Fiber optic cables are designed to withstand some bending, but excessive bends can physically damage the glass fiber or cause significant signal loss. That's why every fiber cable has a minimum bend radius specification provided by the manufacturer. The minimum bend radius defines the smallest. 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. Ignoring these rules leads to improper installation, signal loss.