1. Field of the Invention
The invention relates to optical communication cables and somewhat more particularly to optical communication cables having reinforced casings.
2. Prior Art
The art is aware that optical transmission elements of optical communication cables must be protected against most various types of mechanical stresses. Such protection is usually provided by a suitable structural design of the cable core and/or the cable casing, among other elements.
Thus, for example, tension-proof elements are embedded in synthetic casings of cables. Such tension-proof elements, which for example, are composed of steel, glass, synthetic materials, graphite, etc., function to protect the cable core against excessive longitudinal stresses which may be caused by tensile force or temperature changes (cf. in this regard German Offenlegungsschrift, hereinafter DT-OS, 2,727,315; British Patent Specifications No. 1,462,160; 1,483,845 and 1,501,800).
Embedding tension-proof elements in a cable casing during its extrusion is expensive from a production technology point of view. Casing structures in which coverings or interlacings of tension-proof elements are arranged between two layers of a synthetic casing or on the inside of such a casing are, on the other hand, easier to produce (cf. in this regard British Patent Specification No. 1,453,402; U.S. Pat. No. 4,076,382 and German Auslegeschrift No. 2,628,069).
From tension-proof designs of electrical cable structures having synthetic material casings, it is known to unite tension-proof elements into a tape-like structure and to apply this tape longitudinally or in large lengths of lay onto the cable core. Such tape is then bonded or welded to the casing structure (cf. in this regard DT-OS Nos. 2,522,849; 2,204,367; 2,259,703 and German Pat. No. 1,510,123). With this type of construction as well as with the construction of the reinforced optical cable structures mentioned earlier, one must accept the fact that the cable as a whole is relatively stiff (i.e., inflexible) because of the material interlacing or bonding connection between the tension-proof elements and the synthetic casings.
Suggestions have been made that in order to overcome this difficulty in electric cables, that the tape formed of tension-proof elements be connected with the synthetic casing only at intervals of approximately one length of lay. This type of construction provides a certain degree of mobility to the tension-proof elements and improves the flexibility of the resultant cable structure.