Design Of SPR-type Plastic Optical Fiber Refractive Index Detection System Based On CCD

Surface Plasmon Resonance(SPR) is a kind of optical phenomenon,it has been diffusely used in environmental quality monitoring and biomedical research.The optical fiber SPR sensor has become a hot spot of research in recent years due to its small specifications,high precision,fast response speed,strong anti-electromagnetic interference capability,and sensitivity to environmental change.Thus,the D-type plastic optical fiber SPR sensor is designed to detect the change of refractive index.The main tasks are:Firstly,the principle,basic performance and SPR effect of the fiber refractive index sensor system is analyzed.The design choice of optical systems is based on the optical path structure of a flat field holographic concave grating.After using ZEMAX software to determine the required optical component parameters,complete the modeling optimization.A surface Plasmon resonance sensor was made by using magnetron sputtering technology and gold film of 50 nm thickness was coated on the polished fiber structure,which was used to detect the change of refractive index.The refractive index detection system is designed and built,which takes FPGA as the core control chip and CCD as photodetector.According to the function,the whole circuit system is divided into CCD drive,AD conversion,FPGA control and USB communication module.A TCD1304 DG linear array CCD detector having a response wavelength range of200 nm to 1100 nm is selected for photoelectric conversion,the resulting signal is converted into a digital signal by AD7667,the "soft" FIFO is used for rate adaptation,connect the printed circuit board and the host computer through the USB communication interface to complete the data transmission.Among them,the FPGA is used to complete program control for each module,and the upper computer designed by Lab VIEW is used to complete the graphical display of data.After the system configuration is completed,the wavelength is calibrated by fitting method,and the binary matching of "pixel position wavelength" is completed.Finally,water and Na Cl solution are selected for index detection.The experimental results proved that the test system has steady property within the scope of 400-800 nm,and can precisely measure the wavelength change.The optical grating has a resolution ratio of 2nm near 660 nm,which meets the design requirements and sensitivity requirements.Therefore,it is possible to detect the refractive index of different solutions according to the designed D-type plastic optical fiber SPR sensor with a sensitivity of 1213nm/RIU and the designed test system.