Research On Advanced Modulation Format In Optical Packet Switched Networks

Because of the advantages of high exchange efficiency and the flexible modulation format,Optical packet switched network(OPS)is the key technology of the next high-speed all-optical communication network.Based on the 863 project "key technology of all-optical packet switched network" and the National Natural Science Foundation of China,we focus on the key technologies in all-optical communication network,such as the network architecture,advanced modulation formats,optical packet modulation,and orthonal modulation scheme,to demonstrate the feasibility by simulation.The main achievements and contributions are as follows:A novel high-speed optical modulator is proposed in this paper in order to generate the frequency shift keying(FSK)format.We demonstrate the feasibility of this modulation scheme.This kind of modulator can generate high-speed FSK signal without applying high-speed radio frequency signal to generate sub-carriers.Therefore,this modulation scheme can decrease the influence of RF signal on optical signal and the complexity of the system architecture.In this paper,we demonstrate the transmission performance and analyze the influence of the lasers' stability and the modulator's manufactural error on the performance of FSK signal.The results show that this modulation scheme performs better stability of the system error and the power penalty of transmission performance increases 0.2dB after 50KM single mode fiber.In order to select the optimal values of system parameters,the transmission performance under different influence factors,such as central frequency of filters,bandwidth,dispersion compensation scheme,is analyzed by simulation.Based on the novel modulator,we propose a novel orthogonal modulation scheme for optical packet switching network.In this modulation scheme,the payload with Manchester coding is ASK format at 40Gbs,while the label is FSK format at 2.5Gbs.In previous works,the main disadvantages in orthogonal modulation scheme are the high crosstalk and low extinction ratio between label and payload.Our scheme applying MC,which is a bis-phase modulation,instead of NRZ coding in the payload can greatly increase the ER.The simulation results show that the balanced ER can increase 6.1dB comparing with NRZ coding.Besides,the transmission performances for label and payload are both increased after 50 km SMF under the balanced ER.Moreover,the transmission performances under different influence factors(dispersion,input fiber power and so on)are demonstrated and analyzed.The results provide proper values of parameters for the experiments.We propose a novel modulation scheme combining FSK label and ASK(MC coding)payload.This modulation scheme only applies one high-speed dual-MZ modulator instead of more than one modulator in previous modulation schemes.The less numbers of modulators can reduce costs and increase the transmission performance.We demonstrate the system transmission performance under different influenced factors and analyze the influence of the bandwidth,extinction ratio,dispersion on the system performance.