Photonic digital processing for enabling next generation optical networks

Abstract

Elementary blocks, performing basic operations, are the building elements for complex subsystems implementing all-optical digital processing. They can enable next generation optical networks and optical computing overcoming electronic issues as bandwidth and power consumption. IntroductionThe increasing demand of fast and efficient computing systems is pushing the research towards the investigation of photonic digital processing. The main advantage of photonic processing with respect to electronic processing is the high speed [1], [2]. Nevertheless photonics is in its early stage and the realisation of complete all-optical computing system is still far, mainly due to the lack of efficient all-optical memories. Despite the present limitations, photonic digital processing shows promise in the applications where fast computation speed is required. One of these scenarios is represented by the all-optical short-range photonic interconnection networks. The improvement of the present high performance computing systems is hampered by the bottleneck of the chip-to-chip and chip-to-memory communication.The limits are the high wiring density, the high power consumption and the limited throughput [3]. Photonic interconnection networks can overcome the limitations of the electronic interconnection networks by guaranteeing high bit rate communications, data format transparency and electromagnetic field immunity. Moreover they can reduce the wiring density and the power consumption. In such networks photonic digital processing can be the most suitable paradigm for simple and ultra-fast control and switching operations, since it reduces the packet latency to the optical time-of-flight. In order to apply photonic digital processing for the controlling of the network data plane, complex functions must be available. Elementary logic gates as AND, NOR, NAND, NOT has been demonstrated with fibre, waveguide and semiconductor-based solutions. A fibre-based scheme exploits Cross Phase Modulation (XPM) in nonlinear optical loop mirrors structures [4]. A combination of pump depletion and Sum Frequency and Difference Frequency Generation (SFG-DFG) has bee exploited in a single Periodically Poled Lithium Niobate (PPLN) waveguide in [5] to obtain multiple basic logic operations. Semiconductor-based solutions exploit Semiconductor Optical Amplifiers (SOAs) followed by optical filtering [6], integrated SOAs in Mach Zehnder