Optic fibre sensor for real-time damage detection in smart composite

In this study an optical fibre sensor system was conceived for simultaneous detection of the strain and the acoustic emission due to damage. It consists of a fibre Bragg grating and a Fabry–Pérot interferometer. For the interrogation of the Fabry–Pérot cavity, an innovative low cost process based on the generation of two quadrature phase-shifted signals using two fibre Bragg gratings was implemented, allowing the recovery of the change in the cavity length. An automated processing system, based on Kohonenʹs self-organizing maps is also presented, for future classification of the acoustic emission waves detected by the optic fibre sensor.