How to lay optical fiber cables

Abstract

To provide a fiber optic cable installation method capable of improving efficiency of fiber optic cable installation work while achieving both high flame retardancy and good insertion characteristics.SOLUTION: A fiber optic cable installation method is a method of a fiber optic cable that includes: a cable core including multiple optical fiber cores; a cable jacket including an inner layer and an outer layer arranged radially outwardly; and a tensile strength body embedded in the outer layer, in which a coefficient of kinetic friction of the outer layer against the duct is smaller than that of the inner layer, and the inner layer has more flame retardancy than the outer layer. The fiber optic cable installation method includes: a step of wiring the fiber optic cable outdoors via a duct; a step of bringing the fiber optic cable indoors from outdoors; a step of removing the outer layer after bringing the fiber optic cable indoors to use a part of the fiber optic cable into a fiber optic cable for indoor wiring; and a step of wiring the fiber optic cable indoors.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a method for installing an optical fiber cable. [Background technology]

[0002] US Patent No. 5,949,949 discloses an optical fiber cable including an optical fiber ribbon within a pipe, in which at least two optical fibers included in the ribbon are intermittently spliced ​​along the length of the fiber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2015-517679 Summary of the Invention [Problem to be solved by the invention]

[0004] When laying optical fiber cables in a building, an optical fiber cable pulled in from outdoors is connected to another optical fiber cable installed indoors, for example, by fusion splicing. In recent years, with the increase in the amount of information to be transmitted, multi-core optical fiber cables containing multiple optical fiber cores have appeared. When laying such multi-core optical fiber cables containing multiple optical fiber cores, the splicing work, such as fusion splicing, can result in a significant workload. Therefore, there is a need to reduce this workload.

[0005] Furthermore, for optical fiber cables (microduct cables) that are laid by air pumping through ducts, a low-friction cable jacket is desirable because it allows for longer pumping distances. On the other hand, there is an increasing demand for flame retardancy for optical fiber cables laid indoors. If insertion performance is a priority, the cable jacket needs to have low friction, but if the cable jacket is made from a resin material that provides low friction, the flame retardancy of the cable jacket generally decreases. For this reason, it can be difficult to achieve both high flame retardancy and good insertion performance.

[0006] The present disclosure aims to provide an optical fiber cable laying method that can improve the efficiency of optical fiber cable laying work while achieving both high flame retardancy and good insertion characteristics. [Means for solving the problem]

[0007] In order to achieve the above object, a method for laying an optical fiber cable according to one aspect of the present invention comprises: a cable core including a plurality of optical fiber cores; a cable jacket including an inner layer disposed radially outward of the cable core and an outer layer disposed radially outward of the inner layer; and at least one tensile strength member embedded in the outer layer, The plurality of optical fiber core wires is 288 cores or more, The outer layer has a plurality of protrusions formed thereon, a dynamic friction coefficient of the outer layer relative to the duct is smaller than a dynamic friction coefficient of the inner layer relative to the duct; the inner layer being more flame retardant than the outer layer; The optical fiber cable is passed through the duct. By air pressure a step of wiring outdoors; Pulling the optical fiber cable from the outdoors to the indoors; removing the outer layer after pulling the optical fiber cable indoors, thereby forming a portion of the optical fiber cable into an optical fiber cable for indoor wiring; and wiring the optical fiber cable for indoor wiring indoors. fruit, When the optical fiber cable is laid outdoors, only the protrusion comes into contact with the duct. . [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide an optical fiber cable laying method that can improve the efficiency of optical fiber cable laying work while achieving both high flame retardancy and good insertion characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an optical fiber cable with a traction tool according to one aspect of the present embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 3 is a plan view showing an intermittently connected optical fiber ribbon in the longitudinal direction. [Figure 4] FIG. 4 is a diagram illustrating an example of laying an optical fiber cable. [Figure 5] FIG. 5 is a flowchart illustrating a method for laying an optical fiber cable according to one aspect of the present embodiment. [Figure 6] FIG. 6 is a cross-sectional view of an optical fiber cable for indoor wiring. [Figure 7] FIG. 7 is a diagram illustrating a measurement device for measuring the dynamic friction coefficient of an optical fiber cable according to one aspect of this embodiment. [Figure 8] FIG. 8 is a diagram illustrating a pressure-feeding device for performing pressure-feeding evaluation of an optical fiber cable. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. (1) a cable core including a plurality of optical fiber cores; a cable jacket including an inner layer disposed radially outward of the cable core and an outer layer disposed radially outward of the inner layer; and at least one tensile strength member embedded in the outer layer, The plurality of optical fiber core wires is 288 cores or more, The outer layer has a plurality of protrusions formed thereon, a dynamic friction coefficient of the outer layer relative to the duct is smaller than a dynamic friction coefficient of the inner layer relative to the duct; the inner layer being more flame retardant than the outer layer; The optical fiber cable is passed through the duct. By air pressure a step of wiring outdoors; Pulling the optical fiber cable from the outdoors to the indoors; removing the outer layer after pulling the optical fiber cable indoors, thereby forming a portion of the optical fiber cable into an optical fiber cable for indoor wiring; and wiring the optical fiber cable for indoor wiring indoors. fruit, When the optical fiber cable is laid outdoors, only the protrusion comes into contact with the duct. , a method for laying optical fiber cables. According to this configuration, after the optical fiber cable is pulled from outdoors to indoors, the outer layer of the optical fiber cable is removed, thereby converting a portion of the optical fiber cable into an optical fiber cable for indoor wiring. In other words, when the optical fiber cable is routed outdoors through a duct, it has a low-friction outer layer including a tensile strength member, which provides good insertion properties. On the other hand, the outer layer of the cable jacket is removed after the optical fiber cable is pulled indoors, so the portion of the optical fiber cable up to the inner layer is converted into an optical fiber cable for indoor wiring, and then routed indoors. In other words, when routing indoors, the low-flame-retardant outer layer is removed, and the high-flame-retardant inner layer becomes the outermost layer of the cable jacket. Therefore, the optical fiber cable laying method according to the above configuration enables efficient laying of an optical fiber cable while achieving both high flame retardancy and good insertion properties.

[0011] (2) The optical fiber cable laying method according to item (1), wherein in the step of laying the optical fiber cable outdoors, the optical fiber cable is passed through the duct by air pressure feeding. According to this configuration, the optical fiber cable is passed through the duct by air pressure feeding, so that the optical fiber cable can be laid efficiently.

[0012] (3) Connectors are connected to the ends of the optical fiber core wires, storing the optical fiber cable for indoor wiring in the junction box installed indoors; The method for laying an optical fiber cable according to item (1) or (2), further comprising the step of connecting the connector and another optical fiber core in the connection box. According to this configuration, in a splice box installed indoors, a connector connected to an end of an optical fiber core wire pulled from outdoors is connected to another optical fiber core wire. Therefore, according to the optical fiber cable laying method of the above configuration, an optical fiber core wire pulled indoors from outdoors can be connected to another optical fiber core wire without fusion splicing.

[0013] [Details of the embodiments of the present disclosure] Specific examples of optical fiber cables with traction tools according to embodiments of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0014] An optical fiber cable 100 with a traction tool according to this embodiment will be described with reference to Figures 1 and 2. In the description of this embodiment, for the sake of convenience, the "front-rear direction" and "left-right direction" will be referred to as appropriate. These directions are relative directions set for the optical fiber cable 100 with a traction tool exemplified in Figure 1. Here, the "front-rear direction" refers to a direction that includes the "forward direction" and "rear direction" with respect to the figure. The "left-right direction" refers to a direction that includes the "left direction" and "right direction" with respect to the figure.

[0015] Fig. 1 is a diagram illustrating an optical fiber cable 100 with a pulling tool. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. As illustrated in Fig. 1, the optical fiber cable 100 with a pulling tool includes an optical fiber cable 10 and a pulling tool 20. The optical fiber cable 10 includes a cable main body 1, a plurality of connectors 2, and a pitch changer 3. The pulling tool 20 includes a protective tube 21 and a pulling eye 22.

[0016] The outer diameter of the optical fiber cable 10 is, for example, approximately 8 mm or more and 20 mm or less. The outer diameter of the optical fiber cable 10 according to this embodiment is approximately 20 mm. As illustrated in Fig. 2 , the optical fiber cable 10 includes a cable core 4, a holding and wrapping tape 5, a cable jacket 6, a tensile strength member 7, and a tear cord (fibrous inclusion) 8. The cable core 4, the holding and wrapping tape 5, the cable jacket 6, the tensile strength member 7, and the tear cord 8 are included in the cable main body 1.

[0017] The cable core 4 accommodates, for example, 12 subunits 41. Each subunit 41 includes, for example, two optical fiber ribbons 411. That is, the cable core 4 accommodates, for example, 24 optical fiber ribbons 411. However, the number of subunits 41 and the number of optical fiber ribbons 411 accommodated in the cable core 4 are not limited to this example.

[0018] Here, the optical fiber ribbon 411 will be described in detail with reference to Fig. 3. As illustrated in Fig. 3, the optical fiber ribbon 411 is an intermittently connected optical fiber ribbon in which a plurality of optical fibers 411A-411L are arranged in parallel in a direction perpendicular to the longitudinal direction thereof, and in which, among some or all of the optical fibers 411A-411L, connected portions 413 where adjacent optical fibers are connected and non-connected portions 414 where adjacent optical fibers are not connected are intermittently provided in the longitudinal direction. In this embodiment, the optical fiber ribbon 411 includes 12 optical fibers (optical fibers 411A-411L). Therefore, the cable core 4 contains 288 optical fibers. The outer diameter of each of the optical fibers 411A-411L is, for example, 180 µm or 200 µm. The ultraviolet curing resin coating the glass of each of the optical fibers 411A-411L may be flame-retardant. Specifically, a flame retardant, which will be described later, may be mixed into the ultraviolet curable resin.

[0019] The connecting portions 413 in the optical fiber ribbon 411 are formed by applying a connecting resin 415 made of, for example, an ultraviolet-curable resin, a thermosetting resin, or the like between the optical fibers. By applying the connecting resin 415 between predetermined spaces between the optical fibers, the connecting portions 413 and the non-connecting portions 414 are intermittently provided, and the optical fibers 411A-411L are integrated in a parallel state. The connecting resin 415 may be applied to only one side of the parallel surfaces formed by the parallel optical fibers 411A-411L, or may be applied to both sides. Furthermore, the optical fiber ribbon 411 may be fabricated, for example, by applying a ribbon resin to one or both sides of the parallel optical fibers 411A-411L to connect all the parallel optical fibers 411A-411L, and then cutting a portion with a rotary blade or the like to form the non-connecting portions 414.

[0020] Returning to FIG. 2 , the pressure wrapping tape 5 will be described. The pressure wrapping tape 5 may be, for example, a tape formed by bonding a substrate such as PET to a nonwoven fabric. The substrate and nonwoven fabric may be coated with, for example, a flame retardant. From the viewpoint of reducing environmental impact, the flame retardant is preferably a non-halogen flame retardant such as a metal hydroxide, a nitrogen-based flame retardant, or a phosphorus-based flame retardant. However, the flame retardant may also be a halogen-based flame retardant such as a bromine-based flame retardant or a chlorine-based flame retardant. The thickness of the pressure wrapping tape 5 is, for example, 0.13 mm or more and 0.15 mm or less. A water-absorbing agent (e.g., water-absorbing powder) may be applied to the inside of the pressure wrapping tape 5. The pressure wrapping tape 5 may be formed, for example, from a water-absorbing tape. The water-absorbing tape is made water-absorbent by, for example, adhering water-absorbing powder to a base fabric such as polyester.

[0021] The cable jacket 6 is formed by extrusion molding a resin around the cable core 4 around which the pressure wrapping tape 5 is wound. The thickness T1 of the cable jacket 6 (the thickness of the portion of the cable jacket 6 on which the protruding portion 63, which will be described later, is not formed) is, for example, 2.5 mm. The cable jacket 6 includes an inner layer 61 disposed radially outward from the cable core 4 and an outer layer 62 disposed radially outward from the inner layer 61. In other words, the cable jacket 6 has a two-layer structure.

[0022] The inner layer 61 is formed from a resin material such as vinyl chloride resin or polyolefin resin. In this embodiment, the inner layer 61 may be added with a flame retardant similar to the flame retardant applied to the press wrapping tape 5. Therefore, the inner layer 61 has high flame retardancy. Note that polyolefin resins have a relatively low oxygen index, so when the inner layer 61 is formed from a polyolefin resin, it is preferable to add a flame retardant to the inner layer 61. The oxygen index of the inner layer 61 is, for example, 40 or more. The dynamic friction coefficient of the inner layer 61 with respect to a metal plate (for example, the first metal plate 201 and the second metal plate 202 illustrated in FIG. 4) is, for example, 0.7 or less.

[0023] The outer layer 62 is formed from a vinyl chloride resin, a halogen-free resin, or the like. In this embodiment, the outer layer 62 is formed from a halogen-free resin. Examples of the halogen-free resin include cross-linked polyethylene, polypropylene, polybutylene terephthalate, urethane, and nylon. When the outer layer 62 is formed from a highly flame-retardant polyolefin (an example of a halogen-free resin), the flame retardancy of the outer layer 62 can be improved. The oxygen index of the outer layer 62 is, for example, 38. In this embodiment, the oxygen index of the outer layer 62 is lower than that of the inner layer 61. In other words, the oxygen index of the inner layer 61 is higher than that of the outer layer 62. Therefore, the inner layer 61 has higher flame retardancy than the outer layer 62.

[0024] The outer layer 62 may contain, for example, a silicon-based lubricant such as silicone or siloxane. In this case, the outer layer 62 has low friction. The dynamic friction coefficient of the outer layer 62 with respect to a metal plate (e.g., the first metal plate 201 and the second metal plate 202 illustrated in FIG. 4) is smaller than the dynamic friction coefficient of the inner layer 61 with respect to a metal plate. The dynamic friction coefficient of the outer layer 62 with respect to a metal plate is, for example, 0.5 or less. A plurality of strength members 7 are embedded within the outer layer 62 at equal intervals, i.e., at equal intervals. However, the intervals between the strength members 7 do not have to be equal. In this embodiment, eight strength members 7 are embedded within the outer layer 62. However, the number of strength members 7 embedded within the outer layer 62 is not limited to eight.

[0025] The outer layer 62 has a plurality of protrusions 63. In this embodiment, the outer layer 62 has eight protrusions 63. However, the number of protrusions 63 that the outer layer 62 has is not limited to eight. The protrusions 63 are convex portions formed in an arc shape. The protrusions 63 may be provided in a position of the outer layer 62 close to the position where the strength member 7 is embedded. The protrusions 63 are provided outside the strength member 7 and protrude outward from the optical fiber cable 10.

[0026] The diameter of the reinforcing member 7 is, for example, 0.5 mm. The reinforcing member 7 is formed of fiber reinforced plastic (FRP), such as aramid FRP, glass FRP, or carbon FRP. However, the reinforcing member 7 may also be formed of a liquid crystal polymer. It is preferable that the reinforcing member 7 be non-inductive. Note that fiber reinforced plastic (FRP) is generally a flammable material. From the perspective of improving the flame retardancy of the entire optical fiber cable 10, it is preferable that the reinforcing member 7 be positioned within the outer layer 62, closer to the center of the optical fiber cable 10, rather than near the surface of the outer layer 62.

[0027] The tear cord 8 is provided to tear the outer layer 62 of the cable jacket 6. The tear cord 8 is linearly arranged within the outer layer 62 in the longitudinal direction of the optical fiber cable 10, along the twisted optical fiber ribbons 411. In this embodiment, two tear cords 8 are provided. The two tear cords 8 are arranged so as to face each other in a cross-sectional view of the cable. By pulling out the tear cord 8, an operator can tear the outer layer 62 in the longitudinal direction and remove the optical fiber ribbons 411. The tear cord 8 is fibrous and is formed, for example, from a tensile-resistant plastic material (e.g., polyester).

[0028] Returning to FIG. 1, the connector 2 will be described. The connector 2 is, for example, a small 96-core connector. However, the connector 2 is not limited to a 96-core connector. Connectors with different core counts (for example, a 24-core connector, a 192-core connector, etc.) may also be combined and used. The optical fiber cable 10 includes, for example, three 96-core connectors. The connector 2 is housed in a protective tube 21. The connector 2 is connected to an end of an optical fiber ribbon 411 (see FIG. 3).

[0029] The pitch conversion unit 3 is provided between an end of the optical fiber ribbon 411 and an end of the connector 2. The pitch conversion unit 3 is configured to convert the pitch of the optical fibers 411A-411L. In this embodiment, the pitch of the optical fibers 411A-411L in the optical fiber ribbon 411 is 200 μm, and the arrangement pitch in the connector 2 is 250 μm. The pitch conversion unit 3 converts the pitch of the optical fibers 411A-411L from 200 μm to 250 μm by separating the optical fibers 411A-411L into individual fibers and widening the pitch. This allows the optical fibers 411A-411L to be connected to the connector 2 at a pitch of 250 μm. Note that the pitch conversion unit 3 may be omitted if there is no need to convert the pitch.

[0030] The protective tube 21 is substantially cylindrical. The front end of the protective tube 21 is spherical. The outer diameter of the protective tube 21 is, for example, 25 mm or less. The protective tube 21 is provided at the front end of the optical fiber cable 100 with a traction tool. The surface of the protective tube 21 is covered with, for example, polyvinyl chloride or the like. The outer diameter of the protective tube 21 is larger than the outer diameter of the cable main body 1 and the outer diameter of the pulling eye 22.

[0031] The rear end of the pulling eye 22 is connected to the front end of the protective tube 21. The pulling eye 22 is made of a material that is strong enough to pull the optical fiber cable 10. Such a material is, for example, a metal such as iron. The pulling eye 22 has a hollow portion 221. An installer (worker) can pull the optical fiber cable 10 by, for example, connecting a wire or the like to the hollow portion 221 and pulling the wire with a winch.

[0032] (Method for laying optical fiber cable 10) Next, a method for laying the optical fiber cable 10 will be described with reference to Figures 4 to 6. In this embodiment, the optical fiber cable 100 with a traction tool is inserted into a duct 70 provided underground or the like, thereby pulling the optical fiber cable 10 from outdoors 91 to indoors 92. The duct 70 is made of a metal material such as stainless steel. The duct 70 has, for example, a substantially cylindrical shape. The duct 70 is fixed to, for example, a wall surface or a bottom surface.

[0033] As illustrated in FIGS. 4 and 5, the installer inserts the optical fiber cable 100 with the pulling tool into the duct 70 from the entrance 70a of the duct 70 (STEP 01).

[0034] The installer uses a blower 90 disposed near the entrance 70a of the duct 70 to send compressed air into the duct 70. When the compressed air is sent into the duct 70, the optical fiber cable 100 with the pulling tool is pressurized and sent toward the exit 70b by the compressed air. That is, in this embodiment, the optical fiber cable 100 with the pulling tool is pressurized and sent by the compressed air. In this manner, the optical fiber cable 100 with the pulling tool is laid out to the outdoor 91 through the duct 70 (STEP 02). Note that when the optical fiber cable 100 with the pulling tool passes through the duct 70, the only part of the optical fiber cable 100 with the pulling tool that comes into contact with the duct 70 is the protrusion 63 (see FIG. 2 ). Therefore, the insertion characteristics of the optical fiber cable 100 with the pulling tool are better than those of an optical fiber cable without the protrusion 63. Note that the optical fiber cable 10 may be laid out to the outdoor 91 by pulling it through the duct 70 using the pulling tool 20 without pressurizing and sending air.

[0035] The installer blows compressed air into the duct 70 until the pulling eye 22 comes out at the outlet 70b of the duct 70. In this way, the installer lays the optical fiber cable 100 with the pulling tool outdoors 91 and pulls it from outdoors 91 into indoors 92 (STEP 03).

[0036] When the pulling eye 22 comes out at the exit 70b, the installer removes the pulling tool 20 from the optical fiber cable 100 with the pulling tool. In this way, the installer turns the optical fiber cable 100 with the pulling tool into an optical fiber cable 10 without the pulling tool 20 (STEP 04).

[0037] After pulling the optical fiber cable 10 into the indoor 92, the installer removes the outer layer 62 of the optical fiber cable 10, thereby converting the optical fiber cable 10 into an optical fiber cable 10A for indoor wiring (STEP 05). A cross-sectional view of the optical fiber cable 10A for indoor wiring is shown in FIG. 6. As shown in FIG. 6, the optical fiber cable 10A for indoor wiring includes a cable core 4, a wrapping tape 5, and an inner layer 61. The cable core 4, wrapping tape 5, and inner layer 61 of the optical fiber cable 10A for indoor wiring have the same configurations as the cable core 4, wrapping tape 5, and inner layer 61 of the optical fiber cable 10. As shown in FIG. 6, the outermost layer of the optical fiber cable 10A for indoor wiring is the inner layer 61 of the cable jacket 6.

[0038] 4 and 5, STEP 06 will be described. After converting the optical fiber cable 10 into the optical fiber cable 10A for indoor wiring, the installer lays the optical fiber cable 10A for indoor wiring inside the building 92 (STEP 06).

[0039] After laying the optical fiber cable 10A for indoor wiring inside the house 92, the installer stores the optical fiber cable 10A for indoor wiring in a junction box 80 installed inside the house 92 (STEP 07). The optical fiber cable 10A for indoor wiring does not have an outer layer 62 in which the tensile members 7 are embedded, and is therefore more flexible than the optical fiber cable 10. Therefore, the optical fiber cable 10A for indoor wiring can be bent to a small diameter, and can be easily stored in the junction box 80 installed inside the house 92. The junction box 80 is, for example, a connection cabinet or the like.

[0040] The installer connects the connector 2 to other optical fiber cables, optical communication devices, etc. in the connection box 80. That is, the installer connects the optical fiber cores 411A-411L included in the optical fiber cable 10A for indoor wiring to other optical fiber cores located indoors 92 using the connector (STEP 08). As described above, in this embodiment, the optical fiber cores 411A-411L included in the optical fiber cable 10A for indoor wiring to other optical fiber cores located indoors 92 can be connected using the connector 2 without fusion splicing.

[0041] (Measurement of the coefficient of dynamic friction of the outer layer of the cable jacket) The inventors conducted an experiment using a measuring device 200 illustrated in FIG. 7 to measure the dynamic friction coefficient of the outer layer 62 of the cable jacket 6. As illustrated in FIG. 7, the measuring device 200 includes a first metal plate 201, a second metal plate 202, and four cylindrical members 203. The four cylindrical members 203 are inserted into holes provided at the four corners of the first metal plate 201 and the second metal plate 202. For convenience of illustration, only two cylindrical members 203 are shown in FIG. 7. The first metal plate 201 and the second metal plate 202 are flat stainless steel plates to simulate the wall surfaces of a duct through which an optical fiber cable is inserted.

[0042] The inventors measured the dynamic friction coefficient of the outer layer of the cable sheath by sandwiching an optical fiber cable between a first metal plate 201 and a second metal plate 202 disposed above the first metal plate 201, applying a load to the second metal plate 202, and then pulling the optical fiber cable in the longitudinal direction of the metal plate (to the right in FIG. 7 ). In this experiment, a load of approximately 2.0 kg was applied to the second metal plate 202. The length of the optical fiber cable was approximately 300 mm. The length of the first metal plate 201 and the second metal plate 202 in the longitudinal direction was approximately 150 mm. The pulling speed of the optical fiber cable was approximately 500 mm / min. In this embodiment, the dynamic friction coefficient was evaluated using the average value of the pulling tension. The optical fiber cable used in this experiment was the 288-fiber optical fiber cable illustrated in FIG. 1.

[0043] As a result of an experiment using the measuring device 200, it was confirmed that the coefficient of dynamic friction of the outer layer 62 of the cable jacket 6 was 0.5 or less. It was also confirmed that the coefficient of dynamic friction of the inner layer 61 of the cable jacket 6 was greater than 0.5 and 0.7 or less.

[0044] (Optical fiber cable pressure feeding evaluation) In order to evaluate the pumping performance of optical fiber cable 10, the inventors conducted a pumping test in accordance with IEC using pumping device 300 illustrated in FIG. 8. Pipe 301 was 1000 m long and was bent back every 100 m. The radius of curvature R of pipe 301 was 40 times the inner diameter of the pipe, and the inner diameter of pipe 301 was 14 mm. The outer diameter of optical fiber cable 10 was 20 mm. Opening 302 was an inlet for air and the optical fiber cable, and opening 303 was an outlet for air and the optical fiber cable. The air pressure was set to 1.3 MPa or more and 1.5 MPa or less.

[0045] In the pumping experiment, pumping distances of 1000 m or more were evaluated as good, and pumping distances of less than 1000 m were evaluated as bad. Note that the longer the pumping distance, the better the insertion characteristics of the optical fiber cable. In other words, the longer the pumping distance, the better the low friction of the optical fiber cable.

[0046] As a result of the pumping test using the pumping device 300, it was confirmed that the pumping distance of the optical fiber cable 10 was 1000 m or more. Therefore, it was confirmed that the insertion characteristics of the optical fiber cable were good.

[0047] (Evaluation of flame retardancy of optical fiber cables) The inventors conducted a combustion test based on the Plenum Test UL910 (NFPA262) combustion test to evaluate the flame retardancy of the optical fiber cable 10A for indoor wiring.

[0048] In the plenum test UL910, flame retardancy is evaluated by conducting a flame test according to the flame retardancy standard established by UL (Underwriters Laboratory). Although the flame test may vary depending on the shape of the sample, grades such as CMX (flammability test, usually referred to as VW-1 test), CM (vertical tray flame test), CMR (riser test), and CMP (plenum test) are generally established in order of decreasing flame resistance. The plenum test employed in this embodiment is a test designed to simulate an optical fiber cable being installed in a plenum space, which is a space where air is constantly flowing due to air conditioning. The plenum space is, for example, an attic. In the plenum test according to this embodiment, the flame retardancy of the optical fiber cable was evaluated by igniting the optical fiber cable placed in the plenum space and evaluating the flame spread and smoke generation of the optical fiber cable.

[0049] In this embodiment, optical fiber cables that met the predetermined standards in the plenum test UL910 combustion test were evaluated as good, and optical fiber cables that did not meet the predetermined standards were evaluated as poor.

[0050] As a result of the flame test according to the plenum test UL910, it was confirmed that the optical fiber cable 10A for indoor wiring meets the prescribed standards in the flame test according to the plenum test UL910. Therefore, it was confirmed that the optical fiber cable 10A for indoor wiring has good flame retardancy.

[0051] According to the above-described method for laying the optical fiber cable 10, after the optical fiber cable 10 is pulled from the outdoors 91 to the indoors 92, the outer layer 62 of the cable jacket 6 is removed, thereby converting a portion of the optical fiber cable 10 into an optical fiber cable 10A for indoor wiring. Therefore, when the optical fiber cable 10 is laid outdoors 91 through the duct 70, the optical fiber cable 10 has a low-friction outer layer 62 including the tensile strength members 7, and therefore has good insertability. Meanwhile, the outer layer 62 of the cable jacket 6 is removed after the optical fiber cable 10 is laid indoors 92, so that the portion of the cable jacket 6 up to the inner layer 61 is laid indoors 92 as the optical fiber cable 10A for indoor wiring. In other words, when laying indoors, the low-flame-retardant outer layer 62 is removed, and the high-flame-retardant inner layer 61 becomes the outermost layer of the cable jacket 6. Furthermore, the optical fiber cable 10A for indoor wiring does not need to be fusion-spliced ​​to other optical fiber cables located indoors 92. That is, the optical fiber cable 10A for indoor wiring that has been pulled into the indoor space 92 can be used as an indoor cable as is without fusion splicing. Therefore, according to the method for laying the optical fiber cable 10, the optical fiber cable 10 can be efficiently laid while achieving both high flame retardancy and good insertion characteristics for the optical fiber cable 10.

[0052] Furthermore, according to the method for laying the optical fiber cable 10 as described above, the optical fiber cable 10 is inserted into the duct 70 by compressed air feeding, so that the optical fiber cable 10 can be laid efficiently.

[0053] Furthermore, according to the above-described method for laying the optical fiber cable 10, in the connection box 80, the connectors 2 connected to the ends of the optical fiber core wires 411A-411L drawn from the outdoors 91 are connected to other optical fiber core wires located indoors 92. Therefore, according to the above-described method for laying the optical fiber cable 10, the optical fiber core wires 411A-411L drawn from the outdoors 91 into the indoors 92 can be connected to other optical fiber core wires without fusion splicing.

[0054] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure.

[0055] In the above embodiment, the optical fiber cable 10 includes the connector 2 and the pitch conversion section 3, but at least one of the connector 2 and the pitch conversion section 3 may be omitted.

[0056] In the above embodiment, the number of connectors 2 provided in the optical fiber cable 10 and the number of fibers in the connector 2 are not limited to the numbers exemplified in the above embodiment. For example, the optical fiber cable 10 may include two 96-fiber connectors and four 24-fiber connectors.

[0057] In the above embodiment, the cable core 4 accommodates a plurality of optical fiber cores bundled together as the optical fiber ribbon 411, but each of the plurality of optical fiber cores may be a single optical fiber core.

[0058] In the above embodiment, the optical fiber cable 10 includes the pressure winding tape 5, but the pressure winding tape 5 may not be included.

[0059] In the above embodiment, the method for laying the optical fiber cable 10 by air pressure feeding has been described, but the present disclosure is not limited to this example. For example, the optical fiber cable 10 may be laid by connecting a wire to the hollow portion 221 of the pulling eye 22 and pulling the wire with a winch from the outlet 70b of the duct 70. [Explanation of symbols]

[0060] 1: Cable body 2: Connector 3: Pitch conversion section 4: Cable core 5: Presser tape 6: Cable sheath 7:Tensile strength body 8: Tear string 10, 10A: Fiber optic cable 20: Traction device 21: Protection tube 22: Pooling Eye 41: Subunit 61: Inner layer 62: Outer layer 70: Duct 70a: Entrance 70b:Exit 80: Junction box 90: Air blower 91: Outdoors 92: Indoors 100: Fiber optic cable with traction device 200: Measuring equipment 201:First metal plate 202:Second metal plate 203: Cylindrical member 221: Cavity 300: Pressure feeding device 301: Pipe 302,303:Aperture 411: Optical fiber ribbon 411A, 411B, 411C, 411D, 411E, 411F, 411G, 411H, 411I, 411J, 411K, 411L: Optical fiber core 413:Connection part 414: Unconnected part 415: Connected resin R: Pipe bend T1: Thickness of the cable jacket

Claims

1. a cable core including a plurality of optical fiber cores; a cable jacket including an inner layer disposed radially outward of the cable core and an outer layer disposed radially outward of the inner layer; and at least one tensile strength member embedded in the outer layer, The plurality of optical fiber cores is 288 cores or more, The outer layer has a plurality of protrusions formed thereon, a dynamic friction coefficient of the outer layer relative to the duct is smaller than a dynamic friction coefficient of the inner layer relative to the duct; the inner layer being more flame retardant than the outer layer; wiring the optical fiber cable outdoors through the duct by air pressure feeding; Pulling the optical fiber cable from the outdoors to the indoors; removing the outer layer after pulling the optical fiber cable indoors, thereby forming a portion of the optical fiber cable into an optical fiber cable for indoor wiring; and wiring the indoor wiring optical fiber cable indoors, The optical fiber cable laying method, wherein when the optical fiber cable is laid outdoors, only the protruding portion comes into contact with the duct.

2. 2. The optical fiber cable laying method according to claim 1, wherein in the step of laying the optical fiber cable outdoors, the optical fiber cable is passed through the duct by air pressure feeding.

3. Connectors are connected to the ends of the optical fiber cores, storing the optical fiber cable for indoor wiring in the junction box installed indoors; 3. The method for laying an optical fiber cable according to claim 1, further comprising the step of connecting said connector to another optical fiber core in said connection box.

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