基于衍射理论推导出多芯双包层光纤激光器的远场相干光光强理论模型，并在此基础之上，系统地分析比较了纤芯不同排布方式的合束效果，重点研究了纤芯的单层圆环排布、多层圆环排布、方形排布、正六边形堆积排布4种方案的合束效果，及在一定纤芯排布下纤芯直径、纤芯轴间距、出射平面与衍射平面间距离、波长对合束效果的影响。研究发现：在纤芯数目一定的情况下，单层圆环排布的合束效果最优，其次是方阵排布；纤芯数目越多，截面利用率越高，可获得更大合束最大光强；方阵排布方式及正六边形堆积排布方式可有效提高截面利用率；增大纤芯直径，减小纤芯轴间距、减小出射平面与衍射平面间的距离、减小波长可以获得更好的合束效果。

Based on diffraction theory, this paper deduces the equation of coherent beam intensity in far-field of with multi-core double-clad fiber. The effects of different fiber core arrays, especially single ring array, multilayer rings array, rectangular array and hexagon array, on the final quality of beam combination are investigated. The effects of different parameters including core diameter, core space, the distance between output plane and diffraction plane and wavelength are also studied. Numerical results demonstrate that, for given core number, single ring array is the best scheme among the above four core array in order to realize high quality beam combination, and the next one is rectangular array. Increasing core number can increase cross section utilization ratio，thus producing higher maximum laser intensity. Both rectangular array and hexagonal array can improve using efficiency of the fiber cross section.Moreover, higher laser intensity can be obtained through increasing core diameter, decreasing core space, decreasing the distance between output plane and diffraction plane and decreasing wavelength.