JP3006601B1 - Optical cable - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide an optical cable capable of easily distinguishing an inverted portion from the outside of a jacket and having good take-out of an optical fiber after laying. A plurality of optical fibers (6) are provided around a center member (2).
Are assembled in an SZ twisted state, and the optical cable 1 in which the periphery of the optical fiber 6 is covered with a jacket 10 is disposed near the inner peripheral surface of the jacket 10 and any one of the optical fibers 6 forms. A ferromagnetic member 8 extending along the SZ locus is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable laid underground, on land, aerial or undersea, and in particular, a plurality of optical fibers are assembled in an SZ twisted state, and the periphery of each optical fiber is covered with a jacket. Optical cable.

[0002]

2. Description of the Related Art Hitherto, there has been known an optical cable in which a plurality of optical fibers are assembled in an SZ twisted state around a central member having a built-in strength member, and each optical fiber is covered with a jacket. . Such an optical cable is laid underground, on land, aerial or on the sea floor, but once the optical cable is laid, a part of the jacket is removed or cut off in the middle of the optical cable, and the optical cable is cut. In some cases, it is necessary to take out a part of the optical fiber contained in the optical fiber and branch it (so-called middle post-branch).

Here, in an optical cable having a plurality of optical fibers extending in an SZ shape, an optical cable (center member)
The length of each optical fiber is larger than the length of the optical fiber. Therefore,
If the jacket near the reversal part of the SZ locus formed by the optical fiber (the part where the optical fiber reverses from S twist to Z twist or from Z twist to S twist) is removed, the optical fiber is pulled excessively. It can be taken out smoothly from the optical cable without any trouble. In view of this point, if the reversal part of the SZ trajectory formed by the optical fiber can be determined from the outside of the jacket of the optical cable, the workability when branching after laying the cable is improved.

[0004] Techniques related to the above are disclosed in US Pat. No. 4,828,352 and US Pat.
No. 9,966 is known.
The conventional optical cables described in these documents are obtained by assembling a plurality of optical fibers (optical fiber cores or pipe cores) in an SZ twist around a central member. The periphery of each optical fiber is covered with a jacket formed of a synthetic resin or the like. The outer jacket is provided with a reversing portion display mark such as a symbol or a character at a position corresponding to the reversing portion of the SZ locus formed by each optical fiber.

[0005] This optical cable is manufactured according to the following procedure. That is, when the process from the twisting of the optical fiber to the process of forming the jacket is performed in one manufacturing line, a display marker forming apparatus (core marker apparatus) is disposed downstream of the jacket cooling water tank. In addition, a signal indicating the reversal direction of the reversing plate located at the most downstream side is extracted from a plurality of reversing plates (lay plates) used for twisting the optical fiber around the central member. Then, based on this signal, the supply length of the central member, and the predetermined offset length, when it is determined that the reversing section has reached below the display mark forming apparatus, the reversing section display mark is displayed by the display mark forming apparatus. Formed on the jacket.

In the case where the optical fiber twisting step and the jacket forming step are divided, in the optical fiber twisting step, the same method as in the case where an optical cable is manufactured on one manufacturing line as described above. Then, a color tape or a metal tape indicating the position of the inversion section is pasted on the holding tape wound around the outer periphery of each optical fiber. In the step of forming the outer cover, before the outer cover is extruded, the color tape or the like attached to the presser winding tape is detected by a color sensor, a metal sensor, or the like, and is extruded based on the detection signal. A reversal portion indicating mark is formed on the outer cover.

[0007]

However, the conventional optical cable has the following problems since it is configured as described above.

That is, in the conventional optical cable, before the outer sheath is provided around the optical fiber, the operation of the color tape or the like attached to the holding tape for indicating the position of the reversing portion or the operation of the reversing plate is performed. It is manufactured by a method of detecting the position of the reversing portion based on the above and marking the reversing portion on the extruded jacket. For this reason, in the conventional optical cable, it is practically impossible to determine the position of the reversing portion inside the outer jacket from the outside of the outer jacket after the outer jacket is once provided unless the inverting portion display mark is provided. . In addition, when manufacturing an optical cable, equipment for attaching a color tape or the like is required, so that the cost required for the equipment for manufacturing the optical cable increases, and the manufacturing cost of the optical cable also increases.

[0009] Further, the inversion portion display mark attached to the outer cover for indicating the position of the inversion portion may disappear after the optical cable is laid. Also in this case, it is impossible to detect the position of the reversing portion from the outside of the jacket unless the jacket is completely removed. Therefore, if the inversion mark is peeled off on the jacket, it is extremely difficult to determine the position of the inversion section inside the jacket from the outside of the jacket. Remarkably deteriorates.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical cable in which the inverted portion can be easily identified from the outside of the jacket and the optical fiber can be easily taken out after laying.

[0011]

According to the first aspect of the present invention, there is provided an optical cable in which a plurality of optical fibers are assembled in an SZ twisted state around a central member and an outer periphery of the optical fiber is covered with a jacket. And a ferromagnetic member disposed near the inner peripheral surface of the jacket and extending along the SZ locus formed by any of the optical fibers.

A plurality of optical fibers are provided around the center member by SZ.
When the optical fibers are assembled in a twisted state, the inverted portion of the SZ locus formed by the optical fibers is located on the same circumference centered on the central axis of the optical cable. , Tape cores, tape core laminates, pipe cores, etc.). Based on this point, in this optical cable, the ferromagnetic member is arranged along the SZ locus formed by any of the optical fibers. Further, the ferromagnetic member is arranged near the inner peripheral surface of the jacket. Thus, the inverted portion of the ferromagnetic member can be easily and reliably detected from the outside of the jacket using a metal sensor or the like. Then, by detecting the inverted portion of the ferromagnetic member, the position of the inverted portion of each optical fiber can be determined.

As a result, irrespective of the presence or absence of the reversing portion indicating mark indicating the position of the reversing portion, when the optical fiber is taken out and branched by removing a part of the jacket at the intermediate portion of the optical cable, the operation is most difficult. It is possible to easily determine the appropriate position of the reversing part, and the work efficiency is improved. In this way, this optical cable can easily find the most suitable place for branching and enables flexible branching work. Therefore, this optical cable is suitable for laying in a place where the extra length of the optical cable must be shortened (for example, underground). It is suitable.

In this case, the ferromagnetic member is preferably an iron wire. That is, the iron wire is inexpensive among the ferromagnetic member materials and is excellent in handleability. Therefore, the optical cable according to the present invention can be manufactured easily and inexpensively.

Further, it is preferable to further include a reversal portion indicating mark which is disposed on the outer cover and indicates a position corresponding to the reversal portion of the SZ locus formed by the ferromagnetic member. In this case, it is preferable to extrude the outer cover and cool it, and then detect the inverted portion of the ferromagnetic member via the outer cover with a metal sensor or the like, and attach an inverted portion display mark. Alternatively, the optical cable provided with the jacket may be once wound up, and a reversing portion display mark may be put on the jacket by another line. By providing the reversing portion indicating mark in this way, when removing and branching the optical fiber by removing a part of the jacket at the middle part of the optical cable, the position of the reversing portion most suitable for work can be more easily determined. In addition to being able to make a determination, work efficiency is significantly improved.

When the optical fibers are assembled in an SZ twisted state around the center member and the ferromagnetic member is arranged, the following configuration may be adopted.

That is, the center member is a multi-groove spacer in which a plurality of SZ-shaped spiral grooves are formed on the outer periphery, the optical fiber is housed in the spiral groove, and the ferromagnetic member is any two spiral grooves. The center member is preferably a multi-groove spacer having a plurality of SZ-shaped helical grooves formed on the outer periphery, and the optical fiber is fixed to the multi-groove spacer so as to be located therebetween. Preferably, the ferromagnetic member is accommodated in any of the spiral grooves.

Further, a plurality of optical fiber units including optical fibers are provided, and the optical fiber units are assembled in an SZ twist around a central member.
It is preferable that the optical fiber unit is disposed between any two optical fiber units, and a plurality of optical fiber units including optical fibers are provided, and the optical fiber units are assembled in an SZ twist around a central member, The ferromagnetic member is
Preferably, it is fixed to any of the optical fiber units. In this case, the optical fiber unit is preferably made of a single-groove spacer accommodating the optical fiber, and the optical fiber unit is preferably a loose tube.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an optical cable according to the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a sectional view showing a first embodiment of an optical cable according to the present invention. In the center of the optical cable 1 shown in FIG. 1, a long cylindrical member 2 serving as a central member is arranged. The cylindrical member 2 is formed of a synthetic resin such as an LDPE resin and has an outer diameter of 25 mm. In the center of the cylindrical member 2,
One steel stranded wire 3 is buried. The steel stranded wire 3 is one in which seven steel wires having a diameter of 2 mm are stranded together. Fifteen optical fiber units 4 are twisted in an SZ shape on the outer periphery of the cylindrical member 2 (see FIG. 3). The SZ twist pitch of each optical fiber unit 4 (twice the length between adjacent inversion portions) is 900 mm, and the SZ inversion angle φ is 275 °.

Here, as shown in FIG. 1, one of the fifteen optical fiber units 4 has one optical fiber unit 4.
(The optical fiber unit 4F) includes a ferromagnetic member 8
Has been fixed. The optical fiber unit 4F includes, as shown in FIG.
(Optical fiber). The single groove spacer 5F is manufactured as one straight long member by extruding PBT resin or the like.
It has a substantially U-shaped cross section. Bottom 5a of single groove spacer 5F
The pair of side portions 5b define one fiber housing portion 5c capable of housing various optical fibers such as an optical fiber core, a pipe core, and a tape core.

Further, a pair of side portions 5b of the single groove spacer 5F is provided.
The ferromagnetic member 8 is embedded in the upper end of the side wall 5b on one side (in this case, the left side in FIG. 2). In this optical cable 1, as the ferromagnetic member 8,
A 0.4 mm iron wire (ferromagnetic wire) is used. Iron wire is inexpensive among ferromagnetic materials and has excellent handleability. Therefore, the optical cable according to the present invention is
It can be manufactured easily and inexpensively. As the ferromagnetic member 8, a nickel wire, a cobalt wire, or the like may be used instead of the iron wire. When embedding the ferromagnetic member 8 in the single groove spacer 5F, the ferromagnetic member 8 may be extruded simultaneously with the melted PBT resin or the like. In addition. The dimensions of the single groove spacer 5 are Bu = 6.0 mm, Bu = 4.0 mm,
Bl = 5.0 mm, bl = 3.5 mm, D = 5.0 m
m and d = 4.5 mm.

The tape core laminate 6 is formed by laminating ten eight-core tape cores. Tape cored laminate 6
Are housed in the fiber housing portion 5c of the single groove spacer 5F. Then, a holding tape 7 such as a nonwoven fabric is wound around the single groove spacer 5F in which the tape core laminate 6 is accommodated. Thereby, the single groove spacer 5F and the tape core laminate 6 are unitized.

The optical fiber unit 4 other than the optical fiber unit 4F is a unit in which a single groove spacer 5 and a tape core laminate 6 are unitized. The single groove spacer 5 is the same as the single groove spacer 5F except that the ferromagnetic member 8 is not embedded in the side portion 5b. By twisting each optical fiber unit 4 (4F) around the central member 2 in an SZ shape, each tape core laminate 6 as an optical fiber is assembled around the cylindrical member 2 in an SZ twisted state. Become.

As shown in FIG. 1, a holding tape 9 made of a nonwoven fabric or the like is wound without any gap around each optical fiber unit 4 twisted in an SZ shape on the outer peripheral surface of the cylindrical member 2. Then, around the holding tape 9,
A jacket 10 having an outer diameter of 41 mm formed of low-density polyethylene is provided. Thereby, the optical cable 1
Inside is protected. Further, as shown in FIG. 1, one tear string 11 is built in the outer cover 10.

In the inside of the jacket 10 of the optical cable 1, FIG.
As shown in (2), each of the optical fiber units 4 and 4F (tape fiber laminate 6) forms a locus extending in an SZ shape (hereinafter, referred to as “SZ locus”). The SZ locus includes a portion where the optical fiber units 4 and 4F are inverted from S twist to Z twist or from Z twist to S twist (hereinafter, referred to as “inversion portion R”). Then, as shown in FIG. 3, the inversion portion R of the SZ locus formed by each of the optical fiber units 4 and 4F.
Are located on the same circumference around the central axis of the optical cable 1.

Similarly, inside the jacket 10 of the optical cable 1, as shown in FIG. 3, the ferromagnetic member 8 forms an SZ locus along the tape core laminate 6 included in the optical fiber unit 4F. I have. The SZ locus formed by the ferromagnetic member 8 also includes the inversion portion RF, and the inversion portion RF of the ferromagnetic material 8
Are also located on the same circumference as the inversion portion R of each of the optical fiber units 4 and 4F. The ferromagnetic material 8 is provided on one side 5b of the single groove spacer 5F included in the optical fiber unit 4F.
1, it is located near the inner peripheral surface of the outer casing 10 as shown in FIG. 1 when disposed around the center member 2.

Therefore, the inverted portion RF of the ferromagnetic member 8 can be easily and reliably detected from the outside of the jacket 10 using a metal sensor or the like. Then, by detecting the inversion portion RF of the ferromagnetic member 8, the position of the inversion portion R of each of the optical fiber units 4, 4F (tape core laminate 6) can be determined. That is, in the optical cable 1, it is possible to easily determine the position of the inversion portion R (RF) regardless of whether or not there is a display indicating the position of the inversion portion R of each of the optical fiber units 4 and 4F. As a result, the work efficiency at the time of taking out and branching the optical fiber (tape core laminate 6) by removing a part of the jacket at the intermediate portion of the optical cable 1 is improved. Thus, this optical cable 1
Since an optimum location for branching can be easily found and a flexible branching operation can be performed, the optical cable is suitable for laying in a place where the extra length of the optical cable must be shortened (for example, underground).

Further, as shown in FIG. 4, on the jacket 10 of the optical cable 1, a reversing portion indication mark M indicating a position corresponding to the reversing portion R of the SZ locus formed by the ferromagnetic member 8 is provided. Have been. In the optical cable 1, the letter “R” of the alphabet is marked on the outer cover 10 using a printing device or the like as the inversion portion display mark M. By providing the reversing portion display mark M in this way, when removing and branching the tape core laminate 6 (optical fiber) by removing a part of the jacket 10 at the intermediate portion of the optical cable 1, work is difficult. The most appropriate position of the reversing portion R can be more easily determined, and the working efficiency is extremely improved. It is preferable that the inversion portion display mark M be provided over the entire circumference of a concentric circle centered on the central axis of the optical cable 1 in consideration of the distinguishability at the time of work.

As shown in FIG. 5, a sign (symbol) may be used as the inversion portion display mark M. In the example shown in FIG. 5, an elongated metal tape 12 (for example, a copper tape having a length of about 30 mm and a width of about 5 mm) is provided as a reversal part display mark M at a position corresponding to the reversal part R of the jacket 10. 1 is attached so as to be orthogonal to the longitudinal direction. Even if such a configuration is adopted, the position of the reversing portion R can be determined very easily from the outside of the jacket 10 of the optical cable 1. At the time of removal, it is possible to easily determine the position of the reversal portion R that is most appropriate for the operation, so that the operation efficiency is extremely improved. The shape and the like of the inverted portion display mark M are not limited at all, and any characters, symbols, and signs can be used.

Next, a procedure for manufacturing the above-described optical cable 1 will be described.

When the optical cable 1 is manufactured, first, the optical fiber units 4 and 4F are twisted around the cylindrical member 2 using the optical fiber twisting line 50 shown in FIG. In this case, the cylindrical member 2 as the center member
Is wound on a core winding reel 51. The optical fiber units 4 and 4F are wound around the optical fiber unit winding reel 52 in advance. And the core winding reel 51
And one optical fiber unit 4 and 4F (in this case, 15) from the optical fiber unit winding reel 52 to the reverse perforated panel group 53.

Each of the optical fiber units 4 and 4F is gradually twisted into an SZ shape by each of the inversion eye plates 54 which independently rotate while changing the rotation direction within a predetermined inversion angle. A thread or the like for temporarily fixing the optical fiber units 4 and 4F is wound around the optical fiber units 4 and 4F twisted around the columnar member 2 by the holding-winding device 55, and the holding winding is performed. The tape 8 is wound without any gap. Thereby, the respective tape core laminates 6 included in the respective optical fiber units 4 and 4F assemble around the cylindrical member 2 in an SZ twisted state. The ferromagnetic member 8 included in the optical fiber unit 4F is arranged in an SZ twisted state along the tape core laminate 6 included in the optical fiber unit 4F. The semi-finished product H1 with the holding tape 8 wound thereon is wound on a take-up reel 56.

When the twisting of the optical fiber units 4 and 4F to the cylindrical member 2 is completed, the jacket 10 is provided on the semi-finished product H1 by using the jacket forming line 60 shown in FIG. In this case, as shown in FIG.
Supplies the semi-finished product H1 to the jacket extruder 61.
From the jacket extrusion device 61, the jacket 10 is placed around the semi-finished product H1.
Is extruded. The semi-finished product is introduced into the jacket cooling water tank 62, whereby the jacket 10 is cooled and solidified.

When the jacket 10 is solidified, the ferromagnetic material 8 buried at the upper end of the side portion 5b of the single groove spacer 5F included in the optical fiber unit 4F passes through the holding tape 8 via the holding tape 8. It will be located near the inner peripheral surface (see FIG. 1).
reference). The semi-finished product H2 in a state where the jacket 10 is solidified passes through a metal detection device 63 arranged downstream of the jacket cooling water tank 62. The metal detecting device 63 can detect the position of the reversal portion RF of the ferromagnetic member 8 via the jacket 10.

A method of detecting the reversal portion RF of the ferromagnetic member 8 by the metal detecting device 63 will be described with reference to FIGS. The metal detecting device 63 includes a metal sensor 65 having a coil 64 (for example, EX-42 manufactured by Keyence Corporation).
2) (for example, 12), and each coil 64
The inversion unit RF is detected based on the induced current generated in the inversion unit. As shown in FIG. 8, each metal sensor 65 is disposed on a concentric circle that covers the periphery of the jacket 10,
4 faces one surface of the jacket 10. FIG. 8 shows only three metal sensors 65a, 65b, and 65c among the twelve metal sensors 65. As shown in FIG. 7, the metal detection device 63 is connected to a control computer 66. When an induced current is generated in the coil 64 of each metal sensor 65, the metal detection device 63 sends a predetermined detection signal to the control computer 66. A signal is sent.

As shown in FIG. 8, it is assumed that the ferromagnetic member 8 has passed near the metal sensor 65a at a certain time t1.
In this case, an induced current is generated in the coil 64 of the metal sensor 65a as shown in FIG. 9, and a detection signal is sent from the metal sensor 65a to the control computer 66. Since the ferromagnetic member 8 extends in an SZ shape along any one of the tape core laminates 6, when the semi-finished product H2 advances, it passes near the metal sensor 65b adjacent to the metal sensor 65a. (Time t2), and further pass near the metal sensor 65c adjacent to the metal sensor 65b (time t2).
3).

The ferromagnetic member 8 extending in the SZ shape is
It has a reversing part RF. Therefore, for example, as shown in FIG. 8, the ferromagnetic member 8 once passes through the vicinity of the metal sensor 65c and then again passes through the vicinity of the metal sensor 65c until a predetermined time T (see FIG. 9) elapses. (Time t
4). That is, in the example shown in FIG. 8, the reversal part RF of the ferromagnetic member 8 passes near the metal sensor 65c at a time tm intermediate between the times t3 and t4. This makes it possible to easily and reliably detect the reversal portion RF of the ferromagnetic member 8 from outside the jacket 10 based on the detection signal emitted from each metal sensor 65 of the metal detection device 63.

The control computer 64 is connected to a display mark forming device 67 which is arranged on the downstream side of the metal detecting device 63 and is capable of arranging the inversion portion display mark M on the jacket 10. As shown in FIG. 4, when a character is used as the inversion portion display mark M, a printing device (for example, an inkjet manufactured by Imaju) is used as the display mark forming device 67. In this case, it is preferable to arrange three printing devices in order to provide the reversal portion display mark M on the entire circumference of the jacket 10. In addition, as shown in FIG. 5, when a mark using a metal tape is provided as the reversal portion display mark M, a tape sticking device may be used as the display mark forming device 67.

The control computer 64 controls the metal detector 6
A predetermined operation is performed on the basis of the detection signal received from the third ferromagnetic member 8, and the inverted portion RF of the ferromagnetic member 8
Find the timing of reaching below. That is, the control computer 66 transmits the metal detection device 63 (the metal sensor 6).
5), if an induced current is generated twice in the coil 64 included in any one of the metal sensors 65 within a predetermined time T based on the detection signal (time t3 in FIG. 8).
And t4), a time tm intermediate between times (t3, t4) at which the induced current is generated in the one metal sensor 65 is obtained,
At this time tm, it is determined that the inverted portion RF of the ferromagnetic member 8 has passed through the metal detection device 63.

When the reversing portion RF of the ferromagnetic member 8 reaches below the display mark forming device 67, the control computer 66 operates the display mark forming device 65. The display mark forming device 65 includes a cover 10 that covers the vicinity of the reversal portion RF (R).
A reversal portion display mark M (for example, the character “R”) is attached on the top. Thus, the optical cable 1 shown in FIGS. 1 and 4 or 5 is completed. The completed optical cable 1 is taken up on a take-up reel 68.

As described above, according to the method for manufacturing an optical cable according to the present invention, the SZ in which each of the optical fiber units 4 and 4F (the tape core laminate 6) is formed from the outside of the jacket 10.
It is possible to easily and inexpensively manufacture the optical cable 1 that can determine the reversal part R of the trajectory. Further, S formed by the optical fiber units 4 and 4F (tape core laminate 6)
In a state where the position corresponds to the inverted portion R of the Z trajectory, the inverted portion display mark M can be attached to the jacket 10. Further, after completion of the optical cable 1, it is possible to inspect whether or not the reversal portion indication mark M accurately corresponds to the position of the reversal portion R of the tape core laminate 6. In addition, the jacket 10
Therefore, it is not necessary to perform marking for indicating the reversal portion R before providing the marking, so that it is possible to prevent the marking material (paint, various tapes, etc.) from being mixed into the material of the jacket when the jacket is provided. .

In the first embodiment, after the jacket 10 is extruded and cooled, the metal detector 63 detects the inverted portion RF of the ferromagnetic member 8 via the jacket 10 and Although the display mark M is provided, the present invention is not limited to this. That is, the optical cable 1 provided with the jacket 10 may be once wound up, and the reversal portion display mark M may be put on the jacket 10 by another line.

[Second Embodiment] FIG. 10 is a sectional view showing a second embodiment of the optical cable according to the present invention. The optical cable 20 shown in the figure has a plurality of (five) loose tubes 24 as an optical fiber unit. As shown in FIG. 10, a ferromagnetic member 28 is fixed to one of the 15 loose tubes 24 (referred to as a loose tube 24F). As shown in FIG. 11, the loose tube 24F is a tube 25F (outer diameter 6.0 mm, inner diameter 4.0 mm) formed of polyethylene.
5 mm), and a tape core laminate 26 (optical fiber) housed inside the tube 25.

A ferromagnetic member 28 is embedded in the tube 25F. In this case, 0.
A 4 mm iron wire (ferromagnetic wire) is used. When embedding the ferromagnetic member 28 in the tube 25F, the ferromagnetic member 8 may be extruded simultaneously with the molten polyethylene resin or the like. The tape core laminate 26 is obtained by laminating ten eight-core ribbons. In addition, inside the tube 25, together with the tape core laminate 26,
Grease 27 serving as a cushioning material is filled. Loose tubes 24 other than loose tubes 24F
Is a unit of the tube 25 and the tape core laminate 26. The tube 25 is the same as the tube 25F except that the ferromagnetic member 28 is not embedded.

At the center of the optical cable 20, a long columnar member 22 (LDPE
(Resin, 25 mm in diameter). Column member 2
Is embedded in the center of the steel wire. This steel stranded wire 23 is also formed by twisting seven steel wires each having a diameter of 2 mm.
It is a book. Fifteen loose tubes 24 are twisted in an SZ shape on the outer periphery of the cylindrical member 22. The SZ twist pitch of each loose tube 24 is 90
0 mm, and the SZ inversion angle φ is 275 °. A presser winding tape 29 is wound around each loose tube 24 without gaps. An outer diameter 4 made of low-density polyethylene is further formed around the holding tape 29.
A 1 mm jacket 21 is provided. In addition, this jacket 2
1 includes one tear string 21a.

When the optical cable 20 is manufactured, the loose tubes 24 and 24F may be twisted around the cylindrical member 22 using an optical fiber twisting line 50 shown in FIG. That is, the loose tubes 24 and 24F are wound around the optical fiber unit winding reel 52, and one cylindrical member 22 and a plurality of (15 in this case) loose tubes 24, 24F
Should be supplied.

[Third Embodiment] FIG. 12 is a sectional view showing a third embodiment of the optical cable according to the present invention. The optical cable 1A shown in the figure has a structure basically similar to that of the optical cable 1 shown in FIG. The optical cable 1A shown in FIG. 12 is different from the optical cable 1 of FIG. 1 in that all (fifteen) identical optical fiber units 4 are provided and there is no optical fiber unit 4F to which the ferromagnetic member 8 is fixed. . In the optical cable 1A, the optical fiber units 4 are assembled around the cylindrical member 2 in an SZ twist. Then, the ferromagnetic member 8 </ b> A is arranged between any two optical fiber units 4. The ferromagnetic member 8A is a ferromagnetic wire (outer diameter 0.8 mm) in which a steel wire having an outer diameter of 0.5 mm is coated with polyethylene. Thus, instead of fixing the ferromagnetic member to the optical fiber unit 4 (single groove spacer 5), the ferromagnetic member may be disposed between the two optical fiber units 4.

When manufacturing the optical cable 1A, the optical fiber unit 4 is twisted around the cylindrical member 2 using the optical fiber twisting line 50 shown in FIG.
Then, the ferromagnetic member 8A may be supplied along any one of the optical fiber units 4. In this case, a dedicated winding reel around which the ferromagnetic member 8A is wound is installed on the side of any one of the optical fiber unit winding reels 52, and the ferromagnetic member 8A is inverted together with the single optical fiber unit 4. It may be supplied to the eyelet group 53. Further, the ferromagnetic member 8A is temporarily fixed to a single groove spacer 5 included in any one of the optical fiber units 4 using a tape or the like, and such an optical fiber unit 4 is attached to the optical fiber unit winding reel 52. It may be wound and supplied to the inverting plate group 53.

[Fourth Embodiment] FIG. 13 is a sectional view showing an optical cable according to a fourth embodiment of the present invention. The optical cable 20A shown in FIG.
Have basically the same structure. The optical cables 20A shown in FIG.
The optical cable 20 differs from the optical cable 20 of FIG. 10 in that the optical cable 20 has a plurality (15) and does not have a loose tube 24F to which the ferromagnetic member 8 is fixed. In the optical cable 20 </ b> A, the loose tubes 24 are assembled around the cylindrical member 2 in an SZ twist. Then, the ferromagnetic member 28 </ b> A is arranged between any two optical fiber units 4.
The ferromagnetic member 28A is a ferromagnetic wire (0.8 mm in outer diameter) in which a steel wire having an outer diameter of 0.5 mm is coated with polyethylene. As described above, the ferromagnetic member is connected to the loose tube 24.
Instead of fixing to the (tube 25), it may be arranged between two loose tubes 24.

When the optical cable 1A is manufactured, the loose tube 24 is twisted around the cylindrical member 2 using the optical fiber twisting line 50 shown in FIG. Then, the ferromagnetic member 8A may be supplied along any one of the loose tubes 24. In this case, a dedicated winding reel around which the ferromagnetic member 28A is wound is installed on the side of any of the optical fiber unit winding reels 52, and the ferromagnetic member 28A is placed together with one loose tube 24 together with the reversing member. It may be supplied to the plate group 53. Further, the ferromagnetic member 28A is temporarily fixed to a tube 25 included in any one of the loose tubes 24 by using a tape or the like, and such a loose tube 24 is attached to the optical fiber unit winding reel 5.
2 and may be supplied to the reverse perforated panel group 53.

[Fifth Embodiment] FIG. 14 is a sectional view showing an optical cable according to a fifth embodiment of the present invention. The optical cable 30 shown in the figure uses a multi-groove spacer 32 (outer diameter 24 mm) made of HDPE resin as a central member. In the center of the multi-groove spacer 32, one steel stranded wire 3
3 are buried. This steel stranded wire 33 is obtained by twisting seven steel wires having a diameter of 2 mm into one. Also,
A plurality (ten) of SZ-shaped spiral grooves 34 are formed on the outer periphery of the multi-groove spacer 32. The depth of each spiral groove 34 is
4.3 mm, upper width (corresponding to bu in FIG. 2) is 4.2 m
m, bottom width is 3.2 mm. Further, the SZ pitch of each spiral groove 34 is 700 mm, and the SZ inversion angle φ is 27
5 ゜.

A ferromagnetic member 38 is fixed to the multi-groove spacer 32 so as to be located between any two spiral grooves 34. That is, in the multi-groove spacer 32 in which a plurality of SZ-shaped spiral grooves 34 are formed on the outer periphery, the ribs 32a located between any two spiral grooves 34 also extend in the SZ shape. In the multi-groove spacer 32, one ferromagnetic member 38 is embedded in a rib 32a extending in an SZ shape. In the optical cable 30, a 0.4 mm iron wire (ferromagnetic wire) is used as the ferromagnetic member 38. As the ferromagnetic member 38, a nickel wire, a cobalt wire, or the like may be used instead of the iron wire.

Each spiral groove 34 is provided with one core wire of eight cores.
A zero-core laminated fiber core 36 (optical fiber) is accommodated therein. As a result, the tape core laminate 36
Are gathered around the multi-groove spacer 32 as a central member in an SZ twisted state. The ferromagnetic member 38 extends along the SZ trajectory formed by the single tape core laminate 6.
A holding tape 35 such as a nonwoven fabric is wound around the multi-groove spacer 32 in which the tape core laminate 36 is accommodated in each spiral groove 34 without any gap. A jacket 31 (outer diameter 29 mm) formed of low-density polyethylene and containing a tear string 31a is provided around the holding tape 35. Since the ferromagnetic member 38 is embedded (fixed) in the rib 32 a of the multi-groove spacer 32, it is located near the inner peripheral surface of the jacket 31.

To manufacture the optical cable 30,
The multi-groove spacer 32 manufactured by simultaneously extruding the ferromagnetic member 38 together with the melted HDPE resin or the like is used.
Each spiral groove 34 of the multi-groove spacer 32 accommodates the tape core laminate 6 (optical fiber). Then, using the jacket forming line 60 shown in FIG. 7, the jacket 31 may be provided around the multi-groove spacer 32 accommodating the tape core laminate 6.

[Sixth Embodiment] FIG. 15 is a sectional view showing a sixth embodiment of the optical cable according to the present invention. The optical cable 30A shown in FIG.
Have a basically similar structure. The optical cable 30A shown in FIG. 15 differs from the optical cable 30 of FIG. 14 in that it includes a multi-groove spacer 32A to which the ferromagnetic member 38 is not fixed. In the optical cable 30A, the ferromagnetic member 38A is housed in any of the spiral grooves 34.
The ferromagnetic member 38A is a ferromagnetic wire (0.8 mm outer diameter) in which a steel wire having an outer diameter of 0.5 mm is coated with polyethylene. Even with such a configuration, the ferromagnetic member 38A
Is disposed near the inner peripheral surface of the jacket 31 and extends along the SZ locus formed by one tape core laminate 6 (optical fiber).

When the optical cable 30A is manufactured, a general multi-groove spacer 32A containing a steel stranded wire 33 is used.
Is used. Then, each spiral groove 34 of the multi-groove spacer 32
Then, when accommodating the tape core laminate 6 (optical fiber), the ferromagnetic member 38A is accommodated in any one of the spiral grooves 34 together with the tape core laminate 6.

[0058]

Since the optical cable according to the present invention is configured as described above, the following effects can be obtained.
That is, by arranging the ferromagnetic member so as to be located near the inner peripheral surface of the jacket along the SZ locus formed by any of the optical fibers, the reversing portion can be easily formed from the outside of the jacket. It is possible to realize an optical cable that can be distinguished and has good optical fiber take-out property after laying.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of an optical cable according to the present invention.

FIG. 2 is a sectional view showing an optical fiber unit included in the optical cable of FIG.

FIG. 3 is a plan view showing the inside of a jacket provided on the optical cable of FIG. 1;

FIG. 4 is a plan view for explaining a reversing portion display mark provided on the optical cable of FIG. 1;

FIG. 5 is a plan view illustrating another embodiment of the inversion portion display mark.

FIG. 6 is a schematic diagram showing an optical cable production line for producing the optical cable of FIG.

FIG. 7 is a schematic diagram showing an optical cable production line for producing the optical cable of FIG.

FIG. 8 is a schematic diagram for explaining a method of detecting a reversal portion of the ferromagnetic member.

FIG. 9 is a chart for explaining a method of detecting a reversal portion of the ferromagnetic member.

FIG. 10 is a sectional view showing a second embodiment of the optical cable according to the present invention.

11 is a sectional view showing an optical fiber unit included in the optical cable of FIG.

FIG. 12 is a sectional view showing a third preferred embodiment of the optical cable according to the present invention.

FIG. 13 is a sectional view showing a fourth embodiment of the optical cable according to the present invention.

FIG. 14 is a sectional view showing a fifth embodiment of the optical cable according to the present invention.

FIG. 15 is a sectional view showing a sixth embodiment of the optical cable according to the present invention.

[Explanation of symbols]

1, 1A, 20, 20A, 30, 30A ... optical cable,
2,22: cylindrical member (center member), 3, 23, 33: copper stranded wire (tensile member), 4, 4F: optical fiber unit,
5, 5F: single groove spacer; 6, 26, 36: tape core laminate (optical fiber); 7, 9, 29, 35: holding tape, 8, 28, 28A, 38, 38A: ferromagnetic member;
10, 21, 31 ... jacket, 24, 24F ... loose tube (optical fiber unit), 25, 25F ... tube,
32, 32A: multi-groove spacer (center member) M: reversing part,
R, RF: reversal unit, 63: metal detector, 64: coil, 65, 65a, 65b, 65c: metal sensor.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tadaki Haruki 1-chome, Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (56) References JP-A-11-133279 (JP, A) Hei 8-227033 (JP, A) Jiko Hei 7-25769 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/44

Claims (9)

(57) [Claims] 1. A plurality of optical fibers are provided around a central member.
In an optical cable in which the periphery of the optical fiber is covered with a jacket while being gathered in a Z-twisted state, the optical fiber is disposed near an inner peripheral surface of the jacket, and an SZ locus formed by any of the optical fibers An optical cable comprising a ferromagnetic member extending along the optical cable. 2. The optical cable according to claim 1, wherein the ferromagnetic member is an iron wire. 3. The apparatus according to claim 1, further comprising a reversing portion indicating mark disposed on the outer cover and indicating a position corresponding to a reversing portion of an SZ locus formed by the ferromagnetic member.
Or the optical cable according to 2. 4. The center member is a multi-groove spacer in which a plurality of SZ-shaped spiral grooves are formed on the outer periphery, the optical fiber is accommodated in the spiral groove, and the ferromagnetic member is The optical cable according to any one of claims 1 to 3, wherein the optical cable is fixed to the multi-groove spacer so as to be located between the two spiral grooves. 5. The central member is a multi-groove spacer having a plurality of SZ-shaped spiral grooves formed on an outer periphery, the optical fiber is housed in the spiral groove, and the ferromagnetic member is The optical cable according to any one of claims 1 to 3, wherein the optical cable is housed in one of the grooves. 6. A plurality of optical fiber units including the optical fiber, wherein the optical fiber units are assembled in an SZ twist around the center member, and the ferromagnetic member is any one of the two ferromagnetic members. The optical cable according to any one of claims 1 to 3, wherein the optical cable is arranged between the optical fiber units. 7. A plurality of optical fiber units including the optical fiber, wherein the optical fiber units are assembled in an SZ twist around the central member, and the ferromagnetic member is a member of the optical fiber unit. The optical cable according to any one of claims 1 to 3, wherein the optical cable is fixed to any one of the optical cables. 8. The optical cable according to claim 6, wherein the optical fiber unit comprises a single-groove spacer accommodating the optical fiber. 9. The optical cable according to claim 6, wherein the optical fiber unit is a loose tube.