本文基于自相关及排列熵函数实验研究了掺铒光纤环形激光器混沌序列的复杂度。通过控制腔内损耗来实现光纤激光器不同的混沌态输出，并对其复杂度进行详细分析。实验结果表明：腔内损耗对混沌复杂度影响较大，随着腔内损耗的增大，其排列熵复杂度逐渐变大；自相关曲线上表现出的腔长时延信息也得到有效抑制。通过腔内损耗控制，混沌序列的周期性被完全隐藏，其复杂度达到最大值，这能有效地提高混沌保密通信的安全性，混沌传感和测距的测量精度。

The complexity of the erbium doped fiber ring lasers is experimentally investigated based on the autocorrelation function and permutation entropy function. By controlling the loss in the ring cavity, the different chaotic complexity is analyzed in detail. The experimental results show that the intra-cavity loss has great effect on the chaotic complexity of fiber laser. With increase of the loss, the permutation entropy complexity increases gradually and the time- delay signature shown in the autocorrelation curves can also be suppressed. By controlling the intra-cavity loss, the time-delay signature of chaos is completely hidden and its permutation entropy complexity reaches a maximum, which can effectively improve the security of chaotic secure communications and the measurement precision of chaotic sensing or ranging.