Research On Transmission Characteristic And Simulation Of 40Gb/s New-type Code Modulation

Along with the continual development of economy, the requirement of information is increasing rapidly. To improve communication capacity and network bandwidth of the system can satisfy the increasing information quantity. 40Gb/s system, which has higher transmission rate, lower cost and better flexibility, is the ideal choice to satisfy the requirement of increasing information transmission quantity. However, high rate also brings new questions, such as dispersion, non-linear effects, low signal-to-noise ratio and so on, so new technologies are adopted to overcome these handicaps. New-type code modulation is the hotspot of resent study.On the basis of analyzing optical modulation formats including NRZ, RZ, CSRZ and CRZ, the transmission characteristics of NRZ, RZ and CSRZ are compared by bit-error rate, and the relation between formats and transmission characteristics in single-channel transmission is gained.. With the study results, the integrative evaluating system of transmission characteristic of new modulation formats is established. The relation among modulation formats, signal energy and pulse width is studied by equation. Two time-frequency analysis methods, Wigner-Ville Distribution (WVD) and Fractional Fourier Transform (FRFT) are introduced to analyze transmission characteristics of NRZ and RZ. In the end, effective measures to improve transmission performance of system are gained. MATLAB is used to simulate time-frequency characteristic of NRZ and RZ. The study results show that adopting different code modulation formats is the important technology to overcome questions in 40Gb/s transmission and improve transmission performance. Time-frequency analysis method can analyze transmission characteristic effectively from time region and frequency region. RZ has the better performance than NRZ, so it is more suitable for high-speed and long-haul optical transmission.