Spatial Division Multiplexing (SDM) is being increasingly applied to optical fiber systems . Thus, SDM is gradually becoming a fundamental part of modern telecommunications aiming to provide higher transmission rates that are both error-free and inexpensive. So far, engineers considered packing and operating the many different laser as the biggest problem, but as it seems, the crosstalking phenomenon between the various in-fiber propagating modes creates a great barrier, which needs sophisticated methods to overcome, such as MIMO techniques, which are well known in the wireless field. In this paper, we analyze real data from multimode optical fibers and find that crosstalk seems to be significant. If this is the case, the reception can be problematic without MIMO techniques.