The Study On Essential Technologies Of Coherent Pon Systems

The exponential growth of IP data traffic never slows down, and now is powered by P2P and HD video services. The ever-increasing demand of bandwidth is pushing the ISPs to upgrade their access networks, which has been the bottleneck of the whole network.The Next-Generation PON is expected to provide at least40Gbit/s at downstream direction.Moreover, ISPs are asking for longer coverage distance and higher split ratio to serve more customers while keeping the ODN passive to control OPEX.This paper focuses on introducing coherent detection into PON, so as to provide better sensitivity and higher dispersion tolerance fulfilling the performance requirements on NG-PON. Main works of this paper are listed as follows:Studies on high-capasity PON system scheme is carried out, mainly focusing on transmission scheme in upstream and down stream. In down stream, Coherent PM-DQPSK, DI-DD-DQPSK, DD-OFDM and CO-OFDM are discussed in various aspects including performance, complexity and cost. Proper scenarios are proposed for each shceme after the comparing. In up stream direction, DI-DD-DPSK is compared with conventional OOK, mainly concerning sensitivity performance.In order to reduce the cost of coherent PON system, a single source coherent ONU scheme is put forward, which can deliver almost the same performance as conventional du-LD scheme with lower cost. Analysis on Ryaleigh Backscattering and its impacts on coherent detection are carried out, and measures are taken in order to avoid related performance degradation. According to simulation results, penalty stems from RB impacts is only0.2dB for the receiver while no degradation is observed in the transmitted signal.Experiment system design is put forward based on the preceding works. Essential features are determined based on performance requirements and rusults of preceding analysis and simulations. Princepal function blocks and mechanisms are designed and procedures are described.