Chaos Raman distributed optical fiber sensing using bandwidth-tailored chaos laser for enhanced SNR and temperature localization

Raman distributed optical fiber sensing enables long-range temperature monitoring, but its performance is constrained by the weak Raman backscattered signal and the limited bandwidth of photodetectors. Although cumulative averaging can improve SNR, the corresponding increase in measurement time restricts sensing efficiency. Meanwhile, the spatial resolution of Raman sensing has advanced from the meter scale to the 10-cm regime, making the localization precision of small-scale temperature anomalies increasingly important. In this study, we experimentally demonstrate a Raman distributed optical fiber sensing scheme using a bandwidth-tailored chaos laser, incorporating a fiber Bragg grating (FBG) filter to increase the detectable signal power within the APD bandwidth. The FBG shifts the chaos spectral centroid from approximately 6 GHz to 600 MHz and increases the fraction of chaos spectral energy within the APD bandwidth from 0.4% to about 32%. This increased in-band chaos energy strengthens the Raman backscattered signals. After reconstruction, compressing correlation demodulation with cumulative averaging, the SNR of the cross-correlation peak reaches approximately 7.5 dB, which is about 4 dB higher than that obtained with the chaos source without the FBG. Furthermore, as the demand for higher spatial resolution increases, achieving better localization precision becomes even more important. However, limited sampling can introduce noticeable fluctuations in the non-interpolated correlation trace. To address this, we incorporate Spline interpolation into the correlation-trace processing, which sharpens the peak and improves the localization precision to the sub-centimeter level, providing a practical advantage for identifying small-scale thermal events. In summary, we demonstrated a bandwidth-tailored chaos sensing scheme that enhances SNR through spectral shifting and improves localization precision through interpolation. It provides a simple yet effective way to improve the performance of Raman distributed optical fiber sensing.