Application Of Advanced Modulation Formats In Optical Label Switching System

More than Tbit/s switching rate and storage capacity are needed to deal with largeamounts of video, data and other information in optical communication, due to thegrowing rise of broadband services. However, O/E/O transformation and processing inelectrical domain is necessary in the switching node. The speed of electronic switchingand electrical information processing reached the limit caused the “electronicbottleneck” on data processing and data transmission.To resolve the problem, the optical label switching technology was studied as themain object, and the operation principles of orthogonal modulated optical label wasanalyzed in depth. Furthermore, the basic principles and implementations of m-aryformat modulation (such as8PSK, D8PSK and16-QAM signals) in OLS and keycomponents were investigated by theoretic analysis. The contents are as follows:To obtain higher spectral efficiency, the simulation setup of120Gb/s8PSK/ASKorthogonal modulated OLS system was built. External modulator’s extinction ratio (ER)was analyzed and optimized. The performance of the system with a Tunable OpticalFilter and the Multi-Symbol Phase Estimation algorithm was analyzed. The effects ofdispersion compensation programs, the Optical Signal-to-Noise Ratio and transmissiondistance on system performance were analyzed in detail.One advanced modulation format--D8PSK was introduced to deal with the phaseambiguity between the8PSK payload and ASK label, the failure of receiver phasereversal decoding. With the D8PSK parallel modulation method, the simulation setup of120Gb/s D8PSK/ASK orthogonal modulated OLS system was built. The effects of thekey parameters (extinction ratio, Tunable Optical Filter, dispersion compensationscheme, and transmission distance) on system performance were analyzed.The16-QAM modulation format was introduced to obtain higher spectralefficiency, and its operation principles were analyzed briefly while the dispersion wascompensated by DSP. The simulation setup of40Gb/s,16-QAM/FSK orthogonalmodulated OLS systems was built, the results indicated the feasibility of the scheme. Atlast, the problem of frequency offset caused by the coherent demodulation was discussed.