Fiber-optic Evanescent Wave Biosensor System

Evanescent wave-based optical fiber biosensors is an important branch of biosensor, it has 30 years of development history. Because of its unique advantages, it has great potential for application in terms of water quality monitoring, food hygiene inspection, detection of biological warfare agents. In this paper detection and processing systems is build, based on the study of the principle and the basic structure of the Evanescent wave-based optical fiber biosensor.Because of the weak fluorescence signal from probe which accompanying with the strong laser signal and system noise, so how to extract a weak fluorescent signal from the strong noise is critical to the whole system. In order to solve the problem, we work in two aspects. In on hand, the probe structure is design by using geometrical optics method, through a combination of Evanescent wave theory and pattern matching theory. It can improve the efficiency of the probe. On the other hand, because of the more discrete components and high system noise in traditional evanescent wave-based optical fiber biosensors, we build a platform based on FPGA+LabVIEW. An on-chip system is build, the A/D sampling, signal generator DDS and UART interface are control by Nios II soft-core microprocessor.The system that including data acquisition, data transmission, modulation signal integrated, greatly reduced the number of discrete components system, improve the system integration and SNR. An application softwave providing signal detection by digital lock-in amplifier, data communication with FPGA and Interface display is builded by using LabVIEW.Finally, the experiment is carried on after building the Evanescent wave-based optical fiber biosensors. The experimental results show that the system sensitivity reach to 1nmol/L when detect the Cy5 solution. This biosensors can use in the actual detection of biological material in high precision application requirements. This system has long-term stability, small volume and simple structure which make it suitable for filedwork.