Some Microwave Signal Generation And Filtering Technologies Based On Optical Fiber Devices

Microwave Photonics is a new interdisciplinary research area, which studies the interaction between microwave and optical signals, and has a lot of applications in wireless broadband access networks, sensing networks, microwave measurement and so on. In recent years, microwave photonic technology has attracted intensive research attention. Photonic generation and filtering of microwave signals are two important research areas of microwave potonics technology, and a number of new methods have been proposed, in which little attention has been paid to their performance analysis and applications. On the other hand, due to the inherent advantages, such as large bandwidth, low loss, good tunability and compactness, etc., fiber devices are desirable for implementing the generation and filtering of microwave signals. This thesis focuses on the research on fiber devices based novel microwave signal generation and filtering technology with higher performance, lower cost and simpler configuration compared with the existing implementation methods, and a comprehensive study on their performance is given both theoretically and experimentally; Moreover, their applictions in Radio-over-Fiber (RoF) and fiber sensing systems are exploited, and both theoretical analysis and experimental verification are carried out.To begin with, a brief introduction on the basic concept and research background of microwave photonic technology is given. The recent research progress on microwave signal generation and processing with photonics methods, and their applications in RoF systems, fiber sensing and microwave measurement is summarized.Then, fiber devices desirable for implementing microwave signal generation and filtering are introduced, including fiber Bragg gratings, fiber couplers and fiber delay line devices based on them. The fiber sensing technology is briefly introduced. This part provides the basis for research of this thesis.After that, the study on fiber devices based microwave generation technology is carried out. The research is mainly based on optical heterodyning, which requires that the two beating wavelengths are phase correlated. The methods of beating of fiber Bragg grating Fabry-Perot cavity based dual-wavelength laser to generate microwave signal and microwave signal generation by using Stimulated Brillouin Scattering effect in optical fiber have been proposed. For the application, the beating of dual-wavelength laser is used to realize frequency up/down convertion for microwave signals; the phase-shifted fiber Bragg grating based dual-wavelength laser is applied as a highly sensitive transversal loading sensor for the first time. Then, several fiber devices based novel microwave photonic filters and their performances are investigated comprehensively. The study is carried out both theoretically and experimentally, including:realizing fiber ring based microwave photonic filter with continuous tunability and high Q factor; implementing fiber Bragg grating pair based microwave photonic filter, and analyzing the influences of reflection and Bragg wavelengths of the fiber Bragg gratings on the filters performance; research on the fiber Mach-Zehnder interferometer based continuously tunable microwave photonic filter, and eliminating the baseband resonance by using phase modulation; implementing tunable and reconfigurable microwave photonic filter by cascaded modulators.Furthermore, the applications of microwave photonic filter for the sub-carrier demultiplexing of RoF systems and sensing interrogation systems are studied. The fiber ring based microwave photonic filter and multiple optical source microwave photonic filter are implemented in the RoF systems to filter out the sub-carrier signal with desirable frequency, respectively. The data transmission performance of the systems is characterized in the experiment. A fiber Sagnac loop based microwave photonic filter is used to implement the sensing interrogation for the first time, and the interrogation capability is studied both theoretically and experimentally.In conclusion, study on advanced technology of fiber devices based microwave signal generation and filtering is carried out both theoretically and experimentally in this thesis, and new application areas of this technology are innovatively exploited, which would contribute to the research of microwave photonic technology and its applications.