11-hop Operation of Optical-label Switching System with All-optical Label Swapping

This paper discusses multi-hop operation of an optical-label switching system, demonstrating rapid alloptical packet switching with 2R regeneration for the data and optical label swapping for the label. Introduction Optical-label switching technology has the potential to provide low latency and transparency desired for the next generation Internet [1-2]. For network applications, the router must be cascadable. Moreover, data and label regeneration with label swapping capabilities are desired. Recent demonstrations have been limited to single-hop operations with label swapping [3], multi-hop operations without label or data regeneration [4]. This paper discusses an experimental demonstration of multi-hop (up to 11-hop) operation, in an optical packet routing system with 2R regeneration and optical-label swapping. Experiment Descriptions Using one optical-label switching router (OLSR) setup, the experiment emulates the multi-hop operation of many routers by sending the output packets of one linecard back to the input of the second linecard to form a loop. Fig. 1 shows the setup. The OLSR consists of an optical-subcarrier multiplexing transmitter (SCM TX), two label extractors (LE), two burst mode receivers (BMRX) for label detection, a switch controller that implements the forwarding table and switching control, two tunable wavelength converters (TWC) consisting of tunable lasers (TLD) and semiconductor optical amplifiers (SOA), a uniform-loss cyclic-frequency arrayed waveguide grating router (AWGR), and a fixed wavelength converter and label rewriting module (FWC & LR) [5]. The Parallel Bit Error Rate Tester (ParBERT) synchronously generates the electrical label at 155Mb/s and payload at 2.5Gb/s. The SCM TX mixes the label with a 14GHz tone, combines it with the payload, and modulates the optical carrier with the combined signal. Hence, the modulator output is a double-sideband optical signal with the payload as the baseband and the label as the subcarrier. The combination of a fiber Bragg grating (FBG) and an optical circulator (OC) achieves alloptical label extraction [6]. The BMRX asynchronously recovers the label contents from optical domain to electrical domain. The recovered label signal induces the forwarding decision inside the switch controller according to the routing algorithm. Based on the decision, the switch controller sends a control signal to the TLD to tune to the designated wavelength [7]. The TLD generates the probe light for SOA, which converts the payload information onto the new wavelength by cross-gain modulation (XGM). Payloads with different labels are converted onto different wavelengths corresponding to the desired output ports of the AWGR.