Theoretical And Experimental Investigations On Microwave Photonics Signal Generation And Processing

The research value of the microwave photonics(MWP) lies in two aspects, on the one hand, the advantages inherent to photonics make it possible to have functions in microwave systems those are complex or even not directly possible in the radiofrequency domain(such as fast tunability and reconfigurability and so on). On the other hand, it also creates new solutions for systems and networks of information and communication technology. MWP is currently making scientific and commercial breakthrough in the fields of all-optical generation of microwave signals, filtering and frequency conversion, microwave photonic fiber links, and optical packet switching. Therefore, the research of all-optical generation and processing of microwave signal has important significance. The main research contents of this dissertation can be summarized as follows:1. The development foundations, the fundamental principles, focuses and significations of MWP are analyzed. The recent advances and development trends for the microwave signal photonic generation and filtering process are systematically summarized.2. Operation principle and design procedure of the solid-state unidirectional non-planar ring oscillator(SUNPRO) laser are presented, which is consist of the resonant cavity structure and geometric optical path analyses, eigenpolarization state analysis of the resonant cavity, the determination of design parameters of the laser and the stability analysis of the resonant cavity. Based on the principle of temperature control, the laser frequency stability is studied, and the laser frequency stability is also analyzed based on Fabry-Perot(FP) cavity, which is consist of the laser frequency stability analysis based on the Pound-Drever-Hall(PDH) and the FP cavity stability analysis based on PDH laser frequency stabilization. With the help of heterodyne beat of two independent operation SUNPRO lasers, one can obtain a microwave signal source with 30 GHz frequency tuning range.3. The basic principle and mathematical expression of the governing equations of the stimulated Brillouin scattering(SBS) effect are analyzed, especially the mechanism of inelastic light scattering and acousto-optic coupled equations of the SBS are analyzed. The relative equivalent dispersion parameters of narrowband pumped Brillouin filter are analyzed. The analysis of signal distortions of the narrowband pumped Brillouin filter is presented, numerical simulation results show that saturation effect of Brillouin filter restricts the linearity performance of the relevant filter, wider pulses obtain both larger signal decibel gain and less broadening factor, and thus they are suitable for this type of SBS-based MWP narrow bandpass filtering system.4. By increasing the bandwidth of the pumping light source, the bandwidth of the Brillouin filter can be improved, and then the basic theory of broadband pumped Brillouin filter is investigated. In fact, the SBS gain spectrum of the broadband pumping light can be expressed as the convolution of the power spectrum of the pump and the intrinsic Brillouin gain spectrum, the spectrum of Gaussian broadband pumped Brillouin filter and the distortion characteristics are analyzed. The performance differences between the Gaussian broadband pumped Brillouin filter and narrowband counterpart are given, and the results show that the second order gain non-uniformity is the main reason of the distortions of the narrowband and broadband pumped Brillouin Gaussian filter.5. Based on the basic theory of broadband Brillouin filter, the additional gain and phase shift characteristics of Brillouin filter are studied further under the condition of the rectangular broadband pump, the distortions of the filter caused by the second order gain non-uniformity and the third order dispersion(TOD) are discussed in detail, the results show that the TOD is the main cause of the distortions of the rectangular broadband pumped Brillouin filter. In view of the MWP digital communication link application, filtering characteristics of three kinds of pulse signal code pattern RZ-OOK, NRZ-OOK and RZ-DPSK are analyzed and compared. The above mentioned three types of code pattern datas are filtered by the rectangular broadband pumped and the Gaussian broadband pumped filter system respectively. The eye diagrams show that the rectangular broadband pumped filter system has much less time delay and distortion for Stokes pulse signal. The gain non-uniformity and the TOD are independent of eye diagrams deterioration, especially in the filtering process of RZ-OOK and RZ-DPSK code pattern datas.6. The feasibility of using the temperature control to achieve tunable MWP Brillouin filter is discussed, and the relational expression between the Brillouin frequency shift and the temperature is worked out. The theoretical derivation and experimental verification of the temperature dependence of the refractive index of the fiber which affect Brillouin frequency shift are carried out in detail. More specifically, a theoretical proof for the linear correlation between the refractive index and temperature is presented, and by means of an optical fiber time delay measurement technique, the refractive index changes caused by the time delay in the wide temperature range of 301~1275 K are verified by the experiments, and the theoretical result is in agreement with the experimental one. Under given condition of a certain strain, a formula between the Brillouin frequency shift and the change of temperature is theoretically derived, for the standard single mode fiber, the passband of Brillouin filter varies with the change of the temperature at the rate of 1.32 MHz / ℃.