75 GBd InP-HBT MUX-DAC module for high-symbol-rate optical transmission

An ultra-broadband 6 bit digital-to-analogue converter (DAC) has been designed and fabricated in InP-HBT technology. The DAC IC includes six 2:1 MUXs and thus operates with a half-rate clock. The DAC module is equipped with 1 mm connectors for its analogue output to ensure broadband characteristics. The measured analogue output bandwidth (BW) is >40 GHz. Four-level pulse amplitude modulation signals with clear eye openings were measured at symbol rates of up to 75 GBd. This MUX-DAC module has the widest BW of any previously reported DACs and is suitable for high-symbol-rate optical transmitters.