Research Of Demodulation And Packaging Tecknics On Fiber Grating Sensors

Fiber grating is a novel passive photon device which completely altered the traditional concept of sensing. Sensors using FBG as the sensing component have many advantages including light weight, small size, anti electromagnetism interference, convenience in fiber connecting, wavelength absolute coding etc. Multiple point detection of materials (temperature, strain etc.) can also be achieved by connecting several sensors into a net using variety of multiplex techniques and embedding it into or sticking on the surface of the material or structure. The so called distributed sensing is a unique technique of Fiber Grating Sensor (FGS). These particular merits make FGS play a more and more important part in the sensing field. Now, the reported FGS can measure many physical parameters including temperature, strain, stress, displacement, pressure, torsional angle, twist moment (moment of torque), accelerated velocity, current, voltage, magnetic field, frequency, density, coefficient of thermal expansion, trembling etc. Some of the fiber grating sensing systems have been put into practical use.The dissertation primarily researches on FBG, theoretically and experimentally analyses its sensing principle, high speed demodulation as well as packaging. The main content is:1. Generally introducing the invention, development and present state of fiber grating sensing technique. The three basic theoretically analytical methods. Analyzing the principal theory of FGS. Summarizing and comparing all kinds of packaging, demodulation and multiplexing techniques of fiber gratings.2. Presenting many constructing methods of fiber grating temperature and strain sensors. Formulating the packaging principle and structures in detail. And putting forward the data analysis method of"subtracting bigger number"which effectively increase analysis precision. The design of temperature sensor realizes bare fiber temperature characters and strain insensitivity of capsulated components in the range of 30℃~85℃, which guarantees their high stability and repeatability. Analyzing and experimentally verifying the strain transducing characteristics of strain sensor. Experiments tell that strain sensor capsulated by thin sheet metal can effectively transduce strain under certain mechanical robust with strain transducing efficiency of 97.8%, sensitivity of 83.34με/kg, precision of 1.64με. These two kinds of sensors have the advantages of anti electromagnetic interference, small size, light weight and high mechanical robust etc.3. On the basis of analyzing theoretically the high birefringence fiber loop mirror, temperature characteristics are studied and transduction is realized. Utilizing its...