This paper tackles the problems of simple and robust experiment design for system identification using elementary fractional models. It is based on a frequency domain approach and allows to determine the best sine input signal maximizing D-optimality criterion of the parameters inverse covariance matrix in different contexts? First, a single parameter (any of the parameters of the elementary fractional model) is assumed to be unknown. Next, any combination of two and then three parameters are supposed to be unknown. Finally, the problem of robust experiment design is treated when a bounded interval of the estimated parameters is known, in the same contexts.