Theoretical investigations on the non-local effect in a long-distance Brillouin optical time-domain analyzer based on bi-directional Raman amplification

Abstract

The influence of the non-local effect on sensing performance in a long-distance Brillouin optical time-domain analyzer (BOTDA) based on bi-directional Raman amplification has been investigated theoretically. The system error induced by the non-local effect worsens with increased powers of probe wave and Raman pump. For smaller Brillouin pump power, the non-local effect is almost independent of Brillouin pump power. For larger Brillouin pump power, the non-local effect deteriorates gradually due to Raman gain saturation and cross-gain modulation (XGM). The purely backward pumping (relative to probe light) is preferable for non-local effect suppression. The frequency-division multiplexing (FDM) and time-division-multiplexing (TDM) technologies exhibit similar performance for suppressing the non-local effect under the same conditions. The sensing range near the far-end (relative to the Brillouin pump) should be appropriately shorter to minimize the non-local effect in FDM and TDM. The physical mechanisms of the non-local effect in long-distance BOTDA with Raman amplification are also shown.