| As the development of internet industry, network applications such as video on demand (VOD) have emerged and rapidly popularized. As a result, the demand for higher bandwith increased quickly. Original access network technologies, such as Asymmetrical Digital Subscriber Loop (ADSL) can hardly meet the needs of the user for higher bandwidth. Wavelength division multiplexing passive optical network (WDM-PON), depending on it’s advantages such as higher network bandwidth and easy to realize for the following system upgrade, has gained more and more researchers’attention and became one of the possible realization technologies for next generation access network.As one of the researchers, the author participated in the National Natural Science Foundation project "Mechanism research and experimental validation of optical RF signal processing based on RSOA" and "Research of all-optical signal processing technology based SOA and MZI". During the research time, with the help of optical communication simulation software VPI transmission maker8.5, circuit design software Mentor Graphics2005and other laboratory owned access network plantforms,we studied the design and implementation method for lOGb/s WDM-PON svstem with colourless ONU based on bandwidth limited RSOA. The main research contents of this paper are as follows:Firstly, the development situation of the widely used passive optical access network technologies, such as EPON and GPON, are analyzed. Based on the fallbacks of the mainstream technologies, WDM-PON, which is recognized as a possible technology for the next generation access network is introduced. Detailed instructions and comparirations on key technologies for the development of WDM-PON system, such as the realization of colourless ONU, design and implementation of wavelength dividion multiplexing device, forward error correction coding (FEC) and optical/electronic equalization, are given.Secondly, we propose our own WDM-PON design plan based on RSOA and drow related circuit schimatic with electronic circit design software Mentor Graphic2005. In the design plan, RSOA is choosen as the key device to realize colourless ONU. SERDES chip is choosen to realize the function of PMA layer while functions of PCS layer are realized in FPGA chip.Besides that, FEC coding, electronic equalization and optical equalization are used to conquer the defect of limited bandwidth of RSOA in the design plan.Thirdly, an error signal difference based LMS (ESD-LMS) algorithm, which updates its stepsize according to the difference of error signal, is proposed. Several key parameters of the adaptive filter based on the proposed algorithm is analyzed in detail and MATLAB simulations are implemented to show the performance of the proposed algorithm in situations such as channel equalization and system identification.System simulation is created to explore the performance of the system based on the WDM-PON design plan with RSOA based colourless ONU. The performance of the proposed algorithm in a scheme of10GB/s operation over20km fiber transmission in which directly-modulated RSOA is introduced. The BER measurement and eye diagrams show that the proposed VS_LMS algorithm can lower the BER level and improve the eye opening condition. About2.5dBm receive sensitivity improvement will be achieved at BER=1.0E-4level after20km bidirectional transmission when the injection power is about-20dBm. The relationship between BER level and iteration numbers of the electronic equalizer is investigated which shows about two bytes’training series are needed for the proposed algorithm to reach steady state. |
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