Asawa C K, Taylor H F
Appl Opt. 2000 May 1;39(13):2029-37. doi: 10.1364/ao.39.002029.
We describe experimental results and a theoretical analysis for propagation in graded-index multimode fiber when diode laser light is launched into the lowest-order propagation modes and the fiber undergoes severe bending perturbations. Experimentally, near-field modal interference images and transmission loss measurements were obtained for different loop diameters. The data indicate that, when the fundamental mode is excited, the light remains in lowest-order modes even for small bend diameters. This is consistent with analysis which predicts that, in a parabolic-index multimode fiber subject to constant diameter bending, the light tends to oscillate between lowest-order modes and remains trapped therein rather than diffusing to high-order modes. Implications of these results for an intrusion-resistant communication system with graded-index multimode fiber are discussed.
我们描述了在渐变折射率多模光纤中传播的实验结果和理论分析，此时二极管激光被注入到最低阶传播模式，且光纤受到严重弯曲扰动。实验上，针对不同的环路直径获得了近场模态干涉图像和传输损耗测量结果。数据表明，当基模被激发时，即使对于小弯曲直径，光仍保持在最低阶模式。这与分析结果一致，该分析预测，在受到等直径弯曲的抛物线折射率多模光纤中，光倾向于在最低阶模式之间振荡，并被困在其中，而不是扩散到高阶模式。讨论了这些结果对采用渐变折射率多模光纤的抗入侵通信系统的影响。
