Experimental Demonstration on 2.5-m Spatial Resolution and 1 $^{\circ}$C Temperature Uncertainty Over Long-Distance BOTDA With Combined Raman Amplification and Optical Pulse Coding

The combination of Raman amplification and optical pulse coding (OPC) is proposed to reduce the frequency uncertainty in a long-distance Brillouin optical time-domain analyzer (BOTDA) under higher spatial resolution. The experimental characterization of temperature sensing with measurement accuracy ~ 1°C under ~ 2.5-m spatial resolution over a whole length of sensing fiber is demonstrated. The sensing fiber is composed of 49.6-km fiber at 10.8-GHz Brillouin frequency shift (BFS) and 25-km fiber at 11.005 GHz.