Cu2+ Detecting by Using Optical Fiber Mach-Zehnder Interferometer Coated with CS/PAA

Optical fiber copper (II) ions (Cu2+) sensor based on an optical fiber Mach-Zehnder interferometer (MZI) formed by cascading two micro fibers is proposed and experimentally demonstrated. The MZI is surface-functionized by coating a chitosan/polyacrylic acid multilayer film using a layer-by-layer self-assembly technology. The achieved measurement sensitivity and detection limit are 62.44 dB/mM and 0.0086 mM, respectively, when the copper (II) ions concentration is between 0.005 mMol and 0.1 mMol.