Long-distance random fiber laser sensing system with wide sensing bandwidth

Raman random lasing (RRFL) can be generated in a long fiber waveguide which is beneficial for long-distance transmission of sensing information. However, remote sensing based RRFL has only been demonstrated in quasi-static scenarios due to the limitation of spectral demodulation speed. In this work, we extend the RRFL remote sensing scenario from quasi-static to dynamic, and present methods for further achieving multi-point dynamic sensing and enhancing the sensing sensitivity. Particularly, we first investigate the RRFL sensing bandwidth by analyzing the temporal and spectrum evolution of the RRFL buildup. By using a novel frequency-to-time mapping method, a 100 km remote dynamic sensing is realized and achieved 65 kHz signal demodulation. In addition, the scheme can be extended to multi-point dynamic sensing by combining the frequency division multiplexing method. This work paves the way for ultra-high-bandwidth and ultra-long-distance interrogation for optical fiber sensors.