Study Of Secure Communication Technology Based On Chaotic Semiconductor Laser

The potential of secure communication based on the chaos in semiconductor laser is extremely huge.Generally,the application of chaos in secure communication consists of chaos-based communication and secure key distribution,which can provide physical layer security and high-rate physical random key respectively.This thesis focuses on the optimization and design of signal source based on external cavity semiconductor laser(ECSL),chaos-based secure communication,and secure key distribution(SKD)by using the chaos synchronization.1.The optimization methods for signal source based on external cavity semiconductor laserThe chaos generated by the external cavity semiconductor laser system holds evident time delay signature(TDS),which limits its application greatly.Therefore,there is a huge demand for TDS-suppressed chaos.For TDS in the ring-cascaded semiconductor lasers(RCSLs),TDS suppression using additional feedback loop is proposed and numerically demonstrated.The results show that by properly setting the feedback strength,the TDS can be suppressed well.Moreover,for the TDS suppression in the ECSL subject to optical feedback,two schemes based on the phase modulation are proposed and demonstrated.One is achieved by embedding the phase modulators(PM)into the double feedback loop one by one and performing fast random digital phase perturbation to the feedback light.The numerical and experimental results show that the size of TDS decreases with the increasing of phase modulation rate and index.With adequate modulation rate and index,the TDS can be suppressed very well.The other one is using the self-chaos phase modulated optical feedback(SCPMOF),where the chaos generated by the ECSL is used as the driving signal of PM after photoelectric conversion.The simulation and experiment results indicate that with appropriate feedback strength and phase modulation coefficient,TDS induced by the optical feedback can also be suppressed.Moreover,the probability density distribution of chaotic time series in the ECSL subject to the SCPMOF is more like the Gaussian distribution than that in the ECSL subject to conventional optical feedback(COF).P1 microwave generation based on semiconductor laser(SL)subject to continuous-wave(CW)injection holds a relatively large linewidth,due to the spontaneous emission noise.To enhance the P1 microwave,the filtered optical feedback(FOF)is deployed to the injected SL to suppress its spontaneous emission noise.Compared with the COF,the FOF can also optimize the purity of the P1 microwave and provide another way to tune the microwave frequency,not only reduct the linewidth.2.Three schemes for symmetric SKD based-on the chaos synchronizationTwo identical SL or cascaded semiconductor laser systems(CSLS)under the injection of common light can generated privacy synchronization.The first scheme is using the dynamical post-processing technology(DPPT)to the privacy synchronized chaos to dynamically achieve the symmetrical sampling and delayed exclusive-or(XOR).The DPPT can provide significant security enhancement since it can perform a dynamical encryption to the key extraction form the correlated entropy.Moreover,with the help of dual threshold sampling technology,the proposed key distribution can provide a relatively strong robustness to the synchronization error and the analog to digital converter(ADC)noise,which makes the bit error rate(BER)of the generated key meet the requirement of commercial optical communication network.The second is fulfilled by monitoring the quality of synchronization between the two CSLSs subject to the perturbations of random phase deployed in the legal communication partners.The investigation shows that,high-quality synchronization between the two CSLSs can only be achieved when the phase perturbations are well matched.The gap of synchronization with the phase matching and mismatching is evident enough to distinguish the two situations and extract the key from the perturbations of random phase.It is notable that the TDS induced by the optical feedback in CSLS is also well suppressed,therefore the information of the delay time is undetectable.The third one is the fast stream cipher generation based on the combination of the synchronized physical random number extracted from the privacy synchronized chaos,and the pseudo-random number generated by RC4 algorithm.The investigation shows that the generated stream cipher is non-correlated to the pseudo-random number and physical random number when their resolutions are matched.Besides,the BER of stream cipher is insensitive to the BER of the synchronized physical random number.3.Three schemes for the security enhancement of chaos-based secure communicationThe first one is the digital phase encryption of chaos-based communication by deploying identical digital phase modulated dual optical feedback to the master semiconductor laser(MSL)and slave semiconductor laser(SSL).With respect to the single phase modulated optical feedback scheme,the proposed scheme can suppress the TDS and expand key space greatly.The second one is the chaos-based communication with TDS suppressed by using the analog phase optical feedback.The output of MSL is used to generate the driving signal for the PMs in the external-cavity of MSL and SSL to ensure the high-quality chaos synchronization.The results show that the synchronization between MSL and SSL is more sensitive to intrinsic parameter mismatch and the phase modulation mismatch.Taking the TDS suppression into account,the security of chaotic secure communication is significantlly enhanced.The third one is the security enhancement scheme for the chaos-based communication system subject to common injection.By reversely injecting the chaos generated by the driven semiconductor laser SL1 and SL2 to the driver semiconductor laser(DSL),the the bandwidth of chaos in DSL is expanded and the TDS is also suppressed.In return,the bandwidths of the chaos in SL1 and SL2 are enhanced and the chaos synchronization becomes more sensitive to the parameter mismatching,due to the common injection.Therefore,the security of chaos-based communication is enhanced.