Simple capillary based extrinsic Fabry–Perot interferometer for strain sensing

A simple capillary-based extrinsic Fabry–Perot structure is presented and fabricated, using the manual welding method with the strain sensing characteristics investigated in detail. Strain sensitivities of 4.2, 2.8, and 2.4 pm/με are obtained experimentally with the interferometer length around 50 μ