Temperature and Curvature Microfiber Mach-Zehnder Interferometer Sensor Based on Double Peanut-Shaped Structures and Tapered Coreless Fiber

We propose and demonstrate a new temperature and curvature sensor based on double peanut-shaped structures and tapered coreless fiber (CLF) using microfiber Mach-Zehnder interferometer (MMZI) technology. The peanut structure is comprised of single-mode fiber (SMF) and CLF, and fused sphere in each fiber end to create a high sensing performance. By combining the characteristics of the peanut-shaped structure and microfiber with a high evanescent field, this sensor can excite more high-order modes and obtain high-performance measurements. The experimental results demonstrate that the maximum intensity temperature sensitivity is 0.33 dB/°C when the temperature changes from 45 °C to 60 °C with a taper length of 5.5 mm. As far as we have known, it is the highest temperature sensitivity in the peanut-shaped structure with intensity modulation. Additionally, the sensor has an intensity curvature sensitivity reaches up to 16.56 dB/
$\text{m}^{-1}$
when the curvature varies from 0
$\text{m}^{-1}$
to 0.23264
$\text{m}^{-1}$
. These results highlight that the sensor has excellent curvature and temperature sensitivity, making it ideal for application in health monitoring, environmental monitoring, and medical applications.