I. Introduction
With advances in transistor technology, the operational speed of digital circuits has increased. The role of a multiplexer (MUX) is to serialize lower speed parallel data to higher speed data, and it is one of the benchmarks used to assess the performance of a digital circuit. Results reported to date for several technologies include 50 Gbit/s for CMOS [1], 108 Gbit/s for SiGe HBT [2], 120 Gbit/s for InP HBT [3], and 100 Gbit/s for InP HEMT [4], [5].