Study Of Plastic Optic Fiber Access Network Based On OCDMA

In this paper plastic optical fiber (POF) access network based on optical code-division multiple access (OCDMA) technique is proposed. The relevant issues of this access network are also studied.Recently, optical transmission using graded index POF has received much attention due to its prospect of offering high bandwidth, which can transmit up to 2.5Gbit/s (PMMA based GI-POF) ~ 11Gbit/s or more than (perfluorinated polymer based GI-POF) over 100m long. The large core diameter of POF makes handling easy. And it enables the use of inexpensive injection molding polymer connectors. This result in low cost. In addition, it has the following virtues that are light weight, flexibility and easy maintain. All above make POF a very attractive candidate as transmission media in access network. It requires that the bandwidth of system is larger than that of signal being transmitted in CDMA system. As we known, the differential mode attenuation and mode coupling of POF make the bandwidth much greater than would be expected from their index profiles. So POF access network combined with CDMA gives us an effective solution to FTTO or FTTH.Furthermore, upward signal in an access network is characterized by its burst nature, for other synchronous multiplexing schemes, such as time-division, or wavelength- division multiplexing where domain slots are permanently allocated, this waste resource when a user is idle. In contrast, OCDMA system permits a destination station to capture a packet rather than the entire communication bandwidth. It allows concurrent access to a number of network users without access delay and allocates bandwidth, as it is needed. So OCDMA system can be effectively used to support multimedia real-time communication.In conventional OCDMA system only allows finite units to transmit and access simultaneously according the number of channels which be restricted by BER. More and more new unit joins the network as the growing of network scope. To resolve the problem a novel protocol is proposed in this paper. The number of data channels does not restrict the number of units in the network. This protocol can efficiently support variable-sized messages, and any new unit can join the network at any time without requiring network initialization. To implement the demonstration, each optical network unit is equipped with a fixed optical encoder and a fixed optical decoder, both of which are tuned to the control channel. Each optical network unit also has a tunable optical encoder and a tunable opticaldecoder that can operate at any one of data channels independently. The tunable optical encoder/decoder employing planar holographic optical processors (HOPs) in this system may be a low-cost fabrication. The network throughput and average delay using various system parameters has been investigated by numerical analysis and simulation experiments. It is showed that the dynamic control protocol in this POF access network based on OCDMA technology is valid and efficient.High bandwidth of POF is very suitable for CDMA technology, OCDMA is one of most attractive solution which can assure the performance of real-time multimedia access network, as the most cost-effective technology. The effective solution to FTTO or FTTH is inexpensive and that gives us a new roadmap.