The FI-100 fiber identifier allows the technician to quickly determine the approximate core power and signal direction in a fiber optic cable without disconnecting the fiber. A non-intrusive macrobend is created so that only a small insertion loss is created, thus the technician can probe fibers without causing an alarm condition. The integrity of critical services is maintained. Tone detect technology is employed so that the technician can uniquely trace signals once again without disconnecting fibers with potentially critical services.