Spectral characterization of distributed Brillouin sensors in the transient regime

Abstract

Brillouin scattering based fibre optic sensors have been actively researched over the past decade due to their enhanced sensitivity to environmental parameters such as temperature and strain. Applications range from dynamic health monitoring of civil structures such as bridges, pipelines, and nuclear reactors to real-time threshold applications such as fire detection. As temperature and strain changes often represent the first symptoms of structural degradation, the development of Brillouin scattering based technology will bear considerable scientific as well as economic benefit. Brillouin sensors employing the probe-pump amplification technique obtain distributed spatial information along a fibre using narrow pulses. In this study, the impact of pulse width and extinction ratio on the overall Brillouin spectrum shape is investigated. From independent theoretical and experimental investigations, a comprehensive curve fitting method is proposed to reveal the physical nature of Brillouin scattering in the transient regime.