开环全光混沌通信系统中的光纤信道结构

Structure of Fiber Channel in Open-loop All-optical Chaotic Communication System

根据外光反馈半导体激光器及光纤传输方程,构建了基于光纤信道的开环全光混沌通信系统.考虑混沌调制和混沌键控两种信息加密方法,采用先进的校正相减解调法恢复信息,并且通过解调Q因子衡量系统性能.以不同次序排列单模光纤和色散补偿光纤构成4种结构的光纤信道,通过数值仿真分析信道结构对系统通信性能的影响.结果表明,为光纤信道保留少量的负累积色散有利于改善远程传输性能;两端补偿和中间补偿这两种对称结构的性能一致,对称结构优于非对称结构即预补偿和后补偿,适用于远程高速开环全光混沌通信.另外,无论光纤信道结构怎样,在远程高速激光混沌通信中混沌调制方法总是优于混沌键控方法.

The open-loop all-optical chaotic communication system based on a fiber channel is established according to the equations of semiconductor laser with external feedback and fiber transmission.Two encryption methods for message,i.e.chaotic modulation and chaotic shift keying are considered.The advanced adjusted subtraction demodulation method is used to recover the encrypted message.Meanwhile,the performance of the system is measured by the decoding Q factor.Four kinds of fiber channel are constructed by setting single mode fiber and dispersion compensation fiber in different orders.The influence of the structures on the communication performance of the system is analyzed by numerical simulation.The result indicates that reserving a small negative accumulated dispersion in the fiber channel helps to improve the performance of remote transmission.The two symmetrical structures,i.e.middle and two-side compensations,have similar performances.The Symmetrical structures are superior to the asymmetrical structures,i.e.,anterior and posterior compensations,and therefore suitable for the application of remote and high-speed open-loop all-optical chaotic communications.In addition,the chaotic modulation method is always superior to the chaotic shift keying method for the remote and high-speed chaos laser communication whatever the structures of the fiber channel are.