PDF of this tutorialDefinition
The access network is that portion of a public switched network that connects access nodes to individual subscribers. More simply, it is the last link in a network between the customer premises and the first point of connection to the network infrastructure—a point of presence (PoP) or central office (CO). The access network has hitherto consisted predominantly of passive, twisted-pair copper wires.
The access network has consistently been regarded as a bottleneck in the provisioning of data communication services. This is primarily because the bandwidth available has lagged behind that provided within local-area networks (LANs) and in the upper echelons of the network (in metropolitan and core networks, for example), where concentration factors and economies of scale have allowed optical fiber to unleash significant bandwidth capacity.
The optical access network is that part of the access network implemented using optical fiber. Optical access offers the promise of greatly increased access-network bandwidth by up to several gigabits per second (Gbps)—and most likely more, as technology advances.
This bandwidth availability opens up new architectural possibilities for the provisioning of high-bandwidth services. With the access network as a bandwidth bottleneck, it is necessary to place some sort of processing equipment at the customer premises to manage or control the amount of data transmitted over an access connection. Once the bottleneck is opened, new opportunities present themselves—such as the option of carrying larger quantities of data across an access link to be routed, switched, or processed in some other way at a PoP or CO. In such cases where economies of scale come into play, reducing the cost per bit of handling data, it is possible to simplify the equipment provided at the customer premises.
Overview
There is a general perception that fiber is a scarce resource. However, lack of available fiber for new optical access services is not a major factor in today’s market. In fact, fiber is now a readily available access resource, especially in major urban or metropolitan areas. It is estimated that in 1999 about 65 million kilometers of optical fiber were installed in the United States, of which 70 percent was in the top metropolitan markets of the incumbent local exchange carriers (ILECs) and competitive local exchange carriers (CLECs). The quantity of fiber deployed by CLECs has been forecasted to more than double between 1999 and 2002. All of this points to a large, addressable market for high-speed services based on lighting dark optical fiber—a market with significant growth potential.
Fiber-optic infrastructure is proving to be a vital part of today’s rapidly changing economic environment. The drive for interconnectivity as well as the exponential growth in data traffic as a result of new business applications will lead to the adoption of optical access solutions—as they help both end users and service providers to connect to the information superhighway. A technology is needed that can leverage the existing network as well as increase the economic viability of new network applications. High-bandwidth traffic is creating a mandate to leverage technology and carrier competitiveness to deliver the next wave in high-speed local access. The bandwidth gap can be bridged with optical access solutions. Optical-access platforms provide the solution by unblocking the bandwidth bottleneck between the customer premises unit (CPE) and CO or PoP using dark fiber solutions.
