包层抽运光纤激光器是大功率激光器的研究热点,而双包层光纤的抽运光吸收系数的准确测量,对于稀土掺杂包层抽运光纤激光器的设计至关重要。从光纤中沿长度方向模式分布的角度理论上分析了如何准确测试包层抽运光纤的吸收系数,采用几种不同的方法对具有五边形内包层结构、低折射率材料作为外包层的双包层掺镱光纤的吸收系数进行了测试和分析。要准确测量包层抽运光纤的吸收系数,就必须采用多模光纤作为参考光纤,在注入双包层光纤之前,使抽运光具有尽可能多的模式。实验测试和理论分析结果表明,经过几米距离之后抽运吸收系数将变成线性。抽运光在双包层光纤中的吸收是一个非线性到线性的过程。

Rare-earth doped cladding pumped fiber for high power laser has attracted great interest,and the measurement of the pump absorption coefficient of the rare-earth doped double clad fiber is important for the design of cladding pumped high power optical fiber laser. To acquire the accurate pump absorption coefficient of the double clad optical fiber,measurement methods are talked about rely on the mode distribution along the length of fiber. Some methods are carried out to measure and analyze the double clad ytterbium doped fiber with pentagon inner cladding and low refractive index polymer as second cladding. To precisely measure the pump coefficients of the cladding pumped fiber,the multi-mode optical fiber must be used as reference fiber for acquiring more modes before injecting into the double clad fiber. The result from the theory analysis and experimental measurement shows that the pump absorption is a process from nonlinear to linear. The pump absorption coefficient of the beginning segment is larger than the next segment,and the pump absorption coefficient will be linear along the optical fiber after some meters length fiber.