Fabry–Perot interference optical fiber biosensor based on the ECF for label-free DNA detection

A fiber-optic biosensor based on self-reference parallel Fabry-Perot interference (FPI) is proposed for label-free DNA detection. The parallel FPI is formed by fusing a section of exposed core fiber (ECF) in SMF and MMF. Adopting the air cavity of the ECF as a reference, a self-reference differential phase demodulation technique is designed to improve the stability and resolution of the demodulation system. By functionalizing the fiber surface, the sensor can efficiently capture complementary DNA (cDNA). In addition, the specific selection performance of the sensor is explored using non-complementary DNA (N-cDNA). The experimental results show that the sensor exhibits a good linear response in the concentration range of 1 to 5 µM, and the sensitivity reaches 5.53°/µM. The detection concentration can be as low as 1 µM. The proposed fiber-optic DNA biosensor has good sensitivity and selectivity and has broad prospects in the fields of biomedical diagnostics, environmental monitoring, and food safety detection.