A New Optical TDM Ring Architecture

Abstract

Abstract-In this paper, we explore new optical time-division multiplexing (OTDM) ring architectures. The objective of our study is to achieve high space-reuse efficiency of each time slot without using time-slot interchanges, which are expensive and difficult to implement in the optical domain. Although a TDM slot is often compared to a wavelength channel in a wavelength-division multiplexing (WDM) network, we show that the intrinsic propagation delay in an OTDM network will lead to a phenomenon, called a slot cycle in the paper, that has no counterpart in WDM networks. By exploring the concept and the algebraic relationship between the frame size and the total propagation delay of the ring, we discover a novel OTDM ring architecture that achieves a high space-reuse efficiency without using time-slot interchanges. The equivalent of this architecture in the WDM domain can only be achieved with the use of many wavelength converters. We also study the efficiency of the architecture based on different types of traffic demand models in the network.Index Terms-Optical ring architecture, optical time-division multiplexing (TDM).

On the space reuse efficiency of TSI-free OTDM rings

“…2 ), significantly reducing complexity and cost. A fundamental result we discovered in [1] is that in every TSI-free OTDM ring, all slots form equal-length cycles and the slot cycle length will affect the efficiency of the ring. Consider a unidirectional ring with N nodes indexed from 0 to (N −1) in the clockwise direction, such that data flows from node i to node ((i+1) mod N ) on the ring.…”

“…We discovered in [1] that any traced slot will eventually return to the original slot and form a cycle. We called this a slot cycle [1].…”

“…We discovered in [1] that any traced slot will eventually return to the original slot and form a cycle. We called this a slot cycle [1]. Furthermore, all slots in a TSI- Another important result of [1] is that the length of the slot cycle has a strong bearing on the space re-use efficiency of each slot of the ring.…”

“…We called this a slot cycle [1]. Furthermore, all slots in a TSI- Another important result of [1] is that the length of the slot cycle has a strong bearing on the space re-use efficiency of each slot of the ring. An intuitive explanation of the problem is given in Fig.…”

“…An efficient optical buffer technology for optical TSI is not currently available. Our previous work [1] has shown that without TSIs, all slots in an OTDM rings will form equal-length cycles. In this letter, we derive a general formula that shows the relationship between the cycle length and the space reuse efficiency of a TSI-free OTDM bi-directional ring.…”