Generation And Transmission Of Novel Modulation Formats For High-speed Optical Communication

Advanced modulation formats are key technologies for the innovative development of the large capacity and long distance in the high-speed optical communication network. Thus, the application investigation on novel modulation formats is of great significance in both theory and practice for the upgrade of operational validity and reliability, for the reduction of costing budget and configuration complexity, for the"triple network convergence"and"replacement of copper cables with optical fiber cables". In this dissertation, a few new modulation formats applications for the high-speed optical signal transmission system are mainly discussed, and for the large-capacity optical label switching network are also studied. The main work and contribution of the report are as following:1, Three novel modulation formats suitable for traditional optical signal transmission system, which include modified optical duobinary modulation format, dark RZ format, and the orthogonally modulation format based on dark RZ format, were proposed and demonstrated. At first, through analyzing the process of coding and decoding, we have demonstrated modified optical duobinary signals have capability in reduction of pulse-to-pulse interaction, and could be directly measured through a conventional binary intensity modulation direct detection (IM-DD) receiver. Simulation results showed that MD-NRZ and MD-RZ signals'formats could avoid the eye diagram distortion after transmission, if the dispersion could be compensated in each amplifier span. Moreover, the MD-RZ signal has lower BER than the MD-NRZ signal after transmission. The optical spectrums characteristics of the MD-RZ signals with different duty cycles were compared by experiment. Secondly, a novel scheme for dark RZ signal generation by using a phase modulator and a Mach-Zehnder interferometer (DL-MZ-I) was proposed. Through analyzing the process of modulating, coding and decoding theoretically, we have demonstrated this design allows for adjusting the duty cycle and the extinction ratio of a dark RZ signal, at the same time, the optimal value of decision point for decoding was indicated. We have experimentally demonstrated: the dark RZ signal has higher optical spectra efficiency, and it not only could be applied to increase capability for optical transmission system, but also could be applied to long-distance communication. At last, a novel orthogonally modulation format was proposed and demonstrated. This format with tunable duty cycle and extinction ratio in the optical domain was generated, and was demonstrated that it has high spectral efficiency. A 10Gbit/s DPSK signal was been successfully superimposed on a 10Gbit/s dark RZ signal to achieve orthogonally modulation. After 124km transmission, the characteristicis of the DPSK signal and the dark RZ for avoiding residual dispersion and nonlinear effect were compared.2, In a 100Gbit/s optical signal transmission system, through analyzing the characteristics of the four serial phase modulation formats with those of NRZ-DPSK, RZ-DPSK, NRZ-DQPSK, and RZ-DQPSK, respectively,four new phase modulation formats which involve NRZ-SDPSK, RZ-SDPSK format with 50% duty cycle, and RZ-SDPSK format with 33% duty cycle or 67% duty cycle, were proposed and discussed. We have shown that, to NRZ-DPSK, RZ-DPSK, NRZ-DQPSK, and RZ-DQPSK, when each signal was transmitted over 106km optical fiber, the NRZ-DQPSK signal has the highest chromatic dispersion tolerance when the fiber input powers of four phase modulation formats are same.If only considering first order polarization mode dispersion (PMD), RZ-DQPSK has the largest first order PMD tolerance. When adjusting the fiber input power from 0~10dBm, RZ-DPSK format is very robust against nonlinearities. In addition, the NRZ-DPSK signal has the best transmission performance, if it was launched into a third-order Gaussian optical bandpass filter (OBPF) placed with beyond 125GHz bandwidth. We have also proposed and demonstrated generation and detection of two new staggered differential phase-shift keying (SDPSK) phase modulation formats, NRZ-SDPSK and RZ-SDPSK with 50% duty cycle, for 100 Gbit/s applications. By comparing the transmission characteristics of the two staggered phase modulation formats with four traditional cascading phase modulation formats, we show that, the SDPSK signal has similar chromatic dispersion and polarization-mode-dispersion tolerance to the DPSK signal with same NRZ or RZ shape, while the SDPSK signal has stronger nonlinear tolerance than the DPSK or DQPSK signal. In addition, the RZ-SDPSK signal with 50% duty cycle has the best transmission performance when each signal was transmitted over long-haul optical fiber, and then launched into a third-order OBPF placed with beyond 125GHz bandwidth. Finally,we have proposed and demonstrated generation and detection of two new RZ-SDPSK formats with 33% duty cycle and 67% duty cycle, for 100 Gbit/s transmission. Through comparing their transmission characteristics, we have shown that, the generated RZ-SDPSK signal with 33% duty cycle was especially suited for single carrier transmission in the metropolitan area network without first-order-PMD compensation and with a lower bandwidth OBPF, and the CSRZ-SDPSK with 67% duty cycle signal has higher dispersion and nonlinear tolerance. For extracting clock signals effectively, the bandwidth of OBPF should be larger than 100GHz.3, Two modulation formats, MD-RZ and dark RZ were generated as labels for optical label switching network based on orthogonal modulation, were proposed. In the first instance, a NRZ-DPSK signal was generated as payload, and a NRZ-DQPSK payload was also introduced. When the duty cycle of label was changed, the performance of spectra diagrams of two optical packet signals was studied,in back-to-back system with 2.5Gbit/s label and 10Gbit/s NRZ-DPSK payload or 20Gbit/s NRZ-DQPSK payload. The results showed the optical packet signals with bigger duty cycle label have higher optical spectra efficiency. MD-RZ labels of two optical packet signals could avoid the eye diagram distortion for long-distance transmission, if the dispersion could be compensated. When the value of fiber input power was beyond 18 dBm, the eye-opening penalty of MD-RZ labels with bigger duty cycle was higher transmission robust in label-detecting path. In the second instance, a novel scheme to generate optical dark RZ signals with tunable duty cycle and extinction ratio was proposed, through modifying the process of modulating and coding. The optical dark RZ signals were easily generated only by simply using a dual-arm Mach-Zehnder LiNbO3 modulator along with an electrical signal time delay device. It was demonstrated experimentally that the optical dark RZ signals could be directly measured by a conventional binary intensity modulation direct detection (IM-DD) receiver. When the electrical signal time delay device at 2.5Gbit/s was adjusted, the changes of optical spectra, the BER curves, and the eye diagrams of the optical dark RZ signal for different duty cycles are obtained experimentally.4, Through analytical equation, numerical simulation and experiment, the principle for generating optical carrier suppression and separation (OCSS) was demonstrated. Two novel label switching schemes based on OCSS were proposed and studied by experiment. One is 9.3Gbit/s amplitude modulated payload and 2.5Gbit/s amplitude modulated label were encapsulated an optical packet signal, and the label and payload were detached after this optical packet signal was transmitted over 80km SMF. The transmission performance of 9.3Gbit/s payload was studied. The other is 100Gbit/s RZ-DQPSK payload and 3.125Gbit/s amplitude modulated label were combined optical packet signal, and were separated after 240km transmission with pre-dispersion compensation. The transmission characteristic of 100Gbit/s payload was investigated by experiment.