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We report experimental observations and numerical simulation results on the spectrum moving, narrowing, broadening, and wavelength switching of dissipative solitons (DSs) in an all-normal-dispersion Yb-fiber laser that is passively mode-locked by using the nonlinear polarization rotation (NPR) technique. We found numerically that the DS spectrum moving, together with spectrum narrowing/broadening, is caused by the effective gain profile change resulted from the moving of the artificial spectral filter. Furthermore, we show that the wavelength switching observed in the laser is a natural consequence of the effective gain switching. The moving of the artificial spectral filter could be originated from either the cavity birefringence change or the polarizer rotation. Due to the broad gain and the artificial birefringent filter introduced by the NPR technique, apart from the central wavelength shifting and bandwidth changing, wavelength switching of DSs could be obtained by simply rotating the polarizer. Numerical simulations well reproduced the experimental observations. Our results suggest that extra effort should be made for wavelength tuning if there is any polarization-dependent component in the cavity as the wavelength switching will interrupt the continuously wavelength shift.

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We report results of numerical simulations on the various initial conditions for dark soliton generation in an all-normal-dispersion fiber laser. All the dark solitons generated are odd dark solitons. Differently from the dark soliton generation in fibers, where an arbitrary dip could evolve into a dark soliton, it is found that the dark soliton can originate only from an initial dip with a certain parameter requirement. A bright pulse with either a hyperbolic secant square, Gaussian, or Lorentz profile can be developed into a dark soliton, provided that the parameters of the initial bright pulse are selected. Dark solitons can be generated in fiber lasers only if there is a phase jump, and this phase jump can be maintained and evolve to π during the pulse evolution.

Experimental observations from different fiber lasers or different states within a fiber laser confirm that the fiber dispersion parameter is wavelength‐dependent, which suggests that the fiber dispersion measurement based on Kelly sidebands should base on either positive or negative sideband order only rather than sideband orders across zero. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:242–245, 2016