For several years, Brillouin-based optical fiber sensors plays an important roles in the fields of distributed temperature and strain measurements in the real world. Among these sensors, the optical chirp chain (OCC) based Brillouin optical fiber sensor is a good candidate to realize ultrafast distributed sensing, which is of great importance to distinguish quickchanging events in practical applications. In this paper, the principle of OCC and the OCC based Brillouin optical timedomain analysis (BOTDA) sensing are introduced. In OCC-BOTDA, there are three types of spectral distortions, i.e. the back end distortion, the frequency lag of main peak and the frequency saltation distortion, which are influenced by the transient stimulated Brillouin scattering, are verified in the simulation and experiment in this paper and attributed to the rapid frequency sweeping.
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