JPH06331865A - Groove type optical cable - Google Patents

Abstract

PURPOSE:To provide the groove type optical cable where the degradation in transmission characteristic of tape cores is prevented at the time of housing plural tape cores in a U-shaped groove which has a tape housing space part having a u-shaped cross section. CONSTITUTION:With respect to this optical cable where tape cores 3 are housed in a U-shaped groove 1, the stress for tape cores 3 is uniformized by the curved surface in the groove because tape cores 3 are kept in the twisted state, and the force applied to edge end parts of tape cores 3 is dispersed in the lengthwise direction to effectively reduce the local stress generated between the U-shaped groove 1 and tape cores 3 even at the time of applying a bending force or the like to the cable because tape cores 3 are twisted. Consequently, the stress received on the side of tape cores 3 is minimized, and the degradation in transmission characteristic of tape cores 3 is effectively prevented to obtain the superior optical cable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a groove type optical cable in which a tape core wire is housed in a groove having a tape housing space portion and is twisted around a center tension member when winding the cable. The present invention relates to an optical cable that reduces transmission loss caused by bending during installation.

[0002]

2. Description of the Related Art Conventionally, as an optical cable capable of storing a tape core wire at a high density, a cable having a plurality of grooves formed in a longitudinal direction of a long rod and the tape core wire being housed in the groove Is used. However, this conventional optical cable has a drawback in that when it is bent, the tape core wire receives lateral pressure and transmission loss increases. Therefore, in order to improve this defect, a plurality of tape core wires are housed in a groove having a square cross section (corner groove), and a plurality of the corner grooves are twisted around a central tension member to form a square groove type. Optical cables have been proposed. And, as the tape core wire used in this optical cable, generally, an optical fiber element wire (fiber outer diameter = 125 μm, MF
D = 8.5 to 10.5 μm, λc = 1.1-1.36 μ
m, UV coating diameter = 150 to 220 μm) are arranged side by side in 8 to 16 cores, and these are integrated with a UV curable resin.

[0003]

However, even in the case of the optical cable having the above-mentioned structure, if the tape is wound around the conveying drum after manufacturing or bent at the time of laying, the edge of the tape core wire is attached to the inner wall of the square groove. Since a part of the portion is strongly pressed and acts as lateral pressure on the tape core side, there is a problem that the transmission characteristics of the tape core are deteriorated.

Therefore, the inventors of the present invention have made various studies in order to solve the above-mentioned problems. As a result, the groove for accommodating the tape core wire has a specific structure and the tape core wire has a special state. Therefore, it has been found that the increase of the transmission loss of the tape core wire can be effectively suppressed by the above, and the present invention has been achieved.

[0005]

The feature of the present invention lies in an optical cable in which a tape core wire is housed in a groove having a tape housing space portion having a U-shaped cross section. The core wire is in the groove type optical cable stored in a twisted state.

[0006]

In the optical cable of the present invention, since the groove has a U-shaped cross section and a curved surface in the groove, the tape core wire can be smoothly moved, and the tape core wire is twisted. Therefore, when a force such as bending is applied to the cable, the force applied to the edge portion of the tape core wire is not partially concentrated and is dispersed in the longitudinal direction,
The local stress generated between the groove and the tape core wire is effectively reduced. Therefore, the stress received on the tape core side is minimized.

[0007]

1 shows an embodiment of a groove type optical cable according to the present invention, and FIG. 2 shows a groove used in the optical cable. In these figures, 1 is a groove twisted around the outer periphery of the tension member 2 and has a U-shaped cross-section tape storage space portion (U-shaped groove), and 3 is a plurality of grooves stored in the U-shaped groove 1. The tape core wires 4 of the book are cable sheaths coated on the outside of the U-shaped groove 1.

The U-shaped groove 1 is made of a resin such as polycarbonate, polyetherimide, polybutylene terephthalate, polyimide or polyethylene.
The hardness is not particularly limited, but considering the stress on the tape core wire 3 side, Young's modulus of 30 Kgf / mm ² or less is preferable. When a more specific shape of the U-shaped groove 1 is presented, for example, as shown in FIG. 2, the thickness L ₁ of the side surface and the bottom surface is 0.5 mm, the inner width L ₂ is 5.0 mm, and the inner standing portion L ₂ is 5.0 mm. The depth (L ₃ ) of the installed (vertical) portion is 5.
The U-bottom inner surface radius L ₄ is 5 mm, and the _four U-shaped grooves 1 thus formed are twisted around the outer circumference of the tension member 2 at a pitch of 500 mm, for example.

As the above-mentioned tape core wire 3, for example, an SM type small-diameter optical fiber element wire having an outer diameter of 180 μm (fiber outer diameter = 125 μm, MFD = 8.5) having the same structure as the conventional one.
10.5 μm, λc = 1.1 to 1.36 μm, UV coating diameter = 150 to 220 μm) are arranged in parallel, and 16 cores are UV-coated.
As shown in FIG. 2, the width L ₅ is 3.0 mm and the thickness L ₆ is 0.2 m, using the tape core wire integrated with the cured resin.
In this example, 15 sheets (books) are stored in the groove 1. Then, as the UV curable resin of the tape core wire 3 used here, for example, urethane acrylate resin, epoxy acrylate resin or the like is used.

In addition, at the time of storing, the respective tape core wires 3 are collectively twisted at the same pitch, for example, a pitch of 500 mm to be housed in the groove 1 to form a unit, and four unitized U-shaped grooves 1 are formed. As described above, the optical cable is formed by twisting the outer circumference of the tension member 2 with a pitch of 500 mm.

As described above, in the optical cable of the present invention, since the U-shaped groove 1 has a curved surface in the groove and the tape core wires 3 are twisted at the same pitch, the cable is bent. Even when a local stress is apt to be generated between the U-shaped groove 1 and the tape core wire 3 when a force such as the above is applied, the stress is made uniform by the curved surface of the inner surface of the groove and the tape core wire 3 is formed. Due to the twist of itself, the arrangement of the tape core wires 3 is not aligned in the groove 1 and arranged in a specific direction, but the tape core wires 3 have a spiral shape in the longitudinal direction. Since the force applied from the arrangement direction is easily dispersed in the longitudinal direction, the local stress generated between the U-shaped groove 1 and the tape core wire 3 is effectively reduced. Therefore, the stress received on the side of the tape core wire 3 is minimized, and as a result, the tape core wire 3
It is possible to effectively prevent the deterioration of the transmission characteristics.

By the way, the grooves shown in FIG. 2 are prepared, and 15 tape cores similar to those of the above-mentioned embodiment are collectively twisted in the respective grooves at the same 500 mm pitch. A unit was prepared by housing or storing without twisting, and four of these unitized grooves were twisted around the outer periphery of the tension member at a pitch of 500 mm, and each optical cable was produced as a prototype. Then, when the respective optical cables are wound around a carrier drum having a body diameter of 1 m, the transmission loss of the tape core wire in each groove (measurement light wavelength = 1.55).
.mu.m) was examined and found to be as shown in Table 1. Note that the maximum transmission loss in the table is a value added to this value (0.21 + α, α = cabling because the transmission loss of the tape core wire used here is approximately 0.21 dB / Km. Loss).

[0013]

[Table 1]

From this table 1, the number 1 of the tape core wire in the groove
When 5 sheets are stored together by twisting at the same 500 mm pitch, the transmission loss is small and good transmission characteristics are obtained, whereas when they are stored without twisting, the transmission loss is reduced. It turns out that it is quite large.

In the above embodiment, the U-shaped groove 1
In the case where a plurality of tape core wires 3 are housed therein and four U-shaped grooves 1 are twisted around the outer circumference of the tension member 2, the groove type optical cable of the present invention is not limited to this. The number of glyphs 1 is more than this,
May be small. Further, the number of tape core wires accommodated in the U-shaped groove 1 is not limited to a plurality. Further, a single groove type optical cable in which the tape core wire 3 is simply housed in one U-shaped groove 1 may be used. Further, a high-density optical cable in which the U-shaped groove 1 is twisted in a multi-stage structure on the outer circumference of the tension member 3 may be used. Also,
The cable structure is not limited to the above embodiment, and four U
The gap between the U-shaped grooves 1 may be filled with an interposition, or a winding tape may be wound on the U-shaped groove 1 and then the cable sheath may be covered.

[0016]

As is apparent from the above description, the groove type optical cable according to the present invention is an optical cable in which a tape core wire is housed in a U-shaped groove, and the tape core wire is in a twisted state. Since it is stored in, the curved surface in the groove groove allows the movement of the tape core wire to be smooth, and moreover, the stress on the tape core wire is equalized and even when a force such as bending acts on the cable. Since the force applied to the edge side of the tape core wire is dispersed in the longitudinal direction, the local stress generated between the groove and the tape core wire is effectively reduced. Therefore, the stress applied to the tape core side is minimized, and as a result, an excellent optical cable in which the deterioration of the transmission characteristics of the tape core is effectively prevented can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an embodiment of a groove type optical cable according to the present invention.

FIG. 2 is a vertical sectional view showing a U-shaped groove used in the optical cable of FIG.

[Explanation of symbols]

 1 groove 2 tension member 3 tape core wire 4 cable sheath

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichiro Watanabe 1440 Rokuzaki, Sakura City, Chiba Prefecture Fujikura Co., Ltd.Sakura Factory (72) Inventor Shin Saito 1440, Rokuzaki, Sakura City, Chiba Prefecture Fujikura Sakura Factory, Ltd. ( 72) Inventor Suehiro Miyamoto 1440 Rokuzaki, Sakura City, Chiba Fujikura Co., Ltd. Sakura Factory (72) Inventor Shigeru Tomita 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. An optical cable in which a tape core wire is housed in a groove having a U-shaped cross-sectional tape housing space portion, wherein the tape core wire is housed in a twisted state. Groove type optical cable. 2. The groove type optical cable according to claim 1, wherein the tape core wires are housed by being twisted at the same pitch.