| Sensors utilizing optical fibers are being increasingly exploited in industrial, clinical, and military applications. For the purpose of the optimization design of fiber-optic biosensors, the signal analysis and the optimization design of pivotal components are deeply studied in the thesis.Firstly, by using the theory of the radiation of dipoles placed within a multilayer system and ray analysis of multimode optical waveguides, the analysis models of fluorescence signal are presented. With detailed description of the principles of fluorescence immunoassays fiber-optic biosensors, the multilayer system used for analysis of fluorescence signal is proposed. Based on the theory of the radiation of dipoles placed within multilayer system, the original power distributions of fluorescence emission together with the coupling efficiency of the fiber probe are derived. By using the ray analysis of multimode optical waveguides, theoretical models, such as the normalized power distributions of the fluorescence in the fiber probe, the transmission efficiency of the fiber probe, the normalized output fluorescence power distributions of the fiber probe, the collection efficiency of the fiber probe, the effective collection efficiency of the fiber probe, the estimate output fluorescence power of the fiber probe and the detected power of the system are presented. The theory provided above is useful for the optimization design of fluorescence immunoassays fiber-optic biosensors.Secondly, a new connector is designed and manufactured. In order to keep away the disturbance to the detection of the constructed evanescent wave-based optical fiber biosensor from the connector, some configurations of the biosensors are analyzed. Then the newly designed connector together with its transformation matrix is proposed. On the purpose of achieving the best usage of the fluorescence signal and maximizing the interposition-avulsion tolerances of the fiber probe, the method for choosing pivotal components of the new connector together with its critical encapsulation parameters is provided. All the finished work mentioned above is meaningful to construct a more efficient and stable system.Thirdly, the method for the optimization design of the fiber probe is offered. By using the analysis models constructed before, the fluorescence signal of the fiber-optic biosensors employing step-etched and the tapered fiber probes are analyzed respectively, which leads to the following conclusions: the power of the fluorescence signal are mostly transmitted in the form of tunneling rays; power distributions of the fluorescence signal exhibits considerable anisotropy; behavior of the system is greatly depending on the structure of the fiber probe, the numerical aperture of the excitation laser and that of the detecting system. Based on the analysis mentioned above, two methods, which are named as passive-method and initiative-method, are presented for the use of the optimization design of the fluorescence immunoassays fiber-optic biosensors.Finally, the fluorescence immunoassays fiber-optic biosensor is constructed with the newly designed connector. Fiber probes are optimized by using the passive-method and then series of fiber probes with different structures are manufactured with the self-designed device which is based on the serial port. Power supply is carefully improved to avoid damages to the laser-diode. By using immediate immunoassays, some experiment is carefully researched, which suggests that the experiment results consist with theory model very well. What's more, after the immunoreaction, a considerable change of the detected value is observed, with the signal-to-noise ratio about 50.9 achieved, which is 10～22 times as that of the system constructed heretofore. In addition, photo-bleach is studied by analyzing the data sampled continually within a long term. Then the gain and loss between different detecting method is discussed. Finishing the work above, more system experiment would be done in the future. |
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