Studies On Chirped Soliton-like Pulses In Optical Fiber Amplifier With Variable Parameters

The phenomena of soliton has been seen in many fields. Since soliton was found in the 19^th century, the theories of soliton always have been an important research aspect in many fields, such as math, physics and communication. The generating of the optical soliton is a very graceful kind of physical process, which is a balance of fiber dispersion and self phase modulation (SPM). Optical soliton is not only an important research aspect, but also it has very important application foreground, which will be the new mode of optical communication and high speed full-optical switch. In the paper, based on the Ginzburg - Landau (GL) equation with varying coefficients governing the propagation of optical pulses in optical fiber amplifier, we present the chirped bright and dark soliton-like solution by ansatz method and discuss the transmission property of the soliton-like solution in optical fiber amplifier. We study the stability of the soliton-like pulse by the perturbation method and the numerical simulation, and get some useful results. These results may be helpful for studying the stable transmission of optical pulses in inhomogeneous fiber amplifier and soliton control systems. The main contents are as follows:1. The developing process and status of optical soliton communication are reported in summary, and the significance of studying chirped soliton-like solutions is introduced.2. The (higher-order) nonlinear Schrodinger equation describing the propagation of optical pulses in inhomogeneous or ideal fiber system and the Ginzburg-Landau (GL) equation with varying coefficients governing the propagation of optical pulses in optical fiber amplifier are presented. Finally, a numerical method, i.e. the symmetric split-step Fourier method is introduced.3. Exact chirped bright and dark soliton-like solutions of the Ginzburg-Landau (GL) equation with varying coefficients were found by using a suitable ansatz. Furthermore, we analyze the features of the solitons and consider the problem of stability of these soliton-like solutions under finite initial perturbations.4. With the aid of the numerical method, we analyze the interaction between two neighboring soliton-like pulses in inhomogeneous fiber amplifier. The results show that the interaction is entirely different from that of pure bright or dark femtosecond solitons.