JP2004191506A - Optical cable - Google Patents

Abstract

An optical cable that improves workability and reduces transmission loss by setting a filling length of an intermittent fixing material that is intermittently filled to an appropriate value.
An optical fiber 3 is accommodated and arranged in an internal space 7 formed by bending two forming tapes 5a and 5b in a substantially semicircular arc shape and facing each other. Is filled to 500 mm or less and 10 mm or more. The tensile strength members 11a and 11b are arranged in the vicinity of the center of the two forming tapes 5a and 5b, and the lip cords 13a and 13b are arranged at the joints so that the sheaths are collectively sheathed. And an optical cable capable of suppressing transmission loss due to movement and contact of the optical fiber within the internal gap.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical cable having post-branchability, and more particularly to an optical cable that can improve workability and reduce transmission loss.
[0002]
[Prior art]
Conventionally, an optical cable 101 having a structure as shown in FIG.
[0003]
In FIG. 4, an optical fiber 103 represents a plurality of optical fiber wires, and is loosely housed in an internal space 107 in a pair of forming pipes 105 having a substantially semicircular arc shape. The forming pipe 105 is covered with a sheath 109 made of polyethylene, plasticized polyvinyl chloride, or the like. The sheath 109 is formed by a usual extrusion coating method. Further, in the sheath 109, two strength members 111, 111 made of a metal wire such as a steel wire or a brass wire or a fiber reinforced plastic, and two lip cords 113, 113 made of a plastic string or the like are embedded. Have been.
[0004]
The strength members 111 are arranged symmetrically with respect to the optical fiber 103, and the two lip cords 113, 113 are on a line orthogonal to a line (y-axis in the drawing) connecting the two strength members 111, 111. (X-axis in the figure) are arranged symmetrically with the optical fiber 103 interposed therebetween.
[0005]
Further, in the forming pipe 105, an intermittent fixing member (not shown) made of a soft hot melt adhesive or the like for supporting the plurality of optical fibers 103 and loosely accommodating the optical fiber 103 in the internal space 107 of the forming pipe 105 is provided. It is intermittently filled in the longitudinal direction.
[0006]
In the optical cable 101 having such a structure, when the optical cable 101 is branched, the optical cable is split into two parts by pulling both the lip cords 113 and tearing the sheath 109 to take out the housed optical fiber 103. Can be.
[0007]
[Patent Document 1]
JP-A-2002-122763
[Problems to be solved by the invention]
The optical cable 101 having the above-described structure is filled with an intermittent fixing material to suppress the lateral movement of the optical fiber 103 accommodated in the internal space 107 of the forming pipe 105 with respect to the cross section. Thereby, the lateral movement of the optical fiber 103 can be suppressed, but the filling length of the intermittent fixing material is not particularly defined. Therefore, where the filling length of the intermittent fixing material is long, workability in the post-branching operation is poor. In addition, when the filling length of the intermittent fixing material is short and the space where the intermittent fixing material is not filled is long, the optical fibers 103 move in the air gap, so that the optical fibers 103 come into contact with each other to reduce transmission loss characteristics. There is.
[0009]
Incidentally, the stripping length of an optical cable laid aerial is generally 500 mm, and the stripping length of an optical cable laid underground is 700 mm. Therefore, if the filling length of the intermittent fixing material is longer than this length, the intermittent fixing material is filled over the entire area of the peeling length at the time of intermediate branching, and stress is applied to the optical fiber when taking out the optical fiber, causing loss. There is a problem.
[0010]
The present invention has been made in view of the above, and has as its object to improve the workability by setting the filling length of the intermittent fixing material that is intermittently filled to an appropriate value, and to improve the transmission loss of the optical fiber. An object of the present invention is to provide an optical cable capable of reducing the number of optical cables.
[0011]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an optical fiber comprising a plurality of optical fiber wires, a pair of forming tapes bent in a substantially semicircular arc shape, and end portions of the pair of forming tapes. The optical fiber is accommodated in a cylindrical internal space which is arranged facing each other at a predetermined interval, and a pair of strength members disposed opposite to the outer periphery of the forming tape and a joint of the pair of forming tapes A pair of lip cords disposed to face each other in the vicinity, and a forming tape that encloses the optical fiber, a sheath that collectively accommodates the strength member and the lip cord, and the sheath that is enclosed by tearing the sheath. An optical cable from which an optical fiber can be taken out, wherein a filling length having a length equal to or less than the peeling length of the sheath and equal to or greater than 10 mm is provided in the internal space. Erare, intermittent fixing material in the fill length is summarized in that being filled.
[0012]
According to a second aspect of the present invention, in the optical cable according to the first aspect, the filling length is set to be equal to or less than the length of the erection closure and equal to or more than 10 mm.
[0013]
Further, the invention according to claim 3 is, in the optical cable according to claim 1, wherein the filling length is not more than the length of the underground closure and not less than 10 mm.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
(First Embodiment)
FIG. 1 is a cross-sectional view illustrating a configuration of an optical cable 1 according to a first embodiment of the present invention. Specifically, FIG. 1A is a diagram illustrating a cross section and an appearance of the optical cable, and FIG. () Is a cross-sectional view as viewed from the side.
[0016]
The optical cable 1 shown in FIG. 1 includes an optical fiber 3 composed of a plurality of optical fiber strands, a pair of substantially semicircular forming tapes 5 a and 5 b, an internal space 7 for accommodating the optical fiber 3, and an optical fiber 3. Length 19 that suppresses the movement of the cable, tensile strength members 11a and 11b that absorb the tension in the extension direction, lip cords 13a and 13b used to tear the sheath, and the sheath 9 that accommodates these cable components. Protrusions 15a, 15b are formed beside the lip cords 13a, 13b.
[0017]
Here, the optical fiber 3 is, for example, a set of 20 SM-type optical fiber wires each having a diameter of 250 μm, which are obtained by coating a bare optical fiber having a core diameter of 10 μm and a cladding diameter of 125 μm with UV resin or the like. .
[0018]
The forming tapes 5a and 5b are high-rigidity laminated films having a width of 5.2 mm. The laminated films are bent in a substantially semicircular arc shape and arranged to face each other to form a cylindrical internal space 7 inside.
[0019]
The strength members 11a and 11b are made of a metal wire such as a steel wire or a brass wire or a fiber-reinforced plastic, and are arranged at symmetrical positions with the cylindrical forming tapes 5a and 5b interposed therebetween. Specifically, this arrangement position is the central portion (near the peak of the mountain shape) of the semicircular forming tapes 5a and 5b.
[0020]
The lip cords 13a and 13b are made of a string obtained by twisting fibers of about 6000d (denier) such as aramid fiber or plastic, and are formed in a cylindrical shape on a line perpendicular to a line connecting the two tensile members 11a and 11b. Are formed symmetrically with respect to the forming tapes 5a and 5b.
[0021]
The sheath 9 is made of polyethylene, plasticized polyvinyl chloride, or the like. The molding method is performed by a usual extrusion coating method. In the sheath 9, two strength members 11a and 11b and two lip cords 13a and 13b are embedded so as to be vertically attached to the optical fiber 3.
[0022]
The plurality of optical fibers 3 housed in the internal space 7 formed by the forming tapes 5a and 5b are loosely housed in the internal space 7. Therefore, these optical fibers 3 are intermittently fixed with a soft intermittent fixing member or the like so as not to move in the lateral direction with respect to the cross section of the optical cable.
[0023]
The intermittent fixing material is, for example, a soft styrene-based thermoplastic resin. The intermittent fixing member is not limited to this, and is not particularly limited as long as it can maintain a predetermined optical cable bending characteristic while suppressing lateral movement. That is, jelly or the like may be used. That is, a specific example is OP308 (BP Chemical) composed of an α-olefin-based oil.
[0024]
The filling length 19 of such an intermittent fixing material is 500 mm or less when the stripping length of the sheath 9 is 500 mm, and is 700 mm or less when the stripping length is 700 mm. The filling length 19 of the intermittent fixing material is desirably 10 mm or more from the viewpoint of manufacturability, and the lower limit length is 10 mm.
[0025]
In the present embodiment, the filling length 19 of the intermittent fixing material is specified to be 500 mm or less or 700 mm or less. However, the filling length 19 is not limited to this, and may be shorter than the peeling length. That is, the peeling length of 500 mm is set based on the length of the erection closure installed on the telephone pole. The peeling length of 700 mm is set based on the length of an underground closure installed under the manhole. Therefore, the filling length 19 of the intermittent fixing material is changed according to the length of the closure. That is, the length may be equal to or less than the skinning length based on the skinning length.
[0026]
Therefore, when a peeling length of 500 mm is required, it is preferable that at least the filling length 19 be 400 mm and the unfilled length be 100 mm.
[0027]
Next, the operation and effect of the optical cable 1 will be described.
[0028]
First, as shown in FIG. 1, a plurality of (for example, 20) optical fibers 3 are prepared.
[0029]
Next, the two forming tapes 5a and 5b are bent into a substantially semicircular arc shape, and the ends parallel to the longitudinal direction of the forming tapes 5a and 5b are aligned to form an internal space 7 so that the inside becomes cylindrical. Simultaneously with the formation, the optical fiber 3 is accommodated and arranged in the internal space 7, and the intermittent fixing member is filled with a length of 400 mm, and the filling length of 100 mm is repeated. On the other hand, the ends of the two forming tapes 5a and 5b have a gap of about 0.5 to 1.5 mm.
[0030]
Next, the sheath 9 is extrusion-coated so as to cover the two forming tapes 5a and 5b including the optical fiber 3 therein.
[0031]
In the extrusion coating method, a thermoplastic resin is extruded and formed on the outer circumference of the cylindrical forming tapes 5a and 5b in which the optical fibers 3 are accommodated. At this time, strength members 11a and 11b that absorb tension in the extension direction are arranged one by one near the center of the two substantially semicircular forming tapes 5a and 5b, respectively. The lip cords 13a and 13b used for peeling the sheath 9 are arranged at the alignment of 5b, and the protrusions are provided beside the lip cords 13a and 13b so that the housing positions of the lip cords 13a and 13b can be identified from the outside. 15a and 15b are continuously provided in the longitudinal direction. The optical cable 1 is formed by extruding and covering the above members at once from a mold opening having such a cross section.
[0032]
That is, in the present embodiment, the two forming tapes 5a and 5b are bent into a substantially semicircular arc shape, and the ends parallel to the longitudinal direction of the forming tapes 5a and 5b are arranged so as to face each other at a constant interval. The optical fiber 3 is accommodated and arranged in the cylindrical internal space 7 and the intermittent fixing material is filled at a predetermined length and at a predetermined interval. Near the center of the two substantially semicircular forming tapes 5a and 5b, Tensile strength members 11a and 11b that absorb the tension in the elongation direction are longitudinally attached, and lip cords 13a and 13b for tearing the sheath 9 are vertically aligned at the alignment of the two substantially semicircular forming tapes 5a and 5b. These are packaged and sheathed together.
[0033]
In the optical cable 1 thus formed, the optical fiber 3 housed therein can be taken out by pulling the lip cords 13a and 13b left and right and tearing the sheath 9. FIG. 3 is a view showing a state in which the optical fiber 3 is exposed by tearing the sheath 9.
[0034]
Also, by cutting the sheath 9 from an arbitrary side position of the optical cable 1 with a cutter or the like (500 mm), an unfilled length of about 100 mm exists in at least a part of the cut area. Can be.
[0035]
(Comparative Example 1)
With reference to the comparison table shown in FIG. 2, the optimum value of the filling length 19 of the optical cable 1 according to the first embodiment is determined.
[0036]
Therefore, three types of optical cables were prepared and their workability and transmission loss were compared. Specifically, the three types of optical cables are an optical cable having a filling length 19 of 400 mm, an optical cable having a filling length 19 of 500 mm, and an optical cable having a filling length 19 of 700 mm.
[0037]
Further, in this comparative experiment, the peeling length was generally the peeling length performed during the installation work. That is, it is 500 mm in accordance with the aerial installation and 700 mm in accordance with the underground installation. Therefore, these optical cables were determined under the above conditions in terms of workability and transmission loss.
[0038]
When the three types of optical cables are stripped with a predetermined stripping length, the workability is determined from the ease of taking out the optical cables, and the determination method is based on the difference between the transmission loss before taking out from the optical cable and the transmission loss after taking out. The amount of change was determined, and the transmission loss was determined from the amount of change. In addition, those with 0.00 dB of variation were classified as good (良好), those with 0.00 to 0.01 dB as slightly good (△), and those with 0.01 dB or more as poor (×).
[0039]
As a result, as shown in FIG. 2, when the filling length 19 was 400 mm and the peeling length was 500 mm, both the workability and the change in transmission loss were good.
[0040]
When the filling length 19 was 500 mm and the peeling length was 500 mm, the workability was somewhat difficult, and the change in transmission loss was determined to be poor.
[0041]
Further, when the filling length 19 was 700 mm and the peeling length was 500 mm, both the workability and the change in transmission loss were poor.
[0042]
Next, as shown in the figure, when the filling length 19 was 400 mm and the peeling length was 700 mm, both the workability and the change in transmission loss were good.
[0043]
When the filling length 19 was 500 mm and the peeling length was 700 mm, the workability and the change in transmission loss were good as described above.
[0044]
However, when the filling length 19 was 700 mm and the peeling length was 700 mm, the workability was slightly good, but the change in transmission loss was poor.
[0045]
Therefore, the above results show that, in the optical cable for aerial laying having a peeling length of 500 mm, it is appropriate from the viewpoint of workability and transmission loss if the filling length 19 for filling the intermittent fixing material is 400 mm or less. In addition, in the case of an underground laying optical cable having a peeling length of 700 mm, it was shown that the filling length 19 for filling the intermittent fixing material was set to 500 mm or less from the viewpoint of workability and transmission loss.
[0046]
If it is intended to satisfy both the aerial use and the underground use, the filling length 19 can be satisfied by making the filling length 19 shorter than 500 mm. At this time, the unfilled length cannot be 100 mm, but the value of 100 mm means that it is desirable.
[0047]
Therefore, by setting the upper limit of the filling length 19 to be equal to or less than the peeling length and setting the lower limit to be equal to or more than 10 mm, the workability at the time of the post-branching operation is poor where the filling length 19 of the intermittent fixing material, which is a conventional problem, is long. To solve the problem that the intermittent fixing material has a short filling length 19 and a long interval where the intermittent fixing material is not filled moves in the optical fiber gap, so that the optical fibers come into contact with each other and transmission loss characteristics are reduced. Can be.
[0048]
【The invention's effect】
Therefore, according to the present invention, the two forming tapes 5a, 5b are bent into a substantially semicircular arc shape, and the ends parallel to the longitudinal direction of the forming tapes 5a, 5b are arranged so as to face each other at a predetermined interval, and the inside is cylindrical. The optical fiber 3 is accommodated and arranged in the cylindrical internal space 7 thus formed, and the internal space 7 is filled with an intermittent fixing material of 500 mm or less and 10 mm or more. At this time, the interval (unfilled length) at which the intermittent fixing material is not filled is at least 100 mm. The tensile strength members 11a and 11b are arranged near the center of the two forming tapes 5a and 5b, and the lip cords 13a and 13b are arranged at the joints. And an optical cable capable of suppressing transmission loss due to movement and contact of the optical fiber within the internal gap.
[Brief description of the drawings]
FIGS. 1A and 1B are an external view (a) and a side sectional view (b) showing a configuration of an optical cable 1 according to a first embodiment of the present invention.
FIG. 2 is a comparison table illustrating workability and transmission characteristics of the optical cable 1 according to the present embodiment.
FIG. 3 is a view showing a state in which the optical fiber 3 is exposed by tearing a sheath 9;
FIG. 4 is a cross-sectional view showing a configuration of a conventional optical cable 101.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical cable 3 ... Optical fiber 5a, 5b ... Forming tape 7 ... Internal cavity 9 ... Sheath 11a, 11b ... Strength member 13a, 13b ... Lip cord 15a, 15b ... Protrusion part 17 ... Printing part 19 ... Filling length 21a, 21b, 23 intermittent projection 101 optical cable 103 optical fiber 105 forming pipe 107 internal cavity 109 sheath 111 tensile strength member 113 lip cord

Claims (3)

An optical fiber composed of a plurality of optical fiber strands;
A pair of forming tapes bent in a substantially semicircular shape,
The optical fiber is accommodated in a cylindrical internal space formed by arranging the ends of the pair of forming tapes facing each other at a predetermined interval, and a pair of strength members disposed opposite to the outer periphery of the forming tape. ,
A pair of lip cords which are arranged opposite to each other near a joint of the pair of forming tapes;
An optical cable that has the forming tape enclosing the optical fiber, a sheath that collectively accommodates the strength member and the lip cord, and that can tear out the sheath to take out the encapsulated optical fiber,
An optical cable, wherein the internal space is filled with an intermittent fixing material to a filling length having a length equal to or less than the peeling length of the sheath and equal to or greater than 10 mm. 2. The optical cable according to claim 1, wherein the filling length is equal to or less than the length of the installation closure and is equal to or greater than 10 mm. The optical cable according to claim 1, wherein the filling length is equal to or less than the length of the underground closure and equal to or more than 10 mm.

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