Study Of Strain Measuring Method Based On Optical Fiber Resonant Cavity

With the fast development of the application of optical communication and the technology of optical fiber manufacturing and semiconductor laser, the area of fiber laser has stepped into a new world. At the same time, fiber laser has also become a more and more important component in the field of fiber sensors. Sensors based on fiber lasers can overcome such drawbacks as weak feedback signal and low signal to noise ratio. Also all in-fiber sensing system can be realized because of the application of fiber lasers. So the research on fiber lasers may have a significant meaning for the development of the technology of optical fiber sensing.This dissertation focuses on the research of the theories and experiments of strain sensing system based on single-mode linear-cavity fiber laser. Firstly, we introduced the characteristics, basic theories, configuration, classification and application of fiber lasers. Then, we investigated the basic theories of single-mode linear-cavity fiber laser, and did the numerical analyzation and computer simulation. The condition for the realization of single-mode linear-cavity fiber laser has been analysed theoretically, and the relationship between the condition and the reflectance or the cavity length has been brought up. After that, a driver circuit for the 980nm semiconductor laser has been devised according to the requirement for constant output power and tunable output power. At last, a strain sensing system based on a novel linear-cavity fiber laser has been designed and the driver circuit and sensing system has been tested. From experiments, the relationship between the central wavelength and strain has been acquired, and the results match the theoretical analyzation very well. The threshold of pump light intensity has been got by experiments, and laser spectrum and fluorescence spectrum before lasing have been compared.The laser signal coming from the linear-cavity fiber laser we designed in this work has a broader bandwidth and higher signal to noise ratio comparing to traditional double fiber Bragg gratings(FBG) sensors, and can meet the requirements of our experiment totally. We hope our work of numerical analyzation and experimental study on the strain sensing system based on single-mode linear-cavity may have an impact on our future research both theoretically and experimentally.