Design Principles for Multi-Hop Wavelength and Time Division Multiplexed Optical Passive Star Networks

Abstract

Wavelength Division Multiplexing (WDM) has been shown to be one of the most promising ways to exploit the enormous bandwidth of a single mode optical fiber. Networks employing WDM are commonly based on optical passive star couplers. The major cost and limitations of such networks lie in the interface (both transmitters and receivers) providing optical-electronic conversion between stations and communication media. Based on current technology, interfaces based on fast tunable devices are still in the infant stage of development at this time. Commercially available fixed wavelength devices are much cheaper and reliable. With fixed wavelength device in each station, several stations may transmit and receive on the same wavelength. Time-Division Multiplexing (TDM) is often employed for those stations accessing the same wavelength. The resulting networks, called multi-hop Wavelength- and Time-Division Multiplexed (WTDM) Networks, may require a multi-hop path to deliver packets between two stations. In this paper we study multi-hop WTDM networks where each station has only one fixed wavelength transmitter and one fixed wavelength receiver. We propose a graph model, called a Receiving Graph Model, to represent these networks such that their inherent properties can be easily understood and alternative designs can be compared. Furthermore, we discuss several design principles and theoretical performance limitations of such networks.