采用全矢量的方法，数值求解了内包层为左手材料，纤芯和外包层为常规材料的W型弱导双包层光纤的特征方程，分析了其模式分布、色散和时延特性。结果表明内包层为左手材料的双包层光纤具有许多不同于常规光纤的反常特性：单模传输模式只存在于特定的频率范围内；随着内包层负折射材料厚度的增加，同一模式同一频率下出现不同的传播常数；内包层厚度对单模的色散和群时延影响巨大，通过增大内包层厚度，可以达到-158000 ps/(nm·km)大负色散及极大的群时延。这些结果为设计新型色散补偿光纤及新型光纤器件提了供理论基础。

The characteristic equation of a doubly cladding fiber with an inner cladding made of negative refractive index material is presented by full vectorial mode method. Its mode distribution, dispersion and time delay are demonstrated. The results indicate that this kind of fiber has some abnormal properties, such as the single mode existing in certain normal frequency. Along with increasing diameter of inner cladding, different propagation constants exist in the same mode and normalized frequency. The diameter of inner cladding has great influence on the dispersion and group time delay. The dispersion can reach -158000 ps/(nm·km) and group time delay can become very large by increasing the diameter of the inner cladding. These results provide theoretical basis for designing novel dispersion compensating fiber and photonic devices.