提出了一种基于三芯光子晶体光纤的定向耦合器。通过增大纤芯两侧空气孔直径来引入非对称纤芯，该方法有效地实现了1×3分束的目的。数值分析表明，该三芯光子晶体光纤定向耦合器的工作带宽可达113.9 nm（具体为波长从1530.9~1644.8 nm）且均匀性小于0.4 dB、偏振相关损耗低于0.2 dB。此外，这种结构能够有较大的制作容差，具体表现为器件长度在光纤长度（20.9 mm）的±4%范围内变化都能保证工作带宽不小于80 nm。

A design for a novel broadband directional coupler (1×3) based on an asymmetric three-core photonic crystal fiber (PCF) is proposed. The asymmetry core in the fiber is introduced by the enlargement of air holes in three-core PCF. Numerical investigations demonstrate that the operating wavelengths of the novel broadband coupler range from 1530.9 to 1644.8 nm. The uniformity is less than 0.4 dB and polarization-dependent loss is less than 0.2 dB. In addition, the proposed coupler shows large tolerance to the fiber parameters. In particular, the coupler with at least ±4% derivation of the fiber length (20.9 mm) can ensure that the work bandwidth is not less than 80 nm.