Erbium-doped fiber cascaded coreless fiber temperature and curvature sensor based on MZI

This study presents a dual-parameter fiber-optic sensor with record-breaking sensitivity through erbium-doped fiber (EDF)-coreless fiber (CLF) cascaded interferometry. The EDF enables dual modulation, thermal expansion alters the pseudo-Fabry-Pérot (FP) cavity length (phase shift) while photothermal effects induce Mach-Zehnder interferometer (MZI) intensity changes. Temperature affects both FP and MZI, whereas curvature exclusively modulates CLF-induced MZI leakage, achieving decoupled sensing. Experimental results show record sensitivity (0.415 dB/°C for temperature, <i>R</i>²=0.996; -6.469<i>d</i><i>B</i>/<i>m</i>^-1 for curvature, <i>R</i>²=0.993). The all-fiber fused low-cost structure improves temperature resolution by >25<i>%</i> over existing intensity-modulated sensors, enabling industrial monitoring and smart infrastructure applications.