Acoustic-wave-mode separation using a distributed Bragg grating sensor

Abstract

This paper reports on the measurement and modal decomposition of structural plate wavesusing a single optical fibre sensor comprising an array of uniformly distributedBragg gratings. Following a brief description of the design and fabrication of thesensor, numerical and experimental work is shown to demonstrate the fidelity ofdynamic strain measurements furnished by the sensor at frequencies in excess of200 kHz. The capacity of the sensor to provide a spatially resolved acoustic measurementrepresents an important advancement over conventional piezoelectric sensors as it allows forthe decomposition of an elastic wave field into its constituent modes. This provides apotentially powerful diagnostic framework for structural health monitoring using guidedwaves. Experimental work on a metallic plate is presented to demonstrate the use ofwave-mode conversion as a basis for the detection of structural damage, and itsinsensitivity to environmental effects.