Ultra-long haul DWDM for national networks

Summary form only given. Technology has improved, and and so has reduced the cost penalty associated with long systems by allowing longer amplifier spacings. And further, the traffic matrices on national networks have begun to change under the influence of the shift to data traffic. Average connection distances have increased, and a greater concentration of traffic is seen among a smaller number of major nodes. Also, many networks have been built with shorter reach systems, and now as traffic increases, an attractive strategy is to overbuild with express routes, and use the older systems for local traffic and backhaul. These technical, network, and business factors have combined to create the opportunity to apply ultralong haul technology to national networks.