Investigation of a quasi-distributed displacement sensor using the macro-bending loss of an optical fiber

摘要

In this paper a quasi-distributed fiber-optic displacement sensor (QDFODS) for landslide monitoring using an optical time domain reflectometer (OTDR) was demonstrated. The new sensor was connected in series by several fiber-optic displacement sensors (FODSs). Their configurations introduce power loss through the decrease of their fiber bowknot radius when displacement was applied. The decrease of the light intensity with displacement variation was reported. The proposed FODS had a maximum measurement distance and an effective initial measurement displacement of 36 mm and 0.98 mm. The authors performed the laboratory experiments, and the sliding damage of the rock mass with two-stage sliding was effectively predicted by the QDFODS. Further, a field monitoring application of the QDFODS was conducted to confirm the feasibility for determining the progressive deformation characteristics of the slope, such as the magnitude of movement and positions of the potential sliding surfaces. This capability demonstrates the promising applications of the QDFODS in the monitoring of civil engineering, especially slopes, foundation pits and tunnels.