The OS405 (635nm) visible laser cable fault locator allows the operator to find faults in fiber optic cables, even in the OTDR dead zone, optimizing splices and tracing fibers. By injecting a bright red visible light in the fiber, locations of losses such as breaks, bends, or bad connectors can be detected visually, even through the typical yellow or orange jacket used on most single fiber cables. Fibers can be traced as far as 4 km (2.5 mi.) using this instrument. The OS405 uses a visible diode laser in the compact case for pocket size convenience.