An optical fiber humidity sensor with a microfiber knot resonator (MKR) nested U-shaped Mach-Zehnder (MZ) interferometer based on the Vernier effect is proposed. While the reference arm is protecte…
A novel optical sensor for ammonia concentration in water is demonstrated using up-conversion (UC) fluorescence intensity ratio (FIR). The sensor element consists of (i) an Er 3+ -Yb 3+ co-doped te…