Research On Fiber Optic Surface Plasmon Resonance Technique And Its Application In Real-time Measurement

The refractive index is one of the physical quantities that characterize the optical properties of the medium,and its value has a definite correspondence with the physical and chemical parameters such as temperature and concentration of the medium within a certain range.In the real-time study of substances,the refractive index is often measured in real time,because it is easier to achieve than other physical quantities.Fiber optic surface plasmon resonance technology is a combination of fiber optic sensing technology and surface plasmon resonance（SPR）technology to achieve the measurement of the refractive index of a solution.Fiber optic SPR sensors are label-free,highly sensitive,and can measure in real time.In this paper,the application of plasma technology on the surface of optical fiber in real-time measurement will be studied,taking chemical oscillation reaction as the measured object for real-time measurement.The main research work and achievements are as follows:（1）In this paper,the excitation principle of SPR phenomenon is combined with Maxwell’s electromagnetic waveguide and Fresnel’s multilayer medium reflection theory to derive the intrinsic solution of the electromagnetic wave,thus establishing a theoretical model of a four-layer medium-based optical fiber SPR sensor.Through the analysis of the theoretical model,phase modulation is selected as the signal modulation method for the measurement optical path system in order to improve the measurement resolution of the sensor.（2）Through MATLAB software,the structural parameters of the optical fiber SPR sensor are simulated,the errors caused by the angular drift of the sensor and the influence of the chromium film of the bonding layer on the sensitivity of the sensor are analyzed,the optimization parameters of the optical fiber SPR sensor are determined,and the systematic error of the sensor is analyzed.（3）A transverse Zeeman dual-frequency laser interferometric fiber SPR optical path measurement system was built.Based on the measurement optical path system,the calculation formula of phase responsivity of optical fiber SPR sensor and the refractive index calculation formula of the liquid to be measured are derived.The phase responsivity of different groups of solutions and mixed oscillating solutions was calibrated experimentally,and the corresponding measurement resolution was further obtained.The static refractive index of samples of different concentrations of each group of solutions before participating in the reaction and the dynamic refractive index and its changes when the oscillation reaction occurs after mixing were measured.At the same time,the error of real-time measurement and static measurement is compared,and the measurement results of Abbe refractometer are compared and verified.The experimental results show that the average error of the fiber SPR sensor for real-time measurement is 1.35×10^-4RIU,and the measurement resolution of the magnitude can be achieved 10^-5 during real-time measurement,and the phase responsivity is 1637/RIU.This fiber optic SPR sensor can be used for real-time measurement of refractive index in food processing and drug production processes.