Theoretical And Experimental Study Of Dark Solitons Generation In The Erbium-doped Fiber Ring Laser

Owing to simple and compact structure and low manufacturing cost, the fiber ring laser has a wide range application in fiber senser, spectrum analysis, material proccessing and optical communication system etc. Because dark solitons have many advantages, such as better shape-preserving properties, long transmission distance and high capacity and so on, they have a wide range application in the field of all-optical nonlinear communication technology, the nonlinear optics, optical switching and so on.In this paper, based on the coupled complex nonlinear Schrodinger equations, we do the research on the generation of the dark solitons in the erbium-doped fiber ring laser theoretically and experimentally. With the generation of the dark solitons in the erbium-doped ring laser, in this paper, main works are carried out as following:1. We introduce the historical background, development trend, advantages, classification and situation of the fiber lasers and dark solitons.2. Based on the coupled complex nonlinear Schrodinger equations, the evolvement of the dark soliton is numerically investigated in erbium-doped fiber ring mode-locked laser by the nonlinear polarization rotation technique. In the fiber laser, we analyse that the dark solitons properties are related to the orientation of the polarization controllers and the pump power. The results show that, owing to the nonlinear polarization rotation technique, the change of the work state of the polarization controllers and the small signal gain will lead to the difference of the peak distribution of the transmittance function of the fiber ring laser. In this case, the number of the dark soliton is different. The evolution of dark-dark soliton pairs is led by the inherent characteristics of the fiber ring laser. The generation of the optical spectrum sideband is caused by the interference of nonlinear phase. The self-phase modulation and the cross-phase modulation generate the nonlinear phase.3. Based on the nonlinear effect, we obtain the dark-dark soliton pairs and the dark soliton trains of the erbium-doped fiber ring laser in the experiment. The results demonstrate that the output repetition frequency of the single dark soliton and the dark soliton trains is98ns.