Investigation on low-temperature characteristics of FBG sensors and the technology to enhance sensitivity
The mode of FBG's temperature-sensing is analyzed to and the low temperature performance of FBG is experimental study. Three package technologies can be used for enhancing the sensitivity of FBG under low temperature; the technologies include capillary steel tube package, metallized package and organic polymer package. The results show that the temperature sensitivity of bare FBG under low temperature is 0.00998 nm /°C, the temperature sensitivity of FBG with capillary steel tube package, metallized package and organic polymer package are 0.0213 nm /°C, 0.0283 nm /°C and 0.1376 nm /°C separately, which are 2.02, 3.30, 10.23 times compared with the bare fiber. The temperature sensitivity of FBG sensor under low temperature could be increased effectively by using package technology.
Mathematical model of optimized design of multi-point sensoric measurement with Bragg gratings using wavelength divison multiplex
Fiber Bragg gratings (FBGs) belongs to the single-point optical sensors used in many fields and applications where they often replace a standard sensors. They are easy to multiplex and the wavelength division multiplex is the most widely used method. FBGs in sensory branch are designed for a different Bragg wavelength which gives different measure and sensitivity coefficients. Existing algorithm is based on the determination of left and right boundaries of the measuring channel and the central Bragg wavelength. In this paper is presented the new mathematical model for calculation of Bragg wavelength, sensitivity coefficient and channel width of any FBG in the single step. The model takes into account the following input parameters: wavelength of the optical source, source bandwidth, the type of measured quantity, measuring ranges, width of the FBG reflected spectrum and the guard band between adjacent channels. The mathematical model is verified by using a simulation in software OptiSystem.
Thermal Expansion: Metallic Elements and Alloys
The introductory sections of the work are devoted to the theory of thermal expansion of solids and to methods for the measurement of the linear thermal expansion of solids (X-ray methods, high speed methods, interferometry, push-rod dilatometry, etc.). The bulk of the work is devoted to numerical data on the thermal linear expansion of all the metallic elements, a large number of intermetallics, and a large number of binary alloy systems and multiple alloy systems. A comprehensive bibliography is provided along with an index to the materials examined.