The term bending radius is used in cabling technology and for flexible printed circuit boards. As far as cable technology is concerned, the characteristic value bending radius is used equally for cables with metallic conductors such as TP cables or coaxial cables and also for cables with optical fibers.
- Incabling, the bending radius is the smallest bend that a cable may take during installation without changing the cable properties. The bending radii are specified in relation to the cable diameter and depend on the transmission medium. In the case of coaxial cables, they depend on the cable structure, and in the case of optical fibers, on their type and structure. When one speaks of bending radius, one always means the smallest possible bending radius. For fiber optic cables, the manufacturer's specifications for the minimum bend radius are ten times the outer diameter of the fiber optic cable. According to this rule of thumb, an optical fiber with an outer diameter of 5 mm, for example, has a bending radius of approx. 5 cm. Since there are very many applications where a tighter bending radius is required, there are special bend-optimized fibers(BIF) with bending radii of a few millimeters. The situation is different for coaxial cables. Here, the bending radius depends on the type of shielding. For single-shielded coaxial cables, 5 times the cable diameter applies; for double-shielded cables, 10 times. The EN cable standard specifies a lower value, which corresponds to 4 times the cable diameter. In general, the manufacturer's specifications apply, which often also differentiate between the bending radius during installation and for the attached cable. Attention must be paid to these specifications, as light can also escape via the cladding glass in the case of extremely strongly curved optical fibers.
- The term bending radius is also used in printed circuit board technology, namely for flexible printed circuit boards. FPC) depends on the number of layers and the thickness of the flexible printed circuit board. For single- layer flexible circuit boards, 6 times the board thickness is used, for multilayer flexible circuit boards 15 to 25 times the value.