VOCs Detection Based on Evanescent Wave Coupling of Dye-Coated Optical Fiber

We propose a design for a highly sensitive volatile organic compounds (VOCs) sensor based on evanescent wave coupling of a side-polished optical fiber. The surface of the side-polished optical fiber coupled with a coated solvatochromic dye has charge-transfer (CT) properties. In the proposed model, the application of these optical properties and the novel solvatochromic dye helped overcome problems caused by limited sensitivity, selectivity, and dynamic range that are encountered in typical gas sensors. The different polarities of the VOCs cause changes in the effective refractive index of the sensing membrane owing to CT properties. This can lead to a change in the resonance wavelength of the side-polished optical fiber. To ascertain the effectiveness of the sensor, five VOCs dimethylamine, acetic acid, toluene, benzene, and ethanol were tested, and the enhance in sensitivity was analyzed for varying concentrations. According to the results, the proposed gas sensor showed high sensitivity and resolution.