Miniaturised gap sensor using fibre optic Fabry-Pérot interferometry for structural health monitoring
Tamer Y. Cosgun, Adrian Dzipalski, Calum A. Ross, Robert R. Thomson, Matthew Kingston, S.J. Brooks, William N. MacPherson
Abstract
A miniaturised structural health monitoring device has been developed capable of measuring the absolute distance between close parallel surfaces using Fabry-Pérot interferometry with nm-scale sensitivity. This is achieved by fabricating turning mirrors on two opposite cores of a multi-core fibre to produce a probe with dimensions limited only be the fibre diameter. Two fabrication processes have been investigated: Focused ion beam milling, which has resulted in a sensor measurement accuracy, sensitivity and range of ±0.056 µm, ±0.006 µm and ∼16000 µm respectively; and ultrafast laser assisted etching of the cleaved fibre end, where a sensor measurement accuracy, sensitivity and range of ±0.065 µm, ±0.006 µm and ∼7500 µm have been demonstrated.