A home-made computer code has been implemented to design high power ytterbium doped fiber lasers by following different techniques. The goal is to maximize the effective mode area by maintaining a good beam quality. As a preliminary simulation result, a novel aperiodic fiber lattice, very promising in order to construct high power and single mode lasers, has been identified. The laser obtained by employing the aforesaid aperiodic fiber has been compared, via simulation, with three other fiber sections, taken by literature but suitably optimized.