JPH0355930Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to the improvement of optical fiber cables with high mechanical strength and multi-core fibers, and is particularly suitable for application to areas such as aerial wiring systems. This type of cable has the structure shown in Figures 1 and 2, that is, the outer diameter is 0.3 as shown in Figure 3.
Three so-called tape-type optical units 3 are laminated with a large number of optical fibers (coated with silicone, etc.) 1 of about mm size, for example, five fibers arranged in a row and coated with a coating 2 of nylon or the like. A structure has been proposed in which a unit is formed with an aluminum laminate sheath 4 on the outer periphery, and a large number of these units are twisted around a central tensile strength member 5 and covered with an outer sheath 6. The present invention was proposed in order to realize smaller diameter, lower cost, and higher strength than the conventional structure described above. An embodiment of the present invention is shown in FIGS. 4 and 5. FIG. 4 shows the above-mentioned tape-type optical unit 3 in the groove 7 of a spacer 8, which is formed by extruding polyethylene around the central tensile strength member 5 made of FRP and has a spiral groove 7 continuous in the length direction of the outer periphery. This is a structure in which three layers are stacked in the radial direction and the number of grooves is four. Figure 5 shows a case where the number of grooves is six. Table 1 shows a comparison of the cable outer diameters between the present invention and the conventional structure when the number of optical fibers accommodated is the same. That is, in the specific example of the present invention, as shown in Table 1, the groove dimensions are 2 x 2 mm.
Three tape-shaped optical units (3 subunits) with dimensions of 0.5 x 1.5 mm are stacked here. Therefore, the total dimensions of the three laminated sheets are
The size is 1.5 x 1.5 mm, and the diagonal dimension is 2 mm or more (approximately 2.1 mm). With the structure of the present invention, the outer diameter of the cable is less than 80% compared to the conventional structure, which means that the cable diameter is smaller.Conversely, if the outer diameter of the cable is the same, it is possible to increase the number of cores, thus reducing the cable diameter. It also has the advantage of being cost effective.

[Table] Regarding the lateral pressure resistance of the cable, in this invention the optical fiber is housed in the groove of the spacer, so the transmission characteristics of the optical fiber are stably maintained even under a load more than twice that of the conventional structure. can. When comparing economical efficiency, it can take advantage of the advantage of reducing man-hours compared to conventional structures. Furthermore, in the cable structure of the present invention, the arrangement of optical fibers can be maintained regularly with respect to the central axis of the cable. That is, as shown in FIG. 4, a plurality of tape-shaped optical units are stacked in the radial direction in such a manner that they can directly contact each other within the spiral groove 7, and the width and depth of the spiral groove 7 are as shown in Table 1. As shown in the specific example, when the optical fiber cable is bent during its installation, a plurality of tape-shaped optical units housed in a stack are attached to the outer sheath 6 on the bottom, side wall, and top surface of the spiral groove 7. The size is such that they do not come into contact with each other, thereby preventing them from being replaced with each other and disrupting the arrangement. In other words, in the example in Table 1, the diagonal dimension of the three stacked units (1.5 x 1.5 mm dimensions is 2 mm or more (approximately 2.1 mm)), and therefore the width and depth dimensions of the spiral groove 7 are each 2 mm. , the unit will not twitch back and forth.As a result, the transmission characteristics of the optical fiber will remain stable even under the history of bending during cable installation and harsh environmental changes after installation, and will remain distortion-free. The optical fiber is housed in the groove of the plastic spacer that is integrated with the central tensile strength member, which has a small coefficient of thermal expansion even when the temperature changes. This reduces bending and stabilizes the transmission characteristics.A waterproofing compound is added to the groove of the spacer.
For example, a non-metallic watertight optical cable can be realized by filling it with petroleum-based jewelry or the like.

[Brief explanation of drawings]

1 to 3 are cross-sectional views of conventional optical fiber cables, and FIGS. 4 and 5 are cross-sectional views of optical fiber cables of the present invention. 1... optical fiber, 3... tape type optical unit, 5... Tensile strength body, 7... Spiral groove, 8... Spacer.

Claims (1)

[Claims for Utility Model Registration] Consisting of a plurality of tape-shaped optical units of approximately the same size, which are made by arranging a plurality of optical fibers in a row and covering them all at once, and then embedding the optical fibers integrally in the covering material. The optical fiber cable includes a spacer fixed to a central tensile strength member and having a spiral groove of a predetermined width and depth in the length direction of the outer periphery, and a jacket provided on the outer periphery, and the tape-shaped optical unit are laminated in the radial direction in a state in which they can be in direct contact with each other without being glued together in the helical groove, and the width and depth of the helical groove are such that the laminated fibers are formed when the optical fiber cable is bent during installation. The plurality of tape-shaped optical units housed in
An optical fiber cable having a size that abuts against the bottom surface, side wall, and outer sheath on the top surface of the helical groove, thereby preventing them from being replaced with each other and causing disorder in the arrangement.