Optical Generation Technology Of Flat Millimeter Wave Noise Based On Vernier Effect

Noise generator has become a hot topic in the current research,with a broad application prospect,such as communication,sensing and military.Therefore,it is crucial to investigate the high-frequency noise generators.Among them,improving the flatness of noise power spectrum is a key research work.The noise generated by electrical methods is mainly restricted by the bandwidth of electronic equipment,and it is difficult to develop high-frequency noise generator.Compared with electricity,optical method has great potential to generate broadband flat millimeter-wave noise.Optical beat frequency technology can generate millimeter-wave single frequency signal of target frequency.This method can be used to generate high frequency noise,but the noise flatness is not ideal,which becomes a new problem.Based on the method of photonics and vernier principle,this thesis proposes a method to generate broadband flat millimeter-wave noise by using veriner effect of vernier comb light beat frequency.The main research contents of this thesis are as follows:(1)The high frequency millimeter-wave noise signal generated based on photonics is theoretically analyzed.According to the optical spectrum autocorrelation operation,the spectrum is mapped to the frequency spectrum,and the effects of spectral linewidth and center wavelength on the noise spectrum are analyzed.Combined with the beat frequency theory,a method of generating broadband flat millimeter-wave noise based on vernier effect is proposed.The rationality of using vernier comb light beat frequency to generate flat noise is analyzed theoretically,and verified by numerical simulation.(2)According to the theoretical analysis and numerical simulation results,two vernier multimode chaotic beams are used to produce broadband flat millimeter-wave noise.In experiment,two vernier-type multimode chaotic beams with different mode intervals are coupled to the photodetector for beat frequency,thus generating electrical noise signal.In experiment,the flatness of ± 1.45 d B in 0-50 GHz range is achieved,and the excess noise ratio is greater than 39 d B.Meanwhile,VPI optical simulation software is used to simulate and analyze the mechanism of flat noise generated by vernier effect based on vernier multimode chaotic light beat frequency.(3)In the above study,because the mode interval of the laser is limited by the cavity length,theoretically it is difficult for the noise generated by the vernier effect to produce higher frequency.Therefore,vernier effect based on comb filter beat frequency is proposed to generate high frequency millimeter-wave noise.Through numerical simulation,the proper size of the main and vernier scales of comb light is selected to generate flat noise spectrum in millimeter-wave band(30 GHz-300 GHz).In experiments,a programmable optical filter is used to comb the incoherent light source(SLD)to generate a vernier-type comb light with controllable mode intervals.In the frequency range of 130 GHz-170 GHz and 280 GHz-380 GHz,mmw-noise with flatness of ±2.25 d B and ±3.1 d B is generated,and the excess noise ratio is greater than 28 d B and 18 d B,respectively.The current study provides a novel approach for the fabrication and study of noise generator with high flatness,high bandwidth,and high noise ratio and has established a foundation for the development and utilization of noise generator.