Orbital angular momentum (OAM), inherent to light beams characterized by helical phase fronts, represents an alternative spatial degree of freedom for photons. In recent years, OAM-based communication has gained significant attention as a potential solution to increase the capacity and spectral efficiency of optical fiber communication systems. In optical fibers, OAM modes can be generated and manipulated by utilizing specialized optical components and techniques. One approach involves using specially designed optical fibers, such as ring–core fibers, which have the capability to support multiple OAM modes. In the manufacturing process, the ring fiber is hardly made perfectly, especially the doped-cores. The introduced defect breaks the symmetry of the ring–core, which has a serious impact on OAM mode transmission. Using a material with a slightly higher refractive index than the cladding to wrap the ring–core is effective in reducing impairment of defects. After numerical simulation, the proposed method improves the walk-off length by a factor of 2–40.

中文翻译：

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利用不完美环芯光纤改善轨道角动量模式传输

轨道角动量 (OAM) 是具有螺旋相锋特征的光束所固有的，代表了光子的另一种空间自由度。近年来，基于OAM的通信作为提高光纤通信系统容量和频谱效率的潜在解决方案受到了广泛关注。在光纤中，可以利用专门的光学元件和技术来生成和操纵 OAM 模式。一种方法涉及使用专门设计的光纤，例如环芯光纤，它能够支持多种 OAM 模式。在制造过程中，环形光纤很难做到完美，尤其是掺杂纤芯。引入的缺陷破坏了环芯的对称性，这对OAM模式传输产生严重影响。使用折射率比包层稍高的材料包裹环芯可有效减少缺陷损害。经过数值模拟，所提出的方法将走离长度提高了 2-40 倍。