Study On Lumped Amplification Of Solitons In Dispersion Decreasing Fiber Link

The transmission rate of the optical system is severely limited by the pulse broadening which is induced by the dispersion in the optical fiber,on the other hand,the loss of optical fiber will lead to failed transmitting of optical pulses over long distances.Therefore dispersion decreasing fiber is proposed,thus nonlinear effect reduced by loss can be balanced with decreasing dispersion,where the shape of the optical pulse is invariant and the optical soliton is formed.However,the energy of the optical soliton will be reduced because of energy loss in decreasing dispersion fiber.Naturally by cascading dispersion decreasing fibers and amplifiers,the long-distance transmission of optical soliton is experimentally realized in the cascade system.In this paper,based on the nonlinear Schr?dinger equation with periodic lumped amplification and decreasing dispersion,the exact bright soliton and dark soliton solutions are obtained by a simple transformation.The process of periodic lumped amplification and interaction of bright solitons and dark solitons are studied in dispersion decreasing fiber link.The results presented here are significance for the transmission of solitons and the accurate configuration of dispersion decreasing period lumped amplification fiber link in practice.The main contents of this paper are as follows:(1)In chapter one,based on the introduction of the background of optical solitons,the progress of bright solitons and dark soliton amplification are introduced.(2)In chapter two,the exact bright soliton solution of the variable coefficient nonlinear Schr?dinger(NLS)equation is obtained.Based on the solution,periodic lumped amplification and recovery of solitons are studied,and the influence of each parameter on bright soliton is analyzed during transmission.Meanwhile,the stability and the interaction of bright solitons are discussed numerically.The obtained results show that periodic amplification and recovery of the solitons can be realized under the balance among the dispersion,loss and amplifier gain.Also,one can configure the amplification period according to the fiber loss and amplifier period,or set the amplification period according to the fiber loss and the amplifier gain,thus the periodic amplification or recovery of solitons can be achieved in the dispersion decreasing fiber link with periodic lumped amplification.In addition,the interaction among bright solitons can be suppressed in such a system.(3)Based on the theoretical model presented in the second chapter,the exact 1-dark soliton and 2-dark soliton solutions are obtained in normal dispersion region.Using the 1-dark soliton solutions,the periodic lumped amplification,propagation and interactions of the dark solitons are studied in dispersion decreasing fiber link.Based on the exact 2-dark soliton solution,the interaction of collision,repulsive and parallel propagation between two dark solitons are investigated,respectively.Also,the stability of the dark soliton is numerically studied.The results show that the interaction between dark solitons can be controlled by choosing appropriate soliton parameters,and the dark solitons are quite stable in dispersion decreasing periodic lumped amplification fiber link.(4)Finally,the main contents of this thesis are summarized,the amplification and application of optical solitons in fiber communication are prospected.