1412 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 16, NO. 5, MAY 2004 Fast and Widely Tunable Optical Packet Switching Scheme Based on Tunable Laser and Dual-Pump Four-Wave Mixing Dimitrios Klonidis, Christina (Tanya) Politi, Student Member, IEEE, Michael O’Mahony, Senior Member, IEEE, and Dimitra Simeonidou, Member, IEEE Abstract—An optical packet switching scheme based on a fast electronically controllable tunable laser dual-pump four-wave mixing for wavelength conversion and an arrayed wave- guide grating for passive routing is examined. This scheme can realize ultrafast packet switching and large port switch fabrica- tion, required in next-generation core optical packet routers. The performance is examined in terms of packet-based bit-error-rate measurements for packet-by-packet switching. Design issues are also discussed. Index Terms—Optical frequency conversion, optical switches, packet switching, semiconductor optical amplifier (SOA). I. INTRODUCTION F UTURE communication networks are going to be deter- mined by the data-centric Internet-Protocol-based nature of the accommodating traffic. Optical packet switching is an emerging technology that can efficiently support bursty traffic and offer optimized bandwidth utilization. For the core of the optical network, the optical packet switches must be scalable to a large number of ports each capable of operating at high bit rates of more than 100 Gb/s, in order to support large amounts of traffic. The work presented here is part of the OPSnet project, which examines the realization of an optical packet switch based on the requirements stated above. II. SWITCHING SCHEME FOR OPTICAL PACKET SWITCHED NETWORK The proposed switching scheme for the OPSnet project is shown in Fig. 1. The design is based on the wavelength routing scheme previously reported and demonstrated in project WASPNET [1] and comprises a tunable wavelength converter (TWC) followed by a passive wavelength selective device: here, an arrayed waveguide grating (AWG). Incoming packets are first demultiplexed and a part of the signal is tapped for header extraction and electronic processing. Current advances in the technology of field programmable gate arrays (FPGAs) allow serial input–output streams up to 10 Gb/s and parallel processing at 840 Mb/s (e.g., Virtex-II Pro series by Xilinx), realizing fast header processing, calculated to be less than Manuscript received July 30, 2003; revised January 14, 2004. The authors are is with the Photonic Networks Research Laboratory, Univer- stiy of Essex, Colchester CO4 3SQ, U.K. (e-mail: dkloni@essex.ac.uk). Digital Object Identifier 10.1109/LPT.2004.826135 Fig. 1. Core optical packet switch architecture. Schematic diagram that shows the main elements of the switch. 10 ns when the appropriate programming is applied. After the header bits are processed, the output from a -look-up table is used to tune the laser, which controls the TWC and the payload is converted and routed to a specific output port of an AWG. Contention can be resolved by routing the packets to optical buffers through designated output ports of the AWG. An output processing unit is required after the AWG, to rewrite the header and convert the packets into a wavelength suitable for the network. Similar electronically controllable packet routing schemes have also been presented in [2] and [3]. However, the main drawbacks of these schemes and most of the recently developed optical packet-based node designs are the limitations in the accommodated payload bit rate and/or the switch dimension- ality. Packet switching schemes that are based on cross-gain or cross-phase modulation in semiconductor optical amplifiers (SOAs) are limited in bit rate and complex configurations are required for higher bit rates. Additionally, these techniques exhibit nonuniform performance over the conversion spectrum and depend on whether up or down conversion is used. This limits the dimensionality of the switch, as the transmission characteristics will vary with change of port. In order to support bit rate transparency and increased di- mensionality for the proposed switching scheme, dual-pump four-wave mixing (FWM) is used. This technique retains the bit rate transparent characteristics of single FWM in SOAs [4] and additionally resolves its tunability limitations [5]. Moreover, it exhibits uniform performance over a wide spectral tuning range without distinguishing between down or up conversion [5]. That allows equal performance over the whole bandwidth, enabling the realization of large port switch fabrics. In this letter, the dual pump FWM technique has been uti- lized as a wavelength converter controlled by a tunable laser. 1041-1135/04$20.00 © 2004 IEEE