Abstract

All-optical multihop networks are important in telecommunications and computer communications because of their bandwidth transparency. The combination of photonic switching and wavelength-division multiplexing (WDM) can expand the aggregate capacity and throughput. The actual capacity in terms of number of wavelengths and bit rate per wavelength that can be injected at an access port is a complex function of the physical implementation, topology, and protocol. We describe an analysis that shows all three of these should be considered when designing a multihop all-optical network. We illustrate that severe bandwidth limitations can occur if the network is not designed properly and that there is a strong interplay between the physical implementation and the physical layer protocols. A similar analysis has been carried out for point-to-point transmission systems,¹ where the number of wavelengths can be constrained to as few as ten for transcontinental distances. The difference in our analysis lies in the nature of multihop networks, where packets or messages traverse a statistical number of hops. The combination of the packet lifetime in the network with the network physical dimensions will place a statistical limit on the bandwidth. For a given protocol, this limit is defined by the small number of packets that spend the longest time in the network.

© 1994 Optical Society of America