The performance of plastic optical fiber is greatly influenced by the related but distinct effects of mode coupling and differential modal attenuation (DMA). We establish a method for estimating the matrix that governs both of these effects and allows us to distinguish the two. We obtain partial quantitative estimates of this matrix for a particular graded-index plastic optical fiber (GI-POF). The sample we studied exhibited strong but incomplete mode coupling over 100-m lengths, while DMA was largely limited to a centerline defect. We show that much of the loss of the fiber can be attributed to mode coupling between mode groups with similar effective indexes.
Steven E. Golowich, Whitney White, William A. Reed, and Erik Knudsen, "Quantitative Estimates of Mode Coupling and Differential Modal Attenuation in Perfluorinated Graded-Index Plastic Optical Fiber," J. Lightwave Technol. 21, 111- (2003)