Side-polished Fiber SPR Sensor With Temperature Self-compensation

It is important to continuously monitor the blood glucose level to provide guidance for diagnosis and the therapy.Nowadays,the measuring method based on implantable enzyme electrode sensor is widely used in clinical applications for continuous glucose monitoring.However,the significant drift caused by bioelectricity and the effect of electrochemical reactions under hypoxia reduce the accuracy of the measurement.In order to overcome the two problem,a side-polished fiber surface plasmon resonance(SPR)sensor with temperature self-compensation was proposed in this paper.Traditional fiber SPR sensor shows low sensitivity and the spectrum of it was suspected with temperature.The proposed sensor adopted side-polished structure whose sensing area was a plane,so,the fiber surface modification technique can easily achieve which lay the foundation of sensitivity enhancement.The grating was engraved into fiber sensor which can compensate the SPR spectrum fluctuation caused by temperature changing automatically to enhance the measuring accurate of the sensor.The main work in this paper as follows:(1)The structure design and simulation of proposed sensor.According to the theory study,the whole structure design was proposed in the paper.The mode analysis of COMSOL Multiphysics was selected to simulate the parameters of the side-polished fiber SPR sensor.The optimal parameters including the length of the polished area,the residual cladding thickness,the chrome thickness and the gold thickness were obtained.According to the temperature measuring theory of LPFG,the optimal parameter of LPFG was determined.(2)The fabrication of the sensor.Firstly,the LPFG was engraved into the fiber by CO2 laser.Then,the side-polished structure was achieved by wheeled polish machine.Chrome film and gold film was deposited on the side-polished area by physical vapor deposition technique.The last,the packaging of the senor was achieved.(3)The characteristics of the sensor.The experiment system was established to characterize the sensor.Three experiment was carried out: temperature experiment of LFPG,temperature experiment of SPR,glucose concentration experiment of SPR.The experiment result shows that: The resonance wavelength of LPFG was increase with temperature with linearity of 0.93514.The resonance wavelength of SPR was decrease with temperature with linearity of 0.92646.The resonance wavelength of SPR was increase with glucose concentration with quadratic fitting of 0.94454.The proposed temperature compensation method can compensate the SPR spectrum shift caused by temperature to enhance the measuring accuracy of proposed sensor.