双向半导体光放大器(SOA)光纤环形混沌激光器输出波形呈帧型结构，相邻帧波形具有相似性且受到外界扰动时其相似性下降。为了获得相似性高且一致性好的混沌波形以准确检测扰动的发生，实验研究了影响该激光器相邻帧相似性的各种因素，包括SOA 性能及其驱动电流、系统结构的对称性、输出耦合比以及光纤环长。以相邻帧互相关峰值的平均值考察其相似性，最大偏差衡量其一致性。结果发现，具有偏振保持特性的光功率放大器(BOA)是最适合的有源器件，且其驱动电流越大，相邻帧相似性越好。只要调整偏振控制器使得输出混沌波形呈连续窄带谱的类正弦信号，则系统结构的对称与否、耦合比和光纤环长都不影响其相邻帧的相似性，但光纤环长却影响系统的灵敏度。考察了系统的工作稳定性，5 min 左右相邻帧相似性的波动在10-3 量级。

The output waveforms of a bidirectional optical fiber chaotic ring laser based on semiconductor optical amplifier (SOA) present frame structures. The adjacent-frame waveforms have the characteristic of similarity, which declines when the laser suffers an external disturbance. In order to obtain waveforms with high similarity and good consistency for accurate detection of disturbances, experimental investigations on various factors which can affect the adjacent-frame similarity of the laser are carried out, including the performances and drive current of SOAs, symmetry of system structure, output coupling ratios and optical fiber ring lengths. The similarity levels are investigated by the mean values of the adjacent-frame cross-correlation peaks. The consistency degrees are measured by the maximum deviation of the peaks. The results show that the booster optical amplifier (BOA) with the polarization-maintaining property is the most suitable active device. The bigger the drive current, the better the adjacent-frame similarity. By only adjusting polarization controller to make the output chaotic waveform look like sine signal with continuous narrow-band spectrum, the symmetry of system structure, coupling ratios and optical fiber ring lengths will not affect the adjacent-frame similarity. However, the ring lengths affect the system sensitivity. Moreover, the system stability is also investigated. The adjacentframe similarity fluctuates at 10-3 level within about five minutes.