JPS6113208A - Optical cable - Google Patents

Abstract

PURPOSE:To prevent the application of the tension and compressive force which are of problem between optical fibers when an optical cable is subjected to plane bending by coating movably axially metallic tubes contg. the optical fibers with a sheath. CONSTITUTION:The metallic tubes 6 are axially movably housed in the sheath 4 and further the optical fibers 5 are brought into contain in the tubes 6. A lubricating oil or the like is filled in the space 7 between the sheath 4 and the tubes 6 to increase a slipping effect. Half-split pipes may be used in place of the tubes 6 and the sheath may be made into a pipe shape by winding a metallic tape onto the fibers 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical cable that can be freely installed and laid out on the floor in an office.

[Conventional technology]

A conventional optical cable has optical fibers 1, 1 and 2 as shown in FIG.
2 and a linear member 3 made of metal or the like having a similar thickness are arranged in parallel, and a sheath 4 having an elliptical cross section is provided around the wire member 3.

[Problem that the invention seeks to solve]

Due to the layout of the equipment, this optical cable needs to be bent flat as shown in FIG.

In this way, when plane bending is applied to an optical cable, since the optical fiber 1.2 is not on the bending center (neutral axis) of the cable, tensile stress is applied to the optical fiber outside the neutral axis of the bend, while the inner light The fiber is subjected to compressive stress.

For this reason, an optical fiber to which tensile stress is applied will break in extreme cases, and even in other cases, the rupture life will deteriorate.

On the other hand, optical fibers subjected to compressive stress buckle and break, or local bends (microbends) occur, leading to deterioration in transmission quality. or,
A linear member such as a metal placed in parallel with an optical fiber has high rigidity, so if the cable is bent in a plane, it will not break or buckle like an optical fiber, but it will stick out at the end of the cable. or be drawn into it.

However, since the locations where the optical fibers are placed are on the outside and inside of the optical fibers, at the cable end,
The length at which the optical fiber is protruded or retracted will differ.

Here, connectors are attached to both ends of the optical fiber in advance for connection with equipment or other cables, so if the linear member and the optical fiber protrude or are drawn in at different lengths as described above, However, there is a drawback that it is difficult to use a linear member as a tension member.

[Means for solving problems]

In the present invention, in order to solve such problems, a metal tube 6 is housed within a sheath 4 so as to be movable in the axial direction, and an optical fiber 5 is housed within the metal tube 6, as shown in FIG.

Further, the space 7 between the sheath 4 and the metal tube 6 is filled with lubricating oil or the like to increase the sliding effect. Moreover, a half-split pipe may be used instead of the metal tube 6.

[Function] According to the above configuration, even if the optical cable is subjected to a flat surface dent, the tube will not be dragged by the sheath and will bend with the center of the tube as the neutral axis, and the tension and compression will be at a level that will hardly cause problems for the optical fiber or fiber. It just adds more power. Furthermore, since the outer periphery of the optical fiber is covered and regulated by a metal tube, no local bending occurs in the optical fiber. On the other hand, when a lateral pressure load is applied from above the cable, the rigidity of the metal tube keeps the deformation to a minimum, so no microbend occurs in the optical fiber.

〔Example〕

The present invention will be explained below based on examples.

FIG. 2 is a diagram showing an embodiment of the present invention. In this embodiment, three optical fibers 5a, 5b, 5c are arranged in a metal tube 6.
It is designed to accommodate.

FIG. 3 is a diagram showing still another embodiment of the present invention, in which 7 is an aluminum (A1) tape laminated with polyethylene 8, and the same members as in FIG. 2 are given the same reference numerals.

In this embodiment, an aluminum tape laminated with polyethylene is wrapped around the optical fiber 5 to form it into a pipe shape, which is then housed in the sheath 4.

〔Effect of the invention〕

According to the present invention, when the cable is subjected to flat surface bending due to the metal existing around the optical fiber sliding with the sheath, the optical fiber is not dragged by the sheath and bends with the center of the optical fiber as a neutral axis. It is not subject to tension or compression forces that would cause problems. Furthermore, since the metal tube and metal coating have high rigidity, microbends do not occur in the optical fiber when lateral pressure is applied to the cable. Of course, local burrs do not occur due to bending. Furthermore, the protrusion and retraction amounts of the metal tube, metal sheath, and optical fiber at the cable end are the same, so it is a metal tube.

Metal coatings can be used as tension members.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention, FIGS. 2 and 3 are diagrams showing an embodiment of the present invention, and FIGS. 4 and 5 are diagrams showing a conventional optical cable. In the figure, 4 is a sheath, 5° is a rice fiber, 6 is a metal tube, and 7 is an aluminum tape. Puzzle 1 Figure No. 1? Figure Aluminum Chi 70 <b) Figure 3

Claims (1)

[Claims] 1. An optical cable comprising a metal tube housing an optical fiber and a sheath covering the metal tube so as to be movable in the axial direction. 2. An optical cable comprising an optical fiber whose outer periphery is coated with a metal tape and a sheath which covers the optical fiber so as to be movable in the axial direction.