Publications attached in Section IV. Additional Information To Appear in Technical Digest, OFC 2002, Anaheim, California, March, 2002 Optical-Label based Packet Routing System with Contention Resolution in Wavelength, Time, and Space Domains S. J. B. Yoo, Yash Bansal, Zhong Pan, Jing Cao, Vincent K. Tsui, Steven K. H. Fong, Yanda Zhang, Julie Taylor, Hyuek Jae Lee, Minyong Jeon, and Venkatesh Akella Department of Electrical and Computer Engineering, University of California, Davis, California 95616 yoo@ece.ucdavis.edu , Katsunari Okamoto Okamoto Laboratory, NEL, 6705-2 Naka-machi, Naka-gun, Ibaraki Pref., 311-0122, Japan okamoto@photo.nel.co.jp Shin Kamei NTT Photonics Laboratories, 162 Tokai, Naka-gun, Ibaraki-pref, 319-1193 Japan Abstract: We demonstrate a packet routing system compatible with optical-label switching and capable of contention resolution in wavelength, time, and space domains by combining tunable wavelength conversion, arrayed waveguide grating routers, and fiber delay lines. 2001 Optical Society of America OCIS codes: (060.4250) Networks, (060.4510) Optical communications 1. Introduction Rapidly increasing data traffic demands a scalable and data-oriented networking technology. Achieving packet switching directly in the optical layer can facilitate convergence of optical networking and data networking without relying on redundant optical-to-electrical, and electrical-to-optical signal conversions. The key challenge in realizing a multiwavelength optical-packet switching system lies in the lack of a viable optical random access memory (RAM) technology. Contemporary electronic routers rely on buffering and queuing in the RAM as the main mechanism for contention resolution. Fortunately optical-packet switching system can exploit an additional degree of freedom other than the time domain buffering—wavelength conversion. Contention resolution in optical packet switching system can be achieved by deflection in one or a combination of wavelength, time, and space domains. Optical routers may benefit from wavelength conversion as the primary means to achieve contention resolution. Unlike time buffering, wavelength conversion does not accompany packet latency, jitter, or sequence skews. Recent network simulations [1] have shown excellent performance in an all-optical packet switching system utilizing combined contention resolution in wavelength, time, space domains. This paper discusses an experimental demonstration of an all-optical packet switching system based on optical-label switching [2,3] and incorporating contention resolution in wavelength, time, and space domains. 2. Experimental Description Fig 1. illustrates a schematic of the optical packet routing system used in the experiment. The system consists of the optical router controller, the optical label extractor, the optical label detector, and a switch fabric. The optical router controller, implemented by a field programmable gate array (FPGA) includes the forwarding table, the scoreboard, and the arbitrator incorporating the contention resolution algorithm: (1)seek an alternate wavelength on the same output port, (2) if no such wavelength is available, seek an available wavelength in the local optical buffer delay line, and (3) if all wavelengths on all the buffers are occupied, deflect the packet to a secondary output port. The scoreboard within the optical router controller keeps track of the state of the optical router. The optical-label switching transmitters and receivers employ subcarrier multiplexing for the label and the data payload, and all- optical label extraction is achieved by fiber-Bragg grating and optical-circulators [4]. The label content will be detected by the burst mode receivers (BM-Rx) and induces the forwarding decision according to the routing algorithm. The label is 32 bits long, and assumes 100 Mb/s modulation to accommodate the clock speed of the FPGA, and the payload is modulated at 16 times 100 Mb/s (1.6 Gb/s) and is 640 bits long. The optical switch fabric included multi-section tunable wavelength diode lasers, semiconductor optical amplifiers for cross-gain modulation wavelength conversion, optical circulators, and a 8x8 uniform-loss cyclic frequency arrayed waveguide grating router (ULCF-AWGR). The packet routing experiment consisted of three scenarios. In all three scenarios, two packets, P_1 and P_2, almost simultaneously arrived at the input wavelength_1 of port_1, i.e., (1,1) in and the input wavelength_1 of port_2, i.e., (2,1) in of the OLSR with the same destination D to induce a packet contention condition at the default output port and wavelength (1,1) out . The first scenario consisted of the P_1 reaching (1,1) in slightly (60 nsec) after the P_2 reaching (2,1) in . Fig 2(a) illustrates the incoming packet measured at (1,1) in and