双包层光纤中的包层光不仅会影响到其输出激光的光束质量，还会对光学器件造成损坏。分析了被动双包层光纤中产生包层光的几种原因。通过在双包层光纤激光器的输出端引入产生包层光的不同要素，使用功率和光场分布检测等手段，实验研究了被动双包层光纤之间的熔接质量和模场失配以及无源光学器件的插入对于包层光产生的影响。实验结果表明，被动双包层光纤之间的低质量熔接和模场失配会导致纤芯基模与包层模式发生耦合，光纤合束器会激发高阶泄漏模式导致信号光泄漏到包层中，光纤隔离器会将部分信号光耦合到输出尾纤的包层中，从而导致包层光的产生。讨论了为抑制包层光的产生和减小包层光的影响应注意的事项和采取的措施。

The cladding light in double clad-fiber laser will not only affect the laser beam quality, but also damage the optical devices. The reasons of the generation of cladding light in the passive double-clad fiber are analyzed, and the influence of these reasons on the cladding light generation is studied experimentally by the method of power and optical field distribution detection. The results indicate that, low-quality splices and mode field mismatch between the passive double-clad fibers would raise the coupling between fundamental mode and cladding modes, while the fiber combiner and isolator would lead to the leakage of light from the core to the cladding, which results in the generation of cladding light. Notes of restraining the generation and reducing the influence of cladding light are discussed.