Reconfigurable Microwave Photonic Filter Based On Stimulated Brillouin Scattering

Microwave photonic filters are one of critical components of both civil and military applications such as communication,imaging,sensing,and radar systems.Traditional microwave filters are difficult to achieve reconfigurable passband due to the technical bottlenecks,which have narrow bandwidth,short transmission distance and high loss.The microwave signal is modulated into optical domain combined with the electro-optic modulator.After the transmission and processing,the signal can be converted back into the electrical domain.It is recognized as one of the most promising techniques to realize high frequency signal transmission due to the advantages,which is anti-electromagnetic interference,long transmission distance,low phase noise transmission and low cost.The gain spectrum and loss spectrum generated by stimulated Brillouin scattering have the advantages of narrow bandwidth,high gain and tunable,which are widely used in the optimization of microwave photonic filters performance.Therefore,it is critical worthy to study the reconfigurable microwave filters by the stimulated Brillouin scattering.This thesis focus on the research of the reconfigurable microwave filters based on the stimulated Brillouin scattering.In the experiment,the center frequency and the bandwidth can be reconstructed based on the stimulated Brillouin scattering.Propose a scheme about the dual-passband and the dual-stopband bandwidth reconfigurable microwave photonic filters.The main contents of this thesis are listed as follows:1.The development history of microwave photonic filters is introduced.The coupled equations of stimulated Brillouin scattering effect is studied.A reconfigurable microwave photonic filters based on nonlinear effect is feasible through the theoretical analysis.A typical microwave photonic filter link based on the combination of phase modulation and stimulated Brillouin scattering is designed.The vector network analyzer is used to sweep frequency in a tuning range from 1 GHz to 20 GHz to obtain the passband signal.The experiment results indicate that the filters passband is at the frequency difference between the pump beam and the Brillouin frequency shift.The 3 d B bandwidth is 21 MHz.2.In order to overcome the problem that the traditional filters has limited center frequency and bandwidth shape of in the electric domain,the reconfigurable microwave photonic filters based on stimulated Brillouin scattering are proposed and verified.The center frequency of filter passband can be controlled flexibly by changing pump beam frequency.In the experiment,the tuning range of the center frequency is 0.6-5.6 GHz.The filters passband can be broadened by using an optical frequency comb which is cascaded by a Mach Zendar modulator and a dual-drive Mach Zendar modulator as the pump beam.In the experiment,the filters passband can be broadened from 21 to 80 MHz.3.In order to meet demand of the dual-frequency signal in frequency conversion,wireless communication,sensing and other aspects,the passband filters and band stop filters based on stimulated Brillouin scattering effect are proposed and verified.In the experiment,the bandwidths in the double-pass passband filter of passbands 4.6 GHz and16.6 GHz can be broadened from 33 MHz to 87 MHz,the bandwidths in the double-pass band stop filter of two stopbands 9.58 GHz and 11.6 GHz can be broadened from 40 MHz to 118 MHz.