Fiber-optic temperature sensor coated with PDMS thermo-gel film based on etched SMEDS structure

• A temperature sensor based on an etched SMEDS structure is proposed. • The PDMS Thermo-gel film coating enhances sensor temperature sensitivity. • Experimental results show a temperature sensitivity of 0.113 nm/°C, with a wavelength shift linear to temperature change. • The SMEDS sensor has a compact design and is simple to manufacture, making it widely used in the temperature sensing industry. In this work, we propose a fiber-optic temperature sensor based on single-mode fiber (SMF) −multi-mode fiber (MMF)-etched dispersion compensating fiber (DCF)-single-mode fiber SMF (SMEDS) fiber structure coated polydimethylsiloxane (PDMS) Thermo-gel film with experimental validation. A single-mode fiber is gradually fused with a section of MMF and DCF in this sensor structure. The central region of the DCF was then etched with hydrofluoric acid (HF) to create a strong evanescent field. Finally, the temperature sensitivity of the sensor was significantly improved by coating the sensor area with PDMS thermos-gel material. The PDMS thermos-gel film material serves as a simple and efficient encapsulation layer that not only protects the sensor’s microstructure from damage but also greatly improves the reliability and durability of the sensor structure. The experimental results show that the sensor has a temperature sensitivity of 0.113 nm/°C over a wide temperature range of 25–95 °C. When compared to fiber optic sensors without PDMS coating, the temperature sensitivity is 2.9 times higher. The small structural design of the SMEDS sensor, along with its easy production method, high-cost efficiency, and stable and reliable mechanical strength, suggests that it has a wide range of significant applications in the temperature sensing industry.