US Patent 7095958 Fiber access architecture capable of being seamlessly upgraded

Disclosed is an architecture enabling premium services to be provided over fiber to high-end users/customers. The architecture has a plurality of nodes and a passive optical device inserted prior to one of the nodes. The optical device allows wavelengths provisioned for original service(s) to pass through with minimal loss, while other wavelengths provisioned for the premium services are diverted onto a new fiber. This new fiber may be installed at the time of the upgrade, but, sometimes, dark fiber is available. Dark fiber is fiber that carries no optical signals.