Optical fiber sensors for landslide monitoring

We present a landslide monitoring approach using a high-resolution distributed fiber stress sensor based on polarizationsensitive optical frequency reflectometry (P-OFDR) technology. The sensing system consists of a polarizationmaintaining (PM) fiber and an OFDR with a high spatial resolution. The PM fiber is used as a distributed sensing element. The OFDR is used to measure the polarization mode coupling loss in PM fiber causing by the external pressure along the PM fiber. With the advantages of frequency domain technique and coherent detection, the sensing system can achieve high spatial resolution, high sensitivity and large dynamic range. By monitoring the mechanical property distribution and variations in the landslide body, the occurrence of the landslides can be predicted accurately. We demonstrate an early landslide warning system based on polarization-sensitive distributed fiber stress sensor, which has a spatial resolution of 5cm, dynamic range of about 70dB and theoretical measuring range of 10km. The warning system is also investigated experimentally in the field trial.