Simultaneous measurement of temperature and RI based on a novel peanut-shaped OFS

We propose and demonstrate a compact optical fiber sensor (OFS) based on a novel peanut-shaped structure. Mach-Zehnder interferometer (MZI) and surface plasmon resonance (SPR) are introduced by coating the sensing area with a gold film. The use of optical fiber precision cutting technology ensures the integrity of the core, which reduces the loss of the transmitted light compared to other similar structures. MZI is used for external temperature sensing, the results show that when the temperature range is 25-60°C, the temperature sensitivity is calculated as -43.6 pm/°C. SPR is used for external refractive index (RI) sensing, the results show that when the RI range is 1.333-1.393, the RI sensitivity is calculated as 2250.7 nm/RIU. These two channels are independent of each other, which solves the problem of cross-sensitivity. Finally, the feasibility of the sensor is verified by measuring the thermo-optical coefficient of the anhydrous ethanol. The measured value is in good agreement with the theoretical value, and the error is about 2.31%.