SUN-OFC-A small, lightweight optical fiber fault locator, the output red laser visible to human eyes, can efficiently enter single mode and multimode fiber. The red light with the introduction of optical fiber connectors, multi-core cable can be used as the control line SMIC; check fiber OTDR can not find fault point (breakpoint, the beginning or the end of the optical properties) and high loss caused by microbending section. For example, fiber jumpers, pigtails, junction box in the bare optical fiber core line or so.