PDMS-sensitized MZI fiber optic temperature sensor based on TCF-NCF-TCF structure

• An MZI fiber optic temperature sensor was designed with a new structure of TCF-NCF-TCF (thin-core optical fiber, abbreviated to TCF; and no-core optical fiber, abbreviated to TNT) • The fiber optic sensor has been sensitized with PDMS, a material with high thermo-optical coefficient and thermal expansion coefficient, which increases the sensitivity from 57.14 pm/°C to 130 pm/°C. • The sensor exhibits high sensitivity and accuracy in temperature sensing, which has good stability in the range of 50 °C to 80 °C. • The MZI in this paper is simple to manufacture, low cost and easy to produce. It has great advantages for forming large-scale industrial production. A novel fiber optic sensor based on the Mach-Zender interference (MZI) principle and sensitized with polydimethylsiloxane (PDMS) is proposed. This sensor is primarily a sandwich structure with TCF-NCF-TCF (thin-core optical fiber, abbreviated to TCF; and no-core optical fiber, abbreviated to TNT) fused together sequentially, and its overall length is 3 cm. The TNT structure can effectively excite the cladding mode due to the fiber-core mismatch, which produces a significant interference spectrum. Because no-core optical fibers lack a core and cladding structure, they are equivalent to direct contact between the optical waveguide and the external environment, which is extremely sensitive to the variations in the external environment. The experimental results show the highest temperature sensitivity of 57.14 pm/°C ranges from 45 °C to 80 °C. PDMS, a material with high thermo-optical and thermal expansion coefficients, is coated on the surface of the fiber optic sensing zone. And the temperature sensitivity is effectively improved up to 130 pm/°C. Due to the small shape, compact structure, easy production, and steady mechanical strength, the sensor offers significant promise for temperature sensing applications.