Adaptive Background Compensation of Frequency Interleaved DACs With Application to Coherent Optical Transceivers

Digital-to-analog converters (DACs) with bandwidths larger than 70 GHz and sampling rates in excess of 170 GS/s will soon be required ultra-high speed communication applications such as coherent optical transceivers operating at symbol 140 GBd beyond. Frequency interleaving has been proposed a way to break the bandwidth bottleneck applications. Splitting input signal into multiple frequency bands reduces per interleaved DAC therefore it enables synthesis greater signals reconstructed output. Elaborate digital processing (DSP) is seamlessly stitch together sub-bands compensate errors analog path, which would otherwise severely degrade performance system. Adaptive DSP techniques are automatically caused by process, voltage, temperature variations technology (e.g., CMOS, SiGe, etc.) implementations data converters, ensure high manufacturing yield. These must operate background mode avoid interfering normal operation This work introduces an adaptive compensation scheme for DACs (FI-DACs). The primary application example 128 QAM16 transceiver. However, technique applicable other types transceivers, can generalized arbitrary signals, long they stationary or quasi-stationary have wideband continuous spectrum. key elements MIMO equalizer backpropagation algorithm. Numerical simulation results aforementioned show that noise distortion ratio (SNDR) FI-DAC boosted more 25 dB when applied presence typical mismatches. Furthermore, penalty transceiver reduced from 6 0.1 dB.