The Study Of High Performance Microwave Photonic Filter

Our society is gradually developing,high-tech industries are also making progress.In order to improve the speed and accuracy of communication,many scholars all have thought of combining wireless access networks with optical communication.To achieve this thought,scholars have opened up a discipline which is new,combines microwave and optics,and cross-complementary.That is microwave photonics,MWP.The field is mainly to study how to use photonic knowledge to add to microwave signals,then to generate,process and transmit and so on.Based on this,microwave photonic filter,MPF,it has many advantage that the electric domain filter in the traditional method doesn't have.It can overcome the limit of electronic bottlenecks,large instantaneous bandwidth,tunable,reconfigurable,low loss,small footprint,strong anti-electromagnetic interference and so on.In our life,it can be used to Radio-over-Fiber,Optically Controlled Phased Array Radar,Electronic Warfare and other field.As a module that is worthy of attention in communication links,the quality of MPF will have a direct impact on the quality of the entire communication system.This paper introduces the basic theory,the history of development at home and abroad,the use in daily life of MWP and MPF.And the reacting process of Stimulated Brillouin Scattering,SBS,it also introduces Brillouin gain spectrum loss spectrum,coupling equation,threshold and so on,sets up the actual link system to test the Brillouin frequency shift.Using cancellation of the gain spectrum and loss spectrum,increases the frequency tunable range of the filter.If the peak center frequencies of Brillouin gain spectrum and loss spectrum are same,then both of them can cancel each other,so if multiple pump signals are introduced,the frequency interval value between the adjacent pumps is set to 2v B(v B is Brillouin frequency shift),then the gain spectrum generated by the pump in the high frequency region and the loss spectrum generated by the pump in the low frequency region will cancel out,so the center frequency tunable range of the filter is 2Nv B(N is the number of pump lights).For the single passband MPF based on phase modulation,intensity modulation and SBS,this paper analyzes the theory,simulates numerical values and has an experiment to verify.Explores whether the change of pump power will affect the 3 d B bandwidth and out-of-band rejection ratio(OOBR)or not.Compares the stability of the two systems which are the laser source directly as the pump signal and the modulation signal as the pump signal.The frequency tunable range of ordinary filter is about 0.5GHz to 18.3GHz,the 3d B bandwidth is 23 MHz,and the OOBR is 30 d B;the wide tunable filter has a frequency tunable range of about 0.9 GHz-31.3GHz,3d B is 26 MHz,the OOBR is 26 d B.This paper proposes a notch filter that is opposite to that of the previous passband filter.This kind of MPF realizes the reconstruction of the numbers of notches,notch frequency and notch spectrum type by changing the numbers and frequency of pump signals.There are three cases: When the frequency of the first microwave signal source input to the MZM is 2v B,the system will output a single notch,and the center frequency tunable range depends on the number of pump signals;when the frequency is greater than 2v B,the filter can generate multiple notches,and if the numbers of pump signals are different,the numbers of notches are different;when the frequency is between 0 and v B,the gain spectra generated by the multiple pump signals are overlapped each other,producing a notch with a widened bandwidth.