Signal-to-noise Ratio Analysis And Enhancement Of Stimulated Brillouin Scattering Based Pulse Compression Technology

As a key signal processing technology,pulse compression technology can achieve bet-ter spatial resolution and obtain higher signal-to-noise ratio and is widely used in the field of radar.With the increasing bandwidth of the radar signal,the traditional analog-digital converter(ADC)faces the huge data storage depth and the pressure of real-time processing in the latter part.At the same time,the emerging microwave photonics technology combines the advantages of microwave and photon technology to produce,control and process broadband microwave signals steadily,thereby breaking the bandwidth limitations of electrical ADCs and ultimately to all-optical analog-to-digital converters.In this thesis,a novel pulse compression technique based on microwave photonic signal processing-a pulse compression technique based on Stim-ulated Brillouin Scattering(SBS),is presented.This analog signal processing technique can auto-correlate broadband microwave signals.Therefore,this thesis is aimed to optimize the signal-to-noise ratio(SNR)performance of the technology,and ultimately completes the overall performance optimization.First of all,this thesis briefly introduces the technology and gives the theoretical derivation.At the same time,the SNR of the pulse compression signal is analyzed theoretically and numerically.The key to improve the SNR is to enhance the signal and restrain the noise.Accoring to theoretical deduction and simulation,it is found that the key parameters that affect the SNR are loss coefficient and Brillouin gain coefficient of the fiber.Then,based on the above analysis,the numerical simulation is further carried out.The effects of the key pa-rameters on SNR and bandwidth of pulse compression system based on SBS are discussed.The theory proves that the high Brillouin gain coefficient and the low fiber loss can improve the in-tensity of the pulse-compressed signal,so as to optimize the SNR of compressed signal.Finally,we designed the experimental scheme,and verified the effectiveness of the method to improve the SNR.The influence of relative noise intensity,photo-detector thermal noise on the pulse compression system performance is analyzed,which provides a reference for further optimiza-tion of SNR performance.The experimental results show that the SNR of the pulse-compressed signal is significantly improved after the increasement of Brillouin gain coefficient,and the sys-tem bandwidth breaks through the limit of 1 GHz,finally achieving the pulse compression of the microwave wideband signal of 5 GHz.