Study On Mode-Locking Coupled Optoelectronic Oscillator

Microwave photonics serves as a bridge between optics and microwave engineering,and overcomes the inherent limitations of electronics in processing microwave signals.As a multi-functional and flexible photonics platform,microwave photonics has a very broad application prospect.Among the rich studies of microwave photonics,coupled photoelectric oscillators(COEOs)attract attention because they can simultaneously generate low-phase noise microwave signals and narrow light pulses.Based on the typical COEO,two schemes are constructed and studied in this thesis,which are experimentally demonstrated to realize the generation of microwave signal and microwave pulse signal,respectively.The main work of this thesis is as follows:1.The research progress of microwave photonics is introduced.The application direction of microwave photonics in recent years is introduced from three aspects:generation,transmission and processing of microwave signal in optical domain.The research progress of COEO at home and abroad in recent years is reviewed.2.The fundamental aspects of the COEO are analyzed and summarized.The modelocking process of the COEO is analyzed in detail.The factors that affect the performance of the COEO are introduced,and the noise sources are summarized and analyzed from three aspects: inherent noise from the devices,supermode noise,and environmental noise.3.The mathematical model for analyzing the performance of the COEO is verified by simulation and by experiment.In the experiment,a microwave signal is obtained with a center frequency of 9.998 GHz,a phase noise of-74.7 d Bc/Hz@10 k Hz and a sidemode rejection ratio of 52.18 d B.4.Research on the generation of microwave signals and microwave pulse signals based on improved COEO.A semiconductor saturable absorber mirror(SESAM)is added in the optical loop of a typical COEO to suppress supermode noise due to its saturable absorption effect.A corresponding mathematical model for this modified COEO with SESEM is established,and simulation analysis and experimental research are conducted.The results show that,compared with the traditional COEO without the SESAM,the quality of the generated microwave signal is improved.In the experiment,a microwave signal is obtained with a center frequency of 10.0057 GHz,a phase noise of-91.2 d Bc/Hz@10 k Hz and a side-mode rejection ratio of 77.36 d B.A scheme of active mode-locking coupled optoelectronic oscillator has been designed.By introducing an additional active mode-locking mechanism into the typical COEO,the generation of high repetition frequency microwave pulse signals has been achieved.Experiments have been realized with fundamental frequency mode-locking,second order harmonic mode-locking,and tenth order harmonic mode-locking.Microwave pulse signals are generated with a carrier frequency of 10 GHz and a repetition frequency of 550 k Hz,1.11 MHz,and 5.5 MHz,respectively.