Yannis Benlachtar, Philip M. Watts, Rachid Bouziane, Peter A. Milder, Deepak Rangaraj, Anthony Cartolano, Robert Koutsoyannis, James C. Hoe, Markus Püschel, Madeleine Glick and Robert I. Killey (Optics Express, Vol. 17, No. 20, pp. 17658-17668, 2009)
Generation of Optical OFDM Signals Using 21.4 GS/s Real Time Digital Signal Processing
Published paper (link to publisher)

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-to-analog 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 up-conversion, 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<10^−3.

IP cores for FPGA/ASIC, Discrete/fast Fourier transform, OFDM