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为了评判偏振态移位键控(PolSK)光混沌通信系统的保密性强弱,先要验证它的混沌特性,因此对该系统的信号进行了分析。利用三种方法判定该信号是否具有混沌特性:在三维相空间观察奇异吸引子;分别从最大李氏(Lyapunov)指数满足的方程出发以及wolf法计算其最大李氏指数;并计算其自功率谱密度函数。结果明显观察到奇异吸引子,算得最大李氏指数分别为0.0364和0.0106,都大于零,自功率谱为噪声背景、宽峰的连续谱;从而判定该系统传输的信号确实是混沌信号。另一方面,用最小伪邻点算法计算该系统信号的嵌入维数,结果达到6维,说明该系统具有中高维度混沌特性;结合系统的抗攻击性分析,得出结论:相比于一般的混沌掩盖方案,该系统具有较强的保密性和安全性。
In order to evaluate the confidentiality of the PolSK optical chaotic communication system, its chaotic characteristics must be verified first, and the signal of the system is analyzed. Three kinds of methods are used to determine whether the signal has the chaos characteristic: the singular attractor is observed in the three-dimensional phase space; the maximum Lyse index is calculated from the equations satisfied by the maximum Lyapunov exponent and the maximum Lee’s exponent calculated by the wolf method; Density function. The results show that the singular attractors are obviously observed, and the largest Lee’s index is 0.0364 and 0.0106, respectively, which are both greater than zero. The self-power spectrum is a noise background and a broad spectrum of continuum; therefore, the signal transmitted by this system is indeed a chaotic signal. On the other hand, the embedding dimension of the system signal is calculated with the minimum pseudo-neighbors algorithm, and the result reaches six dimensions, indicating that the system has chaos characteristics of medium and high dimensions. Combining with the analysis of the system’s anti-aggression, it is concluded that compared with the general Chaos masking scheme, the system has strong confidentiality and security.