We have published a new collaborative paper on the real-time generation of 85.4 Gb/sec optical OFDM signals using FPGAs, with transmission over 400 km of standard single-mode fiber using a single polarization.
You can read the paper here.
“Generation and Transmission of 85.4 Gb/s Real-time 16QAM Coherent Optical OFDM Signals Over 400 km SSMR with Preamble-less Reception.” Rachid Bouziane, Rene Schmogrow, David Hillerkuss, Peter Milder, Christian Koos, Wolfgang Freude, Juerg Leuthold, Polina Bayvel, and Robert I. Killey. Optics Express, Vol. 20, Issue 19, pp. 21612–21617. 2012.
Abstract: This paper presents a real-time, coherent optical OFDM transmitter based on a field programmable gate array implementation. The transmitter uses 16QAM mapping and runs at 28 GSa/s achieving a data rate of 85.4 Gb/s on a single polarization. A cyclic prefix of 25% of the symbol duration is added enabling dispersion-tolerant transmission over up to 400 km of SSMF. This is the first transmission experiment performed with a real-time OFDM transmitter running at data rates higher than 40 Gb/s. A key aspect of the paper is the introduction of a novel method for OFDM symbol synchronization without relying on training symbols. Unlike conventional preamble-based synchronization methods which perform cross-correlations at regular time intervals and let the system run freely in between, the proposed method performs synchronization in a continuous manner ensuring correct symbol alignment at all times.