High-sensitivity temperature sensor based on a compact etched assembled LPFG in a SiO₂-PDMS hybrid waveguide

In this Letter, we propose an ultra-sensitive, compact temperature sensor based on an etched assembled long-period fiber grating (EA-LPFG) redefined by a SiO₂-PDMS hybrid waveguide. This structure is fabricated by periodically splicing SMF and NCF segments, with the entire fiber skeleton subsequently etched to 30 µm to trigger a full-interface evanescent leakage regime in PDMS for enhancing the temperature sensitivity. Experimental results show that the structure achieves the temperature sensitivity of -1.00 nm/°C within a compact sensing length of only 2.6 mm. This work not only provides a high-performance tool for temperature sensing but also offers insights into the modal evolution of hybrid-waveguide-based photonic devices.