Over the last decade, fiber optic cables have been installed by carriers as the backbone of their interoffice networks, becoming the mainstay of the telecommunications infrastructure. Using time division multiplexing (TDM) technology, carriers now routinely transmit information at 2.5 Gb/s on a single fiber, with some deploying equipment that quadruples that rate to 10 Gb/s. The revolution in high bandwidth applications and the explosive growth of the Internet, however, have created capacity demands that exceed traditional TDM limits. As a result, the once seemingly inexhaustible bandwidth promised by the deployment of optical fiber in the 1980s is being exhausted. To meet growing demands for bandwidth, a technology called Dense Wavelength Division Multiplexing (DWDM) has been developed that multiplies the capacity of a single fiber. DWDM systems being deployed today can increase a single fiber’s capacity sixteen fold, to a throughput of 40 Gb/s! This cutting edge technology when combined with network management systems and add-drop multiplexers enables carriers to adopt optically-based transmission networks that will meet the next generation of bandwidth demand at a significantly lower cost than installing new fiber.

To transmit 40 Gb/s over 600 kms using a traditional system would require 16 separate fiber pairs with regenerators placed every 35 kms for a total of 272 regenerators. A 16 channel DWDM system, on the other hand, uses a single fiber pair and 4 amplifiers positioned every 120 kms for a total of 600 kms.

DWDM Ring Networks