The Basic Research Of BOTDA Configuration For The Measurement Of Temperature And Strain Based On LEAF Fiber

Distributed fiber sensors play extremely important role in safety and health monitoring area, especially for large range and high precise measurement. However, when traditional distributed fiber sensors encounter the requirements of multiple parameters measurement with higher precise and resolution, which are hard to be achieved, new methods and mechanisms need to be exploited. Hence, recently the novel solution for distributed fiber sensor is very hot as a topic. In this paper, the sensitivity characteristics of LEAF fiber were explored by the realization of a BOTDA configuration. In this thesis the main contents include:1. Systematically, the development history and current situation of distributed fiber sensors were illustrated, especially focusing on the basic sensing principles of sensors based on Brillouin scattering.2. Elaborately, the principles of BOTDA configuration were illustrated, devices choosing and parameters settings for successfully achieving a BOTDA configuration were analyzed, based on that the design of a BOTDA configuration adopting LEAF fiber as sensing fiber was achieved for the sensitivity test of LEAF fiber for temperature and strain, which specifically contains the generation of a pair of about 11 GHz frequency difference signal, which is essential for realizing successful stimulated Brillouin scattering, and the generation of the pulse signal with high extinction ration.3. The threshold of stimulated Brillouin Scattering was analyzed by solving both analytical and numerical solutions for Brillouin scattering equation which finally contributed to simulation of light transmission in fiber when stimulated Brillouin Scattering occurs under different situations, for example, different fiber type, different fiber length and different pulse width of the pump light.4. Based on the design for a BOTDA configuration, the test for the characteristics of LEAF fiber for temperature and strain was done. The stimulated Brillouin gain spectrum under the room temperature was achieved by manual frequency sweep, coherent detection and point tracing, respectively. After acquiring the stimulated Brillouin gain spectrum of LEAF fiber in different temperature and strain and the data processing, we analyzed the sensitivity of four gain peaks’ peak power, linewidth and frequency shift of LEAF fiber for the temperature and strain, respectively.