Fibre Bragg grating inscription into a seven core fibre and its application as a vector bending sensor

This paper demonstrates a highly effective method for fibre Bragg grating (FBG) inscription into a seven core fibre (7CF) and its application as an effective vector bending sensor. The development of multicore fibres (MCFs) and enabling the fabrication of FBGs into them result in a solution for multi-parameter measurements such as temperature/strain/bending/twist. The FBG in the central core of 7CF is on the neutral axis and therefore it is sensitive only to thermal and insensitive to deformational change, whereas the FBGs in the none-central cores that are evenly distributed over the 7CF cross-section can facilitate the measurement of structure deformation, such as bending, loading and twist. Furthermore, the FBGs in different cores respond to the physical perturbations differently in various orientations, offering vector sensing to measure both amplitude and direction of the structure change. The 7CF-FBG sensors are highly applicable for mechanical structures and flexible medical instruments