Destroy the all-or-nothing myth about migration to fiber.

Expanding network traffic forces new bandwidth delivery solutions.

Network capacity triples every year as data travels across backbone networks originally designed for voice traffic. This dramatic expansion drives providers to seek new solutions to deliver more bandwidth at ever lower rates, in order to remain competitive in this fast-moving market.

The current infrastructure sustaining the last mile of the public network, incapable of supporting these bandwidth demands, needs to be radically overhauled to alleviate this major bottleneck in the metro area. To support customers' mission-critical business applications, today's service providers need cost-effective connectivity solutions that are flexible and scalable, as well as secure and manageable.

Until recently, the first mile of the public network--the point of heaviest bandwidth congestion--had been left to rely on the existing copper infrastructure. Optical fiber solutions are transforming the copper access network into the optical last mile--making the case for eliminating the reliance on copper compelling. Wide deployment in new construction and replacement of older technologies with fiber occurs with greater frequency each year.

Optical fiber carries far more data than copper, the obvious solution for last-mile connectivity between the user and point of presence into the network. By focusing on cost-effective fiber implementations, vendors may well be able to achieve manageable costs for the necessary speed and bandwidth required by enterprises.

Unlike copper, fiber does not radiate. Because it does not carry electricity, fiber is immune to electrical interference. It is lightweight, flexible and easy to handle and install--dropping installation cost premiums are fast approaching those of copper. Also, fiber's life span is longer than that of copper.

Fiber is the preferred medium for applications where security is critical. Copper networks produce radio frequency emissions, which means that someone could tap into sensitive data without even touching the physical infrastructure. Fiber, however, does not radiate and cannot be overheard by a third party. If the signal is wiretapped, light loss is unavoidable and the connection fails.

Fiber supports greater distances than copper. Unshielded twisted pair Category 5 copper cables can be no more than 100 meters in length, due to signal attenuation. Fiber-optic cables, however, can carry signals up to two kilometers over multimode fiber, and up to 100 kilometers over single-mode fiber, before signal degradation becomes a factor. Copper-based Gigabit Ethernet is even more restricted--Category 5 or 5e cable is limited to just 100 meters, while 62.5-micron multimode fiber has a reach of 900 feet--almost three times the distance of copper.

Fiber-optic transmission systems offer higher bandwidth services and high transmitting speeds, as well as a more efficient transmission mode. A fiber-optic cable consumes less than 2% of the size and weight of a copper cable with comparable data transmission capabilities. SONET, for example, utilizes fiber in speed increments of OC-3 (155 Mbps) and OC-12 (622 Mbps). Using dense wave division multiplexing, carriers are transmitting multiple OC-48 (1,000 Mbps) channels for a throughput of up to 100 Gbps on a single fiber strand. As the network infrastructure migrates to Fast Ethernet and SONET, fiber-based transmission systems are becoming the standard.

Existing copper infrastructure does not have to be ripped out and replaced with fiber--a common misconception that keeps too many enterprises from upgrading at all. Intelligent media converters can transparently link existing copper cable to new fiber-optic cable, preserving the investment in existing copper. A media converter can be easily installed almost anywhere in the network, allowing self-paced upgrades.

Increasingly, service providers are deploying fiber-in-the-loop for last-mile connections to businesses with a high density of end-users, since fiber-optic technology is a long-term solution that can provide the bandwidth required for tomorrow's applications. A single optical fiber today can easily carry more than 600 Mbps to individual user sites.

By exponentially increasing the available last-mile bandwidth, the bottleneck can be moved from the LAN-WAN convergence point back to the backbone. Effective bandwidth provisioning and management tools can help by gathering usage and

bandwidth statistics, and enabling network staff to proactively manage data traffic to ensure maximum performance. Secure fiber-optic connections can deliver the speed and bandwidth business customers demand.

Finn is senior product manager at Aura Networks, Nashua, NH.

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