Vernier-Effect-Enhanced Fabry-Pérot Interferometric Optical Fiber Sensor for Highly Selective Copper-Ion Detection
A cascaded single–mode–multimode–hollow-core fiber (SMF-MMF-HCF) optical sensor based on Fabry-Pérot interferometer (FPI) is proposed for ultra-sensitive copper ions (Cu(II)) detection. The cascaded structure provides an unfilled-air reference cavity and an air-material hybrid sensing cavity with slightly detuned free...