A High-sensitivity strain sensor based on an Unsymmetrical air-microbubble Fabry-Pérot interferometer with an ultrathin wall

A high-sensitivity, low-cost, ultrathin microbubble structure based on an Unsymmetrical air-microbubble Fabry-Pérot interferometer (UAFPI) is proposed. The UAFPI, which has an ultrathin wall of ~6 μm, is constructed by splicing chemically-etched erbium-doped fiber (EDF) to form an air microbubble and applying a taper to one side of the air microbubble. Compared with the air-microbubble Fabry-Pérot interferometer (AFPI), the UAFPI has a high strain sensitivity of 10.15 pm/με, which is approximately three times higher than that of the AFPI, and a low-temperature sensitivity of 2.4 pm/°C in the range of 25–80 °C. The proposed sensor has several benefits, including high strain sensitivity, low-temperature sensitivity, a simple fabrication process, and low cost. Therefore, such a UAFPI-based strain sensor has broad prospects for mass production and practical applications.