An ytterbium-doped fiber laser mode-locked by the interaction of a fiber Bragg grating and longitudinal acoustic waves in a suspended core fiber is experimentally investigated. An optimized design of an acousto-optic modulator is also proposed. The results indicate output pulses with a width of less than 550 ps at a repetition rate of 10 MHz. The reduction of the power consumed by the transducer and the grating length points out to more efficient, compact and fast acousto-optic modulators for mode-locked all-fiber lasers.