A method of and apparatus for identifying fibers of fiber optic cables is disclosed. Waveforms may be generated by integer subdivision of a clock, the waveforms for modulation of a laser beam into a set of unique signals. Preferably, however, each waveform has two states and a different integer X associated therewith. The repeat period of the waveforms is preferably set at 2Y cycles of the clock, Y being an integer greater than the highest value of X, and the waveforms can be generated by counting X mod Y and changing the state of each waveform whenever this counting reaches or exceeds Y. The signals may be applied either successively or simultaneously to individual fibers at one end of a fiber optic cable. At another end of the cable, each signal can be detected as having a frequency by taking a Fourier Transform; the frequencies detected preferably being in arithmetic progression, whereby each fiber can be identified individually.