JPH055524Y2 - - Google Patents

Description

[Detailed explanation of the idea] (Industrial application field) FIELD OF THE INVENTION The present invention relates to fiber optic cables.

(Prior art) Optical fibers are prone to scratches from contact with the outside and are inconvenient to handle when left as they are, so they are coated with primary and secondary coatings to protect them and to withstand lateral pressure. A structure in which a buffer layer is provided between the primary coating and the secondary coating is widely used.

When an optical fiber is subjected to lateral pressure, it undergoes a minute bend called a microbend, which causes light to escape from the fiber and increase loss. Therefore, it is necessary to design the cable structure so that lateral pressure is not applied to the optical fiber, and to appropriately select fiber parameters (core diameter, refractive index difference, etc.) so that loss does not increase even if lateral pressure is applied.

Furthermore, in order to prevent the fiber from breaking during cable installation, it is necessary to suppress the elongation of the cable as much as possible and keep the tension applied to the internal fiber to a minimum, so a tensile strength member made of metal wire or the like is provided.

In addition, the optical fiber structure, fiber assembly method, and cable structure are determined by considering how to supply power to the repeater, how to maintain and monitor the transmission line, etc.

In this way, the cable structure is designed to minimize the lateral pressure and tension that act on the internal optical fiber core, but even a small tension that is applied over a long period of time can cause the fiber to break due to static fatigue. Therefore, reliability against fiber breakage due to tension is especially important. Furthermore, in the case of submarine cables, excessive tension is applied during cable installation and salvage compared to land cables, so their reliability must be guaranteed under even more severe conditions.

Therefore, JP-A-56-146105 (conventional example 1), JP-A-55-156314 (conventional example 2), JP-A-57-44108 (conventional example 3), 54−
Techniques such as Japanese Patent Application Laid-Open No. 170849 (Conventional Example 4) and Japanese Patent Application Laid-Open No. 52-26840 (Conventional Example 5) have been proposed.

(Problem to be solved by the invention) In conventional examples 3 and 4, when the tape units are laminated, their cross-sectional shape is rectangular or has stepped irregularities on the outer periphery, so when the cable sheathing material is coated, the cable sheathing A gap is created between the inner surface of the material and the outer surface of the tape unit, which poses a problem in terms of lateral pressure resistance.

In conventional examples 1 and 5, assembly of the tape unit (spacer) was troublesome and the structure was complicated.

In addition, in the conventional example 2, the tape unit (spacer) is in the segment shape, so it is troublesome to assemble.

Therefore, the present invention creates a cylindrical laminated structure by overlapping a first elongated main body having a substantially trapezoidal shape and a second elongated main body having a substantially crescent shape, so that there is no gap when covering the cable covering material. It is an object of the present invention to provide an optical fiber cable that is hard to generate, has excellent lateral pressure resistance, and has a stable cable shape.

(Means for Solving the Problems) In the present invention, a spacer 1 for holding an optical fiber 8 is provided in a hollow cable sheathing member 4 having a circular or similar cross-sectional shape, and the spacer 1 includes a flat portion 5B, 6B, a curved optical fiber holding groove 7 is formed in the flat portions 5B, 6B of the elongated main bodies 5, 6 in the longitudinal direction of the elongated main bodies, and 5, 6 flat part 5
In order to achieve the above-mentioned purpose in an optical fiber cable in which B and 6B are mutually polymerized and laminated,
The following technical measures have been taken:

That is, in the present invention, the elongated main bodies 5 and 6 are
A first elongated main body 5 having a substantially trapezoidal cross section and having arcuate surface portions 5A on both side edges and flat portions 5B on the upper and lower surfaces, and an arcuate surface portion 6A having the same curvature as the arcuate surface portion 5A of the first elongated main body 5. and a second elongated main body 6 having a substantially crescent-shaped cross section and having a flat part 6B on one surface, and a plurality of the first elongated main bodies 5 are stacked with the flat parts 5B mutually and placed in the overlapping part. While holding the optical fiber 8, the flat portion 6B of the second elongated body 6 is attached to the flat portion 5B of the pair of first elongated bodies 5 in the outermost layer.
It is characterized in that the optical fibers 8 are held in the overlapping portion by overlapping them to form a laminated structure having a cylindrical outer circumferential shape.

(Function) Since the optical fiber 8 is accommodated in the curved holding groove 7 formed in the spacer 1, even if the cable K expands or contracts due to weather changes, aging changes, wind force, etc., the optical fiber 8 will not bend. There is no expansion or contraction, and fiber breakage is prevented.

The spacer 1 in which the first elongated main body 5 and the second elongated main body 6 are laminated has a cylindrical outer circumferential shape simply by laminating them, and when covered with the cable covering material 4,
It has no gaps and can fully withstand lateral pressure, and the cable shape is stable.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an optical fiber cable K according to an embodiment of the present invention, and the cable K includes a spacer 1 having a cross section similar to a circle, such as a cylindrical or elliptical shape, and a spacer 1 that covers the spacer 1. It consists of a cable covering material 4 such as a heat insulating layer 2 and a covering layer 3.

The spacer 1 is formed by laminating a first elongate body 5 and a second elongate body 6 made of a light alloy material, steel, hard resin, or the like.

The first elongated body 5 has a substantially trapezoidal cross section with arcuate surface portions 5A on both side edges and flat portions 5B on the upper and lower surfaces, and as shown in FIGS. 2 and 3, the flat portions 5B
A holding groove 7 having a curved shape in the longitudinal direction is formed in the holding groove 7, and an optical fiber 8 is accommodated in the holding groove 7.

Note that the holding grooves 7 are formed on both the upper and lower surfaces or only on one surface.

The second elongated main body 6 has an approximately three-month shape in cross section, having an arcuate surface portion 6A having the same curvature as the arcuate surface portion 5A, and a flat portion 6B on one side, and the flat portion 6B has a retaining groove 7 similar to that described above. .

The above-mentioned first elongated body 5 is made by overlapping the flat portions 5A of the plurality of pieces with each other and inserting the optical fiber 8 into the overlapping portion.
The flat part 6B of the second elongated body 6 is attached to the pair of flat parts 5B in the outermost layer of the first elongated body 5.
A spacer 1 having a cylindrical cross section is formed by overlapping the spacer 1, and the cable sheathing material 4 is coated on this spacer 1. There is no gap between the outer periphery of the spacer 1 and the cable sheathing material 4, and the lateral pressure resistance is improved. It is secured.

(Effects of the invention) The present invention is as described above, and by forming the holding groove for accommodating the optical fiber in a curved shape in the longitudinal direction, the length of the optical fiber is made longer than the spacer, and the optical fiber can be expanded by stretching or the like. In addition to the basic effect of being able to prevent breakage, the following specific effects are achieved.

That is, the elongated bodies 5 and 6 forming the spacer
The first elongated main body 5 has a substantially trapezoidal cross section and has arcuate surface portions 5A on both side edges and flat portions 5B on the upper and lower surfaces.
and a second elongated main body 6 having an approximately crescent-shaped cross section and having an arcuate surface portion 6A having the same curvature as the arcuate surface portion 5A of the first elongated main body 5 and a flat portion 6B on one surface, A plurality of main bodies 5 are stacked with their plane parts 5B mutually and the optical fiber 8 is held in the overlapped part, and the second elongate body 5 is attached to the plane part 5B of the pair of first elongated bodies 5 in the outermost layer. Flat part 6B of main body 6
The optical fiber 8 is held in the overlapped portion to form a laminated structure with a cylindrical outer circumferential shape, so there is no gap between the outer circumferential surface of the spacer and the inner circumferential surface of the cable sheathing material. This allows the cable shape to be stabilized, and since the optical fiber 8 is always located inside, the lateral pressure resistance can be greatly improved.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a perspective view, and FIGS. 2 and 3 are sectional views showing two examples. DESCRIPTION OF SYMBOLS 1... Spacer, 5... First elongated body, 6... Second elongated body, 7... Holding groove, 8... Optical fiber, K
...Fiber optic cable.

Claims (1)

[Claims for Utility Model Registration] A spacer 1 for holding an optical fiber 8 is provided in a hollow cable sheathing member 4 having a circular or similar cross-sectional shape.
A curved optical fiber holding groove 7 is formed in the flat portions 5B, 6B of the elongated main bodies 5, 6 in the longitudinal direction of the main body. Flat parts 5B, 6B of the shaku bodies 5, 6
In the optical fiber cable, the elongated main bodies 5 and 6 have arcuate surface portions 5 on both side edges.
A first elongated main body 5 having a substantially trapezoidal cross section and having flat portions 5B on two upper and lower surfaces, an arcuate surface portion 6A having the same curvature as the arcuate surface portion 5A of the first elongated main body 5, and a flat portion 6B on one surface. a second elongated main body 6 having a substantially crescent-shaped cross section, and a plurality of the first elongated main bodies 5 are overlapped with their flat parts 5B, and an optical fiber 8 is held in the overlapped part. At the same time, the flat part 6B of the second elongated main body 6 is superimposed on the flat part 5B of the paired first elongated main body 5 in the outermost layer, and the optical fiber 8 is held in the overlapped part, so that the outer peripheral shape is circular. An optical fiber cable characterized by having a columnar laminated structure.