Dual Light Sources Interferometry Measures the Refractive Index to Estimate Ethanol Concentration

High-precision, rapid, non-contact measurement of solution concentrations is crucial for accurate formulation. In this paper, we introduce an ethanol concentration interferometer based on low-coherence interferometry (LCI) technology, utilizing a dual-light source and a microcavity method. The system features a modified Michelson interferometer structure, conducting measurements with both 1310 nm broadband light and 1550 nm narrowband light. It employs a long optical path optical delay line to achieve high linearity in axial scanning (R2=0.9979). Ultimately, this method achieves a measurement accuracy of 1e-3 for the group refractive index of alcohol solutions ranging from 30% to 75%.