Optical Fluorescence and Its application to blood glucose monitorPan Yongfeng(Wuhan University of Technology, Wuhan, China, xhyzjiji126.com)AbstractBlood glucose monitor system is designed with the core of photonic crystal fiber (PCF) and technology of small invasive photoelectric. According to the principle that different blood glucose concentration absorbs different light, optical modulation is controlled by MSP430 Light is emited to the blood samples through transmission of three probe fiberoptic sensor. The reflected light is inputed to MSP430 after photoelectric conversion. Blood glucose concentration is calculated after A/D conversion. The system has characteristics of easyoperation, low energy.Keywords photonic crystal fiber(PCF); smallinvasive; blood glucoseI. I NTRODUCTIONith the rapid development of science and technology, optical fiber has increasingly expanded in the medical, communications, W electronics and electricity, and other fields. It is becoming the basis of promising materials. In practice, however, the optical fiber, as a transmission medium to wire will inevitably need to be bended. When traditional optical fibers are of bending, bending loss will affect the signal transmission properties and sensitivity. Photonic crystal fiber (photonic crystal fiber, PCF) is a new type of optical fiber, which is formed by a single medium, clad in two-dimensional photonic crystals structure. It is different from the traditional optical fiber because of its small bending loss, Optical fiber features stable etc. Based on this, the blood glucose monitor system use PCF as optical waveguide materials and designe the three probe beam PCF sensor to monitor blood glucose. The system has high precision, low cost, good portability.II.D ESIGN PRINCIPLESA. Measuring principleThe glucose in the blood will be oxidated and finally turn into delta-gluconolactone by GOD, when the blood sample drops into the test paper which contains oxidase for the oxidation of glucose. This substance reacts with peroxidase in the reagent, and thenwill generatea light-absorbingmaterial. Weplace the paper in the reflectiveintensity modulation typefiber opticsensor in theoptical path, as shown in figure 1. The whole sensor system includes a light source, optical fiber, optical fiber and optical detectors.The light emitted by light source reach the surface of blood sample through the filter and transmitting fiber. Due to material suctionlight modulation,reflected light withblood sugar informationwillbe received by receiving optical fiber,finallyturned intoelectrical signals by the photoelectric receiver converts. When the power of light source and optical fiber probe and the distancebetween the reflective surfaces remain unchanged, the receiving optical fiber receives a certain wavelength of light intensity and thewavelength of incident light intensity is the ratio of the corresponding relationship with blood sugar levels. According to the lightintensity of the signal, the blood glucose concentration can be calculated. But the main drawback of this kind of optical fiber sensoris measurement error caused by light source, optical power changes when light excitation is not stable. In addition, the different reflectivity of the reflector surface and light transmission loss in the optical fiber should also cause measurement error. Therefore, to put forward three probe fiber optic sensor compensation measuring method can eliminate the influence of all kinds of unstable factors in the measuring environment.Figure 1. Reflective intensity modulation type fiber optic sensorB. Three probe compensating optical fiber bundle sensors measurement principleTraditional reflective intensity modulation type fiber optic sensor using a single optical fiber transmitting and receiving the light energy is very weak. Moreover, in the design of wiring, because of the warped shape change the geometry of the symmetry of thefiber and the relative refractive index of fiber core and cladding, which affect the lateral distribution of the optical fiber mode field, and destroy the total reflection of light waves along the optical fiber transmission conditions, lead to light leaked to the packet layer and outer layer medium. Therefore, this design is composed of three probe of optical fiber sensor including PCF which use to send and receive light and the additional reference light path, as shown in figure 2.Figure 2. Three probe optical fiber bundle sensorsOrdinary single mode optical fiber loss theory of improvements can be applied to PCF, gaussian beams transmit along the optical fiber, the relationship between light intensity and bend loss coefficient and length isP(z) P(0)exp( az)(1)a in the formula is bend loss coefficient, andin the formula,2sin