Long Range Distributed Optical Acoustic Sensor Based On In-Line Raman Amplification

The volume of research on distributed optical fibre vibration sensors, also known as distributed acoustic sensors (DAS), has increased substantially in the recent years. DAS systems owe their rising popularity to their capability of mapping vibrations along tens of kilometres of optical fibre. With an increasing demand for DAS systems in areas such as subsea cable monitoring [1], earthquake analysis and geophysical sciences [2], and railway monitoring [3], developing DAS systems with higher sensitivity and longer sensing range is of outmost important.