A distributed optical fibre sensing system is used to measure landslide-induced strains on an optical fibre buried in a large scale physical model of a slope. The fibre sensing cable is deployed at the predefined failure surface and interrogated by means of optical frequency domain reflectometry. The strain evolution is measured with centimetre spatial resolution until the occurrence of the slope failure. Standard legacy sensors measuring soil moisture and pore water pressure are installed at different depths and positions along the slope for comparison and validation. The evolution of the strain field is related to landslide dynamics with unprecedented resolution and insight. In fact, the results of the experiment clearly identify several phases within the evolution of the landslide and show that optical fibres can detect precursory signs of failure well before the collapse, paving the way for the development of more effective early warning systems.

This paper presents a completely new method able to characterize polarization mode dispersion (PMD) properties of randomly birefringent single-mode fibers, using polarization sensitive backscattering technique. We show analytical relationships between evolution of polarization state of backscattered signal with respect to state of polarization of forward one. Our technique allows one to measure differential group delay, beat length, and correlation length at the same time over long single-mode fibers using only one fiber end. Experimental data fit very well with numerical results, confirming the capability of our technique for fast routine characterization of PMD during cabling, before and after installation

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Multimode optical fibers have recently received revived attention in the framework of space-division multiplexed systems, where the spatial diversity of fiber modes is exploited to increase transmission capacity. The complexity of these systems strongly depends on the coupling characteristic of the fiber. Therefore, a better description of coupling effects may lead to the more accurate modeling of the system and to an optimized design of multimode fibers. In this paper, we analyze coupling among (quasi) degenerate modes as a consequence of different kinds of coupling sources.

The statistical properties of the random birefringence that affects long single-mode fibers are experimentally evaluated by means of a polarization-sensitive optical time-domain reflectometry. The measurements are in good agreement with theoretical predictions and show, for what we believe is the first time, that the components of the local birefringence vector are Gaussian random variables.