Temperature-Independent Ultrasensitive Fabry–Perot All-Fiber Strain Sensor Based on a Bubble-Expanded Microcavity

A fiber Fabry–Perot interferometer (FPI) based on a bubble-expanded microcavity is investigated in this paper. Due to the expanded bubble microcavity, the FPI exhibits high strain sensitivity of 30.66
$\hbox{pm}/\mu\varepsilon$
. To the best of our knowledge, such strain sensitivity is three to ten times higher than that of the fiber FPIs based on the microcavities previously reported. The strain response of the FPI with different shapes is analyzed, and the experimental results are consistent with the theoretical analysis.