JDSU's FI-11 hand-held optical fiber identifier probe is a rugged, easy-to-use installation and maintenance instrument which identifies optical fibers by detecting the optical signals being transmitted through a single mode fiber. By utilizing local detection technology (non-destructive macro-bend detection), it eliminates the need to open the fiber at the splice point identification; eliminating the probability of interrupting service. Signals detected include continuous wave (CW), live optical transmission, and low frequency modulated tones at 270, 1000 and 2000 Hz. When traffic is present on the fiber tested, the direction of transmission is indicated by the JDSU FI11's LEDs illuminating on the probe. When modulated tones are present on the fiber under test, the unit will detect and illuminate the corresponding LED 270, 1000 or 2000 Hz. The relative core power in the fiber is measured and displayed on a two-digit, seven-segment LED display. With the JDSU FI11 this allows the measurement of power loss through a splice or connector.