Research On Chaos Synchronization And Key Distribution Of Semiconductor Lasers With Dispersion Feedback

In today's society with the rapid development of information,high-speed and safe information transmission is one of the hot issues.Traditional secure communication mainly uses algorithm encryption technology,and its security mainly depends on the complexity of the algorithm.With the rapid increase in computing power,algorithm encryption is always in danger of being cracked in principle.The quantum key distribution technology based on the physical layer utilizes the principle of quantum unclonability and uncertainty,with absolute security,and is strongly supported by the government.However,technical bottlenecks such as single-photon detector efficiency and dead time limit the key distribution rate.In addition,researchers are also constantly exploring classic physical layer key distribution techniques,including methods such as random selection of fiber laser parameters,physical unclonable functions,channel noise,and chaos synchronization.The key distribution rate of fiber laser and channel noise is limited in principle by cavity length and entropy source bandwidth respectively.The physical unclonable function can only grow static keys of fixed length,which cannot meet the requirements of Gbps distribution rate.In the key distribution based on chaos synchronization,the chaotic laser has a bandwidth of up to tens of GHz,which is a broadband chaotic entropy source.Limited by the synchronous keying rate,the key distribution rate is mostly lower than 1 Mbps.In addition,the external cavity feedback semiconductor laser is widely used as a source of chaotic entropy due to its simple structure,easy operation,and easy integration.However,the chaotic signal generated by it has two obvious defects: The existence of time delay signature will expose the parameters of the system and bring safety hazards;the existence of relaxation oscillation characteristics makes its spectral energy low,resulting in low energy utilization of its chaotic signals.In response to the above problems,this thesis proposes a chaos synchronization and key distribution scheme based on a dispersion feedback semiconductor laser.The specific work and results are as follows:(1)The Lang-kobayashi equations are modified to obtain the model of the chirped fiber Bragg grating(CFBG)dispersion feedback semiconductor laser.The complexity of the chaotic signal generated by the CFBG feedback is analyzed.Due to the nonlinear effect of the grating,high complexity chaotic signals whose time delay signature are suppressed or even eliminated can be obtained.The influence of parameters on permutation entropy and delay signature is studied.Through the analysis of the laser's internal parameters,external parameters and grating parameters,a high complexity parameter region that can eliminate the time delay signature and the permutation entropy value is higher than 0.994 is obtained.Compared with the mirror feedback result,the high complexity parameter range under the CFBG feedback is larger.(2)A dispersion feedback semiconductor lasers commonly-driven chaos synchronization scheme is proposed.Using amplified spontaneous emission as the driver,two closed-loop semiconductor lasers with dispersion feedback are driven to achieve chaotic synchronization.Use dispersion compensation module(DCM)to introduce dispersion.When the synchronization of 0.963 between the two response lasers is achieved,there is almost no correlation between the drive signal and the response signal.The analysis of the internal parameters mismatch and DCM parameters mismatch of the two response lasers shows that the system has the robustness of parameters mismatch.The method of double threshold quantization is used to quantize the chaotic signal to obtain random numbers,and to test their randomness.The longer synchronization recovery time(approximately 52 ns)in this scheme will reduce the key generation rate.(3)A key distribution scheme for CFBG dispersion keying synchronization is proposed.The external cavity feedback semiconductor laser is used as a driver to drive two open-loop semiconductor lasers to achieve synchronization.After the nonlinear effect of the dispersion,the correlation between the drive and the response is eliminated,and the safety of the scheme is ensured.Using CFBGs with different dispersion values as the private key,when chaos synchronization is achieved,the chaotic signal is quantized with two thresholds,and then the consistent key is extracted.The open-loop synchronization method is adopted to shorten the synchronization recovery time to the order of ps.In theory,it is possible to achieve a high-speed key distribution with a bit error rate lower than the forward error correction hard decision and a rate of 1.2 Gb/s.