JPH0538613U - Optical cable - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] When the spacer type multi-fiber optical cable is bent,
(EN) Provided is an optical cable having a small transmission loss by reducing the deformation of the spacer and minimizing the stress applied to the optical fiber core wire in the fiber storage chamber. [Structure] A tensile strength member 6 having a Young's modulus higher than that of the material forming the spacer is embedded at the boundary between the bottom portion 8 and the side wall portion 7 of the spacer having the U-shaped storage chamber 9 for accommodating the tape-shaped optical fiber. An optical cable is formed by accommodating the tape-shaped optical fiber in this spacer and arranging the tape-shaped optical fiber in an annular shape so as to surround the strength member.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to an improvement of a spacer type multi-core optical cable.

[0002]

[Prior Art]

 As a multi-core optical cable that is currently put into practical use as an optical fiber cable for subscribers, there is a structure in which a tape-shaped optical fiber is housed in a groove formed in a spiral shape on the outer circumference of a linear body (Shokai 58-188613). .. In order to obtain a cable of higher density, it is possible to realize a multi-layer structure such as an outer layer grooved linear body 10 'on the outer periphery of the inner layer grooved linear body 10 shown in FIG. However, in this cable, it is difficult to take out the optical fiber in the inner layer without damaging the optical fiber in the outer layer in the branching work after taking out the optical fiber from the middle part of the cable after installation.

On the other hand, as described in Japanese Patent Application Laid-Open No. 55-45087, the post-branching property and the discrimination can be obtained by stacking plastic spacers extruded in a U-shaped cross section in multiple layers. The cable can be formed without damaging the property.

[0004]

[Problems to be solved by the device]

 However, when the cable with the above structure is bent, when the bottom of the U-shaped spacer is perpendicular to the bending direction, the side wall falls to the inside of the optical fiber storage chamber and narrows the opening width. There was a problem of increasing transmission loss.

[0005]

[Means for Solving the Problems]

 The present invention provides a structure for solving the above problems, and as shown in FIGS. 1 to 10, a tape shape is formed in a spacer 3 having a U-shaped storage chamber 9 formed of a bottom portion 8 and a side wall portion 7. In an optical cable in which a cable unit having an optical fiber 2 inserted therein is twisted in layers around the cable strength member 1, a Young's modulus higher than that of the material forming the spacer at the boundary between the bottom portion 8 and the side wall portion 7 or at the bottom portion 8 of the spacer. An optical cable having a tensile strength member 6 buried therein.

Here, the cable strength member 1 is formed by twisting FRP, steel wire and the like. The tape-shaped optical fiber 2 is formed by arranging the optical fibers in parallel at regular intervals and coating them with plastic. The spacer 3 is formed by extruding a thermoplastic resin in a U shape so that the inner walls of the side walls are substantially parallel. As the tensile strength member 6 built in the spacer, FRP or a metal linear member is used. The outer shape of the spacer 3 may be trapezoidal as shown in FIGS. 2 to 5 or circular as shown in FIGS. 7 to 10, and is not limited. When the spacer 3 is twisted around the cable strength member 1, the opening of the spacer may be radial from the center of the cable cross section (Fig. 1) or may change depending on the position in the cable length direction (Fig. 6). . The sheath 5 plastically covers and protects the cable.

[0007]

[Action]

 The case where the bottom of the U-shaped spacer is perpendicular to the bending direction will be described with reference to FIG. Due to symmetry, the bending center of the U-shaped plastic spacer is located above the center of the bottom. Therefore, the side wall portion outside the bending center tries to approach the bending center in order to eliminate the difference in length, and the side wall portion collapses inward. Similarly, the side wall inside the bending center also tries to fall inside the groove. In this way, the groove width of the U-shaped plastic spacer is narrowed, and lateral pressure is applied to the optical fiber core wire, causing an increase in loss.

In more detail, the bending moment is generated at the boundary between the bottom portion and the side wall portion to cancel the length by bending, and the side wall portion collapses. In order to suppress this effect, in order to suppress the deformation caused by the moment when the side wall falls down, a part having a higher Young's modulus than the side wall is provided at the bottom or at the boundary between the bottom and the side wall. Specifically, it is effective to insert a strength member. Actually, in order to reduce the bending moment, it is conceivable to keep the height of the side wall part low or increase the allowable bending diameter of the cable, but this limits the cable design and usage environment. Not preferable. Therefore, as in the present invention, it is considered that the best means is to suppress the collapse of the side wall portion by providing the bottom portion or the boundary portion with a portion having a high Young's modulus.

[0009]

【Example】

 The U-shaped plastic spacer shown in FIG. 2 was produced by feeding out two glass FRPs having a diameter of 0.5 mm and extruding high-density polyethylene (HDPE) around them. In addition, the same shape without tensile strength was also manufactured for comparison. The dimensions of the groove were a groove width of 3.8 mm and a groove depth of 3.4 mm, and the wall thickness of the side wall portion / bottom portion was about 0.7 mm. One spacer accommodates five tape fibers consisting of five-core optical fibers, and the cable shown in Fig. 1 was prototyped.

As a result, the transmission loss was not deteriorated by using any spacer when the wire was drawn, but when wound on a drum having a body diameter of 600 mm, the communication wavelength was 1. At 55 μm, deterioration of the transmission characteristics of about 0.1 dB / km was recognized. On the other hand, it was confirmed that the one containing the tensile strength body could be suppressed to deterioration of 0.02 dB / km or less even in a drum wound state.

[0011]

[Effect of the device]

 As described above, the present invention has few deformations of the storage chamber of the spacer even when the cable is bent, so that stable transmission characteristics can be obtained, and the multi-core structure is excellent in the rear branching property and the unit distinguishability. An optical cable can be realized.

[Brief description of drawings]

FIG. 1 shows an example of a cross-sectional view of an optical cable structure according to the present invention.

FIG. 2 shows an example of a cross-sectional view of a spacer applied to FIG.

FIG. 3 is the same as FIG.

FIG. 3 is the same as FIG.

5 is the same as FIG.

FIG. 6 shows a cross-sectional view of another optical cable structure according to the present invention.

7 shows an example of a cross-sectional view of a spacer applied to FIG.

8 is the same as FIG. 7.

9 is the same as FIG. 7.

10 is the same as FIG. 7.

FIG. 11 shows a cross-sectional view of a conventional optical cable structure.

FIG. 12 is an explanatory diagram showing a deformation mechanism of a spacer due to cable bending.

[Explanation of symbols]

 1: Cable strength member 2: Tape-shaped optical fiber 3, 3-1: Spacer 4, 4-1: Press winding 5: Sheath 6, 6 ': Strength member 7, 7-1: Side wall part 8, 8-1: Bottom 9: Storage room 10, 10 ': Linear body with groove

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[Procedure amendment]

[Submission date] October 23, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief explanation of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is an example of a cross-sectional view of an optical cable according to the present invention.

2 is an example of a cross-sectional view of a spacer applied to the optical cable shown in FIG. 1 in the present invention.

FIG. 3 is another example of a cross-sectional view of a spacer applied to the optical cable shown in FIG. 1 in the present invention.

FIG. 4 is another example of a cross-sectional view of a spacer applied to the optical cable shown in FIG. 1 in the present invention.

FIG. 5 is another example of a cross-sectional view of a spacer applied to the optical cable shown in FIG. 1 in the present invention.

FIG. 6 is a cross-sectional view of another optical cable according to the present invention.

FIG. 7 is an example of a cross-sectional view of a spacer applied to the optical cable shown in FIG. 6 in the present invention.

8 is another example of a cross-sectional view of a spacer applied to the optical cable shown in FIG. 6 in the present invention.

9 is another example of a cross-sectional view of a spacer applied to the optical cable shown in FIG. 6 in the present invention.

10 is another example of a cross-sectional view of a spacer applied to the optical cable shown in FIG. 6 in the present invention.

FIG. 11 is a cross-sectional view of a conventional optical cable.

FIG. 12 is an explanatory diagram showing the deformation mechanism of the spacer due to cable bending.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Tanaka 1 Taya-cho, Sakae-ku, Yokohama, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Shigeru Tomita 1-6 Uchiyuki-cho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (1)

[Scope of utility model registration request] 1. An optical cable in which a cable unit, in which a tape-shaped optical fiber is inserted into a spacer having a U-shaped storage chamber formed of a bottom portion and a side wall portion, is twisted in layers around a cable tensile member, wherein the spacer is a spacer. An optical cable characterized in that a tensile strength member having a Young's modulus higher than that of the material forming the spacer is embedded at the boundary between the bottom and the side wall or at the bottom.