Fuel adulteration detection sensor using sensitivity-optimized etched long-period fiber grating

The adulteration of cheap solvents in petrol for financial benefit is not legally allowed because it generates harmful air pollutants in the emission. In the present work, a long-period fiber grating (LPFG)-based sensor is proposed to quantify the adulteration of kerosene oil in petrol. The vector coupled-mode theory has been implemented on a 3-layer fiber geometry-based mathematical approach to estimate the refractive index (RI) sensitivity. For quantitative analysis, the RI sensitivities of LPFG-based cladding modes ( \({{\text{HE}}}_{15}-{{\text{HE}}}_{17})\) ${\text{HE}}_{15}-{\text{HE}}_{17})$ have been analyzed while considering important LPFG parameters i.e., optical mode order grating period, and cladding radius. The dependency of LPFG response on aforesaid parameters leads to their critical selection for designing a highly sensitive adulteration sensor. It is apparent that the higher-ordered ( \({{\text{HE}}}_{17})\) ${\text{HE}}_{17})$ cladding mode has achieved the highest RI sensitivity of 3071.6 nm/RIU (nanometer per refractive index unit) at cladding radius 32.5 μm and grating period 330 μm. It derives the LPFG sensor’s resolution to 0.676 nm for per percentage (nm/%) adulteration of kerosene in petrol. With this resolution, the kerosene adulteration of less than 10% in petrol can be easily detected. Therefore, this study envisages a design to fabricate LPFG sensors for adulteration detection with utmost precision at fuel filling stations.