Study Of The Method For Thinned Cladding FBG Glucose Sensing

Compared to conventional electrochemical biosensor, fiber optical biosensors have many advantages, such as anti-corrosion, anti-electric magnetic field interference, small size, low cost, capacity of online testing, etc. As a kind of reflective passive optical component, Fiber Bragg Grating(FBG) which uses resonance wavelength as the characteristic parameter, need not considering the influence of light intensity and polarization in sensing applications, and is easy to fabricate single-ended miniaturization probe, therefore, FBG has become one of the focus areas of fiber optic biosensor in recent years. Owing to the characteristics of high efficiency and specificity in enzyme-catalyzed reaction, enzyme has become one of the most widely used bioactive substances in the study of biosensors.Combined the characteristics of thinned cladding FBG which is sensitive to the refractive index of external environment and Glucose oxidase(GOD) catalytic glucose specificity, a fiber glucose sensing method is proposed in this paper. Using GOD catalytic glucose reaction specificity and refractive index changes before and after the reaction, the detection of glucose concentration was converted to measuring resonance wavelength of thinned cladding FBG. This fiber biosensor based on FBG and GOD have the advantages of simple structure, easiness to build optical path, easier to fabricate sensing probe, etc. The main content of this paper and achievements as follows:(1) Glucose sensing technologies are described, especially the fiber grating glucose sensing technology, their merits and faults, some problems in present researches are analyzed in the study. Based on summarizing and comparing of fiber grating glucose sensing technology, the thinned cladding FBG is chosen as sensing element in this topic research.(2) The sensing properties of thinning cladding FBG is deduced theoretically and analyzed according to the coupled-mode theory and simulated with OptiGrating software, which indicates that FBG is sensitive to the change of ambient medium refractive index when the FBG cladding is thinned to a certain degree.(3) The production process of the sensor in this paper includes: thinned cladding FBG production process, immobilized GOD on the surface of FBG. Comparing two immobilized methods of GOD through experiments, we concluded that immobilized GOD with silane coupling method is more conductive to improve sensor performance.(4) Several experiments are carried out. Results show that the thinned cladding FBG glucose sensing method can realize specificity detection of glucose, and by experiments of sensors with immobilized different concentration of GOD, we found that the measurement range of sensor will increase with the increase of immobilized GOD concentration. Finally, a few ways are proposed to improve sensor performances.