| In recent years, along with the accelerating space of tri-network integration, services of bandwidth-hungry applications such as interactive television (IPTV), high definition television (HDTV) and network video continue to emerge, which lead to the explosive growth of network information data and the urgent demand of high bandwidth for the end users. What’s more, as with the development of internet of things, remote medical treatment and video on demand, the users’demand for bandwidth greatly increase. During the global wave of broadband evolution, wired access as a way of last mile access can no longer meet the need of current development and gradually become the bottleneck of global network progressing. As a result, the research on next-generation passive optical network is imminent, orthogonal frequency division multiplexing (OFDM) with its inherent advantages of high spectrum efficiency and high resistance to dispersion capacity is considered as one of the most promising technical for next generation passive optical network.This paper takes the upstream of OFDM-PON as the research object, starts with the basic theoretical analysis and formula derivation, then proposes a novel cost-effective OFDM-PON uplink system based on RSOA. Subsequently the paper firstly makes an intensive study for the related OFDM technologies of modulation and demodulation at transmitter and receiver and then gives a radix-4FFT fast signal processing algorithm based on CORDIC algorithm. Thirdly the impacts of various factors like laser width, cyclic prefix, chromatic dispersion and channel estimation are simulated and analyzed. The main research contents and relevant achievements are listed as follows:1. The paper has made an introduction of the application background and corresponding advantages of OFDM technology. And also focus on their overseas and domestic research status.2. Make a presentation of the basic principle of OFDM technology and its cyclic prefix and channel estimation module and disadvantages. Present different types and constructs of PON, especially introduce the operation of OFDM-PON and two different kinds for realization: DDO-OFDM-PON and CO-OFDM-PON. 3. On the basis of mastering the principle of4-FFT and CORDIC algorithm, the paper gives a high signal processing way by using radix-4FFT algorithm based on CORDIC, realizes the modulation and demodulation of OFDM in electrical field. The whole system is coded by VHDL, functional simulation and time simulation are accomplished on Modelsim and QuartusII software individually, the hardware implement is performed on Altera Cyclone II development board.4. The paper proposes a novel lOGb/s colorless OFDM-PON uplink transmission system based on RSOA modulation. In the loopback scheme, ONUs in the adjacent area share the same wavelength. There is a seed light sending optical carrier used in upstream modulation by downstream transmission at OLT, thus achieves each wavelength can be assigned to the utilization of two ONUs. The paper also make an analysis of different cyclic prefix to dispersion cumulative effect, laser line-width to Q factor effect under different transmission distances and channel estimation and equalization to phase shift effect of constellation diagram.5. Make a conclusion of the paper and put forward some prospects for further research. Present some simulation results for uplink transmission system of OFDM-PON based on64QAM and the corresponding difficulties of higher order modulation. |
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