Leo Nederlof

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.

The potential of optical layer networks

There is enormous potential in newly emerging optical layer networks that support a rapidly growing Internet backbone. This potential stems from the value of extended reach to remove costly regenerators, the value of configurability to reduce provisioning times between IP routers, and the value of optical peering to increase the efficiency of the EP backbone network.

Ultra-long-haul DWDM network studies with cost-effective reconfigurable OADMs

By use of novel technologies for broadcast and select (B&S) node architecture and a dispersion-managed fiber system, we demonstrate an ultra-long-haul (ULH) network system consisting of 13 optical add/drop multiplexers (OADM) in an optically transparent 4160-km network chain. All 80 channels at a bit rate of 10.7-Gbps, spaced with a 50-GHz wavelength grid, perform >13.6 dBQ, which offer a 2-dBQ optical margin when forward error correction is applied. A dynamic spectral equalizer with 40 dB extinction ratio is used for the B&S OADM, which offers simultaneous blocking and leveling functions for channel drop and power equalization. The cross-talk penalty requirement of an OADM in the ULH system is studied.

Metro network architecture scenarios, equipment requirements and implications for carriers

Metropolitan network traffic demands are used to project network topology and element characteristics assuming several different market penetrations for existing (ILEC) and new (CLEC) carriers.

Traffic Studies for Fast Optical Switching in an Intelligent Optical Network

The optical layer of the transport network is expected in the (near) future to make the transition from a statically configured layer to a fully flexible, automatic and intelligent layer. Such an intelligent optical network (ION) allows to set up (or tear down) bandwidth between two nodes on demand, following a simple request of the client network layer: the so-called switched connections. For successful deployment of these switched connections it is of utmost importance to have a well-educated idea about the granularities of the traffic flows in the optical transport network. Deploying switched connections with a capacity of 10 Gbps to transport a traffic demand with a granularity of a few hundred Mbps does not exactly make efficient use of the network resources. In this paper, the granularity of the traffic demand between US metro areas is investigated for two future points in time, namely 2006 and 2010. For this study we focus on the traffic flows between two metro area entities: the points of presence (PoPs) or the main aggregation points of the customer traffic in a metro area, and the collector central offices (COs) or the nodes a bit further in the metro area, closer to the end-customers. We have found that a significant portion of the total traffic volume at these moments in time will qualify for transport using switched connections with a capacity of 10 Gbps. According to our study, in 2006 around one third of the traffic will qualify for transportation in such 10 Gbps connections between PoPs in different metro areas, while by 2010 this amount will have increased to more than 99%. The traffic granularity between the collector COs, however, will in 2006 still be too small to justify the use of direct 10 Gbps connections, but in 2010 almost three quarter of the traffic could make use of 10 Gbps direct connections from collector CO to collector CO. These results enable us to sketch the expected network evolution scenario and determine the type and size of equipment needed in the different steps of the network evolution. The optical edge aggregation switches will have to be moved deeper into the metro area with time: in 2006 they will be needed at the PoPs, while by 2010 they could be placed at the collector COs.

Interconnection of metropolitan and backbone networks

As Internet traffic continues to grow, eventually dominating voice traffic, the network economics and traffic granularities may become favorable for merging the metropolitan core with the long-distance backbone network, to form an integrated 10 Gb/s wavelength-routed network architecture.

Value proposition for configurable optical network elements

The value of configurable optical network elements for the fast provisioning of wavelength services is assessed against manual provisioning. Results are presented that were obtained by evaluating the long haul wavelength circuit provisioning process.

USA metropolitan network value opportunities

System costs of SONET, next-generation SONET and WDM transparent ring with 2.5 and 10 Gb/s bit rates are compared for metro applications. WDM ring technology offers significant cost reduction compared to other approaches.

Value of agile transparent optical networks

We describe how and why agile transparent optical networks can lower the cost of building and maintaining a long haul network. We analyze the key value drivers of a transparent network and explore the implications for key optical components and modules.

Value analysis of Raman amplification in 40-Gbit/s optical networks usingdispersion-managed fiber

We present an analytical model for performance of a transmission system in which Raman amplification is employed. We perform a network value analysis on the basis of that model and show that use of Raman amplification in 40-Gbit/s dispersion-managed systems can realize a savings in capital expenditure of ~20% compared with erbium-doped fiber amplifiers for a full network build of a large U.S. carrier.