Development and experimental investigations of extrinsic Fabry–Pérot interferometric sensor-bonding techniques for strain measurement in concrete and metallic structures

As the area of structurally bonded/ embedded optical fibre sensors is evolving rapidly, it is important to reduce/eliminate the sensitivity of various leads. The Extrinsic Fabry-Perot interferometric (EFPI) sensor offers the advantage of simple construction, single-ended operation, high resolution and accuracy, as well as low cost. Compared to conventional strain gauges, it offers the unique ability to be suspended within the matrix portion of the composite system and could provide a viable alternative for assessment of internal strain state of structures. Operation of an EFPI basically depends on an air cavity working as a low finesse two-beam Fabry-Perot interferometer.