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Photonic Layer Systems: An Emerging Solution for Optical Connectivity in a Multivendor, Multi-Service EnvironmentFlexible, low-cost “drop-in” capability brings rapid provisioning of high-growth, high-margin triple-play services.
By Chris Egner, VP of Business Development and Sales and Marc Verreault, Director of Sales Engineering
BTI Photonic Systems
As service providers move into position to compete in the high-growth triple-play services market, they face a number of challenges in evolving the transport portion of their networks to take advantage of new revenue-generating opportunities and sharpen their competitive edge.
Network convergence, combined with the growing commoditization of optical components, sub-systems, and other connectivity equipment, and the advent of pluggable optics means service providers now have a much richer palette of options and vendors from which to choose. No longer are providers locked into single-vendor proprietary solutions; networks are now becoming a patchwork of functionality and gear from those players that operators deem best-in-class in each particular product area. A key challenge for operators lies in connecting this myriad of functionality and multi-vendor gear – routers, WDM equipment, SONET/SDH products, optical components and sub-systems – while at the same time meeting operators’ business imperatives and changing customer needs.
One high-priority business objective, for instance, is to minimize capital investment and re-engineering costs, as well as leverage existing network assets.
At the same time, operators need to keep an eye on continually driving a low-cost infrastructure, while ensuring that their multi-service networks have the necessary flexibility and versatility to accommodate future network and service growth. This is particularly important given the unpredictable growth and demographic patterns of new services.
Current connectivity solutions, however, are rife with tradeoffs. For instance, providers can decide to operate completely independent, parallel networks, but this is an approach that is costly and, increasingly, prohibitive. An alternate approach is to aggregate the traffic from the various transport equipment and send it to WDM gear at either end of the optical link. Again, such an approach would require significant capital outlay.
However, a new category of transport architecture – photonic layer systems – is emerging and gaining market acceptance as an ideal solution to achieve low-cost transport in a multivendor environment and carry multiple service types across metropolitan, regional, and even access networks.
Photonic layer systems: reduced complexity, improved flexibility
A photonic layer system is a standalone all-optical platform that is independent of the terminal, or services equipment, and interfaces directly with the WDM interfaces of service platforms. These photonic systems, integrate into a single product, all the key transport functionality – including amplification, dispersion compensation, performance monitoring, multiplexing, signal conditioning, wavelength “color” management, and optical add/drop capability – required to cost-effectively connect sites within converged multi-service optical networks.
Important for service providers, photonic layer systems are able to be seamlessly overlaid on existing networks without causing disruption to existing network services, allowing gradual migration to new services in line with customer demand. Of equal importance, photonic layer systems are less costly, by orders of magnitude, than other connectivity solutions, and pave the way for significantly more functionality and flexibility.
For example, SONET platforms, which remain a dominant transport architecture today, have evolved into multi-service provisioning platforms, supporting a wide range of services and protocols, including Ethernet and storage protocols (ESCON, Fiber Channel), along with traditional TDM.
However, SONET platforms have limitations: SONET is restricted by its line rate, typically no more than 10 Gigabits per second. This limits bandwidth scalability, which is critical for service providers to maximize future service revenue for higher bandwidth services, such as with the already commonplace Gigabit Ethernet and the growing 10 Gigabit Ethernet services. As well, SONET systems require expensive upgrades or replacement when limits on line rates are reached. Moreover, where a legacy network is not in place, SONET remains a costly alternative for new network deployments.
Another appealing alternative lies in metropolitan and regional WDM transport solutions, long touted as an answer for optical network connectivity. The transparency of WDM systems does allow for support of any optical service, and transitioning from an existing network infrastructure is as simple as a network overlay. At the same time, however, traditional WDM transport systems were designed for an entirely different network architecture, and are expensive and complex to deploy. As a result, WDM systems today have not been widely deployed in metro networks.
These and other options exist today, but each one on its own does not deliver an end-to-end, low-cost, transparent, and scalable solution. Photonic layer systems bring significantly new benefits, and allow providers to optimize their transport infrastructure across regional distances right through to the metro area. And because these systems are based on WDM, the ability to support any optical service and the ease of transitioning from existing network infrastructures is maintained.
Independence brings greater link control, and rapid, simple service deployment
Just as significantly, a photonic layer system that is independent enables intelligence to be decoupled from the services, or terminal equipment, and moves away from any prior dependency on both the terminal link and on specific vendors’ products.
In legacy optical transport systems, this management and control intelligence resides in the services equipment, and the optical link simply transports signals from one end to the other. As a result, there is no ability to gather an inventory of all components on the optical link. And while in recent years some intelligence has been added to various discrete components, that intelligence has been confined to the component level, provides only incremental improvement over previous generations of optical components and modules, and delivers little benefit from an end-to-end link perspective.
An independent photonic layer, by contrast, provides the important management and control plane that was unavailable in previous optical links. Through a photonic layer-specific graphical user interface, providers can now query the link to determine what components – no matter the vendor type – are deployed on that link. Providers gain visibility into and can make modifications to performance parameters of individual components – parameters such as amplifier settings, gain levels, and others. This information is essential in a multi-vendor product environment, where providers need the ability to directly manage the link so they can change component and network parameters, optimize the link as required, and ensure top service performance for their customers.
 With direct control over all equipment in the link, providers gain the ability to “plug-in” any services equipment, from any vendor, at any point on the photonic layer. The photonic layer is then able to adapt to this addition, and service can be turned up quickly and easily, eliminating the need to conduct an often time-consuming integration effort.
There is also a reduced need to engineer the entire transport network up front and calculate, for example, the exact signal, distance, and equipment requirements in advance – a particularly difficult task in the face of the unpredictable nature of today’s emerging broadband multimedia service requirements. Providers no longer need to make advance bets on which service equipment will ultimately be required or which equipment vendors they will choose, enabling them to incorporate new technology and capabilities as they become available and are required.
Along with this “drop-in” service capability, photonic layer systems are being designed to offer both coarse WDM (CWDM) and dense WDM (DWDM), giving service providers the choice of selecting the optimal solution for both cost and scale.
In fact, growing the wavelength count is much more cost-effective with photonic layer systems than with legacy proprietary systems. Proprietary systems tend to require wavelength-dependent transponders that are assigned to convert individual signals between the electrical and optical domains; deploying two wavelengths, then, would double the cost of deploying the first. In photonic layer systems, which leverage the flexibility of pluggable optics, the need for signal conversion functionality is eliminated, yielding a cost savings of as much as 75% compared to traditional WDM links.
Conclusion
The ability of a photonic network to expand, extend, and adapt to new network technologies, new services, and multiple vendor equipment makes it a financially sound decision for service providers and offers them unprecedented flexibility and simplicity to rapidly respond to customer requirements, evolve efficiently to converged broadband networks, and offer the full suite of services with minimal cost.
Chris Egner is VP of Business Development and Sales at BTI Photonic Systems ([email protected]). Marc Verreault is Director of Sales Engineering at BTI Photonic SystemsInc. ([email protected]) .
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