Study On Theory Of Self-similar Pulse Generation And Transition Based On Passively Mode Locked Fiber Laser

Currently, solitons are commonly used in fiber communication systems beacons of the ability of maintaining them shape while propagating in anomalous dispersion fibers, but the exits of nonlinear in fiber limit the pulse energy, the soliton energy cannot reach to a enough level that make soliton transmission ultra-long haul distance, despite the loss is small, it will need relay station after a certain transmission distance. For the purpose of take an ultra-long haul distance data transmission without relay station, it will be improved the laser source and at the same time modify the transmission media.In this thesis, study on the self-similar mode-locked fiber laser and the transmission of self-similar pulses are carried out respectively to meet the needs which put above, and the following researches have been developed.1. Simulation the dispersion range of a passive mode-locked Yb-doped fiber laser which could output the self-similar pulse and the characteristics of self similar pulse. Numerical analysis the influence on the output of self similar pulse parameters while laser’s GVD(Group Velocity Dispersion), gain saturation energy and finite gain bandwidth were changed. Quantitatively study the self-similar pulse characters.2. Research the interaction between a pair of self similar pulses which evolved in the passively mode-locked fiber laser. The results show that the interaction depends on the separation distance of two pulses firstly, more closely the more obviously interaction. Secondly, the interaction is determined by the inter-cavity average dispersion and gain saturation energy, i.e., the strength of the interaction is proportional to the gain saturation energy, a stronger gain saturation energy will result in a higher interaction intensity. In common sense, when two pulses separation is big enough, the interaction will disappear. On the contrary, the interaction of a self-similar pulse pair has a larger interaction distance. The results show that it still has the interaction when the separation reaches 20 ps while the pulse FWHM(Full Width Half Maximum) is 1ps. The wider gain bandwidth also influent the interaction.3. Research the propagation of self-similar and self-similar pairs in single mode fiber in detail. The results show that the self-similar pulse cannot evolve in the fiber with normal/abnormal dispersion without shape change. And the use of dispersion management fiber could solve the problem. In this thesis, suitable choose the length of dispersion management fiber and the dispersion map, quantitatively studied them role on pulse profile, energy, pulse width and the frequency width. Results in this part are used of ultra-long haul distance optical communication without relay.The research in this thesis has made some achievements in the following:1. Established the model of passively mode-locked fiber laser, propose a new Structure of fiber laser the output self-similar pulse. Inaugurate study the interaction of a pair of self-similar pulse which evolve in a fiber laser, and analyze the interaction mechanism, find out that the interaction of parabolic-shaped pulses is the result of phase shift, decrease the phase shift will limit the interaction effectively. The results will guide the experimental research and optimal design the self-similar fiber laser.2. Investigate the evolution of self-similar pulse and pair propagating in fiber. The results show that the self-similar pulse cannot evolve in the fiber with normal/abnormal dispersion without shape change. Then propose a method of dispersion management. The conclusion has certain academic significance to achieve long-distance non-repeater optical communication system, and will drive the applications self-similar pulses in optical fiber communication system.