Demonstration of Contention Resolution for Labeled Packets at 40 Gb/s Using Autonomous Optical Buffers John P. Mack, Henrik N. Poulsen, Emily F. Burmeister, Biljana Stamenic, Geza Kurczveil, John E. Bowers, and Daniel J. Blumenthal Electrical and Computer Engineering Department, University of California, Santa Barbara jmack@ece.ucsb.edu Abstract: Contention resolution of labeled optical packets is demonstrated utilizing two packaged optical buffers. Forwarding and buffering decisions are autonomously determined for 40 Gb/s payloads from 10 Gb/s labels with greater than 99.9% packet recovery demonstrated. ©2009 Optical Society of America OCIS codes: (060.1810) Buffers, couplers, routers, switches, and multiplexers; (230.4480) Optical amplifiers 1. Introduction Optical packet switching provides a means of communication that is high bit rate, transparent, and scalable [1]. In label switched optical packet switching, forwarding information and data are separated into lower bit rate headers and high bit rate payloads [2]. This allows for the use of low frequency electronics for processing headers and payload envelope information while transparently forwarding high bit-rate payloads optically at low switching speeds. The use of low speed electronics and the further integration of photonic devices could reduce power and footprint concerns of scaling high bit rate data routers. Optical packet switches must operate asynchronously and autonomously making optical buffering a necessary functionality for contention resolution to avoid temporal collisions of packets simultaneously destined for the same output port [3, 4]. A flexible and scalable buffer has been proposed and buffering has been demonstrated for 10 Gb/s payloads using commercially available semiconductor optical amplifiers (SOAs) [5]. Buffering of 40 Gb/s payloads has been shown previously utilizing an integrated 2x2 InP switch matrix with fiber delay lines [6]. Two-port contention resolution of 40 Gb/s payloads has been shown with multiple photonic chip optical buffers that consist of an integrated InP switch matrix coupled to a silica-on-silicon waveguide delay line [7]. Destination information was pre-determined for buffering decisions in the referenced experiments. However, optical packet switches require real-time lookup of headers to determine how and where to forward packets. We demonstrate for the first time, optical packet buffering utilizing packaged compact InP switches with fiber delay lines that erase 10 Gb/s headers and re-circulate 40 Gb/s payloads for contention resolution. Buffering and forwarding decisions are made autonomously based on output destinations extracted from lower bit rate headers and envelopes of high bit rate payloads. 2. Principle of Operation The basis of optical buffering and electronic lookup for a 2x2 optical data router is shown in Fig. 1. Input optical packets consist of 10 Gb/s headers, 40 Gb/s payloads, and guard bands. The optical headers contain a label field that indicates the output port. The packet stream is optically tapped and the data enters a clock/data recovery circuit (CDR) and payload envelope detector (PED). Recovered headers and envelopes are sent to an electronic channel processor (ECP) to determine the output port destination of the payloads based on the optical label and to provide a precise time reference for the payloads. The ECPs then forward the recovered payload envelopes as output port requests to a central arbiter for electronic lookup. The arbiter uses a lookup table to determine contention and buffer control by comparing port requests and buffer queue signals. Based on the lookup table, the arbiter generates buffer SOA control signals which pass a packet through, load a packet into the buffer, re-circulate a packet in the buffer, or unload a packet from the buffer. The SOA control signals are then sent to the corresponding ECPs which forward the gating signals to the buffers. The buffers consist of packaged 2x2 InP switches driven by current DACs and RF opamp circuits. The fiber delay line includes an attenuator, band pass filter and polarization controller as shown in Fig. 2. The buffers erase labels by turning SOAs off before the payloads and gating the payloads for buffering. Thereby contention resolution through the use of optical buffering is demonstrated autonomously by using label and payload envelope information along with buffer queue signals. Payloads would then be forwarded via wavelength conversion and a new header written. a1366_1.pdf OMU2.pdf © 2009 OSA/OFC/NFOEC 2009 OMU2.pdf 978-1-55752-865-0/09/$25.00 ©2009 IEEE