Utility companies are facing two important business challenges. On the one hand, they are constantly looking for ways to improve productivity. For example, power companies want to make electric power transmission and distribution safer, scalable, more reliable, and easy to operate by introducing advanced technologies for power-system protection, automation, control, and monitoring.

On the other hand, utilities are looking for innovative ways to increase revenues by diversifying their business lines. Utility companies that have built extensive, highly reliable transport networks to support their internal communication needs have become aware of the revenue potential in the telecom market by leveraging their networks to carry retail and wholesale applications. As a result, more and more utility companies are becoming competitive telecom carriers (utelcos), leasing wavelength services and bandwidth-on-demand to network operators.

Utilities have several characteristics that drive them to become competitive telecom carriers, including:

• The knowledge, technology and ability required to build, operate and maintain a telecommunication network already exist with the utility.
• The same infrastructure and equipment that support the utility’s operations are required for developing its telecommunication business.
• In recent years, worldwide deregulation has enabled utility companies to provide competitive telecommunication services.

As a result, utility companies are now building next-generation transport networks. However, their current approach is problematic. Currently, Utelcos are deploying multiple, best-of-breed Recon-figurable Optical Add/Drop Multiplexer (WDM/ROADM), Multi-Service Provisioning Platform (MSPP), and L2 Ethernet switch boxes. This results in the achievement of a next-generation network, but one that is relatively hard-to-operate and with higher implementation costs.

A better approach would be to deploy a converged Metro Net-working Solution, integrating Carrier Ethernet with WDM/ROADM technologies and TDM onto a single platform. This is called packet-optical convergence. (See Figure 1.)

 This article covers the issue of NG packet-optical convergence, and its respective benefits that aim to achieve optimal networks.

Main Drivers for Converged Packet-Optics
The traditional, TDM traffic-optimized infrastructure has become inefficient. As a result, it has begun to include built-in packet support to better cope with Ethernet services. This trend began with the MSPP concept (and its ability to map packet data into existing SDH payloads). With a WDM overlay in place, switches and routers can be directly connected to their own wavelength channels and share the same fiber used by TDM signals.

Driver 1: Simplification and Convergence of Protocol
The trend toward optimizing and simplifying layers of protocol continues to bring the packet and optical layers closer together. In the transport layers, The ROADM has fostered the development of the DWDM layer into a viable successor to SONET/SDH as the underlying optical transport technology. Thus, telecom networks consist of fewer layers and technologies. (See Figure 2).

Driver 2: Low Revenue Per Bit in Packet Data Traffic
Although data traffic is constantly growing, the revenues per bit are declining. In order to increase this important statistic, service providers must become as cost-efficient as possible, minimizing operational costs as well as CapEx, and implementing intelligent bandwidth utilization into their optical networks.

Driver 3: Move Toward Dynamic Optical Networking
In order to achieve better response to customer requirements, flexible transport solutions are needed. The optimal method to achieve that is to leverage the benefits of both WDM and Ethernet. The service provider can achieve maximum flexibility by using Multi-degree ROADM that enables mesh-built networks and enables provisioning of new high capacity services, together with carrier-Ethernet capabilities which dynamically allocates and manages the traffic transported on the network.

Network Building Blocks
When choosing the right platform for implementing packet-optics, it’s important to find the optimal building blocks that will provide the carrier with the most cost-effective and simple to manage/provision network. Some of these elements include:

Multi-Degree ROADM
Wavelength-selective switches and reconfigurable optical add-drop multiplexer (WSS) ROADM is currently considered the technology of choice for converged networks worldwide, adding flexibility and lowering total cost-of-ownership for various core and regional network scenarios. WSS ROADMs allow carriers to route any wavelength (or any combination thereof) to any node without the need to predefine traffic demands or install additional devices. This reduces time to market significantly for new services.

Furthermore, the WSS ROADM offers “colorless” ports, enabling the operator increased flexibility in selecting and then re-selecting a specific wavelength to add/drop at the node. This is of particular benefit for a carrier-of-carriers application, with hard to predict traffic and/or if the traffic mix is expected to change often.

The WSS ROADM’s multi-degree architecture means it can be deployed not only in rings and chains as in previous generations but also in the multi-ring and mesh topologies so common in metro core and regional WDM networks.

Converged Packet-Optics Built-In Carrier Ethernet Capabilities
The type of technology a service provider selects to implement Carrier Ethernet has a major influence on the quality of experience (QoE) customers will receive. One such leading technology is multi-protocol label switching (MPLS). MPLS is well suited to be a universal data-carrying mechanism. Label switching works particularly well with IP but is also capable of providing a resilient, connection-oriented path for any network layer protocol. MPLS is an efficient way to move information through packet networks by facilitating traffic engineering and providing QoS prioritization for latency-sensitive applications.

Although its application has been focused on core IP networks, MPLS has been adapted specifically for use in transport networks as “Transport MPLS” and is aligned with the architecture of current circuit-based transport technologies. By matching existing transport operational models, the introduction of transport MPLS is a cost-effective way to ease the migration from legacy to packet networks.

Multi-Technology, Multi-Layered Management System
Advanced management of packet-optical networks takes advantage of the condensed transport layer for provisioning, while presenting operators with tiered multi-technology views (packet, WDM, and SDH) that are familiar and easy to navigate. The shift in function of DWDM from “dumb pipes” to an SDH-like transport layer has created a need for new management tools.

For example, the network management system (NMS) must display in real time available, active, or blocked channels for any route between two points in the network. Tools, such as utilization maps and payload availability charts, allow rapid channel assignment and network utilization management.

The NMS must also include detailed performance monitoring at the wavelength and service level for complete QoS visibility. Accordingly, wavelengths can be used, dropped and shifted, to be picked up and reused as needed with point-and-click convenience. This creates an optical infrastructure that allows rapid provisioning of new connectivity paths for the ever-increasing amount of data traffic. Only this kind of straight-forward management system will allow the carrier to turn up services in minutes.

Optical Transport Network (OTN) Standard
Implementing the OTN standard in the packet-optics infrastructure offers standard formatting and interoperability, protocol and service transparency, and performance enhancements for services, enabling smooth functionality with the packet-based services and protocols.

Benefits of Packet-Optical Convergence
In order to gain a competitive advantage, utilities are making an effort to build their optical networks to be as efficient as possible, while also making sure they are agile enough to respond to any customer need, both internal and external, or to any new revenue-generating opportunity. Convergence is a key to achieving this, with five unique benefits:

1. Service continuity.
2. Improved network efficiency with reduced total cost of ownership.
3. Future-proofing that enables the introduction of new applications.
4. Smooth evolution to next-generation services.
5. Ease of operation.

Simplifying Network Architecture
Utelco network complexity continues to be a challenge, due to the need to support many applications (such as power grid maintenance and control, operational voice, and video surveillance) over multiple networks. Supporting them with a converged network facilitates a simpler solution with reduced cost and complexity, based on the smaller number of network-elements and function integration.

This trend began with the MSPP concept’s ability to map packet data into existing SONET/SDH payloads. With a WDM overlay in place, switches and routers can be directly connected to their own wavelength channels and share the same fiber as TDM signals, bypassing SONET/SDH altogether.

The problem, however, is that switches and routers are data service devices, not necessarily capable of carrier-class transport functions. Traditional WDM originally aimed at simply adding capacity required new capabilities to play the role SONET/SDH used to play as a provisionable transport layer. ROADM technology has been a primary catalyst of this change. The move from static to switched wavelengths has necessitated several improvements in how the analog characteristics of lightwaves are adjusted.

Automatic tuning of parameters such as gain and equalization, and improved performance of components such as dispersion compensation, modulators and receiver sensitivity have ensured proper operation of dynamic WDM. Moreover, development in the digital realm brought advanced OA&M and multi-service provisioning capability to the wavelength level.

Utilities are looking to increase their revenues by diversifying their businesses. They also want to provide better service delivery, administration, and management. In order to meet these goals, a utility’s telecom infrastructure must evolve to support enhanced information management and analysis in the generation, transmission, and distribution grids all the way to the end-customer.

To this end, building a network that converges Ethernet, WDM, and SONET/SDH onto the same platform is a key component of a utility’s success. The value of convergence comes from both integration and the flexibility it gives to utelcos. Major benefits, including simplified management and reduction in service provisioning time and network complexity, complement the more expected cost savings associated with reduced sparing, training, and space requirements.