We present the design, fabrication, and characterization of a highly nonlinear few-mode fiber (HNL-FMF) with an intermodal nonlinear coefficient of 2.8 (W·km)−1, which to the best of our knowledge is the highest reported to date. The graded-index circular core fiber supports two mode groups (MGs) with six eigenmodes and is highly doped with germanium. This breaks the mode degeneracy within the higher-order MG, leading to different group velocities among corresponding eigenmodes. Thus, the HNL-FMF can support multiple intermodal four-wave mixing processes between the two MGs at the same time. In a proof-of-concept experiment, we demonstrate simultaneous intermodal wavelength conversions among three eigenmodes of the HNL-FMF over the C band.

中文翻译：

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高度非线性少模光纤的设计、制造和表征

我们介绍了高度非线性少模光纤 (HNL-FMF) 的设计、制造和表征，其模间非线性系数为 2.8 (W·km)−1，据我们所知，这是迄今为止报道的最高值. 渐变折射率圆形纤芯光纤支持具有六个本征模式的两个模式组 (MG)，并且高度掺杂锗。这打破了高阶 MG 内的模式简并，导致相应的本征模式之间的群速度不同。因此，HNL-FMF 可以同时支持两个 MG 之间的多个模间四波混合过程。在概念验证实验中，我们展示了 C 波段上 HNL-FMF 的三个本征模式之间的同步模间波长转换。