The Fbrain family of xWDM/xPON solutions includes devices compliant with the ITU-T G.984.5 specification. It redefines optical spectrum bands used in PONs with the GPON protocol. New bands are also provided for implementing new protocols or NGA services by using WDM overlays.

The ITU-T G.984.5 recommendation describes about a dozen example configurations of xWDM (xPON) multiplexers, which covers practically all paths for PON evolution, as considered today.

By installing xPON multiplexers now, telecom operators can make sure that their networks will be ready for seamless transition or upgrade in the future when they decide what evolution path to take or what additional solutions (for example CATV service, OTDR monitoring channel, or implementation of 40G NG-PON2) to add.

In the ITU-T recommendation, xWDM multiplexers are divided into three groups, depending on the services or standards they support. WDM1r multiplexers should be used when adding new-generation services (e.g. HD quality television) is planned in an existing GPON.