JPS61169806A - Non-metallic layer twisted type optical cable - Google Patents

Abstract

PURPOSE:To improve the ease of handling operation of an optical cable by providing an intimate jelly mixture coated on a plastic tape which is wound on top of fiber cores and intervening cords twisted together into a laminar state via plastic yarn and a plastic sheath which encloses such mixture. CONSTITUTION:The optical fiber cores 1 and the plastic intervening cords 2 are twisted around a tension member 3 consisting of reinforced plastic and a cushion layer 4 consisting of plastic yarn, etc. is provided around the same. The plastic tape or the like is wound 5 on top thereof and thereafter the layer of the intimate jelly mixture 90 is coated thereon and the surface thereof is coated with the sheath 6 consisting of PE or PVC. The mixture 9 is heated to, for example, 70-80 deg.C to the liquid state and is coated on the top winding 5. The layer of the mixture 9 is formed to the thickness enough to absorb the shrinkage in the sectional direction of the sheath 6 in the anticipated using environment.

Description

[Detailed description of the invention] 11th 9μ months! The present invention relates to a non-metallic layer twisted optical cable. More specifically, the present invention relates to a non-metallic layer stranded optical cable that is relatively easy to manufacture and has a structure in which transmission loss due to micro-bent etc. does not increase even if the jacket shrinks in the cross-sectional direction due to a drop in temperature.

BACKGROUND OF THE INVENTION Optical cables with various structures have been developed as optical communication systems become more widely used. Since optical fiber is a dielectric material such as glass or plastic, it has the property of not receiving any electromagnetic induction, and is particularly suitable for the structure of optical cables that should be installed in locations that are connected to power lines or where high noise is expected. There is a demand for a non-metallic optical cable that does not use any metal at all, and it is now in practical use.

Typical structures of non-metallic optical cables that have been conventionally used or devised are those shown in FIGS. 2 to 4.

The non-metallic layer stranded optical cable shown in FIG.
Together with an intervening string 2 made of polyethylene or polyvinyl chloride, they are twisted around a tension member 3 made of reinforced plastic or the like, and a buffer layer 4 made of plastic yarn or the like is provided thereon to protect the optical fiber core 1 from external forces. It has a structure in which an upper wrap 5 of plastic tape or the like is applied, and an outer sheath 6 of polyethylene or polyvinyl chloride is applied to the whole.

Further, in the optical cable shown in FIG. 3, the optical fiber core 1 is surrounded by a tape spacer 7 made of plastic to protect the core wire 1 from external forces, and the tension member 3 made of reinforced plastic or the like is surrounded by a plastic intervening string 2. It is called a tape spacer type optical cable, which has a structure in which the cables are gathered together, covered with a plastic wrapper tape 5, and further covered with a jacket 6 made of polyethylene or polyvinyl chloride.

Furthermore, the optical cable shown in FIG. 4 is called a grooved spacer type optical cable, and has a tension member 3 made of reinforced plastic or the like in its core, and a grooved surface made of polyethylene or the like processed with spiral grooves. With spacer 8
It has a structure in which an optical fiber core 1 is built inside to protect it from external forces, and an upper wrap 5 of plastic and an outer sheath 6 of polyethylene, polyvinyl chloride, or the like are provided.・ However, in the layered optical cable shown in Figure 2, immediately after processing the sheath, such as polyethylene or polyvinyl chloride, the outer sheath shrinks due to residual processing distortion, causing more heat contraction in the cross section or longitudinal direction, compressing the inside. However, there is a problem in that the buffering effect of the buffer layer 4 made of plastic yarn or the like is halved. Furthermore, if the optical cable becomes low temperature below 0℃ during use, the polyethylene or polyvinyl chloride jacket 6
The fiber suddenly shrinks in cross-sectional direction and compresses the buffer layer 4, and the buffer layer 4 made of plastic yarn cannot withstand this compressive force, and an external force is applied to the optical fiber core 1, resulting in an increase in transmission loss. There is a problem with this occurring. In our measurement example, this increase in transmission loss is approximately 0.5 dB at = 20°C.
/ Km ~1. The value was approximately OdB/Km.

Incidentally, by increasing the thickness of the buffer layer 4 made of plastic yarn or the like considerably, it is possible to prevent such an increase in transmission loss, but this not only makes the manufacturing process inefficient, but also increases the outer diameter of the cable. The ease of handling the cable also deteriorates.

Tape spacer type or grooved spacer type optical cables as shown in Figure 3 or Figure 4 can prevent this phenomenon of increased transmission loss at low temperatures, but these optical cables require a tape spacer with a special structure. Because it uses spacers with grooves and grooves, manufacturing is more complicated than the layer-twisted optical cable shown in Figure 2.Furthermore, in the tape spacer type optical cable shown in Figure 3, the spacer itself must be twisted, making it difficult to manufacture a multi-core cable. Moreover, in the grooved spacer type optical cable shown in FIG. 4, it is extremely complicated to manufacture a long grooved spacer made of specially processed plastic.

Therefore, considering the ease of design and manufacturing, multi-core cables, etc., it is easy to manufacture a type that can be applied to a wide range of temperatures and in which optical fiber cores are individually twisted around a tension member as shown in Figure 2. A non-metallic layer stranded optical cable with a unique structure is desired.

In response to such demands, an optical cable as shown in FIG. 5 was developed. This cable is a type of layered optical cable as shown in FIG. There is a structure in which a jelly mixture of polybdenum, which does not solidify at low temperatures, is filled in a liquid state at a high temperature of, for example, 70 to 80°C.

In other words, the purpose is to absorb the shrinkage of the jacket by the jelly mixture 9 and to prevent any load from being applied to the optical fiber core.

In the layered optical cable having such a structure, the increase in transmission loss at -20° C. could be suppressed to approximately Ode/Km. This is because the jelly mixture layer 9 filled between the plastic yarn buffer layer 4 and the polyethylene or polyvinyl chloride jacket 6 prevents heat shrinkage after the jacket is processed. Further, when the liquid jelly mixture filled at high temperature solidifies, a considerable number of closed air bubbles are generated, and these air bubbles are included in the jelly. These bubbles work to absorb the shrinkage force in the cross-sectional direction of the outer sheath when the environment in which the optical cable is placed becomes cold.

However, injecting such a jelly mixture 9 into a cable is a complicated process, resulting in poor manufacturing processability and very poor handling of the optical fiber core.

Problems to be Solved by the Invention The purpose of the present invention is to solve the above-mentioned problems of the prior art.More specifically, the optical cable itself is easy to design and manufacture, the optical cable itself is easy to handle, and can be used over a wide range of temperatures. The purpose of this invention is to provide a non-metallic layer twisted optical cable with stable transmission characteristics.

Means for Solving the Problems In order to achieve the above-mentioned object of the present invention, the present inventors have conducted various experiments and research, and have found that the present invention is easy to design and manufacture.
The present invention has succeeded in providing a non-metallic layer stranded optical cable that is easy to handle and has stable transmission characteristics over a wide range of temperatures.

That is, according to the present invention, a tension member made of a plastic high tensile strength body, an optical fiber core wire and an intervening string made of glass fiber coated with plastic, which are twisted together in layers on the tension member, and these twisted in layers. a plastic tape overwrapping the combined fiber cores and intervening strings via plastic yarn; and a jelly mixture applied onto the plastic tape;
A non-metallic layer stranded optical cable is provided comprising a plastic jacket surrounding the jelly mixture.

The above-mentioned overlapping plastic tape is preferably one that does not allow the jelly mixture to pass through and is air permeable.

When the outer sheath contracts in the cross-sectional direction of the cable due to a decrease in the environmental temperature, the shrinkage of the outer sheath is alleviated by the jelly mixture, and the air bubbles in the jelly mixture permeate through the plastic tape and into the buffer layer. and acts to protect the optical cable core.

The jelly mixture preferably used in accordance with the present invention needs to be in a liquid state (sol) at room temperature or higher, to be jelly-like (gel) at room temperature, and not to solidify even at the lowest temperature at which the cable is laid. Furthermore, it is preferred that the jelly mixture contains about 20% air bubbles.

Typical jelly mixtures that satisfy the above conditions are bolybdenum jelly and petroleum jelly.

The buffer preferably used in the present invention is a polypropylene plastic yarn.

However, jelly blends and plastic yarn buffers themselves are well known in the art and will not be described in further detail.

Rule J As described above, the present invention is a non-metallic layer twisted optical cable characterized by providing a layer of a jelly mixture between the plastic tape and the plastic jacket. By absorbing heat shrinkage in the cross-sectional direction of polyethylene or polyvinyl chloride immediately after processing the outer jacket, and further preventing a decrease in the buffering effect of the plastic yarn, the transmission characteristics are stabilized over a wide temperature range, including low temperatures. Furthermore, the buffer layer of plastic yarn can prevent the jelly mixture from permeating the optical fiber to some extent, and the optical fiber core hardly comes into contact with the jelly, improving the handling efficiency of the optical cable.

Further, since the jelly mixture layer can be processed simultaneously with the processing of the polyethylene or polyvinyl chloride jacket, the manufacturing processability is also very good.

Embodiment An embodiment of the optical cable of the present invention will be described with reference to FIG.

An optical fiber core 1 and a plastic intervening string 2 are twisted around a tension member 3 made of reinforced plastic or the like, and a buffer layer 4 made of plastic yarn or the like is provided. Furthermore, after applying an upper wrap 5 of plastic tape etc. on these,
A layer of Die IJ-admixture 9 is applied and covered with an overcoat 6 such as polyethylene or polyvinyl chloride.

The jelly mixture 9 is heated to a temperature at which it becomes liquid, for example 70 to 80° C., and then applied onto the top roll 5.

The thickness of the jelly mixture layer 9 is large enough to absorb the cross-sectional shrinkage of the jacket 6 under the envisaged use environment. This is designed and calculated according to the overall diameter of the cable and the material and thickness of the jacket 6.

Effects of the Invention By simply providing a layer of jelly mixture with a thickness of, for example, 0.3 to 0.5 mm between a plastic yarn buffer layer such as polypropylene and a polyethylene jacket, loss fluctuations can be reduced over a wide range of temperatures from -30°C to +60°C. It is stabilized at approximately dB/Km, and even if a jelly mixture layer is provided, the outer diameter increases only slightly, and the optical fiber core wire does not leak into the jelly mixture, making the optical fiber core wire very easy to handle. good.

Furthermore, with this structure, even if a pinhole or small external injury occurs in the outer cover, water can be prevented from running in from the outside.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a non-metallic layer stranded optical cable which is an embodiment of the present invention. 2 to 5 are sectional views of conventional optical cables, FIG. 2 is a sectional view of a non-metallic layer stranded optical cable, FIG. 3 is a sectional view of a tape spacer type optical cable, and FIG. 4 is a sectional view of a tape spacer type optical cable.
The figure is a cross-sectional view of a grooved spacer type optical cable, and FIG. 5 is a cross-sectional view of a non-metallic layer twisted type optical cable having a jelly mixture layer. (Main reference numbers) 1. Optical fiber line, 2. Intervening string 3. Tension member, 4. Buffer layer, 5. Upper roll, 6. Outer cover, 7. Tape spacer, 8. Grooved spacer, 9...
jelly mixture

Claims (2)

[Claims] (1) A tension member made of a high tensile strength plastic body, an optical fiber core made of glass fiber coated with plastic and an intervening string, which are twisted together in layers on the tension member, and a fiber core made of these twisted layers. A non-woven fabric characterized by comprising: a plastic tape on which wires and intervening strings are wrapped via plastic yarn; a jelly mixture applied onto the plastic tape; and a plastic jacket surrounding the jelly mixture. Metallic layer twisted optical cable. (2) The non-metallic layer stranded optical cable according to claim 1, wherein the plastic tape is gas permeable.