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。

For judging the security of the chaos optical communication system employing the polarization-shift keying (PolSK) modulation technology, its chaos characteristic needs to be verified above all. So analysis is done for the signal of this system. Three methods are used to judge the signal maintaining chaos characteristics or not: watching the strange attractor in three-dimensional phase space, computing the largest Lyapunov exponent by the equation it meets and wolf method, and computing self-power spectrum density function. As a result, the strange attractor is clearly watched, the largest Lyapunov component is positive 0.0364 and 0.0106, respectively, and the self-power spectrum is wide and continuous with the noise background. Therefore, the judgment of chaos for the signal transmitted in the system is presented. On the other hand, the minimal embodied dimension of the signal is given by the false nearest neighbours (FNN) method and it reaches 6, which shows the higher dimension chaos characteristics of the system. Adding the analysis of the ability of anti-attack for the system, it is concluded that the system owns higher security than the normal chaos masking schemes.