The dramatic increase in throughput demands from backbone transport data networks has propelled the development of all-optical wavelength-division-multiplexed (WDM) networks. As the capacity demands on these systems increase, the physical layer degradation becomes so severe that sophisticated signal processing techniques are necessary to maintain the quality of service. Channel nonlinearity differentiates multichannel fiber-optic systems from conventional wireline and wireless systems. Consequently, novel signal processing and communication theoretic approaches are required to design and analyze the channel; this research project addresses this need. As a consequence, WDM system designs are improved and the data throughput available to society though these networks is substantially increased.
This research develops a discrete time-wavelength nonlinear model for the WDM system and uses this model to design powerful signal processing techniques. Up to now, the WDM channel has been considered as a set of parallel channels, ignoring the cross-channel effects or modeling them simply as noise. Motivated by techniques that have been so successful in wireless communications, such as multiuser detection, MIMO processing, multichannel precoding, etc., this research develops algorithms to apply to the WDM fiber channel that can produce substantial capacity gains. A two-dimensional discrete-time polynomial model for a WDM system is formulated to account for intra-channel and inter-channel linear and nonlinear effects. Multichannel processing algorithms across time and wavelength for interference mitigation are designed and evaluated. Since nonlinear interference limits the performance of networks, constrained coding to diminish this interference is used to trade capacity for performance. In all-optical networks, crosstalk emanating from other lightpaths can limit performance. Employing idle lightpaths judiciously provides multiuser coding and path diversity (redundancy and memory) to the entire network.
Level of effort statement:
At the recommended level of support, the PI will make every attempt to meet the original scope and level of effort of the project.
