Special Report: Next Generation Internet Applications
Gwynne claims that 76% of all businesses are within one mile of a service provider optical cable route.[33] Ninety percent of all interoffice trunks use SONET over singlemode fiber.[30] Clearly, if it were only a matter of being close to fiber optic cable routes, then there would be a large number of subscribers using optical cable services. Yet only 3% of all businesses have connection to fiber-based services. Residential connections to fiber-based services are even more rare. The problem lies in the provisioning of services from a fiber optic cable to many subscribers in an economically attractive manner.
In the past, all cable systems terminated in a carrier office and all derived services emanated from the carrier office to the subscriber. Access carriers distribute their services to their subscribers primarily over copper cable which is part of the "outside plant."
Carrier offices depend heavily upon SONET equipment for the provisioning of services. Extending these services to businesses and residences means placing SONET provisioning equipment and installing fiber optic cable in or very near the subscriber's premises. The cost of upgrading the outside plant to use fiber optic cables is very high, typically as high as $30,000 per mile.[34] The cost of placing SONET equipment and upgrading the outside cable plant to fiber optics limits widespread deployment of many high-speed services. High upgrade costs slowed the introduction of services like ISDN and xDSL.
Deployment cost remains a substantial barrier for high-speed access to future all-optical networks. Even so, access carriers continue to invest in fiber optic outside plant. CLECs have 3 million miles of fiber and RBOCs have 14 million miles of fiber installed according to 1998 FCC statistics.[34] Changing market demands are driving future planning of access networks:
.Application Service Providers (ASPs) need better Service-Level Agreements (SLAs) and QoS from their Virtual Private Networks (VPNs).
.Residential customers want broadband access to the Internet.
.Corporate customers want high-speed bandwidth installed and managed by the carrier from the WAN interface at the customer site. Corporations want to add Web phones and personal digital assistants (PDAs) to their networks.
.Cable TV companies are competing for local exchange carrier residential and corporate clients.
.Data traffic exceeded voice traffic on carrier networks during 2000. It continues to grow much faster than voice.
.Copper cables become a less viable service distribution medium as traffic demand continues to grow.
.Changes in the access traffic mix are forcing carriers to change their networks to accommodate increased Internet holding times and to support heavy video content.
A new breed of optical access networks (OANs), called "asynchronous transfer mode passive optical networks" (ATM PONs) or simply "APONs," offers a financially viable way of providing high-speed access to a customer's premises. ATM PONs fall in the class of shared-medium broadcast optical link networks as was generally described by Figure 14. Figure 30 provides a more detailed depiction of an ATM PON. ATM PONs consist of an optical line terminal (OLT) located in the access carrier office and connected by fiber, passive optical splitters, and other passive optical components to several optical network units (ONUs) located on or near the customer homes and offices.[36] ATM PONs are a major innovation for provisioning customer access to high-bandwidth services. Passive optical networks use few active devices in the access loop, which results in lower operating cost and simplified maintenance.[34] PONs provision access bandwidth incrementally from a single T1 (1.544 Mbps) up to OC-12 (622 Mbps).
Previous Next Table
of Content for report: Next Generation Internet Applications Home
