Research On All-optical Microwave Oscillators Based On Nonlinear Modulation Characteristics Of Semiconductor Lasers

With the progress and development of science and technology,the application prospects of microwave photonic technology in the generation and processing of radar systems,wireless communications,and photonic microwave signal have become very broad.Significantly,photonic microwave signal generation has a very important basic role in it.In the previous microwave signals generation system,the use of electric microwave devices severely restricted the operating bandwidth of the whole system.In order to improve the problems of the system’s operating bandwidth and relieve electronic bottleneck,the pure optical microwave oscillator is one of the effective methods.At the same time,the semiconductor device has the characteristics of small size,fast response speed and easy integration,such that it can not only overcome the influence of electric microwave devices in the system,but also has huge integration potential in the future microwave photonic system.This dissertation proposes a DFB-LD feedback modulation based all-optical microwave oscillator system,which successfully generates a good-quality single-mode photonic microwave signal.It utilizes the core characteristics of the oscillator,i.e.the stimulated Brillouin scattering(SBS)effect as the frequency selection mechanism in the optical domain and the internal nonlinear modulation characteristics(optical-optical modulation)of the semiconductor distributed feedback laser(DFB-LD)as the all-optical feedback device.The research contents of this dissertation are organized as follows:The main methods of photonic microwave signal generation are summarized,and the theory of nonlinear modulation of DFB-LD is deduced and analyzed.An all-optical microwave oscillator system based on DFB-LD feedback modulation is proposed.In the proposed scheme,the DFB-LD acts as both the light source and the feedback modulator,and the SBS realizes the selection of the frequency of the all-optical microwave oscillator.Using the filtering characteristics of the active optical comb filter(AOCF),it can select a microwave oscillation mode that matches the single-loop oscillation mode.Finally,the proposed all-optical microwave oscillator generates a single-mode photonic microwave signal.In the experimental demonstration,the frequency of the single-mode photonic microwave signal is 10.83 GHz,the side-mode suppression ratio(SMSR)is about 48 d B,and the single side-band phase noise is about-85 d Bc/Hz@10 k Hz.In this dissertation,the nonlinear modulation characteristics of DFB-LD lasers are deeply studied and used for the oscillation generation of photonic microwave signal,which proposes new ideas for the design and integration of photonic microwave signal generation systems.