High-density Cables for Controlling Differential Modal Delay of 2-LP-mode Graded-index Optical Fiber

We propose a high-density cable for controlling differential modal delay (DMD) by using the curvature induced within the cable structure to achieve zero-DMD with low optical loss for arbitrary 2-linearly polarized (LP)-mode graded-index optical fiber. We also present a theoretical model for controlling the curvature of optical fiber to control DMD and clarify, on the basis of the theoretical model, that increasing the diameter of the optical fiber unit enhances DMD controllability and reduces the increase in optical loss. We numerically investigate the curvature to achieve zero-DMD with an arbitrary profile exponent and trench depth of 2-LP-mode graded-index optical fiber. We validate the model by fabricating high-density cables with curvature control and experimentally measuring fiber curvature, DMD, and optical loss. On the basis of these analyses, we identify optimal cable-design parameters that achieve a target fiber curvature with minimal lateral pressure by deriving the relationship between bundle tension, unit diameter, and induced fiber curvature.