JP3019082B1 - Method for manufacturing optical cable and method for extracting optical fiber from optical cable - Google Patents

Abstract

An object of the present invention is to provide a method of manufacturing an optical cable capable of easily and inexpensively manufacturing an optical cable having good removability of an optical fiber after laying, in which an inverted portion can be distinguished from the outside of a jacket. And SOLUTION: A plurality of optical fibers 6i, 6o are assembled in an SZ twisted state around a central member 2 built around a metal tensile strength member 3, and the optical fibers 6i, 6o are assembled.
Of the SZ trajectory formed by the optical fibers 6i and 6o when the optical cable 1 is covered with a jacket.
The magnetized portions Z1 and Z2 are formed by magnetizing the tension member 2 at a position corresponding to o.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical cable to be laid underground, on land, aerial, or the like.
The present invention relates to a method for manufacturing an optical cable in which the periphery of each optical fiber is covered with a jacket.

[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 optical cables are laid underground, on land, overhead, etc.After the optical cable is once laid, a part of the jacket is removed or cut off at the middle part of the optical cable, and the optical cable is cut. In some cases, it is necessary to take out and branch a part of the contained optical fiber (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, the display marker forming device (core marker apparatus) is arranged downstream of the jacket cooling water tank, and From the plurality of lay plates used for twisting the optical fiber around the member, a signal indicating the reversal direction of the fold plate located at the most downstream side is extracted. 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 manufacturing method has the following problems.

In other words, the conventional method of manufacturing an optical cable uses a color tape or the like or a reverse tape attached to a holding tape to indicate the position of a reversing portion before providing a jacket around the optical fiber. Based on the operation of the plate and the like, the position of the reversing portion is detected, and then a reversing portion indicating mark is put on the extruded jacket. For this reason, in an optical cable manufactured by the conventional method, unless the reversing portion indication mark is provided,
Once the jacket is provided, it is practically impossible to determine the position of the reversing portion inside the jacket from the outside of the jacket. 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.

Accordingly, the present invention provides a method of manufacturing an optical cable that can easily and inexpensively manufacture an optical cable having good take-out of an optical fiber after laying, in which the inverted portion can be determined from the outside of the jacket. The purpose is to:

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

According to a first aspect of the present invention, there is provided a method of manufacturing an optical cable, comprising: forming a plurality of inner-layer optical fibers in an SZ twisted state around a central member having a metal tensile strength member as a center. In a method of manufacturing an optical cable in which a plurality of outer layer optical fibers are assembled in an SZ twist state around the inner layer optical fiber and the outer layer optical fiber is covered with a jacket, the inner layer S formed by the inner layer optical fiber is formed.
At a position corresponding to the inner layer inversion portion of the Z locus, a step of magnetizing the tensile strength member to form the first magnetic field portion, and at a position corresponding to the outer layer inversion portion included in the outer layer SZ locus formed by the outer layer optical fiber, Forming a first magnetized portion and a second magnetized portion that can be distinguished from each other by magnetizing the tensile strength member.

This method of manufacturing an optical cable has a multilayer structure in which a plurality of outer-layer optical fibers are assembled in an SZ-twisted state around an inner-layer optical fiber, and a plurality of outer-layer optical fibers are further assembled in an SZ-twisted state around an inner-layer optical fiber. It is for manufacturing an optical cable. As a result, an optical cable on which a very large number of optical fibers are mounted can be manufactured. Also in this case, the “optical fiber” is used as a generic term for an optical fiber core, a tape core, a tape core laminate, a pipe core, and the like.

Further, in this method of manufacturing an optical cable, the strength member incorporated in the central member is magnetized (first magnetic portion) at a position corresponding to the inner layer inversion portion of the inner layer SZ locus formed by the inner optical fiber. Then, it is magnetized at a position corresponding to the outer-layer inversion portion of the outer-layer SZ locus formed by the outer-layer optical fiber (second magnetized portion). When magnetizing the tensile strength member, the first magnetic field and the second magnetic field are made distinguishable from each other. In this case, it is preferable to make the magnetic flux density in the first magnetic part different from the magnetic flux density in the second magnetic part in order to reliably distinguish the first magnetic part from the second magnetic part. Further, the length of the first magnetized portion in the longitudinal direction of the tensile strength member,
The length of the second magnetized portion in the longitudinal direction may be different, and the magnetic flux density of the first magnetized portion and the second magnetized portion may be changed along the longitudinal direction of the tensile member.

The first magnetic field and the second magnetic field formed by magnetizing the strength member can be easily and reliably detected from the outside of the jacket in a state where they are distinguished by using a magnetic force detecting device or the like. be able to. By detecting the first magnetic field and the second magnetic field of the tensile strength member, it is possible to independently determine the positions of the inner layer reversal part and the outer layer reversal part of each optical fiber. As described above, according to the optical cable manufacturing method of the present invention, it is possible to easily and inexpensively manufacture an optical cable capable of determining the inversion of the SZ locus formed by each optical fiber from the outside of the jacket. .

Further, in the optical cable manufactured by this method of manufacturing an optical cable, the inner layer and the outer layer are partially covered at the intermediate portion of the optical cable regardless of the presence or absence of the inverted portion indicating mark indicating the position of the inverted portion. When the optical fiber is taken out and branched by removing, for example, it is possible to easily determine the most appropriate position of the reversing part in the work, and the work efficiency is improved. Therefore, this optical cable is suitable for laying in a place (for example, underground) where the surplus length of the optical cable has to be shortened because it is possible to easily find an optimum place for branching and to perform a flexible branching operation. is there.

In addition, the first magnetized portion is detected via the jacket, an inner layer reversing portion indicating mark is provided at a position corresponding to the first magnetized portion of the jacket, and the second magnetized portion is formed via the jacket. It is preferable to provide an inner-layer inversion portion indication mark and an outer-layer inversion portion indication mark that can be distinguished from each other at a position corresponding to the detection and at the position corresponding to the second magnetic field portion of the jacket.

Thus, it is possible to put an inner layer / outer layer inversion portion display mark on the jacket in a state in which the positions of the inner layer inversion portion and the outer layer inversion portion correspond exactly. Further, after the completion of the optical cable, it is possible to inspect whether or not the indicia of the inner layer / outer layer inversion portion accurately correspond to the positions of the inner layer / outer layer inversion portion. Further, since it is not necessary to apply a marking for indicating the inner layer / outer layer reversing portion before providing the jacket, the marking material (paint, various tapes, etc.) is mixed into the material of the jacket when the jacket is provided. Can be prevented.

When assembling the inner optical fiber and the outer optical fiber in the SZ twisted state, the following method may be employed.

That is, a multi-groove spacer having a plurality of SZ-shaped helical grooves formed on the outer periphery is used as a central member, an inner-layer optical fiber is accommodated in the helical groove, and a plurality of optical fiber units including an outer-layer optical fiber are used. Preferably, the optical fiber units are SZ twisted around the multi-groove spacer to be assembled. In this case, it is preferable that the optical fiber unit is formed of a single groove spacer accommodating the outer layer optical fiber.

Also, a plurality of inner layer optical fiber units each including an inner layer optical fiber and a plurality of outer layer optical fiber units including an outer layer optical fiber are used, and the inner layer optical fiber units are SZ-twisted around a central member to be assembled. SZ around the inner optical fiber unit
It is preferable to twist and collect. In this case, it is preferable that the inner-layer optical fiber unit is composed of a single-groove spacer accommodating the inner-layer optical fiber, and the outer-layer optical fiber unit is composed of a single-groove spacer accommodating the outer-layer optical fiber.
Further, it is preferable that the inner optical fiber unit and the outer optical fiber unit are loose tubes.

[0028]

The method for extracting an optical fiber from an optical cable according to the present invention according to claim 8 is a method of forming a plurality of inner-layer optical fibers in an SZ twisted state around a central member built around a metal tensile strength member. In the method of assembling and collecting a plurality of outer layer optical fibers around the inner layer optical fiber in an SZ twisted state, and taking out the optical fiber from the optical cable covering the outer layer optical fiber with a jacket, the inner layer optical fiber is formed. At the position corresponding to the inner layer inversion portion of the inner layer SZ locus, the first magnetic field portion is formed in advance by magnetizing the tensile strength member, and at the position corresponding to the outer layer inversion portion of the outer layer SZ locus formed by the outer layer optical fiber. A step of previously forming a second magnetic field that can be distinguished from the first magnetic field by magnetizing the tensile strength member; and While detecting at least one of the two magnetized portions, it is intended to include removing a portion corresponding to at least one of the first magnetized portion of the envelope and a second magnetized portion.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for manufacturing 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 an optical cable manufactured by a first embodiment of a method for manufacturing 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. This cylindrical member 2 is an LDP
It is formed of a synthetic resin such as E resin and is 14 mm
Having an outer diameter of At the center of the columnar member 2, a strength member 3 made of one steel stranded wire is embedded. This steel strand is
It is one in which seven steel wires having a diameter of 2 mm are twisted together. Nine inner-layer optical fiber units 4i are twisted in an SZ shape around the outer periphery of the cylindrical member 2 (see FIG. 3). The SZ twist pitch of each inner-layer optical fiber unit 4i (length twice as long as the distance between adjacent inversion portions) is 7
00 mm, and the SZ inversion angle φ is 275 °.

As shown in FIG. 2, the inner layer optical fiber unit 4i includes a single groove spacer 5i and a tape core laminate 6i.
(Inner-layer optical fiber). The single-groove spacer 5i is manufactured as one straight long member by using PBT resin or the like, and has a substantially U-shaped cross section. The bottom of the single groove spacer 5i and a pair of side portions define one fiber housing portion 5a capable of housing various optical fibers such as an optical fiber core, a pipe core, and a tape core.
Each dimension of the single groove spacer 5i is Bu = 6.0 mm, bu
= 4.0 mm, Bl = 5.0 mm, bl = 3.5 mm,
D = 5.0 mm and d = 4.5 mm.

The tape core laminate 6i is formed by laminating ten eight-core ribbons. Tape cored laminate 6
i is housed in the fiber housing portion 5a of the single groove spacer 5i. Then, a holding tape 7 such as a nonwoven fabric is wound around the single groove spacer 5i accommodating the tape core laminate 6i. Thereby, the single groove spacer 5i and the tape core laminate 6i are unitized. By twisting each inner-layer optical fiber unit 4i around the central member 2 in an SZ shape, each tape core laminate 6i as an inner-layer optical fiber is assembled around the cylindrical member 2 in an SZ twisted state. .

As shown in FIG. 1, each inner-layer optical fiber unit 4i twisted in an SZ shape on the outer peripheral surface of the cylindrical member 2
, A pressing tape 8 such as a nonwoven fabric is wound without any gap. And around the holding tape 8,
Sixteen outer layer optical fiber units 4o are twisted in an SZ shape. The SZ twist pitch of each outer layer optical fiber unit 4o is 900 mm, and the SZ inversion angle φ is 27 mm.
5 ゜. The outer layer optical fiber unit 4o is obtained by unitizing a single groove spacer 5o and a tape core laminate 6o (outer layer optical fiber) as in the inner layer optical fiber unit 4i.

Here, in the optical cable 1, the same single groove spacer 5o as the single groove spacer 5i shown in FIG. 2 is used. The tape core laminate 6o is also formed by laminating eight eight-core tape cores, similarly to the tape core laminate 4i. Each outer layer optical fiber unit 4o
Are twisted around each inner-layer optical fiber unit 4i in an SZ shape, so that each of the tape core laminates 6o as the outer-layer optical fibers is assembled in an SZ-twisted state around each inner-layer optical fiber unit 4i. . As described above, the optical cable 1 is further provided with a plurality of outer layer optical fibers (tape core) around the plurality of inner layer optical fibers (tape core laminate 6i) assembled in a SZ twisted state around the cylindrical member 2. The wire laminate 6o) was assembled in an SZ twisted state 2
It has a layered structure. Thereby, this optical cable 1 has:
A very large number of optical fibers (tape fiber laminates) can be mounted.

SZ around the inner layer optical fiber unit 4i
A holding tape 9 is wound around the outer optical fiber unit 4o twisted in the shape without any gap.
Around the holding tape 9, a jacket 10 having an outer diameter of 41 mm formed of low-density polyethylene is further provided. Thereby, the inside of the optical cable 1 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 (a), each inner layer optical fiber unit 4i
The (tape core laminate 6i) forms a locus extending in an SZ shape (hereinafter referred to as “inner layer SZ locus”). This inner layer SZ
The locus includes a portion (hereinafter, referred to as “inner layer inversion portion Ri”) in which the tape core laminate 6i is inverted from S twist to Z twist or from Z twist to S twist. In this case, the inversion portion R of the SZ locus formed by the inner-layer-side tape core laminate 6i.
i are located on the same circumference centered on the central axis of the optical cable 1.

Similarly, inside the jacket 10 of the optical cable 1, as shown in FIG. 3 (b), each outer-layer optical fiber unit 4o (tape core laminate 6o) extends in an SZ shape (hereinafter referred to as "ZZ"). Outer layer SZ locus ”). In the outer layer SZ locus, the tape core laminate 6o is shifted from S twisted to Z
A portion where the twist is reversed or a portion where the Z twist is reversed to the S twist (hereinafter, referred to as “outer layer reversed portion Ro”) is included. The reversal portion Ro of the SZ locus formed by the outer-layer-side tape core laminate 6o is also:
The optical cables 1 are located on the same circumference around the central axis.

As described above, the plurality of optical fiber units 4i and 4o (tape fiber laminates 6i and 6
o), each of the tape core laminates 6i, 6o corresponds to the length of the optical cable 1 (center member 2).
Is long. Therefore, each optical fiber unit 4i,
If the jacket 10 near the inversions Ri and Ro of the SZ locus formed by 4o is removed, the optical fiber (tape core 6
i, 6o) can be smoothly removed from the optical cable 1 without excessive pulling.

Based on these facts, in this optical cable 1, as shown in FIG.
In order to determine Ro from the outside of the jacket 10, the cylindrical member 2
Is magnetized at a position corresponding to the inner-layer inversion portion Ri of the inner-layer SZ locus formed by the inner-layer optical fiber unit 4i (tape core laminate 6i).
The tensile strength member 3 is magnetized at a position corresponding to the outer-layer inversion portion Ro of the outer-layer SZ locus formed by the outer-layer optical fiber unit 4o (tape core laminate 6o). Strength member 3
The first magnetic field Z1 and the second magnetic field Z2 formed by magnetizing are distinguished from each other by using a magnetic force detection device (for example, a magnetic force detector FS201 manufactured by Macome Laboratory Co., Ltd.). Thus, it is possible to detect easily and reliably from the outside of the jacket 10.

In addition, the first magnetic part Z1 and the second magnetic part Z2
Are distinguishable from each other. This optical cable 1
In order to make it possible to distinguish between the first magnetic field Z1 corresponding to the inner layer reversal Ri and the second magnetic field Z2 corresponding to the outer layer reversal Ro, the magnetic flux density (average magnetic flux density) in the first magnetic field Z1 and And the magnetic flux density (average magnetic flux density) in the second magnetic zone Z2. Further, the magnetic flux densities of the first magnetic part Z1 and the second magnetic part Z2 change along the longitudinal direction of the tensile strength member 3, respectively. Further, in the optical cable 1, the first magnetic portion Z in the longitudinal direction of the tensile member 3 is provided.
1 and the length of the second magnetic zone Z2.

That is, as shown in FIG. 4, the magnetic flux density in both the first magnetic part Z1 and the second magnetic part Z2 is
The peak is located at the center in the longitudinal direction of the first magnetic portion Z1 and the second magnetic portion Z2, and is distributed so as to gradually decrease as going to both ends. And the inner layer inversion part R
The average magnetic flux density of the first magnetic zone Z1 corresponding to i is 100
0 G (Gauss), and the average magnetic flux density of the second magnetic zone Z2 corresponding to the outer layer inversion portion Ro is 2000 G (Gauss). Also. The length of the first magnetized portion Z1 is 12 mm, and the length of the second magnetized portion is 6 mm. As a result, the first magnetic field Z1 and the second magnetic field Z2 can be reliably distinguished, so that each of the tape core laminates 6i, 6o is provided.
The positions of the inner layer inversion portion Ri and the outer layer inversion portion Ro of the (inner / outer layer optical fiber) can be determined independently from the outside of the jacket 10.

Here, in order to increase the work efficiency when taking out and branching the optical fiber by removing a part of the jacket at the middle part of the optical cable, the longer the SZ twist pitch of the optical fiber, the more the reverse. It is necessary to accurately determine the position of the part. In this optical cable 1, the SZ twist pitch Po (90 mm) of the outer layer optical fiber unit 4o is larger than the SZ twist pitch Pi (700 mm) of the inner layer optical fiber unit 4i.
0 mm) is long.

Therefore, in the optical cable 1, the second magnetic field portion Z2 corresponding to the outer layer inversion portion Ro of the outer layer optical fiber unit 4o having a long SZ twist pitch Po has the second magnetic field portion Z2 corresponding to the inner layer inversion portion Ri of the inner layer optical fiber unit 4i. The magnetic flux density (average magnetic flux density) is set to be larger than that of the one-zone magnetic portion Z1. In the longitudinal direction of the optical cable 1, the length of the second magnetized portion Z2 is shorter than the length of the first magnetized portion Z1. As a result, the outer layer inversion portion Ro is
Can be detected with high sensitivity. Therefore, the reversal part Ro of the outer layer optical fiber unit 4o having the long SZ twist pitch Po can be easily and reliably determined.

Further, a tensile member 3 built in the cylindrical member 2
When the tape core laminates 6i and 6o are taken out from the optical cable 1 by preliminarily forming the first magnetized portion and the second magnetized portion by magnetizing the following, the following method can be adopted. Becomes That is, first, at the place where the optical cable 1 is laid, at least one of the first magnetic part Z1 and the second magnetic part Z2 is detected via the jacket 10. In this case, a magnetic force detecting device that is small, light, and easy to carry (for example,
A Gauss meter GM-003 manufactured by Denki Kogyo Kogyo KK may be used. Then, a portion corresponding to at least one of the first magnetic portion Z1 and the second magnetic portion Z2 of the jacket 10 is removed.

In this way, when the optical fiber (tape core laminates 6i, 6o) is taken out and branched by removing a part of the jacket 10 at the intermediate portion of the optical cable 1, the inversion indicating the position of the inversion portion is performed. Regardless of the presence or absence of the part indication mark, the most appropriate reversing parts Ri and Ro for the operation for both the inner layer and the outer layer
Can be easily determined. 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.

As described above, the first magnetic portion Z1 and the second magnetic portion Z2 can be easily detected from the outside of the jacket 10. Therefore, in the optical cable 1, an inner layer reversing portion display mark Mi indicating the position of the inner layer reversing portion Ri on the jacket 10 using the first magnetic portion Z 1 and the second magnetic portion Z 2.
And an outer layer reversing portion display mark Mo indicating the position of the outer layer reversing portion Ro.
Are provided. Accordingly, when the tape core laminates 6i and 6o are taken out and branched by removing a part of the jacket at the intermediate portion of the optical cable 1, for both the inner layer and the outer layer, the most appropriate reversing part Ri for the operation. , Ro can be more easily determined, so that the working efficiency is greatly improved.

As shown in FIG. 5C, on the surface of the jacket 10 of the optical cable 1, each inner-layer optical fiber unit 4i
Inner layer inversion portion display mark M indicating a position of inner layer SZ locus formed by (tape core laminate 6i) corresponding to inner layer inversion portion Ri.
i is provided. Similarly, on the surface of the jacket 10, an outer-layer inversion portion indication mark Mo indicating a position corresponding to the outer-layer inversion portion Ro included in the outer-layer SZ locus formed by the outer-layer optical fiber unit 4o is provided.

In this optical cable 1, the letter “I” of the alphabet is marked on the outer cover 10 by using a printing device or the like as the inner layer inversion portion display mark Mi.
In addition, the letter “O” of the alphabet is marked on the outer cover 10 as the outer layer inversion portion display mark Mo.
Thereby, the inner layer reversal part display mark Mi and the outer layer reversal part display mark Mo can be distinguished from each other. It is preferable that the inner layer reversal portion display mark Mi and the outer layer reversal portion display mark Mo be provided over the entire circumference of a concentric circle centered on the central axis of the optical cable 1 in consideration of the discriminability during operation.

Further, like the optical cable 1, the SZ twist pitch Pi (700 m) of the inner layer optical fiber unit 4i is used.
m) is different from the SZ twist pitch Po (900 mm) of the outer layer optical fiber unit 4o, FIG.
As shown in the right side of (a) to (c), there may be a portion where the inner layer inversion portion Ri and the inner layer inversion portion Ro overlap. For this reason,
In the optical cable 1, a character “I” indicating the inner layer inversion portion Ri and an “O” indicating the outer layer inversion portion Ro are provided at portions corresponding to the portions where the inner layer inversion portion Ri and the inner layer inversion portion Ro of the jacket 10 overlap. And the letters are alternately marked.

As a result, it is possible to find a place where the inner layer inversion portion Ri and the outer layer inversion portion Ro are close to or coincide with each other based on the inner layer inversion portion display mark Mi and the outer layer inversion portion display mark Mo. For example, when it is desired to take out the inner-layer tape core laminate 6i from the optical cable 1, it is naturally necessary to also take out the outer-layer optical fiber unit 4o (tape core laminate 6o) once. Inner layer inversion part display mark Mi and outer layer inversion part display mark Mo
It is possible to remove the jacket 10 at a location where the cable approaches or coincides with each other, and it is possible to significantly improve the work efficiency when branching after laying the cable.

As described above, in the optical cable 1, when any one of the tape core laminates 6i, 6o is taken out and branched by removing a part of the jacket 10 at an intermediate portion thereof, the inner layer inversion portion Ri By visually observing both the outer layer inversion portion Ro and the outer layer inversion portion Ro from the outside of the jacket 10 of the optical cable 1, it is possible to determine each of them independently. Therefore, when removing the jacket 10 for branching after laying the optical cable 1,
Since it is possible to easily determine the most appropriate positions of the reversing portions Ri and Ro for both the inner layer and the outer layer, the working efficiency is extremely improved.

As shown in FIG. 6C, a mark (symbol) may be used as the inner layer inversion portion display mark Mi and the outer layer inversion portion display mark Mo. In the example shown in FIG. 6, an elongated metal tape 12 (for example, having a length of 30 mm) is provided at a position corresponding to the inner layer inversion portion Ri of the jacket 10 as an inner layer inversion portion display mark Mi.
mm and a copper tape having a width of about 5 mm) are attached along the longitudinal direction of the optical cable 1. Meanwhile, the jacket 1
At a position corresponding to the outer layer reversal portion Ro of 0, an elongated metal tape 12 is attached as an outer layer reversal portion indication mark Mo so as to be orthogonal to the longitudinal direction of the optical cable 1.

As shown on the right side in FIG. 6 (c), a portion corresponding to a portion where the inner-layer inversion portion Ri and the outer-layer inversion portion Ro of the jacket 10 overlap with each other is an optical cable 1 as an inner-layer inversion portion display mark Mi. On the metal tape 12 adhered to the jacket 10 along the longitudinal direction of the optical cable 1, another metal tape 12 is perpendicular to the longitudinal direction of the optical cable 1 as an outer layer inversion portion display mark Mo ( (In a cross).

Even if such a configuration is adopted, both the inner layer inversion portion Ri and the outer layer inversion portion Ro can be independently determined from the outside of the jacket 10 of the optical cable 1, and the optical cable 1 is laid. When the jacket 10 is removed to perform branching after the branching, the most appropriate reversing part Ri,
Since the position of Ro can be easily determined, work efficiency is extremely improved. In addition, the inner layer reversal part display mark Mi
The shape and the like of the outer-layer inversion portion display mark Mo are not limited at all, as long as they can be distinguished from each other, and arbitrary characters, symbols, and markers can be used.

Next, a first embodiment of the method for manufacturing an optical cable according to the present invention will be described in detail.

In manufacturing the optical cable 1, first, the inner-layer optical fiber unit 4 i is twisted around the cylindrical member 2 using the optical fiber twisting line 50 shown in FIG. In this case, the columnar member 2 having the built-in strength member 3 is wound around a core winding reel 51. Also,
The inner optical fiber unit 4i is wound around the optical fiber unit winding reel 52 in advance. Then, from the core winding reel 51 and the optical fiber unit winding reel 52, one cylindrical member 2 and a plurality of (in this case, nine) inner layer optical fiber units 4i are supplied to the inversion plate group 53. I do.

Each of the inner-layer optical fiber units 4i is gradually twisted into an SZ shape by each of the reversing eye plates 54 that rotate independently while rotating alternately within a predetermined reversing angle. A thread and the like for temporarily fixing each inner-layer optical fiber unit 4i are wound around the inner-layer optical fiber unit 4i twisted around the cylindrical member 2 by a holding-winding device 55, and a holding tape 8 Is wound without gaps. Thereby, each tape core laminate 6i included in each inner layer optical fiber unit 4i is
Assemble around the cylindrical member 2 in an SZ twisted state.

Further, an encoder (not shown) is connected to the inverting plate 54a located at the most downstream position among the inverting plates 54. From this encoder, a reversing plate 54a
Is supplied to the control computer 56. Further, a degaussing device 57 disposed downstream of the presser winding device 55 is connected to the control computer 54. Downstream of the degaussing device 57, the magnetizing device 5
8 (for example, a capacitor-type magnetizer SCB-20 manufactured by Nippon Electromagnetic Instruments Co., Ltd.). This magnetizing device 58
Is also connected to the control computer 56.

The control computer 56 includes a reversing board 54a.
Performs a predetermined operation based on the inverted signal received from
The timing at which the inner-layer inversion portion Ri of the SZ locus formed by each of the inner-layer optical fiber units 4i twisted around the cylindrical member 2 reaches below the magnetizing device 58 is determined. Then, the control computer 56 activates the magnetizing device 58 when the inner layer reversing part Ri reaches below the magnetizing device 58. When the magnetizing device 58 is operated, the inner layer S formed by each inner layer optical fiber unit 4i (tape core laminate 6i) is formed.
At a position corresponding to the inner layer inversion portion Ri of the Z locus, the tensile strength member 3
Are magnetized to form the first magnetic zone Z1. Also, before the magnetization of the strength member is performed by the magnetization device 58, the magnetism remaining in the strength member 3 is removed by the demagnetization device 57. Therefore, the efficiency of magnetization by the magnetization device 58 is improved. Semi-finished product H1 in the state where the first magnetic zone Z1 is formed
Is wound on a take-up reel 59A.

Next, using the optical fiber twisting line 50 shown in FIG.
Is twisted around each inner layer optical fiber unit 4i.
In this case, as shown in FIG. 7, the take-up reel 59A is replaced with the core take-up reel 51, and the optical fiber unit take-up reel 52 is provided with the outer layer optical fiber unit 4o.
(In the optical cable 1, both are the same). Then, the inverting eyeplate group 53 is operated to twist each outer-layer optical fiber unit 4o around each inner-layer optical fiber unit 4i. And the presser winding device 55
Thereby, the holding tape 9 is wound around the outer optical fiber unit 4o without any gap. Thereby, the respective tape core laminates 6o included in the respective outer layer optical fiber units 4o gather around the respective inner layer optical fiber units 4i in an SZ twisted state.

The degaussing device 57 and the magnetizing device 58 are operated by the control computer 56. This allows
Outer layer optical fiber unit 4o (tape core laminate 6o)
At the position corresponding to the outer layer reversal part Ro included in the outer layer SZ trajectory formed by the second magnetic field part Z2
Is formed. When forming the second magnetized portion Z, the intensity, pattern, etc. of the magnetization by the magnetizing device 58 are set at the time of forming the first magnetized portion Z1 so that the second magnetized portion Z2 can be distinguished from the first magnetized portion Z1. Keep it different. The semi-finished product H2 in a state where both the first magnetic portion Z1 and the second magnetic portion Z2 are formed is taken up on the take-up reel 59B.

When the twisting of the inner-layer optical fiber unit 4i and the outer-layer optical fiber unit 4o with respect to the cylindrical member 2 is completed, the jacket 10 is provided on the semifinished product H2 using the jacket forming line 60 shown in FIG. . In this case, FIG.
As shown in (5), the semi-finished product H2 is supplied to the jacket extrusion device 61 from the take-up reel 59B. From the jacket extrusion device 61, an optical cable in which the jacket 10 is integrated around the semi-finished product H2 is extruded. This optical cable is connected to the jacket cooling water tank 6.
2, whereby the jacket 10 is cooled and solidified. This state (the state where the inverted part display mark is not attached)
May be handled as a finished product. Accordingly, it is possible to easily and inexpensively manufacture an optical cable capable of determining the inverted portion of the SZ locus formed by each optical fiber from the outside of the jacket.

When the inner layer reversal portion display mark Mi and the outer layer reversal portion display mark Mo are provided on the jacket 10, as shown in FIG. 8, the magnetic force detecting device 63 is provided downstream of the jacket cooling water tank 62.
(For example, a magnetic force detector FS20 manufactured by Macome Laboratory Inc.)
Place 1). The magnetic force detecting device 63 can detect the above-described first magnetic part Z1 and second magnetic part Z2 via the jacket 10. When detecting the first magnetic portion Z <b> 1 and the second magnetic portion Z <b> 2, the magnetic force detection device 63 gives a detection signal indicating that to the control computer 64. Further, in the control computer 64, a display mark forming apparatus which is disposed downstream of the magnetic force detection device 63 and can arrange the inner layer reversal portion display mark Mi and the outer layer reversal portion display mark Mo on the jacket 10 is provided. 65 are connected.

As shown in FIG. 5, the inner layer inversion portion display mark Mi
When a character is used as the display mark Mo for the outer layer inversion portion, a printing device (for example, an inkjet printer manufactured by Imaj) is used as the display mark forming device 65. In this case, it is preferable to arrange three printing devices in order to provide the inner layer reversal portion display mark Mi and the outer layer reversal portion display mark Mo all around the outer cover 10. In addition, as shown in FIG. 6, when a mark using a metal tape is attached as the inner layer reversing portion display mark Mi and the outer layer reversing portion display mark Mo, two tape sticking devices (inner layer reversing device) are used as the display mark forming device 65. It is preferable to use one for each of the inversion portion display mark Mi and the outer layer inversion portion display mark Mo.

The control computer 64 controls the magnetic force detecting device 6
A predetermined calculation is performed on the basis of the detection signal received from No. 3 to determine a timing at which the first magnetized portion Z1 or the second magnetized portion Z2 (if both overlap, both arrive below the display mark forming device 65). . When the first magnetic part Z1 or the second magnetic part Z2 reaches below the display mark forming device 65, the control computer 64 causes the display mark forming device 65
Activate

The display mark forming device 65 attaches an inner layer reversal portion display mark Mi (for example, the character “I”) on the jacket 10 covering the vicinity of the first magnetic portion Z1 and the vicinity of the second magnetic portion Z2. An outer layer reversing portion display mark Mo (for example, a character of “O”) is attached on the covering jacket 10. Further, the first magnetic part Z1 and the second magnetic part Z
On the jacket 10 covering the portion where 2 overlaps, both the inner layer reversal portion display mark Mi and the outer layer reversal portion display mark Mo (for example, the character of “I” and the character of “O” are alternately provided). Thus, the inner / outer-layer inversion portion display mark M is displayed on the jacket 10 in a state in which the inner / outer-layer inversion portions Ri and Ro correspond exactly to each other.
i and Mo can be added. In this way,
The optical cable 1 is completed. The completed optical cable 1 is taken up on a take-up reel 66.

As described above, the first magnetic field Z1 and the second magnetic field Z formed by magnetizing the tension member 3 are formed.
2 can be easily and reliably detected from the outside of the jacket 10 in a state where they are distinguished by using the magnetic force detection device 63 or the like. Then, the first magnetic portion Z1 of the tensile strength member 3
By detecting the second magnetic field portion Z2 and the position of the inner layer / outer layer inversion portions Ri and Ro of the optical fiber units 4i and 4o, respectively, it is possible to determine the position of each of them independently. As described above, according to the method for manufacturing an optical cable according to the present invention, the optical cable 1 capable of distinguishing the inversion parts Ri and Ro of the SZ trajectory formed by the optical fiber units 4i and 4o from the outside of the jacket 10 can be easily and lowly manufactured. It can be manufactured at a low cost.

After the optical cable 1 is completed, the inner / outer layer inversion portion display marks Mi and Mo are displayed as inner / outer layer inversion portions Ri and Mo.
It is also possible to check whether or not it exactly corresponds to the position of Ro. Further, since it is not necessary to apply a marking for indicating the inner layer / outer layer inversion portions Ri and Ro before providing the outer cover 10, when the outer cover 10 is provided, a marking material (paint, various tapes, etc.) is used. Can be prevented from being mixed into the material.

When the outer layer 10 is provided with the inner layer reversing portion indicating mark Mi and the outer layer reversing portion indicating mark Mo, the first magnetized portion Z1 is provided.
And the second magnetic portion Z2 do not necessarily need to be formed so as to correspond to all the inner / outer-layer inversion portions Ri and Ro. That is, the inversion portions Ri and Ro appear at predetermined intervals (１ ／ Pi, × Po). Therefore, even if the first / second magnetized portions Z1 and Z2 are formed in correspondence with the inversion portions Ri and Ro every predetermined number,
Inverted portion display marks Mi, M corresponding to the inverted portions Ri, Ro, respectively.
It is possible to add o. In this case, the first / second magnetic portions Z1, Z2 detected by the magnetic force detecting device 63
And the positions of the reversing portions Ri and Ro may be determined based on the positions of the SZ twist pitches Pi and Po. This is particularly effective when it takes a long time to prepare the magnetizing device for operation.

[Second Embodiment] FIG. 9 is a sectional view showing an optical cable manufactured by a second embodiment of the method for manufacturing an optical cable according to the present invention. The optical cable 20 shown in the figure has the same configuration as the optical cable 1 of the first embodiment using an inner loose tube 24i and an outer loose tube 24o as an inner optical fiber unit and an outer optical fiber unit. An extremely large number of optical fibers (tape ribbons) can be mounted on the optical cable 20 as well.

As shown in FIG. 10, the inner loose tube 24i is a tube 2 made of polyethylene.
5 (outer diameter 6.0 mm, inner diameter 4.5 mm) and tube 2
5 is a tape core laminated body 26i (inner layer optical fiber) accommodated in the inside. The tape core laminate 26i has 8
It is obtained by laminating 10 core tapes. Also,
The inside of the tube 25 is filled with grease 27 serving as a cushioning material together with the tape core laminate 26i. The outer layer loose tube 24o is the same as the inner layer loose tube 24i, and includes a tube 25 and a tape core laminate 26o (outer layer optical fiber).

At the center of the optical cable 20, a long cylindrical member 22 (LDPE
(Made of resin, diameter 14 mm). Column member 2
Is embedded with a tensile strength member 23 made of a single steel stranded wire. This steel twisted wire is also one in which seven steel wires each having a diameter of 2 mm are twisted together. In the tensile member 23,
Similarly to the optical cable 1, a first magnetic part Z1 and a second magnetic part Z2 are formed (see FIG. 3). Nine inner layer loose tubes 24i are twisted in an SZ shape on the outer periphery of the columnar member 22, respectively. Each inner loose tube 2
4i has an SZ twist pitch of 700 mm and an SZ inversion angle φ of 275 °.

As shown in FIG. 9, a holding tape 28 made of non-woven fabric or the like is wound without any gap around each inner layer loose tube 24i twisted in an SZ shape on the outer peripheral surface of the cylindrical member 2. Around the holding tape 28, 16 outer layer loose tubes 24o are twisted in an SZ shape. The SZ twist pitch of each outer layer loose tube 24o is 900 mm, and the SZ inversion angle φ is 275 °. A holding tape 29 is wound around each outer loose tube 24o without any gap. A jacket 21 having an outer diameter of 41 mm and made of low-density polyethylene is further provided around the holding tape 29. The outer cover 21 has a single tear string 21a built therein. Further, on the surface of the jacket 21 of the optical cable 20, similarly to the optical cable 1 of the first embodiment, an inner layer inversion portion display mark Mi and an outer layer inversion portion display mark Mo (see FIG. 3) are provided.

When the optical cable 20 is manufactured, the loose tubes 24i and 24o may be twisted around the cylindrical member 22 using the optical fiber twisting line 50 shown in FIG. That is, the loose tubes 24i and 24o are wound around the optical fiber unit winding reel 52, and one cylindrical member 22 and a plurality (15 in this case) of loose tubes 24i, 2
If 4o is supplied, the optical cable 20 can be manufactured in the same manner as the optical cable 1 of the first embodiment.

[Third Embodiment] FIG. 11 is a sectional view showing an optical cable manufactured by a third embodiment of the method for manufacturing an optical cable according to the present invention. The optical cable 30 shown in FIG.
Instead, a multi-core spacer 32 is used, and the multi-layer spacer 32 accommodates a tape core laminate as an inner-layer optical fiber. An extremely large number of optical fibers (tape core laminate) can be mounted on the optical cable 30 as well.

At the center of the long multi-groove spacer 32 (made of HDPE resin, outer diameter 24 mm), a tensile strength member 33 composed of one steel stranded wire is embedded. This steel strand also has a diameter of 2
It is one in which 7 mm steel wires are twisted together.
Like the optical cable 1, the tensile member 33 has a first magnetic part Z1 and a second magnetic part Z2 (see FIG. 3). Further, on the outer periphery of the multi-groove spacer 32, ten SZ-shaped spiral grooves 37 are formed. The depth of each spiral groove 37 is 4.3 mm, and the upper width (corresponding to bu in FIG. 2) is 4.2.
mm, the bottom width is 3.2 mm. Furthermore, each spiral groove 37
Has an SZ pitch of 700 mm and an SZ inversion angle φ of 2
75 °.

Each spiral groove 37 is provided with an eight core fiber ribbon.
The tape core laminated body 36i (inner optical fiber) in which zero sheets are laminated is housed. As a result, the tape core laminate 36i gathers around the multi-groove spacer 32 as the central member in an SZ twisted state. A holding tape 38 such as a nonwoven fabric is wound around the multi-groove spacer 32 in which the tape core laminate 36i is accommodated in each spiral groove 37 without any gap. Then, around the holding tape 38, 15
The outer layer optical fiber unit 34 is twisted in an SZ shape. The SZ twist pitch of each outer layer optical fiber unit 34 is 900 mm, and the SZ inversion angle φ is 275 °.

The outer layer optical fiber unit 34 is formed by unitizing a single groove spacer 35 and a tape core laminate 36o (outer layer optical fiber). Here, in the optical cable 30, the single groove spacer 35 is the same as the single groove spacer 5i shown in FIG. The tape core laminate 36o is also formed by laminating ten eight-core tape cores, similarly to the tape core laminate 36i. Each outer layer optical fiber unit 34 is provided with SZ around the multi-groove spacer 32.
By twisting in a shape, each tape core laminate 36o
Will be assembled around the multi-groove spacer 32 in an SZ twisted state.

A holding tape 39 is wound around each outer optical fiber unit 34 without any gap.
Around the holding tape 9, a jacket 31 further formed of low-density polyethylene and incorporating a tear string 31a is provided.
(Outer diameter of 39 mm). Further, on the surface of the jacket 31 of the optical cable 30, similarly to the optical cable 1 of the first embodiment, an inner layer inversion portion display mark Mi and an outer layer inversion portion display mark Mo are provided.

In manufacturing the optical cable 30, first, the multi-groove spacer 32 is manufactured using the spacer manufacturing line 40 shown in FIG. In this case, as shown in FIG. 12, the tensile strength member 33 is wound around the take-up reel 41.
Then, from the take-up reel 41, the tensile strength member 33 is supplied to a spacer extruder 42 having a built-in reversing die (not shown). The tensile strength member 33 is extruded together with the molten HDPE resin by the spacer extruder 42. This semi-finished product is cooled in the cooling water tank 43 and solidified.

A degaussing device 45 and a magnetizing device 46 controlled by a control computer 44 are arranged downstream of the cooling water tank 43. The control computer 44 includes:
An inversion signal indicating the angular velocity of the inversion die is sent from the spacer extruder 42 via the encoder. The control computer 44 operates the degaussing device 45 and the magnetizing device 46 based on the inversion signal. Thereby, the tensile strength member 33 is magnetized at a position corresponding to the reversal portion of the spiral groove 37 formed in the spacer 32 (corresponding to the reversal portion Ri of the inner layer SZ locus formed by the inner layer tape core laminate 36i). Thus, a first magnetic zone Z1 is formed. The multi-groove spacer 32 in the state where the first magnetic zone Z1 is formed is taken up by the take-up reel 47.

After the multi-groove spacer 32 is manufactured by the spacer manufacturing line 40, the tape core laminate 36i is accommodated in each spiral groove 37 of the multi-groove spacer 32. Then, using the optical fiber twisting line 50 shown in FIG. 7, the outer layer optical fiber unit 34 is twisted in an SZ shape around the multi-groove spacer 32 and included in the outer layer SZ locus formed by the outer layer optical fiber unit 34. At the position corresponding to the outer layer reversal portion Ro to be formed, the tensile strength member 33 is magnetized to form the second magnetized portion Z2. Further, the jacket 31 is provided around the outer optical fiber unit 34 by using the jacket forming line 60 shown in FIG. 8, and the inner / outer layer inversion portion display mark Mi,
Mo is disposed on the jacket 31.

[Fourth Embodiment] FIG. 13 is a sectional view showing an optical cable manufactured according to a fourth embodiment of the method for manufacturing an optical cable according to the present invention. In the center of the optical cable 70 shown in the figure, a long cylindrical member 72 serving as a central member is arranged. This cylindrical member 72 is
It is made of synthetic resin such as LDPE resin,
It has an outer diameter of 5 mm. At the center of the columnar member 72, a tensile strength member 73 made of one steel stranded wire is embedded. This steel stranded wire is one in which seven steel wires having a diameter of 2 mm are stranded together. Fifteen optical fiber units 74 are twisted in an SZ shape around the outer periphery of the cylindrical member 72 (see FIG. 14).

The optical fiber unit 74 is the same as the optical fiber unit 4 shown in FIG. 2, in which a single-core spacer 75 accommodates a tape core laminate 76 as an optical fiber. S of each optical fiber unit 74
The Z twist pitch (length twice as long as the distance between adjacent inversion portions) is 900 mm, and the SZ inversion angle φ is 275 °. A holding tape 79 such as a nonwoven fabric is wound around the optical fiber units 74 twisted in an SZ shape around the outer peripheral surface of the cylindrical member 72 without any gap. In addition, a jacket 71 having an outer diameter of 41 mm formed of low-density polyethylene is provided around the holding tape 79. Thereby, the inside of the optical cable 71 is protected. In addition, one tear string 71a is built in the jacket 71.

In this optical cable 70, in order to determine the reversal portion R from the outside of the jacket 71, as shown in FIG. 14B, a tensile member 73 built in the columnar member 72 is connected to the optical fiber unit 74 ( The magnetized portion Z is formed by magnetizing at a position corresponding to the inversion portion R of the SZ locus formed by the tape core laminate 76). This makes it possible to adopt the following method for taking out the tape core laminate 76 from the optical cable 70. That is,
First, at the place where the optical cable 70 is laid, the magnetized portion Z is detected via the jacket 71. In this case, a magnetic force detecting device that is small and lightweight and easy to carry (for example, Electric Magnetic Industry Co., Ltd.)
And a Gauss meter GM-003) manufactured by Toshiba Corporation. Then, a portion corresponding to the magnetized portion Z of the jacket 71 is removed.

In this way, when the optical fiber (tape core laminate 76) is taken out and branched by removing a part of the jacket 71 at the intermediate portion of the optical cable 70, the reversing portion indicating the position of the reversing portion R is provided. Regardless of the presence or absence of the display mark, it is possible to easily determine the most appropriate position of the reversing portion R in the work. As described above, since the optical cable 70 can easily find an optimum location for branching and enables a flexible branching operation, the optical cable 70 is laid in a place (for example, underground) where the extra length of the optical cable must be shortened. It is suitable for. FIG.
As shown in (c), a reversal portion display mark M indicating the position of the reversal portion R may be provided on the outer cover 71 using the magnetic portion Z.

When this optical cable 70 is manufactured, the optical fiber unit 74 is twisted around the cylindrical member 72 using the optical fiber twisting line 50 shown in FIG. 6, and the SZ locus formed by the optical fiber unit 74 is formed. The magnetized strength member 73 is formed at a position corresponding to the reversal portion R included in the magnetic field to form a magnetized portion Z. Further, a jacket 71 is provided around the optical fiber unit 74 using the jacket forming line 60 shown in FIG. 8, and an inversion portion display mark M is provided on the jacket 71.

[Fifth Embodiment] FIG. 15 is a sectional view showing an optical cable manufactured by a fifth embodiment of the method for manufacturing an optical cable according to the present invention. The optical cable 80 shown in the figure has the same configuration as the above-described optical cable 70 using a loose tube 84 as the optical fiber unit 4. The loose tube 84 is similar to the loose tube 24 included in the optical cable 20 of the second embodiment. The optical cable 80 is connected to the loose tube 8
4, the optical cable 70 can be manufactured by the same method as the optical cable 70 of the fourth embodiment.

At the center of the optical cable 80, a long cylindrical member 82 (made of HDPE resin, 25 mm in diameter) serving as a central member is arranged. At the center of the columnar member 82, a tensile strength member 83 made of one steel stranded wire is embedded. This steel twisted wire is also one in which seven steel wires each having a diameter of 2 mm are twisted together. Fifteen loose tubes 84 are twisted in an SZ shape on the outer periphery of the columnar member 82, respectively. The SZ twist pitch of each loose tube 24 is 900 mm, and the SZ inversion angle φ is 275 °. A presser winding tape 89 is wound around each loose tube 84 without a gap. Presser tape 89
Is further provided with a jacket 81 having an outer diameter of 41 mm formed of low-density polyethylene. In addition, one tear string 81a is built in the jacket 21.

In this optical cable 80, the reversing part R
The strength member 83 built in the cylindrical member 82 is connected to the optical fiber unit 8
The magnetized portion Z is formed by magnetizing at a position corresponding to the reversal portion R of the SZ locus formed by the SZ 4 (FIG. 14).
(B)). In addition, by using the magnetized portion Z, an inversion portion display mark M indicating the position of the inversion portion R is provided on the outer cover 81 (see FIG. 14C).

[Sixth Embodiment] FIG. 16 is a sectional view showing an optical cable manufactured by a sixth embodiment of the method for manufacturing an optical cable according to the present invention. Optical cable 9 shown in FIG.
0 corresponds to the optical cable 30 of the third embodiment in which the outer-layer optical fiber unit 34 is omitted. That is,
The multi-groove spacer 92 used for the optical cable 90 includes:
It is the same as the multi-groove spacer 32 included in the optical cable 30 of the third embodiment.
Is built-in. Each spiral groove 94 of the multi-groove spacer 92 accommodates a tape core laminated body 96 (optical fiber) in which ten 8-core tape cores are stacked and bundled. Around the multi-groove spacer 92 in which the tape core laminate 96 is accommodated in each spiral groove 94, a holding tape 95 such as a nonwoven fabric is provided.
Are wound without any gaps. Around the presser winding tape 95, a jacket 91 (outer diameter 29) which is further formed of low-density polyethylene and incorporates a tear string 91a.
mm) is provided.

In the optical cable 90, the reversing part R
The strength member 93 built in the cylindrical member 92 is discriminated from the outside of the jacket 91 by the tensile strength member 93.
The magnetized portion Z is formed by magnetizing at a position corresponding to the reversal portion R of the SZ locus formed by the SZ 4 (FIG. 14).
(B)). In addition, by using the magnetized portion Z, an inversion portion display mark M indicating the position of the inversion portion R is provided on the outer cover 91 (see FIG. 14C).

When this optical cable 90 is manufactured, FIG.
2, a multi-groove spacer 9 having a built-in strength member 93 provided with a first magnetic section Z is provided.
2 is manufactured. Then, after the tape core laminated body 96 is accommodated in each spiral groove 94, a jacket 91 is provided around the multi-groove spacer 92 by using the jacket forming line 60 shown in FIG. It is arranged on the jacket 91.

[0095]

According to the optical cable manufacturing method of the present invention, the following effects can be obtained. That is,
By magnetizing the tensile strength member at a position corresponding to the reversal part of the SZ locus formed by the optical fiber to form a magnetized part,
The inverted portion can be distinguished from the outside of the jacket, and a method of manufacturing an optical cable that can easily and inexpensively manufacture an optical cable with good optical fiber take-out after laying can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an optical cable manufactured according to a first embodiment of an optical cable manufacturing method 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 schematic diagram for explaining a first magnetized portion and a second magnetized portion provided in the optical cable of FIG. 1;

FIG. 4 is a schematic diagram for explaining a distribution state of a magnetic flux density in a first magnetic field and a second magnetic field.

FIG. 5 is a schematic diagram for explaining an inner layer reversing portion indicating mark and an outer layer reversing portion indicating mark provided on the optical cable of FIG. 1;

FIG. 6 is a schematic diagram showing another embodiment of the inner layer reversal portion display mark and the outer layer reversal portion display mark.

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

FIG. 8 is a schematic view showing an optical cable production line for producing the optical cable of FIG.

FIG. 9 is a sectional view showing an optical cable manufactured according to a second embodiment of the method for manufacturing an optical cable according to the present invention.

FIG. 10 is a sectional view showing an optical fiber unit included in the optical cable of FIG. 9;

FIG. 11 is a sectional view showing an optical cable manufactured by a third embodiment of the method for manufacturing an optical cable according to the present invention.

FIG. 12 is a schematic diagram showing an optical cable production line for producing the optical cable of FIG.

FIG. 13 is a sectional view showing an optical cable manufactured according to a fourth embodiment of the method for manufacturing an optical cable according to the present invention.

FIG. 14 is a schematic diagram for explaining a magnetized portion and a reversal portion display mark of the optical cable of FIG. 13;

FIG. 15 is a sectional view showing an optical cable manufactured by a fifth embodiment of the method for manufacturing an optical cable according to the present invention.

FIG. 16 is a sectional view showing an optical cable manufactured according to a sixth embodiment of the method for manufacturing an optical cable according to the present invention.

[Explanation of symbols]

1, 20, 30, 70, 80, 90 ... optical cable, 2,
22, 72, 82 ... cylindrical member (center member), 3, 23,
33, 73, 83, 93 ... copper stranded wire (tensile member), 4i,
4o, 24i, 24o, 34, 74, 84 ... optical fiber unit, 5i, 5o, 35, 75 ... single groove spacer, 6
i, 6o, 26i, 26o, 36i, 36o, 76, 8
6,96 ... Tape core laminate (optical fiber), 10,2
1, 31, 71, 81, 91 ... jacket, 32, 92 ... multi-groove spacer (center member), M ... inverted portion, Mi ... inner layer inverted portion indication mark, Mo ... outer layer inverted portion indication mark, R ... inverted portion , Ri ...
Inner layer reversal part, Ro: outer layer reversal part, Z: magnetic part, Z1: first magnetic part, Z2: second magnetic part.

Continuation of the front page (72) Inventor Tadaki Haruki 1, Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (56) References JP-A-62-273216 (JP, A) JP-A-1- 257807 (JP, A) JP-A-7-333475 (JP, A) JP-A-4-182612 (JP, A) JP-A-8-15586 (JP, A) JP-A-11-133279 (JP, A) JP-A-1-173509 (JP, A) JP-A-4-59639 (JP, A) JP-A-8-227033 (JP, A) JP-A-62-21111 (JP, A) JP-B-56-35842 (JP, B2) JP 89689 (JP, Y2) US Pat. No. 4,828,352 (US, A) US Pat. No. 5,729,966 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6 / 44

Claims (8)

(57) [Claims] A plurality of inner layer optical fibers are assembled in an SZ twisted state around a central member containing a metallic tensile strength member as a center, and a plurality of outer layer optical fibers are SZ twisted around the inner layer optical fiber. In a method of manufacturing an optical cable, wherein the inner layer optical fiber is covered with a jacket, the strength member is magnetized at a position corresponding to an inner layer inversion portion of an inner layer SZ locus formed by the inner layer optical fiber. Forming the first magnetic field by the method, and magnetizing the strength member at a position corresponding to the outer layer reversal part included in the outer layer SZ locus formed by the outer layer optical fiber so that the first magnetic field can be distinguished from the first magnetic field. Forming a second magnetically polarized portion. 2. A step of detecting the first magnetized portion via the mantle, and providing an inner layer inversion portion indicating mark at a position of the mantle corresponding to the first magnetized portion; Detecting the second magnetic field and providing the outer layer reversing part display mark, which can be distinguished from the inner layer reversing part display mark, at a position corresponding to the second magnetic field part of the jacket. 2. The method for manufacturing an optical cable according to item 1. 3. An optical fiber including the outer layer optical fiber while accommodating the inner layer optical fiber in the spiral groove using a multi-groove spacer having a plurality of SZ-shaped spiral grooves formed on the outer periphery as the center member. Using a plurality of units, place the optical fiber unit around the multi-groove spacer by SZ.
3. The method of claim 1 or 2, wherein the sheets are twisted and assembled.
3. The method for manufacturing an optical cable according to claim 1. 4. The method according to claim 3, wherein the optical fiber unit comprises a single groove spacer accommodating the outer layer optical fiber. 5. A plurality of inner-layer optical fiber units including the inner-layer optical fiber and a plurality of outer-layer optical fiber units including the outer-layer optical fiber are used, and the inner-layer optical fiber unit is SZ-twisted around the central member to be assembled. The method for manufacturing an optical cable according to claim 1, wherein the outer optical fiber unit is SZ-twisted around the inner optical fiber unit to be assembled. 6. The optical fiber unit according to claim 1, wherein the inner optical fiber unit comprises a single groove spacer accommodating the inner optical fiber, and the outer optical fiber unit comprises a single groove spacer accommodating the outer optical fiber. Claim 5
3. The method for manufacturing an optical cable according to claim 1. 7. The method according to claim 5, wherein the inner optical fiber unit and the outer optical fiber unit are loose tubes. 8. A plurality of inner-layer optical fibers are SZ-twisted around a central member containing a metal tensile strength member as a center, and a plurality of outer-layer optical fibers are SZ-twisted around the inner-layer optical fiber. In the method of taking out the optical fiber from the optical cable in which the periphery of the outer layer optical fiber is covered with a jacket, the strength member is formed at a position corresponding to an inner layer reversal part of an inner layer SZ locus formed by the inner layer optical fiber. By magnetizing the first magnetic field, the first magnetic field is formed in advance, and the first magnetic field is magnetized at the position corresponding to the outer layer inversion of the outer layer SZ locus formed by the outer optical fiber. Forming in advance a second magnetic field that can be distinguished from each other, and detecting at least one of the first magnetic field and the second magnetic field via the jacket. To a method of taking out the optical fiber from the optical cable and removing the portion corresponding to at least one of the casing of the first magnetized portion and the second magnetized portion.