Curvature and shape distributed sensing using Brillouin scattering in multi-core fibers

Abstract

Distributed curvature and shape sensing using Brillouin scattering in multi-core fiber (MCF) is presented for the first time to the best of our knowledge, by exploiting bend-dependent Brillouin frequency shift (BFS) in off-center cores.

Recent developments in fibre optic shape sensing

“…In recent years, advancement of research on effect of bend on Brillouin scattering frequency shift in multicore fibres has introduced a novel principle for FOSSs, promising long range full 3D shape sensing [61][62][63][64]. The latest research study has experimentally demonstrated use of conventional Brillouin optical time-domain analysis (BOTDA) for a 1 kilometre long multicore fibre bend sensing; however, further work is required to develop it to a FOSS [61].…”

Demonstration of distributed shape sensing based on Brillouin scattering in multi-core fibers

“…The principle of the here proposed method for distributed shape sensing is based on the linear dependence that the BFS of off-center cores in MCFs shows on the fiber curvature 5 . In particular, when a MCF is bent at a given position, different tangential strains are locally induced in each of the lateral cores, thus leading to different variations of the BFS.…”

“…In fact, the unique feature of MCF, containing multiple spatially isolated and independently transmitted channels, also provides a platform for distributed sensing applications. Recently, we reported the observation of the bending-dependence of the Brillouin frequency shift (BFS) in off-center cores in a MCF 5 , revealing that the BFS varies with a linear dependence on the local fiber curvature (the reciprocal of bending radius). This has demonstrated the potential of MCFs for distributed curvature and shape sensing based on conventional Brillouin sensing interrogation techniques.…”

“…From Eq. (3) the local bending angle  () b z and curvature () z (the reciprocal of bending radius) can be calculated as 5,7 : The experiment setup shown in Fig. 1(b) has been used to demonstrate distributed shape sensing based on conventional BOTDA, where the differential pulse-width pairs technique has been employed to achieve 20 cm spatial resolution 6 .…”

“…It should be pointed out that, to provide a known reference of the bending angle for measurements to be compared with, the core's orientation of the patterned MCF has been positioned before measurement using the visual procedure as described in Ref. 5. The BFS profiles measured along Core 1, Core 2 and Core 3 (see Fig.…”