JPH06331866A - 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 section. CONSTITUTION:Since tape cores 3 are housed in a U-shaped groove 1 in the twisted state and the length of tape cores 3 is made to be -0.1 to 0.1% for the U-shaped groove 1, the force applied to edge end parts of tape cores 3 is uniformly dispersed along the curved surface of the bottom surface of the U-shaped groove 1 even if the cable is bent or is used in environment having a large temperature difference, and the cable can satisfactorily cope with even various temperature changes or the like after laying, and therefore, the local stress generated between the U-shaped groove 1 and tape cores 3 is effectively reduced. 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. Furthermore, the installed optical cable has a problem that the transmission characteristics are deteriorated depending on various conditions such as the installation environment, temperature changes depending on the seasons, and installation conditions.

Therefore, the inventors of the present invention have made various studies in order to solve the above problems. As a result, the tape core wire accommodated in the groove is made into a special state, and the tape core wire accommodated therein. The present invention has been found out that the increase of the transmission loss of the tape core wire can be effectively suppressed by setting the length of the tape to a specific length with respect to the groove.

[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 accommodated in a twisted state, and the length of the tape core wire is −
It is in a groove type optical cable with a length of 0.1 to 0.1%.

[0006]

In the optical cable of the present invention, since the groove has a U-shaped cross section and has a curved surface in the groove, the movement of the tape core wire can be made smooth 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 dispersed in the longitudinal direction without being partially concentrated, so that it occurs between the groove and the tape core wire. Local stress is effectively reduced. Furthermore, since the length of the accommodated tape core wire is set to −0.1 to 0.1% with respect to the groove,
The local stress applied to the tape core wire can be relieved against various temperature changes after installation. Therefore, under various usage conditions and usage conditions, local stress on the tape core side is minimized, and good transmission characteristics can be obtained.

[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, for example, polyetherimide, polycarbonate, polyamide, PBT,
It is made of resin such as polyethylene, and its hardness is not particularly limited. 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 height is 5.0 mm. The depth (L ₃ ) of the installed (vertical) portion is 5.5 mm and the U-bottom inner surface radius L ₄ is 2.5 mm. _Four U-shaped grooves 1 thus formed are provided on the outer circumference of the tension member 2, for example, at a pitch. It is twisted at 500 mm.

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.
m, and in this example, 15 in the U-shaped groove 1
Stores a sheet (book). 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.

Further, 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 U-shaped groove 1, and as shown in FIG. The length L _{7 of} 3 is made −0.1 to 0.1% longer than the length L _{8 of} the U-shaped groove 1 to form a unit, and the four U-shaped grooves 1 which are unitized are described above. As described above, the tension member 2 is twisted around the outer periphery at a pitch of 500 mm to form an optical cable.

Here, the length L ₇ of the tape core wire 3 is
-0.1 to 0.1 for the length L ₈ of the U-shaped groove 1
The reason for increasing the length is due to the following reasons. In other words, in the case of an optical cable, it is not only exposed to a low temperature of about -40 ° C to a high temperature of about 70 ° C due to the temperature change due to the installation environment and the four seasons, but also when it is used by being incorporated into an overhead cable. It may also be used under special circumstances where tensile stress is applied to the. In such a situation, the relative length between the tape core wire 3 and the U-shaped groove 1 slightly changes due to a difference in expansion coefficient due to temperature change, tensile stress, etc. There is a problem that stress is applied and transmission loss increases. In such a case, the length L ₇ of the tape core wire 3 is set to -0.1 to 0..80 with respect to the length L ₈ of the U-shaped groove 1. This is because these problems can be effectively prevented by appropriately adjusting in the range of 1% in consideration of the use environment and use state.

For example, when considering the temperature environment under installation, since the expansion and contraction of the U-shaped groove 1 made of only resin is relatively large with respect to the tape core wire 3, for example, set as follows. Is desirable. When installed in an environment where there is a large inclination to the low temperature side and there are many opportunities, it is preferable to make the tape core wire 3 longer than the length L ₈ of the U-shaped groove 1 by 0.1%, and a large inclination to the high temperature side. When laying in an environment where there are many opportunities, use the tape core wire 3 for the length L of the U-shaped groove 1.
It is preferable to make it shorter than ₈ within the range of -0.1%,
When laying in an environment in which the temperature does not greatly incline on the low temperature side or the high temperature side, it is preferable that the tape core wire 3 has a length substantially equal to the length L ₈ of the U-shaped groove 1.

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. When a force such as the above acts, even if rubbing or twisting occurs between the U-shaped groove 1 and the tape core wire 3, a large friction is alleviated by the curved surface inside the groove, and the tape core wire 3 Due to the twisting of itself, the arrangement of the respective tape core wires 3 is not aligned in the U-shaped groove 1 in a constant state, but becomes a spiral shape in the longitudinal direction. Since the force applied from the edge portion is easily dispersed in the longitudinal direction, the stress generated between the U-shaped groove 1 and the tape core wire 3 is effectively reduced. Furthermore, since the length L ₇ of the tape core wire 3 is set in a specific range with respect to the U-shaped groove 1, it is possible to favorably cope with various laying conditions. Therefore, the stress received on the tape core wire 3 side is minimized, and as a result, it is possible to effectively prevent deterioration of the transmission characteristics of the tape core wire 3.

Incidentally, U-shaped grooves as shown in FIG. 2 are prepared, and 15 tape cores similar to those of the above embodiment are collectively provided in each of these grooves with the same 500 mm.
A unit was prepared in which the optical fiber was twisted at a pitch and stored or not twisted, and four of these unitized grooves were twisted around a tension member at a pitch of 500 mm to produce respective optical cables. Then, when the respective optical cables are wound around a conveying drum having a body diameter of 1 m, the transmission loss of the tape core wire in each groove (measurement light wavelength = 1.5).
5 μm), the results are shown in Table 1. In addition,
As for the maximum transmission loss in the table, since the transmission loss of the tape core wire itself used here is approximately 0.21 dB / Km, the value added to this value (0.21 + α, α = loss due to cable formation) ).

Further, similarly to the above, the grooves as shown in FIG. 2 are prepared, and 15 tape cores similar to those of the above embodiment are collectively provided in each of these grooves with the same 500 mm.
Twist it at a pitch and store it. At that time, the length of the tape core wire to the groove is 6 types (-0.2%, -0.1%,-
0.05%, 0%, 0.1%, 0.2%) to create a unit, and twist these four unitized grooves around the tension member at a pitch of 500 mm. Was prototyped. Then, when the transmission loss (wavelength of measured light = 1.55 μm) of the tape core wire in each groove of each optical cable was examined under the following temperature conditions, it was as shown in Table 2. The maximum transmission loss in the table is also shown in the same manner as in Table 1, and
The temperature condition of each optical cable was set by placing a trial cable of about 3 km wound on a drum or the like in a temperature-controllable test chamber. Environmental temperature +70 when tape core length is -0.2%
℃ Environmental temperature +70 when tape core length is -0.1%
℃ Environmental temperature +7 when tape core length is -0.05%
0 ℃ When the core length of tape is 0%, the ambient temperature is +70 to -4
0 ℃ Environmental temperature -40 ℃ when the length of the tape core wire is 0.1% Environmental temperature -40 ℃ when the length of the tape core wire is 0.2%

[0016]

[Table 1]

[0017]

[Table 2]

From Table 1 above, 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. Also, from Table 2 above,
15 tape cores are grouped together in a groove
While storing by twisting at a mm pitch and making the length longer by 0.1% to 0.1% than the groove, transmission loss is small and good transmission characteristics are obtained.
It can be seen that the transmission loss is considerably large when the length of the tape core wire is out of the above range.

In the above embodiment, the U-shaped groove 1
In the case where a plurality of tape core wires 3 are housed inside 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, and the groove type optical cable is not limited to this. 1 may be more or less than this. 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, it may be a high density type optical cable in which the U-shaped groove 1 is twisted in a multi-stage structure on the outer circumference of the tension member 2. Also, the cable structure is not limited to the above-mentioned embodiment, and the gap between the four U-shaped grooves 1 is filled with an interposition, or the winding tape is wound on the U-shaped grooves 1, and then the cable sheath is inserted. It may be coated.

[0020]

As is apparent from the above description, according to the groove type optical cable of the present invention, the tape core wire is stored in a twisted state in the U-shaped groove having a curved bottom surface. Even when the cable is bent, such as when it is wound around a drum, the stress at the edge of the tape core is evenly distributed along the curved surface of the groove, and the stress is localized at the edge of the tape core. Good transmission characteristics can be obtained because no significant stress concentration occurs. In addition to the fact that the tape core wire is stored in a twisted state, the length of the tape core wire is −0.1 to 0.
Since the length is 1%, it can cope well with stress caused by a difference in linear expansion coefficient when used in an environment with a large temperature difference, so that it is locally generated between the groove and the tape core wire. Effective stress is effectively reduced.
Therefore, in various usage conditions and usage environments, the stress received on 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.

3 is a partial schematic side view showing a length of a tape core wire with respect to 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 section and a tape housing space portion, wherein the tape core wire is housed in a twisted state, and the tape core wire is housed. A groove type optical cable characterized in that the length of the wire is set to -0.1 to 0.1% with respect to the groove. 2. The groove type optical cable according to claim 1, wherein the tape core wires housed in the groove are twisted at the same pitch.