Measuring dynamic strain of structures using a gold-deposited extrinsic Fabry Perot interferometer

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Abstract
In this paper, we present a new type of extrinsic Fabry–Perot interferometer (EFPI) for measurement of dynamic strain. Gold was deposited on the second reflecting surface of the optical fibre in this sensor to increase its reflectivity. Thus, we have termed it a gold-deposited extrinsic Fabry–Perot interferometer (G-EFPI). If a gap between two reflecting surfaces increases, the loss of intensity of the light that passes through the gap increases, causing a subsequent decrease in the output intensity of the sensor. Conversely, if the gap decreases, the amount of loss decreases and the output intensity increases. Therefore, it is possible to determine the variation of the gap size by observing the output intensity of the sensor. Finally, the dynamic strain of a composite specimen was measured successfully using the G-EFPI.