Research On Microwave Photonic Sensing And Demodulation System Based On Comb Filtering Broadband Light Source

With the development of optical fiber technology,the microwave photonic（MWP）technology combined with photonic technology and microwave technology has attracted the interest of many researchers.This technology has the advantages of low loss,anti-electromagnetic interference and high data transmission capability.Using MWP technology to demodulate optical fiber sensing signals can not only improve the resolution and speed of demodulation,but also effectively reduce the cost of demodulation.This thesis focuses on the theoretical analysis and experimental research on the application of microwave photonic filter（MPF）based on broadband light source comb filtering in the sensing field,and analyzes the sensing demodulation characteristics of three comb filtering structures,namely,single interferometer,interferometers cascade and interferometers parallel,in order to optimize the demodulation method of traditional optical fiber sensor and provide a high-resolution demodulation scheme for optical fiber sensor.The specific work is as follows:（1）The refractive index sensing and demodulation characteristics of MPF based on a single interferometer are analyzed theoretically and studied experimentally.The analysis results show that the refractive index has a linear relationship with the central frequency of the passband,and the experimental research shows that the designed refractive index sensor has a sensitivity of-1.1054 GHz/RIU,9×10^-7 RIU resolution and wide measurement range.（2）The dual-parameter sensing and demodulation characteristics of the MPF based on interferometers cascade are studied theoretically and experimentally.The analysis results show that the cascaded filter has four passbands.Through the reasonable design of the sensor structure,the dual-parameter sensing and demodulation of stress and external temperature without crosstalk can be realized.（3）The multi-channel temperature sensing and demodulation of MPF based on parallel interferometers are studied theoretically and experimentally.The analysis results show that the MPF based on parallel interferometer has double passband characteristics.The dual-channel non-crosstalk temperature sensor with sensitivity of-0.9884 MHz/℃and-1.9302 MHz/℃is realized experimentally.The results show that the sensor has good linearity and stability.