Research Of The Multiplexing Technology In RoF Broadband Access Network

As the advent and development of the information age, Man has demand for increasing knowledge and information, which presents both opportunities and challenges to the development of communication technology. Optical fiber communication is a milestone of communications technology, and fiber has applied widely in the backbone network and MAN (Metropolitan Area Network) and penetrated to the access network because of its advantages, such as ultra-high bandwidth and ultra-low loss. The access network is information bearing source, and traditional access network is difficult to support broadband and multimedia services and limit the development of information network, because it takes copper wire as transmission medium of which there is bottleneck of throughput, while the new generation of access network based on the principle of fiber over radio broadband access both makes use of advantage of fiber, such as ultra-wideband, ultra-low loss and freeing from electromagnetic interference, and makes use of the strength of mobile access, such as anytime, anywhere, and convenient and flexibility. It is the inexorable trend of future broadband access network, and have broad application prospects.For further improving the utilization of fiber, and excavating more bandwidth resources, we can adopt various multiplexing technologies, such as WDM, OCDMA, OTDM, and so on. WDM is regarded as the most promising optical-transmission technology at present, according to its unparalleled advantage compared with traditional fibre communication, such as huge capacity, transparent for signal, high rate, and high performance price ratio. OCDMA can implement high rate and broadband access at optical stage and signal in multiple Base stations (BS) sharing the whole channel because of its asynchronous access property, flexibility, and transparency for various radio signal, and easily add/drop the number of BSs anytime and anywhere, which can lower the cost of system at the same time.In this paper, we do much research of multiplexing technologies in RoF broadband access network. First we do much research in OCDMA-based RoF network, and present a double-ring network structure of RoF access network. Then we simulate and analyze the performance of system, which adopts PC code, MDW code, ZCC code and OOC code as user after transmitting 20km in the Sing mode fiber (SMF), discuss the relationship between carrier noise ratio (CNR) and code rate and number of BSs connected, and draw curves of CNR. Finally, we conclude that CNR and performance of system is declining as the increasing of the number of BSs and improving of code rate as well as ZCC code is superior to the three other codes. Subsequently, we do much research of a combination of WDM and OCDMA technology in the RoF system. First we simulate and analyze the CWDM plus OCDMA-based RoF system, and get the system's curve of CNR in certain BS (10GHz) of certain wavelength (1311nm) in high rate (2.2Gbit/s) in case of 16 CWDM channels with 20nm spacing in RoF when adopting PC code and OOC code. Likewise we conclude that WDM/OCDMA-based RoF can make full use of wavelength, and increase the number of BSs connected to an extreme and demonstrate the feasibility in the actual application.