Breaking the resolution-distance trade-off: 50-cm spatial resolution over 14 km using correlation demodulation in Raman distributed fiber sensors

The spatial resolution and sensing distance of Raman distributed optical fiber sensors are constrained by the pulse width and the inherently weak Raman scattering signals. Consequently, the spatial resolution for kilometer-level detection distances is typically limited to the order of meters. To address this principle limitation, this study proposes a Raman distributed optical fiber sensing scheme based on amplified spontaneous emission (ASE) correlation detection. By performing a cross correlation operation between the ASE detection signal and the reconstructed Raman anti-Stokes signal, the system effectively captures the weaker intensity information of Raman anti-Stokes light, thereby enhancing spatial resolution. Experimental results demonstrate a spatial resolution of 50 cm over a distributed temperature-sensing distance exceeding 14.0 km.