WO2023167093A1

WO2023167093A1 - Optical cable, rip cord dislodgement method, and optical fibre exposure method

Info

Publication number: WO2023167093A1
Application number: PCT/JP2023/006659
Authority: WO
Inventors: 悠介辻本; 健大里; 大樹竹田
Original assignee: 株式会社フジクラ
Priority date: 2022-03-02
Filing date: 2023-02-24
Publication date: 2023-09-07
Also published as: TW202343053A

Abstract

This optical cable comprises: an optical fibre; a sheath which protects the optical fibre; and a rip cord which is located at a part of the circumference of the sheath and at least a part of which is embedded in the sheath in a manner so as to be exposed from the inner surface of the sheath. The optical cable is configured such that the rip cord is dislodged to the inner side of the sheath when a side pressure load that is greater than the withstand load of the optical cable during use is applied from the inner surface of the sheath in the exposure direction in which the rip cord is exposed from the sheath, as seen from the centre of the rip cord, in a cross-section orthogonal to the longitudinal direction of the sheath 3.

Description

Optical cable, rip cord removal method and optical fiber lead-out method

TECHNICAL FIELD The present invention relates to an optical cable, a method for removing a ripcord, and a method for extracting an optical fiber.
This application claims priority to Japanese Patent Application No. 2022-031428 filed in Japan on March 2, 2022, the contents of which are incorporated herein.

Patent Document 1 describes a method for using a plurality of optical fiber core wires (optical fibers), a jacket covering the plurality of optical fiber core wires, and a device for tearing the jacket to expose the ends of the optical fiber core wires. An optical cable is disclosed that includes a tear cord (ripcord).

Japanese Patent Application Laid-Open No. 2012-173398

However, with conventional optical cables, there is the problem that the ripcord may be cut unexpectedly when the outer sheath is torn, reducing the efficiency of the lead-out work.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides an optical cable capable of suppressing a decrease in the efficiency of optical fiber lead-out work even if the ripcord is unexpectedly cut, and a ripcord falling off from the optical cable. An object of the present invention is to provide a method and a method for leading out an optical fiber in an optical cable.

An optical cable according to an aspect of the present invention includes an optical fiber, a jacket that protects the optical fiber, and a part of the jacket in a circumferential direction, at least a part of which is exposed to the inner surface of the jacket. and a ripcord embedded in the outer cover, in a cross section orthogonal to the longitudinal direction of the outer cover, in an exposure direction in which the ripcord is exposed from the inner surface of the outer cover when viewed from the center of the ripcord. and the ripcord is configured to drop inside the jacket when a lateral pressure load larger than the withstand load of the optical cable is applied.

A method for removing a ripcord according to an aspect of the present invention comprises an optical fiber, an outer covering for protecting the optical fiber, and at least a part of the outer covering in the circumferential direction so as to be exposed to the inner surface of the outer covering. and a ripcord partially embedded in the jacket, wherein the optical cable extends in an exposure direction in which the ripcord is exposed from the inner surface of the jacket in a cross section perpendicular to the longitudinal direction of the jacket. By applying a lateral pressure load larger than the withstand load during use, the ripcord is dropped inside the outer cover.

An optical fiber lead-out method according to an aspect of the present invention comprises an optical fiber, a jacket for protecting the optical fiber, and at least a part of the jacket in the circumferential direction so as to be exposed to the inner surface of the jacket. and a ripcord partially embedded in the outer jacket, wherein the inner surface of the outer jacket in a cross section perpendicular to the longitudinal direction of the outer jacket. a cord dropping step of dropping the ripcord to the inside of the jacket by applying a lateral pressure load larger than the withstand load of the optical cable in use in the exposure direction in which the ripcord is exposed from the cord; After the removal step, the operator tears the outer cover, triggered by a groove-shaped embedding mark formed on the outer cover so as to be exposed on the inner surface of the outer cover and in which the ripcord was embedded, thereby removing the rip cord. and a fiber tapping step of tapping the optical fiber.

According to the above aspect, even if the ripcord is unexpectedly cut, it is possible to suppress a decrease in the efficiency of the optical fiber lead-out work.

It is a figure which shows the optical cable based on this embodiment in the cross section orthogonal to the longitudinal direction. 2 is an enlarged cross-sectional view showing a main part of the optical cable of FIG. 1; FIG. It is a figure which shows the process which falls off a rip cord from a jacket in the optical cable which concerns on this embodiment. It is a figure which shows the process which falls off a rip cord from a jacket in the optical cable which concerns on this embodiment. FIG. 10 is a diagram for explaining a method of manually tearing the jacket of the optical cable according to the present embodiment by using the embedded trace of the rip cord. 4 is a table showing the relationship between the embedding ratio of the ripcord, the presence or absence of falling off of the ripcord, and the propriety of tearing the outer cover by an operator's hand when the bending elastic modulus of the outer cover is 100 MPa. 4 is a table showing the relationship between the embedding rate of the ripcord, the presence or absence of falling off of the ripcord, and the propriety of tearing of the outer cover by an operator's hand when the bending elastic modulus of the outer cover is 320 MPa. 4 is a table showing the relationship between the embedding rate of the ripcord, the presence or absence of falling off of the ripcord, and the propriety of tearing the outer cover by an operator's hand when the bending elastic modulus of the outer cover is 500 MPa. 4 is a table showing the relationship between the embedding ratio of the ripcord, the presence or absence of falling off of the ripcord, and the propriety of tearing of the outer cover by an operator's hand when the flexural modulus of the outer cover is 630 MPa. 10 is a table showing the relationship between the ripcord embedding rate, the presence or absence of the ripcord coming off, and the possibility of tearing the outer cover by an operator's hand when the flexural modulus of the outer cover is 790 MPa. The flexural modulus of the jacket of the optical cable, the withstand load (first load) when the optical cable is in use, the minimum lateral pressure load (second load) that allows the ripcord to fall off the jacket, and the jacket on the ripcord It is a table of examples showing the relationship between thickness and thickness.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 11. FIG.
As shown in FIG. 1, the optical cable 1 has a plurality of optical fibers 2, a jacket 3, a ripcord 4, a pressure wrap 5 as an arbitrary member, and a tensile member 6 as an arbitrary member. . In this specification, all the plurality of optical fibers 2 in a state of being housed inside a member radially outside of the optical cable 1 from all the plurality of optical fibers 2 are collectively referred to as a core 10 . Note that the number of optical fibers 2 may be one.

The one or more optical fibers 2 each extend in the longitudinal direction of the optical cable 1 (the direction orthogonal to the paper surface in FIG. 1). Although not shown, the optical fiber 2 has a waveguide (made of glass, for example) for propagating an optical signal, and a resin coating layer covering the waveguide. The coating layer may include a colored layer for identifying multiple optical fibers 2 . Also, the optical fiber 2 may be an optical fiber tape core wire, or may be unitized by bundling every certain number of cores.

The jacket 3 extends in the longitudinal direction of the optical cable 1. The jacket 3 is a layer that protects the plurality of optical fibers 2 . An inner surface 3a of the jacket 3 forms a space for accommodating a plurality of optical fibers 2. As shown in FIG. The jacket 3 is formed to be elastically deformable. A load that compresses the jacket 3 in a direction perpendicular to its longitudinal direction is called a lateral pressure load. For example, when this lateral pressure load acts on the jacket 3, the jacket 3 shrinks in the compression direction in a cross section perpendicular to the longitudinal direction of the optical cable 1 (hereinafter also referred to as "the cross section of the optical cable 1"). and elastically deform so as to extend in a direction orthogonal to the compression direction. Examples of materials for the jacket 3 having such characteristics include resin compositions containing polyolefins such as polyethylene and polypropylene, and polyvinyl chloride (PVC) as main components. The characteristics and physical properties of the jacket 3, such as the modulus of elasticity, can be designed according to the types, composition ratios, and combinations of resins and additives that are the main components of the resin composition.

The pressure wrap 5 is interposed between the inner surface 3a of the jacket 3 and the plurality of optical fibers 2 housed inside the jacket 3 to cover the plurality of optical fibers 2. For example, the pressure wrap 5 may be wound vertically or horizontally around the optical fiber 2 . Also, the ratio of the pressure wrap 5 covering the optical fiber 2 may be changed according to the purpose of the pressure wrap 5 . The presser wrap 5 may be made of a flexible sheet. A specific example of the press wrap 5 is a sheet such as polyethylene terephthalate (PET). The presser wrap 5 may be provided with water absorbency. The pressure wrap 5 constitutes the core 10 of the optical cable 1 housed inside the jacket 3 together with the plurality of optical fibers 2 described above. Since the pressure wrap 5 is a member radially outside the optical cable 1 relative to all the plurality of optical fibers 2, the entirety of the plurality of optical fibers 2 is accommodated in the pressure wrap 5, and the plurality of optical fibers 2 as a whole are cores. 10 will be formed. Since the optical cable 1 has the presser wrap 5, contact between the ripcord 4 and the optical fibers 2 can be reduced when the ripcord 4 is removed from the jacket 3, and a plurality of optical fibers 2 form an optical fiber bundle. In this case, it is possible to prevent the ripcord 4 falling off from the jacket 3 from being buried in the optical fiber bundle and becoming difficult to take out. However, the optical cable 1 may not have the pressure winding 5, for example. In this case, the jacket 3 is a member radially outside the optical cable 1 relative to all of the plurality of optical fibers 2, so that the plurality of optical fibers 2 described above are entirely housed in the inner surface 3a of the jacket 3, and the plurality of The entire optical fiber 2 will form the core 10 .

The ripcord 4 extends in the longitudinal direction of the optical cable 1. The ripcord 4 is a member for tearing the jacket 3 positioned outside the ripcord 4 . The ripcord 4 is made of a material that is not easily deformed or broken by the stress when tearing the outer cover 3, that is, a material with a high elastic modulus and high breaking strength, and can be designed to have a thickness according to the object to be torn. Materials for the ripcord 4 include, for example, steel wires, twisted aramid fibers, and polyester fibers. As shown in FIGS. 1 and 2, the ripcord 4 is at least partially embedded in the outer cover 3 so as to be exposed on the inner surface 3a of the outer cover 3. As shown in FIGS. That is, an embedding mark 31 is formed in the jacket 3 where the ripcord 4 is embedded. In the present embodiment, the cross-sectional shape of the ripcord 4 in the cross section of the optical cable 1 is circular, but is not limited to this. The cross-sectional shape of the rip cord 4 may be, for example, a shape having unevenness in the circumferential direction.

As shown in FIG. 1, two ripcords 4 are arranged so as to sandwich the core 10 in the cross section of the optical cable 1 . The two ripcords 4 are arranged so that the two ripcords 4 and the center 1C of the core 10 are aligned in a cross section of the optical cable 1 . The direction in which one ripcord 4 and the center 1C of the core 10 are aligned and the direction in which the other ripcord 4 and the center 1C of the core 10 are aligned may, for example, cross each other. Also, the number of ripcords 4 is not limited to two, and may be one or three or more. When the number of ripcords 4 is plural, the plural ripcords 4 may be spaced apart in the circumferential direction of the jacket 3 .

Here, the direction in which the ripcord 4 is exposed from the inner surface 3a of the outer cover 3 as viewed from the center of the ripcord 4 is referred to as the exposed direction. The rip cord 4 falls off inside the jacket 3 in this exposure direction in the cross section (cross-sectional view) of the optical cable 1 . When a lateral pressure load larger than the withstand load of the optical cable 1 is applied in the exposure direction, the optical cable 1 is configured to drop inside the jacket 3 . That is, even if the optical cable 1 is subjected to a lateral pressure load that is less than the withstand load described above when the optical cable 1 is used, the ripcord 4 will not come off from the jacket 3 .
Here, the above-mentioned "exposure direction" may correspond to the arrangement direction in which the ripcord 4 and the center 1C of the core 10 are aligned in the cross section of the optical cable 1, or the ripcord 4 and the center of the core 10 are aligned. It may correspond to the alignment direction. Although the center of the core 10 is aligned with the center 1C of the core 10 in FIG. 1, they may not be aligned. In FIG. 1 , the “exposure direction” corresponds to the direction toward the center 1C of the core 10 in the radial direction of the optical cable 1 . In addition, the “exposure direction” may not coincide with the direction toward the center 1C of the core 10 in the radial direction of the optical cable 1, for example.
Also, "when the optical cable 1 is used" may be, for example, when the optical cable 1 is laid, during maintenance and inspection, or when data communication is being performed by the laid optical cable 1, or the like. Also, the "withstand load of the optical cable 1 during use" may be, for example, the maximum lateral pressure load that can act on the optical cable 1 in the direction orthogonal to its longitudinal direction within the normal usage range of the optical cable 1. Moreover, the above-mentioned "withstanding load" may be, for example, a lateral pressure load that does not increase the transmission loss beyond the allowable value when the optical cable 1 is used. The “withstanding load” may be a lateral pressure load at which the transmission loss in the optical cable 1 does not rise to 0.15 dB or more. The “withstanding load” may vary depending on the specifications and uses of the optical cable 1 .

The embedding rate of the ripcord 4 in which the ripcord 4 is embedded in the jacket 3 will be explained. In this embodiment, the embedding ratio of the ripcord 4 is defined as the contact of the ripcord 4 with respect to the length of the entire circumference of the ripcord 4 in the cross section of the optical cable 1 shown in FIG. It is indicated by the ratio of length 4L. The embedding rate of the ripcord 4 in this embodiment is 40% or more and less than 100%. The fact that the embedding rate of the ripcord 4 is less than 100% means that at least the ripcord 4 is exposed on the inner surface 3 a of the jacket 3 .

In this embodiment, the jacket 3 described above is a circle whose dimension in the arrangement direction in which the ripcord 4 and the center 1C of the core 10 are aligned in the cross section of the optical cable 1 and the dimension in the orthogonal direction perpendicular to the arrangement direction are substantially equal. It is formed in a shape (substantially circular). In the following description, the above-mentioned "arrangement direction" and the corresponding "exposure direction" may be referred to as the vertical direction Y, and the above-described "perpendicular direction" may be referred to as the horizontal direction X.

The thickness 3T of the jacket 3 in the vertical direction Y (exposure direction) will be described with reference to FIG. The thickness 3T of the jacket 3 in the vertical direction Y is the thickness 3T of the jacket 3 that overlaps the ripcord 4 in the vertical direction Y. In other words, the thickness 3T of the jacket 3 in the vertical direction Y is the total thickness of the jacket 3 from the inner surface 3a to the outer surface 3b of the jacket 3 in the vertical direction Y. This is the dimension after subtracting the length of the embedded part. In the following description, the thickness 3T of the jacket 3 in the vertical direction Y (exposure direction) may be referred to as "the thickness 3T of the jacket 3 on the ripcord 4". In this embodiment, the thickness 3T of the jacket 3 on the ripcord 4 is 0.5 mm or more and 4.0 mm or less.

A tensile strength member 6 is embedded in the jacket 3 . The tensile strength member 6 has the function of suppressing contraction of the jacket 3 and protecting the optical fiber 2 from tensile stress in the longitudinal direction of the optical cable 1 . Steel wire or fiber reinforced plastic (FRP), for example, can be used for the tensile member 6 .
The bending elastic modulus of the strength member 6 is higher than that of the jacket 3 . The tensile members 6 are arranged in the cross section of the optical cable 1 so as to be aligned in the left-right direction X (perpendicular direction) with respect to the center 1C of the core 10, for example. In this embodiment, a pair of tensile members 6 are arranged so as to sandwich the core 10 in the cross section of the optical cable 1 . A pair of tensile members 6 may be arranged in parallel with the longitudinal direction of the optical cable 1 .

In FIG. 1, two tensile members 6 are set as one set, and a pair of sets are arranged on both sides of the core 10, but this is not the only option. For example, a pair of three or more tensile strength members 6 may be arranged on both sides of the core 10 , or one tensile strength member 6 may be arranged on each side of the core 10 . Moreover, in FIG. 1, the plurality of tensile members 6 forming a set are spaced apart, but they may be in contact with each other, for example. Moreover, a plurality of tensile members 6 forming a set may be twisted. Also, three or more sets or three or more tensile members 6 may be arranged substantially evenly in the circumferential direction of the jacket 3 . However, the optical cable 1 may not have the tension member 6, for example.

By arranging the tensile members 6 in the horizontal direction X with respect to the center 1C of the core 10, it is possible to make it difficult to compress the jacket 3 in the horizontal direction X. As a result, the jacket 3 of the present embodiment is easier to compress in the vertical direction Y (exposed direction) than in the horizontal direction X (perpendicular direction).

In addition, since the tensile strength member 6 is arranged as described above, the optical cable 1 of the present embodiment has an anisotropy in bending in the cross section of the optical cable 1, which is easy to bend in a direction centering on the bending neutral line NL of the optical cable 1. have sex. To explain this point, the neutral bending line NL is a line connecting the centers of the pair of tensile members 6 . By positioning the tensile strength member 6 on the neutral line NL, the optical cable 1 can be easily bent in a direction centered on the neutral line NL and is difficult to bend in other directions.
The neutral line NL indicates the position of the optical cable 1 where the expansion and contraction in the longitudinal direction of the optical cable 1 is small when the optical cable 1 is bent. For example, in FIG. 1, when the optical cable 1 is bent so that the optical cable 1 protrudes upward from the neutral line NL, the portion of the optical cable 1 located above the neutral line NL extends in the longitudinal direction of the optical cable 1 and extends toward the neutral line NL. The portion of the optical cable 1 positioned below is contracted in the longitudinal direction of the optical cable 1 .

In the optical cable 1 of the present embodiment, the neutral line NL of bending extends in the left-right direction X (perpendicular direction). compresses in the vertical direction Y (exposure direction).

In the optical cable 1 of this embodiment configured as described above, the optical fiber 2 can be led out by two different lead-out methods. A method for leading out the two optical fibers in the optical cable 1 will be described below.

<Method of Leading out the First Optical Fiber>
The first optical fiber lead-out method (hereinafter referred to as the first lead-out method) is the same as the conventional method. That is, in the first lead-out method, the outer cover 3 is torn by pulling the ripcord 4 while the ripcord 4 is held by the outer cover 3 . Thereby, the optical fiber 2 can be exposed to the outside of the jacket 3 .

<Method of Leading out the Second Optical Fiber>
In the second optical fiber lead-out method (hereinafter referred to as the second lead-out method), first, as shown in FIGS. drop-off method).
In the cord removal process (rip cord removal method), in the cross section (cross sectional view) of the optical cable 1, the center 1C of the core 10 and the rip cord 4 are aligned in the vertical direction Y (arrangement direction), when the optical cable 1 is in use. A lateral pressure load larger than the withstand load is applied to the optical cable 1 .
At this time, the jacket 3 contracts in the vertical direction Y and extends in the horizontal direction X, as shown in FIG. Therefore, the portion of the jacket 3 that holds the ripcord 4 also extends in the left-right direction X. As shown in FIG. As a result, the holding of the ripcord 4 by the outer cover 3 is released, and the ripcord 4 drops inside the outer cover 3 . 3 and 4, the lateral pressure load is applied to the optical cable 1 by sandwiching the optical cable 1 in the vertical direction Y between the two flat plates 100, but the present invention is not limited to this.

After the cord drop-off process, a fiber lead-out process of leading the optical fiber 2 to the outside of the jacket 3 is performed. In the fiber lead extraction step, as shown in FIG. The optical fiber 2 is exposed using the embedding trace 31 formed on the jacket 3 . The embedded trace 31 after the ripcord 4 has fallen off is exposed on the inner surface 3a of the outer cover 3 and has a groove shape extending in the longitudinal direction of the outer cover 3. As shown in FIG. A worker tears the jacket 3 by hand using the burial marks 31 as a trigger, and the optical fiber 2 is exposed outside the jacket 3 . Reference numeral 32 in FIG. 5 indicates a tear line 32 of the outer cover 3 to be torn by hand of the operator.

In the cord removal step of the second lead-out method, for example, the rip cord 4 may be removed inside the jacket 3 by bending the optical cable 1 . In this case, the optical cable 1 may be bent so that the bending neutral line NL (see FIG. 1) of the optical cable 1 is perpendicular to the vertical direction Y. FIG. By bending the optical cable 1 in this manner, the sheath 3 is shrunk in the vertical direction Y. As shown in FIG. As a result, a lateral pressure load is applied to the optical cable 1 in the vertical direction Y, and the ripcord 4 drops inside the jacket 3 . When bending the optical cable 1, the side pressure load can be applied to the optical cable 1 more easily than when the operator compresses the optical cable 1 with his or her fingers.

As described above, according to the optical cable 1, the method for removing the rip cord, and the method for pulling out the optical fiber according to the present embodiment, the lateral pressure load in the vertical direction Y (exposure direction) larger than the withstand load when the optical cable 1 is in use. is applied, the ripcord 4 drops inside the jacket 3. Therefore, even if the optical cable 1 is subjected to a lateral pressure load that is less than the withstand load of the optical cable 1 during use, the ripcord 4 does not fall off inside the jacket 3 and is held by the jacket 3 .
That is, it is possible to prevent the rip cord 4 from unexpectedly falling inside the jacket 3 when the optical cable 1 is used. By intentionally applying a lateral pressure load larger than the withstand load to the optical cable 1 , the ripcord 4 can be intentionally dropped inside the jacket 3 .
If the ripcord 4 unexpectedly falls off the jacket 3, the ripcord 4 may become entangled with the optical fiber 2. As shown in FIG. In that case, the optical fiber 2 may be cut by the ripcord 4 when the jacket 3 is torn by the ripcord 4 . For this reason, it is undesirable for the ripcord 4 to unexpectedly fall off the jacket 3 .

Since the ripcord 4 can be intentionally dropped inside the outer cover 3, either the first lead-out method or the second lead-out method can be selected depending on the environment in which the lead-out work is performed (for example, the temperature environment) and the skill level of the operator. can be selected to suppress a decrease in the efficiency of the optical fiber 2 lead-out work. For example, if the first lead-out method is selected when the lead-out work is performed in a low-temperature environment or by an unskilled worker, the rip cord 4 may be unexpectedly damaged when the outer cover 3 is torn. It may break. In such a case, if the second lead method is selected, the optical fiber 2 can be efficiently led. Also, when a highly skilled worker performs the picking work, the optical fiber 2 can be picked up efficiently by selecting the first picking method with a small number of steps.

In addition, in the optical cable 1 of the present embodiment, in the cross section of the optical cable 1, the jacket 3 is easily compressed in the exposure direction (vertical direction Y) in which the ripcord 4 is exposed from the inner surface 3a of the jacket 3, and the exposure direction It is difficult to compress the jacket 3 in the orthogonal direction (horizontal direction X). Thus, even if the ripcord 4 is covered with the outer cover 3 and cannot be seen, the ripcord 4 can be easily dropped inside the outer cover 3 only by applying a side pressure load in the direction in which the outer cover 3 is easily compressed. be able to.

In addition, in the optical cable 1 of the present embodiment, the tensile strength member 6 having a higher flexural modulus than the jacket 3 is arranged in the above orthogonal direction (horizontal direction X) with respect to the center 1C of the core 10 in the cross section of the optical cable 1. placed in position. This tensile strength member 6 makes it difficult to compress the jacket 3 in the orthogonal direction. Therefore, it is possible to provide an optical cable 1 that is easy to compress in the exposure direction and difficult to compress in the orthogonal direction.

Further, in the optical cable 1 of the present embodiment, the thickness 3T of the jacket 3 in the exposure direction (vertical direction Y), that is, the thickness 3T of the jacket 3 on the ripcord 4 is 0.5 mm or more and 4.0 mm or less. is.
Since the thickness 3T of the outer cover 3 in the exposure direction is 4.0 mm or less, after the ripcord 4 is dropped from the outer cover 3, the groove-like embedding mark of the outer cover 3 in which the ripcord 4 is embedded is left. Using 31 as a trigger, the jacket 3 can be easily torn off by hand. Note that if the thickness 3T of the outer cover 3 in the exposure direction is greater than 4.0 mm, the outer cover 3 is too thick, and it is difficult to tear the outer cover 3 by hand using the embedding marks 31 as a trigger. Become.

In addition, since the thickness 3T of the jacket 3 in the exposure direction is 0.5 mm or more, the lateral pressure load applied to cause the ripcord 4 to come off the inside of the jacket 3 is equal to the withstanding load when the optical cable 1 is in use. can be larger than In other words, it is possible to prevent the rip cord 4 from falling inside the jacket 3 due to a lateral pressure load that is less than the withstand load when the optical cable 1 is in use. Furthermore, in other words, it is possible to prevent the rip cord 4 from unexpectedly falling inside the jacket 3 when the optical cable 1 is used.

Further, in the optical cable 1 of this embodiment, the embedding rate of the ripcord 4 embedded in the jacket 3 is 40% or more and less than 100%. When the ripcord 4 is buried at a rate of 40% or more, it is possible to prevent the ripcord 4 from unexpectedly falling off from the jacket 3 immediately after the optical cable 1 is manufactured and when the optical cable 1 is used. In addition, since the embedding rate of the ripcord 4 is less than 100%, the ripcord 4 is exposed inside the jacket 3 . As a result, the ripcord 4 can be removed from the jacket 3 by applying a lateral pressure load in the exposure direction to the optical cable 1 .

Next, referring to the tables of FIGS. 6 to 10, the embedding rate of the ripcord 4, whether or not the ripcord 4 falls off from the jacket 3, and whether or not the jacket 3 can be torn by the operator's hand. I will explain the relationship between
In the tables of FIGS. 6 to 10, the flexural moduli of the jacket 3 are different from each other. The bending elastic modulus of the jacket 3 in the table of FIG. 6 is 100 MPa, and the bending elastic modulus of the jacket 3 in the table of FIG. 7 is 320 MPa. The bending elastic modulus of the jacket 3 in the table of FIG. 8 is 500 MPa, and the bending elastic modulus of the jacket 3 in the table of FIG. 9 is 630 MPa. Furthermore, the bending elastic modulus of the jacket 3 in the table of FIG. 10 is 790 MPa.

"Presence/absence of ripcord falling off" in FIGS. "Presence" in the column "Presence or absence of ripcord falling off" indicates that the ripcord 4 has fallen off from the jacket 3, and "No" indicates that the ripcord 4 has not fallen off from the jacket 3. In addition, "-" in the column "whether or not the rip cord has come off" indicates that whether or not the rip cord 4 has come off has not been determined.

Regarding the presence or absence of the rip cord 4 falling off from the outer sheath 3, the lateral pressure load of 6000 N was applied to the optical cable 1 immediately after manufacturing the optical cable 1 ("Immediately after cable manufacturing" in FIGS. 6 to 10) and after manufacturing. It was confirmed in two states after applying in the direction Y (exposure direction) (“after application of 6000 N” in FIGS. 6 to 10). A lateral pressure load of 6000 N is an example of a maximum lateral pressure load (hereinafter referred to as “maximum allowable load”) that can be allowed when using the optical cable 1 .
A lateral pressure load larger than the maximum allowable load is, for example, a load of a magnitude that does not restore the transmission loss even if the application of the lateral pressure load to the optical cable 1 is canceled, in other words, the characteristics of the optical cable 1 change irreversibly. load of magnitude. The lateral pressure test to apply the above lateral pressure load is a test procedure according to Telcordia Technologies Generic Requirements GR-20-CORE (Issue4, July 2013) (hereinafter sometimes abbreviated as "Telcordia GR-20"). Is going. In the lateral pressure test, a lateral pressure load of 6000 N is applied to the optical cable 1 in the vertical direction Y for 1 minute by sandwiching the optical cable 1 in the vertical direction Y with 100 mm square metal flat plates in an environment of 22°C.

"Tearability of outer cover by hand" in FIGS. "Possible" in the column of "Tearable outer cover by hand" indicates that the outer cover 3 could be torn by the operator's hand, and "Unacceptable" indicates that the outer cover 3 was torn by the operator's hand. indicate that it was not possible. Regarding whether or not the jacket 3 can be torn by the operator's hand, after applying a lateral pressure load of 6000 N (maximum allowable load) to the manufactured optical cable 1 in the vertical direction Y (exposure direction) (see FIGS. 6 to 10 "After applying 6000 N").

"Comprehensive judgment" in FIGS. 6 to 10 is indicated by "○ (good)" and "X (bad)". "○" in "Comprehensive Judgment" indicates that all of the following three conditions are satisfied and passed. The first condition is that the ripcord 4 does not fall off in the optical cable 1 immediately after manufacture (the ``ripcord dropout presence/absence'' in ``immediately after cable manufacture'' in FIGS. 6 to 10 is ``no''). The second condition is that the ripcord 4 falls off after a lateral pressure load of 6000N (maximum allowable load) is applied to the optical cable 1 ("Whether or not the ripcord falls off" in "After applying 6000N" in FIGS. 6 to 10 is “Yes”). The third condition is that the worker can tear the jacket 3 by hand after applying a lateral pressure load of 6000 N to the optical cable 1 (“Hand tearability” in FIGS. be). An "x" in "Comprehensive Judgment" indicates that one or more of the above three conditions are not met, and that the product is unsatisfactory.

As shown in FIGS. 6 to 10, when the embedding ratio of the ripcord 4 is 30% or less, regardless of the bending elastic modulus of the jacket 3, the ripcord 4 is It is known to fall out of On the other hand, when the embedding ratio of the ripcord 4 is 40% or more, the ripcord 4 does not come off from the jacket 3 immediately after the optical cable 1 is manufactured regardless of the bending elastic modulus of the jacket 3 . That is, irrespective of the bending elastic modulus of the jacket 3, the embedding rate of the ripcord 4 is 40% or more. It can be seen that it is possible to prevent it from falling off.

Further, as shown in FIGS. 6 to 9, when the bending elastic modulus of the jacket 3 is in the range of 100 MPa to 630 MPa, the ripcord 4 is detached from the jacket 3 by applying a lateral pressure load of 6000 N to the optical cable 1. It can be seen that the lower limit of the embedding rate of the ripcord 4 that can be used is 40%. When the embedding rate of the ripcord 4 is 30% or less, the ripcord 4 is dropped from the jacket 3 immediately after the optical cable 1 is manufactured. It is not possible to judge the presence or absence of falling off.

On the other hand, when the flexural modulus of the jacket 3 is in the range of 100 MPa or more and 630 MPa or less, the rip cord 4 can be detached from the jacket 3 by applying a lateral pressure load of 6000 N to the optical cable 1. The upper limit of the embedding rate of varies according to the flexural modulus of the jacket 3 . Specifically, the upper limit of the embedding ratio of the ripcord 4 that allows the ripcord 4 to fall off decreases as the bending elastic modulus of the outer cover 3 increases. This is because, as the embedding rate of the ripcord 4 increases, the amount of contraction of the outer cover 3 in the exposed direction in order to drop the ripcord 4 must be increased. This is because it becomes difficult to shrink the cover 3 in the exposure direction.

As shown in FIG. 10, when the flexural modulus of the jacket 3 is excessively large at 790 MPa, a side pressure load of 6000 N is applied to the optical cable 1 within a range where the embedding rate of the rip cord 4 is 40% or more. Even if the voltage is applied, the ripcord 4 cannot be removed from the jacket 3.
On the other hand, as shown in FIG. 6, when the flexural modulus of the outer cover 3 is as small as 100 MPa, the ripcord 4 can be dropped from the outer cover 3 even if the ripcord 4 is embedded at a high embedding rate of 95%. can. That is, when the flexural modulus of the jacket 3 is sufficiently small and the embedding rate of the ripcord 4 is less than 100%, the ripcord 4 can be removed from the jacket 3 .

As shown in FIGS. 6 to 9, the embedding rate of the ripcord 4 (40% or more embedding rate) that allows the ripcord 4 to fall off the outer cover 3 by applying a lateral pressure load of 6000 N (maximum allowable load). , basically the mantle 3 can be torn by hand. As an exception, as shown in FIG. 9, when the rip cord 4 is buried at 80% in the optical cable 1 whose jacket 3 has a flexural modulus of 630 MPa, a lateral pressure load of 6000 N (maximum allowable load) is applied. By doing so, the ripcord 4 can be detached from the outer cover 3, but the outer cover 3 cannot be torn off by the operator's hand. This indicates that if the flexural modulus of the outer cover 3 is excessively high, it becomes difficult for the operator to tear the outer cover 3 by hand.

Further, as shown in FIGS. 7 to 10, in the optical cable 1 in which the flexural modulus of the jacket 3 is in the range of 320 MPa or more and the embedding rate of the rip cord 4 is 30% or less, the rip is Although the cord 4 has fallen off, the outer cover 3 cannot be torn off by the operator's hand. This is because the embedding rate of the ripcord 4 in the outer cover 3 is low, and the size of the embedded trace 31 of the ripcord 4 in the outer cover 3 is small, making it difficult to tear the outer cover 3. It is conceivable that there are
On the other hand, as shown in FIG. 6, in the optical cable 1 in which the bending elastic modulus of the jacket 3 is 100 MPa and the rip cord 4 embedding rate is 30% or less, the jacket 3 can be torn by the operator's hand. . This is probably because even if the size of the embedding marks 31 is small, the bending elastic modulus of the outer cover 3 is low, so that the outer cover 3 is easily torn.

As shown in FIGS. 6 to 9, the lower limit of the embedding rate of the ripcord 4 at which the overall judgment is "○" is 40% in the range of the bending elastic modulus of the outer cover 3 from 100 MPa to 630 MPa. be. Further, the upper limit value of the embedding rate of the ripcord 4 at which the comprehensive judgment is "O" tends to decrease as the bending elastic modulus of the outer cover 3 increases. Therefore, the upper limit of the embedding rate of the ripcord 4 should be at least less than 100%, but it may be 90% or less, 80% or less, or 70% or less depending on the bending elastic modulus of the outer cover 3. preferably lower.

The preferred upper limit of the embedding ratio of the ripcord 4 based on the tables of FIGS. , the lateral pressure load for detaching the ripcord 4 from the jacket 3 can be set smaller than the maximum allowable load (6000N). Note that the lower limit of the lateral pressure load can be set to the "second load" shown in FIG. 11, which will be described later. Therefore, when the lateral pressure load for detaching the ripcord 4 from the jacket 3 is set between the "second load" and the maximum allowable load (6000N), the upper limit of the embedding ratio of the ripcord 4 is , the lateral pressure load can be set smaller than the maximum allowable load (6000N). From this, the upper limit of the embedding ratio of the ripcord 4 based on the tables of FIGS. This is the maximum value to drop out.

As shown in FIG. 10, when the flexural modulus of the outer cover 3 is excessively large at 790 MPa, the overall judgment is "x" regardless of the embedding rate. Therefore, it is preferable that the bending elastic modulus of the jacket 3 is, for example, 630 MPa or less.

Next, referring to the table of FIG. 11, the flexural modulus of the jacket 3, the withstand load of the optical cable 1 during use, the minimum lateral pressure load that allows the ripcord 4 to fall off the jacket 3, and the ripcord The relationship with the thickness 3T (see FIG. 1) of the jacket 3 on 4 will be described.
In the four optical cables 1 of Examples A to D shown in FIG. 11, the rip cord 4 embedding rate is 70%. In the optical cables 1 of the four examples A to D, the flexural modulus of the jacket 3 is different from each other. The jacket 3 of Example A is designed to meet ICEA S-83-596 when the first load described below is applied. The jacket 3 of Example B is designed to meet Telcordia GR-20 when the first load is applied. The jacket 3 of Example C is designed to meet ICEA_S-104-696 when the first load is applied. The jacket 3 of Example D is designed to meet the specific specifications of Telcordia GR-20 when the first load is applied.

The "first load" in FIG. 11 is the lateral pressure load applied to the optical cable 1 in the exposure direction (vertical direction Y) perpendicular to its longitudinal direction, and is the withstand load of the optical cable 1 during use. As described above, the withstand load is the lateral pressure load at which the transmission loss in the optical cable 1 does not rise above the allowable value (for example, 0.15 dB or more). The first load is proportional to the flexural modulus of the jacket 3 . That is, the higher the flexural modulus of the jacket 3, the larger the first load.

The “second load” in FIG. 11 is a lateral pressure load applied to the optical cable 1 in the exposure direction (vertical direction Y) orthogonal to its longitudinal direction, and the lateral pressure load that causes the ripcord 4 to come off the jacket 3. is the lower limit of The second load is larger than the first load described above due to the setting of the thickness 3T of the jacket 3 on the ripcord 4, which will be described later.
In the optical cables 1 of the four examples A to D, the maximum lateral pressure load that can be allowed when using the optical cable 1 of the jacket 3, that is, the maximum allowable load, is 6000 N, which is larger than the second load. .

"The thickness of the jacket on the ripcord" in FIG. 11 is the thickness 3T of the jacket 3 on the ripcord 4 shown in FIG. In FIG. 11, the lower limit and upper limit of the thickness 3T of the jacket 3 are shown.

As shown in FIG. 11, the lower limit of the thickness 3T of the jacket 3 is equal to each other in the four examples AD, which is 0.5 mm. By setting the thickness 3T of the jacket 3 to 0.5 mm or more, the second load (the lower limit of the lateral pressure load that causes the ripcord 4 to fall off) in the optical cable 1 of each embodiment is reduced to the first load (the use of the optical cable 1 load capacity at times). Thereby, it is possible to prevent the rip cord 4 from unexpectedly falling off from the jacket 3 when the optical cable 1 is used. In addition, when the thickness 3T of the jacket 3 is smaller than 0.5 mm, the second load is equal to or smaller than the first load. In this case, during normal use of the optical cable 1, the ripcord 4 unexpectedly falls off from the jacket 3.
The fact that the lower limit value of the thickness 3T of the jacket 3 is the same among the four Examples A to D is the first among the four Examples A to D due to the difference in the bending elastic modulus of the jacket 3. This is due to different loads.

The upper limit value of the thickness 3T of the outer cover 3 is a value at which the worker can tear the outer cover 3 by hand, triggered by the embedded trace 31 of the outer cover 3 after the ripcord 4 has fallen off. It is set according to the magnitude of the flexural modulus of 3. Specifically, the higher the flexural modulus of the jacket 3, the smaller the upper limit value of the thickness 3T of the jacket 3 at which the operator can tear the jacket 3 by hand.

In Example A in which the bending elastic modulus of the jacket 3 is as small as 100 MPa, the upper limit of the thickness 3T of the jacket 3 is 4.0 mm. In Example A, the thickness 3T of the outer cover 3 is set to 4.0 mm or less, so that the operator can tear the outer cover 3 by hand. If the thickness 3T of the outer cover 3 is greater than 4.0 mm, the operator cannot tear the outer cover 3 by hand.
The bending elastic modulus of the jacket 3 is 320 MPa, and in Example B, which is larger than Example A, the upper limit of the thickness 3T of the jacket 3 is smaller than that in Example A, and is 3.5 mm. In Example B, by setting the thickness 3T of the jacket 3 to 3.5 mm or less, the worker can tear the jacket 3 by hand as in the case of Example A.

In Example C, in which the flexural modulus of the jacket 3 is 500 MPa, which is even larger than that in Example B, the upper limit of the thickness 3T of the jacket 3 is 3.0 mm, which is smaller than that in Example B.
In Example C, by setting the thickness 3T of the jacket 3 to 3.0 mm or less, the operator can tear the jacket 3 by hand as in Example A.
In Example D, in which the bending elastic modulus of the jacket 3 is 630 MPa, which is even larger than that in Example C, the upper limit of the thickness 3T of the jacket 3 is 2.5 mm, which is smaller than that in Example C.
In Example D, by setting the thickness 3T of the jacket 3 to 2.5 mm or less, the worker can tear the jacket 3 by hand as in Example A.
From the above, considering the ease of tearing the outer cover 3 by the hand of the operator, the thickness 3T of the outer cover 3 should be at least 4.0 mm or less. 3.5 mm or less, 3.0 mm or less, or 2.5 mm or less.

Although the details of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

In the present invention, the jacket 3 is such that, for example, in the cross section of the optical cable 1, the dimension in the exposure direction (vertical direction Y) in which the ripcord 4 is exposed from the inner surface 3a of the jacket 3 is the orthogonal direction ( It may be an elliptical shape 7 smaller than the dimension in the left-right direction X), a rectangular shape, or the like. When the outer cover 3 has such a shape, for example, even if the tensile strength member 6 is not embedded in the outer cover 3, the outer cover 3 can be easily compressed in the "exposed direction" rather than in the "perpendicular direction". can be done.

When the outer cover 3 has a shape such as the above-described elliptical shape or rectangular shape, it is easy to bend in a direction centered on the neutral line of bending extending in the orthogonal direction (horizontal direction X), and in other directions (for example, the exposure direction ( It is difficult to bend in the direction centered on the neutral line of bending extending in the vertical direction Y). That is, the optical cable 1 having the jacket 3 having the shape described above has the same bending anisotropy as in the above embodiment.

In the present invention, for example, the ripcord 4 may be buried inside the outer cover 3 without being exposed on the inner surface of the outer cover 3 . In this case, the thickness of the inner portion of the jacket 3 located inside the ripcord 4 in the radial direction of the optical cable 1 is, for example, when a lateral pressure load larger than the withstand load of the optical cable 1 is applied to the optical cable 1 It may be set to such an extent that the inner portion of the outer cover 3 is fractured.

The present invention may be applied to a slot type optical cable having a slot rod in which a groove (slot) for accommodating the optical fiber 2 is formed, or may be applied to a slotless type optical cable having no slot rod. good.

DESCRIPTION OF SYMBOLS 1... Optical cable 2... Optical fiber 3... Jacket 3a... Inner surface of jacket 3 3T... Thickness of jacket 3 4... Rip cord 4L... Contact length 6... Tensile member 31... Burying Marks, X... horizontal direction (perpendicular direction), Y... vertical direction (exposure direction)

Claims

an optical fiber;
a jacket that protects the optical fiber;
a ripcord at least partially embedded in the outer cover so as to be exposed on the inner surface of the outer cover in a part of the outer cover in the circumferential direction;
with
In a cross section perpendicular to the longitudinal direction of the jacket, a lateral pressure load greater than the withstand load of the optical cable in use in the exposure direction in which the ripcord is exposed from the inner surface of the jacket when viewed from the center of the ripcord. an optical cable configured such that the ripcord drops inside the jacket when a is applied to the cable.
The optical cable according to claim 1, wherein the withstand load is a lateral pressure load that does not increase the transmission loss of the optical fiber to 0.15 dB or more when the optical cable is used.
The optical cable according to claim 1 or claim 2, wherein the jacket is more likely to be compressed in the exposure direction than in the orthogonal direction perpendicular to the exposure direction in the cross section.
Further comprising a tensile strength body embedded in the outer cover and having a higher flexural modulus than the outer cover,
4. The optical cable according to claim 3, wherein, in the cross section, the tensile members are arranged at positions aligned in the orthogonal direction with respect to the center of the core.
The optical cable according to any one of claims 1 to 4, wherein the thickness of the jacket in the exposure direction is 0.5 mm or more and 4.0 mm or less.
1 to claim 1, wherein the contact length of the ripcord in the circumferential direction where the ripcord contacts the jacket in the cross section is 40% or more and less than 100% of the length of the entire circumference of the ripcord. 6. The optical cable according to any one of 5.
By applying a lateral pressure load larger than the withstand load of the optical cable in use in the arrangement direction in which the ripcord and the center of the optical cable are aligned in a cross-sectional view, the ripcord is dropped inside the jacket. drop off method.
8. The ripcord according to claim 7, wherein the lateral pressure load is applied by bending the optical cable so that a neutral line of bending of the optical cable is perpendicular to the arrangement direction in a cross section orthogonal to the longitudinal direction of the jacket. How to fall off.
a cord dropping step of dropping the ripcord to the inside of the jacket by applying a lateral pressure load larger than the withstanding load of the optical cable in use in the direction in which the ripcord and the center of the optical cable are aligned in a cross-sectional view; ,
After the cord dropping step, a worker tearing the outer cover triggered by a groove-shaped embedding mark formed in the outer cover so as to be exposed on the inner surface of the outer cover and in which the ripcord was embedded. and a fiber lead-out step of lead-out the optical fiber.