Optical signal processing in future broadband dynamic optical networks

Communication Networks form the basis of our modern information age providing efficient transfer of information around the globe. Communications networks are akin to the transportation system where optical fibres form the roads and network nodes are equivalent to the traffic light controlled junctions. Optical fibre technology has revolutionised networks by providing high capacity point-to-point links - the autobahns of the transportation system. However these are currently still interconnected with nodes based on limited speed electronic processing which become bottlenecks in the system. The solution to this problem is to introduce high capacity optical processing into the network to replace the current electronic processing. This will result in a flexible network that is able to respond (dynamically) to changes in traffic and demand. It will be more scalable as the nodes only have to deal with traffic destined for that node, all other traffic is bypassed in the optical domain.The two major obstacles to implementing the required dynamic optical networks are the management of the optical signal distortions that arise in these networks and implementation of efficient optical switches. Signal distortions that lead to errors are more problematic in dynamic optical networks because the signal remains in the optical domain, accumulating distortions and noise throughout the optical network. This is in contrast to current networks where the signal is converted to the electronic domain at every node for processing and error correction before re-transmission. Additionally in a dynamic optical network these distortions depend on the route that the signal takes through the network. In order to ensure error free transmission of the optical signals it is necessary to periodically correct for these distortions in the optical domain using a technique known as optical regeneration. Optical switches are used to control the routing of information in the optical domain through the network in order to ensure it reaches the intended destination without the need for conversion into the electronic domain.All optical processing technologies, specifically optical regeneration and the ability to change the wavelength of the optical signal (tunable wavelength conversion), can be used to compensate for the distortion and implement optical switching. In this proposal I consider both functionalities as the particular implementation exploits the same physical processes in nonlinear optical devices. The major aim of this fellowship is the identification and verification of suitable optical technologies for optical processing in dynamic optical networks. This will be achieved through the development of an advanced characterisation technique to assess potential optical devices (including novel materials) and the implementation of an experimental dynamic network test-bed combined with a modelling framework. This test-bed is designed to be independent of the particular network architecture so that the research focuses on solving the principle physical issue of mitigating the increased and variable levels of signal distortion that arise in dynamic networks. The multi-channel test-bed will operate at a bit rate of 40Gbit/s and is designed to emulate signal distortions present in a real dynamic network with reconfiguration times ranging from milliseconds to nanoseconds. The aim of the test-bed will be to enable the investigation and testing of these optical subsystems both independently and together to evaluate both the individual performance and interoperability of these.In summary this research proposal explores the requirements and performance limits of optical processing in dynamic networks. It combines the characterisation of potential optical devices with system modelling and experimental verification in a realistic network scenario in order to assess the suitability, performance and requirements of these devices in dynamic networks.