Replacing FOADMs with Scalability, Agility, Cost-effectiveness
Fixed Optical Add-Drop Multiplexers (FOADMs) were originally developed to improve the delivery of "express" traffic through networks, without requiring expensive OEO regeneration. FOADMs use fixed filters that add/drop a selected wavelength "band" and pass the rest of the wavelengths through the node. Static wavelength-filtering technology eliminates the cost and attenuation to demultiplex all DWDM signals in a signal path. The solution is called FOADM because the wavelength(s) added and dropped are fixed at the time of add/drop filter installation on the optical path through a node. No additional filters can be added without interrupting express wavelengths traveling through the node.
Many FOADM solutions are still in place in carrier networks today and result in tremendous stranded bandwidth. The reasons are simple: (1) the wavelengths that can be added or dropped are pre-determined, and (2) an entire wavelength band has to be dropped rather than just one wavelength at a time. In addition, they are highly static devices, manually-intensive in terms of service provisioning and unscalable, a poor fit for carriers who face high traffic growth and the unpredictability of bandwidth demand in their metro and access networks.
Nistica's FLEDGE series of tunable filter modules offer cost-effective relief from the limitations of FOADMs. Both the FLEDGE 3 and FLEDGE 10 are hitless tunable filters that enable single-wavelength add-drop along the entire C-band spectrum and allow for future 40 Gb/s upgrades. They can also accommodate future add-drop capability for in-line optical amplifiers, and serves as building blocks for multi-wavelength add-drop. A gracefully scalable, agile and cost-effective solution -- now.