Relative intensity noise characterization of supercontinuum generation in graded-index and step-index multimode fibers.

Multimode fibers have recently attracted significant attention due to their high-power handling capability and beam self-cleaning property that results in a single-mode profile at the fiber output. Here, we perform a detailed experimental comparison of the relative intensity noise (RIN) of all-fiber supercontinuum (SC) generated in multimode step-index (MMF) and graded-index (GRIN) fibers. We also characterize the spatial intensity profile of the SC in different wavelength bands, showing that it is near single mode across the full spectrum. Our results show that the RIN of SC generated in multimode GRIN fibers is not only lower than that generated in a step-index MMF but close to that of a SC generated in a single-mode fiber.