Photonic Layer Systems – A New Transport Architecture for Converged Networks

Service providers across North America face the challenge of migrating their networks to new low-cost infrastructure that delivers the full set of triple-play services to their customers. At the same time, economic realities are driving the need to extend the life of existing network investments. As a result, there is a need to re-evaluate existing network architectures, and specifically, a need for a new optimized transport layer.

The full suite of voice, video, data and -- increasingly-- storage services are required to compete in today’s market. Packet-based service platforms such as metro Ethernet routers are now emerging to offer all service types on a single low-cost platform. But to maintain these economic benefits and ensure flexibility for future network growth, a new transport architecture is required.

In addition to economics, another concern is how to transition to this new architecture while leveraging existing network assets. A transport solution must be multivendor to integrate with existing service platforms, and able to seamlessly overlay on the existing network without disruption of existing network services, allowing gradual migration as customer service demand dictates.

As service providers wrestle with identifying the ideal transport architecture, one obvious question is: Why not SONET? Despite its long-predicted demise, SONET is still a dominant transport architecture today. SONET platforms have evolved into multiservice provisioning platforms, and can offer a wide range of service solutions including Ethernet and storage protocols (ESCON, Fiber Channel) in addition to traditional TDM.

But SONET/MSPP platforms have limitations. SONET is restricted by its line rate, typically 2.5gbps or 10gbps. Also, legacy SONET ADMs, and even new MSPPs, have a limited set of service interfaces. Bandwidth scalability is critical for service providers to maximize future service revenue (for example, gigabit Ethernet is already common, and deployment of 10 gigabit Ethernet is increasing). SONET systems require expensive upgrades or replacement when limits on line rates are reached and are typically limited to no more than 10gbps. In addition, where a legacy network is not already in place, SONET remains an expensive alternative for new network deployments.

Metro and regional WDM transport solutions, long touted as the answer for optical networks connectivity, are an appealing alternative as a transport architecture. The transparency of WDM systems allows for support of any optical service. And transitioning from an existing network infrastructure is as simple as a network overlay.

But especially for metro and even regional networks, legacy WDM transport systems are often expensive and complex to deploy. Traditional WDM systems were designed for a different network architecture. As a result, WDM systems today have not been widely deployed in metro networks.

Today’s new service platforms typically deploy pluggable optics that directly generate colored or WDM-ready interfaces. Legacy WDM systems are generally designed to include electrical transponders. In the past, transponders were required for flexibility, but this is no longer a consideration with the general availability of WDM-ready interfaces. There is a need for a streamlined transport solution that interfaces directly at the WDM layer to service platforms.

A new transport architecture has emerged to address this need – Photonic layer systems. Photonic layer systems interface directly into the colored interfaces of service platforms. The elimination of unnecessary functionality, such as electrical conversion and grooming, results in dramatic cost savings of up to 75 percent or more over traditional WDM systems.

But photonic layer systems are based on WDM, so the benefits of supporting any optical service, and ease of transitioning from an existing network infrastructure are maintained. Photonic layer systems do however offer a distinct advantage with their multitechnology, multivendor (interfacing at the photonic layer) and multiservice capability.

The efficiency of photonic layer systems as a transport architecture is extended with the addition of key functionality that has typically been packaged separately. Amplification extends network reach – services can be rolled out at selected sites allowing service providers to reduce costs by deploying new network services only as demand dictates.

Photonic layer systems can offer both CWDM and DWDM solutions allowing service providers the choice of selecting the optimal solutions for both cost and scale.

In addition to the cost benefits of a streamlined architecture, space and power requirements are also significantly reduced. Photonic layer systems are typically much smaller (1RU or 2RU in height), compared with traditional WDM- and SONET-based systems that can be 15RU or more.

And, finally, photonic layer systems are future-proof. WDM scalability means services can be scaled to 10gbps and beyond with WDM transparency allowing for support of any future optical service.

For service providers planning to migrate their networks to a low-cost infrastructure that can offer the full suite of services, photonic layer systems offer a promising new alternative for an optimized transport layer. Multiservice, multivendor and economical, photonic layer systems are rapidly gaining acceptance amongst service providers throughout North America and Asia.

David Teed is vice president of product marketing at BTI Photonic Systems. Robin Andrew is a strategic marketing consultant at BTI Photonic Systems.

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