| Recently, with the growth of communication services, subscribers demand for large capacity and high speed communication is increasing significantly. Presently, the commercial optical transmission systems are being upgraded from40G to100G. The research emphasis is to develop future Terabit/s and Petabit/s transmission in single fiber. Therefore, it is required to develop new technology to satisfy the large capacity and high speed demand. However, to achieve high speed systems need to overcome the signal distortions resulted by chromatic dispersion (CD), nonlinearity effects and polarization mode dispersion (PMD). This thesis conducts the research work based on the two problems.For the first challenge, the high speed system normally combines the new modulation formats with multiplexing technology. Currently DQPSK and16QAM are combined with polarization division multiplexing, frequency division multiplexing and space division multiplexing to achieve Terabit and higher speed communication system transmission. Especially the frequency-locked multi-carrier generation based on recirculating frequency shifter is the key technology in frequency division multiplexing. For the second problem, the linear and nonlinear impairments need to be mitigated or compensated in the high capacity systems. Generally there are two major techniques to compensate the impacts of impairments. The first method is optical or electrical compensation in direct reception systems. Whereas, the second method for compensation is based on digital signal processing (DSP) with algorithm for coherent detection. The algorithm covers chromatic dispersion compensation, polarization mode dispersion compensation and nonlinear effects mitigation and so on.In this thesis, our major focus is on the generation of different kinds of modulation formats, polarization control technology, multi-carrier generation and its application. We have developed and designed a new OPMDC (optical polarization mode dispersion compensation) prototype. The OPMDC prototype works well in the single channel43GB/s RZ-DQPSK DWDM commercial systems. It has shown reliable performance under the condition of SOP, DGD (differential group delay) and PSP(principle state of polarization) fast variation. We also have studied the multi-carrier generation based on RFS (recirculating frequency shifter) and its application in2.56Tb/S CO-WDM transmission system. The main research work is divided into the following sections:(1) Several modulation formats are studied in optical fiber communication system, including amplitude modulation format (OOK, PSBT), phase modulation format (DPSK, DQPSK), and quadrature amplitude modulation (16QAM). The theoretical analysis of the generation and reception of the above mentioned formats and the results establishment by simulation and laboratory experiments. Moreover, the polarization multiplexing and de-multiplexing is discussed, which will lay a solid foundation for the follow-up research.(2)The principle and implementation of polarization mode dispersion compensation are theoretically analyzed, and then the first national commercial OPMDC is developed. The performance of the prototype is tested in the practical system, and realized the error free43-Gb/s RZ-DQPSK signal propagation on a1200-km optical fiber link for12hours. The prototype indicator is better than that of the United States OTS-5450PMD compensator. In the end, the principle of polarization stabilization is analyzed and experimentally verified.(3)The experimental scheme for multi-carrier generation is discussed. The different impact factors to influence the flatness and stability of multi-carrier are analyzed, including the asymmetric property of single-sideband modulator, the imbalanced DC bias voltages, the imbalanced RF drive signals, unsatisfactory performance of the filter and the output power of the amplifier and polarization controller function. On the basis of the above analysis, the experimental optimization of the key parameters and the selection of suitable devices are investigated to generate50carriers with high flatness and high stability. The maximum peak power difference and the root mean square (RMS) are1.5dB and0.3dB, respectively, which is better than the indicators of domestic and foreign counterparts.(4)Applying high quality multi-carrier source to set up the2.56Tbit/s transmission system, and analyzed the transmission performance. Moreover, the different modulation formats are first innovatively applied to modulate the multi-carrier source as the adjacent channels, to simulate the actual WDM hybrid transmission system for studying the impact of the nonlinear effects of cross phase modulation on the performance of256Gbit/s PDM-RZ-16QAM signals.In summary, this thesis is focused on the polarization control technology, frequency-locked multi-carrier generation and application in high-speed optical fiber communication systems. The thesis work is concentrated on solving practical problems, by adopting the physical and mathematical models with innovative ideas and solutions, and gets the experimental verification. |
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