为改善光纤通信系统带宽容量在实际工程应用中面临的局限性，基于空分复用技术提出一种可分别传输基模与高阶模的光子晶体光纤纤芯结构，利用虚轴光束传播法得到不同结构参数下相应模式的有效折射率曲线，通过匹配两种模式的有效折射率曲线，设计了一种具有非对称双芯结构的光子晶体光纤模式转换器。光波长为1550 nm时，该器件实现了基模（LP₀₁模）与高阶模（LP₀₂模）之间的模式转换，在较宽的归一化频率范围内模式耦合效率可达91.98%，耦合长度约178.5 μm，器件直径最大仅47.6 μm。该结构设计灵活可控，可满足未来大容量通信系统的需求。

To improve limitations of bandwidth capacity of optical fiber communication system in practical engineering applications, a photonic crystal fiber core structure which is capable of transmitting fundamental and high-order modes is proposed based on space division multiplexing technology. The effective refractive index curves of the corresponding modes under different structural parameters are obtained using the finite-difference imaginary-distance beam propagation method. An asymmetric dual-core photonic crystal fiber mode converter is designed by matching the effective refractive index curves of the two modes. It demonstrates that such an LP₀₁-to-LP₀₂ mode converter can be achieved at the wavelength of 1550 nm. In a wider frequency range, the mode coupling efficiency is above 90%, and the coupling length is about 178.5 μm. The device diameter is 47.6 μm, and the structural design is flexible and controllable, which can meet the needs of future large-capacity communication systems.