Photonic Combinatorial Network for Contention Management in 160 Gb/s-Interconnection Networks Based on All-Optical 2$\,\times\,$2 Switching Elements

A modular photonic interconnection network based on a combination of basic 2times2 all-optical nodes including a photonic combinatorial network for the packet contention management is presented. The proposed architecture is synchronous, can handle optical time division multiplexed (OTDM) packets up to 160 Gb/s, exhibits self-routing capability, and very low switching latency. In such a scenario, OTDM has to be preferred to wavelength division multiplexing (WDM) because in the former case, the instantaneous packet power carries the information related to only one bit, making the signal processing based on instantaneous nonlinear interactions between packets and control signals more efficient. Moreover, OTDM can be used in interconnection networks without caring about the propagation impairments because of the very short length (<100 m) of the links in these networks. For such short-range networks, the packet synchronization can be solved at the network boundary in the electronic domain without the need of complex optical synchronizers. In this paper, we focus on a photonic combinatorial network able to detect the contentions, and to optically drive the contention resolution block and the switching control block. The implementation of the photonic combinatorial network is based on semiconductor devices, which makes the solution very promising in terms of compactness, stability, and power consumption. This implementation represents the first example of complex photonic combinatorial network for ultrafast digital processing. The network performance has been investigated for bit streams at 10 Gb/s in terms of bit error rate (BER) and contrast ratio. Moreover, the suitability of the 2times2 photonic node architecture exploiting the earlier mentioned combinatorial network has been verified at a bit rate up to 160 Gb/s. In this way, the potential of photonic digital processing for the next generation broad band and flexible interconnection networks has been demonstrated.