| In recent years, optical fiber sensing technology has been widely used in the health of structures field to monitor the temperature and strain,due to its advantage such as high sensitivity, avoiding the electromagnetic, adapting to harsh environment and easy to form sensing network.The distributed sensing technology based on optical fiber Brillouin scattering not only has the advantages of the traditional optical fiber senor also can achieve high accuracy, high spatial resolution and achieve the real-time monitoring in the application.This paper elaborated the researching background of sensing system based on BOTDA, development status and trends in the world and described mechanism of optical fiber Brillouin scattering.It theoretically analyzed the primary parameters and their influence factors of the sensing system based on BOTDA and discoursed application on detecting leaking of the oil pipeline.In experimental studies, the width of pump pulse light was 10 ns in the sensing system based on BOTDA and its corresponding spatial resolution was 1m.By using spiral distribution sensing optical fiber, it can improve the actual monitoring spatial resolution to be 0.5m.Respectively, It was done that using the ordinary single-mode fiber and non-zero dispersion shifted fiber as sensing fiber to research that Brillouin scattering gain and Brillouin linewidth effected on the measurement accuracy. The results indicated that the Brillouin gain of non-zero dispersion shifted fiber was about 1.17 and its Brillouin linewidth was about 82 MHz with a small amount of change with temperature.Therefore, non-zero dispersion shifted fiber is more suitable for long distance, high accuracy in temperature measurement field.As the temperature field is slowly changing field, when the sensing optical fiber which was scribbled the thermal grease was used as sensing fiber, it would reduce heat conduction error and can improve temperature sensing accuracy. |
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