Agile optical networking reduces cost and complexity in WDM networks

By Steven D. Robinson, Meriton Networks -- Agile optical networking eliminates cost and complexity from existing carrier networks by creating a fully automated optical layer.

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Agile optical networking eliminates cost and complexity from existing carrier networks by creating a fully automated optical layer.

By Steven D. Robinson, Meriton Networks

With consumer broadband expected to surpass business use of bandwidth within the next four to seven years, the telecommunications industry is facing extraordinary change. In a recent report, industry analyst Tom Nolle predicts that "by 2010, consumers will outspend companies by almost 3:1 and will generate over 90% of the offered load of the public network in the US. In other parts of the world, consumers will make up virtually all of the market in both traffic and revenue."1

Today, the network load per household comprises applications connected to the computer, including Internet access, instant messaging, music and video downloads, and online gaming. Other activities, such as television and movie viewing, are handled independently and are not connected to the broadband IP network. Likewise, voice calls are handled by mobile or POTS systems and are not networked to the IP system. With this set-up, 1 Mbit/sec to 5 Mbits/sec per household generally has been adequate.

That was then. Now, as we enter the era of the "digital home," changes are underway. Households will require connections of 30 Mbits/sec to 50 Mbits/sec and beyond to support new networked services. Entertainment services such as IPTV, video-on-demand (VoD), and online gaming will add to the current network load, with each demanding 5- to 10-Mbits/sec bandwidth. Additionally, personal and mobile communications will be an extension of the IP network, adding even more to the overall network load.

In short, the emergence of the digital home requires a fundamental new approach to networking. However, because optical infrastructure decisions are long-term and because many uncertainties still exist regarding future service mixes, traffic patterns, and bandwidth needs, many operators understandably are hesitant to commit to network changes. But in this fast-moving environment, a wait-and-see approach simply won't work--and neither will the old standby method of simply adding more bandwidth.

Old business models under siege

The challenges facing today's service providers cannot be met by simply adding more bandwidth. Bandwidth prices are extremely sensitive to competition and have been falling every year since the beginning of the millennium. With operating expenditures (opex) making up the majority of costs, network operators must continue to increase bandwidth and aggressively decrease opex to maintain a positive return on investment (ROI).

For business models to succeed, network operators must shift the focus of their cost management plans from capital/bandwidth cost (capex) to opex cost reduction. Fortunately, new developments in WDM technologies are making that shift easier while providing future-proofing capabilities that enable network operators to meet the unpredictable and unforeseen requirements that the digital home will bring.

Agile optical networking

In this new digital home and opex-focused environment, what is required is an infrastructure capable of supporting higher value services while eliminating excess cost and complexity. A new optical layer has been defined that meets these needs: Agile optical networking.

The hallmarks of agile optical networking include the following:

• Rapid and simplified optical deployment, which is fundamental to reducing opex;

• Flexibility to provide a plethora of choices, including:

DWDM and/or CWDM;

Multiple services (e.g., SONET/SDH, Ethernet, etc.);

Multiple topologies (rings, mesh, or linear);

Unicast or multicast to support a broad range of multimedia formats;

• Scalability, making it easier to add capacity without affecting existing customers; and

• Future-proofing to ensure support for multiples services, even those still being defined.

The agile optical networking infrastructure fits as part of network operators' emerging next-generation network architectures, as illustrated in Figure 1. The agile optical layer provides all the transport and grooming requirements for service access networks and the IP/MPLS network layer, while also delivering some services directly to end-customers (e.g., high-speed Ethernet, SANs).

Figure 1: Converged next-generation network architecture

Many people associate agile optical networking with reconfigurability, and while this is true, agile optical networking actually includes much more than the ability to remotely provision/add/drop wavelengths across a network. In order to achieve the promise of reduced complexity and cost in optical networks, agile optical networking incorporates the following capabilities:

• Automated network lifecycle planning;

• Simplified deployment and operations;

• Network flexibility with reconfigurable optical add/drop multiplexing (ROADM) technology;

• Dynamic provisioning; and

• Programmable hardware.

Eliminating costs through automated network lifecycle planning

With agile optical networking, service providers can rely on sophisticated tools that fully automate the planning, design, and management of the entire optical layer in an end-to-end fashion. A full-featured planning tool guides the operator through all aspects of network planning, including node placement, equipment requirements, and traffic planning--everything the service provider needs to ensure that each wavelength will be packed to maximum capacity and the network will operate as efficiently as possible. Good network planning tools provide detailed reports that effectively can act as the order form for the network. This automation enables a single network operator to complete a network plan within minutes, without calling on a team of specialists.

Once the network is set up, planning tools continue to help the service provider with a variety of ongoing planning activities. Planning tools can facilitate re-engineering of the network as demand changes over time. In addition, they are invaluable for scenario planning--the "what-if?" scenarios that help a service provider prepare for changes in a dynamic environment. They can also be used for multi-year planning by helping to prepare the service provider for whatever the future holds.

Eliminating costs through simplified deployment and operations

Agile optical networking solutions simplify network deployments and operations in many ways. Keys to achieving simplification include a fully automated optical layer and a pre-configured optical backplane. Through the use of an optical backplane, installation is greatly simplified and the manual labor and cabling required to provision a new lightpath or a new service is reduced. The optical backplane eliminates all intra-system fiber jumper cables, vastly accelerating the time it takes to commission a node--not to mention eliminating manual errors.

Moreover, all power and gain balancing is done automatically, with no manual intervention. These systems automatically adjust the existing traffic and the added traffic power levels to ensure optimal transmission for each wavelength. Whereas it used to require highly trained engineers to deploy and operate an optical network, regular telecom staff now can do the job effectively.

Eliminating cost with ROADM technology

A ROADM remotely controls the adding and dropping of wavelengths without converting the pass-through optical signals to electrical signals. ROADMs support any-to-any port connectivity without reengineering, and they offer a level of flexibility at the optical layer similar to what is provided by SONET/SDH ADMs at the sub-wavelength level.

ROADMs lower opex and increase the network operator's ability to get services up and running quickly. They are ideal for today's network because they enable simple, fast service activation through a fully automated optical layer; flexible network configurations that can be adapted as requirements change; improved bandwidth efficiency by eliminating stranded or under-utilized bandwidth; and integrated SONET/SDH and WDM layers that simplify the network.

Thanks to a GMPLS control plane and flexible ROADM technology, agile optical networking enables the setup, provisioning, and management of a ROADM-based network with true point-and-click provisioning from a central location. Agile optical networking solutions can be installed in a day--a task that used to take two to three weeks for fixed OADMs. New cards can be installed in minutes instead of hours. Automated operations, administration, maintenance, and provisioning (OAM&P) reduce provisioning time, maximize network efficiency, increase service flexibility, and--above all--substantially reduce opex.

Eliminating costs through dynamic provisioning

By combining key technologies like flexible-port ROADMs and GMPLS control planes, provisioning new services can be done dynamically and remotely. For example, once a user initiates a request for a new service (a "point-and-click" operation), a message is sent to the gateway node signaling the request for the new lightpath/service. This message is forwarded to the headend node via an optical supervisory channel. Since each node knows the resources of all other nodes on the network, the headend node can choose the optimal wavelength and path. Resource reservation messages are sent to the relevant nodes to reserve the required resources along the path. Acknowledgements are returned to the headend node. The set up of add, pass-through, and drop wavelength states for each ROADM is then signaled to all relevant nodes. With a fully reconfigurable, flexible-port ROADM, lightpath setup can be accomplished without the carrier ever touching a fiber.

Agile optical networking solutions also offer the ability to select optical or SONET/SDH layer protection on a per-wavelength basis. These solutions offer multiple optical layer and SONET/SDH layer protection switching options, on the same two-fiber physical ring. All protection options are selectable on a per-wavelength basis, and multiple protection options can be implemented in a single ring/system.

Eliminating complexity through programmable hardware

Next-generation optical modules reduce costs by reducing network complexity. Programmable cards with pluggable optics allow the service provider to use a single line card to support multiple clients or wavelengths. The most effective cards will provide:

• Multiple SFP- and XFP-based lasers/receivers that are hot pluggable for pay-as-you- grow and reach adaptability;

• Integrated CWDM/DWDM filters;

• Tunable lasers across the full wavelength band;

• Integrated protection switching;

• Integrated loop-back support;

• Integrated bridge-and-roll support; and

• Integrated optical and protocol-level performance monitoring.

By deploying ADM-on-a-wavelength transponders, service providers can take advantage of standards-compliant ADM functionality, which dramatically reduces the number of network elements at each site, thereby eliminating the "rack and stack" requirement of SONET rings. Standard ADM functionality also provides effective utilization of every wavelength with per-wavelength, VC3/STS-1-level grooming and allows the service provider to add/drop or bypass any ADM wavelength at any node.


The evidence is clear: Service providers must lower opex to ensure ongoing profitability while upgrading their network infrastructures to handle the requirements of the digital home. Just as there are many factors that contribute to operating costs, the service provider has many options available for keeping costs down. Taking advantage of the latest developments in network planning, hardware innovations, and network management will help the service provider keep opex under control while allowing the infrastructure to support the requirements that new services place upon it.

Agile optical networking provides a future-proof network that supports multipurpose and multi-topology networking. It ensures that service providers' operating costs are kept to a minimum through one-time node engineering and zero-touch, automated provisioning. And by enabling rapid service deployment, agile optical networking enables service providers to stay ahead of the ever-changing network curve.


1 Tom Nolle, CIMI Corporation, Netwatcher, October 2005.

Steven D. Robinson has over twenty years of business and technical experience in the telecommunications industry. Prior to Meriton Networks, Steve held various leadership and product development roles with companies such as Agere Systems, Lucent, and AT&T Bell Laboratories. Steve received both his Bachelors and Masters Degrees in Electrical Engineering from Drexel University and his MBA from Lehigh University. He may be reached via the company's Web site at

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