ABSTRACT
This chapter proposes a method of simultaneous measurements of two optical fiber lengths. A semiconductor optical amplifier based fiber ring laser with an external optical feedback was constituted which can work in chaotic state. By using two different time intervals of autocorrelation peaks or two different frequency intervals of resonant peaks in the spectrum function of the chaotic signal, the two fiber lengths were simultaneously obtained in a measurement process. The lengths obtained with the spectrum analysis method are closer to the reference one than that with the autocorrelation method. The autocorrelation method is better than the spectrum analysis method in respect to the measurement stability. For a chaotic laser with optical feedback, the timedelay signature is not only embodied in the autocorrelation function but also in the spectrum function of the chaotic waveform. The lengths obtained with the spectrum analysis method are closer to the reference one than that with the autocorrelation method.
