Reconfigurable Dual-channel Microwave Photonic Filter With High Performance

Microwave photonic filters are high-performance devices that have emerged in the field of microwave photonics.They find wide applications in areas such as optical communication,sensing,and radar detection,particularly in defense and military industries.Compared to traditional electronic filters,microwave photonic filters utilize electro-optic modulators to load microwave signals onto optical carriers.The signals are then transmitted and processed using optical components.Finally,photodetectors convert the signals back to electrical form for output.These filters offer significant advantages such as high performance,strong confidentiality,wide operating frequency range,low loss,strong immunity to electromagnetic interference,flexible reconfiguration,and low cost.This thesis first introduces microwave photonics and its application in the field of filters.It provides an overview of the research status and recent developments in microwave photonic filters both domestically and internationally.Additionally,the thesis introduces the optical components commonly used in microwave photonic filters and presents a detailed explanation of the basic principles and important performance parameters of these filters.Based on this foundation,two high-performance tunable dual-channel microwave photonic filters are proposed and theoretically simulated and experimentally verified.The specific work of the paper is as follows:A dual-channel reconfigurable microwave photonic filter based on a dual-polarization dualdrive Mach-Zehnder modulator(DP-DDMZM)and a phase-shifted fiber Bragg grating(PS-FBG)is proposed.MATLAB is used for simulation and the filter is experimentally verified.The DPDDMZM is properly biased to function as a single-sideband(SSB)modulator or an equivalent phase modulator(E-PM).The PS-FBG is used for notch filtering through phase modulation or quasi-single-sideband modulation of one sideband,thereby achieving a single-passband or singlenotch filter.Three types of microwave photonic filters are realized: single-passband dual-port filter,single-notch dual-port filter,and hybrid single-passband and single-notch dual-port filter.The suppression ratio of the frequency response for the single-passband filter exceeds 20 d B,and for the single-notch filter exceeds 35 d B.The experimental results show the frequency responses for both single-passband and single-notch filters can be tuned within the 0-18 GHz range.A large out-of-band suppression reconfigurable microwave photonic filter based on a dual-drive Mach-Zehnder modulator(DDMZM)and a polarization-maintaining phase-shifted fiber Bragg grating with low birefringence(PM-PSFBG)is proposed.MATLAB is used for simulation and the filter is experimentally verified.The PM-PSFBG with low birefringence has fast and slow axes with slightly different effective refractive indices that are mutually orthogonal.When the phase modulation signal or single-sideband modulation signal is at a 45° angle to the fast or slow axis of the PM-PSFBG,the fast and slow axes of the PM-PSFBG are aligned with the two principal axes of the polarization beam splitter(PBS),two single-passband filters or two single-notch filters with slightly different frequencies are realized.By appropriately adjusting the polarization controller(PC)to satisfy specific angular relationships between the polarization direction,PM-PSFBG,and the principal axes of the PBS,performance-improved single-passband filters with large out-of-band suppression ratio can be obtained through subtraction of the responses from the two filters.