We report a method for the characterization of the higher-order modes in polarization-maintaining multimode optical fibers using a Bragg grating. We evaluate a 400 µm diameter, polarization-maintaining higher-order-modes fiber by inscribing a Bragg grating, resonant at the wavelength $\lambda \sim {1067}\;{\rm nm}$. By comparing the reflection spectra of the light polarized along the slow and the fast axes of the fiber and using the derived mathematical relations, we estimate the birefringence and the polarization-extinction ratio of the various higher-order modes in the fiber. This represents a simple and attractive approach for a detailed investigation of the multimode polarization-maintaining fibers that are emerging as an invaluable tool for advanced manufacturing, defense, bio-imaging, and telecommunications systems.

中文翻译：

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通过布拉格光栅对大面积，保持偏振态的高阶模光纤的偏振和模态分析

我们报告了一种使用布拉格光栅在保偏多模光纤中表征高阶模的方法。我们通过刻画在波长$ \ lambda \ sim {1067} \; {\ rm nm} $处谐振的布拉格光栅，来评估直径为400 µm，保持偏振的高阶模光纤。。通过比较沿光纤的慢轴和快轴偏振的光的反射光谱，并使用导出的数学关系式，我们估计了光纤中各种高阶模的双折射和偏振消光比。这是一种详细研究多模保偏光纤的简单而诱人的方法，这种多模保偏光纤是先进制造，国防，生物成像和电信系统的宝贵工具。