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.

I. Introduction

The distributed fiber sensor (DFS) based on Brillouin effect has been paid special attention due to its important applications including health monitoring in structure, oil pipeline, etc. Two types of Brillouin-based DFS are used. The first is Brillouin optical time-domain reflectormetry (BOTDR) [1]. The second is Brillouin optical time-domain analyzer (BOTDA) [2]–[11].