8.6 A Highly Reconfigurable 40-97GS/s DAC and ADC with 40GHz AFE Bandwidth and Sub-35fJ/conv-step for 400Gb/s Coherent Optical Applications in 7nm FinFET

Low power digital signal processing (DSP) and optical integration have fueled the development of high-performance optical pluggable modules due to their deployment flexibility and network disaggregation. In addition, the rapid growth of new technologies such as 5G, cloud computing, IoT and AR/VR has prompted the demand for even higher data rates, requiring optical modules to scale beyond 400Gb/s while targeting the best possible tradeoff between power efficiency and reach. This necessitates more complex equalization schemes and coding techniques such as probabilistic shaping (PS) [1] and drives ever higher the specifications of analog building blocks. These requirements, as a result, constantly push the envelope of traditional analog-front-end (AFE) bandwidth and the rates of companion data converters such as DACs and ADCs to the technology limits, making it challenging to address a diversity of DSP modulation needs and oversampling rates while maintaining low power consumption. In this paper, we present an energy efficient optical transceiver fully integrated in a 400G coherent DSP chip using 4 reconfigurable 40-97GS/s 8b DACs and ADCs with a 40GHz AFE bandwidth, fabricated in a 7nm FinFET process.