| Driven by rapid growth of multimedia and Internet applications, bandwidth requirement of access network grows exponentially. Since optical fiber communication takes advantages of large capacity and long reach, utilizing optical fiber as transmission medium can significantly increase capacity and span of access network. Fiber to the home (FTTH) is considered as "future-proof" solution to access network. Among various FTTH technologies, passive optical network (PON) is cost-effective and thus adopted widely. Passive optical network (PON) is cost-effective because there are no active equipments in the network which can cut down the cost of maintenance. Main technologies in PON system include EPON and GPON, both of which belong to time division multiplexing PON(TDM-PON). Nowadays, TDM-PON can provide10Gb/s downstream and upstream capacity which is the maximum capacity that TDM-PON can provide. Next generation PON should achieve capacity of at least40Gb/s, which is a very difficult task for TDM-PON.Orthogonal Frequency Division Multiplexing (OFDM) enjoys such advantages as high spectrum efficiency, resistance to chromatic dispersion, compatibility with TDM-PON. Capacity of OFDM can be increased by using high level modulation format. So we can apply OFDM to PON system to increase the capacity of future access network.In modern life, our demand for bandwidth is growing which forces us to research on new standards for PON. NG-PON2is a new standard for PON in which the bit rate should be at least10Gb/s, the transmission length should be longer than20km, what’s more, it should also be able to provide services for at least32users, at last the most important is that it should also make the ONU colorless. OFDMA-PON system can meet with all the requirements in NG-PON2because OFDM in OFDMA-PON is not only a kind of modulation but also a kind of access method for ONUs. The thesis overviews principles of OFDMA-PON. OFDMA-PON system performances are studied by stimulations. Of course the OFDMA-PON system includes both upstream and downstream. Main contributions of this thesis are summarized as follows:1) Through extensive research, the thesis overviews OFDMA-PON research background and gives an outlook of PON development.2) The thesis makes some research on the basic principle of OFDMA-PON. These basic principle includes the principle of OFDM, the principle of optical OFDM and OFDMA-PON.3) The thesis proposes a new single side band modulation method which is applied to direct detection OFDM-PON sytem(DD-OFDM-PON). This new method combines ACO technology with compatible single sideband(comp SSB) technology. This new single sideband modulation method is called ACO-SSB in this thesis. This part make some researches on the principle of ACO-SSB. Then a lOGb/s DD-OFDM-PON simulation system is built to verify to performance of ACO-SSB.4) Make massive research on20Gb/s upstream OFDMA-PON system. The research include three aspects. First, the thesis research on the access method of upstream OFDMA-PON system and then give out design result. Second, the thesis also complete some researches on channel equalization algorithm. For example training sequences are used to estimate the chromatic dispersion in fiber link. Third, a20Gb/s upstream OFDMA-PON simulation system is built by some simulation tools to verify the basic researches. Meanwile the thesis give some analysis for the simulation result. |
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