Error-free multihop cascaded operation of optical label switching routers with all-optical label swapping
OFC 2003 Optical Fiber Communications Conference, 2003.
This paper discusses multi-hop routing, all-optical label swapping operation of optical label switching routers that make real-time decisions based on the label and the forwarding table. The switching fabric conducts data regeneration and label rewriting. 2003 Optical Society of America OCIS codes: 060.4510 Optical communications, 060.4250 Networks Introduction Optical-label switching technology has made key progress in providing the low-latency and transparent switching desired for the next
... ired for the next generation Internet   . For practical network applications, the optical routing system must be cascadable. Recent demonstrations have been limited to single-hop operations with label swapping , multi-hop operations without label or data regeneration  . High-performance optical-label switching routers are expected to include data and label regeneration with label swapping capabilities. This paper discusses an experimental demonstration of a cascaded multi-hop optical packet routing system with optical-label swapping. The system includes tunable lasers, wavelength converters, arrayed waveguide grating routers, burst mode receivers, a switch controller with a forwarding table, and an all-optical label-swapping module. Experiments The experiment emulates a network with multiple optical-label switching routers, each providing label-based packet forwarding . Fig 1(a) shows an emulated optical-label switching network consisting of several optical-label switching routers (OLSR). Three types of packets, P1, P2, and P3 with labels L1, L2, and L3 respectively, ingress into the optical label switching networks. The first OLS router (OLSR1) performs the optical-label based forwarding of all three packets. OLSR1 forwards P3 north to a neighboring OLS router (OLSR2) and forwards P1 and P2 east to another neighboring OLS router (OLSR3). The OLSR3 in turn forwards P1 and P2 to two different output ports. For multi-hop scalable OLSR operations, data payload regeneration and label swapping/regeneration are beneficial. Fig 1(b) shows the detailed structure of OLSR and setup for this network emulation. As Fig 1(b) shows, the actual experiment places OLSR1 and OLSR3 on the same optical router system with multiple line cards and replaces OLSR2 with a drop port. The OLSR system consists of an optical-subcarrier multiplexing transmitter (SCM Tx), two optical label/data separators, two burst mode receivers (BMRx1 and BMRx2) for label detection, a field programmable gate array (FPGA) that implements the forwarding table and switching control, two tunable wavelength converters consisting of tunable lasers and semiconductor optical amplifiers (SOAs), a uniform-losscyclic frequency (ULCF) arrayed waveguide grating router (AWGR), a label rewriting module  and data receivers. The Parallel Bit Error Rate Tester/Pattern generator (ParBERT) synchronously generates the electrical label and payload signals. The LiNbO 3 external modulator modulates the continuous wave (CW) light from the distributed feedback laser diode (DFB LD) using a subcarrier multiplexed signal consisting of a baseband 2.5 Gb/s data payload and a 155 Mb/s label modulated onto a 14 GHz subcarrier. Hence, the modulated signal includes a double-sideband subcarrier label 14 GHz away from the center optical carrier frequency. The combination of a fiber Bragg grating and an optical circulator achieves all-optical label extraction  . 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 in the FPGA. Based on the forwarding decision, the switch controller sends a control signal to the tunable laser (TLD) to switch to the designated wavelength  . The TLD generates a tunable probe light for the SOA1, which modulates the payload signals onto the new wavelength by cross-gain modulation. Payloads with different labels are converted onto different wavelengths corresponding to the desired output ports of the AWGR.