Experimental demonstration of real-time DSP with FPGA-based optical transmitter

Digital signal processing has the potential to overcome cost and power challenges associated with optical links. The questions to address for short links (avoiding the requirement for temperature control, laser patterning, differential mode delay in multimode fibres, increasing capacity at low cost) are different to those for ultra-long telecom links (mainly chromatic and polarization mode dispersion, and fibre nonlinearity), but both may be solved through the use of DSP. We have completed the construction and begun experimental tests of the first FPGA-based optical transmitter, based on the Xilinx Virtex 4 field programmable gate array chip and D/A converters, operating at 21.4 GSa/s. This will allow DSP for both short optical interconnects and long-haul transmission systems to be experimentally investigated. This paper reviews recent development work on this transmitter and presents initial results.