The Study Of Optical Nonlinearity In 160Gbit/s OTDM

ABSTRACT:With the fast development of Internet and multimedia technology, demanding for wideband communication systems increases rapidly. Improving bandwidth becomes a hot topic. Wavelength division multiplexing (WDM) and Optical time division multiplexing (OTDM), as key technologies for increasing bandwidth, have attracted considered attentions. OTDM, by increasing bit rate of single channel, improves spectrum efficient substantially. Loss, dispersion and fiber nonlinearity have been regarded main factors which degrade performance of optical systems. However, loss and dispersion have been appropriately solved by EDFA and dispersion compensator. As bit rate increasing, inter-channel nonlinearity becomes main factor which limit performance of OTDM systems. Today, more and more devices for high-speed optical communication systems based on optical nonlinearity were presented and widely used, such as Brillouin fiber lasers. This thesis present some research work in fiber nonlinearity based on the national 863 project named "Research on transmission technology of 160Gbit/s optical systems". It consists of following parts:1. We study the generation mechanism of nonlinear Kerr effects. The essence of nonlinear Kerr effects is the interaction between the fiber refractive index and the input intensity. And it will lead to the introduction of additional phase, broadening the spectrum or the generation of new frequencies as the perturbations for communication system. The nonlinear Kerr effects can be divided into inter-channel nonlinear optical effects and intra-channel nonlinear optical effects. Intra-channel nonlinear effects are derived from the interaction among the pulses in the same channel, which can be divided into two phenomenons named Intra-channel Cross phase modulation(IXPM) and Intra-channel four wave mixing. IXPM introduces the time jitter in the time domain and IFWM introduces the pulse amplitude jitter and generates the ghost pulses in the time domain. For achieving the optical transmission system used to transmit the 160Gbit/s, RZ coded singal through 100 kilometers, it is very important to adopt a suitable dispersion management solution for suppressing the perturbations caused by the intra-channel nonlinear optics.2. This paper compares with two main methods, which are used to suppress the effect caused from IXPM and IFWM, and combines with the existing experimental conditions. In the end, the high-dispersion management system is adopted for suppression of intra-channel nonlinear optics in the 160Gbit/s RZ coded 100km OTDM optical transmission system. Finally the high-dispersion management system will be proved effectively by analyzing the experimental results.3. We analyze the generation mechanism of Stimulated Brillouin Scattering, SBS. To Summarizes the structure and relevant theories of stimulated Brillouin scattering fiber laser. According to the feature of stokes lightwave's spectum and the experimental conditions of this project, we propose a new stable laser solution based on the theory of SBS, and analyze the feature of the output laser. Meanwhile, using the stable laser caused by the SBS as the control singal, in order to achieving the low-cost structures for de-multiplexing and retrieving the clock.