A switchable and tunable ytterbium-doped fiber ring laser (YDFL) is reported and demonstrated. Employing a Sagnac loop mirror fabricated by an 85-cm-long polarization-maintaining fiber (PMF), the proposed YDFL can operate with stable dual-wavelength lasing or tunable single-wavelength lasing around 1 064 nm. Both stable dual-wavelength lasing and tunable single-wavelength lasing are achieved by adjusting a polarization controller in the Sagnac loop mirror. The experimental results show that the output of the proposed fiber laser with two different operation modes is rather stable at room temperature.

针对传统K-均值算法容易受到野点和噪声点的影响，缺乏鲁棒性的问题，提出了一种基于协同熵的K-均值算法。该方法利用协同熵作为一种局部的相似度度量手段，并依赖最大协同熵准则进行最优聚类中心的求解。采用迭代重加权的优化算法可以用来快速实现最优聚类中心的求解。对于残差较大的野点和噪声，它们在聚类中心更新的过程中将被赋予较小的权重。实验结果表明，基于协同熵的K-均值算法具有较好的鲁棒性，并获得较好的聚类效果。