Innovative optical sensors for prognostic techniques in the aerospace field: design and development of a test bench for studying the frequency response of FBG sensors.

This thesis is developed at the Department of Mechanical and Aerospace Engineering (DIMEAS) of the Politecnico di Torino in collaboration with the interdepartmental center Photonext and the Istituto Superiore Mario Boella (ISMB). The object of study and testing is the optical fiber, in particular, the FBG (Fiber Bragg Grating) sensor. FBG technology is one of the most popular solutions for fiber optic sensors. They are used to measure physical properties for instance: vibration, strain, pressure, and temperature. Typically, FBGs used as sensors have lengths of the order of 5 mm, which is very small compared to the length of the optical fiber and acts as a punctual sensor. They are environmentally more stable, immune to electromagnetic interference, highly multiplexed and in addition, they are passive components that do not need electric energy to work. The objective of the thesis is a first dynamic analysis of the FBG sensor. In particular, to set up a test bench for dynamic tests on the optical fiber and analyze its frequency response. The future concept is to use these sensors for prognostics and diagnostics activities in aerospace applications.