5-Tbit/s frame-based ATM switching system using 2.5-Gbit/s×8 optical WDM links

The hardware architecture of a 5-Tbit/s FB (frame-based) ATM switching system OPTIMA-2 (OPTically Interconnected Distributed Multi-stage Tbit/s-ATM switching Network Architecture-2) is described. OPTIMA-2 has a non-blocking 3-stage switch architecture employing optical WDM links and dynamic bandwidth sharing. The WDM links are composed of a sender port, wavelength arrayed waveguided grating (AWG) router and receiver port. The sender port at the output port of a switch-element allocates a packet to one of eight WDM wavelengths and transmits it. The receiver port receives packets of all eight wavelengths via the wavelength AWG router and merges them at an input port of the next-stage switch-element. Total bandwidth is limited to 10 Gbit/s, but the maximum bandwidth of each wavelength is designed to be 2.5 Gbit/s to prevent the statistical multiplexing gain from falling. A scheduler, which selects variable-length packets from the eight wavelengths, can keep fairness and a small delay. The bandwidth of each wavelength is changed dynamically by the system so that the traffic in each wavelength is equally distributed among the total bandwidth. In OPTIMA-2, variable-length FB-ATM cell, which is familiar with the IP packet, can be switched while keeping the throughput fairness