fiber optic cable

Abstract

An optical fiber cable (1) comprises: a core (10) that includes optical fibers (11); a first protective layer (20) that covers the core (10); and a second protective layer (50) that covers the first protective layer (20). At least one integrated region (20a) that is in pressure-contact with or fixed to the second protective layer (50) and at least one non-integrated region (20b) that is not in pressure-contact with or fixed to the second protective layer (50) are provided to the outer circumferential surface (20s) of the first protective layer (20).

Description

[Technical Field]

[0001] The present invention relates to optical fiber cables. This application claims priority based on Japanese Patent Application No. 2022-048418, filed on March 24, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] Patent Document 1 discloses an optical fiber cable including a core having an optical fiber, an inner sheath covering the core, and an outer sheath covering the inner sheath. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-72801 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, the inner sheath and the outer sheath may shrink in the longitudinal direction of the optical fiber cable due to the influence of the external environment. Here, for example, if the linear expansion coefficient of the inner sheath differs from the linear expansion coefficient of the outer sheath, the amount of shrinkage of the inner sheath and the amount of shrinkage of the outer sheath may differ when the temperature drops. Also, for example, if a tensile strength member is embedded in only one of the inner sheath and the outer sheath (see, for example, Patent Document 1), the amount of shrinkage of the two sheaths may also differ from each other. If the amount of shrinkage of the two sheaths differs from each other as in this case, residual stress may occur in the optical fiber cable, which may result in an increase in transmission loss.

[0005] In order to solve the above problem, it is conceivable to adopt a configuration in which the inner sheath and the outer sheath are integrated in the entire circumferential direction (entire circumference). However, in such a configuration, it becomes difficult to pull out the outer sheath from the optical fiber cable and leave the inner sheath and the optical fiber, which may reduce workability.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide an optical fiber cable that can simultaneously suppress transmission loss and improve the workability of lead-out work. [Means for solving the problem]

[0007] In order to solve the above problem, an optical fiber cable according to one embodiment of the present invention comprises a core having an optical fiber, a first protective layer covering the core, and a second protective layer covering the first protective layer, and the outer surface of the first protective layer is provided with at least one integrated region fixed to or pressed against the second protective layer, and at least one non-integrated region that is not fixed to or pressed against the second protective layer. [Effects of the Invention]

[0008] According to the above aspect of the present invention, an optical fiber cable can be provided that can achieve both reduced transmission loss and improved workability in lead-out work. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing an optical fiber cable according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a cross-sectional view showing an optical fiber cable according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a perspective view showing an optical fiber cable according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) An optical fiber cable 1 according to a first embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the optical fiber cable 1 includes a core 10, a first protective layer 20, a pair of ripcords 40, a second protective layer 50, and a plurality of (four in the illustrated example) tensile strength members 60.

[0011] The core 10 according to this embodiment has a plurality of optical fiber units U. Each optical fiber unit U includes a plurality of optical fibers 11 and a bundling material 12 that bundles the plurality of optical fibers 11. In other words, inside the core 10, the plurality of optical fibers 11 constitute an optical fiber unit U. The core 10 may have a holding winding tape (not shown) that covers the plurality of optical fiber units U. Note that the plurality of optical fibers 11 do not have to constitute an optical fiber unit U.

[0012] (direction definition) In this embodiment, the direction parallel to the central axis O of the core 10 is referred to as the axial direction or longitudinal direction. A cross section perpendicular to the longitudinal direction is referred to as a transverse section. In the transverse section, the direction perpendicular to the central axis O is referred to as the radial direction. The direction approaching the central axis O along the radial direction is referred to as the radially inner direction. The direction moving away from the central axis O along the radial direction is referred to as the radially outer direction. When viewed from the axial direction, the direction going around the central axis O is referred to as the circumferential direction.

[0013] The optical fiber 11 may be an optical fiber core, an optical fiber bare wire, an optical fiber ribbon, or the like. As a type of optical fiber ribbon, the plurality of optical fibers 11 may form a so-called intermittently fixed ribbon. In an intermittently fixed ribbon, the plurality of optical fibers 11 are bonded to one another so that they spread out in a mesh-like (spider web-like) shape when pulled in a direction perpendicular to the extending direction. More specifically, one optical fiber 11 is bonded to the optical fibers 11 on both sides thereof at different positions in the extending direction. The adjacent optical fibers 11 are bonded to one another at a fixed interval in the extending direction. The form of the optical fibers 11 included in the core 10 is not limited to an intermittently fixed ribbon and may be changed as appropriate. The number of optical fibers 11 included in the core 10 may be changed as appropriate, as long as it is one or more.

[0014] The first protective layer 20 is also referred to as an inner sheath (internal sheath). The first protective layer 20 has a cylindrical shape and covers the core 10 from the radially outer side. The first protective layer 20 can be made of a polyolefin (PO) resin such as polyethylene (PE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), or ethylene-propylene copolymer (EP), or polyvinyl chloride (PVC). The first protective layer 20 may also be formed using a blend (alloy, mixture) of the above resins. Depending on the purpose, various additives may be added to the first protective layer 20. Examples of the additives include flame retardants, colorants, anti-degradants, and inorganic fillers.

[0015] The second protective layer 50 according to this embodiment includes a reinforcing member 51 and a sheath 52. The sheath 52 is located radially outward of the reinforcing member 51.

[0016] The sheath 52 is also referred to as an outer sheath (external sheath). The sheath 52 has a cylindrical shape and covers the reinforcing member 51 from the radially outer side. The sheath 52 can be made of a polyolefin (PO) resin such as polyethylene (PE), polypropylene (PP), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), or ethylene-propylene copolymer (EP), or polyvinyl chloride (PVC). The sheath 52 may also be made of a mixture (alloy or mixture) of the above resins. Depending on the purpose, various additives may be added to the sheath 52. Examples of the additives include a flame retardant, a colorant, an anti-degradant, and an inorganic filler. The material of the first protective layer 20 and the material of the sheath 52 may be the same or different.

[0017] The reinforcing member 51 according to this embodiment has a cylindrical shape and faces the first protective layer 20 in the radial direction. The material that can be used to form the reinforcing member 51 is, for example, a metal tape. The metal tape can be made of, for example, iron, stainless steel, copper, copper alloy, or the like. Alternatively, the reinforcing member 51 may be a tape containing glass fiber or a tape containing fiber reinforced plastic (FRP). The reinforcing member 51 serves to protect the optical fiber 11 from bites by animals such as squirrels and woodpeckers, and from hunting bullets, etc.

[0018] The reinforcing member 51 and the sheath 52 are fixed to each other. The manner of fixing is not particularly limited, but for example, when the sheath 52 is made of resin, the sheath 52 can be fixed to the reinforcing member 51 by thermal fusion. In this case, a resin layer may be provided on the outer peripheral surface of the reinforcing member 51 to more reliably fusion-fix the reinforcing member 51 and the sheath 52.

[0019] The outer peripheral surface 20s of the first protective layer 20 includes an integrated region 20a and a non-integrated region 20b. The integrated region 20a is a portion of the outer peripheral surface 20s of the first protective layer 20 that is fused and fixed to the inner peripheral surface of the second protective layer 50 (reinforcing member 51). The non-integrated region 20b is a portion of the outer peripheral surface 20s of the first protective layer 20 that is not fused and fixed to the inner peripheral surface of the second protective layer 50 (reinforcing member 51).

[0020] In this embodiment, the holding winding tape 30 is disposed between the first protective layer 20 and the second protective layer 50 in the radial direction. The holding winding tape 30 according to this embodiment has water absorbency. For example, a nonwoven fabric or a polyester tape can be used as the holding winding tape 30. The holding winding tape 30 extends in the longitudinal direction. More specifically, the holding winding tape 30 may extend linearly along the longitudinal direction. Alternatively, the holding winding tape 30 may be wound around the first protective layer 20 in a spiral or SZ shape.

[0021] The holding winding tape 30 according to this embodiment is curved along the outer peripheral surface 20s of the first protective layer 20 in a cross-sectional view, and has a C-shape. In other words, the holding winding tape 30 does not extend over the entire circumferential direction (entire circumference) of the outer peripheral surface 20s of the first protective layer 20. In yet other words, the holding winding tape 30 covers only a portion of the circumferential direction of the outer peripheral surface 20s of the first protective layer 20. Of the outer peripheral surface 20s of the first protective layer 20, the portion covered by the holding winding tape 30 is the non-integrated region 20b described above, and the portion not covered by the holding winding tape 30 is the integrated region 20a described above.

[0022] This structure can be achieved by extrusion-molding the first protective layer 20 and the sheath 52 with the holding winding tape 30 and the reinforcing member 51 attached longitudinally. More specifically, a holding winding tape 30 having a width (circumferential dimension) smaller than the outer periphery of the first protective layer 20 (circumferential dimension of the outer peripheral surface 20s) is prepared. By extrusion-molding using the holding winding tape 30, the heated and melted first protective layer 20 is fused and fixed to the reinforcing member 51 of the second protective layer 50 in the portion where the holding winding tape 30 is not present (integrated region 20a). On the other hand, in the portion where the holding winding tape 30 is present (non-integrated region 20b), contact and fusion between the first protective layer 20 and the reinforcing member 51 are suppressed. This is because the melting point and softening point of the holding winding tape 30 are sufficiently higher than the temperature of the sheath 52 during extrusion-molding, and the adhesiveness (surface energy) of the surface of the holding winding tape 30 is sufficiently low. In order to more reliably fuse and fix the first protective layer 20 and the reinforcing member 51 in the integrated region 20a, a resin layer may be provided on the inner peripheral surface of the reinforcing member 51. In addition, in order to more reliably fuse and fix the first protective layer 20 and the reinforcing member 51 in the integrated region 20a, the thickness (diameter dimension) of the holding wrapping tape 30 and the curvature of the outer peripheral surface 20s of the first protective layer 20 may be designed appropriately.

[0023] Even when the width of the holding winding tape 30 is equal to or greater than the outer periphery of the first protective layer 20, the same effect as above can be obtained by extrusion molding the holding winding tape 30 in a state where it is circumferentially wrinkled (compressed) or folded. That is, the first protective layer 20 can be fusion-bonded to the reinforcing member 51 in the integrated region 20a. In this case, the holding winding tape 30 may be wrinkled or folded over the entire length of the optical fiber cable 1 in the longitudinal direction. Alternatively, the holding winding tape 30 may be wrinkled or folded intermittently in the longitudinal direction.

[0024] The ripcord 40 according to this embodiment is disposed radially between the holding winding tape 30 and the reinforcing member 51. The pair of ripcords 40 according to this embodiment are disposed radially with the core 10 positioned therebetween. The ripcord 40 is a member used to tear the sheath 52. The ripcord 40 may be made of, for example, a synthetic fiber (such as polyester) thread or a cylindrical rod made of polypropylene (PP) or nylon.

[0025] The four strength members 60 according to this embodiment are embedded in the sheath 52 of the second protective layer 50. Each strength member 60 extends linearly along the longitudinal direction. When tension is applied to the optical fiber cable 1 along the longitudinal direction, the strength members 60 protect the optical fiber 11 by receiving the tension. The strength members 60 also suppress the contraction of the sheath 52 when the temperature drops. Examples of materials that can be used for the strength members 60 include metal wires (such as steel wires), bundled metal wires, glass fibers, and bundled glass fibers. Alternatively, fiber-reinforced plastics (FRP) and the like may be used for the strength members 60. The four strength members 60 according to this embodiment are arranged radially so that the core 10 is positioned between them. More specifically, the four strength members 60 according to this embodiment form two groups G1 and G2. Each group G1 and G2 includes two strength members 60. The two groups G1 and G2 are arranged so that the core 10 is located between them in the radial direction. The number of reinforcing members 60 may be three or less or five or more. The reinforcing members 60 may also form three or more groups. The number of reinforcing members 60 included in each group can be changed as appropriate. Alternatively, the reinforcing members 60 do not need to form groups.

[0026] In the illustrated example, the strength members 60 are not embedded in the first protective layer 20. However, a configuration may be adopted in which the strength members 60 are embedded in the first protective layer 20 but not in the second protective layer 50. In other words, in this embodiment, the strength members 60 are embedded in only one of the first protective layer 20 and the second protective layer 50.

[0027] Next, the operation of the optical fiber cable 1 configured as above will be described.

[0028] Conventionally, optical fiber cables having an inner sheath and an outer sheath are known. Generally, when the temperature of an optical fiber cable drops, the inner sheath and the outer sheath shrink in the longitudinal direction. For example, if a strength member is embedded only in the outer sheath, the strength member suppresses the shrinkage of the outer sheath, while the strength member does not suppress the shrinkage of the inner sheath. This can result in different amounts of shrinkage between the inner sheath and the outer sheath. If the shrinkage amounts of the inner sheath and the outer sheath differ, residual stress may occur within the optical fiber cable, resulting in increased transmission loss.

[0029] In contrast, in the optical fiber cable 1 according to this embodiment, the first protective layer 20 and the second protective layer 50 are fusion-bonded in the integrated region 20a. This prevents the first protective layer 20 and the second protective layer 50 from shrinking independently when the temperature drops. This reduces the difference between the amount of shrinkage of the first protective layer 20 and the amount of shrinkage of the second protective layer 50, thereby suppressing residual stress inside the optical fiber cable 1. In other words, the transmission loss of the optical fiber cable 1 can be suppressed.

[0030] Furthermore, in the optical fiber cable 1 according to this embodiment, a non-integrated region 20b is provided on the outer peripheral surface 20s of the first protective layer 20. That is, the integrated region 20a does not extend over the entire outer peripheral surface 20s of the first protective layer 20. This configuration makes it easier to pull out the second protective layer 50 from the optical fiber cable 1 and leave the first protective layer 20 and the core 10, compared to when the entire outer peripheral surface 20s of the first protective layer 20 is the integrated region 20a, for example.

[0031] As described above, the optical fiber cable 1 of this embodiment comprises a core 10 having an optical fiber 11, a first protective layer 20 covering the optical fiber 11, and a second protective layer 50 covering the first protective layer 20, and the outer surface 20s of the first protective layer 20 is provided with an integrated region 20a fixed to the second protective layer 50 and a non-integrated region 20b not fixed to the second protective layer 50.

[0032] This configuration reduces the difference between the amount of shrinkage of the first protective layer 20 and the amount of shrinkage of the second protective layer 50 when the temperature drops, thereby suppressing transmission loss in the optical fiber cable 1. Furthermore, compared to a case where the entire outer peripheral surface 20s of the first protective layer 20 is the integrated region 20a, for example, the optical fiber cable 1 can be easily led out. In other words, it is possible to achieve both suppression of transmission loss and improved workability in the lead-out operation.

[0033] The second protective layer 50 also includes a reinforcing member 51 facing the outer peripheral surface 20s of the first protective layer 20, and a sheath 52 covering the reinforcing member 51 and fixed to the reinforcing member 51, and the integrated region 20a is fixed to the reinforcing member 51. With this configuration, the optical fiber 11 can be more securely protected by using the reinforcing member 51.

[0034] Furthermore, the integrated region 20a is fused and fixed to the second protective layer 50. With this configuration, the integrated region 20a can be easily fixed to the second protective layer 50 by, for example, extrusion molding.

[0035] The optical fiber cable 1 also includes a strength member 60 embedded in only one of the first protective layer 20 and the second protective layer 50. This configuration allows the outer diameter of the optical fiber cable 1 to be smaller than when, for example, the strength members 60 are embedded in both the first protective layer 20 and the second protective layer 50. Furthermore, because the integrated region 20a is provided on the outer peripheral surface 20s of the first protective layer 20, even if the strength members 60 are embedded in only one of the protective layers 20, 50, the difference in the amount of shrinkage between the protective layers 20, 50 when the temperature drops can be reduced.

[0036] The optical fiber cable 1 further includes a holding winding tape 30 located between the first protective layer 20 and the second protective layer 50 and covering a portion of the first protective layer 20, and the portion of the outer peripheral surface 20s of the first protective layer 20 that is covered with the holding winding tape 30 is the non-integrated region 20b. With this configuration, for example, by extrusion molding the first protective layer 20 and the second protective layer 50 with the holding winding tape 30 attached longitudinally, the integrated region 20a and the non-integrated region 20b can be easily provided on the outer peripheral surface 20s of the first protective layer 20.

[0037] The holding winding tape 30 has a C-shape in a cross section perpendicular to the central axis O of the core 10. With this configuration, the integrated region 20a and the non-integrated region 20b can be easily provided on the outer peripheral surface 20s of the first protective layer 20.

[0038] In addition, the holding winding tape 30 has water absorbency. With this configuration, water leakage inside the optical fiber cable 1 can be suppressed.

[0039] (Second embodiment) Next, a second embodiment will be described, but the basic configuration is similar to that of the first embodiment. Therefore, the same components are given the same reference numerals, and the description thereof will be omitted, and only the differences will be described.

[0040] As shown in FIG. 2 , the optical fiber cable 2 according to this embodiment includes a plurality of holding winding tapes 30 spaced apart in the circumferential direction. As a result, a plurality of integrated regions 20a and a plurality of non-integrated regions 20b are provided on the outer peripheral surface 20s of the first protective layer 20. The integrated regions 20a are spaced apart in the circumferential direction. The non-integrated regions 20b are spaced apart in the circumferential direction. This structure can be achieved, for example, by extrusion molding the first protective layer 20 and the sheath 52 with a reinforcing member 51 and a plurality of holding winding tapes 30 attached longitudinally. In this case, the width of each holding winding tape 30 may be adjusted depending on the number and size of the desired integrated regions 20a and non-integrated regions 20b. Furthermore, as described in the first embodiment, the holding winding tape 30 may be wrinkled or folded in the circumferential direction.

[0041] As described above, in the optical fiber cable 2 according to this embodiment, similar to the optical fiber cable 1 according to the first embodiment, the integrated region 20a and the non-integrated region 20b are provided on the outer peripheral surface 20s of the first protective layer 20. Therefore, it is possible to achieve both suppression of transmission loss and improvement of workability in the lead-out operation.

[0042] Furthermore, the multiple holding winding tapes 30 (non-integrated regions 20b) are arranged at intervals in the circumferential direction. Therefore, even if the width of each holding winding tape 30 (non-integrated regions 20b) is reduced, the holding winding tape 30 can easily absorb water from the entire optical fiber cable 2. Therefore, it is easier to prevent water from running inside the optical fiber cable 2.

[0043] (Third embodiment) Next, a third embodiment will be described, but the basic configuration is similar to that of the first embodiment. Therefore, the same components are given the same reference numerals, and the description thereof will be omitted, and only the differences will be described.

[0044] As shown in FIG. 3 , in the optical fiber cable 3 according to this embodiment, there is a cross section in which the holding winding tape 30 extends over the entire circumferential direction (entire circumference) of the first protective layer 20. In other words, there is a cross section in which the integrated region 20a does not exist on the outer peripheral surface 20s of the first protective layer 20. Furthermore, the holding winding tape 30 has holes 31 formed therethrough in the radial direction. In the illustrated example, the holding winding tape 30 has a plurality of holes 31 formed therethrough that are intermittently arranged in the longitudinal and circumferential directions. However, the number and positions of the holes 31 can be changed as appropriate. In the optical fiber cable 3 according to this embodiment, the portions of the outer peripheral surface 20s of the first protective layer 20 that overlap with the holes 31 in the radial direction are integrated regions 20a, and the portions that do not overlap with the holes 31 are non-integrated regions 20b.

[0045] As described above, in the optical fiber cable 3 according to this embodiment, similar to the optical fiber cable 1 according to the first embodiment, the integrated region 20a and the non-integrated region 20b are provided on the outer peripheral surface 20s of the first protective layer 20. Therefore, it is possible to achieve both suppression of transmission loss and improvement of workability in lead-out work.

[0046] Furthermore, the holding winding tape 30 has holes 31 formed therein that penetrate the holding winding tape 30 in the radial direction. With this configuration, the integrated region 20a and the non-integrated region 20b can be easily provided on the outer peripheral surface 20s of the first protective layer 20. [Example]

[0047] The above embodiment will be described below using specific examples. More specifically, a preferred range of the ratio r of the integrated region 20a to the outer peripheral surface 20s of the first protective layer 20 will be described. Note that the present invention is not limited to the following examples.

[0048] (Comparative Example) In the optical fiber cables according to Comparative Examples 1 and 2, the core 10 included 12 optical fiber units U. Each optical fiber unit U included six intermittently fixed ribbons. Each intermittently fixed ribbon included 12 optical fibers 11. In other words, the core 10 had a total of 864 optical fibers 11. In the optical fiber cables according to Comparative Examples, the first protective layer 20 was completely covered with the holding winding tape 30. In other words, the ratio r of the integrated region 20a to the outer peripheral surface 20s of the first protective layer 20 was 0%. In the optical fiber cable according to Comparative Example 2, the outer peripheral surface 20s of the first protective layer 20 was not covered with the holding winding tape 30. In other words, the ratio r of the integrated region 20a to the outer peripheral surface 20s of the first protective layer 20 was 100%.

[0049] (Example) The optical fiber cable according to Example 1 was the optical fiber cable 1 according to the first embodiment. The optical fiber cable according to Example 2 was the optical fiber cable 2 according to the second embodiment. The optical fiber cable according to Example 3 was the optical fiber cable 3 according to the third embodiment. The optical fiber cables according to Examples 1 to 3 had cores that were considered to be identical to the cores of the optical fiber cable according to the comparative example. The only difference between Examples 1 to 3 and the comparative example was the arrangement of the holding winding tape 30, i.e., the arrangement of the integrated region 20a and the non-integrated region 20b. In Example 1, multiple optical fiber cables were prepared in which the ratio r of the integrated region 20a to the outer circumferential surface 20s of the first protective layer 20 was varied by changing the width of the holding winding tape 30. In Example 2, multiple optical fiber cables were prepared in which the ratio r was varied by changing the width and number of the holding winding tape 30. In Example 3, multiple optical fiber cables were prepared in which the ratio r was varied by changing the size and number of holes 31 formed in the holding winding tape 30. More specifically, the ratio r is defined as the ratio of the area of ​​the integrated region 20a to the surface area of ​​the outer circumferential surface 20s of the first protective layer 20. Here, the ratio r in Examples 1 and 2 can also be defined as the ratio of the length (dimension in the circumferential direction) of the integrated region 20a to the length (dimension in the circumferential direction) of the outer periphery of the first protective layer 20 in a certain cross section.

[0050] A temperature cycle test and confirmation of the workability of leading out the optical fiber cables according to Examples 1 to 3 and Comparative Examples 1 and 2 were carried out. The results are shown in Tables 1 to 3. The temperature cycle test was conducted in accordance with ICEA S-87-640-2016, item 7.24. Specifically, a loss increase of 0.15 dB / km or less (measured at 1550 nm wavelength) after two cycles of -40°C / +70°C was considered good (OK), and a loss increase of more than 0.15 dB / km was considered bad (NG). When checking the ease of use of the lead-out work, if the lead-out work was difficult it was given a C, if the lead-out work was performed well it was given a B, and if the lead-out work was performed even better it was given an A.

[0051] [Table 1]

[0052] [Table 2]

[0053] [Table 3]

[0054] As shown in Tables 1 to 3, when the ratio r of the integrated region 20a was between 0% and 5%, the temperature cycle test resulted in NG. This is thought to be because the fixing strength between the first protective layer 20 and the second protective layer 50 was insufficient, causing the protective layers 20 and 50 to shrink differently, resulting in residual stress inside the optical fiber cable. On the other hand, when the ratio r of the integrated region 20a was between 10% and 100%, the temperature cycle test resulted in OK.

[0055] From the above results, it is preferable that the ratio r of the integrated region 20a to the outer peripheral surface 20s of the first protective layer 20 is 10% or more, which can effectively suppress the transmission loss of the optical fiber cable.

[0056] Furthermore, as shown in Tables 1 to 3, when the proportion r of the integrated region 20a was 100%, the confirmation result of the lead-out operability was C. This is thought to be because the first protective layer 20 and the second protective layer 50 were completely integrated, making it difficult to pull out only the second protective layer 50 from the optical fiber cable. On the other hand, when the proportion r of the integrated region 20a was 60% to 80%, the confirmation result of the lead-out operability was B, and when the proportion r was 0% to 50%, the confirmation result was A.

[0057] From the above results, the ratio r of the integrated region 20a to the outer peripheral surface 20s of the first protective layer 20 is preferably 80% or less, and more preferably 50% or less, which can reliably ensure ease of opening work.

[0058] The inventors also conducted waterproofing tests on the optical fiber cables according to Examples 1 to 3. The waterproofing tests were conducted in accordance with IEC 60794-1-22 F5C. The optical fiber cables according to Examples 1 and 3 passed the test when the ratio r of the integrated region 20a to the outer peripheral surface 20s of the first protective layer 20 was 40% or less. The optical fiber cable according to Example 2 passed the test when the ratio r was 60% or less. The reason for the difference in results between Examples 1 and 3 and Example 2 is thought to be due to the difference in the arrangement of the holding winding tape 30 (non-integrated region 20b). That is, in Example 2, multiple holding winding tapes 30 are arranged at intervals in the circumferential direction. Therefore, even if each holding winding tape 30 has a short width and a large ratio r, it is thought that the holding winding tape 30 easily absorbs water from the entire optical fiber cable 2.

[0059] From the above results, it is preferable that the ratio r of the integrated region 20a to the outer peripheral surface 20s of the first protective layer 20 is 40% or less. This effectively suppresses water leakage inside the optical fiber cable. However, if the outer peripheral surface 20s of the first protective layer 20 has multiple non-integrated regions 20b spaced apart in the circumferential direction, water leakage can be effectively suppressed even if the ratio r is 60% or less.

[0060] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0061] For example, in the above embodiment, the integrated region 20a of the first protective layer 20 and the second protective layer 50 are fixed to each other by fusion, but the manner of fixing is not limited to fusion. For example, the first protective layer 20 and the second protective layer 50 may be fixed to each other by an adhesive.

[0062] Furthermore, the integrated region 20a and the second protective layer 50 do not necessarily need to be fixed together, and the integrated region 20a may be pressed against the second protective layer 50. In this case, a frictional force acts between the integrated region 20a and the second protective layer 50. When only one of the protective layers 20, 50 attempts to shrink, the frictional force acts to prevent the shrinkage of only one protective layer. Therefore, even in a configuration in which the integrated region 20a is pressed against the second protective layer 50, the difference in the amount of shrinkage between the protective layers 20, 50 can be reduced, as in the above embodiment, thereby suppressing the transmission loss of the optical fiber cables 1 to 3. Note that the optical fiber cables 1 to 3 may include, for example, a compression member that compresses (presses or crushes) the second protective layer 50 radially inward. Alternatively, the inner diameter of the second protective layer 50 may be smaller than the outer diameter of the first protective layer 20, thereby crushing the first protective layer 20 radially inward. These configurations allow the integrated region 20a to be more reliably pressed against the second protective layer 50. Furthermore, the coefficient of friction between the integrated region 20a and the second protective layer 50 may be increased by applying a surface treatment to the integrated region 20a or to the second protective layer 50. This configuration allows the frictional force acting between the integrated region 20a and the second protective layer 50 to be increased.

[0063] Furthermore, the second protective layer 50 does not have to include the reinforcing member 51. In this case, the integrated region 20a may be fixed to or pressed against the sheath 52.

[0064] Furthermore, the holding wrapping tape 30 does not need to have water absorbency.

[0065] Furthermore, the optical fiber cables 1 to 3 may not include the strength members 60. Even in conventional optical fiber cables that do not include the strength members, if the materials that make up the first protective layer and the second protective layer have different linear expansion coefficients, a problem occurs in that the amount of shrinkage differs between the two protective layers. By applying the configuration according to the above embodiment in which the integrated region 20a is present on the outer peripheral surface 20s of the first protective layer 20, this problem can be solved even in optical fiber cables 1 to 3 that do not include the strength members 60.

[0066] In addition, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and the above-described embodiments and variations may be combined as appropriate, without departing from the spirit of the present invention.

[0067] For example, the first embodiment and the third embodiment may be combined. That is, a configuration may be adopted in which the hole 31 is formed in the holding winding tape 30 having a C-shaped cross section. Similarly, the second embodiment and the third embodiment may be combined. That is, a configuration may be adopted in which the hole 31 is formed in a plurality of holding winding tapes 30. In this case, the hole 31 may be formed in all of the holding winding tapes 30. Alternatively, there may be a holding winding tape 30 in which the hole 31 is not formed. [Explanation of symbols]

[0068] 1 to 3... Optical fiber cable 10... Core 11... Optical fiber 20... First protective layer 20s... Outer surface 20a... Integrated region 20b... Non-integrated region 30... Pressing winding tape 31... Hole 50... Second protective layer 51... Reinforcing member 52... Sheath 60... Tensile member

Claims

1. a core having an optical fiber; a first protective layer covering the core; a second protective layer covering the first protective layer; at least one holding tape positioned between the first protective layer and the second protective layer and covering a portion of the first protective layer; an outer peripheral surface of the first protective layer is provided with at least one integrated region that is fixed to or pressure-welded to the second protective layer, and at least one non-integrated region that is not fixed to or pressure-welded to the second protective layer; a portion of the outer peripheral surface of the first protective layer that is covered by the holding winding tape is the non-integrated region; The optical fiber cable, wherein the holding and winding tape is a nonwoven fabric or a polyester tape.

2. the second protective layer includes a reinforcing member facing an outer peripheral surface of the first protective layer, and a sheath covering the reinforcing member and fixed to the reinforcing member, The optical fiber cable of claim 1 , wherein the integrated region is fixed or crimped to the strength member.

3. The optical fiber cable according to claim 1 or 2, wherein the integrated region is fusion-fixed to the second protective layer.

4. 3. The optical fiber cable according to claim 1, further comprising a strength member embedded in only one of the first protective layer and the second protective layer.

5. 3. The optical fiber cable according to claim 1, wherein a ratio of the integrated region to the outer peripheral surface of the first protective layer is 10% or more.

6. 3. The optical fiber cable according to claim 1, wherein a ratio of the integrated region to the outer peripheral surface of the first protective layer is 50% or less.

7. 3. The optical fiber cable according to claim 1, wherein the holding winding tape has a C-shape in a cross section perpendicular to the central axis of the core.

8. A core having an optical fiber; a first protective layer covering the core; a second protective layer covering the first protective layer; at least one holding tape positioned between the first protective layer and the second protective layer and covering a portion of the first protective layer; an outer peripheral surface of the first protective layer is provided with at least one integrated region that is fixed to or pressure-welded to the second protective layer, and at least one non-integrated region that is not fixed to or pressure-welded to the second protective layer; a portion of the outer peripheral surface of the first protective layer that is covered by the holding winding tape is the non-integrated region; The optical fiber cable has a hole formed in the holding and winding tape that passes through the holding and winding tape in the radial direction.

9. 3. The optical fiber cable according to claim 1, wherein the holding and winding tape has water-absorbing properties.

10. The optical fiber cable according to claim 9 , wherein a ratio of the integrated region to the outer peripheral surface of the first protective layer is 40% or less.

11. a plurality of non-integrated regions are provided on an outer peripheral surface of the first protective layer, the non-integrated regions being spaced apart in a circumferential direction; The optical fiber cable according to claim 9 , wherein a ratio of the integrated region to the outer peripheral surface of the first protective layer is 60% or less.

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