The fiber optic 90-degree bend refers to the minimum radius required when cables must change direction at right angles. Similar to how a garden hose restricts water flow when kinked, fiber optic cables experience performance degradation or complete signal loss when bent too sharply. During installation under tension, maintain a minimum bend radius of 20 times the cable's outer diameter, while post-installation requires a minimum long-term bend radius of 10 times the cable diameter. Fiber macro-bending happens when the optical fiber undergoes curves due to bend after cabling.