The Research On Optical Access Technology Based On WDM And OCDMA

Access network transports voice, date and video to end-users. PON has becomed an important access method now because it possesses broadband transporting capability, easy to maintenance, reduces access cost by sharing transporting medium and can transform to FTTH smoothly. However, the traditional access technology suffers from limited bandwidth, low assembly flexibility and low network security, which obstructs the network from delivering integrated services to users. Thanks to the maturity of optical components and multiplexing technology, optical access have become practical.In this paper a novel PON based on WDM and OCDMA is presented, which aims to resolve the problems states above. We analyse the system in detail by both theoretical anaysis and numerical simulations and get the result that the performance of our system can be better improved by increasing the transmitter input power, which can use our proposed ring resonator laser based on PPLN-OPO.The main contents and key creation points of this dissertation are as follows:1. A new scheme of WDM-PON is given, which provides practical migration steps from current-generation TDM-PON to future backward compatible WDM-PON. The new architecture is based on a double-collector-ring and several distribution stars connecting the CO and the users. Besides, we design the RN and the ONU. Also we propose the fast tunable lasers in the OLT not only generate downstream data traffic but also provide CW bursts for their ONU's upstream data transmission.2. The OCDMA, especislly the theory of the OOC is investigated. Then we study the mathematics characteristic of the code length, weight, threshold and the number of user, and give their simulation in relation to the MAI, which produces an asymptotic floor to the bit error rate (BER) performance. Based on the conclusion we get, we construct a set of (961,6,1)–OOC sequence via the algorithm of the wilsons's primitive root to apply on our system. At last, We demonstrate the WDM-OOC have better performance than the common OOC, which prepare for the design of our OCDMA-WDM-PON futher.3. Combined the architecture of the WDM-PON with the OOC we study previously, we give the whole system of the network, we calculate the MAI 1.9* 10?9 W, deduce the sentence threshold 10 5 electron number, and analyse the APD receiver's performance due to the MAI and other noises. Then we analyze in detail the scalability based on power allocation and system transmission performance of such a network. Simulation results indicate that the proposed scheme is feasible and by increasing our laser transmitter's power, the novel design can improve the performance dramatically.4. In the design of laser, we introduced a ring resonator based on an PPLN-OPO. The experimental study is conducted on an LD-single-end-pumped single-frequency Nd:YVO4 unidirectional ring laser, with which the optical parametric oscillation is achieved by pumping the PPLN. While the average pump power is 1.6W, an high average laser output power of 56.9mW is obtained at 1.5μm, with a linewidth of less than 0.06nm. This laser can apply in the area of our proposed PON, combined with the OCDMA technology, we can realize the Free Space Optical secret communication.