Magnesium ion sensor based on single mode-multimode-single with multi-walled carbon nanotubes

A Single-mode multimode single-mode (SMS) fiber structure coated with MWCNTs is proposed and demonstrated for the detection of magnesium ion. The SMS fiber has a length of 30 mm multimode fiber and was fabricated by connecting two optical fiber single-mode and multimode fiber. As the magnesium concentration increases from 0% to 5%, the output power of the SMS fiber structure decreases linearly with sensitivity and resolution of 3.0261 dBm/% and 0.0379 % respectively, for the SMS fiber structure coating with MWCNTs. MWCNTs as magnesium ion sensors will change the refractive index of fiber as the magnesium ion concentration changes due to the optical properties of adsorption. Hence, the SMS fiber structure coating with MWCNTs is more sensitive than the one without coating for magnesium concentration detection.