Generation of step-tunable microwave signal using a multiwavelength Brillouin fiber laser

We propose and demonstrate an all-fiber scheme to generate step-tunable microwave signals by heterodyning two Stokes lasing lights from a multiwavelength Brillouin fiber laser. Ten orders of Stokes lasing have been observed with rigid ∼11-GHz frequency spacing, and each order of Stokes works on single-longitudinal-mode operation. The generated microwave frequency is equivalent to the difference between two arbitrary orders Stokes from the laser. A ∼22-GHz microwave signal is obtained and the signal linewidth is less than 2 kHz. As a potential application, a step-tunable microwave source ranging from ∼ 11 to ∼77 GHz is proposed and partially demonstrated.