Optical Secure Communication System Based On Dynamic Dispersion Management

Information security of Optical fiber transmission network is one of theimportant issues in the research of communication field. The secret communicationsystem encrypts the intended transmitted information before transferred in the channel,and then it decrypts the encrypted information received at the receiving end. So itguarantees that the users’ true information is not easy to be stolen by others. Thedynamic strong dispersion management’ security optical communication systemadjusts the dispersion of the light pulse signals of the encryptions fully anddynamically. Then the regulated information is transmitted synchronously through thesecret passage to the decryption part. In the decryption part, according to the secretkey information, it can compensate the accumulated dispersion precisely andsynchronously. Thereupon it fulfills the decrypt function and achieves the goal oftransferred secretly. The main contents are as follows:(1) According to literature review, this paper discusses the contemporary tuningdynamic dispersion and the development of the key technologies of secret opticalfiber communication. By analyzing their principles, the paper proposes that itcompletes the encryption function by broadening and deforming a wide range ofincident light signals according to the dynamic dispersion. The dispersioncompensation recovery process of initial signal waveform is decrypted. So,combining the dynamic strong dispersion management and secret communication,this paper puts forward a new security optical communication system;(2) The paper analyzes the principle of encryption and decryption on the basis of thenew secret optical fiber communication system. The relationship of speed andaliasing of different frequency components of carrying different dispersionoptical pulses will influence decryption. It formulates reasonable methods ofencryption and decryption through analogue simulation;(3) Various kinds of dynamic dispersion tuning technologies are introduced as anencryption and decryption scheme, and the principle is analyzed in details. Itpoints out the feasibility and constraints of the scheme. By contrast, it is feasible to combine the chirp fiber grating and the dispersion compensation fiber with theoptical switch respectively;(4) Numerical simulation of the NRZ, RZ and CSRZ transmission performance iscarried out, and their dispersion tolerance, nonlinear effect, the noise of EDFAresistance, PMD resistance have been compared and analyzed. The results provethat the RZ is more suitable for the new secret optical fiber communication withthe characteristics of high precision for dispersion management;(5) The results of the comparison and analysis of the line dispersion managementscheme indicate that the symmetrical dispersion management plan is the best andits quality of transferring signals is the best. The logical allocation of the powerand RZ pulse rate plays a positive role in optimizing the system.(6) The combination of the dispersion compensation fiber and optical switch can beused to fulfill the dynamic encryption and decryption in the symmetry ofdispersion compensation transmission system. It also finds that the scope oftuning dispersion is limited mainly by its damage of nonlinear effect.(7) The encryption and decryption of chirp fiber grating and optical switch are theimprovements of the dispersion compensation fiber by increasing the tuningrange. Dispersion controlling and upgrading the transmission rate can reduce thescope of dispersion compensation to improve the safety of the decryption. Thesecond method is the best as it can combine the safety of decryption and the highquality signal transmission together.