Experimental investigations on the relative phase stability in amplifying multicore fibers

In 2014, it was hypothesized that MCFs could act as shielded interferometers, where environmental perturbations would affect all cores in a highly correlated manner, leading to stable relative phases. However, this hypothesis has remained unverified. In this work, we present experimental evidence of relative phase stability in an Ytterbium-doped MCF at high power levels. Using two complementary measurement techniques, we demonstrate sub-wavelength relative phase stability at average output powers up to 55 W.