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

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 ber. 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. According to current technology, an interface based on fast tunable wavelength devices is still in an infant stage of development. On the contrary, xed wavelength devices are much cheaper and already commercially available. When xed wavelength devices are used, to reduce the number of transmitters and receivers in each station several stations may transmit and receive on the same wavelength. Therefore, Time-Division Multiplexing (TDM) is employed for those stations accessing the same wavelength. The resulting networks may require taking a multi-hop path to deliver packets from one station to another (i.e., multi-hop WTDM networks). In this paper we study multi-hop WTDM networks when each station has only one xed wavelength transmitter and one xed wavelength receiver. We propose a graph model called the Receiving Graph model to represent these networks such that their inherent properties can be easily understood and alternative designs can be compared. Furthermore, based on this model we discussed several design principles for such networks and some theoretical performance limitations are presented.