Quasi error-free 10 Gbit/s data transmission is demonstrated over a novel type of 50 µm core diameter photonic crystal fiber with as much as 100 m length. Combined with 850 nm VCSEL sources, this fiber is an attractive alternative to graded-index multi-mode fibers for datacom applications. A comparison to numerical simulations suggests that the high bit-rate may be partly explained by inter-modal diffusion.