Study On Advanced Modulation Formats In High Speed Optical Communication System

Advanced modulation technique is one of the key technologies for the development of large capacity and longe distance high-speed optical communication networks. Thus, the study on novel modulation formats and theirs applications is of great significance theoretically and practically for the upgrade of operational validity and reliability, the reduction of operation cost and structural complexity, the development of "triple play"and "copper retreat into the light". Several novel modulation formats and theirs applications in high speed optical transmission networks, optical label switching networks and optical broadband access networks are studied in this thesis. The main achievements and contributions are as follows:(1) A novel carrier suppressed return to zero-frequency shift keying (CSRZ-FSK) modulation format is proposed in this thesis; we simulated the transmission performance of 40Gbit/s CSRZ-FSK signal. Compared with traditional scheme for the generation of frequency shift keying (FSK), this scheme can produce 40Gbit/s CSRZ-FSK signal with a single light source, avoiding the drawbacks of precise control for the wavelength and optical power of traditional two light sources approach. It is beneficial to reduce the cost of wavelength division multiplexing (WDM) and wavelength division multiplexing-passive optical network (WDM-PON) systems by carrier suppression for the entire wavelength at once. In addition, the single-span transmission performance of 40Gbit/s CSRZ-FSK signals, differential quadrature phase shift keying (DQPSK) signals and amplitude shift keying (ASK) signals under different compensation schemes were investigated in this thesis.(2) We propose an optical label switching scheme by orthogonal modulation which is implemented by 40Gbit/s CSRZ-FSK payload and 2.5Gbit/s label. It can effectively overcome the disadvantages of low nonliner tolerance, limited transmisssion rate and distance of ASK playload for the traditional ASK/FSK scheme. This scheme has a simple receiver structure and low cost by the optical filter and direct detection for 40Gbit/s CSRZ-FSK payload.(3) The generation scheme, implementation principle and transmission performance of 33% return to zero-frequency shift keying (33%RZ-FSK) modulation format are studied in this thesis. The simulation and comparsion results of 40Gbit/s 33%RZ-FSK, differential phase shift keying (DPSK) and return to zero (RZ) signals show that the 40Gbit/s 33%RZ-FSK signal has the highest nonlinear tolerance, smallest power penalty.(4) We propose an optical label switching scheme by orthogonal modulation which is implemented by 40Gbit/s 33%RZ-FSK payload and 2.5Gbit/s ASK label, simulate the transmission performance of them under different compensation schemes. The 33%RZ-FSK/ASK format is less influenced by phase noise evidently, has a simpler structure and lower cost compared with DPSK/ASK sheme.(5) We propose a new type of chirped returen to zero-frequency shift keying (CRZ-FSK) modulation format and compare the transmission performance of 40Gbit/s CRZ-FSK signals, RZ-DQPSK signals and CSRZ signals.(6) We present a 40Gbit/s CRZ-FSK/2.5Gbit/sASK optical label switching architecture and simulate the transmission performance in details. The simulation results show that, it has longer transmission distance compared with CSRZ-FSK/ASK scheme.(7) A novel alternate polarization-frequency shift keying (APol-FSK) modulation format is proposed in this thesis. The polarization-switched modulation provides a better suppression of nonlinear system degradation than FSK and carrier suppressed return to zero-differential quadrature phase shift keying (CSRZ-DQPSK) formats. The polarization switching between adjacent bits disables power interactions between them, resulting in a lower pulse interaction and a larger nonlinear tolerance. At the same time, the orthogonal polarization between bits is maintained over long transmission distance independently of PMD impacts in the transmission line.(8) We design a novel WDM-PON system by orthogonal modulation scheme. It transmitted downstream signals by 40Gbit/s APol-FSK modulation format and upstream signals by 2.5Gbit/s ASK modulation format. Simulation results show that the system has good transmission performance across 20km single mode fiber (SMF). Compared with the traditional two light sources FSK/ASK modulation system, the number of light source of OLT is reduced to the half of the original; the ONU is working without light source, which effectively reduces the cost with less devices.(9) A novel alternate polarization-return to zero-frequency shift keying (APol-RZ-FSK) modulation format is proposed in this thesis. Simulation results show that, it has stronger nonlinear tolerance when compared with all of the modulation formats studied in this thesis.(10) We design a novel WDM-PON system by the orthogonal modulation scheme. It transmitted downstream signals by 40Gbit/s APol-RZ-FSK modulation format and upstream signals by 2.5Gbit/s ASK modulation format. Simulation results show that this system has better transmission performance than APol-FSK/ASK-based WDM-PON system.(11) The nonlinear tolerance and dispersion tolerance of NRZ, RZ,33%RZ, CSRZ, DPSK, RZ-DPSK, CSRZ-DPSK,33%RZ-DPSK, DQPSK, DQPSK, RZ-DQPSK, 33%RZ-DQPSK, CSRZ-DQPSK, FSK, RZ-FSK,33%RZ-FSK, CSRZ-FSK, CRZ-FSK, APol-FSK, APol-RZ-FSK modulation formats are simulated in this thesis. We analyze the disadvantages and advantages of various modulation formats and summarize the applications of them. It can provide a comprehensive reference for researchers to select the suitable modulation format when designing systems.