JPH0862462A - Loose tube type optical fiber cable - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a loose tube type optical fiber cable capable of completely filling a gap in the cable with a jelly compound. [Structure] A loose tube type in which a loose tube 20 accommodating an optical fiber core wire 1 and an interposing string 30 are twisted around the outer circumference of a tension member 4 and the outer circumference thereof is covered with a sheath 5, and a sheath 5 is filled with a jelly compound. The optical fiber cable is characterized in that either one or both of the interposing cord 30 and the loose tube 20 has a non-circular cross-sectional shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loose tube type optical fiber cable.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view of a conventional loose tube type optical fiber cable.

As shown in the figure, in the loose tube type optical fiber cable, the loose tube 2 accommodating the optical fiber core wire 1 and the interposition string 3 are twisted around the outer circumference of the tension member 4, and the sheath 5 and the jacket are covered. In addition to being covered with 6, the gap 7 between the loose tube 2, the interposing cord 3 and the sheath 5 is filled with a jelly compound for the purpose of preventing running water. Usually, the loose tube 2 and the interposition string 3 are circular in cross section.

[0004]

Generally, when water enters the inside of a cable, it runs and spreads in the longitudinal direction, which adversely affects the characteristics and life of the cable. Therefore, for the purpose of preventing running water, gas is supplied to the gap in the cable or jelly compound is filled.

When the gas is supplied into the cable, the gas is filled without any gap, but especially when the jelly compound is filled, a gap (gap) between the loose tube 2 or the interposing cord 3 and the tension member 4 is formed. It is necessary to completely fill 8.

By the way, in the case of an optical fiber cable, it is desirable that the outer diameter of the cable is small. In the loose tube type optical fiber cable, the loose tube 2 and the interposing string 3
The outer diameter of the cable is thinned by arranging (sometimes used) on the outer circumference of the tension member 4 without any gap and twisting them.

When the jelly compound is filled in the gap 7 in such a loose tube type optical fiber cable, the loose tube and the interposing cord are twisted around the outer circumference of the tension member, and the jelly compound is press-fitted after being covered with the sheath. To be done.

If there is almost no gap between the loose tube 2 and the interposing cord 3 at the time of filling the jelly compound, the jelly compound is not pressed into the gap between the loose tube 2 or the interposing cord 3 and the tension member 4. Will be insufficiently filled. It is conceivable that if a cable with insufficient jelly compound filling is exposed to water, it may run through this gap.

Therefore, an object of the present invention is to solve the above problems and to provide a loose tube type optical fiber cable capable of completely filling a clearance in the cable with a jelly compound.

[0010]

In order to achieve the above object, the present invention twists a loose tube accommodating an optical fiber core wire on an outer circumference of a tension member and an interlacing cord, and covers the outer circumference with a sheath. In a loose tube type optical fiber cable having a sheath filled with a jelly compound, one or both of the interposing cord and the loose tube have a non-circular cross-sectional shape.

In addition to the above structure, the present invention may have a non-circular cross-sectional shape by forming either a straight groove or a straight protrusion along the longitudinal direction on the outer circumference of one or both of the interposing cord and loose tube. Good.

In addition to the above structure, in the present invention, the non-circular shape may be formed by either the spiral groove or the spiral protrusion.

In addition to the above structure, according to the present invention, one or both of the discontinuous groove and the discontinuous projection may be formed along the longitudinal direction on the outer circumference of either one or both of the interposing cord and the loose tube.

In addition to the above construction, in the present invention, a plurality of notches may be formed along the longitudinal direction on the outer circumference of either one or both of the interposing string and the loose tube.

In addition to the above structure, in the present invention, the outer circumference of either one or both of the interposing string and the loose tube may be formed in a wave shape along the longitudinal direction.

In addition to the above structure, in the present invention, a plurality of recesses may be formed along the longitudinal direction on the outer circumference of either one or both of the interposing string and the loose tube.

In addition to the above construction, the present invention may be arranged such that the interposing string is a plate-shaped member having a plurality of through holes formed in the longitudinal direction.

In addition to the above structure, the present invention may be arranged such that the interposing string is a plate-shaped member having wavy unevenness formed along the longitudinal direction.

[0019]

According to the above construction, one or both of the interposing cord and the loose tube has a non-circular cross section. Therefore, if the interposing cord and the loose tube are twisted with the outer periphery of the tension member, the interposing cord and the loose tube are loosened. A gap will be newly formed between the tube and the tube. When the jelly compound is pressed into the gap between the interstitial string or loose tube and the sheath, the jelly compound flows into the gap on the tension member through the gap between the interstitial string and the loose tube, so the gap inside the cable is completely filled. Filled with jelly compound. Further, even if the interposing string is a plate-shaped member having a plurality of through holes formed in the longitudinal direction or a plate-shaped member having corrugated irregularities, the jelly compound is completely filled in the gap in the cable. As a result, water does not run even if water enters the cable.

[0020]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of a loose tube type optical fiber cable of the present invention.

As shown in the figure, the loose tube type optical fiber cable includes, for example, three loose tubes 20 accommodating four optical fiber core wires 1 and three interposing cords 30.
Are alternately twisted around the outer circumference of one tension member 4 and covered with the sheath 5 and the jacket 6, and the gap between the loose tube 20 and the interposing cord 30 and the sheath 5, the loose tube 20 and the interposing cord 30, and the tension. The gap between the members 4 is completely filled with the jelly compound.

Two grooves 21 and 31 are formed on the outer circumferences of the loose tube 20 and the interposing cord 30 at positions facing each other in the longitudinal direction (direction perpendicular to the drawing). That is, the cross-sectional shapes of the loose tube 20 and the interposing cord 30 are not circular because the grooves 21 and 31 are formed in the outer peripheral portion.

Although the grooves 21 and 31 are formed in both the loose tube 20 and the interposing cord 30 in the drawing, they may be formed in either one. Further, in the drawing, the number of loose tubes 20 and the number of intervening cords 30 is three, and the number of tension members 4 is one, but it goes without saying that the number is not limited to this.

Next, the operation of the embodiment will be described.

Since the loose tube 20 and the interposing cord 30 are non-circular in cross section, when the loose tube 20 and the interposing cord 30 are twisted around the outer periphery of the tension member 4,
A gap 9 is newly formed between the loose tube 20 and the interposing cord 30. When the jelly compound is pressed into the gap 7 between the loose tube 20 or the interposing cord 30 and the sheath 5, the loose tube 20 and the interposing cord 30 are inserted.
Since the jelly compound flows into the gap 8 on the tension member 4 through the gap newly formed between the gaps 7 and 8, the gaps 7 and 8 in the cable are completely filled with the jelly compound. Therefore, even if water enters the cable, it will not run.

By the way, when the loose tube 20 and the interposing cord 30 described above are extrusion-molded by an extruder, grooves (protrusions, which will be described later) are formed around the loose tube 20 and the interposing cord 30.
It is necessary to change the shape of the extruder die so that

In the present embodiment, the cross-sectional shape of the intervening cord is set as shown in FIG. 1, but it is not limited to this, and a gear type as shown in FIG. 2 (a) may be used. Two
It may be a notched circular shape as shown in (b).

The outer shape of either or both of the loose tube and the interposing cord is such that either one of a straight groove and a straight protrusion (31a) is formed on the outer periphery thereof along the longitudinal direction (FIG. 3 (a)). , Spiral groove 3 along the longitudinal direction on the outer circumference
1b or a spiral projection (not shown) is formed (FIG. 3 (b)), or a discontinuous groove or a discontinuous projection (31c) is formed on the outer periphery along the longitudinal direction. (FIG. 3 (c)), one having a plurality of notches 31d formed along the longitudinal direction on the outer periphery (FIG. 3 (d)), and one having a corrugated outer periphery along the longitudinal direction (FIG. 3 (e)) ), A plurality of recesses 31f are formed on the outer periphery along the longitudinal direction (FIG. 3 (f)).

Further, the interposing string 30 may be a plate-like member (FIG. 4A) having a plurality of through holes 32 formed along the longitudinal direction, and a plate-like member having corrugated irregularities 33 formed along the longitudinal direction. It may be a member (FIG. 4B).

In the above, according to the present embodiment, since either or both of the interposing cord and the loose tube have a non-circular cross-sectional shape, the loose tube type optical fiber capable of completely filling the gap in the cable with the jelly compound. A cable can be realized.

[0032]

In summary, according to the present invention, the following excellent effects are exhibited.

Since the jelly compound can be completely filled in the gap in the cable, running water can be prevented even if water enters the cable.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a loose tube type optical fiber cable of the present invention.

2 is a cross-sectional view of an interposing string used in the loose tube type optical fiber cable shown in FIG.

3 is a side view of an interposing string or loose tube used in the loose tube type optical fiber cable shown in FIG. 1. FIG.

4 is an external perspective view of an intervening plate used in place of the intervening string used in the loose tube type optical fiber cable shown in FIG.

FIG. 5 is a cross-sectional view of a conventional loose tube type optical fiber cable.

[Explanation of symbols]

 1 optical fiber core wire 4 tension member 5 sheath 20 loose tube 30 intervening string

Claims (9)

[Claims] 1. A loose tube accommodating an optical fiber core is twisted around an outer periphery of a tension member, and an interlacing cord is twisted.
A loose tube type optical fiber cable in which the outer periphery is covered with a sheath and the sheath is filled with a jelly compound, wherein one or both of the interposing cords and the loose tube are non-circular in cross-sectional shape. Loose tube type optical fiber cable. 2. The cross-sectional shape is non-circular by forming either a straight groove or a straight protrusion along the longitudinal direction on the outer circumference of one or both of the interposing cord and the loose tube. Loose tube type optical fiber cable. 3. The loose tube type optical fiber cable according to claim 1, wherein the non-circular shape is formed by one of the spiral groove and the spiral protrusion. 4. The loose tube type optical fiber according to claim 1, wherein either one or both of the interposing cord and the loose tube are provided with a discontinuous groove or a discontinuous projection along the longitudinal direction on the outer periphery thereof. cable. 5. The loose tube type optical fiber cable according to claim 1, wherein a plurality of cutouts are formed along the longitudinal direction on the outer circumference of one or both of the interposing cord and the loose tube. 6. The loose tube type optical fiber cable according to claim 1, wherein one or both of the interposing cord and the loose tube are formed in a wavy shape along the longitudinal direction. 7. The loose-tube type optical fiber cable according to claim 1, wherein a plurality of recesses are formed along the longitudinal direction on the outer circumference of one or both of the interposing cord and the loose tube. 8. The loose tube type optical fiber cable according to claim 1, wherein the intervening cord is a plate-shaped member having a plurality of through holes formed in the longitudinal direction. 9. The loose tube type optical fiber cable according to claim 1, wherein the intervening string is a plate-shaped member having wavy irregularities formed along the longitudinal direction.