What is RF Overlay on PON?
RF Overlay on PON, As telcos turn to triple-play services (video, voice and high-speed internet access) to reduce churn and increase revenue, they need to find a way of delivering TV and video to the end-user as cost-effectively as possible.
Each of the major point-to multi point PON variants – BPON, GPON and EPON – offers TV/video service: RF (radio frequency) overlay.In a point-to-multipoint PON architecture, one wavelength frequency is assigned for downstream data and telephony (1490 nm) and another is assigned for upstream data (1310 nm). With the RF overlay approach, through the use of wave-division multiplexing (WDM), a third downstream frequency is assigned – 1550 nm – which is dedicated to video broadcast. RF overlay is capable of delivering all types of video service: analogue broadcast, digital broadcast and HDTV, and video-on-demand.
As TV broadcasting is assigned to a dedicated frequency it will not eat into the data throughput of the PON. It offers a comparatively short entry-to-market time to deliver TV services (no set-top boxes are needed for the delivery of analogue broadcast over coaxial cable in the home).
Through the use RF overlay, operators can gradually migrate to IPTV (by using both delivery systems simultaneously) without the need for external set-top conversion apparatus (assuming they have shipped hybrid IPTV/RF set-top boxes to their customers). This could be an important consideration for operators since IPTV, unlike RF overlay, is not yet a proven technology for delivering video services on a large scale…
The way it works in a fiber network
The RF TV signal is distributed by the 1550nm optical laser transmitter which makes E/O convertering at headend. The RF signal is transported by a separate fiber network to EDFA, or EDFA PON Combiner. This PON WDM combines the RF signal with the data traffic from the OLT, which uses a different wavelength (1310/1490 nm), putting three wavelengths (1550/1310/1490nm) on the same fiber PON and distributing them downstream through the splitters to the customer’s ONT/ONU.