High-sensitivity PCF-SPR sensor for simultaneous and independent monitoring of humidity and temperature

Abstract Existing devices often suffer from cross-sensitivity, complex structures, or low sensitivity when monitoring temperature and relative humidity (RH) simultaneously. To address these critical challenges, we proposed a dual-side polished photonic crystal fiber (PCF) sensor with polyvinyl alcohol (PVA) and polydimethylsiloxane (PDMS) as selective sensitive materials. Silver films deposited on the two polished surfaces of the PCF efficiently excite surface plasmon resonance (SPR), while a TiO 2 modulation layer was introduced to shift the SPR peak of the temperature-sensing channel to the near-infrared region-enabling complete spectral separation of the two sensing channels. The Ag/PVA composite film on one side realizes RH detection, and the Ag/TiO 2 /PDMS stack on the other side achieves temperature measurement. The sensor reliably detects temperature (10–50 ℃) and RH (60%–100% RH) within the wavelength range of 500–1350 nm, with average sensitivities of −7.875 nm ℃ −1 and −7.475 nm/%RH, respectively. By monitoring shifts in resonance wavelengths and core mode loss spectra, the sensor achieves interference-free simultaneous measurement of temperature and RH, offering a solution for environmental monitoring in vegetable greenhouses. This work provides a novel design paradigm for high-performance dual-parameter optical fiber sensors, advancing their practical application potential.