In this work, a novel, to the best of our knowledge, α-BaTeMo2O9 crystal-based acousto-optical modulator is designed and successfully applied in actively Q-switched and mode-locked Er-doped fiber lasers (EDFLs) and Yb-doped fiber lasers (YDFLs) operating at 1.5 and 1.0 µm. The shortest pulse width of 429 ns and 1.37 µs are obtained in actively Q-switched EDFLs and YDFLs, respectively. For actively mode-locked operation, a pulse width of 11.32 ns at a modulation frequency of 3.19 MHz is obtained in EDFLs, while it is 29.9 ns at 1.036 MHz in YDFLs. The results indicate that the α-BaTeMo2O9 crystal is a promising candidate for all-fiber active modulators.