Balanced Detection for Performance Enhancement in a Pulse-Coded Brillouin Optical Time Domain Analyzer

A pulse-coded Brillouin optical time domain analyzer (BOTDA) so far uses the single-sideband photo detection. Here, thanks to a specially designed Brillouin gain extraction scheme, the dual-sideband balanced photo detection is successfully employed in a pulse-coded BOTDA. Compared with the single-sideband detection, the balanced detection can effectively eliminate common-mode noises existing in the two sidebands of the commonly used dual-sideband probe. In addition, the signal-to-noise ratio (SNR) at the far fiber end can be enhanced by 1.5 dB. The two benefits are experimentally demonstrated in a 117.46-km Golay-coded BOTDA, resulting in the reduction of the Brillouin frequency shift (BFS) measurement uncertainty from 30 km to the far fiber end.