Noiselike pulse generation in a fiber laser by use of nonlinear differential filtering with a nonlinear birefringent loop mirror

We report observation of noiselike pulse generation in a passively mode-locked fiber laser incorporating the nonlinear birefringent loop mirror (NBLM) which consists of a symmetric coupler and an asymmetrically located 90/spl deg/ rotation element in the loop. In this laser, the noiselike pulse generation results from nonlinear differential filtering due to the polarization-mode-dispersion effect in the NBLM, which is equivalent to nonlinear filtering in the ring laser.