Fig. 1. Raman scattering trace for different detection pulse schemes. (a) Trace of ΔLFUT>ΔLpulse for single pulse; (b) trace of ΔLFUT=ΔLpulse for single pulse; (c) trace of ΔLFUT<ΔLpulse for single pulse; (d) trace of ΔLFUT>Sum(ΔLpulse) for paired-pulse; (e) trace of Min(ΔLpulse)<ΔLFUT<Max(ΔLpulse) for paired-pulse; (f) trace of ΔLFUT<Min(ΔLpulse) for paired-pulse. Sum(ΔLpulse)=(τA+τB+τ0)c/2n0.

Fig. 2. CAPC scheme and demodulation principle: (a) CAPC system scheme; (b) demodulation principle of time-domain differential refactoring and chaotic correlation-enhanced.

Fig. 3. Correction principle of small FUT positioning. (a) Trace of chaotic probe pulse; (b) trace of chaotic Raman scattering; (c) trace of chaotic correlation.

Fig. 4. CAPC experimental setup for Raman distributed fiber-optic sensing.

Fig. 5. Characteristics of chaotic continuous signals and chaotic asymmetric paired-pulse signals. (a) Light spectrum of chaotic laser; (b) power spectrum of chaotic laser; (c) timing of chaotic laser; (d) normalized autocorrelation of chaotic laser; (e) timing of chaotic asymmetric paired-pulse; (f) normalized autocorrelation of chaotic asymmetric paired-pulse.

Fig. 6. Results of the CAPC and single-pulse schemes. (a) Chaotic correlated traces of two schemes; (b) details of the FUT.

Fig. 7. Results of different FUT experiments. (a) Original experimental results; (b) FUT corrected results.

Fig. 8. Experimental results at different temperatures. (a) Correlated trace of 60°C; (b) correlated trace of 70°C; (c) correlated trace of 80°C; (d) correlated trace of 90°C; (e) result of temperature and positively correlated peak; (f) result of temperature demodulation.

Fig. 9. Relationship between chaotic bandwidth and spatial resolution. (a) FWHM of chaotic timing autocorrelation at 200 MHz; (b) relationship between chaotic bandwidth and spatial resolution.

Fig. 10. Effect of pulse width on the CAPC system: (a) main pulse width and spatial resolution; (b) auxiliary pulse width and spatial resolution; (c) main pulse width and system SNR; (d) auxiliary pulse width and system SNR.