Evolution of dark-dark soliton pairs in a dispersion managed erbium-doped fiber ring laser

The evolution of dark-dark soliton pairs is numerically investigated in a dispersion managed erbium-doped fiber ring laser. It is found that the fluctuation of the background, the sideband intensity of the optical spectrum, the distance and the width of dark-dark soliton pairs are related to the orientation of the polarization controllers and the pump power of the fiber ring laser. The evolution of dark-dark soliton pairs is caused by the modulation instability and the balance between gain and loss in the fiber ring laser.