JPH07218784A - Slot rod and slot unit of optical fiber cable - Google Patents

Abstract

PURPOSE:To greatly improve the density of the optical fiber cable by forming many spiral grooves, which each have a narrow spiral groove formed in the bottom part of its wide spiral groove, as optical fiber storage grooves. CONSTITUTION:Many spiral grooves are formed as the optical fiber storage grooves by forming narrow spiral grooves 23 in the bottom parts of wide spiral grooves 22. The wide spiral grooves 22 are deep enough to secure necessary strength with the thickness t1 of the rib at the bottom parts of the wide spiral grooves 22, and the narrow spiral grooves 23 formed in their bottom parts are deep enough to secure necessary strength with the thickness t2 of the rib at the bottom parts of the narrow spiral grooves 23. Then narrow ribbons 25 of optical fibers are put in the narrow spiral grooves 23 and wide ribbons 27 of optical fibers are put in the wide spiral grooves 22. Therefore, the storage density of optical fibers is increased by as much as the narrow ribbons 25 of optical fibers are stored in the narrow spiral grooves 23, thereby making the density of ribbons of optical fibers high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slot rod of an optical fiber cable, and more particularly to the shape of a spiral groove for accommodating the optical fiber tape, and the number of optical fiber tapes that can be accommodated in one slot rod. Can be dramatically increased, which can increase the density of the optical fiber cable.

[0002]

2. Description of the Related Art There are various cross-sectional shapes of synthetic resin slot rods for optical fiber cables which are manufactured by extrusion with a tension member buried in the center and have an optical fiber tape accommodating groove on the outer periphery. A device having a large number of radial storage grooves (see FIG. 3) has been conventionally known as a device capable of storing fiber tapes at a high density (hereinafter, referred to as "conventional slot rod"). In recent years, there has been a demand for higher density optical fiber cables,
In order to meet this demand, the spiral groove 2 of the slot rod 10 must be deepened to increase the number of optical fiber tapes that can be accommodated in one groove. However, when the depth of the spiral groove 2 is increased, the wall thickness A (see FIG. 3) at the root of the rib 3 between the grooves is reduced, and the rib has insufficient strength. Therefore, there is a limit in increasing the depth of the spiral groove 2, and there is a limit in increasing the density in the cross-sectional shape of the conventional slot rod. For this reason, conventionally, the diameter of the optical fiber is made as small as possible, the optical fiber coating layer is made as thin as possible, and the protective layer of the optical fiber is made as thin as possible. However, it is very difficult to dramatically increase the density in the future only by taking such measures. In order to dramatically improve the density of optical fiber cables in the future, it is important to devise the shape and structure of the slot rod so that the number of tapes that can be accommodated in the slot rod can be increased as much as possible. Become.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to improve the density of the conventional slot rod by devising the cross-sectional shape of the spiral groove.

[0004]

Means for Solving the Problems In the means taken for solving the above problems, a narrow spiral groove is formed at the bottom of a wide spiral groove to form an optical fiber storage groove as a multi-step spiral groove. That is.

[0005]

[Operation] The depth of the wide spiral groove should be such that the wall thickness of the rib at the bottom of the wide spiral groove ensures the necessary strength, and the depth of the narrow spiral groove formed at the bottom is also The thickness of the ribs at the bottom of the narrow spiral groove is set so that the required strength can be secured, and the narrow optical fiber tape is stored in the narrow spiral groove, and the wide optical fiber tape is formed into the wide spiral shape. Store in the groove. The number of optical fiber tapes that can be stored in the wide spiral groove is the same as the conventional one, but the storage density of optical fibers increases as much as the narrow optical fiber tape can be stored in the narrow spiral groove. . Therefore, the density of the optical fiber cable can be increased. When the wide optical fiber tape is an 8-fiber tape and the narrow optical fiber tape is a 4-fiber tape, the spiral groove is a two-step spiral groove. When the wide optical fiber tape is an 8-core tape, a 6-core tape or a 4-core tape, the spiral groove is a spiral groove having three stages. In addition, the spiral groove may be formed in multiple stages so that the lowermost stage is a single-core fiber. Further, when the narrow spiral groove is formed on the bottom of the spiral groove, the side end of the wide optical fiber tape accommodated in the wide spiral groove falls into the spiral groove of the wide ridge and becomes wider. The fiber optic tape may be twisted resulting in reduced transmission efficiency. In order to prevent this reliably, a thin plastic sheet cover plate is laid on the bottom of the wide spiral groove to cover the narrow ridge spiral groove, and a wide optical fiber tape is laminated on top of it to form an optical fiber. Configure a cable slot unit.

[0006]

Example Next, an example will be described with reference to FIGS. 1 and 2. A synthetic resin slot rod 20 manufactured by extrusion molding having a diameter of 14 mm is provided with five spiral two-stage grooves 21 at equal intervals. The spiral two-stage groove 21 has a wide groove 22 having a width B of 2.7 mm and a depth D of 2.5 mm.
And width b groove 2 with a width b of 1.5 mm and a depth d of 2.4 mm
The rib 24 has a wall thickness t ₁ of 2.9 mm at the bottom of the wide groove 22 and the rib 24 has a wall thickness t ₂ of 1.2 mm at the bottom of the wide ridge groove. Since the above wall thickness t ₁ is larger than the wall thickness A of the rib 3 at the spiral bottom portion of the conventional 8-rod tape slot rod,
The strength of the rib is sufficiently secured. Further, the wall thickness t ₂ of the rib 24 at the bottom of the width ridge groove 23 is sufficient to secure the strength of the rib 24. 4 of 250 μmφ wire in the width ridge groove 23
Five core tapes 25 (width 1.1 mm, thickness 0.4 mm) are laminated, the width grooving groove 23 is covered with a lid plate 26 of a polyethylene terephthalate sheet having a plate thickness of 0.1 mm and a width of 2.6 mm, and is placed thereon. Wide groove 2 by stacking five 8-core tapes 27 (width 2.1 mm, thickness 0.4 mm) of 250 μmφ strands
2 and is covered with a sheath 28. This allows a total of 300 cords to be stored in one slot rod and
00 slot units are configured. Since the conventional slot rod shown in FIG. 3 can accommodate 200 cores, a larger number of cores can be accommodated. The slot unit of the above example was subjected to a transmission test with light having a wavelength of 1.55 μm. As a result, the transmission loss is 0.02 dB / km for all cores.
The following was the same as the conventional one. Also radius 40
Wrap the cable around the pulley of 0, apply a pulling force of 100 kg and squeeze the slot unit, then wavelength 1.5
A transmission test was conducted with light of 5 μm. As a result, the transmission loss of all the cores was 0.02 dB / km or less, which was the same as the conventional one.

[0007]

[Effect] The invention which has solved the above-mentioned problems is not yet known. Therefore, it is an effect peculiar to the present invention that the new problem can be solved to solve the problem of the conventional technique, and thereby the density of the optical fiber cable can be dramatically improved. In addition, the density of the optical fiber cable was improved by devising the shape of the groove without changing the thickness of the slot rod.The groove processing method is the same as the conventional slot rod groove processing method. There is no particular difference, and there is no particular disadvantage in terms of processing efficiency and processing cost. Further, by applying the present invention, there is no problem in other aspects such as laying of the optical fiber cable, so that the optical fiber cable can be laid in the same manner as the conventional one. Therefore, the greatest advantage of the present invention is that the density of the optical fiber cable can be dramatically improved without increasing the manufacturing cost of the slot rod and without causing additional problems with the application of the present invention. Is.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is an enlarged view of the groove of FIG.

FIG. 3 is a cross-sectional view of a conventional technique.

[Explanation of symbols]

2 ... Spiral groove 3, 24 ... Rib 10, 20 ... Slot rod 21 ... Spiral two-stage groove 22 ... Wide groove 23 ... Narrow groove 25 ... 4 cores Tape 26 ... Lid plate 27 ... 8-core tape 28 ... Sheath A ... Rib 3 root thickness B ... Wide groove 22 width D ... Wide groove 22 depth b Width of the narrow groove 23 d Depth of the narrow groove t ₁ Rib wall thickness at the bottom of the wide groove 22 t ₂ Rib wall at the bottom of the narrow groove 23 Thickness

Claims (2)

[Claims] 1. A slot rod for an optical fiber cable having a tension member buried in the center and having an optical fiber tape accommodating groove on its outer periphery, wherein the optical fiber accommodating groove has a narrow spiral groove at the bottom of the wide spiral groove. A slot rod for an optical fiber cable having a formed multi-step spiral groove. 2. The slot rod according to claim 1, wherein a plastic plate cover plate is laid on the bottom of the wide spiral groove to cover the narrow spiral groove, and a wide optical fiber tape is laminated thereon. Fiber optic cable slot unit.