Upgrading PON With Orthogonal Modulation And Upstream Remodulation

With the rapid development of the Internet and the increasing popularity of mobile intelligent terminal, a variety of new service and the diversification of user demand have emerged in recent years, which stimulate communication networks to develop for high rate and large capacity. So the time division multiplexing passive optical network (TDM PON) extensively deployed in access network can’t satisfy our demand for bandwidth. Wavelength division multiplexing passive optical network (WDM PON) is particularly attractive in the research of next generation access network.In this paper, our research is conducted about the smooth upgrade of PON. The paper focuses on how to achieve gradual and smooth upgrade to the next generation WDM PON without any change requirement for the existing TDM PON.Firstly, we simply introduce the development of the access network, the classification of PON and the research background in PON upgrade. Then we innovatively propose several evolution schemes based on orthogonal modulation and remodulation. The upgrade signal is respectively modulated by means of polarization shift keying (PolSK), frequency shift keying (FSK) and differential phase shift keying (DPSK). In the downstream transmission, we compare the differences in eye diagrams and bit-error-rate curves of the previous PON signal before and after the evolution, which show small crosstalk between unchanged TDM PON and upgraded WDM PON. In the upstream direction, remodualtion is applied on the downstream upgrade signal to avoid the use of light source in optical network unit (ONU) and low pass filter is used to simulate uplink receiver of low rate. So the interference from downlink signal can be greatly reduced. The experiment results demonstrate that upgrade PON coexists well with the current TDM PON in the legacy installed infrastructure and upstream remodulation is employed to realize colorless ONU in WDM PON in our smooth evolution schemes, which prove to be feasible.