All-optical Microwave Signal Generation Based On Stimulated Brillouin Scattering

Microwave photonic technology combines the advantages of microwave technology with photonic technology,in which the microwave signals generation is the basic reseach.Among various photonic approaches of microwave signals generation,optoelectronic oscillators(OEOs)and coupled optoelectronic oscillators(COEOs)could generate microwave signals with high stability and high spectral purity.However,they are photo-electric hybrid structure.The electronic bottleneck effect of the electrical microwave devices limit the operation bandwidth of the system.If an all-optical microwave oscillator is introduced,the adverse effects of electronic microwave devices can be overcome.This kind of oscillator can be combined with the microwave photonic system,which shows the flexibility of high-frequency microwave signal generation.The main study of this work are frequency selection and feedback modulation in an oscillator.In more detail,stimulated Brillouin scattering(SBS)is employed to complete the optical frequency selection.The optical-optical modulation in semiconductor optical amplifier(SOA)is utilized to carry out all-optical feedback modulation.The main research of all-optical microwave oscillator based on SBS includes the following two parts:Active ring resonance cavity(ARRC)assisted single-mode all-optical microwave oscillator is proposed.In this scheme,the Brillouin-selective sideband amplification technology is used to select the oscillation frequency.In order to accomplish optical-optical modulation,a SOA is employed.An ARRC is used as a tunable optical comb filter with high-Q factor to select one oscillation mode.A single-mode microwave signal with frequency of 10.83 GHz is obtained when the oscillation is established.The side-mode suppression ratio of the generate signal is approximately 48 d B.Furthermore,the tunability of this system can be demonstrated by varying the wavelength of the light source.A coupled all-optical microwave oscillator with large tuning range based on SBS is proposed.In this system,a set of muti-modes as frequency references are provided by a fiber ring laser and carried by the probe light to induce SBS.Then,those transferred muti-modes in Brillouin gain region are selectively amplified,which come into been Stokes light.A stable phase relationship between probe light and Stokes light will be established through a positive feedback loop.A single-mode microwave signal with high stability and good quality is generated.By adjusting the wavelength of pump light,a wide tuning range is achieved.In addition,the generated microwave signals have low phase noise,and the single side-band phase noise(SSB)of those signals are around-90 d Bc/Hz at 10 k Hz.The related research of this work makes full use of the photonic technology and provides possibilty for the future microwave photonic system.