Theoretical Simulation Of Biomedical Fiber Optic Sensor Based On SPR Effect

As optical fiber sensors are widely used in various fields of production and life,the development of biomedicine has also put forward new requirements on the performance of optical fiber sensors.Conventional fiber-optic sensors have such problems as high material loss and low measurement accuracy.Therefore,in order to meet the sensitivity requirements of biomedical detection and clinical experimental needs,the researches on detection of optical fiber sensors to determined whether biological cells are cancerous or not become more and more important.And these optical fiber sensors are usually enhanced with the surface covered with gold nanoparticles,which exhibit the surface plasmon resonance effect and thus effectively increase the sensitivity of the optical fiber sensors.However,most of the current researches were confined to experimental works,and the different shapes and sizes of optical fiber sensors need to be fabricated first before subsequent experimental measurements can be performed.The main differences of these fiber sensors include the diameter of the internal core,the geometry and bending diameter of the probe,and the size of the gold nanoparticles covering the probe surface.However,this method is actually inefficient and wasteful.On the other hand,the relevant theoretical studies cannot reasonably model and simulate the millimeter-sized optical fiber sensors and the nanometer-sized gold nanoparticles on the probe surface.Therefore,fully theoretical simulation analysis on the realistic millimeter-sized optical fiber sensors covered with gold nanoparticles are of special scientific significance and practical importance.In this work,the optical fiber sensor with the U-shaped probe shape covered with gold nanoparticles,which is commonly used in biomedical detection,is investigated in a fully theoretical simulation,and the absorbance and sensitivity of a bare U-shaped fiber optic sensor,surface plasmon resonance effect and a U-shaped fiber optic sensor covered with gold nanoparticles are focused on.In this study,an equivalent method and a theoretical equation are innovatively proposed for the first time by combining the geometric optical model and the fluctuating optical model,and its self-consistency is illustrated and its rationality is verified.In this study,the outgoing light intensity and transmittance of the relevant fiber-optic sensor model are obtained by solving the set of partial differential equations in multi-physics fields by the finite element method,and then the absorbance is calculated using the Lambert-Bier law,so that the refractive index sensitivity of the Ushaped fiber-optic sensor can be calculated based on the rate of change of absorbance with the refractive index of the external solution.This refractive index sensitivity is an important parameter to determine whether a normal cell is cancerous or not,i.e.,the greater the refractive index sensitivity,the higher detection accuracy for the possibility of cell cancer.Present full theoretical simulation may not only avoid the waste caused by the fabrication of optical fibers in experiments,but also calculate the probe shapes that cannot be fabricated experimentally or are difficult to fabricate,and also provide useful information for experimental measurements.