Robust low-loss optical fiber joints are a prerequisite in all-fiber devices. Joining structurally dissimilar fibers, such as microstructured optical fibers, is a timely challenge, as they are becoming important building blocks in photonics. In this paper we have revealed the mechanism of robust mode matching and demonstrated ultralow loss and high strength fusion splices between ultralarge mode-area photonic crystal fibers (ULMA-PCFs) and standard single mode fibers (SMFs) without using any intermediate bridging elements. To provide precise matching in both the mode field distribution and the cladding size between an SMF and an ULMA-PCF, we develop a two-step reverse tapering approach, involving reverse tapering an SMF and thermally expanding its core, where the fundamental mode can be adiabatically transferred and reach the optimized mode shape in the tailored reverse-taper. Using our new tapering approach, we achieve a record-low splice loss of 0.23 dB, regardless of the transmission direction, together with a mechanical strength an order of magnitude higher than that of a conventional sharp-edge joint. Our approach provides an effective way to overcome the splicing challenge for ultralarge mode specialty fibers and thus greatly facilitates the development of components and devices with such fibers.

中文翻译：

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结构不同的光纤波导之间的稳健模式匹配

坚固的低损耗光纤接头是全光纤设备的先决条件。连接结构不同的光纤（例如微结构光纤）是一个及时的挑战，因为它们已成为光子学中的重要组成部分。在本文中，我们揭示了稳健的模式匹配机制，并展示了超大模态面积光子晶体光纤（ULMA-PCF）与标准单模光纤（SMF）之间的超低损耗和高强度熔接，而无需使用任何中间桥接元件。为了在SMF和ULMA-PCF之间的模场分布和包层尺寸方面提供精确的匹配，我们开发了一种两步反向渐缩方法，其中包括反向渐缩SMF并热膨胀其芯，可以绝热地传递基本模式，并在量身定制的倒锥中达到最佳模式形状。使用我们的新的渐缩方法，无论传输方向如何，我们都可以实现创纪录的0.23 dB的熔接损耗，并且机械强度比传统的尖锐接缝高出一个数量级。我们的方法为克服超大型特种光纤的熔接难题提供了有效的方法，因此极大地促进了使用此类光纤的组件和设备的开发。