SiGe BiCMOS linear modulator drivers with 4.8-Vpp differential output swing for 120-GBaud applications

Two linear, large-swing distributed amplifiers (DAs) are reported for future 120-GBaud fiber-optic systems. The measured differential gain and bandwidth are over 20 dB and 70 GHz, respectively, and the P
_1dB
is -2.5 dBm. Eye diagram measurements with at least 4.8-V
_pp
differential swing were performed for NRZ signals up to a record 120 Gb/s, and with 4-PAM and 8-PAM signals up to 64 GBaud, with the symbol rate limited by the speed and ENOB of the arbitrary waveform generator. As well, a bit error rate better than 10
^-12
is demonstrated at 64 Gb/s.