Curvature radius of duct optical cable laying

The normal recommendation for fiber optic cable is the minimum bend radius under tension during pulling is 20 times the diameter of the cable (d). Corning Optical Communications cable specification sheets are available which list the maximum tensile load for various cable types. The maximum pulling tension for stranded loose tube cable and ribbon cable is 600 lbF (2,700 Newtons). Damage may not always be obvious, like a kink in the cable, but may include broken fibers, fibers with higher loss due to stress and cable structural damage that may lead to reliability problems. If bent smaller than this radius, the internal structure of the cable will be under too much pressure, and. [pdf]