Few mode optical fibers for mode division multiplexing. The Few Mode Fiber supporting 25 or 30 LP guided modes and includes a graded index core with a α-profile, a radius R1 (at 0 refractive index difference) between 23 and 27 μm and a maximum refractive index difference Dn1 between 14·10−3 and 17·10−3, and an end of the α-profile at a radius R1b, with index difference Dn1b; a trench surrounding the core with radius R3 between 30 and 40 μm and refractive index difference Dn3 between −15·10−3 and −6·10−3. Such a FMF shows a specific design of the interface between the core and the cladding such that R1b>R1, Dn1b between −10·10−3 and −3·10−3, and Dn1b−Dn3≥0.9×10−3.