A number of fiber optic magnetostrictive transducers were fabricated using various metallic glass ribbons made of Co70Fe10B20, Co76Fe4B20, Co80B20, Ni, Fe79B16Si5, and Fe40Ni38Mo4B18 and were characterized by a typical optical fiber Mach-Zehnder interferometer constructed by splicing the fiber transducers to the single-mode-fiber sensing arm. The ac magnetostrictive responses for the metallic glasses measured with the fiber optic sensing system show that the dc-bias field (Hp) for the maximum response with a Co70Fe10B20 ribbon is ~ 0.97 Oe, that with a Ni ribbon is 23 Oe, and with a Fe79B16Si5 ribbon is 5.7 Oe. A magnetostriction function describing the magnetostrictive response of the transducer was also empirically found. The measured effective magnetostrictive parameters and saturation magnetostrictions are 1.3 x 10-7/Oe2 to 7 x 10-7/Oe2 and -4.6 x 10-6 to 5.7 x 10-6, respectively. The optical fiber sensors exhibit minimum detectable fields Hmin of the order of between 10-5 Oe(rms)/√Hz and 10-7 Oe(rms)/√Hz above 1 kHz at their respective dc-bias fields Hp. The Hmin can be much further improved by reducing the level of noises that limit the phase resolution to ~ 10-4 rad/√Hz in the interferometer.