| As one of the best solutions for the next generation broadband optical accessnetworks, OFDM-PON has been attracting tremendous attention from extensive R&Dinstitutes and researchers, due to its high spectrum efficiency, strong robustness tochromatic dispersion, low hardware complexity and great flexibility of dynamicresource scheduling and allocation. With the further development of broadband opticalfiber access networks, OFDM-PON systems are required to support much more userswith much higher access rate and meantime the overall cost for the OFDM-PONsystems should be maximally reduced.In this thesis, OFDM-PON with novel source-free ONUs and interference-freeupstream transmission have been designed and experimentally verified so as to solvethe problem mentioned above. Based on the deep analysis of current theories andtechnologies about the source-free ONUs in the OFDM-PON system, the followingthree points are studied in this thesis:1. A novel approach of source-free ONUs in OFDM-PON has been investigated inwhich the ONU is source-free not only from the optical domain but also from theelectrical radio frequency domain. By utilizing this new scheme, expensive lasers andradio frequency sources could be completely removed and thus the overall cost of theproposed OFDM-PON system could be greatly reduced.2. The implementation approaches of ONUs which are source-free both opticallyand electrically has been studied and two schemes have been proposed to achieve novelsource-free ONUs based on the technology of polarization multiplexing and the effectof foure-wave mixing.3. The interference-free upstream transmission of multiuser OFDM-PON systemhas been discussed and a scheme utilizing optical comb has been introduced to achievenovel source-free ONUs and meanwhile support the interference-free transmission ofupstream signal from multiple different ONUs in the multiuser OFDM-PON system. |
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