An ultra-high speed OFDMA system for optical access networks

In this paper we present an FPGA based, ultra-high speed OFDMA system which is intended to be used as a bandwidth efficient, advanced modulation format in optical access networks like fiber-to-the-home. The aggregate bandwidth of the network reaches up to 50 GBit/s while handling hundreds of different subscribers, sharing the same optical bandwidth. Compared to other domains using OFDM like e.g. wireless communication, data rates in the multi GBit/s range require very high performance signal processing components at a central office and at the subscribers. With modern FPGA technologies like the Xilinx Virtex-6 family and massive parallelization of the algorithms the necessary processing power can be provided. Besides the OFDMA processing blocks themselves also their connections to a suitable analog front end as well as to data sources and sinks have to be considered. The presented system uses digital-to-analogue (DAC) and analogue-to-digital (ADC) converters with up to 25 GSa/s at the central office and up to 3.125 GSa/s at the subscribers. The connection to data sources and sinks is realized via 10G Ethernet links. The whole system is therefore transparent for Ethernet packets making its integration into existing infrastructure very easy.