IEEE PHOTONICS TECHNOLOGY, VOL. 14, NO. 8, AUGUST 2002 1211 Rapidly Switching All-Optical Packet Routing System With Optical-Label Swapping Incorporating Tunable Wavelength Conversion and a Uniform-Loss Cyclic Frequency AWGR S. J. B. Yoo, Hyuek Jae Lee, Zhong Pan, Jing Cao, Yanda Zhang, Katsunari Okamoto, and Shin Kamei Abstract—This letter discusses an experimental demonstration of a rapidly switching all-optical packet routing system with optical-label switching and all-optical label-swapping capabilities. The optical routing system optically extracts the subcarrier optical-label content, compares it against the forwarding table, makes packet forwarding and label-swapping decisions, and forward the packet to the desired output with a newly updated subcarrier optical label. The packet switching fabric included a combination of rapidly tunable wavelength conversion and a uniform-loss cyclic frequency 8 8 arrayed waveguide grating router. The packet routing system achieved 600-ps switching time and 250-ns forwarding decision time. Accumulated packet bit-error-rate measurements confirm the successful error-free packet routing with all-optical label-swapping. Index Terms—Arrayed waveguide grating, multiprotocol label switching (MPLS), optical-label switching, optical-packet switching, subcarrier multiplexing (SCM), wavelength conversion. I. INTRODUCTION W HILE THE convergence of data networking with multi- wavelength optical networking is a natural consequence driven by imminent needs of the Internet, equally important are the low latency and the traffic engineering features associated with the networking technology. Multiprotocol-label switching (MPLS) [1] is a recent development from the data networking perspective, and it combines desirable Layer 2 and Layer 3 features of Internet protocol (IP) and asynchronous transfer mode (ATM). Nearly concurrently with MPLS, the new con- cept of optical-label switching (OLS) networks [2], [11], [3] and optical-label swapping [4]–[6] emerged from the optical networking perspective. This letter discusses an experimental demonstration of an optical-packet routing system with 600-ps switching time capable of optical-label detection, optical-label swapping, and optical-packet forwarding incorporating an Manuscript received December 28, 2002; revised April 10, 2002. This work was supported in part by NewFocus, Inc., and UCCoRe under CoRe99-012, by the Defense Advanced Research Projects Agency and by Air Force Research Laboratory under the Agreement F30602-00-2-0543, and by the National Sci- ence Foundation under Grant ANI-998665. S. J. B. Yoo, H. J. Lee, Z. Pan, J. Cao, and Y. Zhang are with Optical Switching and Communications Systems Laboratory, Department of Electrical and Computer Engineering, University of California, Davis, CA 95616-5294 USA (e-mail: yoo@ece.ucdavis.edu). K. Okamoto is with NTT Electronics Corporation, 311-0122 Ibaraki Pref., Japan. S. Kamei is with NTT Photonics Laboratories, 319-1193 Ibaraki-Pref., Japan. Publisher Item Identifier S 1041-1135(02)06013-5. Fig. 1. A functional block diagram of the experimental system, which represents the core of an optical label switching (OLS) router. The experimental setup includes optical circulators (OC1 and OC2), fiber Bragg gratings (FBG1 and FBG2), erbium-doped fiber amplifier (EDFA1, EDFA2), LiNbO modulators (Mod1, Mod2), 14-GHz local oscillators (LO), a polarization controller (PC), and photodetectors (Payload detector and label detector). arrayed waveguide grating router (AWGR) and rapidly tun- able-wavelength conversion. II. EXPERIMENTS Fig. 1 shows a functional block diagram of the experi- mental system, which represents the core of an OLS router. It consists of an optical-subcarrier multiplexing transmitter, an optical-label/data separator, a label detector, a forwarding table, a switch controller, a tunable wavelength converter including a tunable laser and a semiconductor optical amplifier (SOA), a uniform-loss-cyclic frequency (ULCF) AWGR, label rewriters and receivers. The transmitter modulates the original label (label_1) at 622 Mb/s on a 14-GHz carrier frequency subcarrier multiplexed with the baseband data payload packet at 2.5 Gb/s. The modulated signal will then include double-sideband sub- carrier header appearing 14 GHz away from the center optical frequency of 192.7 THz (1549.3 nm). The optical-label/data separator consists of an optical circulator (OC1) and a fiber Bragg grating (FBG) with its peak reflectivity centered at the same optical frequency. The FBG has higher than 99.9% peak reflectivity with a pass band below 5-GHz half-width at half-maximum. Hence, the FBG nearly perfectly reflects the data payload appearing at the center lobe and almost completely transmits the subcarrier header appearing at the sidebands. The combination of the optical circulator and the FBG separates the input signal into the data payload and the subcarrier header. 1041-1135/02$17.00 © 2002 IEEE