Investigation Of High Sensitivity Optical Refractive Index Sensing System

Optical sensing technology is along with the development of the optical communication technology, and gradually become an important symbol of a national informatization level. Optical sensor with the significant advantages of high sensitivity, corrosion resistance, resistance to electromagnetic interference, and small transmission loss, cause more and more people's concern, and has been widely used in environmental monitoring, smart power grids, and biological sensors. At present, with the further development of optical demodulation technology, optical sensing technology has been more and more mature, many sensors have been commercialized. However, in order to improve the performance and function of optical sensing, people didn't stop research of optical sensors, optical sensing with new structure or new sensing mechanism appear constantly. In this thesis, we mainly discuss some of the work during the master graduate, including building an optical sensing system based on Surface plasmon resonance(SPR), and designing an optical fiber sensor based on Bent Fiber, finally doing the simulation and experiment to the two kinds of sensors, The main contents are as follows:(1) Because of the advantages of high sensitivity, less need to sample weight, the samples do not need to be marked, SPR technique soon be attention by domestic and foreign research institutions.In this paper, we are starting from the basic theory, and deducing condition of SPR phenomenon, then according to the condition, we wrote a program to determine the parameters and materials of the apparatus, finally, the SPR instrument was been designed from two aspects of hardware and software respectively:with prism of Kretchmann structure as the core, we chose laser, detector, the turntable and other facilities, and controlled them through the software in the computer according to our requirements. Finally we were evaluated for completing system:under long hours work, the stability of the system has reached the requirement of us, and when we set the Angle resolution as 0.00375 °, the refractive index and resonance Angle have very good linear characteristic from the analysis of the different refractive index salt solution, the sensitivity of measurement is 1.935×10-5RIU. But in order to get more high sensitivity, the system must be improved.(2) According to the existing structure of bent fiber sensors, we analyzed the deficiencies and limitations of them, and then we have designed a kind of bent fiber sensor based on wavelength modulation. We do the detailed elaboration of the principle and preparation method of the structure, and then do the experimental study on the refractive index characteristic and temperature characteristic. The results show that when the temperature increase from 23 to 33 degrees Celsius(?), two temperature sensitivity of resonance peaks are-280pm/? and-460pm/? respectively; However, when the temperature is lower than 23 ?, the tesponse to the temperature is very low, as the change of temperature, the resonance peaks wavelength had no obvious change. So the fiber refractive index sensors is more suitable for measure below 23 ?. And the refractive index sensitivity can be achieved respectively 147.602 nm/RIU and 125.459 nm/RIU.