Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing Yannis Benlachtar,1,* Philip M. Watts,1,2 Rachid Bouziane,1 Peter Milder,3 Deepak Rangaraj,3 Anthony Cartolano,3 Robert Koutsoyannis,3 James C. Hoe,3 Markus Püschel,3 Madeleine Glick,4 and Robert I. Killey1 1
Optical Networks Group, Department of Electronic and Electrical Engineering, University College London, Torrington Place. London. UK. WC1E 7JE 2 Computer Laboratory, University of Cambridge, JJ Thompson Avenue, Cambridge, CB3 0FD, UK 3 Department of Electrical and Computer Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213, USA 4 Intel Research Pittsburgh, Pittsburgh, PA 15213 USA *
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Abstract: We demonstrate a field programmable gate array (FPGA) based optical orthogonal frequency division multiplexing (OFDM) transmitter implementing real time digital signal processing at a sample rate of 21.4 GS/s. The QPSK-OFDM signal is generated using an 8 bit, 128 point inverse fast Fourier transform (IFFT) core, performing one transform per clock cycle at a clock speed of 167.2 MHz and can be deployed with either a direct-detection or a coherent receiver. The hardware design and the main digital signal processing functions are described, and we show that the main performance limitation is due to the low (4-bit) resolution of the digital-toanalog converter (DAC) and the 8-bit resolution of the IFFT core used. We analyze the back-to-back performance of the transmitter generating an 8.36 Gb/s optical single sideband (SSB) OFDM signal using digital upconversion, suitable for direct-detection. Additionally, we use the device to transmit 8.36 Gb/s SSB OFDM signals over 200 km of uncompensated standard single mode fiber achieving an overall BER
