Advanced signal processing techniques for fibre-optic structural health monitoring

Fibre optic sensors can measure a range of physics and chemical parameters. Some of the more common fibre optic sensors are the fibre Bragg grating (FBG), the long period grating (LPG), the Fabry-Pérot Interferometer (FPI) and various distributed fibre optic sensors based on optical time-domain reflectometry (OTDR) and optical frequency domain reflectometry (OFDR). Each of these sensor types utilises different interrogator hardware and signal processing software. The goals of this research are to develop new algorithms for multi-parameter sensing and to improve the sensitivity and resolution of fibre optic sensing by developing new approaches. This is done by stepping back from current algorithms, and considering what additional information is expected to be present in and can be extracted from the signal. Recent publications have shown that advanced signal processing techniques can be used for bend sensing, for damage type classification and to improve the spatial resolution of the sensing. Structural health monitoring requires the measurement of different structural parameters to determine the health of a structure. A commonly used definition of structural health monitoring is “SHM is the integration of sensing and possibly also actuation devices to allow the loading and damaging conditions of a structure to be recorded, analysed, localized, and predicted in a way that non-destructive testing (NDT) becomes an integral part of the structure and a material”. From this definition four levels of structural heath monitoring are defined: (1) mechanical and environmental load monitoring, (2) identification and location of damage, (3) damage quantification, and (4) prognosis of residual life. The paper will explore how advanced signal processing techniques can drive the development of multi-parameter sensing with fibre optics, and can lead to the goal of integrated fibre optic sensing system for structural health monitoring applications.