Distributed sensing requires a position-dependent response and this is only possible through 2 types of optical interactions with the fibre material: scatterings (Rayleigh, Brillouin, Raman) and non-linearities (Kerr-based effects, stimulated scatterings). Scatterings cause a partial redirection of the light in the backward direction (change of the wavevector direction), while the nonlinearities make possible the transfer of light between 2 distinct lightwaves (light sensitive to the presence of light). Such interactions are very dependent on the power of the stimulating light and show a better response for an increased power. Therefore new optical sources based on doped fibres or semiconductor materials are of particular importance owing to their higher power and better spectral properties.

In the frame of this Action, the implementation of distributed measurement techniques is studied to characterize several important fibre parameters and to evaluate many external quantities for sensing purpose.

The discussions and studies are divided along two main directions. The first one studies OTDR/OTDA-based techniques for measuring the spatial distribution of the parameters. The second study direction focuses on the use of nonlinear effects for metrology and sensing, for instance the use of nonlinear supercontinuum sources for optical coherence tomography (OCT) and other measurements.