A fiber-optic sensing system for rock mass monitoring in coal mines

We present and discuss an experimental fiber-optic sensing system developed for application in a coal mine. One of the major issues of coal mine engineering is the condition of the rock mass above the roadways in which miners extract coal. The condition is typically monitored using measurement anchors with electronic strain gauges. In the demonstrated system, the electronic sensors are replaced with FBGs. A fundamental cell of the network consists of gratings that are glued to a special groove on the anchor, while the output signal is read out with an interrogation system. The interrogator is realized either using a commercially available device or with a photonic integrated circuit. The system has been assembled and tested both in the anchor laboratory and in a test site in a roadway of a mine. The first characterization results are promising and prove the feasibility of fiber-optic sensors for rock mass monitoring.