Fiber Grating Temperature Sensing System Based On DSP

Fiber grating sensing technology has many advantages, such as small in size, multiplexing, electrical insulation, anti-electromagnetic interference, online measurement, remote transmission, etc. Therefore, it is especially suitable for flammable, explosive, space severely restricted, strong electromagnetic interference and other harsh environments. As a result, the optical fiber sensor not only can replace the traditional electrical sensors in most cases but also can be used in the extreme situations. It provides a reliable and new detection method to detect temperature and other parameters. For example, fiber Bragg grating temperature sensing system can be used to monitor temperature inside the power transformer winding.On the basis of analysis of the FBG sensor and demodulation technique both at home and abroad, hardware and software which fiber Bragg grating sensor demodulation requires are designed. The main matters are shown as follows:The basic structure of the fiber, mechanism of Bragg grating and its producing methods are firstly described in this paper. At the same time FBG sensor's basic parameters of the spectral characteristics is analyzed. Then temperature sensing model of FBG is deduced, and finally FBG demodulation technique which is current commonly used is described in detail.The design of circuit and the development of software system are main content of this thesis. Circuit consists of several sections, which are shown as follows:the amplifying circuit of small signal including photoelectric conversion circuit and preamp and filter circuit, which transforms the light signals to electrical signals; AD converting circuit transforms analog signals to digital signals; Micro-controller circuit could process digital signals; LED circuit could display the number of the temperature; RS-485 circuit provided the hardware platform for the communication of upper and lower computer.In the software system, CCS2.2 is adopted as the environment of system. The main program, AD converter program, LED display program and RS-485 communication program are designed based on correctly configuring the CMD file, properly allocating the memory space and correctly writing the head file. On the basis of this analysis, real-time collection of temperature, data sending and receiving are implemented.System optical circuit was set up at last to test the monitoring system and some actual data has been obtained, which provide a basis for the further work.