In this paper, we design a novel type of photonic crystal fiber (PCF) with a kind of typical micro-structure in its innermost cladding area, which can totally transmit 26 orbital angular momentum modes (OAMs). Over a bandwidth of 300 nm from 1.5 to 1.8 μm, this new type PCF shows a great improvement in dispersion property when it is compared with the total internal reflection PCF for reference. Moreover, other mode properties are also calculated and listed in curves, including effective indices, confinement loss and nonlinear coefficient. And basing on the test results, we further ameliorate the micro-structure and cladding of previous PCF structure and propose two effective ways to reduce the dispersion and confinement loss respectively. One is to insert typical type of micro-structure; the other is to change the arrangement and size of air holes in the cladding area. We finally propose an optimized structure which can support 30 OAM modes with the application of the two ways. Results show the optimized structure performs very well and achieves great progress in terms of dispersion and confinement loss.

中文翻译：

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用于轨道角动量模式传输的低色散和限制损耗光子晶体光纤

在本文中，我们设计了一种新型光子晶体光纤（PCF），其最内包层区域具有一种典型的微结构，可完全传输 26 个轨道角动量模式（OAM）。在从 1.5 到 1.8 μm 的 300 nm 带宽上，这种新型 PCF 与参考的全内反射 PCF 相比，其色散性能有了很大的改善。此外，还计算并在曲线中列出了其他模式属性，包括有效指数、限制损耗和非线性系数。并基于测试结果，我们进一步改善了先前PCF结构的微观结构和包层，并提出了两种分别降低色散和限制损失的有效方法。一是插入典型的微结构类型；另一种是改变熔覆区气孔的排列和尺寸。我们最终提出了一种优化的结构，可以通过两种方式的应用支持30种OAM模式。结果表明，优化后的结构性能非常好，在分散和约束损失方面取得了很大的进步。