Smart slope monitoring through the use of fibre optic sensors

Abstract: This study demonstrates the use of fibre optic instrumentation such as an Optical Time-Domain Reflectometer as well as Fibre Bragg Grating sensors on a small-scale physical 1-g model to monitor potential slope movement. The scope is to improve current knowledge in the field of slope monitoring through the im- plementation of optic fibre sensors. Single-mode and multi-mode hetero-core optic fibre displacement sensors were created and directly embedded into layers of coarse-grained soil. By inducing critical slope conditions in the small-scale model through the course of several experiments we were able to identify localised failure zones and quantify signal attenuation. Using a calibrated source, it was possible to indirectly estimate microstrain and investigate spatial resolution of the sensing cable. Laboratory testing of the sensors and the sensing system allowed for further development of sensor integration techniques

Optical fiber sensing cables for brillouin-based distributed measurements

Brillouin distributed optical fiber sensing (Brillouin D-FOS) is a powerful technology for real-time in situ monitoring of various physical quantities, such as strain, temperature, and pressure. Compared to local or multi-point fiber optic sensing techniques, in Brillouin-based sensing, the optical fiber is interrogated along its complete length with a resolution down to decimeters and with a frequency encoding of the measure information that is not affected by changes in the optical attenuation. The fiber sensing cable plays a significant role since it must ensure a low optical loss and optimal transfer of the measured parameters for a long time and in harsh conditions, e.g., the presence of moisture, corrosion, and relevant mechanical or thermal stresses. In this paper, research and application regarding optical fiber cables for Brillouin distributed sensing are reviewed, connected, and extended. It is shown how appropriate cable design can give a significant contribution toward the successful exploitation of the Brillouin D-FOS technique