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). While installers are aware of the fundamental importance of minimum bend radii, they often lack the practical know-how to. The fiber optic bend radius refers to the smallest radius a fiber cable can be bent without causing unacceptable signal degradation or physical damage. It is measured from the inside of the bend, not the outer curve. Fiber optic cables transmit data through light propagation within a glass core. Exceed it repeatedly, around truss corners, over stage decks, wound tight on undersized reels, and you're stacking up loss that.