The fibre optic bending radius fundamentally determines the functionality and lifespan of optical fibre installations – for modern fibre optic cables, a minimum bending radius of 60 mm applies to permanent installations in conduits, while temporary bends during installation allow up. The fibre optic bending radius fundamentally determines the functionality and lifespan of optical fibre installations – for modern fibre optic cables, a minimum bending radius of 60 mm applies to permanent installations in conduits, while temporary bends during installation allow up. Corning Optical Communications cable specification sheets also list the minimum cable bend radius both “Loaded” (during installation) and “Installed” (after installation). The following formulas may be used to determine general guidelines for installing Corning Optical Communications' fiber optic. Bending of a fiber optic cable can damage the cable if the curvature of the bend is too small. 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. Note:. Fiber optic cable bend radius is a critical mechanical parameter that determines how sharply a cable can be bent without risking microbending, macrobending, signal loss, or long-term structural fatigue. When not under tension (after installation), the.