Development of optical sensors with FBG for vibrational analysis

The detection and study of vibrations play a fundamental role in the monitoring and safety of major engineering systems. This is especially true in the aerospace sector where the operating environment is hostile and the constraints on weights and dimensions are extremely tight. For these reasons, the research and use of sensors based on optical signal transmission is becoming increasingly important. The opportunity to implement distributed measurements along a single fibre, the small size and weight and the high resistance to electromagnetic interference make this technology an ideal candidate for the development of next-generation aerial platforms. In this paper the operating principles and main concepts behind optical signal transmission are introduced, with particular emphasis placed on the type based on Fibre Bragg Grating (FBG). The objective is to better understand the main merits and shortcomings of this solution, for vibration sensing, and the creation of possible designs to be realised for subsequent study in the laboratory. This is done through a careful literature search and a classification of the main existing architectures. Subsequently, a possible device capable of compensating for the major problems of this solution is proposed, and the dynamic and sensitivity characteristics of the sensor are studied. A great deal of attention is paid to the properties of the support on which the fibre is to be placed, as this has a very important effect on the performance. This is possible thanks to a mathematical modelling of the problem and the implementation of a Matlab script capable of estimating dimensions, weights and dynamic performance then verified through FEM modelling.