Fig. 1. Chaotic laser source and its output characteristics. (a) Single feedback loop external cavity chaotic laser source; (b1) optical spectrum; (b2) radio frequency spectrum; (b3) time sequence; (b4) autocorrelation curve

Fig. 2. Working principle of chaotic BOCDA. (a) Schematic illustration of principle; (b) simulation of time-space distribution of chaotic SBS acoustic field in 100 m-long fiber; (c) simulation of chaotic Brillouin gain spectrum

Fig. 3. Experimental setup diagram of chaotic Brillouin optical correlation-domain analysis technology

Fig. 4. Temperature demodulation by chaotic BGS. (a) Measured BGSs at different positions and temperatures; (b) linear relationship between BFS and temperature

Fig. 5. Results of distributed temperature measurement^[49]. (a) Chaotic BGS distribution along the FUT; (b) BFS distribution along the FUT

Fig. 6. Distribution map of autocorrelation coefficient at external cavity feedback delay position under different injection currents and feedback strengths^[50]

Fig. 7. Schematic diagram of time-gated system. (a) Technical principle; (b) experimental setup

Fig. 8. BGS comparisons of chaotic BOCDA systems with and without time-gated scheme at different fiber positions^[51]. (a) 5.0 km; (b) 8.5 km; (c) 10.0 km; (d) SBR as a function of fiber position

Fig. 9. Typical status of chaotic laser in bandwidth adjustment process^[52]. (a1)‒(c1) Radio frequency spectra; (a2)‒(c2) autocorrelation traces; (a3)‒(c3) autocorrelation center peaks and their Gaussian fitting curves

Fig. 10. Comparisons of BGS under different data acquisition methods in millimeter-level-spatial-resolution chaotic BOCDA system^[52]. (a) OPM-based scheme; (b) LIA-based scheme

Fig. 11. Results of distributed strain measurement in millimeter-level-spatial-resolution chaotic BOCDA system^[52]. (a) BGS along the FUT; (b) BFS curve along the FUT

Fig. 12. Principle of single-slope-assisted technology. (a) Schematic diagram of single-slope-assisted technology; (b) conversion coefficient between Brillouin amplitude and strain value^[54]

Fig. 13. Time traces and sine-fitted curves under different dynamic strains^[54]. (a) 0‒100 µε; (b) 0‒1000 µε; (c) 0‒1200 µε; (d) 0‒1400 µε

Fig. 14. Measurement results of DSA-CBOCDA system^[57]. (a) Measurement accuracy of static strain; (b) static strain resolution; (c) measurement accuracy of dynamic strain; (d) dynamic strain resolution