Fig. 1. (a) Two modulation steps to obtain the frequency-scanning optical pulses. (b) The sequence diagram of the pump pulses and probe wave.

Fig. 2. The frequency relationship between the Rayleigh scattering and Brillouin signals.

Fig. 3. (a) Simulated Rayleigh intensity distribution along 1 GHz frequency span: reference spectrum (black short dash line) and measured spectrum (red line). (b) The BGSs of the initial state (black short dash line) and final state (red solid line).

Fig. 4. The experiment setup of the proposed sensor by combining the Rayleigh and Brillouin measurements.

Fig. 5. (a) The cross-correlation between Rayleigh spectra along the FUT containing the relative sub-micro strain information. (b) The measured 3-D BGSs along the FUT, showing the pre-applied strain information.

Fig. 6. (a) The measured Rayleigh spectra recording a 1000 nε relative strain change with a step of 100 nε. (b) The frequency shift in different relative strain change and its linear fitting result. (c) The measured BGSs at different strains from 220 με to 3970 με. (d) The BFS in different strains and its linear fitting result.

Fig. 7. Two groups of vibration measurements by integrating the Rayleigh and Brillouin strain information.