The use of Walsh functions in modulating pump light of high-spatial-resolution BOTDA with NRZ pulses

Abstract

We have previously introduced phase modulation into pulsed pump of Brillouin Optical Time Domain Analysis (BOTDA) in order to obtain high spatial resolution. In this study, we propose to use Walsh functions in coding nonreturn- to-zero (NRZ) formatted pump pulses of the high-spatial-resolution BOTDA to increase signal-to-noise ratio (SNR). Contrary to previous reports, it is numerically and experimentally verified that the use of the Walsh functions in the high-spatial-resolution BOTDA allows the increase in SNR without deteriorating its spatial resolution expected. We demonstrate measurements with 1.5 dB improvement in SNR and with approximately 0.2 m spatial resolution.