Theoretical Analysis And Signal Processing Experiments Of The Evanescent Wave-based Optical Fiber Biosensors

With the advantages such as simple structure, small volume, ease to make, high cost-performance and remote analysis, optical fiber biosensors have been widely applied in clinical diagnostic, environmental protection and food service industry. They also have been paid more attention and have very high value in the military field such as military medicine and biological toxicant detection,Based on the study of the basic operating principle and structure of the evanescent wave-based optical fiber biosensors, an optical fiber biosensor with fiber bundle was developed. Theoretical analysis and signal processing experiments were researched then.The evanescent wave-based optical fiber biosensor uses the evanescent wave which is produced when light propagates in the fiber probe to excite the fluorescence signal. The performance of the probe has an important effect on the performance of the biosensor. Therefore, it is critical for advancing the detection sensitivity of the biosensor to design and optimize the structure of the probe to improve the excitation and collection efficiency. In this thesis, finite-difference time-domain (FDTD) method was used to analyze the field distribution in the fiber probe.In order to solve the problem of weak fluorescence, the signal modulation circuit and signal demodulation program were designed. The laser source was modulated by the modulation circuit, so that the fluorescence signal was modulated. The fluorescence signal collected by probe was detected, acquired by the computer, and then demodulated by the signal demodulation program. The amplitude of the signal identified the concentration of the biology material.Experiments were carried on after finishing the separate parts. The experiment system was improved in the process of experiments. Problems in the current system were analyzed and several factors that may have effects on the detection sensitivity and stability of the biosensor were discussed on the basis of numbers of experiments. Some methods that may improve the sensitivity were put forward.