针对传统光纤弯曲损耗位移传感器中位移与弯曲损耗的非线性关系,且高灵敏度和大量程不能兼得的问题,设计了一种U型缠绕式光纤弯曲损耗位移传感器,结构包括U型回绕和螺旋绕轴,两者合称为U型缠绕。理论证明被测位移量与光纤弯曲损耗之间的线性关系,推导出表达式,讨论了螺旋绕轴方式对光纤弯曲半径的影响和U型回绕方式对传感器精度的影响,并进行了一系列实验研究和性能测试。结果表明:传感器的测量范围为0~120 mm,灵敏度为0.14 dB/mm,线性相关系数大于0.99,光纤在U型缠绕中无应力松弛的现象,建议U型回绕光纤曲率半径大于6 mm。U型缠绕式光纤弯曲损耗位移传感器具有良好的测量精度和较大量程,能够实现传感器对混凝土结构的裂缝监测和大型结构位移的连续监测。

报道了一种全光纤结构的高消光比(PER)线偏振激光振荡器。该光纤激光振荡器的谐振腔由一段双包层掺镱保偏光纤和一对与增益光纤匹配的光栅组成。弯曲损耗使快轴方向上的偏振模和高阶模受到抑制，实现了消光比优于15 dB的线偏振激光输出。最高输出功率为93.2 W，中心波长为1080 nm，光谱半峰全宽(FWHM)约为1.2 nm。增加抽运功率有望进一步提升功率。

光纤激光的输出功率在十余年内迅速上升,目前连续输出的光纤激光功率已达千瓦以上。由于光纤纤芯可承受功率和光纤纤芯大小有关,而加大纤芯直径会降低光束质量,为了进一步提高光纤激光输出功率而不降低光束质量,一种方法是设计超大模场双包层光纤,加大光纤中低阶模的直径;另一种方法是加大光纤的纤芯直径,并用各种方法改进它的光束质量。对以上两种方法进行介绍,并给出一部分实验结果。

Coiling technique is used to control the transverse mode of a large-mode-area (LMA) multimode fiber laser. By winding the fiber to a coil with different radius, high-order modes of a multimode fiber laser are suppressed one by one and finally 15.4-W single-transverse-mode output is achieved when the coil radius is 20 mm. It is found that as the coil radius decreases, the beam quality of a multimode fiber laser gets better but the slope efficiency drops for higher-order modes are discriminated. During the experiment, as the coil radius of multimode fiber changes, output characteristic of the laser has been measured. Meanwhile, the mode loss of different modes is calculated theoretically. It is proved that the experimental measured results fit well with the theoretically calculated results.