Single-mode fiber coupler with variable coupling ratio is a flexible tool for optical fiber applications. Here we demonstrate a microfiber based coupler with compact size and wide tuning range. The coupler consists of two identical single-mode microfibers that are fabricated via parallel pulling process. By adjusting the twisting angle between these microfibers, the coupling ratio varies from 3.15% to 98.5% due to the change of evanescent field interaction length. Numerical simulations are carried out and the results agree well with the experimental ones. The effects of diameter discrepancy between two microfibers and mode polarization are also studied experimentally and numerically.

中文翻译：

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基于微光纤的紧凑型可变单模光纤耦合器的实验演示


具有可变耦合比的单模光纤耦合器是光纤应用的灵活工具。在这里，我们展示了一种基于微光纤的耦合器，具有紧凑的尺寸和宽的调谐范围。该耦合器由两根相同的单模微光纤组成，通过平行拉伸工艺制造。通过调节这些微纤维之间的扭转角度，由于倏逝场相互作用长度的变化，耦合比从3.15%变化到98.5%。进行了数值模拟，结果与实验结果吻合较好。还通过实验和数值研究了两根微纤维之间的直径差异和模式偏振的影响。