| In high bit rate (10G bit/s and beyond) WDM optical transmission systems, the maximum link length that can be covered without the need for signal regeneration is limited by chromatic dispersion (CD) and polarization mode dispersion (PMD) in single mode optical fiber. This will cause optical pulse broadening and finally cause inter-symbol-interfere which corrupts severely the performance of optical communication system. So some solutions (optical, electronic) for overcoming the limitation have been proposed in the optical system. It is well known, as metropolitan networks using standard single-mode fiber (SSMF) are upgraded to 10 Gb/s, some form of chromatic dispersion (CD) compensation is required. Previous research shows CD is a static impairment, causing intersymbol interference (ISI), which leads to significant penalties for over 60-km SSMF at 10 Gb/s. Tradition dispersion compensation module adopts the passive optical components. These methods use lots of expensive and bulky optical elements to do the inverse effects of the dispersion on the transmitted signal. Though this method works, but comparing with Electronic Dispersion Compensation, they have many disadvantages such as the less adaptability. To combat CD, electronic dispersion compensation (EDC) is attractive because it avoids the use of optical modules which are expensive, bulky, and have high optical loss. EDC can provide an adaptive and cost-effective solution suitable for integration with other receiver functions. As a new technology for fiber dispersion compensation, Electronic Dispersion Compensation (EDC) is gradually being applied in practical projects.The focus topic of this thesis is the adaptive Decision Feedback Equalizer technology. We first describe the basic principle of dispersion compensation, on this foundation, and introduce several of electronic compensation technology: linear equalizer-feedforward equalizer; nonlinear equalizer including Decision Feedback Equalizer (DFE) and Maximum Likelihood Sequence Estimator (MLSE). By comparison, the more suitable dispersion compensation technology of fiber-optic communication systems is chosen as DFE. Then we analyse and make a research the algorithm of the adaptive equalizer that is more suitable for actual need. And lay the foundation for the adaptive technology, besides, which provide a basis for the following performance simulation.Electrical dispersion compensation equalizer is a cost-effective element in optical communication OOK systems in the presence of chromatic dispersion. The optimization of training sequence and taps for the electrical adaptive decision feedback equalizer in a single-mode fiber communication system is studied in this paper.10-Gb/s transmission over 100km and up to 180km of single-mode fiber without any in-line dispersion compensation is demonstrated. The simulation results show that the ISI can be eliminated effectively with the ADFE in the optical Single-Mode Fiber (SMF) communication systems. For the sake of disadvantages, the simulations showed that it's not necessary for optical fiber communication system to make use of double the bandwidth of transmission signal. With a transmission distance up to 250km without in-line dispersion compensation by the use of the best sampling point, present metropolitan area networks can be efficiently upgraded and expanded to accommodate fast development of expanding citiesThis thesis presents 10Gb/s simulation results showing the performance of ADFE in SMF communication system links. Transmission distances up to 180km are considered to demonstrate the limits of this technology. Of particular interest for the systems is the maximum achievable transmission distance without any in-line dispersion compensation. Compensator is the primary component of EDC. FFE and DFE are commonly used. A simulation is done in an optical system with 10Gbit/s and OOK modulation. The suitable FFE and DFE architecture and length of the training sequence are given by the simulation results in this situation. |
PDF Full Text Request