Modal noise in optical fibers: open and closed speckle pattern regimes

Modal noise generation in multimode optical fiber is identified as occurring in two statistically differing regimes, that in which there is independence of the speckles (open regime) and that in which the speckles have an interdependency related to the constancy of the total light power in the core modes (closed regime). We derive statistical expressions for modal noise generation in the closed regime and verify them with experiment.