Research On The Characteristics Of Chaotic Laser Based On Power Spectrum Analysis And Time-Frequency Analysis

Chaos lasers have been widely used in secure communications,optical fiber sensing and other fields due to their noise-like,wide spectrum,and synchronizable properties.The research on the characteristics of chaotic lasers is a hotspot at present.Common research methods of chaotic laser characteristics include timing characterization,spectral characterization,power spectral characterization and time-frequency characterization.Using power spectrum analysis and time-frequency analysis to study the characteristics of chaotic laser is of great significance for revealing the generation mechanism of chaotic laser.However,the influence mechanism of RBW and VBW in the power spectrum analysis method to accurately measure the effective bandwidth and delay characteristics of chaotic signals is still unclear,and the time-frequency analysis method has not deeply studied the time-frequency dynamic characteristics of chaotic signals under different time windows.It is difficult to fully reveal the formation and evolution of chaotic lasers.Aiming at the above problems,the power spectrum analysis method and the short-time Fourier transform time-frequency analysis method of the periodogram combined with the first-order low-pass filtering method are used to study the power spectrum characteristics and time-frequency characteristics of chaotic signals respectively.The specific work is as follows:（1）The power spectrum characteristics of the chaotic signal are studied by using the periodogram and the first-order low-pass filtering method,and the bandwidth characteristics and periodic characteristics of the chaotic power spectrum are accurately obtained.The Lang-Kobayashi rate equation is used to generate the chaotic signal,and the periodogram method combined with the first-order low-pass filtering method is used to obtain a complete and smooth power spectrum,which effectively suppresses the power spectrum distortion caused by the randomness of chaos.The power spectrum characteristics of chaos under different equivalent resolution bandwidth(RBW_eqv.)and equivalent video bandwidth(VBW_eqv.)are further studied in numerical simulation.The results show that the bandwidth and period characteristics of chaos can be accurately characterized when RBW_eqv.Furthermore,the chaotic laser signal is generated based on the single feedback semiconductor laser structure,and the power spectrum characteristics of the chaos are studied by using the swept frequency spectrum analyzer,and the characterization of the spectrum characteristics of the chaotic laser is studied by changing the RBW and VBW.The experimental results are consistent with the simulation results,which reflect the accurate representation of the chaotic power spectrum characteristics.（2）Using the short-time Fourier transform method,the time-frequency analysis of the chaotic signals generated by the experiment and simulation is carried out respectively,and the time-varying characteristics of the chaotic spectrum under different time-resolved windows are studied by using the correlation coefficient method.The results show that no matter for the chaotic signal generated in the experiment or the chaotic signal generated in the simulation,the time sequence of the chaotic signal with a length of more than 500 ns contains the complete spectrum components of the chaos.And the time-resolved spectral dynamic evolution process of the chaotic laser signal at different time scales is obtained.