Study On Time-Delay Signature And Bandwidth In The Chaotic Injection System Of Semiconductor Lasers

Over the last fifty years,optical communication has been become one of the most useful communication methods in the era of internet.With the rapid development of integrated services digital network(ISDN),the information security becomes more and more important.The chaotic security communication,generated by the semiconductor lasers,has attracted considerable interest on the area of information security all over the world,since it employs the hardware as the key infrastructure,and it can be easily expanded in the all-optical communication network.Usually,the semiconductor lasers have the stable output,but,via adding some degree of freedom,the SLs exhibit rich dynamical behaviors,such as the complexity bandwidth enhanced chaos signals.Besides,the chaotic signals are considered as the perfect entropy of random number generator(RNG),due to its widely bandwidth and good performance of randomness.However,the external factor will bring some harmful things.For instance,the time delay signature(TDS)caused by external-cavity semiconductor lasers(ECSLs)leads to the week periodicity in the output of chaotic signals.As a result,the attacker can extract the TDS via some mathematic methods,and then the technique of three dimensional re-constructions can make up the same system.Moreover,the TDS can also reduce the randomness of RNG.This work concentrates on the TDS and bandwidth of chaotic system,in accordance with the great demand and hotspot of information and cyber security.The TDS and the bandwidth of chaotic injection system are numerically demonstrated in detail.We suppressed the TDS of chaotic signals via designing chaotic structure and choosing the suitable parameters,while the bandwidth of the chaos also expanded.The experiment is carried out to generate the high speed RNG.This thesis discusses the chaotic properties and the concealment of TDS in the chaotic system.Meanwhile,the system for extracting the random bit from the chaotic signals is designed.The main innovation work and achievements are summarized as follows:Numerically simulations demonstrate the properties of time-delay signature and bandwidth of the ECSLs subjected to the phase-conjugate feedback(PCF).The conventional optical feedback(COF)is also studied in parallel for comparison,while the difference of chaotic dynamics between these two feedback types is also discussed.The model of the combined mechanism of PCF and optical injection chaotic system(OICS)is proposed,wherein both of them have the advantages of TDS suppression and bandwidth enhancement.Comparing with the combination of the COF and the OICS,the widely parameter region can be obtained where the system has bigger bandwidth and smaller TDS value.Via the studying of system parameters and SL parameters,the index of the chaotic injection system subjected to PCF is curtained,which has certain practical applications.The bandwidth of dual-path optical injection system used SLs(DPOI-SL)is investigated in detail.The impact of injection parameters on the bandwidth is considered.The bandwidth of DPOI-SL is three times than that of the conventional single-path optical injection system(SPOI-SL).Besides,the principle of synchronization is analyzed,while the complete synchronization between different slave-semiconductor lasers(SSL)is achieved by changing the structure of DPOI-SL.The dependence of chaos synchronization on parameter mismatch and the detuning confirms the feasibility and the privacy of the proposed schemes.The multiplexing communication in the chaotic unidirectional injection system is achieved by the means of active-passive duplexing(APD).The conventional multiplexing communication system has the disadvantage that,even the master semiconductor laser(MSL)and SSL have good performance of chaotic synchronization,the interference between different pairs of MSL and SSL still exists,which effects the quality of communication.The better parameters are chosen via the selecting the parameter mismatch factor.Comparing with the conventional multiplexing system,the designed system has more complex TDS,and the security of the chaotic communication system is enhanced.The delay characteristics of the laser chaotic injection system are studied numerically and experimentally.Then,the two-chaotic unidirectional optical injection system is designed.The TDSs associated with the dynamics of master lasers or only one of the two TDSs can be concealed in the SSL with DCOI based on the choices of the injection ratio and the frequency detuning of the two injection lights.As a result,the bandwidth is enhanced.Besides,while this DCOI-SL system are used as the entropy of the physical random number generator(Phy-RNG),the high-speed random bit sequences with the bit rate of 160 Gbit/s are obtained experimentally,and they passed the NIST(SP 800-22)test.The effects of the internal parameters(i.e.,linewidth-enhancement factor and gain nonlinearity)on the chaos TDS concealment in MCSLs are investigated in detail and the relation between TDS and the nonlinearity of SLs is revealed.The results shows that,the linewidth-enhancement factor affects the nonlinearity dynamics of the SL uncomely and reduces the TDS.As a suitable value selected,the gain nonlinearity can improve the TDS value and characterizes the nonlinear term of the SLs.The dynamics of free-running and optically injected VCSELs are numerically studied.The powerful measurements including the 0-1 test for chaos and permutation entropy are used for locating the chaotic dynamics in a free-running VCSEL,which illustrate the effects of some key parameters on the chaotic region.In order to enhance chaotic dynamics,the output of the free-running VCSEL(master)is injected to another free-running VCSEL(slave).The results show that the chaotic dynamics of the slave VCSEL can be greatly enhanced,i.e.,both the bandwidth and complexity,while this occurs only outside of the injection locking region where the correlation between the mater and slave lasers is low.To take advantage of these enhanced chaotic dynamics exhibiting extremely high complexity and broadband bandwidth,a three-laser synchronization scheme is proposed and demonstrated.