JPH09243880A - Optical fiber unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the waste of optical fibers by preventing the unused optical fibers from remaining in an optical fiber unit as far as possible at the time of executing the intermediate pull-down of an optical cable constituted by inserting the optical fiber unit into a pipe. SOLUTION: This optical fiber unit 20 is constituted by extrusion coating plural coated optical fiber ribbons 21 varying in lengths with an integral coating layer 24 in the state of aligning their one-side ends and aggregating the fiber ribbons. The lengths of the respective coated optical fiber ribbons 21 are so set that the end parts of the optical fibers 22 of the number of the fibers to be pulled down or above are positioned near the intermediate pull-down point after laying of the optical fiber unit 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber unit in which a plurality of optical fiber core wires are integrated, and in particular, an optical cable is constructed by pulling the optical fiber unit into a pipe laid in advance by a pneumatic method. The present invention relates to an optical fiber unit for pneumatic feeding / pulling in which is suitably used.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a conventional example of an optical fiber unit which is preferably used as an optical fiber unit for pneumatic feeding and drawing. Reference numeral 2 in the drawing denotes an optical fiber tape core wire, which is formed by arranging four optical fiber element wires 3 in parallel and coating them all together with an ultraviolet curable resin or the like. The optical fiber unit 1 of this example has a structure in which four optical fiber ribbons 2 are laminated and a collective coating layer 4 made of foamed polyethylene is formed around them to have a circular cross section. Has been done.

The optical fiber unit 1 thus constructed is laid by a pneumatic feeding method as shown in FIG.
That is, first, the pipe 10 is laid, the optical fiber unit 1 is inserted from one end side of the pipe 10, and at the same time, air is blown at a high speed, and the optical fiber unit 1 is placed on the air stream to run to the other end side. is there. In this way, the optical fiber unit can be laid by inserting the multi-fiber optical fiber unit 1 into the single pipe 10. Generally, an optical cable is constructed by assembling a plurality of such pipes 10.

By the way, in the multi-core optical cable constructed as described above, after installation, if necessary, a part of the optical fiber element wire 3 constituting the optical fiber unit 1 is branched in the middle of the optical cable. The so-called intermediate withdrawal is performed. The position where this intermediate drawing is performed is called the intermediate drawing point, and the number of optical fiber strands that are drawn is called the number of drawn cores.

In the case of the optical fiber unit 1 using the optical fiber ribbon 2 as shown in FIG. 3, it is general that the intermediate withdrawal is performed in units of the optical fiber ribbon 2. Specifically, for example, the pipe 10 is partially cut and removed at the intermediate pull-down point, the housed optical fiber unit 1 is pulled out, and the collective coating layer 4 is partially removed, so that a required number of light beams can be obtained. The fiber tape core wire 2 is cut. Then, the cut end portion is pulled out from the optical fiber unit 1 and connected to another pulling-down optical fiber tape core wire or the like. However, in the case of performing the intermediate pull-down in this way, one end side of the cut optical fiber tape core wire 2 is used for transmission, but the other end side is not used for anything and is wasted. I will end up.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate an unused optical fiber in an optical fiber unit when intermediately dropping an optical cable formed by inserting the optical fiber unit into a pipe. The purpose is to reduce the waste of the optical fiber by avoiding the remaining.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is an optical fiber unit in which a plurality of optical fiber core wires are integrated by a collective coating layer. The optical fiber unit is characterized in that the number of optical fiber core wires is reduced in the longitudinal direction from one end to the other end. Such an optical fiber unit can be configured by collectively covering a plurality of optical fiber core wires having different lengths, with one end aligned and assembled together. Also, between the first intermediate pull-down point after laying the optical fiber unit and the second intermediate pull-down point or the other end of the optical fiber unit which is on the other end side and is closest to the first intermediate pull-down point. In addition, it is preferable that the end portion of the optical fiber whose number is equal to or larger than the number of cores at the first intermediate point is located.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
1A and 1B show an embodiment of an optical fiber unit of the present invention. FIG. 1A is a front view seen from one end side, FIG. 1B is a side view, and FIG. 1C is a front view seen from the other end side. Symbol 2 in the figure
1 is an optical fiber tape core wire, which are arranged in parallel 4
The optical fiber elemental wires 22 of the book are collectively covered with the coating layer 23. The optical fiber unit 20 of this embodiment
Is made by stacking one ends of four optical fiber ribbons 21 having different lengths so that their end faces are flush with each other, and extruding a collective coating layer 24 around them to have a circular cross section. Is formed. As the material of the collective coating layer 24, the same foamed polyethylene as that used in the conventional optical fiber unit can be used.

The length of each of the optical fiber tape core wires 21 forming the optical fiber unit 20 is set as follows when the intermediate drawing point and the number of drawing cores are known in advance. That is, when the optical fiber unit 20 is laid, the first intermediate pull-down point and the second intermediate pull-down point located on the other end side and closest to the first intermediate pull-down point are It is set so that the end portion of the optical fiber element wire 22 having the number of withdrawal cores or more at the first intermediate withdrawal point is located. Further, when there is no other withdrawal point on the other end side than the first intermediate withdrawal point, the withdrawal center at the first intermediate withdrawal point is provided between the first intermediate withdrawal point and the other end of the optical fiber unit. It is set so that the end portions of the number of the optical fiber strands 22 or more are positioned.

The optical fiber ribbon 21 to be used for pulling at the first intermediate pulling point is too short,
When the other end is located on the one end side with respect to the first intermediate pull-down point, the optical fiber ribbon core wire 21 cannot be pulled down. Further, if the other end reaches the second drop point or the other end of the optical fiber unit 20 because it is too long, the workability of the second drop point or the drop in the optical fiber unit 20 may be deteriorated. The shorter the distance between the intermediate withdrawal point and the other end of the optical fiber tape core wire 21 used for the withdrawal here, the shorter the length of the useless optical fiber tape core wire 21 that occurs after the withdrawal is preferable. Theoretically, with the optical fiber unit 20 laid, as many optical fiber strands 2 as the number of cores to be dropped at the intermediate pulling point.
Although it is desirable that the other end of the optical fiber 2 be located at the other end, the optical fiber unit 20 normally meanders while being inserted into the pipe, and therefore, the intermediate withdrawal point and the optical fiber ribbon 21 (optical fiber). It is actually difficult to exactly match the other end of the wire 22).

For example, the four-core optical fiber element wire 22 is pulled down in the vicinity of the point A, which is separated from the one end O of the optical fiber unit 20 having the total length d by the distance a, and the distance b (a <a
It is planned to pull down the four-core optical fiber element wire 22 near the point B which is separated by b), and to drop the four-core optical fiber element wire 22 near the point C which is separated by a distance c (b <c) from the above O. In this case, the lengths L ₁ , L ₂ and L ₃ of _three of the four optical fiber ribbons 21 are respectively set as a <L ₁ <b, b <L ₂ <c and c. <L ₃ <d, preferably about several m longer than a, b and c, respectively.

The order of stacking the four optical fiber ribbons 21 is not particularly limited, but between the optical fiber tapes 21 used for pulling down and the peripheral surface of the optical fiber unit 20 at the pulling down point. If another optical fiber ribbon 21 exists in the optical fiber tape, the workability of pulling it down deteriorates.
It is necessary to stack 1 so as not to be sandwiched between the optical fiber ribbons 21 longer than this. In this embodiment,
The longest optical fiber tape core wire 21 is arranged near the center, and the optical fiber tape core wire 21 having a length L _{2 and} the optical fiber tape core wire 21 having a length L ₃ are laminated so as to sandwich the optical fiber tape core wire 21 and the length L ₃ L ₁ on the optical fiber ribbon 21 of
Optical fiber tape core wires 21 of (L ₁ <L ₂ <L ₃ ) are laminated. In addition, it is preferable that the four optical fiber ribbons 21 having different lengths can be visually distinguished from each other when they are viewed from the peripheral surface. For that purpose, for example, the optical fiber ribbons 21 are formed. The coating layer 23 present may be colored appropriately.

In order to manufacture the optical fiber unit 20 of this embodiment, for example, four optical fiber tape core wires 21 are laminated as shown in FIG. 1, and this is formed into a molding die having a die hole with a circular cross section. 4 optical fiber ribbons 2
The collective coating layer 24 made of foamed polyethylene may be extrusion-coated through the one end on which 1 is laminated. When this extrusion coating is performed, the number of the optical fiber ribbons 21 gradually decreases from one end side to the other end side of the optical fiber unit 20, and accordingly, the supply rate of the foamed polyethylene is increased. Preferably. The optical fiber unit 20 manufactured in this manner has a circular cross-sectional shape, although the outer diameter slightly decreases from one end side to the other end side as the number of the optical fiber tape core wires 21 decreases. Held in.

FIG. 2 shows the optical fiber unit 20 of this embodiment.
3 schematically shows an example of laying. The optical fiber unit 20 is an optical cable pipe 10 that has been laid in advance.
It is inserted by the pneumatic method. Reference symbol A,
B and C indicate intermediate withdrawal points, respectively. The side where the four optical fiber ribbons 21 are assembled is defined as one end side. As shown in this figure, in the optical cable using the optical fiber unit 20 of the present embodiment, one optical fiber is provided on the other end side of the optical cable for a few meters from each intermediate pull-down point A, B, C. The other end of the tape core wire 21, that is, the other end of the four optical fiber element wires 22 is located.

In order to pull down the optical cable laid in this way, first, at each pulling point, the pipe 10 is cut off for a length of about 300 to 500 mm,
The optical fiber unit 20 is pulled out from here. here,
In order to pull out the optical fiber unit 20 from the pipe 10, the optical fiber unit 2 is previously set at the pull-down point.
It is preferable that 0 has an extra length. For that purpose, for example, when the optical cable is laid, the optical cable may have an extra length at the pulling point. When the optical fiber unit 20 is pulled down, the optical fiber unit 20 can be pulled out by cutting the part of the pipe 10 as described above and then pushing the entire optical cable in the longitudinal direction toward the center of the optical cable.

Next, the drawn optical fiber unit 20
Part of the collective coating layer 24 is removed, the optical fiber ribbon 21 to be branched is cut, and the cut end on one end side from the cutting position is taken out. Then, the cut end thus taken out is connected to another optical fiber core wire 30 for drawing as shown by a broken line in FIG.
The optical fiber strand 22 of the heart can be branched and withdrawn. It is desirable to repair the optical fiber unit 20 in which the collective coating layer 24 is partially removed after the removal, using a vinyl tape, a filler, or the like, but such repair is not necessary. Also, a partially cut pipe 1
For 0, a repair procedure such as attaching a simple closure to the excised portion or winding a vinyl tape is performed.

According to the optical fiber unit 20 of this embodiment, the number of the optical fiber ribbons 21 is reduced in the longitudinal direction of the optical fiber unit 20, and the reduced location and the reduced number are the optical fiber unit 20. It is almost the same as the intermediate withdrawal point and the number of withdrawals after installation.
Therefore, it is possible to pull out the optical fiber tape core wire 21 whose other end is located in the vicinity of the intermediate pull-down point and use it for intermediate pull-down. In this way, useless optical fiber tape remaining in the optical fiber unit after intermediate pull-down The number of core wires 21 can be reduced as compared with the conventional one. Further, in the optical fiber unit 20 of the present embodiment, the four optical fiber ribbons 21 are arranged such that the shorter optical fiber ribbons 21 are located outside the longer optical fiber ribbons 21. It is stacked. Therefore, when performing intermediate pull-down at a plurality of points of the optical cable, the optical fiber tape core wire 21 on the outer side is sequentially pulled out from one end side to the other end side of the optical cable, and the optical fiber tape core wire 21 is pulled out. Can be done smoothly. Furthermore, if the four optical fiber tape core wires 21 forming the optical fiber unit 20 can be visually identified when the peripheral surfaces are viewed, branching and connection can be performed reliably. It is effective for quick execution.

Further, each intermediate pull-down point A of the optical cable,
It is desirable to match B and C with the other end of each optical fiber tape core wire 21, respectively. In this case, the optical fiber tape core wire 21 is not cut near each intermediate pull-down point and the optical fiber tape core wire 21 is not cut. The other end of the core wire 21 may be pulled out and connected to the optical fiber tape core wire 30 or the like for withdrawal. In this way, no wasteful optical fiber ribbon 21 is left in the optical fiber unit 20 after the intermediate drawing.

In the present embodiment, an example in which four optical fiber tape core wires 21 are laminated to form the optical fiber unit 20, but the optical fiber element forming the optical fiber tape core wire 21 is described. The number of wires 22 (the number of cores) and the number of laminated optical fiber ribbons 21 can be set arbitrarily. Further, the optical fiber core wire in the present invention is not limited to the optical fiber ribbon core wire, and other forms of optical fiber core wire can be used, and a single-core optical fiber core wire may be used.
Further, the form in which a plurality of optical fiber core wires are assembled can be appropriately changed.

[0020]

【Example】

Example 1 An optical fiber unit having the structure shown in FIG. 1 was produced. That is, first, four optical fiber strands were arranged in parallel, and four optical fiber ribbons each having a coating layer collectively coated on the periphery thereof were prepared. The length of each optical fiber tape is 350 m (corresponding to A) and 400 m
(Core B), 450 m (core C), 500
m (corresponding to core D). Further, the coating layers were colored in different colors so that the optical fiber ribbons could be visually identified. Next, one ends of these four optical fiber ribbons were aligned and laminated so that their end faces were flush with each other. As for the stacking order, the core wire B and the core wire C were stacked so as to sandwich the core wire D, and the core wire A was stacked on the core wire C.

Subsequently, the four optical fiber ribbons thus laminated are passed through a molding die from one end thereof,
A collective coating layer made of expanded polyethylene was formed around the periphery to obtain an optical fiber unit having a circular cross section. The outer diameter of the optical fiber unit is 2.3 mm at one end and 2.1 mm at the other end.
Met. The optical fiber unit thus obtained, in a pipe made of polyethylene laid in advance,
It was inserted and laid by the pneumatic feeding method. The pumpability was good. After laying, the distance from the pipe end on one end side is 35
The intermediate withdrawal of the cord A, the cord B, and the cord C was performed at the positions of 0 m, 400 m, and 450 m, respectively. The workability of withdrawal was good.

[0022]

As described above, according to the optical fiber unit of the present invention, the length of the optical fiber core which is not used for optical transmission and remains in the optical fiber unit when the intermediate drawing is performed after the installation is performed. Can be shortened. Therefore, waste of the optical fiber core wire can be reduced, and the material cost can be reduced.

[Brief description of drawings]

FIG. 1 shows an embodiment of an optical fiber unit of the present invention, (a) is a front view of one end side, (b) is a side view,
(C) is a front view of the other end side.

FIG. 2 is an explanatory diagram showing an example of laying the optical fiber unit of the present invention.

FIG. 3 is a sectional view showing an example of a conventional optical fiber unit.

FIG. 4 is an explanatory diagram of a pneumatic feeding method.

[Explanation of symbols]

20 ... Optical fiber unit, 21 ... Optical fiber ribbon, 24 ... Collective coating layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinji Araki 1440 Rokuzaki, Sakura City, Chiba Prefecture Fujikura Ltd. Sakura Factory

Claims (3)

[Claims] 1. An optical fiber unit in which a plurality of optical fiber cores are integrated by a collective coating layer, wherein the number of optical fiber cores decreases in the longitudinal direction from one end of the optical fiber unit to the other end. An optical fiber unit characterized in that 2. A plurality of optical fiber core wires having different lengths,
An optical fiber unit characterized in that it is collectively covered in a state where one end is aligned and gathered. 3. A first intermediate withdrawal point after laying an optical fiber unit and a second intermediate withdrawal point or an optical fiber unit or the like which is on the other end side and is closest to the first intermediate withdrawal point. The optical fiber unit according to claim 1 or 2, wherein the end portion of the optical fiber having the number of withdrawal cores or more at the first intermediate withdrawal point is located between the end and the end.