The Investigation On Key Techniques For High Speed Passive Optical Nerwotks

Under the background of the popularization of high bandwidth business and the rapid development of network, our country increase the investment of technology on passive optical network, so as to support the development of FTTx technology. In this case,10G PON and40G PON technology become the trend of the future development. With the increase of network speed, some influences of link damage factors, such as CD and PMD, have been increasing, which can be ignored in low-speed system. For example, the influence of chromatic dispersion may cause the Inter-symbol interference, and then limit the transmission distance, which can’t meet the system requirements of long distances. Therefore, in order to suit the transmission requirements of high speed PON system, we need to find out new modulation technique to improve the tolerance of link damage factors. Moreover, taking the cost of system into account, not only need we to improve the performance of system, but also to reduce the complexity of system design, so as to reduce the cost of the system. Based on this background, the modulation technology of high speed passive optical network becomes a hot topic in next generation PON areas.This paper mainly researches on the modulation technology and demodulation technology of high speed PON system, and obtains a number of innovative research achievements. The main work and innovative contributions are listed as follows.1. In view of high-cost and hard-integration problems caused by the using of phase modulator, such as MZ modulator, to generate duobinary signal, we propose to use electro absorption modulator to achieve phase modulation, not only satisfying the high-speed system’s transmission requirements(Transmission distance≥40km),but also reducing the cost of transmitter. Moreover, we carry out simulation to prove the feasibility of the proposed scheme.2. In order to overcome the inter-symbol interference, caused by polarization crosstalk, we propose a novel modulation format of50%RZ polarization interleaved multiplexing DQPSK for high-speed self-homodyne receivers. By introducing a half period time’s dislocation, we load different polarization state information in different time, so that the influence of the polarization crosstalk can be avoided effectively. After building a simulation platform, we verify the effectiveness of the proposed method.3. In the uplink of40Gbit/s coherent TDMA PON system, processing delay is so large that it couldn’t fix the burst mode very well. In order to solve this problem, we propose an algorithm to adapt the compensation of linear damage and the de-multiplexing of polarization division quickly. Through the optimizing of initializing method for adaptive equalization module’s tap coefficient, the algorithm could switch the tap coefficient fast according to different burst packet information. The simulation results show that the above algorithm can reduce the adaptive equalization convergence time and the complexity of DSP processing more than half.