2 mm² are not good. This is because the seal between the gasket S and the fiber optic cable deteriorates when the recess cross-sectional area A is significantly large, and backflow of air from the interior of the microchannel D is likely. If the amount of air flowing back from the interior of the microchannel D is large, the amount of air between the inner surface of the microchannel D and the fiber optic cable decreases, and friction increases. This friction is thought to impede the transmission of force from the upstream to the downstream side of the fiber optic cable, causing the fiber optic cable to stall.

[0062] In contrast, for test examples (3-2 to 3-5) where the cross-sectional area A of the recesses is 1.3 mm² or more and 4.8 mm² or less, the results of the air blowing test are good. This is because the cross-sectional area A of the recesses is sufficiently small, the seal between the gasket S and the fiber optic cable is good, and the backflow of air from the interior of the microchannel D is suppressed. That is, it is assumed that the friction is reduced by the sufficient air between the inner surface of the microchannel D and the fiber optic cable, and the force can be transmitted from the upstream side to the downstream side of the fiber optic cable.

[0063] Since the sheath 10 in test example 3-6 does not have an irregular shape, the friction between the inner surface of the microchannel D and the fiber optic cable is high, and the advancement of the fiber optic cable is stopped.

[0064] The results above indicate that the cross-sectional area A of the recesses is preferably in the range of 1.3 mm² or more and 4.8 mm² or less. This configuration ensures a tight seal between the seal S and the fiber optic cable and improves the effectiveness of the air blowing process. (Twisted shape of the coat)

[0065] The recess 12 serves as an airflow path when the fiber optic cable is blown with air. For example, the state of the airflow changes when the recesses 12 extend linearly along the longitudinal direction (see Fig.7A) and when the recesses 12 are spirally twisted along the longitudinal direction (see Fig. 7B). It is assumed that the difference in airflow conditions affects the feasibility when the fiber optic cable is blown in with air.

[0066] Therefore, the results of the investigation into the relationship between the twist shape of the sheath 10 and its feasibility during air blowing are described with reference to Table 4. Here, a number of fiber optic cables (test examples 4-1 to 4-5) with different twist angles θ are prepared. The twist angle θ is the amount of twist around the central axis O of the sheath 10 (projection 11) per 1 m in the longitudinal direction. For example, if θ = 90° / m, this means that the positions of the projections 11 differ by 90° around the central axis O when comparing sections separated by 1 m in the longitudinal direction of the cable. In test examples 4-2 to 4-5, the tensile strength elements 30 are twisted around the central axis O with a twist angle θ similar to that of the projections 11.Therefore, the fiber optic cables of test examples 4-2 to 4-5 have essentially the same cross-sectional shape at every point in the longitudinal direction. [Table 4] Test example 4-1 4-2 4-3 4-4 4-5 Twist angle θ (° / m) 0 5 10 120 180 Test for blowing in air NG NG OK OK OK

[0067] As can be seen from Table 4, the results of the air blowing test are good for test examples (4-3 to 4-5) where the twist angle 10 < θ (° / m) < 180. This is assumed to be due to the fact that the pressure of the air flowing in the recesses 12 can be effectively converted into a thrust that drives the fiber optic cable downstream. That is, the air flowing in the recesses 12 exerts a pressure in the direction perpendicular to the side surface of the projection 11. Therefore, the larger the value of θ, the more the side surface of the projection 11 is inclined with respect to the longitudinal direction, and the more the air pressure is converted into a force in the longitudinal direction.

[0068] On the other hand, in the test examples (4-1, 4-2) where the twist angle θ is 5° / m or less, the results of the air blowing test are not good. It is assumed that this is because the pressure of the air flowing in the recesses 12 cannot be effectively used to push the fiber optic cable.

[0069] From the above explanations, it follows that the twist angle of the sheath 10 is preferably 10 < θ (° / m) < 180. With this configuration, the pressure of the air flowing in the recesses 12 can be effectively converted into a force to drive the optical fiber cable towards the downstream side, and the feasibility of blowing in air can be improved.

[0070] If the sheath 10 is shaped such that 10 < θ (° / m) < 180, the sheath 10 can have a twisted shape. Alternatively, the sheath 10 can be twisted by utilizing the force with which the spirally twisted fiber optic unit 21 attempts to unwind.

[0071] Next, the results of the investigation into the influence of the twisted shape of the sheath 10 and the tensile strength elements 30 on the bending stiffness of the fiber optic cable are described. In the present example, two fiber optic cables from test examples 5-1 and 5-2 are used (see Fig. 8) manufactured. The fiber optic cable of test example 5-1 is a fiber optic cable similar to that of test example 4-1. As in Fig. As shown in Figure 7A, the sheath 10 and the tensile strength elements 30 are not twisted. In the fiber optic cable of test example 5-2, the sheath 10 and the tensile strength elements 30 are spirally twisted, as shown in Figure 7A. Fig.Figure 7B shows the distance in the longitudinal direction as 700 mm. In both test examples 5-1 and 5-2, a core 20 is used in which a number of optical fiber units 21 are twisted in an SZ shape. In both test examples 5-1 and 5-2, the number of projections is 11 and the number of tensile strength elements is 30.

[0072] Fig. Figure 8 is a diagram showing the bending stiffness values ​​for each measurement angle X for the fiber optic cable of test examples 5-1 and 5-2. As shown in Fig. Figure 9 shows that the measuring angle X indicates the angle at which a force is applied when measuring the bending stiffness. Since, in the present example, a force is exerted on each of the central sections of the 12 projections 11 and the 12 recesses 12, the measuring angle X is given in increments of 15° (= 360° + 24).

[0073] As in Fig.As shown in Figure 8, the fiber optic cable from test example 5-1 exhibits a large variation in the bending stiffness value for each measurement angle X. Conversely, the variation in the bending stiffness value for each measurement angle X is smaller for the fiber optic cable from test example 5-2 than for test example 5-1. This difference is due to whether the tensile strength elements 30 are spirally twisted and arranged or not. Since the tensile strength elements 30 in test example 5-2 are spirally arranged, the bending stiffness is assumed to be uniform in the circumferential direction.

[0074] As described above, the tensile strength elements 30 are embedded in the projections 11 of the sheath 10, and the projections 11 and the tensile strength elements 30 are formed into a helically twisted shape centered on the central axis O, so that the bending stiffness of the fiber optic cable can be made uniform in the circumferential direction. In this way, a fiber optic cable can be provided that is easier to handle and easier to install in a microduct. (Material of the tension member)

[0075] The results of the material testing of tensile strength element 30 are described below with reference to Tables 5 and 6. Test examples 6-1 to 6-3 shown in Table 5 are fiber optic cables with 288 optical fibers. Test examples 7-1 and 7-2 shown in Table 6 are fiber optic cables with 144 optical fibers. [Table 5] TM material Tensile modulus of elasticity (kg / mm2) TM diameter (mm) TM Cross-sectional area (mm2) Number of TMs (pieces) Tensile strength index ratio of outer diameter Test example 6-1 KFRP 5000 0,5 0,196 12 1,00 1,00 Test example 6-2 PBO- FRP 25000 0,25 0,049 12 1,25 0,94 Test example 6-3 PBO- FRP 25000 0,3 0,071 8 1,20 0,95 [Table 6] TM material Tensile modulus of elasticity (kg / mm2) TM diameter (mm) TM cross-sectional area (mm2) Number of TMs (pieces) Tensile strength index ratio of outer diameter Test example 7-1 KFRP 5000 0,5 0,196 10 1,00 1,00 Test example 7-2 PBO- FRP 25000 0,25 0,049 10 1,25 0,92

[0076] In Tables 5 and 6, “TM material”, “tensile modulus”, “TM diameter”, and “TM cross-sectional area” denote the material, the tensile modulus, the diameter, and the cross-sectional area, respectively, of the tensile strength element 30. “Number of TMs” indicates the number of tensile strength elements 30 included in the test example. The surface of the sheath 10 is provided with the same number of projections 11 as the tensile strength elements 30 in each test example, and the tensile strength element 30 is located within each projection 11.

[0077] The “tensile strength index” given in Table 5 indicates the ratio of the tensile force applied longitudinally to the fiber optic cables of test examples 6-1 to 6-3 to achieve a predetermined strain rate a (%), based on test example 6-1. For example, since test example 6-2 has a tensile strength index of 1.25, a tensile force 1.25 times greater than that of test example 6-1 is required before the strain rate a is reached. The tensile strength index given in Table 6 is also the same as the tensile strength index in Table 5, except that the tensile force of test example 7-1 is used as the reference.

[0078] The strain rate a is defined within a range where the fiber optic cable stretches relative to the tensile force. Therefore, the tensile strength index of test samples 6-2, 6-3, and 7-2 is not affected by the value of the strain rate a.

[0079] The “outer diameter ratio” given in Table 5 represents the size of the outer diameter of the fiber optic cables of test examples 6-2 and 6-3 relative to the outer diameter of the fiber optic cable of test example 6-1. For example, the outer diameter of the fiber optic cable of test example 6-2 is 0.94 times the outer diameter of the fiber optic cable of test example 6-1. The same applies to the “outer diameter ratio” in Table 6, which represents the size of the outer diameter of the fiber optic cables of test example 7-2 relative to the outer diameter of the fiber optic cable of test example 7-1. Since the jacket 10 of each test example is designed to have the same minimum thickness, the outer diameter ratio is smaller the smaller the diameter of the tensile strength element 30.

[0080] As can be seen from Table 5, the tensile strength indices of test examples 6-2 and 6-3 are 1.25 and 1.20, respectively, which makes longitudinal elongation difficult and effectively protects the optical fiber from tensile stress. Furthermore, the TM diameters of test examples 6-2 and 6-3, at 0.25 mm and 0.30 mm respectively, are significantly smaller than the TM diameter of test example 6-1. Thus, the outer diameter of the fiber optic cables of test examples 6-2 and 6-3 is smaller than that of test example 6-1.

[0081] As shown in Table 6, the same results as in Table 5 are also achieved in test examples 7-1 and 7-2 with 144 optical fibers.

[0082] As described above, by using PBO-FRP with a large tensile modulus of elasticity as the material for the tensile strength element 30, it is possible to provide a fiber optic cable that is difficult to stretch longitudinally under tension and has a small outer diameter. (Number of tensile strength elements for projections)

[0083] The number of tensile strength elements 30 arranged in the projections 11 can be changed as appropriate. For example, a fiber optic cable with a cross-section as shown in Fig. 10 are used as shown. In the Fig. In Figure 10, two tensile strength elements 30 are embedded in a projection 11 in a cross-sectional view of the fiber optic cable. In this way, two or more tensile strength elements 30 can be arranged within a projection 11. (Adjusting the twist angle)

[0084] Next, the effect of twisting the multiple fiber optic units 21 in an SZ shape is described with reference to Table 7. [Table 7] Set angle (°) Twist angle of the mantle (°) Test for blowing in air Transmission loss Determination Test example 9-1 0 0 1500 m NG NG Test example 9-2 ±350 ±30 2000 m or more OK OK Test example 9-3 ±500 ±50 2000 m or more OK OK Test example 9-4 ±700 ±70 2000 m or more OK OK

[0085] The fiber optic cables of test examples 9-1 to 9-4 have a cross-sectional shape as described in Fig. Figure 1A shows the configuration. The number of projections 11 and tensile strength elements 30 is 12. An intermittently bonded fiber optic tape is used as the fiber optic unit 21. The "setting angle" in Table 7 specifies a setting angle when the multiple fiber optic units 21 are twisted in an SZ shape. For example, in a case where the setting angle is ±350°, when the core 20 is housed in the sheath 10, a process of rotating the bundle of optical fiber units 21 by 350° in the CW direction (clockwise) and then rotating the bundle by 350° in the CCW direction (counterclockwise) is repeated. In this way, the bundle of fiber optic units 21 is housed in the sheath 10 in a state where it is twisted in an SZ shape.

[0086] When the bundle of fiber optic units 21 is twisted in an SZ shape, it attempts to untwist itself into the shape it was in before twisting. Wrapping the bundle of fiber optic units 21 with the sheath 22 and the jacket 10 before untwisting prevents it from retaining the SZ-shaped twisted state within the fiber optic cable.

[0087] Here, the sheath 10 inside the fiber optic cable absorbs the force that the fiber optic unit 21 attempts to untwist through the outer sleeve 22. Since the sheath 10 is deformed by this force, an SZ-shaped twist also forms on its surface. In this case, the tensile strength elements 30 embedded in the sheath 10 are also twisted in an SZ shape. The SZ-shaped twist angle that thus appears on the surface of the sheath 10 is given in Table 7 under "Sheath Twist Angle". In the fiber optic cable of test example 9-1, the fiber optic unit 21 is not twisted in an SZ shape, so no SZ-shaped twist occurs on the surface of the sheath 10. In the fiber optic cables of test examples 9-2 to 9-4, however, an SZ-shaped twist appears on the surface of the sheath 10, since the fiber optic unit 21 is twisted in an SZ shape.

[0088] The larger the tilt angle, the greater the force with which the fiber optic unit 21 attempts to untwist itself. Therefore, as shown in Table 7, the larger the tilt angle, the greater the "twist angle of the sheath".

[0089] The "Air Blowing Test" field in Table 7 shows the results of the air blowing tests on the fiber optic cables of test examples 9-1 to 9-4. The details of the air blowing tests are the same as in Table 1. For example, in test example 9-1, it is possible to blow 1500 m of cable in the air blowing test, but it is difficult to blow more. In contrast, in test examples 9-2 to 9-4, it is possible to blow 2000 m or more in the air blowing test. The data on "transmission loss" in Table 7 are the same as in Table 2.

[0090] As shown in Table 7, the fiber optic units of test examples 9-2 to 9-4 achieve better results in the air blowing test than test example 9-1. This is because the protrusions 11 and the recesses 12 are twisted in an SZ shape, allowing the pressure of the air flowing in the recesses 12 to be effectively converted into thrust, which drives the fiber optic cable downstream. That is, the air flowing in the recesses 12 exerts a pressure in the direction perpendicular to the side surface of the protrusion 11. Therefore, the air pressure is assumed to be converted into a force in the longitudinal direction, thus improving the result of the air blowing test compared to test example 9-1, where the sheath 10 is not twisted.Furthermore, in test examples 9-2 to 9-4, when the SZ-shaped twist is applied to the sheath 10, the tensile strength elements 30 embedded in the sheath 10 are also twisted in an SZ shape, and the bending stiffness of the fiber optic cable is homogenized in the circumferential direction. This point is also considered a factor for improving the results of the air blowing test.

[0091] The bending stiffness values ​​of the fiber optic cables of test examples 9-1 and 9-2 for each measurement angle X are given in Fig. Figure 11 illustrates the procedure for measuring the bending stiffness values. This procedure is the same as in test examples 5-1 and 5-2. Fig. As can be seen in Figure 11, the fiber optic cable of test example 9-2 exhibits a lower variation in the bending stiffness value for each measurement angle X than the fiber optic cable of test example 9-1.

[0092] From the above explanations, it follows that by twisting a number of fiber optic units 21 into an SZ shape and applying an SZ-shaped twist to the sheath 10, a fiber optic cable can be created whose bending stiffness is uniform in the circumferential direction and which is better suited for blowing with air. In the present example, the fiber optic unit 21 is twisted in an SZ shape. However, it is assumed that the same result can be achieved if a number of optical fibers 21a are twisted in an SZ shape without being bundled into a single unit. That is, by twisting the several optical fibers 21a in an SZ shape, the effect described above can be achieved when an SZ-shaped twist is applied to the sheath 10.

[0093] As shown in Table 7, it was found that in test examples 9-2, 9-3, and 9-4, in addition to the air blowing test, the transmission loss was also good. Therefore, by adjusting the SZ twist angle of the optical fiber unit 21 so that the twist angle of the cladding is between ±30° and ±70°, it is possible to provide a fiber optic cable with good transmission loss characteristics. (Low-friction material)

[0094] Since the sheath 10 is blown with air into the fiber optic cable with the microchannel D (see Fig.3) where the jacket 10 comes into contact with the microchannel, it is preferably made of a material with a low coefficient of friction (hereinafter referred to as a low-friction material). However, it is assumed that the strength of the jacket 10 cannot be guaranteed or that the costs will increase if the entire jacket 10 is made of a low-friction material. Therefore, an investigation is carried out in which a portion of the jacket 10 that is in contact with the microchannel is made of a low-friction material. A description is given below with reference to Table 8. [Table 8] Transverse cross-sectional shape cable outer diameter Result of the test for blowing in air Test example 10-1 Fig. 1A 12 mm 2000 m Test example 10-2 Fig. 1A 8 mm 2000 m or more Test example 10-3 Fig. 12A 12 mm 2000 m or more Test example 10-4 Fig. 12A 8 mm 2000 m or more Test example 10-5 Fig. 12B 12 mm 2000 m or more Test example 10-6 Fig. 12B 8 mm 2000 m or more Test example 10-7 Fig. 12C 12 mm 2000 m or more Test example 10-8 Fig. 12C 8 mm 2000 m or more

[0095] As shown in Table 8, the fiber optic cables of test examples 10-1 to 10-8 are prepared. In the fiber optic cables of test examples 10-1 and 10-2, the cladding 10 consists of a single base material B (average dynamic coefficient of friction: 0.27). In the fiber optic cables of test examples 10-3 and 10-4, as shown in Fig. As shown in Figure 12A, the upper part of the projection 11 is made of a low-friction material M (average dynamic coefficient of friction 0.20), and the remaining part of the sleeve 10 is made of the base material B. That is, the low-friction material M has a lower coefficient of friction than the base material B. The average dynamic coefficient of friction is measured according to JIS K7125.

[0096] In the fiber optic cables of test examples 10-5 and 10-6, as in Fig.As shown in Figure 12B, a layer of the low-friction material M is provided on the entire surface of the sheath 10 formed from the base material B. In the fiber optic cables of test examples 10-7 and 10-8, as shown in Fig. As shown in Figure 12C, the projections 11 and the depressions 12 are formed from the low-friction material M on the outer circumferential surface of the cylindrical base material B.

[0097] The fiber optic cables of test examples 10-3 to 10-8 have in common that the sheath 10 is formed from the base material B and the low-friction material M, and that the low-friction material M is arranged at least on the upper side of the projection 11. In this description, the "upper side" of the projection 11 refers to a section that is curved such that it is convex radially outwards.

[0098] An air blowing test is performed on the fiber optic cables of test examples 10-1 to 10-8. The blowing speed is approximately 60 m / min at the beginning of the test. In all test examples 10-1 to 10-8, the blowing speed decreases with increasing blowing distance. In test example 10-1, the blowing speed is almost zero when the blowing distance is 2000 m. On the other hand, test examples 10-2 to 10-8 confirm that the blowing speed is 30 m / min or more when the blowing distance is 2000 m, and that blowing distances of 2000 m or more are sufficiently achievable. As described above, better results are obtained with the fiber optic cables of test examples 10-2 to 10-8 than with test example 10-1.Since test examples 10-2 and 10-1 have the same cross-sectional shape, but test example 10-1 has a large outer diameter and a large contact area with a microchannel, it is assumed that the friction increases and the property for blowing in air is less than with test example 10-2.

[0099] On the other hand, in test examples 10-3, 10-5 and 10-7, friction is reduced by shaping the part that is in contact with the microchannel with the low-friction material M, and the property for blowing in air can even be improved in the fiber optic cable with an outer diameter of 12 mm or more.

[0100] Since the low-friction material M, as described above, is arranged at least on the upper surface of the projection 11, it is possible to provide a fiber optic cable with good properties for air blowing. Furthermore, by forming the sheath 10 with the base material B and the low-friction material M, it is possible to improve the strength of the sheath 10 and reduce the cost compared to the case where the entire sheath 10 is formed from the low-friction material M.

[0101] However, considering the required air blowing capability for the fiber optic cable 1 and the cost, the entire sheath 10 can be made of the low-friction material M. (tear cord)

[0102] When connecting and disassembling fiber optic cables, it is necessary to remove the core 20 from inside the sheath 10. The structures of Fig.13A to 13C are proposed as the arrangement of the tear strip to facilitate access to core 20.

[0103] At the in Fig. In the fiber optic cable 1 shown in Figure 13A, part of the tensile strength element 30 is replaced by the tear strip 40, as shown in Figure 13A. Fig. Figure 1A shows this. More precisely, two tear-off cords 40 are embedded in the projections 11 of the sheath 10 and arranged in such a way that they clamp the core 20 between them.

[0104] A yarn obtained by twisting fibers such as polypropylene (PP) and polyester can be used as the tear strip 40. The tensile strength element 30 is designed to protect the optical fiber 21a from tensile stress, while the tear strip 40 is designed to tear the sheath 10. Therefore, the materials of the tear strip 40 and the tear-resistant element 30 are different. In particular, the tensile modulus of elasticity of the tensile strength element 30 is higher than that of the tear strip 40. Furthermore, the tear strip 40 is more flexible than the tensile strength element 30.

[0105] As in Fig.As shown in Figure 13A, the tear strip 40 can be embedded in the projection 11 of the sheath 10, thus preventing the sheath 10 from becoming thin. When the core 20 is removed from inside the sheath 10, part of the projection 11 is cut to allow the tear strip 40 to emerge, and the tear strip 40 is pulled lengthwise along the fiber optic cable. This tears open the sheath 10, allowing the core 20 to be removed.

[0106] As in Fig. As shown in Figure 13A, when manufacturing a fiber optic cable in which a pair of rip cords 40 are arranged to enclose the core 20, access to the core 20 can be satisfactorily achieved. The number of rip cords 40 contained in the fiber optic cable can be one, three, or more.

[0107] As described above, in the cross-sectional view, the tear strips 40 are positioned within some of the projections 11 and the tensile strength elements 30 are positioned within the other projections 11, which facilitates access to the core 20 in the optical fiber cable while protecting the optical fiber 21a from stress.

[0108] To indicate the position where the tear strip 40 is embedded, the projection 11 in which the tear strip 40 is embedded can be marked (with paint or similar). Alternatively, as shown in the Fig. 13B, Fig. 13C and Fig. As shown in 13D, the shape of the projection 11, in which the tear strip 40 is embedded, differs from the shape of the other projections 11. In the example of Fig.13B are the projections 11 in which the tear-off cords 40 are embedded, directed radially further outwards than the other projections 11. In the example of Fig. 13C is the width of the projections 11 in which the tear strip 40 is embedded circumferentially, smaller than that of the other projections 11.

[0109] In the example of Fig. In 13D, the tear strip 40 is arranged so that it is in contact with the core 20. Furthermore, the tensile strength elements 30 are arranged at equal intervals in the circumferential direction, and the tear strips 40 are positioned between adjacent tensile strength elements 30 in the circumferential direction. Then, two tensile strength elements 30, which enclose the tear strip 40, are arranged within a projection 11.

[0110] Through the in the Fig. 13B, Fig. 13C and Fig.The position of the tear strip 40 is easily recognizable from the outside of the fiber optic cable in the 13D depicted shapes.

[0111] It should be noted that the technical scope of the present invention is defined by the attached claims.

[0112] As in Fig. As shown in Figure 14A, the inner surface of the recess 12 can, for example, be a curved, radially inwardly convex surface.

[0113] As in Fig. As shown in Figure 14B, the number of projections 11 does not have to match the number of tensile strength elements 30. As shown in Fig. As shown in Figure 14B, the tensile strength element 30 can be arranged closer to the inner circumferential surface than to the outer circumferential surface of the shell 10.

[0114] Furthermore, it is possible to replace the components of the examples described above with known components, and the examples described above can be combined in a suitable manner.

[0115] According to an illustrative example, a fiber optic cable is provided comprising a sheath and a core housed within the sheath, which has an intermittently bonded fiber optic tape. This tape includes a number of optical fibers and a number of bonding sections for the intermittent bonding of the optical fibers in a longitudinal direction. Additionally, recesses and projections are arranged alternately in a circumferential direction on an outer circumferential surface of the sheath. Each recess comprises two connecting sections, each connected to the radial inner ends of two adjacent projections, and a bottom surface located between the two connecting sections.

[0116] The fiber optic cable according to this example may also have one or more of the following optional features.

[0117] The connecting sections can be formed in a curved, radially inwardly curved surface shape.

[0118] The optical cable can withstand a compressive strength of 12.8 N / mm². 2 or more and 32.4 N / mm 2 or less.

[0119] The core may have a sheathing tube that encloses the intermittently bonded fiber optic tape.

[0120] The sheath tube can have a first and a second end section that overlap to form a sheath section, and a non-sheath section that lies between the first and the second end section.

[0121] If the circumference of the envelope section is W1 and the circumference of the non-envelope section is W2, the envelope rate R, which is calculated as R = W1 ÷ (W1 + W2) x 100, can be in a range of 5% or more and 20% or less.

[0122] In a cross-sectional view, the cross-sectional area A of the depressions, which is a cross-sectional area of ​​a space defined by closed curves tangential to the radial outer ends of the number of protrusions and all depressions, can be in a range of 1.3 mm2 or more and 4.8 mm2 or less.

[0123] If the twist angle of the sheath per 1 m in the longitudinal direction of the fiber optic cable is θ (° / m), the relationship 10 < θ < 180 can be satisfied.

[0124] The radius of curvature of each outer circumferential surface of the projections can be smaller than the radius of the mantle.

[0125] The fiber optic cable may contain tensile strength elements embedded in projections within the cladding. These projections and the tensile strength elements may have a helically twisted shape centered on a central axis of the fiber optic cable.

[0126] The fiber optic cable may include tensile strength elements embedded in the projections in the jacket. These tensile strength elements may be made of PBO-FRP.

[0127] The fiber optic cable can contain a number of tensile strength elements embedded in the jacket. In a cross-sectional view, the majority of the tensile strength elements can be located within each of the projections in the jacket.

[0128] A number of intermittently bonded optical fiber tapes, including the intermittently bonded optical fiber tape, can be provided, and an SZ-shaped twist can be applied to the sheath by twisting the number of intermittently bonded optical fiber tapes in an SZ shape.

[0129] The sheath can be formed from a base material and a low-friction material with a coefficient of friction that is smaller than the coefficient of friction of the base material, and the low-friction material can be arranged at least on the upper surfaces of the projections.

[0130] The fiber optic cable may contain tensile strength elements and rip cords embedded in the cladding. In a cross-sectional view, the rip cords may be located within some of the projections and the tensile strength elements within the other projections. [List of reference symbols] 1 fiber optic cable 10 coats 11 lead 12 In-depth study 12a Connecting section 12b Floor area 20 core 21 fiber optic unit (intermittently bonded fiber optic tape) 21a Optical fiber 21c Adhesive section 22 Sheathing hose 22a Envelope section 22b Non-envelope section 30 tensile strength element 40 Tear cord B Basic material low-friction material QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 6963686

[0004] JP 2016080747A

[0004] JP 2013109172A

[0004] Cited non-patent literature

[0000] JIS K7181: 2011

[0039]

Claims

[1] Fiber optic cable (1) comprising: a coat (10); a number of tensile strength elements (30) embedded in the shell (10); a core (20) housed in the cladding (10) and having an intermittently bonded fiber optic ribbon (21) comprising: optical fibers (21a); and Adhesive portions (21c) which intermittently bond the optical fibers (21a) together in a longitudinal direction; and a sheathing tube (22) enclosing the intermittently bonded fiber optic ribbon (21), the sheathing tube (22) comprising: a sheath portion (22a), wherein a first end portion of the sheath tube (22) overlaps with a second end portion of the sheath tube (22); and a non-envelope portion (22b) positioned between the first end portion and the second end portion, characterized by , that: the fiber optic cable (1) has a compressive strength of 12.8 N / mm 2 or more and 32.4 N / mm 2 or less. [2] Fiber optic cable (1) comprising: a coat (10); a plurality of tensile strength elements (30) embedded in the shell (10); a core (20) housed in the cladding (10) and comprising an intermittently bonded fiber optic ribbon (21) comprising: optical fibers (21a); and Adhesive portions (21c) which intermittently bond the optical fibers (21a) together in a longitudinal direction; and a sheathing tube (22) which encloses the intermittently bonded fiber optic ribbon (21), the sheathing tube (22) comprising: a sheath portion (22a), wherein a first end portion of the sheath tube (22) overlaps with a second end portion of the sheath tube (22); and a non-envelope portion (22b) positioned between the first end portion and the second end portion, characterized by , that: the number of tensile strength elements (30) is between 8 and 12. [3] Fiber optic cable (1) comprising: a coat (10); a core (20) housed in the cladding (10) and having an intermittently bonded fiber optic (21) ribbon comprising: optical fibers (21a); and Adhesive portions (21c) which intermittently bond the optical fibers (21a) together in a longitudinal direction; and characterized by , that: the fiber optic cable (1) has a compressive strength of 12.8 N / mm 2 or more and 32.4 N / mm 2 or less. [4] Fiber optic cable (1) according to claim 3, further comprising: a number of tensile strength elements (30) embedded in the sheath (10). [5] Fiber optic cable (1) according to one of claims 1 to 4, wherein recesses (12) and projections (11) are arranged alternately in the circumferential direction on an outer peripheral surface of the sheath (30). [6] Fiber optic cable (1) according to claim 5, wherein the inner surfaces of the recesses (12) are curved surfaces which are convex radially inward. [7] Fiber optic cable (1) according to claim 5 or 6, wherein in a cross-sectional view, a cross-sectional area of the recesses (12) enclosed by closed curves tangential to the radially outer ends of the projections (11) and all the recesses (12) is 1.3 mm 2 or more and 4.8 mm 2 or less. [8] Fiber optic cable (1) according to one of claims 1, 2 and 4, wherein Recesses (12) and projections (11) are arranged alternately in a circumferential direction on an outer circumferential surface of the casing (30), and the number of projections (11) does not correspond to the number of tensile strength elements (30). [9] Fiber optic cable (1) according to one of claims 1 to 8, further comprising a tear cord (40). [10] Fiber optic cable (1) according to claim 9, wherein the tear cord (40) is arranged to be in contact with the core (20). [11] Fiber optic cable (1) according to one of claims 1 to 10, wherein the sheath (10) is formed from a polyolefin resin. [12] Fiber optic cable (1) according to one of claims 1 to 11, wherein the sheath (10) is formed into a cylindrical shape. [13] Fiber optic cable (1) according to claim 1 or 4, wherein the number of tensile strength elements (30) is between 8 and 12. [14] Fiber optic cable (1) according to one of claims 1 to 13, wherein the outer diameter of the sheath (10) is greater than or equal to 6.1 mm. [15] Fiber optic cable (1) according to claim 3, wherein the core (20) comprises a sheath tube (22) enclosing the intermittently bonded fiber optic ribbon (21). [16] The fiber optic cable (1) according to claim 15, wherein the sheath tube (22) has a first end portion and a second end portion overlapping each other to form a sheath portion (22a), and a non-sheath portion (22b) disposed between the first end portion and the second end portion. [17] The fiber optic cable (1) according to any one of claims 1, 2 and 16, wherein when a circumferential length of the sheath portion (22a) is W1 and a circumferential length of the non-sheath portion (22b) is W2, a sheath rate R obtained by R = W1 / (W1 + W2) x 100 is in a range of 5% or more and 20% or less. [18] Fiber optic cable (1) according to one of claims 1 to 17, wherein when a twist angle of the sheath (10) per 1 m along the longitudinal direction of the optical fiber cable (1) is θ in ° / m, 10 < θ < 180. [19] Fiber optic cable (1) according to claim 5, wherein a radius of curvature of each outer peripheral surface of the projections (11) is smaller than a radius of the sheath (10). [20] Fiber optic cable (1) according to one of claims 1, 2 and 4, wherein Recesses (12) and projections (11) are arranged alternately in a circumferential direction on an outer circumferential surface of the casing (30), and the projections (11) and the tensile strength elements (30) have a spirally twisted shape centered on a central axis (O) of the optical fiber cable (1). [21] A fiber optic cable (1) according to claim 20, wherein the bending stiffness value in the circumferential direction is uniform for each 15° increment of the measuring angle, the measuring angle indicating an angle at which a force is applied in measuring the bending stiffness. [22] Fiber optic cable (1) according to one of claims 1, 2 and 4, wherein the tensile strength elements (30) are formed of polyparaphenylenebenzobisoxazole fiber reinforced plastic (PBO-FRP). [23] Fiber optic cable (1) according to one of claims 1, 2 and 4, wherein Recesses (12) and projections (11) are arranged alternately in a circumferential direction on an outer circumferential surface of the casing (30), and in a transverse cross-sectional view, the number of tensile strength elements (30) are arranged within each of the projections (11) in the shell (10). [24] Fiber optic cable (1) according to one of claims 1 to 23, wherein a number of intermittently bonded fiber optic ribbons (21) including the intermittently bonded fiber optic ribbon (21) are provided, and an SZ-shaped twist is applied to the sheath (10) by twisting the plurality of intermittently bonded fiber optic ribbons (21) in an SZ shape. [25] Fiber optic cable (1) according to claim 5, wherein the casing (10) is formed from a base material (B) and a low-friction material (M) having a friction coefficient that is smaller than the friction coefficient of the base material (B), and the low-friction material (M) is arranged at least on the upper sides of the projections (11).

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