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Abstract

Brillouin distributed measurement techniques have been extensively
developed for structural health monitoring using fibre optic nerve
systems. The recent advancement in the spatial resolution capabilities
of correlation-based Brillouin distributed technique have reached the
sub-mm regime, making this approach a suitable candidate for monitoring
and characterizing integrated photonic devices. The small dimension
associated with the short length of these devices-on the order of the
cm- and mm-scale-requires high sensitivity detection techniques and
sub-mm spatial resolution. In this paper, we provide an overview of the
different Brillouin sensing techniques in various micro-scale structures
such as photonic crystal fibres, microfibres, and on-chip waveguides. We
show how Brillouin sensing is capable of detecting fine transverse
geometrical features with the sensitivity of a few nm and also extremely
small longitudinal features on the order of a few hundreds of mu m. We
focus on the technique of Brillouin optical correlation domain analysis
(BOCDA), which enables such high spatial resolution for mapping the
opto-acoustic responses of micro-scale waveguides.