During the installation process, maintain a minimum bend radius of 20 times the cable diameter under tension, and 10 times after installation. Ignoring these rules leads to improper installation, signal loss, and costly cable damage. 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. Exceed it once and you might get away with it. Exceed it repeatedly, around truss corners, over stage decks, wound tight on undersized reels, and you're stacking up loss that. ter the cable has been placed in the raceway. Simply put, it is: how small the cable is allowed to bend but not being damaged.