Enhancement of sensing range of Brillouin optical time‐domain reflectometry system up to 150 km with in‐line bi‐directional erbium‐doped fibre amplifications

Brillouin optical time‐domain reflectometry (BOTDR) has the advantage of requiring access to only one end of the sensing fibre, which is an important property for some applications. The coherent detection of spontaneous Brillouin scattering allows high sensitivity of temperature/strain measurements, close to one of the well‐known Brillouin optical time‐domain analyser‐based solutions. In‐line amplification based on bidirectional erbium‐doped fibre amplification (EDFA) modules can improve sensing distance and temperature accuracy. This study demonstrates a distributed sensing over 150 km with 5‐m spatial resolution and a temperature error of less than 2°C in 10 min without requiring specific BOTDR adaptation. A record performance of 0.7°C in 60 min has been also obtained, which corresponds to the best performance obtained in reflectometer configuration at this distance.