A high gain-bandwidth product InP HEMT distributed amplifier with 92 GHz cut-off frequency for 40 Gbit/s applications and beyond

The design, fabrication and characteristics of a coplanar distributed ultra broadband amplifier are presented. The circuit is fabricated using a composite channel InP CC-HEMT high breakdown voltage technology developed in Alcatel OPTO+. It exhibits an average gain of 13 dB over a 92 GHz -3dB cut-off frequency that corresponds to a state of the art gain-bandwidth product of 410 GHz for baseband amplifier ICs. It still presents 8 dB gain at 110 GHz. Such an amplifier is a good candidate for 40 and 80 Gbit/s optoelectronic driver modules applications. We discuss the use of coplanar waveguide lines and low impedance bias microstrip transmission lines in such a design. We also highlight the need of largest bandwidths for 40 Gbit/s eye diagram quality and the needed gain-bandwidth product for 80 Gbit/s ETDM communications.