Study On WDM-PON System Based On Advanced Modulation Technique

With the continuous growth of the demand for information, the user side of the access network bandwidth requirements are also getting higher and higher. The technology of WDM(Wavelength Division Multiplexing) in Passive Optical Network(PON) optical access network systems has become a hot topic of NG-PON2. As the ultimate direction of development of access technologies, WDM-PON system has the characteristics of high transmission rate, good security and large transmission capacity. Because of these characteristics, WDM-PON has become the mainstream solution to solve the last mile bottleneck of the future optical access network bandwidth. However, the introduction of WDM-PON system access technology can lead to the enhancement of dispersion and nonlinear effects, and the use of advanced optical modulation technology can effectively reduce the impact of these factors on the performance of the system. In particular, the application of joint transmission code not only makes the transmission structure of WDM-PON system to be further improved, but also greatly reduces the construction cost of the system. These make the commercialization process of the WDM-PON system to enter a new development milestone.This thesis mainly focuses on the application of various optical modulation techniques and advanced modulation techniques in the WDM-PON system of the high speed optical transmission system. Firstly, the generation mode and demodulation principle of the three modulation formats of intensity modulation, correlative coding and phase modulation are introduced. At the same time, the damage factors of optical fiber transmission are discussed and the simulation comparison between the intensity modulation format and the partial code type in the phase modulation format is carried out. According to the simulation results, system construction costs and other factors, the intensity modulation format of IRZ with better nonlinear tolerance and correlative coding of Duobinary with better dispersion tolerance are selected to form an advanced modulation format—IRZ-duobinary. The relationship between residual dispersion and OSNR that system required will be analyzed. The simulation results show that IRZ-duobinary can not increase the OSNR of the system with the increase of the dispersion tolerance, so it has more cost-effective in the practical application.Secondly, the advanced combined modulation format IRZ-duobinary is combined with the high speed WDM-PON transmission system and multicast re modulation system, and the performance of the system is simulated and analyzed. In the high speed WDM-PON transmission system, the IRZ-duobinary downlink and IRZ uplink re-modulation scheme is adopted. In the Multicast re-modulation system based on IRZ-duobinary downlink, the IRZ-duobinary code is used to carry both the point to point unicast service and multicast services, and the multicast service is controlled by Mach Zehnder modulator.In short, the simulation results of the two systems show that the overall performance of WDM-PON system is improved by using the advanced combined modulation format—IRZ-duobinary as the modulation code, which reduces the cost of the system construction. It is of great significance to promote the further development of WDM-PON and has a good application prospect in the development of high speed transmission system in the future.