JP2003227977A - Optical fiber drop cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber drop cable having a fine diameter and in which mechanical characteristics such as optical loss, lateral pressure and lead wire preparability of coated optical fiber are enhanced. <P>SOLUTION: The fiber drop cable 1 is provided with a long optical element part 19 consisting of an optical fiber unit 7 in which a plurality of coated optical fibers 3 are covered all together with a unit sheath 5, a long cable sheath part 15 which covers, with a cable sheath 13, at least a pair of first tension bodies 11 parallel installed to each other on both sides of the optical fiber unit 7, and a cable-tearing notch part 17 which is arranged on both sides of the cable sheath part 15. In addition, a long cable supporting part 23 covering a second tension body 25 with a sheath 27 is stuck parallel to each other to the optical element part 19 to form the fiber drop cable 1. Further, the unit sheath 5 is made of an expandable resin, thereby enhancing lateral pressure characteristic and enabling a fine diameter for the cable. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber drop cable, and more particularly to an optical fiber drop cable for intermediately branching from a closure or the like of an overhead line at each drop point of each electric pole.

[0002]

2. Description of the Related Art Conventionally, FTTH (Fiber to the Home)
That is, in order to be able to send and receive high-speed broadband information such as ultra-high-speed data at home or office, the optical fiber cable extended from the central office is dropped into the subscriber's home such as a general residence. A fiber optic drop cable suitable for wiring this is used.

Referring to FIG. 2, a main cable 103 is wired on the main power pole 101, and a plurality of power poles 1 for wiring to each home or office are provided between the main power poles 101.
05 is provided. The optical fiber cable of the trunk cable 103 is branched by the AO closure 107 provided in the main utility pole 101, and each utility pole 105 is branched from this AO closure 107 using the optical fiber drop cable 109.
1 drop point closure for each drop point
An intermediate branch is made at 11. Then, it is dropped from the drop point closure 111 to each home or office using the optical fiber drop cable 109.

That is, the optical fiber drop cable 10
9 (outdoor line) from AO closure 107 to each utility pole 105
The drop cable is used when pulling an optical fiber to each drop point and from each drop point into a home or office.

As a conventional cable (109) for pulling down, there is a collective optical fiber drop cable 117 in which drop elements 113 are assembled around a tension member 115 (TM) as shown in FIG. The aggregate optical fiber drop cable 117 is mainly used to drop the AO closure 107 to the drop point of each utility pole 105.

More specifically, the collective optical fiber drop cable 117 has a structure in which the tension member 115 is sheathed to form a drop element 1 around a support wire portion 119.
A fictitious assembly optical unit 13 is wound around, and a sheath is not provided on the outermost layer in order to improve the workability of withdrawing in the middle.

The above-mentioned optical unit (drop element 113) for aerial assembly will be described by taking the upper one in FIG. 3 as a representative. For example, an optical fiber element wire 121 of 0.25 mmφ and this optical fiber element wire 121 will be described. 0.4 mmφ steel wires as a pair of tensile strength members 123 (tension members) arranged in parallel on both sides of the sheath 121 are covered together by a sheath 125, and both sides of the sheath 125 are cabled in the longitudinal direction. A tear notch 127 is provided.

Further, as another conventional cable for pulling down (109), there is a cable having a reduced diameter as shown in FIG. 4, which follows the SSD type optical fiber drop cable 129. . The optical fiber drop cable 129 is, for example, a 0.25 mm optical fiber element wire 131 and a pair of tensile strength members 133 (tension members) arranged in parallel on both sides of the optical fiber element wire 131 with the optical fiber element wire 131 interposed therebetween. The 4 mmφ steel wire is covered with the cable sheath 135 all at once.
A notch portion 137 for tearing the cable is provided on both sides of the optical element portion 139 so as to extend in the longitudinal direction, and a long optical element portion 139 is configured.

Further, the above optical element section 139,
A support wire 141 (tension member) made of a 1.2 mmφ steel wire is integrally connected to a support wire portion 145 covered with a sheath 143 through necks 147 which are parallel to each other and are constricted.

In addition, in the above-mentioned optical fiber drop cable 129 of FIG.
There is an optical fiber drop cable having a structure that accommodates about 8 optical fibers from the core. For example, an 8-fiber unit in which optical fiber element wires 131 are gathered around an interposition, a unit in which optical fiber wires are bundled, or the like is used. There is a structure to use.

[0011]

By the way, the conditions required for the cable for pulling down are (1) a cable accommodating about 4 to 8 cores of optical fiber,
(2) Since it may be bundled with other cables and installed, it is thin and lightweight, and (3) some optical fiber cores in the cables can be dropped on each floor of the building. In order to do so, the structure should be such that each intermediate core can be easily branched, (4) good loss characteristics and mechanical characteristics, (5) excellent manufacturability and low cost, etc. Can be given.

However, in the above-mentioned conventional cable for pulling down, the collective optical fiber drop cable 117 of FIG. 3 has a problem that the manufacturing cost is high because the outer diameter is large and there are many manufacturing processes. Further, the optical fiber drop cable 129 of FIG. 4 has a single core, and the optical fiber drop cable having a structure in which about 4 to 8 cores are unitized and housed has a problem that mechanical characteristics, particularly lateral pressure characteristics are inferior.

The present invention has been made to solve the above-mentioned problems, and its object is to improve the mechanical characteristics such as loss characteristics, lateral pressure characteristics, and core wire exitability by using a small diameter, for example, the closure of an overhead line. Therefore, it is an object of the present invention to provide an optical fiber drop cable that can be easily dropped while intermediately branching at each drop point of each power pole.

[0014]

In order to achieve the above object, an optical fiber drop cable of the present invention according to claim 1 is an optical fiber unit portion in which a plurality of optical fiber core wires are collectively covered with a unit sheath, and A long cable sheath portion in which at least a pair of first tensile strength members arranged in parallel on both sides of the optical fiber unit portion are covered with a cable sheath, and both side surfaces of the cable sheath portion are arranged in the longitudinal direction of the cable. A notch for cable tearing provided toward the side, and a long optical element part consisting of
It is characterized in that a long cable supporting wire portion in which a second strength member is covered with a sheath is fixed to the optical element portion in parallel with each other, and the unit sheath is made of a foaming resin.

Therefore, since the plurality of optical fiber core wires of the optical fiber unit portion are collectively covered with the unit sheath of foaming resin, there is a buffering effect against external stress and the lateral pressure characteristic is improved. The thickness of the cable sheath on the outside of the foamable unit sheath can be made thinner, and it is possible to manufacture it with a smaller diameter and lighter weight, so it is cheaper and loss characteristics and core wire exitability are improved. It

An optical fiber drop cable according to a second aspect of the present invention is the optical fiber drop cable according to the first aspect, wherein the unit sheath and the cable sheath are simultaneously continuous when the cable sheath is torn from the notch portion. It is characterized in that it is configured to be bonded so as to be broken.

Therefore, since the unit sheath and the cable sheath are adhered to each other, when the cable sheath is torn from the notch, the unit sheath is also continuously broken at the same time, and the core wire can be easily exposed.

The optical fiber drop cable of the present invention according to claim 3 is the optical fiber drop cable according to claim 1 or 2, wherein the unit sheath and the cable sheath are made of the same resin material or a resin material having substantially the same melting point. It is characterized by being configured.

Therefore, since the unit sheath and the cable sheath are made of the same resin material or a resin material having substantially the same melting point, the optical fiber unit portion and the pair of tensile strength members on both sides thereof are collectively formed by the cable sheath by extrusion molding. When covered, the surface of the unit sheath is melted by the heat at the time of extrusion molding, and the unit sheath and the cable sheath are reliably bonded without damaging the optical fiber unit portion.

The optical fiber drop cable of the present invention according to claim 4 is the optical fiber drop cable according to claim 1, 2 or 3, wherein the unit sheath has a foaming degree of 20 to 40% and a wall thickness of 0. It is characterized by being composed of 2 to 0.4 mm.

Therefore, the foaming degree of the unit sheath is 2
An optical fiber drop cable having a wall thickness of 0 to 40% and a thickness of 0.2 to 0.4 mm is a suitable condition for obtaining good lateral pressure characteristics, core wire ejection characteristics, and loss characteristics.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, an optical fiber drop cable 1 according to this embodiment is provided with an optical fiber unit portion 7 in which a plurality of optical fiber core wires 3 are collectively covered with a unit sheath 5. More specifically, in this embodiment, the optical fiber unit portion 7 has, for example, SM 0.25 mm strands of 0.4 as the eight optical fiber core wires 3.
A unit sheath 5 made of a foaming resin is formed as a unit so as to gather around a polyethylene interposition 9 of 5 mmφ.

In this embodiment, the unit sheath 5 is made of a material in which polyethylene is mixed with a foaming agent at 5%, the sheath thickness is 0.3 mm, and the sheath foaming degree is 4 mm.
It is 0%. This optical fiber unit 7 is about 1.5 mm
The diameter is φ.

As the foamable unit sheath 5, in addition to polyethylene, a thermoplastic resin such as polypropylene or polyamide, or a thermosetting resin such as polyurethane is mixed with a foaming agent and foamed according to the temperature at the time of extrusion molding. Those that utilize chemical foaming, or those that utilize gas foaming to inject gas during extrusion molding are preferably used.

A cable sheath in which, for example, 0.4 mmφ steel wires as at least a pair of first tensile strength members 11 (tension members; TM) are arranged in parallel on both sides of the optical fiber unit portion 7 with the optical fiber unit portion 7 sandwiched therebetween. A cable sheath portion 15 is formed by being collectively covered with 13. The cable sheath 13 is made of low density polyethylene and has a cable sheath width of about 4 mm and a thickness of about 2 mm.
It is finished with.

Also, the cable sheaths on both sides of the above-mentioned cable sheath portion 15, that is, in the linear direction that passes through the optical fiber unit portion 7 in a direction substantially orthogonal to the straight line passing through the pair of first tensile strength members 11 described above. A notch portion 17 for tearing the cable is provided on both side faces of the cable 13 in the longitudinal direction of the cable.

As described above, the pair of first tensile strength members 11 provided in parallel on both sides of the optical fiber unit 7 with the optical fiber unit 7 sandwiched therebetween.
A long optical element portion 19 is composed of a cable sheath portion 15 which is collectively covered with the cable sheath 13 and notch portions 17 for tearing the cable provided on both side surfaces of the cable sheath portion 15.

Further, the optical fiber drop cable 1
Is a long cable supporting wire portion 23 which is continuously or intermittently integrally fixed to the above-mentioned optical element portion 19 through a neck portion 21 constricted in parallel with the optical element portion 19.
It consists of and.

The above-mentioned cable supporting wire portion 23 is the second
For example, a support wire 25 as a strength member is covered with a sheath 27. For example, the sheath 27 is made of a resin such as low density polyethylene, and the support wire 25 is 1.
It is made of 2mmφ steel wire. The optical fiber drop cable 1 as a whole has a cable width of about 6 mm and a thickness of about 2 mm.
It is finished with.

With the above configuration, in the optical fiber drop cable 1 of the present invention, the plurality of optical fiber core wires 3 of the optical fiber unit portion 7 are collectively covered by the foamable unit sheath 5, so that they are protected against external stress. Has a buffering effect and improves lateral pressure characteristics. Therefore, the layer thickness of the cable sheath 13 outside the foamable unit sheath 5 can be reduced, and the diameter of the optical fiber drop cable 1 can be reduced.

Although the optical fiber drop cable 1 of the present invention has a good function even with the above-mentioned configuration, it has a two-layer sheath structure of the unit sheath 5 and the cable sheath 13, so that the notch portion 17 is formed. Should the cable sheath 13 be torn from the unit sheath 5
If it remains without being torn, the unit sheath 5 must be torn to take out the optical fiber core wire 3. In other words, it may be difficult to find the core wire.

Therefore, in order to allow the unit sheath 5 to be continuously broken at the same time when the cable sheath 13 is torn from the notch portion 17 so that the core wire can be easily exposed, in this embodiment, the unit sheath 5 and The cable sheath 13 is bonded.

As a method of adhering the unit sheath 5 and the cable sheath 13, a cable sheath process in which the optical fiber unit portion 7 and the pair of first tensile strength members 11 on both sides thereof are collectively covered with the cable sheath 13 by extrusion molding. Sometimes, there is a method in which the surface of the unit sheath 5 is melted by the heat of extrusion molding and the unit sheath 5 and the cable sheath 13 are adhered to each other. In this case, the unit sheath 5 and the cable sheath 13 are made of the same resin or a resin material having almost the same melting point.

The reason is that if the melting point of the unit sheath 5 is too high as compared with that of the cable sheath 13, the unit sheath 5 does not melt during the cable sheath process, so that the adhesion cannot be achieved. On the other hand, if the melting point of the unit sheath 5 is too low as compared with the cable sheath 13, the unit sheath 5 is melted in a large amount during the cable sheath process, and the foamed structure of the unit sheath 5 is broken. Not only does the effect of the lateral pressure characteristic disappear, but the loss characteristic may deteriorate in some cases.

As another bonding method, there is a method of bonding the contact surfaces of the unit sheath 5 and the cable sheath 13 with an adhesive. In this case, the unit sheath 5
And a cable sheath 1 including a pair of first strength members 11.
3 and 3 are made separately, and an adhesive is applied to the surface of the unit sheath 5 when the unit sheath 5 is incorporated into the cable sheath 13. As the adhesive, a styrene type or a urethane type is used.

In this embodiment, as described above, since the unit sheath 5 and the cable sheath 13 are made of polyethylene, which is the same resin material, there is a condition that the unit sheath 5 is easily softened by the temperature during extrusion molding. can get. Furthermore, the temperature of the extrusion molding during the cable sheath process is adjusted more finely, so that the unit sheath 5
The optical fiber drop cable 1 is manufactured under the condition that the surface of the is melted and sufficiently adhered to the cable sheath 13.

The optical fiber drop cable 1 of this embodiment obtained as described above has good loss characteristics, with the average loss after cable formation being 0.20 dB / km (1.55 μm). . Also, the lateral pressure characteristic is a load of 50 kg / 100 mm.
The loss increase in the width was 0.1 dB or less (1.55 μm), which was good. In addition, the bareness of the core wire is notched 17
It was confirmed that when the cable sheath 13 was torn, the unit sheath 5 was also torn at the same time, and the optical fiber core wire 3 could be easily exposed.

In order to compare with the optical fiber drop cable 1 of the above-mentioned embodiment and to define the range of each parameter, various optical fiber drop cables as comparative examples were manufactured as shown below.

Comparative Example 1 Optical Fiber Drop Cable without Unit Sheath 5 An optical fiber drop cable having the same dimensions as the optical fiber drop cable 1 shown in FIG. 1 but without the unit sheath 5 was manufactured. As a result of confirming the characteristics, it was determined that the lateral pressure characteristics had a loss of 0.1 dB or more at a load of 20 kg / 100 mm width, which was a problem in practical use.

(Comparative Example 2) Optical fiber drop cable using resin other than foaming resin for the unit sheath 5, as in the optical fiber drop cable of Comparative Example 1 described above, the lateral pressure characteristic was poor.

(Comparative Example 3) Foaming degree of the unit sheath 5,
Regarding the wall thickness, the foaming degree of the unit sheath 5 is 30% or more, and the wall thickness is 0.
Good lateral pressure characteristics, core wire ejection characteristics, and loss characteristics were obtained with an optical fiber drop cable of 2 mm or more. Also,
When the foaming degree is 50% or more, the productivity of the optical fiber drop cable becomes difficult. Further, if the wall thickness is 0.5 mm or more, the size becomes too large and the tearability of the cable is hindered. From the above, it was found that the degree of foaming is preferably about 20 to 40% and the wall thickness is preferably about 0.2 to 0.4 mm.

From the above, the optical fiber drop cable 1 of the present invention is a cable that accommodates the optical fiber core wires of about 4 to 8 cores, which is a condition required as a drop cable, and other cables. Since it may be laid in a bundle, it is small in diameter and lightweight, and it is easy to pull down some of the optical fiber cores in the optical fiber drop cable on each floor of the building. The structure that allows intermediate branching for each single core,
It satisfies various conditions such as good loss characteristics and mechanical characteristics, excellent manufacturability, and low cost.

The present invention is not limited to the above-described embodiment, but can be implemented in other modes by making appropriate changes.

[0045]

As can be understood from the above description of the embodiment of the invention, according to the invention of claim 1, the plurality of optical fiber core wires of the optical fiber unit portion are formed by the unit sheath of the foaming resin. Since they are collectively covered, a lateral pressure characteristic can be improved because a buffering effect against external stress is obtained. Further, since it can be manufactured to have a smaller diameter and a lighter weight, it can be manufactured at a low cost, and the loss characteristics and the core wire exitability can be improved. Therefore, it can be sufficiently used as a cable for withdrawal.

According to the second aspect of the invention, since the unit sheath and the cable sheath are adhered to each other, when the cable sheath is torn from the notch portion, the unit sheath can be continuously broken at the same time, and the core wire can be easily exposed.

According to the third aspect of the present invention, the unit sheath and the cable sheath are made of the same resin material or a resin material having substantially the same melting point. Since the surface is melted, the unit sheath and the cable sheath can be reliably bonded without damaging the optical fiber unit portion.

According to the fourth aspect of the invention, the foaming degree of the unit sheath is set to 20 to 40%, and the wall thickness of the unit sheath is set to 0.2 to 0.4 mm.
It is possible to obtain the core wire output property and the loss property.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an optical fiber drop cable according to an embodiment of the present invention.

FIG. 2 is a schematic explanatory view showing a wiring form of an optical fiber drop cable.

FIG. 3 is a cross-sectional view of a conventional aggregate optical fiber drop cable.

FIG. 4 is a cross-sectional view of a conventional optical fiber drop cable.

[Explanation of symbols]

1 Optical fiber drop cable 3 Optical fiber core 5 unit sheath 7 Optical fiber unit 9 Polyethylene intervention 11 First tensile member 13 Cable sheath 15 Cable sheath 17 Notch 19 Optical element section 21 neck 23 Cable support line 25 Support line (second tensile strength body) 27 sheath

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazunaga Kobayashi             1440 Rokuzaki, Sakura City, Chiba Prefecture Fujikura Ltd.             Sakura office (72) Inventor Masahiro Kusakari             1440 Rokuzaki, Sakura City, Chiba Prefecture Fujikura Ltd.             Sakura office (72) Inventor Shiaki Tanaka             1440 Rokuzaki, Sakura City, Chiba Prefecture Fujikura Ltd.             Sakura office (72) Inventor Keiji Ohashi             1440 Rokuzaki, Sakura City, Chiba Prefecture Fujikura Ltd.             Sakura office (72) Inventor Kimio Ando             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation (72) Inventor Hiroyuki Satsuki             Sumitomoden 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa             Ki Industry Co., Ltd. Yokohama Works F-term (reference) 2H001 BB21 BB27 DD06 DD11 HH02                       KK02 KK07 KK17 PP01

Claims (4)

[Claims] 1. A cable comprising an optical fiber unit portion in which a plurality of optical fiber core wires are collectively covered with a unit sheath, and at least a pair of first tensile strength members arranged in parallel on both sides of the optical fiber unit portion with the optical fiber unit portion interposed therebetween. A long optical element portion including a long cable sheath portion covered with a sheath and notch portions for cable tearing provided on both side surfaces of the cable sheath portion in the longitudinal direction of the cable is provided. (2) An optical fiber drop cable, characterized in that a long cable supporting wire portion in which a tensile strength member is covered with a sheath is fixed to the optical element portion in parallel with each other, and the unit sheath is made of a foaming resin. 2. The optical fiber according to claim 1, wherein the unit sheath and the cable sheath are adhered to each other so that when the cable sheath is torn from the notch, the unit sheath is also continuously broken. Drop cable. 3. The optical fiber drop cable according to claim 1, wherein the unit sheath and the cable sheath are made of the same resin material or a resin material having substantially the same melting point. 4. The unit sheath has a foaming degree of 20 to
The optical fiber drop cable according to claim 1, 2 or 3, wherein the optical fiber drop cable has a wall thickness of 40% and a thickness of 0.2 to 0.4 mm.