Ultrafast distributed Brillouin optical fiber sensing based on optical chirp chain

In the past few years, Brillouin-based optical fiber sensors have gained significant ground for 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 quick-changing events in practical applications. In this paper, the concept, principle and sensing scheme of OCC are introduced, including the OCC Brillouin optical time-domain analysis and OCC Brillouin optical time-domain reflectometry. In OCC Brillouin optical time-domain analysis, the influence of transient interaction is reflected as three types of spectral distortions, i.e. the back end distortion, the frequency lag of main peak and the frequency saltation distortion, which are verified in the simulation and experiment and attributed to the rapid frequency sweeping. In addition, this paper reviews the OCC based cutting-edge schemes and technologies aspects to upgrade Brillouin sensors with ultra-fast and high-performance sensing capability. In the future, there are still many challenges in OCC based disturbed sensing, such as high spatial resolution, real-time demodulation and low-cost scheme.