Wavelength-division-multiplexed ring networks

Abstract

Multichannel local-area networks can be constructed using fiber-optic wavelength-division-multiplexing (WDM) techniques. In this paper, WDM is applied to ring networks such as FDDI, token ring, slotted ring, and buffer insertion ring architectures. Crosstalk and insertion loss analyses of grating demultiplexers shows that the ratio of channel separation to channel width must be greater than four. Performance analyses of the multichannel WDM ring are formulated to determine the packet delay. The delay in the multichannel token ring is obtained by summing the remaining service time, token walk time, and the average service time of newly arrived messages. The remaining service time is estimated by approximating the system as a M/M/m queue. The multichannel slotted ring and buffer insertion ring are modeled by a non-preemptive head-of-the-line priority queuing system. By identifying that portion of the passing ring traffic having priority over local traffic, the delay of a tagged packet can be obtained as the sum of the residual service time and service times of local waiting packets and newly arrived ring packets. Two implementations are identified, one with parallel optical transmitters and receivers and protocol modules, and another using an array of laser diodes and photodetectors and a single protocol module.