A Photonic Knockout Switch for High-Speed Packet Networks

Recent advances in photonics have prompted new widespread interest in photonic switches with capacities orders of magnitude higher than possible with electronics. Considerable attention has been focussed on photonic circuit switching. In this paper, we consider the case of a high-performance packet switch which employs a photonic cross-connect fabric to route very wideband data packets from input to output. Packet contention is accomplished via a much slower electronic controller, based on the Knockout Principle operating in parallel with the optical cross-connect. Specifically, we propose the use of a wavelength-division-multiplex fabric whereby high-speed (2-4 Gb/s) packets are regenerated before modulating a single-frequency laser at each switch input. The optical signals from various inputs are summed in a Star Coupler and then broadcast to the different coupler outputs. Each coupler is equipped with a small number (L) of tunable receivers arranged in a parallel manner, each preceded by a power splitter so that up to L simultaneous packets can be received by each output. The L packets so received are converted into electronic signals before stored in an L -input one-output first-in-out (FIFO) buffer. The buffered packets are read out one at a time, and the FIFO packet sequence is always guaranteed. Not only does this architecture achieve the best delay-throughout performance, but, remarkably, modularity is such that the optical complexity grows linearly with the number of switch ports. The value of L needed to keep the packet loss probability below 10 -6 is 8, and we present a technique to reduce this by a factor of two. The high capacity potential of such a switch becomes evident via a simple example of a 64 x 64 configuration interfaced to 4 Gb/s input/output lines, yielding a total capacity of 256 Gb/s. Advantages compared to several possible alternatives approaches are A Photonic Knockout Switch for High-Speed Packet Networks L