Explaining and exploiting the radial memory effect in multimode optical fibers

Light propagation through a multimode optical fiber results in a seemingly random speckle pattern at the output. This makes it difficult to harness the full information capacity that such fibers are theoretically capable of supporting. Yet, propagation through a fiber is fully deterministic, which leads to correlations in the apparently random output. In this work, we explain and characterize the so-called “radial memory effect,” which manifests as an output ring of excess energy at the same radius as an input focused spot. We show that this effect is robust against the bending of the fiber, discuss its connections with other known correlations, and develop a scheme for its use for spatial multiplexing.