Over the last few years, we have experienced a renaissance of nonlinear optics in multimode fibers, driven by both fundamental and applied research. Multimode optical fibers (MMFs) offer a natural environment for investigating multidimensional systems and their complex collective dynamics. Indeed, numerous new nonlinear effects have recently been observed including, for instance, Kerr beam self-cleaning, mode-locking by spatiotemporal filtering, or multimode parametric wave mixing, to name a few . On the other hand, from the application perspective, MMFs are expected to provide interesting novel solutions for high power delivery and increased transmission capacity. Significant work is now in progress to exploit the recently discovered dynamics, and improve the performances of different technologies such as laser endoscopy, nonlinear imaging, and fiber-based laser sources , . In addition, the recent development of advanced measurement techniques, permitting to capture the full spatiotemporal nature of the multimode phenomena has also attracted a strong research interest .