Abstract:In this letter, a passively Q-switched all-fiber laser is demonstrated using a 10 cm long Bismuth-doped fiber as a saturable absorber (SA). The dual wavelength operation was obtained due to the nonlinear effect inside the fabricated BDF, which has a high germanium content. Stable Q-switched pulses were obtained at the dual synchronous wavelengths of 1530.1 nm and 1531.1 nm. When the pump power is tuned from 105.3 to 191.0 mW, the repetition rate can be varied from 82.6 to 117.6 kHz. The maximum pulse energy and average output power were 83.4 nJ and 9.8 mW, respectively while the minimum pulse width was 8.5 μs at the maximum pump power of 191.0 mW. To the best of our knowledge, this is the first report on a dual-wavelength Q-switched laser based on a BDF SA. Our results indicate that BDF could be a promising alternative optical modulator for pulsed fiber laser application.