Time Delay Signature Analysis Of Semiconductor Laser Chaotic System And Its Application In Secure Communication

With the advantages of high speed,low loss and large capacity,optical fiber communication has become an important carrier and backbone facility of network information,covering all fields of the global economy.However,in the process of information transmission,there are many risks,such as eavesdropping,impersonation and deception from illegal receivers.Therefore,it is necessary to encrypt the information transmitted in the optical fiber.Optical chaotic secure communication is based on the hardware encryption of the physical layer.With the advantages of noise-like,aperiodic and non-long-term prediction of chaotic signals,the information is hidden in the chaotic signal and transmitted.The transmitted information is demodulated at the receiver by the chaotic signal synchronized with the transmitter.It has excellent application prospects in the field of secure communication.Based on the research of optical chaotic secure communication systems carried out by predecessors,from the perspective of improving system security,this paper hides the time delay signatures in the system through different schemes and structural designs to ensure safer communication.The main contents and results of this paper are as follows:（1）An electro-optic intensity chaotic communication system is simulated by MATLAB and Opti System.The system has two parallel electro-optic delay feedback loops.Firstly,the scheme performs numerical analysis on the system,evaluates the randomness of the chaotic signal generated by the system,analyzes the synchronization and robustness of the system,and simulates the encryption and decryption process of the signal.The numerical simulation results show that the scheme is feasible and that the performance of the chaotic system is consistent with the theoretical value.In addition,through the co-simulation of MATLAB and Opti System,the scheme can design virtual devices according to the users’wishes,which is of great significance to the research and development of new optoelectronic devices.（2）An improved traditional external cavity optical feedback method is proposed.An all-optical time-delay feedback loop is designed by replacing the traditional external cavity with an erbium-doped fiber amplifier,which overcomes the shortcomings of high precision and a large volume of the traditional method.The communication scheme of bidirectional transmission is further designed,and two sets of binary information are input into the system.The introduction of information makes the output waveforms at both ends constantly switch between synchronous and asynchronous.The encrypted information is transmitted to the other end through the channel.After subtracting from the local encrypted information,the synchronous power error of the two ciphertext information is obtained.After taking the absolute value,the opposite side sending information can be recovered by XOR operation with the local information.In addition,this scheme only sets the encryption device at the transmitter and uses the correlation between the two encrypted signals for decryption,omitting the decryption device at the receiver.Based on simplifying the experimental equipment,this scheme solves the problem that the receiving end cannot decrypt synchronously due to the damage of the channel during remote communication,and it is easy to be used in production and life.Finally,the scheme successfully realizes the bidirectional transmission of 10Gb/s information over 85km single-mode fiber under the bit error rate of less than 10^-5.（3）A multi-mode（unicast,multicast and broadcast）optical chaotic secure communication system with multi-dimensional keys and complex entropy source is proposed.The system uses amplified spontaneous emission noise generated by an erbium-doped fiber amplifier to replace the traditional continuous wave as a complex entropy source.The phase intensity chaotic carrier is generated through a dispersion-induced device and electro-optic time delay feedback loop.The plaintext information is double-masked in the phase field and intensity field.A frequency-dependent group delay module is introduced into the electro-optic time delay feedback loop to hide the time delay signatures of chaotic signals and enhance system security.In addition,the problem of system decryption function degradation caused by different hardware parameter mismatches is also studied.With the help of wavelength converters and wavelength division multiplexers,the system can realize secure communication in multiple modes（unicast,multicast and broadcast）simultaneously to improve the system’s transmission efficiency and has a wide range of application scenarios.（4）Based on the chaotic shift keying theory,a secondary encrypted semiconductor laser chaotic communication system with an optical injection structure is proposed.This system uses a distributed feedback laser with a single optical feedback structure as the driving laser.By switching the responding laser with a double dispersion feedback structure connected to the driving laser as the information feeding method,chaotic coding is realized to avoid the direct transmission of information into the channel.The chaotic phase scrambling technology is used for secondary encryption.The spectrum-broadening effect of chaotic phase scrambling technology can effectively improve the efficiency of secure transmission.In addition,the system can effectively resist the return map attack and show robustness in dealing with the noise of digital signals.The results show that the system can achieve high-quality,secure communication with a low signal-to-noise ratio of as low as 10d B.