Study Of The Optical Pulse Reshaping In The High Speed Optical Communication Systems

Optical communication systems are preformence of high-speed transmission and long distance. But in the high-speed transmission and long distance systems, the effect of fiber loss, dispersion and nonlinearity cause error and distortion. In order to increase the transmission distance and transmission rate, the optical pulse need to reshape and then the reshaping pulse is suit to transmit in the high-speed transmission and long distance system. The appearance and industrialization of optical pulse reshaping technology have become one of the most important achievements in high-speed transmission and long distance optical communication. A large number of optical reshaping technologies such as grating, nonlinear optical loop mirror, nonlinear birefringent technology. These technologies have already applied in the field of the pulse reshaping. In particular, the study of pulse reshaping using nonlinear birefringent fiber have become the focal point of the research in pulse reshaping, as its unique properties. Pulse reshaping using nonlinear birefringent fiber can be used to remove the low-intensity pedestal associated with some compressed pulses. It can also be used to make shutter. From the basic theory of signal transmission, pulses reshaping using nonlinear birefringent fiber have been studied in the dissertation. The main research work and results are as follows:1. At first, the current situation of pulse reshaping research and application prospect of pulse reshaping, as well as the technologies of pulse reshaping are introduced.2. Fiber loss, dispersion and nonlinear effect have been introduced in chapter 2, and the paper also have introduced the basic theory of nonlinear birefringent and deduced the coupled mode equation. The effect on the pulse reshaping with the polarization angle have been analyzed in the condition of linear and nonlinear.3. Pulse reshaping using the nonlinear birefringent fiber that have two modes coupled have introduced in detail. The pulse reshaping using high nonlinear birefringent fiber and low nonlinear birefringent fiber have been separately researched. Firstly, the nonlinear Schrodinger equations (CNLSES) of pulse reshaping using nonlinear birefringent fiber that have two modes coupled have been deduced Secondly, the effect factors of the pulse reshaping using variations and split-step Fourier method(SSFM).have been researched.4. This paper also have researched the pulse reshaping using nonlinear birefringent fiber with third-order dispersion coefficient. Firstly, the nonlinear Schrodinger equations(CNLSES)of pulse reshaping using nonlinear birefringent fiber that have two modes coupled with third-order dispersion coefficient have been deduced. Secondly, the third-order dispersion coefficient's effect on the pulse reshaping and other effect factors using calculus of variations(VA) and split-step Fourier method(SSFM).have been researched.The results indicate that:1) High nonlinear birefringent fiber and low nonlinear birefringent fiber, the transmission of pulse relies on the instantaneous intensity, and the initial energy of pulse. Choosing a proper the initial energy of signal pulse can lead to the higher transmission of the pulse in the central part than in the tails of pulse, consequently, pulse compressing or pulse reshaping can be achieved.2) The transmission of pulse relies on the angle between the fiber's principle axe and the polarizer, choosing a proper the angle between the polarizer as well as the fiber's principle axe can lead to the higher transmission of the pulse in the central part than in the tails of pulse, consequently, pulse reshaping can be achieved.3) Slow-axis and fast-axis have diffident pulse evolution.The results indicate that:4) The effect of the third-order dispersion coefficient is third-order dispersion coefficient stronger the pulse reshaping will be more significantly.5) The transmission of the pulse depends on the angle between the polarizer and the fiber's principle axe and the initial energy of signal pulse, when the polarization angle closed to the slow-axis and choosing a proper the initial energy of signal pulse and third-order dispersion coefficient can lead to the higher transmission of the pulse in the central part than in the tails of pulse, consequently, pulse reshaping can be achieved.