Chaos Raman optical time-domain reflectometry for millimeter-level spatial resolution temperature sensing

The Raman optical time-domain reflectometry (ROTDR) uses the Raman backscattering signal of an optical pulse to obtain environmental information along the sensing fiber, with the pulse width limiting spatial resolution to the meter level in current systems. To solve this problem, we propose a chaos ROTDR system to eliminate the superposition effect of Raman backscattering response caused by pulse width. Here, the chaotic laser is applied as the sensing source instead of a conventional laser. For the random amplitude characteristics of the chaotic laser in time series, the chaotic Raman backscattering signal of individual points along the sensing fiber can be obtained, so that the millimeter-evel spatial resolution is realized. Firstly, the propagation equation of the chaotic Raman backscattering signal is established. Subsequently, the most relevant factors impacting the performance of spatial resolution and the signal-to-noise ratio (SNR) could be addressed based on two methods proposed in this study: one is the time-domain differential reconstruction (TDDR), and the other is the short-scale time-domain correlation compression (SSTDCC). Finally, the spatial resolution of 5 mm and temperature sensitivity of 0.1 K are achieved, which is an unprecedented breakthrough compared to the state-of-the-art technology.