We report on mid-infrared optical parametric generation in the 4-5 μm and 9-12 μm bands by pumping custom-designed orientation-patterned gallium arsenide (OP-GaAs) rib waveguides with an ultrafast femtosecond fiber laser system. This pump source is seeded by a mode-locked fluoride fiber laser with 59 MHz repetition rate and can be tuned between 2.8 and 3.2 μm using a soliton self-frequency shifting stage. The single TE and TM modes OP-GaAs crystals feature quasi-phase-matched grating periods of 85 and 90 μm and different transverse sizes thus allowing a wide spectral tunability.