LAUSR

A Mach–Zehnder interferometric sensor with a dual-core photonic crystal fiber structure with defect cores is designed, which is used to detect the content of crude refined or refined cottonseed oil in olive oil in terahertz band. The radius of the central air holes and the defect cores in the dual-core fiber structure are optimized, so that the interval between adjacent transmission peaks of mixed oil doped with different contents of crude refined or refined cottonseed oil is as large as possible, the transmission spectrum width is as small as possible, and the transmission depth is as deep as possible. The linear relationship between the resonance frequency and the content of doped cottonseed oil is obtained, and the average sensitivities are 5.976 × 10−4 THz/% and 2.212 × 10−4 THz/%.