Experimental and numerical studies of spatiotemporal femtosecond soliton propagation over up to 1 km spans of parabolic graded-index fibers reveal that initial multimode soliton pulses naturally and irreversibly evolve into a single-mode soliton. This is carried by the fundamental mode of the fiber, which acts as a dynamical attractor of the multimode system for up to the record value (for multimode fibers) of 5600 chromatic dispersion distances. This experimental evidence invalidates the use of variational approaches, which intrinsically require that the initial multimode propagation of a self-imaging soliton is indefinitely maintained.

中文翻译：

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多模GRIN光纤中的单模时空孤子吸引子

时空飞秒孤子在长达1 km的抛物线渐变折射率光纤上传播的时空实验和数值研究表明，初始的多模孤子脉冲自然且不可逆地演化为单模孤子。这是由光纤的基本模式承载的，该基本模式充当多模系统的动态吸引子，对于高达5600色散距离的记录值（对于多模光纤）。该实验证据使变分方法的使用无效，这本质上要求无限期地保持自成像孤子的初始多模传播。