Fig. 1. Experimental system setup

Fig. 2. Rayleigh backscattering (RBS) intensity spectra at given position before and after applying strain

Fig. 3. Schematic diagram of spectrum extension algorithm. (a) Process of spectrum splicing extended to the right; (b) splicing weight ratio within range of [Δfk,Δfk+1]; (c) reference spectrum after algorithm splicing and extension

Fig. 4. Superposition of positive frequency cross-correlation and negative frequency cross-correlation

Fig. 5. Demodulation of strain changes applied by PZT. (a) Strain changes relative to the first detection; (b) comparison between cumulative result of relative changes and demodulation results of spectrum extension; (c) cross-correlation at each moment of cumulative method; (d) cross-correlation at each moment of spectrum extension demodulation; (e) comparison of changes in cross-correlation peak values; (f) strain demodulation result when no voltage is applied to PZT

Fig. 6. Demodulation of 198 με strain change applied by electrokinetic displacement platform. (a) Cross-correlation results at various times; (b) variation of cross-correlation peak values; (c) matching between extended spectrum and spectrum to be measured at 308 ms; (d) spectrum extension demodulation result