Light trails: a sub-wavelength solution for optical networking

Abstract

All-optical networks are able to transport data from source to destination entirely in the optical domain. This is a departure from current optical networks that rely on optical-electrical-optical (OEO) conversion at each intermediate connection node to route data properly. The opacity inherent in traditional networks is costly in terms of limiting bandwidth and increasing switching complexity. MPLS, OBS and OPS have been proposed as solutions for realizing an all-optical network. MPLS and OBS have the advantages of creating all-optical connections between nodes, but do not allow intermediate nodes to use the wavelength as well. Additionally, optical switches are constantly being reconfigured to accommodate new connections. OPS can make switching decisions in the optical domain, but the technology is immature. Light trail technology tries to avoid the pitfalls of immature technology, the inability of intermediate nodes to use a connection wavelength, and the constant reconfiguration of switches. A light trail is a unidirectional optical bus between nodes that allows intermediate nodes to access the bus. The goal is to minimize the amount of active switching that needs to be done by allowing intermediate nodes to use a connection that has already been setup. Connections are not constantly being setup and torn down, but rather exist for as long as they are being used by any of the nodes along their light trail.

Dynamic light trail routing in WDM optical networks

“…Each node can transmit data to any downstream node as long as it finds the optical bus is free. Frederick et al [8] and Gumaste and Chlamtac [11] both presented collision avoidance and re-transmission schemes using light trail technology. -Third, a light trail can be dimensioned (expanded or contracted) to meet certain applications.…”

“…Each node on a light trail supports the drop and continue function [8,11]. Instead of dropping the whole optical signal at an intermediate node, the node only needs to tap a sufficient amount of optical power from the signal for local processing.…”

“…The node architecture of a light trail network [8,11] is shown in Fig. 1 [11] proposed a protocol to establish and dimension light trails.…”

“…1 [11] proposed a protocol to establish and dimension light trails. Schemes for ensuring conflict free communication between opened optical paths within a light trail were provided in [8,11]. Compared with other schemes based on the traditional lightpath routing, e.g.…”

“…A new technology termed light trail was proposed in [11] to avoid the inability of intermediate nodes to use a connection wavelength, and the constant reconfiguration of switches. The authors in [8] proposed a scheme to avoid the collision occurring between different connections along a light trail. An important issue of light trail routing is to construct light trails to carry traffic in WDM networks.…”