Radio frequency over glass

In telecommunications, radio frequency over glass (RFoG) is a deep-fiber network design in which the coax portion of the hybrid fiber coax (HFC) network is replaced by a single-fiber passive optical network (PON). Downstream and return-path transmission use different wavelengths to share the same fiber (typically 1550 nm downstream, and 1310 nm or 1590/1610 nm upstream). The return-path wavelength standard is expected to be 1610 nm, but early deployments have used 1590 nm. Using 1590/1610 nm for the return path allows the fiber infrastructure to support both RFoG and a standards-based PON simultaneously, operating with 1490 nm downstream and 1310 nm return-path wavelengths.

RFoG delivers the same services as an RF/DOCSIS/HFC network, with the added benefit of improved noise performance and increased usable RF spectrum in both the downstream and return-path directions. Both RFoG and HFC systems can concurrently operate out of the same headend/hub, making RFoG a good solution for node-splitting and capacity increases on an existing network.

RFoG allows service providers to continue to leverage traditional HFC equipment and back-office applications with the new FTTP deployments. Cable operators can continue to rely on the existing provisioning and billing systems, cable modem termination system (CMTS) platforms, headend equipment, set-top boxes, conditional access technology and cable modems while gaining benefits inherent with RFoG and FTTx.

RFoG provides several benefits over traditional network architecture:

Both cost savings and increased capacity for new services (revenue generating and/or competitive positioning) are driving the acceptance of RFoG as a cost-effective step on the path towards a 100-percent PON-based access network.

As with an HFC architecture, video controllers and data-networking services are fed through a CMTS/edge router. These electrical signals are then converted to optical ones, and transported via a 1550 nm wavelength through a wavelength-division multiplexing (WDM) platform and a passive splitter to a fiber-optic micro-node located at the customer premises. If necessary, an optical amplifier can be used to boost the downstream optical signal to cover a greater distance.

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Wikipedia