Shared Protection Rings Research Articles

Transparent optical protection ring architectures and applications

This paper reviews recent progress in optical protection rings with the focus on transparent optical protection rings. Different optical protection ring architectures, such as dedicated and shared protection rings, in both the optical-channel (OCh) layer and the optical multiplex section (OMS) layer, are described. In particular, OCh shared protection rings (OChSPRINGs) are discussed in detail including node-architecture designs, ring protocols, triggers, and messaging channels. Feasibility studies and experimental results from Corning Inc. and other companies are reviewed. The paper also discusses how protection-switching times scale with number of nodes and number of wavelengths, and shows examples of applications using the scaling rules for practical optical networks such as metro, regional, and long-haul ring networks. The cost benefits of transparent optical protection rings are analyzed using a typical metro network. Finally, the paper discusses remaining issues and future developments in the optical protection ring area.

Calculating the optimal optical ultra-long haul network

Today's new generation of undersea cable systems extensively uses optical amplifiers, which allows the systems to be implemented over transoceanic distances. Optical amplifiers offer significantly increased transmission capacity, networking functionality and operational flexibility - all potentially at lower cost than traditional regeneration systems. Thus, similar techniques are now being used in terrestrial networks to exploit the wide bandwidth of optical fibers for long-distance transmission (thousand of miles) since the frequency range is in THz. A network optimization design methodology for ultra-long-haul terrestrial networks is presented and a variety of network architectures analyzed: optical networks with a 1:N path restoration mechanism; optical networks with express routes and a 1:N path restoration; line shared protection ring (LSPR) networks. This methodology is applied to an example network using several traffic scenarios. The optimal network architecture depends on the network itself and on the criteria determining the network design.

Transparent Two-Fiber Optical Channel Shared Protection Ring

A two-fiber optical channel shared protection ring including node architecture, signaling protocol, control hardware, and software is designed and implemented experimentally. For a ring with four nodes and two wavelengths, a total protection switching time of 6.8 ms is demonstrated along with a revert-to-working switching time of 1.6 ms. Experimental results show that the switching time scales linearly with number of nodes and number of wavelengths. The system can protect a ring with 16 nodes, 1200 km circumference, and 40 wavelengths in less than 50 ms.

Planning of WDM ring networks.

The rapid introduction of wavelength division multiplexing (WDM) technology to cope with the increased bandwidth requirements of transmission networks has intensified the need for recovery mechanisms at the optical layer. A first step towards survivable optical networking will be seen through the introduction of optical rings. This paper presents different types of optical rings (dedicated and shared protection WDM rings) and the planning issues associated with these WDM rings. In particular, we give mathematical models as well as solution methods for the ring loading and wavelength assignment problem. We compare the wavelength requirement of dedicated and shared protection rings under scenarios with different demand patterns. We also discuss the influence of the WDM equipment cost, and present a mathematical model for the optimization of hybrid networks with both dedicated and shared protection rings.

Fiber network survivability

At the transport layer in interoffice and interexchange networks, shared protection rings (SPRINGS) interconnected at matched nodes can provide 100% restoration in milliseconds after cable cuts and central office failures. The author introduces the SPRING and explains how its capacity advantage over other ring configurations enables it to be the most economical solution in more applications. Transport restoration technologies-1+1 diversity, digital crossconnect systems, and SPRINGS-in interoffice and interexchange environments are compared. A representative network study is presented to justify the choice of SPRINGs and matched nodes for the target architecture. Recommendations on how to evolve today's asynchronous networks in preparation for a fully survivable SONET ring-based network are also provided. Generic ring planning guidelines and network examples are presented to demonstrate how today's networks can be evolved to provide end-to-end survivable SONET transport. An approach to ring-based network design that simplifies the planning process and minimizes network cost is provided.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>