Characteristics Of Chaotic Output From A Gaussian Apodized Fiber Bragg Grating Feedback Semiconductor Laser

Since the birth of a semiconductor laser(SL),with its relatively small volume and relatively low manufacturing cost,it has played an important role in many fields,such as optical communication,optical storage and optical interconnection.Normally,If the external disturbance is not introduced,it will carry out continuous-wave output at this time,but SL is a nonlinear device,when it is subjected to external disturbances,such as optical feedback,optical injection,photoelectric feedback,and so on,it will show a series of rich and colorful dynamic characteristics.Among these external disturbances,optical feedback disturbance to SL is a special one.It is widely used because of its simple structure,relatively easy operation and the ability to generate high-dimensional optical chaos under suitable feedback parameters.However,the transmission of the output light in the outer cavity will inevitably lead to the introduction of a more obvious delay feature(TDS)in the chaotic output of the optical feedback SL system,chaos TDS will threaten the communication security of the secure communication system,reduce the statistical properties of a random number and incorrect detection of chaotic radar target.Based on the above reasons,it is of great practical significance to study how to suppress the chaotic output of TDS in the optical feedback SL system.For the optical feedback SL system,the outer cavity of the SL usually selects a plane mirror.The plane mirror feedback makes the different frequency components of the signal back to the SL with the same transmission time,which does not have wavelength selectivity.For F-P interferometer or fiber Bragg grating(FBG)and other filtering devices,wavelength selective optical feedback is provided,so that different frequency light is sent back to SL through different group delay,which can better suppress the TDS of chaotic signal.And some researches prove that the Gaussian apodized Fiber Bragg Grating(GAFBG)provides higher group delay than uniform FBG under the same reflection bandwidth.If GAFBG is used to form the external cavity of SL,the chaotic output with lower TDS will be obtained.Based on this,using the method of GAFBG to replace the plane mirror in optical feedback semiconductor laser,and construct a GAFBG feedback semiconductor laser system in this paper.And numerical simulation evolution of GAFBGF-SL dynamic state,using the autocorrelation(SF)analysis method,the evolution of TDS of GAFBGF-SL was studied.At the same time,considering the chaotic bandwidth is another key index to evaluate the quality of chaotic signals,the chaotic bandwidth of the system is also calculated by using the effective bandwidth calculation method in related literature.The numerical simulation results show that,with the increase of feedback strength in the system,the output of GAFBGF-SL system will show the dynamic evolution path from steady state,quasi periodic state to chaotic state finally.The two feedback parameters(feedback strength and the frequency detuning between the Bragg frequency of the GAFBG and the peak frequency of the free-running SL)will significantly affect the TDS of the chaotic output of the system,and under the action of appropriate feedback parameters,the chaotic TDS output of the system can be well suppressed.By mapping of the TDS and effective bandwidth of the GAFBGF-SL system under the parameter space composed of two kinds of feedback parameters,it provides the best range of feedback parameters for obtaining weak TDS and wide bandwidth high quality optical chaotic signals.