Theoretical Analysis And Optimization Design Of Pivotal Components In The Evanescent Wave-based Optical Fiber Biosensors

The thesis aimed at the applicationg requirement of military field in biological toxicant detection, battle environment inspection and biology counter-terrorism, based on the constructed evanescent wave-based optical fiber biosensor research platform, the basic theory and technology of system were more deeply studied in theoretics and experiment.The paper started in the evanescent wave-based optical fiber biosensor prototype general experiment testing, and obtained lots of experiment datas, hereby, detailed analyzed detecting sensitivity, precision and stability of system. The experiment results show that the detection limit for the labeling concertration of the fiber probe reachs to 0.001μmol/L, which can satisfy the applying requirements of precision in actual analyte detection. Based on this, the paper ananlysed and appraised the capability of experiment prototype, and put forward some plans and projects to improved engineering and practicality.Optical-fiber connector jointed laser fiber, signal fiber and probe, was one of pivotal components in system, its performance directly influences the system detecting sensitivity and stability. The paper studied on connector model based on geometry-optic theory, calculated the coupling efficiencies using overlap-area integral, analysed the background optic-noise of laser end reflect, and obtained the quantitative results. Designed the experiment based on the lab's system, the resuls show that improvement of connector's structure can increase the coupling efficiencies and detecting sensitivity of system, the results between theoretics and experiment were same in principle. Based on the error ananlysis, the thesis suggested optimizing and improving methods of fiber connector structure.The PMT detector in the system have advantage of high gain and low noise, but its large dimension restrict the system miniaturization and portability. Using small volume and high sensitivity photoelectric detector is the approach to engineering and miniaturization. Based on this, the paper gropingly analyzed feasibility of varieties of photoelectric detector applied in optical fiber biosensor. Primarily based on the APD and PIN, theoretically calculated the precision, gain and SNR performance, and taked into account difficulties when the detection cell applied and fabricated actually. From the contrast analysis of PMT, APD and PIN, the thesis discussed the precision of system using different photoelectric detectors, provided theory basis for improving and optimizing photoelectric detection cell in the system. Finally, aimed at system miniaturization, circuit stability and parameter adjust facility, the paper redesigned signal modulation circuit and signal-collection-card interface circuits. Optimizing the performance, compressed PCB area and perfected function.