为更好地解决少模光纤在传输中由于模式耦合过强而导致的信号串扰问题，对弱耦合光子晶体光纤中的线偏振（LP）模式以及矢量模的传输特性进行了研究，设计了一种可传输20种矢量模的双包层光子晶体光纤。通过有限元法模拟光纤参数对相邻LP模式间最小有效折射率差的影响，优化结构参数，使光纤支持稳定传输6种LP模式并满足弱耦合要求。最后分析了不同模式的有效模场面积、弯曲损耗。结果表明：各模式之间的最小有效折射率差达到1.12×10⁻⁴，表明模式间的串扰可忽略。基模有效模场面积达到了1040 μm²，且其相应的非线性系数低至1.07×10⁻¹⁰。此外，在弯曲半径为38 mm时，各模式弯曲损耗最大仅为5.65×10⁻⁸ dB/km。与主流的单模光纤及少模单包层相比，该结构具有大模场面积，低模间串扰及更强的抗弯曲能力，丰富了空分复用技术的开发思路。在大数据、虚拟现实、网络传输容量等新兴业务以及光纤传感方面提供了有益的参考方案。

To better solve the problem of signal crosstalk caused by mode coupling in the transmission of few mode optical fiber, the transmission characteristics of linear polarization (LP) mode and vector mode in weakly coupled photonic crystal fibers were studied. A double clad photonic crystal fiber has been designed that can transmit 20 vector modes. The effect of fiber parameters on the minimum effective refractive index difference between adjacent LP modes was simulated using finite element method to optimize the structural parameters, allowing the fiber to support stable transmission of six LP modes, which meets the weak coupling requirements. Finally, the effective mode field area and bending loss of different modes were analyzed. The results show that the minimum refractive index difference between the modes of the fiber is more than 1.12×10^-4, indicating that the crosstalk between the modes is negligible. Effective mode field area of basic mode reaches 1040 μm², where the corresponding nonlinear coefficient is as low as 1.07×10^-10. In addition, at the bending radius of 38 mm, the maximum bending loss of each mode is only 5.65×10^-8 dB/km. Compared with mainstream single-mode fiber and few mode single cladding, this structure has larger mode field area, lower inter mode crosstalk and stronger bending resistance, enriching the development ideas of space division multiplexing technology. It provides useful reference solutions for emerging services such as big data, virtual reality, network transmission capacity and optical fiber sensing.