Microwave Photonic Filter Based On Stimulated Brillouin Scattering Effect

Microwave photonic filter not only overcomes the shortcomings of traditional microwave filter,such as electronic bottleneck and electromagnetic interference,but also has the advantages of low transmission loss,large bandwidth,flexible tuning and fast reconstruction speed,which makes it have great potential applications in satellite communication,optical wireless communication system,radar,and true delay beam of antenna array.Stimulated Brillouin scattering effect has the advantages of narrow bandwidth,low threshold and high gain,it can also excite the gain spectrum with very narrow bandwidth,so that the microwave photonic filter combined with stimulated Brillouin scattering effect can realize the flexible reconstruction of passband bandwidth.Therefore,the microwave photonic filter based on stimulated Brillouin scattering effect has become one of the mainstream schemes in the research of reconfigurable filter.The main research work and results of this thesis are as follows:1.This paper introduces the research background,research progress and basic structure of microwave photonic filter and the related concepts of stimulated Brillouin scattering.It explains the basic structure and working principle of microwave photonic filter based on stimulated Brillouin scattering effect.In additional,the thesis puts forward the preliminary analysis of the reconfigurability of microwave photonic filter by combining optical frequency comb with stimulated Brillouin scattering effect.2.A structure of reconfigurable microwave photonic filter combined with stimulated Brillouin scattering effect is proposed.The stimulated Brillouin scattering effect is combined with the optical frequency comb and simulated with Opti System and MATLAB.The results show that the tunability of the passband of the filter can be realized by changing the frequency of the laser of the pump branch;By changing the number of comb teeth and frequency interval of pump optical frequency comb,the reconfigurability of filter bandwidth can be realized;A flat stimulated Brillouin scattering based reconfigurable microwave photonic filter with 3d B bandwidth of80 MHz and shape factor of 1.38 is obtained;Finally,two major factors affecting the output power of the filter,namely pump power and fiber length,are analyzed.3.A segmented pumped microwave photonic filter combined with stimulated Brillouin scattering effect is proposed for spectrum analysis,which can avoid gain saturation and other nonlinear effects.The results obtained by Opti System simulation software show that the effect of increasing the gain level of small signal is better than that of large signal;The spectrum of the signal to be measured is almost the same as that of itself;And the factor affecting the spectral analysis of the structure,namely the pump power,is analyzed;Finally,a filter with an out-of-band rejection ratio of 63 d B is obtained.