A novel optic fiber interferometer for distance measurements over a wide measurement range using an artificial neural network is designed. The optical phase of the interferometer is simultaneously modulated with a frequency modulated laser diode and optical path-length difference. To enlarge the measurement range and eliminate the influence of the cross-sensitivity, the interferometer readings are used as input data and the actual sensed measuring value as desired output data during the training process of the network model. The principle and signal processing system containing the ANN are described. The experimental results show the use of ANN could widen the measurement range and enhance the measurement accuracy.