Contribution
DAS - acoustical measurements inside different environments
* Presenting author
Abstract:
The sea bottom of coastal waters like the Baltic Sea is covered by a web of power and communication cables. Recent advances in Distributed Acoustic Sensing (DAS) have made it feasible to transform each of these subsea cables into extended and close-meshed sensor arrays.DAS measures microscopic changes in the optical length of the fiber, and is therefore sensitive to changes in the fiber strain induced by acoustic waves. Thus, a DAS system converts a subsea cable into a long (~100 km) virtual hydrophone array with high spatial resolution (~10 m). Since the sensitivity of DAS reaches down into the sub-Hz range it can adopt the role of a pressure sensor at the same time.We present how DAS can be used to detect surface vessels in different environments. Cables with different internal structures at water depths ranging from 10 m to 1500 m embedded in sea bottoms including mud and sand were employed. The overall goal is to obtain a physical understanding how environmental parameters like weather conditions and sea bottom structure but also the structure of the cable itself affect the measurement performance. Ultimately, this will make it possible to establish propagation models in the future.