Core-cladding mode resonances of long period fiber grating in concentration sensor

Abstract

Long period fiber grating (LPFG) is photoinduced fiber device that facilitates the coupling of core mode to different cladding modes resulting into series of transmission dips in the transmission spectrum. Here we present LPFG chemical sensor to determine the concentration of Manganese in water at ppm level. We fabricated LPFG of period 600µm in single mode communication fiber using 12W carbon dioxide laser applying point by point method. The fabricated LPFG is directly used as chemical sensor since cladding modes coupled to core mode directly come in contact with surrounding chemicals. Concentration of manganese in our collected sample is found to be 0.0329ppm. The result is verified with sophisticated Atomic Absorption Spectrometer (AAS).