A Visual Fault Locator (VFL) is a handheld tool used to detect faults in fiber optic cables. It emits a visible red laser light (usually at 650 nm) through the fiber, helping technicians identify issues such as breaks, bends, and poor splices. The laser light leaks out at the point of fault, making. By injecting the light from a visible source, such as a LED, laser or incandescent bulb, one can visually trace the fiber from transmitter to receiver to ensure correct orientation and check continuity besides. The simple instruments that inject visible light are called fiber tracers or visual. It gives instant visual proof of where light escapes the fiber. Even beginners can spot bends, cracks, or bad splices without complex tools.