Research On Photonic Microwave Noise Generator Based On Chaotic Laser

With the development of science and technology,high-precision scientific research instruments are indispensable in measurement,calibration and other applications.However,the influence of noise on the accuracy of the instrument can’t be ignored.In order to verify the reliability of the instrument,stable and controllable noise generator has become an important instrument for system measurement.In aviation,radar and other fields,due to the complex working environment,the traditional noise generator is limited by the device itself,with low noise frequency,small output excess noise ratio(ENR),and there are problems such as large volume,the need for external refrigeration equipment when working,and the application scenarios are limited.Therefore,the noise generator with high frequency,large ENR and easy integration of components has broad prospect.The noise produced by traditional electrical methods is mainly affected by the frequency of electrical devices,so the bandwidth of noise generated is limited.The avalanche noise generated by Schottky diode is limited by its frequency,and with the increase of frequency,the difficulty of device fabrication increases accordingly.With the rapid development of optical integrated devices in recent years,some researchers use photonics methods to generate noise through photoelectric conversion,but the small output ENR has become another new problem.In this paper,a microwave noise generator based on chaotic laser is proposed to overcome the disadvantages of the noise generation method such as limited electrical frequency and small photonic ENR.Based on the large amplitude noise like characteristics of chaotic signal,white noise signal in micro band and high ENR are generated.Through theoretical research of spectral linewidth,the limiting factors of noise bandwidth are found out.Specific work and results are as follows:(1)In this paper,chaotic laser is used to generate noise,and the way to generate noise is analyzed theoretically.The influence parameters of noise bandwidth and center frequency are also determined;(2)A broadband chaotic source with chirped fiber Bragg grating as the main device is constructed experimentally.The effects of feedback intensity and wavelength detuning on bandwidth and time delay signature under different dispersion conditions are studied.After adjusting the polarization and feedback intensity,the 3dB line width of the optical spectrum reaches 0.2～0.3nm when the feedback intensity is about 3;(3)Based on wide spectra source,two closed-loop circuits are constructed.Beat frequency is obtained by two wide spectrum light sources with 3dB linewidth of 0.2nm.The broadband white noise with 30GHz bandwidth is obtained.The autocorrelation has no time delay signature.The skewness of time series distribution is 0.019,noise bandwidth and center frequency are adjustable.Finally,the ENR of the generated noise is tested,and it is calculated that the ENR of the generated noise is greater than 20dB in the frequency range of 30GHz.