Contents Introduction
For some years, the speed of ready DSP has been capable of addressing the equalization requirements long haul transmission at the highest capacities on existing fiber plant. These requirements include a channel memory of order one hundred bits, minmum loop delay of 10's of nanoseconds and a data troughput > 10 Gb/s. Recently we reported transmission of 46 Gb/s over long haul distances using polarization mutiplexed Quadrature Phase shift Key, DP-QPSK, modulation and coherent detection [1],[2]. The transmission is supported by a CMOS receiver ASIC outfitted with four, six bit wide, analog to digital converters, ADCs, and a 20 Mgate DSP engine. The ASIC is shown in Figure1. Each ADC converts signals proportional to the in-phase and quadrature fields arriving on the x and y polarization directions with respect to Rx site reference phase and polarization. These are translated using DSP to the same signal categories but with respect to the transmit side phase and polarization reference. In so doing chromatic dispersion and and PMD are equalized while carrier phase and signal clock are recovered. PDL The total processing amount to 12 Tops/sec and ASIC power dissipation is 21 W. photograph of 46Gb/s receive ASIC
