JP6408289B2 - Slot type optical cable, method for manufacturing slot type optical cable, and slot core for optical cable - Google Patents

Description

The present invention relates to a slot-type optical cable , a method for manufacturing a slot-type optical cable , and a slot core for an optical cable .

A slot-type optical cable in which an optical fiber is accommodated in a groove-shaped slot formed on the outer peripheral portion is known (see, for example, Patent Documents 1 and 2).
In the manufacturing process of the slot-type optical cable of Patent Document 1, in order to prevent the optical fiber from falling out of the slot, the coarsely wound string is spirally wound around the outer periphery of the slot core (slot rod), and is further wound on the presser The tape is wound in a spiral shape, and then a jacket (sheath) is formed by extrusion.
In the slot type optical cable of Patent Document 2, in order to reduce the diameter of the optical cable by accommodating the optical fibers with high density, the longitudinal direction and the width direction of the adjacent optical fiber cores in the three or more optical fiber cores arranged in parallel are set. Intermittently connected optical fiber ribbons (also referred to as intermittently fixed optical fiber tapes) are packed together in a bundle and stored in a slot.

JP 2013-182094 A JP 2011-100115 A

  In the case of a slot type optical cable in which an intermittently fixed type optical fiber tape is accommodated in a slot as in Patent Document 2, when an impact is applied to the optical cable, an unconnected portion of the optical fiber (a portion not connected to an adjacent optical fiber) is formed. There is a unique problem that it tends to come out of the slot. As a result, the optical fiber removed from the slot may be sandwiched between the outer periphery of the slot core and the jacket (pressing tape), and the transmission loss of the optical fiber may increase.

  An object of the present invention is to suppress an increase in transmission loss of an optical fiber in a slot type optical fiber cable that accommodates an intermittently fixed type optical fiber tape.

A main invention for achieving the above object is an optical fiber tape having a plurality of optical fibers arranged in parallel, wherein connecting portions for connecting adjacent optical fibers are arranged in the longitudinal direction and the width direction of the optical fiber tape. An optical fiber tape disposed intermittently, a slot core having slots on the outer peripheral portion, the slot core accommodating the optical fiber tapes bundled together in the slot, and the outer peripheral portion of the slot core And a jacket for accommodating the slot core wound around the coarse winding string inside at least a part of the outer peripheral portion of the slot core. extrusion this process has a low melting point portion is formed, which is constituted by a low melting point material having a melting point lower than the temperature, in which the outer peripheral portion of the slotted core and the rough winding cord is adhesion It is a slot type optical cable according to claim.

  Other characteristics of the present invention will be made clear by the description and drawings described later.

  According to the present invention, since the optical fiber is hardly detached from the slot at the time of impact, an increase in transmission loss of the optical fiber can be suppressed.

FIG. 1 is a cross-sectional view of the slot type optical cable 1 of the first embodiment. FIG. 2 is an explanatory diagram showing the structure of the slot-type optical cable 1. FIG. 2 is an explanatory diagram of cross winding. 3A and 3B are explanatory diagrams of the intermittently fixed type optical fiber tape 31. FIG. FIG. 4 is an explanatory diagram of single winding. FIG. 5 is an explanatory diagram of the manufacturing apparatus 10 (manufacturing process) for the slot-type optical cable 1. 6A to 6C are explanatory diagrams of the impact test. FIG. 7 is an explanatory diagram showing a state in which the optical fiber 31A is sandwiched between the slot core 2 and the jacket 6. FIG. 8 is a cross-sectional view of the slot type optical cable 1 of the second embodiment. FIG. 9 is a cross-sectional view of a slotted optical cable 1 according to a modification of the second embodiment. FIG. 10 is an explanatory view showing the structure of the slot type optical cable 1 of the third embodiment.

  At least the following matters will be apparent from the description and drawings described below.

  An optical fiber tape having a plurality of optical fibers arranged in parallel, wherein the connecting portion that connects the adjacent optical fibers is intermittently disposed in the longitudinal direction and the width direction of the optical fiber tape, and A slot core having a slot on the outer periphery, the slot core accommodating the optical fiber tapes bundled together in the slot, and a coarsely wound string wound spirally around the outer periphery of the slot core; A slot-type optical cable comprising: a jacket for accommodating the slot core wound around the coarsely wound string; and the outer peripheral portion of the slot core and the coarsely wound string are bonded to each other. It becomes clear. According to such a slot-type optical cable, the optical fiber is not easily detached from the slot at the time of impact, so that an increase in transmission loss of the optical fiber can be suppressed.

It is desirable that the rough wound string includes a high melting point material and a low melting point material which are two types of materials having different melting points. As a result, the coarsely wound string and the outer peripheral portion of the slot core can be bonded, and at the time of branching, the coarsely wound string can be easily detached from the slot core by the high melting point material.

  The melting point of the low melting point material is preferably equal to or lower than the extrusion processing temperature of the jacket. As a result, the coarsely wound string and the outer peripheral portion of the slot core can be bonded to each other with the low melting point material when the slot type optical cable is manufactured.

  It is desirable that the difference between the melting point of the high melting point material and the melting point of the low melting point material is 20 ° C. or more. Thereby, it becomes easy to control the amount of heat received by the coarsely wound string.

  It is preferable that the two coarsely wound strings are spirally wound around the outer peripheral portion of the slot core in opposite directions. As a result, the number of places where the coarsely wound string presses the optical fiber increases, so that the optical fiber is unlikely to come out of the slot upon impact.

  It is desirable that at least a part of the outer peripheral portion of the slot core is formed with a low melting point portion made of a low melting point material having a melting point lower than the extrusion temperature of the jacket. Thereby, the range of selection of the material of the slot core can be expanded.

  It is desirable that the low melting point portion is formed at a corner between the slot and the outer peripheral portion. This makes it difficult for the optical fiber to come out of the slot during impact.

  It is desirable that the low melting point portion is formed on the entire outer peripheral portion between the slots. Thereby, the adhesion state of the coarsely wound string is not easily destroyed.

  When the base material constituting the slot core and the low melting point material are coextruded, the steel wire in the slot core is twisted before the extrusion head of the extruder having a die portion with a groove. Thus, it is preferable that the slot core having the low melting point is formed. Thereby, the slot core can be formed by a simple process.

  An optical fiber tape having a plurality of optical fibers arranged in parallel, wherein a connecting portion that connects the adjacent optical fibers is intermittently disposed in the longitudinal direction and the width direction of the optical fiber tape, A step of accommodating the slot core in a slot; a step of spirally winding a coarsely wound string around the outer periphery of the slot core in which the optical fiber tape is accommodated in the slot; and the optical fiber tape while being accommodated in the slot Forming a jacket so as to accommodate the slot core wound around the rough winding cord, and bonding the outer peripheral portion of the slot core and the rough winding cord to each other. The manufacturing method becomes clear. According to such a manufacturing method, it is possible to manufacture a slot type optical cable in which the optical fiber is unlikely to be detached from the slot at the time of impact.

  It is desirable to heat-seal the outer peripheral portion of the slot core and the coarsely wound string using heat at the time of forming the outer jacket. This simplifies the manufacturing process of the slot type optical cable.

=== First Embodiment ===
<Configuration>
FIG. 1 is a cross-sectional view of the slot type optical cable 1 of the first embodiment. FIG. 2 is an explanatory diagram showing the structure of the slot-type optical cable 1. In FIG. 2, only one optical fiber unit 3 accommodated in the slot 21 is illustrated.

  The slot-type optical cable 1 includes a slot core 2, an optical fiber unit 3, a coarsely wound string 4, a presser winding tape 5, and a jacket 6.

  The slot core 2 is a member having a plurality of slots 21 (grooves) on the outer peripheral portion 22. Each slot 21 of the slot core 2 is formed in an SZ shape here. The SZ-shaped slot 21 is a groove in which the spiral rotation direction is periodically reversed. The slot 21 may be formed in a spiral shape in one direction. Each slot 21 accommodates the optical fiber unit 3 (see FIG. 1). The ribs 23 between the slots 21 separate the optical fiber units 3 accommodated in the respective slits.

  A tension member 24 (strength member) is embedded in the center of the slot core 2. For the tension member 24, fiber reinforced such as metal wire such as steel wire or iron wire, glass FRP (GFRP), aramid fiber reinforced plastic (KFRP) reinforced by Kevlar (registered trademark), polyethylene fiber reinforced plastic reinforced by polyethylene fiber, etc. Plastic (FRP) can be used.

  Here, the slot core 2 is made of high-density polyethylene. The melting point of the high-density polyethylene constituting the slot core 2 is 120 ° C to 130 ° C. However, the slot core 2 may be made of other resin.

  FIG. 3A is an explanatory diagram of an example of the intermittently fixed type optical fiber tape 31.

  The optical fiber unit 3 is a bundle of a plurality of optical fibers 31 </ b> A configured by collecting intermittently fixed optical fiber tapes 31 in a bundle. Here, the optical fiber unit 3 by 20 optical fibers 31A is constituted by bundling five pieces of the four-fiber intermittently fixed optical fiber tapes 31 shown in FIG. 3A.

The intermittently fixed type optical fiber tape 31 is an optical fiber tape 31 having a plurality of optical fibers 31A arranged in parallel, and a connecting portion 31B that connects adjacent optical fibers 31A is in the longitudinal direction of the optical fiber tape 31. It is the optical fiber tape 31 arrange | positioned intermittently in the width direction, respectively.
A plurality of connecting portions 31B that connect two adjacent optical fibers 31A are intermittently arranged two-dimensionally in the longitudinal direction and the width direction. The connecting portion 31B connects the two adjacent optical fibers 31A with, for example, an ultraviolet curable resin or a thermoplastic resin. A region other than the connecting portion 31B between the two adjacent optical fibers 31A is a non-connecting portion. In the unconnected portion, the adjacent two optical fibers 31A are not restrained. As a result, the optical fiber tape 31 can be rolled into a cylindrical shape (bundle) or folded and stored, and a large number of optical fibers 31A can be stored in the slot 21 of the slot-type optical cable 1 with high density. .

  The intermittently fixed type optical fiber tape 31 is not limited to the one shown in FIG. 3A. For example, as shown in FIG. 3B, the number of optical fibers 31A constituting the intermittently fixed type optical fiber tape 31 may be changed to another number, and the arrangement of the connecting portions 31B may be appropriately changed.

  The coarsely wound string 4 is a string-like member wound spirally around the outer peripheral portion 22 of the slot core 2 in which the optical fiber unit 3 is accommodated in the slot 21. In order to prevent the optical fiber unit 3 and the optical fiber 31 </ b> A from falling out of the slot 21 in the manufacturing process (described later) of the slot-type optical cable 1, the coarsely wound string 4 is spirally wound around the outer peripheral portion 22 of the slot core 2. .

  In the present embodiment, the coarsely wound string 4 is bonded to the outer peripheral portion 22 (the surface of the rib 23) of the slot core 2. As the bonding method, heat fusion, bonding with an adhesive, or the like can be employed. However, bonding by heat fusion is desirable because it has higher bonding strength than bonding by an adhesive. When heat-sealing the coarsely wound string 4 to the slot core 2, heat fusion may be performed using the heat at the time of extrusion of the outer cover 6. After the winding, it may be heated and heat-sealed before the outer cover 6 is extruded. Here, the coarsely wound string 4 is made of a thermoplastic resin, and the outer peripheral portion 22 of the slot core 2 and the coarsely wound string are formed by heat at the time of extrusion of the outer cover 6 in the manufacturing process (described later) of the slot-type optical cable 1. 4 is bonded (heat-sealed).

  In the present embodiment, the coarsely wound string 4 is a composite of a high melting point material having a higher melting point than the heat at the time of extrusion molding of the jacket 6 and a low melting point material having a melting point lower than the heat at the time of extrusion molding of the jacket 6. Consists of materials. By constructing the coarsely wound string 4 from a composite material, the coarsely wound string 4 and the outer peripheral surface of the slot core 2 can be bonded to each other with a low melting point material when the slot type optical cable 1 is manufactured, and a high melting point material when the optical fiber 31A is branched. This makes it easier to remove the coarsely wound string 4 from the slot core 2.

As the high melting point material constituting the rough wound string 4, for example, a high melting point plastic material such as polyamide or a polyester resin such as polyethylene terephthalate (PET) can be used. Here, nylon (trademark) is used. Yes. Further, as the low melting point material, polyethylene (PE), polypropylene (PP), ethylene vinyl acetate (EVA), ethylene ethyl acrylate (EEA), or the like can be used, and here, low density polyethylene is used. The melting point of nylon (trademark) is 200 ° C. to 300 ° C., and the melting point of low density polyethylene is about 100 ° C.
In this embodiment, the coarsely wound string 4 includes a high melting point material and a low melting point material which are two types of materials having different melting points. By configuring the coarsely wound string with the composite material in this way, the coarsely wound string 4 and the outer peripheral portion 22 of the slot core 2 can be bonded, and at the time of branching, the coarsely wound string 4 can be easily detached from the slot core 2 with a high melting point material. Become.
Further, in the present embodiment, the melting point of the low melting point material constituting the coarsely wound string 4 is equal to or lower than the extrusion temperature (160 ° C. to 230 ° C.) of the jacket 6. Thereby, the coarsely wound string 4 and the outer peripheral portion 22 of the slot core 2 can be bonded to each other with the low melting point material when the slot type optical cable 1 is manufactured.
In the present embodiment, the difference between the melting point of the high melting point material and the melting point of the low melting point material constituting the rough winding string 4 is 20 ° C. or more. Thus, if the difference in melting point is 20 ° C. or more, the amount of heat received by the coarsely wound string 4 can be controlled by adjusting the distance from the extruder to the cooling tank, the linear velocity, etc. during the extrusion of the jacket 6 (high It is preferable to melt only the low melting point material without melting the melting point material).

  The coarsely wound string 4 may have a tape shape with a flat cross section or a thread shape with a round cross section. The coarsely wound string 4 made of a composite material may have a two-layer structure of a high melting point material and a low melting point material, or a fiber bundle structure in which fibers of a high melting point material and fibers of a low melting point material are twisted together. But it ’s okay. When the coarsely wound string 4 is constituted by a two-layer structure of a high melting point material and a low melting point material, the coarsely wound string 4 is arranged so that the low melting point material layer and the outer peripheral portion 22 of the slot core 2 are in contact with each other. Is desirable. Thereby, it becomes easy to adhere the coarsely wound string 4 and the outer peripheral surface of the slot core 2.

  As shown in FIG. 2, the two coarsely wound strings 4 are spirally wound around the outer peripheral portion 22 of the slot core 2 in opposite directions. However, as shown in FIG. 4, it is also possible to simply wind one coarse wound string 4 in a spiral shape. In the following description, the winding method in which the two coarsely wound cords 4 are spirally wound in opposite directions as shown in FIG. 2 is referred to as “cross winding”. In addition, as shown in FIG. 4, a winding method in which a single coarsely wound string 4 is spirally wound is referred to as “single winding”. Cross winding is preferable because the number of places where the coarsely wound string 4 presses the optical fiber 31A increases compared to single winding. As will be described later, the pitch P (see FIG. 2) of the cross-winding coarsely wound string 4 is preferably 15 mm or less. In the case of single winding, it is preferable that the spiral direction of the coarsely wound string 4 is opposite to the slot 21 because the number of locations where the coarsely wound string 4 blocks the slot 21 increases. Note that the number of the coarsely wound cords 4 wound spirally around the outer peripheral portion 22 of the slot core 2 may be two or more.

  The presser winding tape 5 is a member that wraps the slot core 2 that houses the optical fiber unit 3. As the presser winding tape 5, a polyimide tape (film), a polyester tape, a polypropylene tape, a polyethylene tape, or the like is used. In addition, a nonwoven fabric can be used as the presser winding tape 5. In this case, the nonwoven fabric used is a tape formed of polyimide, polyester, polypropylene, polyethylene or the like. In addition, the nonwoven fabric may be a material to which water-absorbing powder or the like is attached and applied, or a surface processed for that purpose. The presser winding tape 5 may be a non-woven fabric bonded with a film such as a polyester film. In addition, in order to protect the optical fiber 31A from impact, side pressure, etc., a synthetic sponge or rubber sponge made of foamed polyethylene or foamed polyurethane may be bonded to the tape (film) or non-woven fabric. Note that the press winding tape 5 has a melting point of about 230 ° C. here.

  The jacket 6 is a member that covers the slot core 2, the optical fiber unit 3, and the coarsely wound string 4 so as to be accommodated. As the material of the jacket 6, for example, a resin such as polyvinyl chloride (PVC), polyethylene (PE), nylon (registered trademark), ethylene fluoride, or polypropylene (PP) can be used. Further, as a material of the outer cover 6, for example, a polyolefin compound containing a hydrated metal compound such as magnesium hydroxide or aluminum hydroxide as a flame retardant can also be used. Here, LLDPE is used for the jacket 6, and the extrusion temperature of the jacket 6 is 160 ° C to 230 ° C.

<Method for Manufacturing Slot-Type Optical Cable 1>
FIG. 5 is an explanatory diagram of the manufacturing apparatus 10 (manufacturing process) for the slot-type optical cable 1.
The collective machine 11 is supplied with the slot core 2 and the optical fiber unit 3, and the collective machine 11 accommodates the optical fiber unit 3 in the slot 21 of the slot core 2 while twisting it in the SZ shape. The winding device 12 is a device that winds the coarsely wound string 4 around the outer peripheral portion 22 of the slot core 2 in which the optical fiber unit 3 is accommodated in the slot 21. The winding device 12 is disposed between the collecting machine 11 and the extruder 13. That is, after the optical fiber unit 3 is received in the slot 21 of the slot core 2 by the collecting machine 11 and before the outer cover 6 is formed by the extruder 13, the winding device 12 spirals the outer peripheral portion 22 of the slot core 2. The coarsely wound string 4 is wound in a shape. This prevents the optical fiber unit 3 from falling out of the slot 21 before forming the jacket 6.

  The slot core 2 wound around the coarsely wound string 4 while accommodating the optical fiber unit 3 (optical fiber tape 31) in the slot 21 and the presser winding tape 5 are supplied to the extruder 13. The extruder 13 covers the outer jacket 6 so as to accommodate the slot core 2 wrapped in the presser winding tape 5 by extrusion molding. At this time, the low melting point material of the coarsely wound string 4 is melted by the heat of the molten resin for forming the jacket, and the outer peripheral portion 22 of the slot core 2 and the roughly wound string 4 are thermally fused. Since the outer peripheral portion 22 of the slot core 2 and the coarsely wound string 4 can be bonded by using heat at the time of extrusion molding of the jacket 6, the manufacturing process is simplified.

<About impact resistance>
6A to 6C are explanatory diagrams of the impact test. FIG. 7 is an explanatory diagram showing a state in which the optical fiber 31A is sandwiched between the slot core 2 and the jacket 6. Here, the rough winding string 4 and the presser winding tape 5 are omitted from the illustration.

  When the slot-type optical cable 1 receives an impact, the slot-type optical cable 1 is instantaneously deformed and then returns to its original shape due to elasticity. When the slot-type optical cable 1 is deformed by an impact, a gap is formed between the outer peripheral portion 22 (rib 23) of the slot core 2 and the jacket 6 (between the outer peripheral portion 22 of the slot core 2 and the presser winding tape 5). it can. Since the intermittently fixed optical fiber tape 31 has a non-connected portion (see FIGS. 3A and 3B), the optical fiber 31A (particularly the non-connected portion) of the intermittently fixed optical fiber tape 31 is disconnected from the slot 21 at the time of impact. Thus, the optical fiber 31A may be sandwiched in the gap between the outer peripheral portions 22 of the slot core 2 (see the black circle optical fiber 31 in FIG. 7). As a result, an increase in transmission loss of the optical fiber 31A or a disconnection of the optical fiber 31A may occur. Even when the coarsely wound cord 4 is simply wound without being bonded to the slot core 2, the loosely wound cord 4 is slackened when the slot type optical cable 1 is deformed by an impact, and the outer periphery of the slot core 2 is There is a possibility that the optical fiber 31 </ b> A may be caught in the gap between the portions 22.

  On the other hand, in this embodiment, the outer peripheral part 22 of the slot core 2 and the coarsely wound string 4 are bonded. For this reason, even if the slot-type optical cable 1 is deformed by an impact, the coarsely wound string 4 bonded to the slot core 2 prevents the optical fiber 31 </ b> A from jumping out of the slot 21. As a result, the optical fiber 31A is suppressed from being caught in the gap between the outer peripheral portions 22 of the slot core 2, and an increase in transmission loss or disconnection of the optical fiber 31A can be suppressed.

<Example>
First Example A slot type optical cable 1 having a cross-sectional structure shown in FIG. 1 was prepared. The outer diameter of the slot type optical cable 1 is 10 mm, the thickness of the jacket 6 is 1.5 mm, the sectional area of each slot 21 is about 2.2 mm ² , and the optical fiber 31A of the optical fiber unit 3 accommodated in each slot 21 is provided. The number was 20 (heart).
In the slot-type optical cable 1 of the first embodiment, two coarsely wound cords 4 made of a composite material of nylon (trademark) and low density polyethylene were cross-wound (see FIG. 2). In the slot type optical cable of the comparative example, two coarsely wound cords 4 made of nylon (trademark) were cross-wound. In addition, five types (10 mm, 12 mm, 15 mm, 18 mm, and 20 mm) of slot-type optical cables 1 having different pitches P (see FIG. 2) of the coarsely wound string 4 wound spirally were prepared. The coarsely wound string 4 of the slot type optical cable 1 of the first embodiment was heat-sealed to the outer peripheral portion 22 of the slot core 2 by heat at the time of extrusion molding of the jacket 6. Since the coarsely wound string 4 of the comparative example is composed only of a high melting point material, it is not bonded to the outer peripheral portion of the slot core 2.

  The impact test was conducted in accordance with the international standard IEC 60794-1-2. The impact energy was 5 J and the number of impact repetitions was 50. 50 impacts are applied to different locations of one slot type optical cable, and the loss increase residual value is zero even in one optical fiber (here, one optical fiber out of 100 optical fibers) after the impact test. When there was a value exceeding 0.1 dB, it was evaluated as x, and when the loss increase residual value was 0.1 dB or less, it was evaluated as ◯. The evaluation results are as follows.

  In the first example, when the helical pitch of the coarsely wound string 4 was 15 mm or less, the loss increase residual value of the optical fiber 31A after the impact test was 0.1 dB or less, and good results were obtained. On the other hand, in the comparative example, even when the helical pitch of the coarsely wound string 4 was 15 mm or less, the loss increase residual value of the optical fiber 31A after the impact test exceeded 0.1 dB. When the slot type optical cable of the comparative example was inspected after the impact test, the optical fiber 31A was removed from the slot regardless of the helical pitch of the coarsely wound string 4, and the optical fiber 31A was located between the rib of the slot core and the jacket 6 It was confirmed that it was sandwiched between. From these results, the effectiveness of bonding the coarsely wound string 4 to the outer peripheral portion 22 of the slot core 2 was confirmed.

  In the first example, when the helical pitch of the coarsely wound string 4 was 18 mm or more, the loss increase residual value of the optical fiber 31A after the impact test exceeded 0.1 dB. When these slot type optical cables 1 were inspected after the impact test, the optical fiber 31A was removed from the slot 21, and the optical fiber 31A was sandwiched between the rib 23 of the slot core 2 and the jacket 6 (pressing winding tape 5). It was confirmed that This is considered because the optical fiber 31 </ b> A is detached from the slot 21 at the time of impact because the spiral pitch of the coarsely wound string 4 is widened. From these results, it was confirmed that when the two coarsely wound cords 4 are cross-wound, the spiral pitch of the coarsely wound cords 4 is desirably 15 mm or less.

  In the first embodiment, when the helical pitch of the coarsely wound string 4 is 18 mm or more, the loss increase residual value exceeds 0.1 dB, and this is the same evaluation result as the slot type optical cable of the comparative example. is there. However, in consideration of the fact that in the first embodiment, good results are obtained when the spiral pitch of the coarsely wound string 4 is 15 mm or less, and in the comparative example, good results cannot be obtained even in the case of the same spiral pitch. Even if the spiral pitch of the coarsely wound string 4 is 18 mm or more in the embodiment, the coarsely wound string 4 is bonded to the outer peripheral portion 22 of the slot core 2 as compared with the case of the same spiral pitch of the comparative example. It is considered that the optical fiber 31A is unlikely to be detached from the slot 21 at the time of impact.

Second Example In the slot-type optical cable 1 of the second example, a coarsely wound string 4 made of a composite material similar to that of the first example was used. However, in the second example, instead of cross-winding the two coarsely wound cords 4, one coarsely wound cord 4 was single-wound as shown in FIG. Other conditions are the same as in the first embodiment. Also in the second embodiment, five types of slot-type optical cables 1 (5 types of 10 mm, 12 mm, 15 mm, 18 mm, and 20 mm) with different pitches of the coarsely wound string 4 wound in a spiral shape were prepared. The coarsely wound string 4 of the slot type optical cable 1 of the second embodiment was heat-sealed to the outer peripheral portion 22 of the slot core 2 by heat at the time of extrusion molding of the jacket 6.

  The slot-type optical cable 1 of the second example was also subjected to the same impact test as described above, and the same evaluation was performed. That is, the impact test was conducted according to the international standard IEC 60794-1-2. The impact energy was 5 J and the number of impact repetitions was 50. 50 impacts are applied to different locations of one slot type optical cable, and the loss increase residual value is zero even in one optical fiber (here, one optical fiber out of 100 optical fibers) after the impact test. When there was a value exceeding 0.1 dB, it was evaluated as x, and when the loss increase residual value was 0.1 dB or less, it was evaluated as ◯. The evaluation results are as follows.

  In the second example, even when the helical pitch of the coarsely wound string 4 was 15 mm or less, the loss increase residual value of the optical fiber 31A after the impact test exceeded 0.1 dB. When the slot type optical cable 1 of the second embodiment was inspected after the impact test, the optical fiber 31A was removed from the slot 21 regardless of the helical pitch of the coarsely wound string 4, and the optical fiber 31A was connected to the rib 23 of the slot core 2. It was confirmed that it was sandwiched between the jacket 6. This is because when the coarsely wound string 4 is single-wound, the number of places where the roughly wound string 4 blocks the slot 21 is reduced compared to the case of cross-winding (because it is almost reduced by half). This is probably because the optical fiber 31 </ b> A is easily detached from the slot 21. From these results, it was confirmed that the method of winding the coarsely wound string 4 is preferably cross winding rather than single winding.

  In addition, although the loss increase residual value exceeds 0.1 dB in the second embodiment, the slot-type optical cable 1 of the second embodiment is single-wound without adhering the coarsely wound string 4 to the outer peripheral portion 22 of the slot core 2. Compared with the slot type optical cable, it is considered that the optical fiber 31A is not easily detached from the slot 21 at the time of impact.

=== Second Embodiment ===
As the material of the slot core 2, for example, among thermoplastic polyolefins, a high-strength plastic material such as high-density polyethylene (HDPE) or an engineering plastic material such as polyamide, polycarbonate, or polybutylene terephthalate may be used. However, depending on the material of the high-strength material that constitutes the slot core 2, the amount of heat for heat-sealing the coarsely wound string 4 to the outer peripheral portion 22 of the slot core 2 increases. May become narrower.
Therefore, in the second embodiment, the low melting point portion 22A is formed in at least a part of the outer peripheral portion 22 of the slot core 2 made of a high-strength material (particularly, the corner between the slot 21 and the outer peripheral portion 22). . And the low melting-point part 22A of the slot core 2 and the rough winding string 4 are heat-sealed (adhered) by the heat at the time of extrusion molding of the jacket 6.

FIG. 8 is a cross-sectional view of the slot type optical cable 1 of the second embodiment.
The slot core 2 of the second embodiment is mainly composed of a high-strength material, and here is composed of a thermoplastic polyolefin (melting point: 120 ° C. to 130 ° C.). A low melting point portion 22A is formed on the entire surface of the outer peripheral portion 22 of the slot core 2 (the surface of the rib 23). In FIG. 8, the formation region of the low melting point portion 22A is hatched. The low melting point portion 22A is made of a low melting point material having a melting point lower than the extrusion processing temperature of the jacket 6, and is made of LDPE here. In the manufacturing process of the slot-type optical cable 1 (see FIG. 5), the coarsely wound string 4 spirally wound around the slot core 2 to prevent the optical fiber 31A from dropping out of the slot 21 is Is heat-sealed to the low melting point portion 22A of the slot core 2. With this configuration, the center portion of the slot core 2 can be made of a high-strength material, and the coarsely wound string 4 and the outer peripheral portion 22 of the slot core 2 can be bonded.

  In the slot type optical cable 1 of the second embodiment, a low melting point portion 22 </ b> A is formed at the corner between the slot 21 and the outer peripheral portion 22. For this reason, since the coarsely wound string 4 is bonded at this corner, the optical fiber 31A is unlikely to be detached from the slot 21 at the time of impact.

  In the slot type optical cable 1 of the second embodiment, the low melting point portion 22A is formed not only on the corners of the slot 21 and the outer peripheral portion 22 but also on the entire surface of the outer peripheral portion 22 of the slot core 2. For this reason, the adhesion of the coarsely wound string 4 at the corners of the slot 21 and the outer peripheral portion 22 becomes strong, and the adhesion state is not easily broken even when subjected to an impact.

  The slot core 2 of the second embodiment is preferably manufactured as follows. The base material (high strength material) constituting the slot core and the low melting point material are coextruded. At that time, the die portion of the extruder that performs co-extrusion is formed into a grooved shape, and the steel wire that is the tension member in the slot core 2 is twisted before the extrusion head of the extruder to form a spiral or SZ shape. The slot core 2 having the groove (slot 21) is formed. Thereby, the slot core 2 can be formed by a simple process.

FIG. 9 is a cross-sectional view of a slotted optical cable 1 according to a modification of the second embodiment.
In the slot core 2 of the modified example, the low melting point portion 22 </ b> A is formed not only on the entire surface of the outer peripheral portion 22 of the slot core 2 but only at the corner between the slot 21 and the outer peripheral portion 22. Also in the slot type optical cable 1 of this modified example, since the coarsely wound string 4 is bonded at the corners of the slot 21 and the outer peripheral portion 22, the optical fiber 31A is not easily detached from the slot 21 at the time of impact. However, in the modified example, the coarsely wound string 4 is not bonded to other portions of the outer peripheral portion 22 of the slot core 2, and therefore, compared to the case of FIG. 8, the bonded state of the coarsely wound string 4 and the slot core 2 at the time of impact. Will be easily destroyed. Further, the slot core 2 of the modified example is limited in the arrangement of the low-melting point material, and it is difficult to adjust the width and the like.

=== Third Embodiment ===
FIG. 10 is an explanatory view showing the structure of the slot type optical cable 1 of the third embodiment. In the above-described embodiment, the rough winding string 4 made of a composite material of a high melting point material and a low melting point material is used. On the other hand, in 3rd Embodiment, the coarsely wound string 4A comprised with the high melting point material and the coarsely wound string 4B comprised with the low melting point material are cross-wound.

  In the manufacturing process of the slot-type optical cable 1 (see FIG. 5), the optical fibers 31A from the slots 21 drop off from the coarsely wound cords 4A and 4B spirally wound around the slot core 2 before the outer cover 6 is extruded. To prevent that. Further, in the manufacturing process of the slot-type optical cable 1 (see FIG. 5), the outer peripheral portion 22 of the slot core 2 and the coarsely wound string 4B made of a low melting point material are heat-sealed by heat at the time of extrusion molding of the jacket 6. Is done.

  In 3rd Embodiment, the rough winding string 4B comprised with the low melting-point material may fracture | rupture with the heat | fever at the time of the extrusion molding of the jacket 6. FIG. However, even if the coarsely wound string 4B made of the low melting point material is broken, the coarsely wound string 4A made of the high melting point material is not broken. Therefore, the optical fiber 31A from the slot 21 is formed before the outer cover 6 is extruded. Can be prevented from falling off. Further, even if there is no coarse winding string 4A made of a high melting point material, since the outer cover 6 is already formed when the rough winding string 4B made of a low melting point material is broken by heat, Can be prevented from falling off. And even if the rough winding string 4B made of the low melting point material is broken by heat, the broken rough winding string 4B is bonded to the outer peripheral portion 22 of the slot core 2, and the rough winding string 4B is attached to the slot 21. Since a part of the opening is blocked, the optical fiber 31A is not easily detached from the slot 21 at the time of impact.

=== Others ===
The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be modified and improved without departing from the gist thereof, and it goes without saying that the present invention includes equivalents thereof.

1 slot type optical cable, 2 slot core,
3 Optical fiber unit, 4 Coarse winding string,
5 presser tape, 6 outer jacket,
10 manufacturing equipment, 11 collecting machines,
12 winding device, 13 extruder 21 slot, 22 outer peripheral part, 22A low melting point part,
23 ribs, 24 tension members,
31 Intermittently fixed optical fiber tape,
31A optical fiber, 31B coupling part,

Claims (11)

An optical fiber tape having a plurality of optical fibers arranged in parallel, wherein the connecting portion that connects the adjacent optical fibers is intermittently disposed in the longitudinal direction and the width direction of the optical fiber tape, and
A slot core having slots on the outer periphery, the slot core accommodating the optical fiber tapes bundled in a bundle; and
A coarsely wound string wound spirally around the outer periphery of the slot core;
A jacket for accommodating the slot core wound around the rough winding string inside,
At least a part of the outer peripheral portion of the slot core is formed with a low melting point portion made of a low melting point material having a melting point lower than the extrusion temperature of the jacket,
A slot-type optical cable, wherein the outer peripheral portion of the slot core and the coarsely wound string are bonded together. The slot-type optical cable according to claim 1,
The slot-type optical cable, wherein the coarsely wound string includes a high melting point material and a low melting point material, which are two kinds of materials having different melting points. The slot-type optical cable according to claim 2,
The slot-type optical cable according to claim 1, wherein a melting point of the low-melting-point material is equal to or lower than an extrusion temperature of the jacket. The slot-type optical cable according to claim 2 or 3,
A slot-type optical cable, wherein a difference between a melting point of the high melting point material and a melting point of the low melting point material is 20 ° C. or more. The slot-type optical cable according to any one of claims 1 to 4,
A slot-type optical cable, wherein the two coarsely wound cords are spirally wound around the outer peripheral portion of the slot core in opposite directions. The slot-type optical cable according to claim 5,
The slot-type optical cable according to claim 1, wherein a pitch of the coarsely wound string wound spirally around the outer peripheral portion of the slot core is 15 mm or less. The slot-type optical cable according to any one of claims 1 to 6 ,
A slot-type optical cable, wherein the low melting point portion is formed at a corner between the slot and the outer peripheral portion. The slot-type optical cable according to claim 7 ,
The slot type optical cable, wherein the low melting point portion is formed on the entire surface of the outer peripheral portion between the slots. The slot-type optical cable according to any one of claims 1 to 8 ,
When the base material constituting the slot core and the low melting point material are coextruded, the steel wire in the slot core is twisted before the extrusion head of the extruder having a die portion with a groove. Thus, the slot core having the low melting point is formed. An optical fiber tape having a plurality of optical fibers arranged in parallel, wherein a connecting portion that connects the adjacent optical fibers is intermittently disposed in the longitudinal direction and the width direction of the optical fiber tape, Receiving the slot in the slot core; and
A step of spirally winding a coarsely wound string around the outer periphery of the slot core containing the optical fiber tape in the slot;
Forming a jacket so as to accommodate the slot core wound around the rough winding string while accommodating the optical fiber tape in the slot,
At least a part of the outer peripheral portion of the slot core is formed with a low melting point portion made of a low melting point material having a melting point lower than the extrusion temperature of the jacket,
The method of manufacturing a slot-type optical cable, wherein the outer peripheral portion of the slot core and the coarsely wound string are heat-sealed using heat at the time of forming the jacket .   A slot core for an optical cable having a slot in the outer peripheral portion and accommodating the optical fiber tapes bundled in a bundle,
  A slot core for an optical cable, characterized in that a low melting point portion made of a low melting point material having a melting point lower than the extrusion temperature of the jacket is formed on at least a part of the outer peripheral portion.

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