A 50-GHz-bandwidth InP-HBT analog-MUX module for high-symbol-rate optical communications systems

An ultra-broadband 2:1 analog-multiplexer (A-MUX) module has been developed for optical communications systems with a high symbol rate. The A-MUX IC was designed and fabricated using in-house InP HBTs, which have a peak ft and fmax of 290 and 320 GHz, respectively. The A-MUX module has a through bandwidth of over 50 GHz and operates at a clock rate of up to 50 GHz, leading to 100-GS/s operation. Its power consumption is as small as 0.5 W. In addition, we devised a novel method to double the bandwidth of DACs using the A-MUX. We succeeded in generating an 80-Gbaud (160-Gb/s) Nyquist PAM4 signal based on two 20-GHz-bandwidth sub-DACs and this A-MUX.